Evaluating the cement stabilization of arsenic-bearing iron wastes from drinking water treatment.

PubMed

Clancy, Tara M; Snyder, Kathryn V; Reddy, Raghav; Lanzirotti, Antonio; Amrose, Susan E; Raskin, Lutgarde; Hayes, Kim F

2015-12-30

Cement stabilization of arsenic-bearing wastes is recommended to limit arsenic release from wastes following disposal. Such stabilization has been demonstrated to reduce the arsenic concentration in the Toxicity Characteristic Leaching Procedure (TCLP), which regulates landfill disposal of arsenic waste. However, few studies have evaluated leaching from actual wastes under conditions similar to ultimate disposal environments. In this study, land disposal in areas where flooding is likely was simulated to test arsenic release from cement stabilized arsenic-bearing iron oxide wastes. After 406 days submersed in chemically simulated rainwater, <0.4% of total arsenic was leached, which was comparable to the amount leached during the TCLP (<0.3%). Short-term (18 h) modified TCLP tests (pH 3-12) found that cement stabilization lowered arsenic leaching at high pH, but increased leaching at pH<4.2 compared to non-stabilized wastes. Presenting the first characterization of cement stabilized waste using μXRF, these results revealed the majority of arsenic in cement stabilized waste remained associated with iron. This distribution of arsenic differed from previous observations of calcium-arsenic solid phases when arsenic salts were stabilized with cement, illustrating that the initial waste form influences the stabilized form. Overall, cement stabilization is effective for arsenic-bearing wastes when acidic conditions can be avoided. Copyright © 2015 Elsevier B.V. All rights reserved.

Role of individual histidines in the pH-dependent global stability of human chloride intracellular channel 1.

PubMed

Achilonu, Ikechukwu; Fanucchi, Sylvia; Cross, Megan; Fernandes, Manuel; Dirr, Heini W

2012-02-07

Chloride intracellular channel proteins exist in both a soluble cytosolic form and a membrane-bound form. The mechanism of conversion between the two forms is not properly understood, although one of the contributing factors is believed to be the variation in pH between the cytosol (~7.4) and the membrane (~5.5). We systematically mutated each of the three histidine residues in CLIC1 to an alanine at position 74 and a phenylalanine at positions 185 and 207. We examined the effect of the histidine-mediated pH dependence on the structure and global stability of CLIC1. None of the mutations were found to alter the global structure of the protein. However, the stability of H74A-CLIC1 and H185F-CLIC1, as calculated from the equilibrium unfolding data, is no longer dependent on pH because similar trends are observed at pH 7.0 and 5.5. The crystal structures show that the mutations result in changes in the local hydrogen bond coordination. Because the mutant total free energy change upon unfolding is not different from that of the wild type at pH 7.0, despite the presence of intermediates that are not seen in the wild type, we propose that it may be the stability of the intermediate state rather than the native state that is dependent on pH. On the basis of the lower stability of the intermediate in the H74A and H185F mutants compared to that of the wild type, we conclude that both His74 and His185 are involved in triggering the pH changes to the conformational stability of wild-type CLIC1 via their protonation, which stabilizes the intermediate state.

The stability of amoxicillin trihydrate and potassium clavulanate combination in aqueous solutions.

PubMed

Jerzsele, Akos; Nagy, Gábor

2009-12-01

The effect of various environmental factors on the stability of aqueous solutions of amoxicillin-clavulanic acid combination in a veterinary water-soluble powder product was investigated. In the swine industry, the combination is administered via the drinking water, where both substances are quickly decomposed depending on several environmental factors. The degradation rate of the substances was determined in solutions of different water hardness levels (German hardness of 2, 6 and 10) and pH values (3.0, 7.0 and 10.0), and in troughs made of different materials (metal or plastic). Increasing the water hardness decreased the stability of both substances, amoxicillin being more stable at each hardness value than clavulanate. Amoxicillin trihydrate proved to be most stable at an acidic pH, while increasing the pH decreased its stability (P < 0.05). Maximum stability of potassium clavulanate was experienced at neutral pH, while its decomposition rate was significantly higher at acidic and alkaline pH values (P < 0.01). The stability of the amoxicillin-clavulanic acid combination depends mainly on the less stable clavulanate, although the effect of metallic ions significantly increased the decomposition rate of amoxicillin, rendering it less stable in metal troughs than clavulanate (P < 0.05). Therefore, the amoxicillin-clavulanic acid combination should be administered to the animals in soft water, at neutral pH and in plastic troughs.

Physical stability comparisons of IgG1-Fc variants: effects of N-glycosylation site occupancy and Asp/Gln residues at site Asn 297

PubMed Central

KIM, JAE HYUN; JOSHI, SANGEETA B.; MIDDAUGH, C. RUSSELL; TOLBERT, THOMAS J.; VOLKIN, DAVID B.

2014-01-01

The structural integrity and conformational stability of various IgG1-Fc proteins produced from the yeast Pichia pastoris with different glycosylation site occupancy (di-, mono-, and non- glycosylated) was determined. In addition, the physical stability profiles of three different forms of non-glycosylated Fc molecules (varying amino acid residues at site 297 in the CH2 domain due to point mutations and enzymatic digestion of the Fc glycoforms) were also examined. The physical stability of these IgG1-Fc glycoproteins was examined as a function of pH and temperature by high throughput biophysical analysis using multiple techniques combined with data visualization tools (three index empirical phase diagrams and radar charts). Across the pH range of 4.0 to 6.0, the di- and mono- glycosylated forms of the IgG1-Fc showed the highest and lowest levels of physical stability respectively, with the non-glycosylated forms showing intermediate stability depending on solution pH. In the aglycosylated Fc proteins, the introduction of Asp (D) residues at site 297 (QQ vs. DN vs. DD forms) resulted in more subtle changes in structural integrity and physical stability depending on solution pH. The utility of evaluating the conformational stability profile differences between the various IgG1-Fc glycoproteins is discussed in the context of analytical comparability studies. PMID:24740840

Stability enhancement of cytochrome c through heme deprotonation and mutations.

PubMed

Sonoyama, Takafumi; Hasegawa, Jun; Uchiyama, Susumu; Nakamura, Shota; Kobayashi, Yuji; Sambongi, Yoshihiro

2009-01-01

The chemical denaturation of Pseudomonas aeruginosa cytochrome c(551) variants was examined at pH 5.0 and 3.6. All variants were stabilized at both pHs compared with the wild-type. Remarkably, the variants carrying the F34Y and/or E43Y mutations were more stabilized than those having the F7A/V13M or V78I ones at pH 5.0 compared with at pH 3.6 by ~3.0-4.6 kJ/mol. Structural analyses predicted that the side chains of introduced Tyr-34 and Tyr-43 become hydrogen donors for the hydrogen bond formation with heme 17-propionate at pH 5.0, but less efficiently at pH 3.6, because the propionate is deprotonated at the higher pH. Our results provide an insight into a stabilization strategy for heme proteins involving variation of the heme electronic state and introduction of appropriate mutations.

Impact of lysozyme on stability mechanism of nanozirconia aqueous suspension

NASA Astrophysics Data System (ADS)

Szewczuk-Karpisz, Katarzyna; Wiśniewska, Małgorzata

2016-08-01

The effect of lysozyme (LSZ) presence on the zirconium(IV) oxide (ZrO2) aqueous suspension stability was examined. The applied zirconia contains mesopores (with a diameter about 30 nm) and its mean particle size is about 100 nm. To determine the stability mechanism of ZrO2 suspension in the biopolymer presence, the adsorption and electrokinetic (surface charge density and zeta potential) measurements were performed in the pH range 3-10. The lysozyme adsorption on the nanozirconia surface proceeds mainly through electrostatic forces. Under solid-polymer repulsion conditions, there is no adsorption of lysozyme (pH < 6, CNaCl 0.01 mol/dm3). The increase of solution ionic strength to 0.2 mol/dm3 causes screening of unfavourable forces and biopolymer adsorption becomes possible. The LSZ addition to the ZrO2 suspension influences its stability. At pH 3, 4.6 and 7.6, slight improvement of the system stability was obtained. In turn, at pH 9 considerable destabilization of nanozirconia particles covered by polymeric layers occurs.

Synthesis and Characterisation of Biocompatible Polymer-Conjugated Magnetic Beads for Enhancement Stability of Urease.

PubMed

Doğaç, Yasemin Ispirli; Teke, Mustafa

2016-04-01

We reported natural polymer-conjugated magnetic featured urease systems for removal of urea effectively. The optimum temperature (20-60 °C), optimum pH (3.0-10.0), kinetic parameters, thermal stability (4-70 °C), pH stability (4.0-9.0), operational stability (0-250 min), reusability (18 times) and storage stability (24 weeks) were studied for characterisation of the urease-encapsulated biocompatible polymer-conjugated magnetic beads. Also, the surface groups and chemical structure of the magnetic beads were determined by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The all urease-encapsulated magnetic beads protected their stability of 30-45 % relative activity at 70 °C. A significant increase was observed at their pH stability compared with the free urease for both acidic and alkaline medium. Besides this, their repeatability activity were approximately 100 % during 4(th) run. They showed residual activity of 50 % after 16 weeks. The importance of this work is enhancement stability of immobilised urease by biocompatible polymer-conjugated magnetic beads for the industrial application based on removal of urea.

Application of extrinsic fluorescence spectroscopy for the high throughput formulation screening of aluminum-adjuvanted vaccines.

PubMed

Ausar, Salvador F; Chan, Judy; Hoque, Warda; James, Olive; Jayasundara, Kavisha; Harper, Kevin

2011-02-01

High throughput screening (HTS) of excipients for proteins in solution can be achieved by several analytical techniques. The screening of stabilizers for proteins adsorbed onto adjuvants, however, may be difficult due to the limited amount of techniques that can measure stability of adsorbed protein in high throughput mode. Here, we demonstrate that extrinsic fluorescence spectroscopy can be successfully applied to study the physical stability of adsorbed antigens at low concentrations in 96-well plates, using a real-time polymerase chain reaction (RT-PCR) instrument. HTS was performed on three adjuvanted pneumococcal proteins as model antigens in the presence of a standard library of stabilizers. Aluminum hydroxide appeared to decrease the stability of all three proteins at relatively high and low pH values, showing a bell-shaped curve as the pH was increased from 5 to 9 with a maximum stability at near neutral pH. Nonspecific stabilizers such as mono- and disaccharides could increase the conformational stability of the antigens. In addition, those excipients that increased the melting temperature of adsorbed antigens could improve antigenicity and chemical stability. To the best of our knowledge, this is the first report describing an HTS technology amenable for low concentration of antigens adsorbed onto aluminum-containing adjuvants. Copyright © 2010 Wiley-Liss, Inc.

Effect of acidification on carrot (Daucus carota) juice cloud stability.

PubMed

Schultz, Alison K; Barrett, Diane M; Dungan, Stephanie R

2014-11-26

Effects of acidity on cloud stability in pasteurized carrot juice were examined over the pH range of 3.5-6.2. Cloud sedimentation, particle diameter, and ζ potential were measured at each pH condition to quantify juice cloud stability and clarification during 3 days of storage. Acidification below pH 4.9 resulted in a less negative ζ potential, an increased particle size, and an unstable cloud, leading to juice clarification. As the acidity increased, clarification occurred more rapidly and to a greater extent. Only a weak effect of ionic strength was observed when sodium salts were added to the juice, but the addition of calcium salts significantly reduced the cloud stability.

Improving the storage stability of Bifidobacterium breve in low pH fruit juice.

PubMed

Saarela, M; Alakomi, H L; Mättö, J; Ahonen, A M; Puhakka, A; Tynkkynen, S

2011-09-01

Bifidobacterial food applications are limited since bifidobacteria are sensitive to e.g. acidic conditions prevalent in many food matrices. The aim of the present study was to investigate whether a low pH selection step alone or combined to UV mutagenesis could improve the viability of an acid sensitive Bifidobacterium strain, B. breve 99, in low pH food matrices. Furthermore, the potential of carriers and an oat fibre preparation to further improve the stability was studied. The best performing low pH tolerant variants in the present study were generated by UV-mutagenesis with 70-700μJ/cm(2) followed by incubation in growth medium at pH 4.5. The most promising variants regarding the low pH tolerance showed, in repeated tests with cells grown without pH control, about one Log-value better survival in pH 3.8 fruit juice after one week storage at 4°C compared to wild-type B. breve 99. Cells grown with pH control, PDX formulated and then frozen showed poorer viability in low pH fruit juice than cells grown with no pH control. For frozen concentrates pH 3.8 was too stressful and no or small differences between the variants and the wild-type strain were seen. The differences detected at pH 3.8 with the cells grown without pH control were also seen with the frozen concentrates at pH 4.5. Some improvement in the stability could be achieved by using a combination of trehalose, vitamin C and PDX as a freezing carrier material, whereas a significant improvement in the stability was seen when oat fibre was added into the fruit juice together with the frozen cells. Due to the initial very poor fruit juice tolerance of B. breve 99 the obtained improvement in the stability was not enough for commercial applications. However, the same methods could be applied to initially better performing strains to further improve their stability in the fruit juice. Copyright © 2010 Elsevier B.V. All rights reserved.

Engineering a highly active thermophilic β-glucosidase to enhance its pH stability and saccharification performance.

PubMed

Xia, Wei; Xu, Xinxin; Qian, Lichun; Shi, Pengjun; Bai, Yingguo; Luo, Huiying; Ma, Rui; Yao, Bin

2016-01-01

β-Glucosidase is an important member of the biomass-degrading enzyme system, and plays vital roles in enzymatic saccharification for biofuels production. Candidates with high activity and great stability over high temperature and varied pHs are always preferred in industrial practice. To achieve cost-effective biomass conversion, exploring natural enzymes, developing high level expression systems and engineering superior mutants are effective approaches commonly used. A newly identified β-glucosidase of GH3, Bgl3A, from Talaromyces leycettanus JCM12802, was overexpressed in yeast strain Pichia pastoris GS115, yielding a crude enzyme activity of 6000 U/ml in a 3 L fermentation tank. The purified enzyme exhibited outstanding enzymatic properties, including favorable temperature and pH optima (75 °C and pH 4.5), good thermostability (maintaining stable at 60 °C), and high catalytic performance (with a specific activity and catalytic efficiency of 905 U/mg and 9096/s/mM on pNPG, respectively). However, the narrow stability of Bgl3A at pH 4.0-5.0 would limit its industrial applications. Further site-directed mutagenesis indicated the role of excessive O-glycosylation in pH liability. By removing the potential O-glycosylation sites, two mutants showed improved pH stability over a broader pH range (3.0-10.0). Besides, with better stability under pH 5.0 and 50 °C compared with wild type Bgl3A, saccharification efficiency of mutant M1 was improved substantially cooperating with cellulase Celluclast 1.5L. And mutant M1 reached approximately equivalent saccharification performance to commercial β-glucosidase Novozyme 188 with identical β-glucosidase activity, suggesting its great prospect in biofuels production. In this study, we overexpressed a novel β-glucosidase Bgl3A with high specific activity and high catalytic efficiency in P. pastoris. We further proved the negative effect of excessive O-glycosylation on the pH stability of Bgl3A, and enhanced the pH stability by reducing the O-glycosylation. And the enhanced mutants showed much better application prospect with substantially improved saccharification efficiency on cellulosic materials.

Optimization of Processing Parameters for Extraction of Amylase Enzyme from Dragon (Hylocereus polyrhizus) Peel Using Response Surface Methodology

PubMed Central

Abdul Manap, Mohd Yazid; Zohdi, Norkhanani

2014-01-01

The main goal of this study was to investigate the effect of extraction conditions on the enzymatic properties of thermoacidic amylase enzyme derived from dragon peel. The studied extraction variables were the buffer-to-sample (B/S) ratio (1 : 2 to 1 : 6, w/w), temperature (−18°C to 25°), mixing time (60 to 180 seconds), and the pH of the buffer (2.0 to 8.0). The results indicate that the enzyme extraction conditions exhibited the least significant (P < 0.05) effect on temperature stability. Conversely, the extraction conditions had the most significant (P < 0.05) effect on the specific activity and pH stability. The results also reveal that the main effect of the B/S ratio, followed by its interaction with the pH of the buffer, was significant (P < 0.05) among most of the response variables studied. The optimum extraction condition caused the amylase to achieve high enzyme activity (648.4 U), specific activity (14.2 U/mg), temperature stability (88.4%), pH stability (85.2%), surfactant agent stability (87.2%), and storage stability (90.3%). PMID:25050403

Temperature- and pH-dependent effect of lactate on in vitro redox stability of red meat myoglobins.

PubMed

Nair, M N; Suman, S P; Li, S; Ramanathan, R; Mancini, R A

2014-01-01

Our objective was to evaluate the influence of lactate on in vitro redox stability and thermostability of beef, horse, pork, and sheep myoglobins. Lactate (200 mM) had no effect (P>0.05) on redox stability at physiological (pH7.4, 37°C) and meat (pH 5.6, 4°C) conditions. However, lactate increased (P<0.05) metmyoglobin formation at a condition simulating stressed live skeletal muscle (pH 6.5, 37°C). The redox stability of myoglobins at stressed live skeletal muscle and meat conditions was species-specific (P<0.05). Myoglobin thermostability at 71°C was lower (P<0.05) in the presence of lactate compared with controls and was influenced (P<0.05) by species. The results of the present study indicate that the effects of lactate on myoglobin are temperature and pH dependent. The observed lack of influence of lactate on myoglobin redox stability at meat condition suggests that the color stability of lactate-enhanced fresh meat is not due to direct interactions between the ingredient and the heme protein. © 2013.

Stability of urea in solution and pharmaceutical preparations.

PubMed

Panyachariwat, Nattakan; Steckel, Hartwig

2014-01-01

The stability of urea in solution and pharmaceutical preparations was analyzed as a function of temperature (25°-60°C), pH (3.11-9.67), and initial urea concentration (2.5%-20%). This study was undertaken to (i) obtain more extensive, quantitative information relative to the degradation of urea in both aqueous and non-aqueous solutions and in pharmaceutical preparations, and (ii) test the effects of initial urea concentration, pH, buffer, and temperature values on urea degradation. The stability analysis shows that urea is more stable at the pH range of 4-8 and the stability of urea decreases by increase in temperature for all pH values. Within the experimental range of temperature and initial urea concentration values, the lowest urea degradation was found with lactate buffer pH 6.0. The urea decomposition rate in solution and pharmaceutical preparations shows the dependence of the initial urea concentrations. At higher initial urea concentrations, the rate of degradation is a decreasing function with time. This suggests that the reverse reaction is a factor in the degradation of concentrated urea solution. For non-aqueous solvents, isopropanol showed the best effort in retarding the decomposition of urea. Since the losses in urea is directly influenced by its stability at a given temperature and pH, the stability analysis of urea by the proposed model can be used to prevent the loss and optimize the operating condition for urea-containing pharmaceutical preparations.

Physical stability comparisons of IgG1-Fc variants: effects of N-glycosylation site occupancy and Asp/Gln residues at site Asn 297.

PubMed

Alsenaidy, Mohammad A; Okbazghi, Solomon Z; Kim, Jae Hyun; Joshi, Sangeeta B; Middaugh, C Russell; Tolbert, Thomas J; Volkin, David B

2014-06-01

The structural integrity and conformational stability of various IgG1-Fc proteins produced from the yeast Pichia pastoris with different glycosylation site occupancy (di-, mono-, and nonglycosylated) were determined. In addition, the physical stability profiles of three different forms of nonglycosylated Fc molecules (varying amino-acid residues at site 297 in the CH 2 domain due to the point mutations and enzymatic digestion of the Fc glycoforms) were also examined. The physical stability of these IgG1-Fc glycoproteins was examined as a function of pH and temperature by high-throughput biophysical analysis using multiple techniques combined with data visualization tools (three index empirical phase diagrams and radar charts). Across the pH range of 4.0-6.0, the di- and monoglycosylated forms of the IgG1-Fc showed the highest and lowest levels of physical stability, respectively, with the nonglycosylated forms showing intermediate stability depending on solution pH. In the aglycosylated Fc proteins, the introduction of Asp (D) residues at site 297 (QQ vs. DN vs. DD forms) resulted in more subtle changes in structural integrity and physical stability depending on solution pH. The utility of evaluating the conformational stability profile differences between the various IgG1-Fc glycoproteins is discussed in the context of analytical comparability studies. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Biophysical characterization and conformational stability of Ebola and Marburg virus-like particles.

PubMed

Hu, Lei; Trefethen, Jared M; Zeng, Yuhong; Yee, Luisa; Ohtake, Satoshi; Lechuga-Ballesteros, David; Warfield, Kelly L; Aman, M Javad; Shulenin, Sergey; Unfer, Robert; Enterlein, Sven G; Truong-Le, Vu; Volkin, David B; Joshi, Sangeeta B; Middaugh, C Russell

2011-12-01

The filoviruses, Ebola virus and Marburg virus, cause severe hemorrhagic fever with up to 90% human mortality. Virus-like particles of EBOV (eVLPs) and MARV (mVLPs) are attractive vaccine candidates. For the development of stable vaccines, the conformational stability of these two enveloped VLPs produced in insect cells was characterized by various spectroscopic techniques over a wide pH and temperature range. Temperature-induced aggregation of the VLPs at various pH values was monitored by light scattering. Temperature/pH empirical phase diagrams (EPDs) of the two VLPs were constructed to summarize the large volume of data generated. The EPDs show that both VLPs lose their conformational integrity above about 50°C-60°C, depending on solution pH. The VLPs were maximally thermal stable in solution at pH 7-8, with a significant reduction in stability at pH 5 and 6. They were much less stable in solution at pH 3-4 due to increased susceptibility of the VLPs to aggregation. The characterization data and conformational stability profiles from these studies provide a basis for selection of optimized solution conditions for further vaccine formulation and long-term stability studies of eVLPs and mVLPs. Copyright © 2011 Wiley-Liss, Inc.

Chemical reaction mechanisms between Y2O3 stabilized ZrO2 and Gd doped CeO2 with PH3 in coal syngas

NASA Astrophysics Data System (ADS)

Chen, Gang; Kishimoto, Haruo; Yamaji, Katsuhiko; Kuramoto, Koji; Gong, Mingyang; Liu, Xingbo; Hackett, Gregory; Gerdes, Kirk; Horita, Teruhisa

2014-12-01

To clarify the chemical stability of the key materials exposed to coal syngas (CSG) containing PH3 contaminant atmosphere, exposure tests of Y2O3 8 mol.% stabilized ZrO2 (YSZ) and Gd doped CeO2 (GDC) are carried out in simulated CSG with different concentrations of PH3. Significant reaction between YSZ and 10 ppm PH3 in CSG atmosphere is confirmed, and no obvious reaction is detected on the surface of YSZ after exposed in CSG with 1 ppm PH3. YPO4, Zr2.25(PO4)3 and monoclinic Y partial stabilized ZrO2 (m-PSZ) are identified on the YSZ pellet surface after exposed in CSG with 10 ppm PH3. GDC reacted with PH3 even at 1 ppm concentration. A (Ce0.9Gd0.1)PO4 layer is formed on the surface of GDC pellet after exposure in CSG with 10 ppm PH3. Possible reaction mechanisms between YSZ and GDC with PH3 in CSG are clarified. Compared with GDC, YSZ exhibits sufficient phosphorus resistance for devices directly exposed to a coal syngas atmosphere containing low concentration of PH3.

Evaluating the effects of buffer conditions and extremolytes on thermostability of granulocyte colony-stimulating factor using high-throughput screening combined with design of experiments.

PubMed

Ablinger, Elisabeth; Hellweger, Monika; Leitgeb, Stefan; Zimmer, Andreas

2012-10-15

In this study, we combined a high-throughput screening method, differential scanning fluorimetry (DSF), with design of experiments (DoE) methodology to evaluate the effects of several formulation components on the thermostability of granulocyte colony stimulating factor (G-CSF). First we performed a primary buffer screening where we tested thermal stability of G-CSF in different buffers, pH values and buffer concentrations. The significance of each factor and the two-way interactions between them were studied by multivariable regression analysis. pH was identified as most critical factor regarding thermal stability. The most stabilizing buffer, sodium glutamate, and sodium acetate were determined for further investigations. Second we tested the effect of 6 naturally occurring extremolytes (trehalose, sucrose, ectoine, hydroxyectoine, sorbitol, mannitol) on the thermal stability of G-CSF, using a central composite circumscribed design. At low pH (3.8) and low buffer concentration (5 mM) all extremolytes led to a significant increase in thermal stability except the addition of ectoine which resulted in a strong destabilization of G-CSF. Increasing pH and buffer concentration led to an increase in thermal stability with all investigated extremolytes. The described systematic approach allowed to create a ranking of stabilizing extremolytes at different buffer conditions. Copyright © 2012. Published by Elsevier B.V.

A Systematic Approach Toward Stabilization of CagL, a Protein Antigen from Helicobacter pylori That Is a Candidate Subunit Vaccine

PubMed Central

Choudhari, Shyamal P.; Pendleton, Kirk P.; Ramsey, Joshua D.; Blanchard, Thomas G.; Picking, William D.

2013-01-01

An important consideration in the development of subunit vaccines is loss of activity caused by physical instability of the protein. Such instability often results from suboptimal solution conditions related to pH and temperature. Excipients can help to stabilize vaccines, but it is important to screen and identify excipients that adequately contribute to stabilization of a given formulation. CagL is a protein present in strains of Helicobacter pylori that possess type IV secretion systems. It contributes to bacterial adherence via α5β1 integrin, thereby making it an attractive subunit vaccine candidate. We characterized the stability of CagL in different pH and temperature conditions using a variety of spectroscopic techniques. Stability was assessed in terms of transition temperature (Tm) with the accumulated data then incorporated into an empirical phase diagram (EPD) that provided an overview of CagL physical stability. These analyses indicated maximum CagL stability at pH 4–6 up to 40 °C in the absence of excipient. Using this EPD analysis, aggregation assays were developed to screen a panel of excipients with some found to inhibit CagL aggregation. Candidate stabilizers were selected to confirm their enhanced stabilizing effect. These analyses will help in the formulation of a stable vaccine against H. pylori. PMID:23794457

Examination of molecular mechanism for the enhanced thermal stability of anthocyanins by metal cations and polysaccharides.

PubMed

Tachibana, Noriko; Kimura, Yukihiro; Ohno, Takashi

2014-01-15

Anthocyanins exhibit colour variation over wide pH range but the colour stability is relatively low at the physiological pH. To improve the stability of anthocyanins in neutral to weakly acidic pH region, effects of metal cations and polysaccharides on the colour stability of cyanidin-3-glucoside (C3G) were examined by ultraviolet-visible and resonance Raman spectroscopies. C3G was thermally stabilized by the addition of Fe(3+) but formed aggregation. However, further addition of anionic polysaccharides enhanced the thermal stability of C3G without aggregation. Similar stabilisation was confirmed for delphinidin-3-glucoside (D3G) but not for pelargonidin-3-glucoside. The stability of anthocyanins considerably varied depending on pHs and kinds of metal cations, polysaccharides and buffer molecules. The characteristic resonance Raman bands of C3G-Fe(3+) and D3G-Fe(3+) complexes were significantly affected by the addition of alginate, (18)O/(16)O-isotope substitution, and Fe(2+)/Fe(3+)-replacement. These results suggest that alginate associates with C3G through Fe(3+) to form a stable complex, which enhances the thermal stability of C3G. Copyright © 2013 Elsevier Ltd. All rights reserved.

Solubility of lead and copper in biochar-amended small arms range soils: influence of soil organic carbon and pH.

PubMed

Uchimiya, Minori; Bannon, Desmond I

2013-08-14

Biochar is often considered a strong heavy metal stabilizing agent. However, biochar in some cases had no effects on, or increased the soluble concentrations of, heavy metals in soil. The objective of this study was to determine the factors causing some biochars to stabilize and others to dissolve heavy metals in soil. Seven small arms range soils with known total organic carbon (TOC), cation exchange capacity, pH, and total Pb and Cu contents were first screened for soluble Pb and Cu concentrations. Over 2 weeks successive equilibrations using weak acid (pH 4.5 sulfuric acid) and acetate buffer (0.1 M at pH 4.9), Alaska soil containing disproportionately high (31.6%) TOC had nearly 100% residual (insoluble) Pb and Cu. This soil was then compared with sandy soils from Maryland containing significantly lower (0.5-2.0%) TOC in the presence of 10 wt % (i) plant biochar activated to increase the surface-bound carboxyl and phosphate ligands (PS450A), (ii) manure biochar enriched with soluble P (BL700), and (iii) unactivated plant biochars produced at 350 °C (CH350) and 700 °C (CH500) and by flash carbonization (corn). In weak acid, the pH was set by soil and biochar, and the biochars increasingly stabilized Pb with repeated extractions. In pH 4.9 acetate buffer, PS450A and BL700 stabilized Pb, and only PS450A stabilized Cu. Surface ligands of PS450A likely complexed and stabilized Pb and Cu even under acidic pH in the presence of competing acetate ligand. Oppositely, unactivated plant biochars (CH350, CH500, and corn) mobilized Pb and Cu in sandy soils; the putative mechanism is the formation of soluble complexes with biochar-borne dissolved organic carbon. In summary, unactivated plant biochars can inadvertently increase dissolved Pb and Cu concentrations of sandy, low TOC soils when used to stabilize other contaminants.

Nature of the Charged-Group Effect on the Stability of the C-Peptide Helix

NASA Astrophysics Data System (ADS)

Shoemaker, Kevin R.; Kim, Peter S.; Brems, David N.; Marqusee, Susan; York, Eunice J.; Chaiken, Irwin M.; Stewart, John M.; Baldwin, Robert L.

1985-04-01

The residues responsible for the pH-dependent stability of the helix formed by the isolated C-peptide (residues 1-13 of ribonuclease A) have been identified by chemical synthesis of analogues and measurement of their helix-forming properties. Each of the residues ionizing between pH 2 and pH 8 has been replaced separately by an uncharged residue. Protonation of Glu-2- is responsible for the sharp decrease in helix stability between pH 5 and pH 2, and deprotonation of His-12+ causes a similar decrease between pH 5 and pH 8. Glu-9- is not needed for helix stability. The results cannot be explained by the Zimm-Bragg model and host-guest data for α -helix formation, which predict that the stability of the C-peptide helix should increase when Glu-2- is protonated or when His-12+ is deprotonated. Moreover, histidine+ is a strong helix-breaker in host-guest studies. In proteins, acidic and basic residues tend to occur at opposite ends of α -helices: acidic residues occur preferentially near the NH2-terminal end and basic residues near the COOH-terminal end. A possible explanation, based on a helix dipole model, has been given [Blagdon, D. E. & Goodman, M. (1975) Biopolymers 14, 241-245]. Our results are consistent with the helix dipole model and they support the suggestion that the distribution of charged residues in protein helices reflects the helix-stabilizing propensity of those residues. Because Glu-9 is not needed for helix stability, a possible Glu-9-\\cdots His-12+ salt bridge does not contribute significantly to helix stability. The role of a possible Glu-2-\\cdots Arg-10+ salt bridge has not yet been evaluated. A charged-group effect on α -helix stability in water has also been observed in a different peptide system [Ihara, S., Ooi, T. & Takahashi, S. (1982) Biopolymers 21, 131-145]: block copolymers containing (Ala)20 and (Glu)20 show partial helix formation at low temperatures, pH 7.5, where the glutamic acid residues are ionized. (Glu)20(Ala)20Phe forms a helix that is markedly more stable than (Ala)20(Glu)20Phe. The results are consistent with a helix dipole model.

Stability and in vitro digestibility of emulsions containing lecithin and whey proteins.

PubMed

Mantovani, Raphaela Araujo; Cavallieri, Ângelo Luiz Fazani; Netto, Flavia Maria; Cunha, Rosiane Lopes

2013-09-01

The effect of pH and high-pressure homogenization on the properties of oil-in-water (O/W) emulsions stabilized by lecithin and/or whey proteins (WPI) was evaluated. For this purpose, emulsions were characterized by visual analysis, droplet size distribution, zeta potential, electrophoresis, rheological measurements and their response to in vitro digestion. Lecithin emulsions were stable even after 7 days of storage and WPI emulsions were unstable only at pH values close to the isoelectric point (pI) of proteins. Systems containing the mixture of lecithin and WPI showed high kinetic instability at pH 3, which was attributed to the electrostatic interaction between the emulsifiers oppositely charged at this pH value. At pH 5.5 and 7, the mixture led to reduction of the droplet size with enhanced emulsion stability compared to the systems with WPI or lecithin. The stability of WPI emulsions after the addition of lecithin, especially at pH 5.5, was associated with the increase of droplet surface charge density. The in vitro digestion evaluation showed that WPI emulsion was more stable against gastrointestinal conditions.

Effect of the presence of cationic polyacrylamide on the surface properties of aqueous alumina suspension-stability mechanism

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

2014-11-01

The effects of solution pH and the content of cationic groups in polyacrylamide (PAM) macromolecules on the stability mechanism of aqueous alumina suspension were investigated. The following experimental techniques were applied: spectrophotometry, potentiometric titration, microelectrophoresis, viscosimetry and turbidimetry. They enable determination of polymer adsorbed amount, surface charge density and zeta potential of solid particles in the presence and absence of PAM, as well as thickness of polymer adsorption layer, size of macromolecules in the solution and stability of the Al2O3-polymer systems, respectively. The obtained results indicate that adsorption of PAM increases with the increasing pH, whereas the thickness of polymeric adsorption layer decreases. Additionally, the greater the number of cationic groups in the PAM chains is, the higher adsorption was found. The polymer presence influences on the alumina suspension stability. At pH 3 and 6 the slight deterioration of stability conditions of solid particle covered with polyacrylamide was observed. At pH 9 the systems containing polymer are unstable, similarly to the suspension without PAM, but the mechanism of their destabilization is different.

pH-dependent relationship between thermodynamic and kinetic stability in the denaturation of human phosphoglycerate kinase 1.

PubMed

Pey, Angel L

2014-08-01

Human phosphoglycerate kinase 1 (hPGK1) is a glycolytic enzyme essential for ATP synthesis, and it is implicated in different pathological conditions such as inherited diseases, oncogenesis and activation of drugs for cancer and viral treatments. Particularly, mutations in hPGK1 cause human PGK1 deficiency, a rate metabolic conformational disease. We have recently found that most of these mutations cause protein kinetic destabilization by significant changes in the structure/energetics of the transition state for irreversible denaturation. In this work, we explore the relationships between protein conformation, thermodynamic and kinetic stability in hPGK1 by performing comprehensive analyses in a wide pH range (2.5-8). hPGK1 remains in a native conformation at pH 5-8, but undergoes a conformational transition to a molten globule-like state at acidic pH. Interestingly, hPGK1 kinetic stability remains essentially constant at pH 6-8, but is significantly reduced when pH is decreased from 6 to 5. We found that this decrease in kinetic stability is caused by significant changes in the energetic/structural balance of the denaturation transition state, which diverge from those found for disease-causing mutations. We also show that protein kinetic destabilization by acidic pH is strongly linked to lower thermodynamic stability, while in disease-causing mutations seems to be linked to lower unfolding cooperativity. These results highlight the plasticity of the hPGK1 denaturation mechanism that responds differently to changes in pH and in disease-causing mutations. New insight is presented into the different factors contributing to hPGK1 thermodynamic and kinetic stability and the role of denaturation mechanisms in hPGK1 deficiency. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Stability of Polyphenols Epigallocatechin Gallate and Pentagalloyl Glucose in a Simulated Digestive System

PubMed Central

Krook, Melanie A.; Hagerman, Ann E.

2012-01-01

Polyphenols found in foods and beverages are under intense scrutiny for their potential beneficial effects on human health. We examined the stability of two bioactive polyphenols, epigallocatechin-O-gallate (EGCg) and 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG), in a model digestive system at low oxygen tension with and without added digestive components and foods. Both compounds were stable at pH values of 5–6 and below, indicating gastric stability. Both compounds decomposed at pH 7.0. PGG was stabilized in a model system containing pepsin, pancreatin, bile and lipase, and/or baby food, but was not stabilized by dry cereal. EGCg was not stabilized by the addition of any biomolecule. The effects of polyphenols on human health should be evaluated in the context of their stability in the digestive tract with and without added digestive components and/or food. PMID:23028206

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate.

PubMed

Sato, A C K; Perrechil, F A; Costa, A A S; Santana, R C; Cunha, R L

2015-09-01

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5mg/mL) and ferulic acid (5 and 10mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH3. At pH3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH5), larger droplet size (pH3, 5 and 7) and higher pseudoplasticity (pH5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dispersion stability of a ceramic glaze achieved through ionic surfactant adsorption.

PubMed

Panya, Preecha; Arquero, Orn-anong; Franks, George V; Wanless, Erica J

2004-11-01

The adsorption of cetylpyridinium chloride (CPC) and sodium dodecylbenzenesulfonate (SDBS) onto a ceramic glaze mixture composed of limestone, feldspar, quartz, and kaolin has been investigated. Both adsorption isotherms and the average particle zeta potential have been studied in order to understand the suspension stability as a function of pH, ionic strength, and surfactant concentration. The adsorption of small amounts of cationic CPC onto the primarily negatively charged surfaces of the particles at pH 7 and 9 results in strong attraction and flocculation due to hydrophobic interactions. At higher surfactant concentrations a zeta potential of more than +60 mV results from the bilayered adsorbed surfactant, providing stability at salt concentrations < or = 0.01 M. At 0.1 M salt poor stability results despite substantial zeta potential values. Three mechanisms for SDBS adsorption have been identified. When anionic SDBS monomers either adsorb by electrostatic interactions with the few positive surface sites at high pH or adsorb onto like charged negative surface sites due to dispersion or hydrophobic interactions, the magnitude of the negative zeta potential increases slightly. At pH 9 this increase is enough to promote stability with an average zeta potential of more than -55 mV, whereas at pH 7 the zeta potential is lower at about -45 mV. The stability of suspensions at pH 7 is additionally due to steric repulsion caused by the adsorption of thick layers of neutrally charged Ca(DBS)2 complexes created when the surfactant interacts with dissolved calcium ions from the calcium carbonate component.

Influence of vehicle properties and excipients on hydrolytic and photochemical stability of curcumin in preparations containing Pluronics: studies of curcumin and curcuminoids XLVIII.

PubMed

Singh, R; Kristensen, S; Tønnesen, H H

2013-03-01

The influence of vehicle properties and excipients on the hydrolytic and photochemical stability of curcumin in Pluronic preparations, and the interactions between curcumin and Pluronics was investigated. Curcumin was found to be degraded by general acid-base catalyzed hydrolytic degradation in alkaline preparations. The degradation rate of curcumin was higher in carbonate buffer than in phosphate buffer (pH 8.8), while it was higher in phosphate buffer than in citrate buffer (pH 7.8). At pH 8.0-8.8 the degradation rate of curcumin increased compared to preparations with pH <8.0. The stabilizing effect of the Pluronics against hydrolytic degradation of curcumin was only detectable at pH 8.0-8.8, and it was highest for F127 and lowest for P85, in phosphate buffer pH 8.8. An increase in the ionic strength increased the stabilization against hydrolytic degradation of curcumin by all Pluronics. Addition of ethanol decreased the hydrolytic stability of curcumin in all Pluronics. Addition of PEG 400 decreased the hydrolytic stability in preparation with either P123 or F127 while the degradation in preparations with P85 remained the same as in P85 preparations without PEG 400. Vehicle properties and excipients did not to any large degree influence the spectroscopic properties or the photostability of curcumin in Pluronic preparations. Photochemical half life of curcumin was in the minutes range. Spectrophotometric data indicate that Pluronic aggregates most likely solubilize curcumin through hydrophobic interactions, although hydrogen-bonding may also be involved.

Stability studies on florfenicol using developed derivative spectrophotometric methods.

PubMed

Elimam, M M; Shantier, S W; Gadkariem, E A; Mohamed, M A; Osman, Z

2017-01-01

This study aims to investigate the stability of florfenicol using previously developed derivative spectrophotometric methods (D 1 and D 2 ). The studied stability-indicating pararmeters included alkali (NaOH, 1M), acid (HCl, 1M), pH changes (buffer pH 2.2-11), temperature (80°C and 100°C at pH 10) and light. A constructed pH profile for the drug degradation rate revealed a significant effect of pH on the drug stability between pH ranges 8 and 11. The obtained profile indicated first order dependence of K obs on [OH - ]. Arrhenius plot at pH 10 was found linear at temperatures 80°C and 100°C with estimated activation energy of 19.35kcal/mol. The calculated rate constant (K obs ), t ½ and t 90 at 25°C were found to be 1.8×10 -3 h, 385h and 58.3h, respectively. The photostability of florfenicol was also studied by exposing the drug solution to direct sunlight during mid-day time. The obtained results reflected the instability of florfenicol under the study conditions. Copyright © 2016 Académie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

Factors influencing the stability and type of hydroxyapatite stabilized Pickering emulsion.

PubMed

Zhang, Ming; Wang, Ai-Juan; Li, Jun-Ming; Song, Na; Song, Yang; He, Rui

2017-01-01

Hydroxyapatite (HAp) nanoparticle stabilized Pickering emulsion was fabricated with poly(l-lactic acid) dissolved in dichloromethane (CH 2 Cl 2 ) solution as oil phase and HAp aqueous dispersion as aqueous phase. Pickering emulsion was cured via in situ solvent evaporation method. Effect of PLLA concentrations, pH value, HAp concentrations, oil-water ratio, emulsification rates and times were studied on emulsion stability and emulsion type, etc. The results indicated emulsion stability increased with the increase of HAp concentration, emulsification rate and time; it is very stable when pH value of aqueous phase was adjusted to 10. Stable W/O and O/W emulsions were fabricated successfully using as-received HAp particles as stabilizer by adjusting the fabricating parameters. The interaction between HAp and PLLA played an important role to stabilize Pickering emulsions. SEM results indicated that both microsphere and porous materials were fabricated using emulsion stabilized by unmodified HAp nanoparticles, implying that both W/O and O/W emulsion type were obtained. Copyright © 2016 Elsevier B.V. All rights reserved.

The Effects of Various Amendments on Trace Element Stabilization in Acidic, Neutral, and Alkali Soil with Similar Pollution Index

PubMed Central

Kim, Min-Suk; Min, Hyun-Gi; Lee, Sang-Hwan; Kim, Jeong-Gyu

2016-01-01

Many studies have examined the application of soil amendments, including pH change-induced immobilizers, adsorbents, and organic materials, for soil remediation. This study evaluated the effects of various amendments on trace element stabilization and phytotoxicity, depending on the initial soil pH in acid, neutral, and alkali conditions. As in all types of soils, Fe and Ca were well stabilized on adsorption sites. There was an effect from pH control or adsorption mechanisms on the stabilization of cationic trace elements from inorganic amendments in acidic and neutral soil. Furthermore, acid mine drainage sludge has shown great potential for stabilizing most trace elements. In a phytotoxicity test, the ratio of the bioavailable fraction to the pseudo-total fraction significantly affected the uptake of trace elements by bok choy. While inorganic amendments efficiently decreased the bioavailability of trace elements, significant effects from organic amendments were not noticeable due to the short-term cultivation period. Therefore, the application of organic amendments for stabilizing trace elements in agricultural soil requires further study. PMID:27835687

Effects of Micro-environmental pH of Liposome on Chemical Stability of Loaded Drug

NASA Astrophysics Data System (ADS)

Shao, Xiao-Ru; Wei, Xue-Qin; Zhang, Shu; Fu, Na; Lin, Yun-Feng; Cai, Xiao-Xiao; Peng, Qiang

2017-08-01

Liposome is a promising carrier system for delivering bioactive molecules. However, the successful delivery of pH-sensitive molecules is still limited by the intrinsic instability of payloads in physiological environment. Herein, we developed a special liposome system that possesses an acidic micro-environment in the internal aqueous chamber to improve the chemical stability of pH-sensitive payloads. Curcumin-loaded liposomes (Cur-LPs) with varied internal pH values (pH 2.5, 5.0, or 7.4) were prepared. These Cur-LPs have similar particle size of 300 nm, comparable physical stabilities and analogous in vitro release profiles. Interestingly, the chemical stability of liposomal curcumin in 50% fetal bovine serum and its anticancer efficacy in vitro are both micro-environmental pH-dependent (Cur-LP-2.5 > Cur-LP-5.0 > Cur-LP-7.4). This serum stability still has space to be further enhanced to improve the applicability of Cur-LP. In conclusion, creating an acidic micro-environment in the internal chamber of liposome is feasible and efficient to improve the chemical stability of pH-sensitive payloads.

The Effects of Various Amendments on Trace Element Stabilization in Acidic, Neutral, and Alkali Soil with Similar Pollution Index.

PubMed

Kim, Min-Suk; Min, Hyun-Gi; Lee, Sang-Hwan; Kim, Jeong-Gyu

2016-01-01

Many studies have examined the application of soil amendments, including pH change-induced immobilizers, adsorbents, and organic materials, for soil remediation. This study evaluated the effects of various amendments on trace element stabilization and phytotoxicity, depending on the initial soil pH in acid, neutral, and alkali conditions. As in all types of soils, Fe and Ca were well stabilized on adsorption sites. There was an effect from pH control or adsorption mechanisms on the stabilization of cationic trace elements from inorganic amendments in acidic and neutral soil. Furthermore, acid mine drainage sludge has shown great potential for stabilizing most trace elements. In a phytotoxicity test, the ratio of the bioavailable fraction to the pseudo-total fraction significantly affected the uptake of trace elements by bok choy. While inorganic amendments efficiently decreased the bioavailability of trace elements, significant effects from organic amendments were not noticeable due to the short-term cultivation period. Therefore, the application of organic amendments for stabilizing trace elements in agricultural soil requires further study.

Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil.

PubMed

Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Liu, Zhao-Peng; Jin, Fei

2014-04-30

Cement stabilization is a practical approach to remediate soils contaminated with high levels of lead. However, the potential for leaching of lead out of these stabilized soils under variable acid rain pH conditions is a major environmental concern. This study investigates the effects of acid rain on the leaching characteristics of cement stabilized lead contaminated soil under different pH conditions. Clean kaolin clay and the same soil spiked with 2% lead contamination are stabilized with cement contents of 12 and 18% and then cured for 28 days. The soil samples are then subjected to a series of accelerated leaching tests (or semi-dynamic leaching tests) using a simulated acid rain leachant prepared at pH 2.0, 4.0 or 7.0. The results show that the strongly acidic leachant (pH ∼2.0) significantly altered the leaching behavior of lead as well as calcium present in the soil. However, the differences in the leaching behavior of the soil when the leachant was mildly acidic (pH ∼4.0) and neutral (pH ∼7.0) prove to be minor. In addition, it is observed that the lead contamination and cement content levels can have a considerable impact on the leaching behavior of the soils. Overall, the leachability of lead and calcium is attributed to the stability of the hydration products and their consequent influence on the soil buffering capacity and structure. Copyright © 2014 Elsevier B.V. All rights reserved.

Distinct structural changes detected by X-ray fiber diffraction in stabilization of F-actin by lowering pH and increasing ionic strength.

PubMed

Oda, T; Makino, K; Yamashita, I; Namba, K; Maéda, Y

2001-02-01

Lowering pH or raising salt concentration stabilizes the F-actin structure by increasing the free energy change associated with its polymerization. To understand the F-actin stabilization mechanism, we studied the effect of pH, salt concentration, and cation species on the F-actin structure. X-ray fiber diffraction patterns recorded from highly ordered F-actin sols at high density enabled us to detect minute changes of diffraction intensities and to precisely determine the helical parameters. F-actin in a solution containing 30 mM NaCl at pH 8 was taken as the control. F-actin at pH 8, 30 to 90 mM NaCl or 30 mM KCl showed a helical symmetry of 2.161 subunits per turn of the 1-start helix (12.968 subunits/6 turns). Lowering pH from 8 to 6 or replacing NaCl by LiCl altered the helical symmetry to 2.159 subunits per turn (12.952/6). The diffraction intensity associated with the 27-A meridional layer-line increased as the pH decreased but decreased as the NaCl concentration increased. None of the solvent conditions tested gave rise to significant changes in the pitch of the left-handed 1-start helix (approximately 59.8 A). The present results indicate that the two factors that stabilize F-actin, relatively low pH and high salt concentration, have distinct effects on the F-actin structure. Possible mechanisms will be discussed to understand how F-actin is stabilized under these conditions.

Stability of Synthetic Cathinones in Urine.

PubMed

Glicksberg, Lindsay; Kerrigan, Sarah

2018-03-01

In this report, we evaluate the concentration, pH, temperature and analyte-dependent effects on cathinone stability in preserved human urine. A total of 22 synthetic cathinones were evaluated at 100 ng/mL and 1,000 ng/mL in pH 4 and pH 8 urine over 6 months. Specimens were stored at -20°C, 4°C, 20°C and 32°C. The stability of synthetic cathinones was highly dependent on urine pH and storage temperature. Cathinones were considerably more stable in acidic urine (pH 4) at low temperature. In alkaline urine (pH 8) at 32°C, significant losses (>20%) were observed within hours for the majority of drugs. In contrast, all drugs were stable in frozen and refrigerated urine at pH 4 for the duration of the study. These results highlight the importance of sample storage and the potential for pre-analytical changes in concentration during routine shipping and handling of specimens. Significant structural influence was also observed. Cathinones bearing a tertiary amine (pyrrolidine group) were significantly more stable than their secondary amine counterparts. The methylenedioxy group also exerted a significant stabilizing effect on both the tertiary and secondary amines. In the absence of the methylenedioxy group, no significant differences in stability were observed between the unsubstituted and ring substituted secondary amines. Half-lives at ambient temperature in pH 8 urine ranged from 9 h (3-fluoromethcathinone) to 4.3 months (methylenedioxypyrovalerone and 3,4-methylenedioxy-α-pyrrolidinobutiophenone), demonstrating the importance of analyte dependence, and the dual stabilizing effect of both the pyrollidine and methylenedioxy groups. Biological evidence may be subjected to a variety of environmental conditions prior to, and during transport to the forensic laboratory. These findings demonstrate the inherent instability of certain cathinone species in biological evidence under some conditions. Moreover, this study highlights the need for quantitative drug findings in toxicological investigations to be interpreted cautiously, and within the context of specimen storage and integrity.

Effect of glucuronosylation on anthocyanin color stability.

PubMed

Osmani, Sarah Anne; Hansen, Esben Halkjaer; Malien-Aubert, Céline; Olsen, Carl-Erik; Bak, Søren; Møller, Birger Lindberg

2009-04-22

The effect of glucuronosylation on the color stability of anthocyanins was investigated using glucuronosylated anthocyanins isolated from the flower petals of the red daisy (Bellis perennis) or obtained by enzymatic in vitro synthesis using heterologously expressed red daisy glucuronosyltransferase BpUGT94B1. Color stability toward light and heat stress was assessed by monitoring CIELAB color coordinates and stability at pH 7.0 by A(550). Cyanidin-3-O-2''-O-glucuronosylglucoside showed improved color stability in response to light compared to both cyanidin 3-O-glucoside and cyanidin 3-O-2''-O-diglucoside. A similar increase in color stability was not observed following heat treatment. Glucuronosylation did not increase the stability of anthocyanins at pH 7.0 as determined by A(550). To test for a possible effect of glucuronosylation on the color stability of anthocyanins in plant extracts used for food coloration, an elderberry (Sambucus nigra) extract was glucuronosylated in vitro. Glucuronosylation of approximately 50% of total anthocyanins proceeded fast and resulted in increased color stability in response to both heat and light. The data show that glucuronosylation may be used to stabilize industrially used extracts of natural colorants.

Preformulation considerations for controlled release dosage forms. Part II. Selected candidate support.

PubMed

Chrzanowski, Frank

2008-01-01

Practical examples of preformulation support of the form selected for formulation development are provided using several drug substances (DSs). The examples include determination of the solubilities vs. pH particularly for the range pH 1 to 8 because of its relationship to gastrointestinal (GI) conditions and dissolution method development. The advantages of equilibrium solubility and trial solubility methods are described. The equilibrium method is related to detecting polymorphism and the trial solubility method, to simplifying difficult solubility problems. An example of two polymorphs existing in mixtures of DS is presented in which one of the forms is very unstable. Accelerating stability studies are used in conjunction with HPLC and quantitative X-ray powder diffraction (QXRD) to demonstrate the differences in chemical and polymorphic stabilities. The results from two model excipient compatibility methods are compared to determine which has better predictive accuracy for room temperature stability. A DSC (calorimetric) method and an isothermal stress with quantitative analysis (ISQA) method that simulates wet granulation conditions were compared using a 2 year room temperature sample set as reference. An example of a pH stability profile for understanding stability and extrapolating stability to other environments is provided. The pH-stability of omeprazole and lansoprazole, which are extremely unstable in acidic and even mildly acidic conditions, are related to the formulation of delayed release dosage forms and the resolution of the problem associated with free carboxyl groups from the enteric coating polymers reacting with the DSs. Dissolution method requirements for CR dosage forms are discussed. The applicability of a modified disintegration time (DT) apparatus for supporting CR dosage form development of a pH sensitive DS at a specific pH such as duodenal pH 5.6 is related. This method is applicable for DSs such as peptides, proteins, enzymes and natural products where physical observation can be used in place of a difficult to perform analytical method, saving resources and providing rapid preformulation support.

Thermal inactivation reaction rates for ricin are influenced by pH and carbohydrates.

PubMed

Zhang, Zhe; Triplett, Odbert A; Nguyen, Kiet T; Melchior, William B; Taylor, Kelly; Jackson, Lauren S; Tolleson, William H

2013-08-01

Ricin is a lethal protein toxin produced by the castor bean plant. Ricin is known to possess significant heat resistance. Therefore, we placed it in a variety of foods to study the influence of the food matrix on behavior of a thermally stable protein toxin. First order rate constants for the thermal inactivation of ricin in foods and simple buffers were measured using cytotoxicity assays. We observed greater thermal stability at 75 °C for the cytotoxic activity of ricin when it was placed in a yogurt-containing fruit drink compared to its stability when placed in the other foods tested. We found that galactose and high molecular weight exopolysaccharides present in various dairy products contributed to the thermal stability of ricin. Differential scanning calorimetry also showed enhanced thermal stability for ricin at pH 4.5. Our results demonstrate the importance of considering pH and the presence of stabilizing ligands in the thermal inactivation of protein toxins in foods. Published by Elsevier Ltd.

Investigation by response surface methodology of the combined effect of pH and composition of water-methanol mixtures on the stability of curcuminoids.

PubMed

D'Archivio, Angelo Antonio; Maggi, Maria Anna

2017-03-15

Response surface methodology, coupled to a full factorial three-level experimental design, was applied to investigate the combined influence of pH (between 7.0 and 8.6) and composition of methanol-water mixtures (between 30 and 70% v/v of methanol content) on the stability of curcumin and its analogues demethoxycurcumin and bisdemethoxycurcumin. The response plots revealed that addition of methanol noticeably improved the stability of curcuminoids, this effect being both pH- and structure-dependent. In the central point of the experimental domain, half-life times of curcumin, demethoxycurcumin and bisdemethoxycurcumin were 3.8±0.2, 27±2 and 251±17h, respectively. Stability of curcuminoids increased at lower pH and higher methanol content and decreased in the opposite vertex of the experimental domain. These results can be interpreted by assuming that addition of methanol to water produces a different variation of pH of the medium and apparent pKa values of the ionisable groups of curcuminoids. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dissolution enhancement of gliclazide using pH change approach in presence of twelve stabilizers with various physico-chemical properties.

PubMed

Talari, Roya; Varshosaz, Jaleh; Mostafavi, Seyed Abolfazl; Nokhodchi, Ali

2009-01-01

The micronization using milling process to enhance dissolution rate is extremely inefficient due to a high energy input, and disruptions in the crystal lattice which can cause physical or chemical instability. Therefore, the aim of the present study is to use in situ micronization process through pH change method to produce micron-size gliclazide particles for fast dissolution hence better bioavailability. Gliclazide was recrystallized in presence of 12 different stabilizers and the effects of each stabilizer on micromeritic behaviors, morphology of microcrystals, dissolution rate and solid state of recrystallized drug particles were investigated. The results showed that recrystallized samples showed faster dissolution rate than untreated gliclazide particles and the fastest dissolution rate was observed for the samples recrystallized in presence of PEG 1500. Some of the recrystallized drug samples in presence of stabilizers dissolved 100% within the first 5 min showing at least 10 times greater dissolution rate than the dissolution rate of untreated gliclazide powders. Micromeritic studies showed that in situ micronization technique via pH change method is able to produce smaller particle size with a high surface area. The results also showed that the type of stabilizer had significant impact on morphology of recrystallized drug particles. The untreated gliclazide is rod or rectangular shape, whereas the crystals produced in presence of stabilizers, depending on the type of stabilizer, were very fine particles with irregular, cubic, rectangular, granular and spherical/modular shape. The results showed that crystallization of gliclazide in presence of stabilizers reduced the crystallinity of the samples as confirmed by XRPD and DSC results. In situ micronization of gliclazide through pH change method can successfully be used to produce micron-sized drug particles to enhance dissolution rate.

Stabilizing sodium hypochlorite at high pH: effects on soft tissue and dentin.

PubMed

Jungbluth, Holger; Marending, Monika; De-Deus, Gustavo; Sener, Beatrice; Zehnder, Matthias

2011-05-01

When sodium hypochlorite solutions react with tissue, their pH drops and tissue sorption decreases. We studied whether stabilizing a NaOCl solution at a high pH would increase its soft-tissue dissolution capacity and effects on the dentin matrix compared with a standard NaOCl solution of the same concentration and similar initial pH. NaOCl solutions were prepared by mixing (1:1) a 10% stock solution with water (standard) or 2 mol/L NaOH (stabilized). Physiological saline and 1 mol/L NaOH served as the controls. Chlorine content and alkaline capacity of NaOCl solutions were determined. Standardized porcine palatal soft-tissue specimens and human root dentin bars were exposed to test and control solutions. Weight loss percentage was assessed in the soft-tissue dissolution assay. Three-point bending tests were performed on the root dentin bars to determine the modulus of elasticity and flexural strength. Values between groups were compared using one-way analysis of variance with the Bonferroni correction for multiple testing (α < .05). Both solutions contained 5% NaOCl. One milliliter of the standard and the stabilized solution consumed 4.0 mL and 13.7 mL of a 0.1-mol/L HCl solution before they reached a pH level of 7.5, respectively. The stabilized NaOCl dissolved significantly more soft tissue than the standard solution, and the pH remained high. It also caused a higher loss in elastic modulus and flexure strength (P < .05) than the control solutions, whereas the standard solution did not. NaOH-stabilized NaOCl solutions have a higher alkaline capacity and are thus more proteolytic than standard counterparts. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Stability and Transport of Cerium Oxide Nanoparticles in Aqueous Environment: Effect of pH, Ionic Strength, and Organic Matter.

EPA Science Inventory

This study investigated the stability and transport of CeO2 NPs under the influence of pH, natural/manmade organic matter, and electrolyte (NaCl) concentrations. In column test, effluent concentration of CeO2 NPs was close to the influent at pH 10, while most NPs deposited on san...

Influence of pH, benzoic acid, glutathione, EDTA, 4-hexylresorcinol, and sodium chloride on the pressure inactivation kinetics of mushroom polyphenol oxidase.

PubMed

Weemaes, C A; Ludikhuyze, L R; Van den Broeck, I; Hendrickx, M E

1999-09-01

Pressure inactivation of mushroom PPO was studied for pH values ranging from 4 to 8, and the effect of some antibrowning agents on the pressure stability of mushroom PPO at pH 6.5 was evaluated. pH reduction below 6.5 resulted in a lowered inactivation threshold pressure and an increase of the absolute value of the activation volume (or a decrease of the z(p) value), the latter two parameters reflecting the pressure dependency of the inactivation rate constant. An increase in pH from 6.5 to 8, on the other hand, did only marginally affect the pressure stability of the enzyme. Mushroom PPO at pH 6.5 was markedly sensitized toward pressure by the presence of 2.5 mM 4-hexylresorcinol and slightly stabilized by the presence of 5 mM EDTA. The presence of 5 mM glutathione, sodium chloride, or benzoic acid caused no significant alteration of the enzyme pressure stability. Only in the presence of 4-hexylresorcinol, significant changes of the activation volume and z(p) value were noticed.

Oil-in-water emulsions as a delivery system for n-3 fatty acids in meat products.

PubMed

Salminen, Hanna; Herrmann, Kurt; Weiss, Jochen

2013-03-01

The oxidative and physical stabilities of oil-in-water emulsions containing n-3 fatty acids (25 wt.% oil, 2.5 wt.% whey protein, pH 3.0 or pH 6.0), and their subsequent incorporation into meat products were investigated. The physical stability of fish oil emulsions was excellent and neither coalescence nor aggregation occurred during storage. Oxidative stability was better at pH 6.0 compared to pH 3.0 likely due to antioxidative continuous phase proteins. Incorporation of fish oil emulsions into pork sausages led to an increase in oxidation compared to sausages without the added fish oil emulsion. Confocal microscopy of pork sausages with fish oil emulsions revealed that droplets had coalesced in the meat matrix over time which may have contributed to the decreased oxidative stability. Results demonstrate that although interfacial engineering of n-3 fatty acids containing oil-in-water emulsions provides physical and oxidative stability of the base-emulsion, their incorporation into complex meat matrices is a non-trivial undertaking and products may incur changes in quality over time. Copyright © 2012 Elsevier Ltd. All rights reserved.

The effect of high pressure and residual oxygen on the color stability of minced cured restructured ham at different levels of drying, pH, and NaCl.

PubMed

Bak, Kathrine Holmgaard; Lindahl, Gunilla; Karlsson, Anders H; Lloret, Elsa; Gou, Pere; Arnau, Jacint; Orlien, Vibeke

2013-10-01

Color stability of minced cured restructured ham was studied by considering the effects of high pressure (HP) (600 MPa, 13°C, 5 min), raw meat pH24 (low, normal, high), salt content (15, 30 g/kg), drying (20%, 50% weight loss), and residual oxygen level (0.02%-0.30%). Raw hams were selected by pH24 in Semimembranosus, mixed with additives, frozen, sliced, and dried by the Quick-Dry-Slice® (QDS) process followed by HP treatment or not (control). Packaging and storage simulated industrial packaging: modified atmosphere containing 80% N2, 20% CO2, and residual O2 in one of three intervals: <0.1%, 0.1%-0.2%, or 0.2%-0.3%, and retail storage conditions: chill storage, 12 h light, 12 h darkness. HP improved the stability of the redness of 20% QDS hams, while the stabilizing effect on 50% QDS hams was smaller, concluding that water has the dominating role. Raw meat pH24, salt content, and residual oxygen level had varying effects on the stability of the red color. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigations Concerning Hydrolysis and Stabilization of Antiradiation Compounds

DTIC Science & Technology

1982-01-01

Stability of Unencapsulated WR 2721 31 V. DISCUSSION 35 A. Microencapsulation 35 1. Microspheres 35 2. Microcapsules 35 B. Hydrolytic Stability of...in 1.5 hours at 370C in buffered solutions of pH 1.0 or 3.0. 3^ The more promising microspheres and microcapsules released the WR 2721 within two...hours at pH 7.5 in buffered solutions. 4) Analytical procedures were developed for: "♦ WR 2721 (directly) in microcapsules using an HPLC

Biophysical stability of hyFc fusion protein with regards to buffers and various excipients.

PubMed

Lim, Jun Yeul; Kim, Nam Ah; Lim, Dae Gon; Eun, Chang-yong; Choi, Donghoon; Jeong, Seong Hoon

2016-05-01

A novel non-cytolytic hybrid Fc (hyFc) with an intact Ig structure without any mutation in the hyFc region, was developed to construct a long-acting agonistic protein. The stability of interleukin-7 (IL-7) fused with the hyFc (GXN-04) was evaluated to develop early formulations. Various biophysical methods were utilized and three different buffer systems with various pH ranges were investigated including histidine-acetate, sodium citrate, and tris buffers. Various excipients were incorporated into the systems to obtain optimum protein stability. Two evident thermal transitions were observed with the unfolding of IL-7 and hyFc. The Tm and ΔH increased with pH, suggesting increased conformational stability. Increased Z-average size with PDI and decreased zeta potential with pH increase, with the exception of tris buffer, showed aggregation issues. Moreover, tris buffer at higher pH showed aggregation peaks from DLS. Non-ionic surfactants were effective against agitation by outcompeting protein molecules for hydrophobic surfaces. Sucrose and sorbitol accelerated protein aggregation during agitation, but exhibited a protective effect against oxidation, with preferential exclusion favoring the compact states of GXN-04. The stability of GXN-04 was varied by basal buffers and excipients, hence the buffers and excipients need to be evaluated carefully to achieve the maximum stability of proteins. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemical stability of insulin. 3. Influence of excipients, formulation, and pH.

PubMed

Brange, J; Langkjaer, L

1992-01-01

The influence of auxiliary substances and pH on the chemical transformations of insulin in pharmaceutical formulation, including various hydrolytic and intermolecular cross-linking reactions, was studied. Bacteriostatic agents had a profound stabilizing effect--phenol > m-cresol > methylparaben--on deamidation as well as on insulin intermolecular cross-linking reactions. Of the isotonicity substances, NaCl generally had a stabilizing effect whereas glycerol and glucose led to increased chemical deterioration. Phenol and sodium chloride exerted their stabilizing effect through independent mechanisms. Zinc ions, in concentrations that promote association of insulin into hexamers, increase the stability, whereas higher zinc content had no further influence. Protamine gave rise to additional formation of covalent protamine-insulin products which increased with increasing protamine concentration. The impact of excipients on the chemical processes seems to be dictated mainly via an influence on the three-dimensional insulin structure. The effect of the physical state of the insulin on the chemical stability was also complex, suggesting an intricate dependence of intermolecular proximity of involved functional groups. At pH values below five and above eight, insulin degrades relatively fast. At acid pH, deamidation at residue A21 and covalent insulin dimerization dominates, whereas disulfide reactions leading to covalent polymerization and formation of A- and B-chains prevailed in alkaline medium. Structure-reactivity relationship is proposed to be a main determinant for the chemical transformation of insulin.

Immobilization of Candida antarctica lipase B by covalent attachment to green coconut fiber.

PubMed

Brígida, Ana I S; Pinheiro, Alvaro D T; Ferreira, Andrea L O; Pinto, Gustavo A S; Gonçalves, Luciana R B

2007-04-01

The objective of this study was to covalently immobilize Candida antarctica type B lipase (CALB) onto silanized green coconut fibers. Variables known to control the number of bonds between enzyme and support were evaluated including contact time, pH, and final reduction with sodium borohydride. Optimal conditions for lipase immobilization were found to be 2 h incubation at both pH 7.0 and 10.0. Thermal stability studies at 60 degrees C showed that the immobilized lipase prepared at pH 10.0 (CALB-10) was 363-fold more stable than the soluble enzyme and 5.4-fold more stable than the biocatalyst prepared at pH 7.0 (CALB-7). CALB-7 was found to have higher specific activity and better stability when stored at 5 degrees C. When sodium borohydride was used as reducing agent on CALB-10 there were no improvement in storage stability and at 60 degrees C stability was reduced for both CALB-7 and CALB-10.

Immobilization of Candida antarctica Lipase B by Covalent Attachment to Green Coconut Fiber

NASA Astrophysics Data System (ADS)

Brígida, Ana I. S.; Pinheiro, Álvaro D. T.; Ferreira, Andrea L. O.; Pinto, Gustavo A. S.; Gonçalves, Luciana R. B.

The objective of this study was to covalently immobilize Candida antarctica type B lipase (CALB) onto silanized green coconut fibers. Variables known to control the number of bonds between enzyme and support were evaluated including contact time, pH, and final reduction with sodium borohydride. Optimal conditions for lipase immobilization were found to be 2h incubation at both pH 7.0 and 10.0. Thermal stability studies at 60°C showed that the immobilized lipase prepared at pH 10.0 (CALB-10) was 363-fold more stable than the soluble enzyme and 5.4-fold more stable than the biocatalyst prepared at pH 7.0 (CALB-7). CALB-7 was found to have higher specific activity and better stability when stored at 5°C. When sodium borohydride was used as reducing agent on CALB-10 there were no improvement in storage stability and at 60°C stability was reduced for both CALB-7 and CALB-10.

Toxicity evaluation of pH dependent stable Achyranthes aspera herbal gold nanoparticles

NASA Astrophysics Data System (ADS)

Tripathi, Alok; Kumari, Sarika; Kumar, Arvind

2016-01-01

Nanoparticles have gained substantial attention for the control of various diseases. However, any adverse effect of herbal gold nanoparticles (HGNPs) on animals including human being has not been investigated in details. The objectives of current study are to assess the cytotoxicity of HGNPs synthesized by using leaf extract of Achyranthes aspera, and long epoch stability. The protocol deals with stability of HGNPs in pH dependent manner. Visually, HGNPs formation is characterized by colour change of extract from dark brown to dark purple after adding gold chloride solution (1 mM). The 100 μg/ml HGNPs concentration has been found nontoxic to the cultured spleenocyte cells. Spectrophotometric analysis of nanoparticles solution gave a peak at 540 nm which corresponds to surface plasmon resonance absorption band. As per scanning electron microscopy and Transmission electron microscopy (TEM), size of HGNPs are in the range of 50-80 nm (average size 70 nm) with spherical morphology. TEM-selected area electron diffraction observation showed hexagonal texture. HGNPs showed substantial stability at higher temperature (85 °C), pH 10 and salt concentration (5 M). The zeta potential value of HGNPs is -35.9 mV at temperature 25 °C, pH 10 showing its good quality with better stability in comparison to pH 6 and pH 7. The findings advocate that the protocol for the synthesis of HGNPs is easy and quick with good quality and long epoch stability at pH 10. Moreover, non-toxic dose could be widely applicable for human health as a potential nano-medicine in the future to cure diseases.

Sodium caseinate stabilized zein colloidal particles.

PubMed

Patel, Ashok R; Bouwens, Elisabeth C M; Velikov, Krassimir P

2010-12-08

The present work deals with the preparation and stabilization of zein colloidal particles using sodium caseinate as electrosteric stabilizer. Colloidal particles with well-defined size range (120-150 nm) and negative surface potential (-29 to -47 mV) were obtained using a simple antisolvent precipitation method. Due to the presence of caseinate, the stabilized colloidal particles showed a shift of isoelectric point (IEP) from 6.0 to around pH 5.0 and thus prevent the aggregation of zein near its native IEP (pH 6.2). The particles also showed good stability to varying ionic strength (15 mM-1.5 M NaCl). Furthermore, stabilized particles retained the property of redispersibility after drying. In vitro protein hydrolysis study confirmed that the presence of caseinate did not alter the digestibility of zein. Such colloidal particles could potentially serve as all-natural delivery systems for bioactive molecules in food, pharmaceutical, and agricultural formulations.

Insight into the stability of poly(diallydimethylammoniumchloride) and polybrene poly cationic coatings in capillary electrophoresis.

PubMed

Pei, Lei; Lucy, Charles A

2014-10-24

Polycationic polymers are widely used in capillary electrophoresis (CE) as surface coatings to prevent protein adsorption and control electroosmotic flow (EOF). Such semi-permanent coatings are formed by flushing the capillary with a quaternary amine-based polymer such as poly(diallydimethylammonium chloride) (PDADMAC) or polybrene. Compared to covalent capillary coatings, the claimed advantages of adsorptive polycation coatings are their simple preparation and that they are not limited to the pH 2-8 range as are covalent coatings. However, while the latter is commonly claimed, few studies have demonstrated the stability of polycationic coatings at extreme pH. Herein PDADMAC and polybrene are studied as model cationic coatings. PDADMAC with higher molecular weight (M.W.) demonstrated higher EOF stability at pH 9.5, with PDADMAC of M.W. less than 200,000 being unstable at pH 9.5. X-ray photoelectron spectroscopy (XPS) shows that the quaternary amines of PDADMAC and polybrene were slowly converted to tertiary amines in alkaline solution and more rapidly when adsorbed on a silica surface. The degraded polycation deprotonated at pH >7, resulting in loss of polymer from the surface and diminishing EOF. Successive multiple ionic layer (SMIL) coatings show greater alkaline stability by distancing the polycation from the surface. Separations of inorganic anions at pH 9.5 illustrate the degradation behavior and enhanced stability of higher M.W. polycationic coatings. Copyright © 2014 Elsevier B.V. All rights reserved.

Lentil and chickpea protein-stabilized emulsions: optimization of emulsion formulation.

PubMed

Can Karaca, Asli; Nickerson, Michael T; Low, Nicholas H

2011-12-28

Chickpea and lentil protein-stabilized emulsions were optimized with regard to pH (3.0-8.0), protein concentration (1.1-4.1% w/w), and oil content (20-40%) for their ability to form and stabilize oil-in-water emulsions using response surface methodology. Specifically, creaming stability, droplet size, and droplet charge were assessed. Optimum conditions for minimal creaming (no serum separation after 24 h), small droplet size (<2 μm), and high net droplet charge (absolute value of ZP > 40 mV) were identified as 4.1% protein, 40% oil, and pH 3.0 or 8.0, regardless of the plant protein used for emulsion preparation.

Broad control of disulfide stability through microenvironmental effects and analysis in complex redox environments.

PubMed

Wu, Chuanliu; Wang, Shuo; Brülisauer, Lorine; Leroux, Jean-Christophe; Gauthier, Marc A

2013-07-08

Disulfide bonds stabilize the tertiary- and quaternary structure of proteins. In addition, they can be used to engineer redox-sensitive (bio)materials and drug-delivery systems. Many of these applications require control of the stability of the disulfide bond. It has recently been shown that the charged microenvironment of the disulfide can be used to alter their stability by ∼3 orders of magnitude in a predictable and finely tunable manner at acidic pH. The aim of this work is to extend these findings to physiological pH and to demonstrate the validity of this approach in complex redox milieu. Disulfide microenvironments were manipulated synergistically with steric hindrance herein to control disulfide bond stability over ∼3 orders of magnitude at neutral pH. Control of disulfide stability through microenvironmental effects could also be observed in complex redox buffers (including serum) and in the presence of cells. Such fine and predictable control of disulfide properties is not achievable using other existing approaches. These findings provide easily implementable and general tools for controlling the responsiveness of biomaterials and drug delivery systems toward various local endogenous redox environments.

Factors that affect Pickering emulsions stabilized by graphene oxide.

PubMed

He, Yongqiang; Wu, Fei; Sun, Xiying; Li, Ruqiang; Guo, Yongqin; Li, Chuanbao; Zhang, Lu; Xing, Fubao; Wang, Wei; Gao, Jianping

2013-06-12

Stable Pickering emulsions were prepared using only graphene oxide (GO) as a stabilizer, and the effects of the type of oil, the sonication time, the GO concentration, the oil/water ratio, and the pH value on the stability, type, and morphology of these emulsions were investigated. In addition, the effects of salt and the extent of GO reduction on emulsion formation and stability were studied and discussed. The average droplet size decreased with sonication time and with GO concentration, and the emulsions tended to achieve good stability at intermediate oil/water ratios and at low pH values. In all solvents, the emulsions were of the oil-in-water type, but interestingly, some water-in-oil-in-water (w/o/w) multiple emulsion droplets were also observed with low GO concentrations, low pH values, high oil/water ratios, high salt concentrations, or moderately reduced GO in the benzyl chloride-water system. A Pickering emulsion stabilized by Ag/GO was also prepared, and its catalytic performance for the reduction of 4-nitrophenol was investigated. This research paves the way for the fabrication of graphene-based functional materials with novel nanostructures and microstructures.

Nanoparticle-stabilized liposomes for pH-responsive gastric drug delivery.

PubMed

Thamphiwatana, Soracha; Fu, Victoria; Zhu, Jingying; Lu, Diannan; Gao, Weiwei; Zhang, Liangfang

2013-10-01

We report a novel pH-responsive gold nanoparticle-stabilized liposome system for gastric antimicrobial delivery. By adsorbing small chitosan-modified gold nanoparticles (diameter ~10 nm) onto the outer surface of negatively charged phospholipid liposomes (diameter ~75 nm), we show that at gastric pH the liposomes have excellent stability with limited fusion ability and negligible cargo releases. However, when the stabilized liposomes are present in an environment with neutral pH, the gold stabilizers detach from the liposomes, resulting in free liposomes that can actively fuse with bacterial membranes. Using Helicobacter pylori as a model bacterium and doxycycline as a model antibiotic, we demonstrate such pH-responsive fusion activity and drug release profile of the nanoparticle-stabilized liposomes. Particularly, at neutral pH the gold nanoparticles detach, and thus the doxycycline-loaded liposomes rapidly fuse with bacteria and cause superior bactericidal efficacy as compared to the free doxycycline counterpart. Our results suggest that the reported liposome system holds a substantial potential for gastric drug delivery; it remains inactive (stable) in the stomach lumen but actively interacts with bacteria once it reaches the mucus layer of the stomach where the bacteria may reside.

Limitations and possibilities of green synthesis and long-term stability of colloidal Ag nanoparticles

NASA Astrophysics Data System (ADS)

Velgosová, Oksana; Mražíková, Anna

2017-12-01

In this paper the influence of algae life cycle and the solutions pH on the green synthesis of colloidal Ag nanoparticles (AgNPs) as well as effect of different storage conditions on AgNPs long-term stability was investigated. Silver nanoparticles were biologically synthesized using extracts of Parachlorella kessleri algae cultivated 1, 2, 3 and 4 weeks. The formation of AgNPs was monitored using a UV-vis spectrophotometer and verified by TEM observation. The results confirmed formation of polyhedron and/or near polyhedron AgNPs, ranging between 5 and 60 nm in diameter. The age of algae influenced the synthesis rate and an amount of AgNPs in solution. The best results were obtained using tree weeks old algae. UV-vis analysis and TEM observation also revealed that the size and the stability of AgNPs depend on the pH of solution. AgNPs formed in solutions of higher pH (8 and 10) are polyhedron, fine, with narrow size interval and stabile. Nanoparticles formed in solutions of low pH (2, 4 and 6) started to lose their stability on 10th day of experiment, and the particle size interval was wide. The long-term stability of AgNPs can be influenced by light and temperature conditions. The most significant stability loss was observed at day light and room temperature (21°C). After 200-days significant amount of agglomerated particles settled on the bottom of the Erlenmeyer flask. AgNPs stored at dark and room temperature showed better long-term stability, weak particles agglomeration was observed. AgNPs stored at dark and at temperature 5°C showed the best long-term stability. Such AgNPs remained spherical, fine (5-20 nm), with narrow size interval and stable (no agglomeration) even after more than six months.

Optimization of extraction of novel pectinase enzyme discovered in red pitaya (Hylocereus polyrhizus) peel.

PubMed

Zohdi, Nor Khanani; Amid, Mehrnoush

2013-11-20

Plant peels could be a potential source of novel pectinases for use in various industrial applications due to their broad substrate specificity with high stability under extreme conditions. Therefore, the extraction conditions of a novel pectinase enzyme from pitaya peel was optimized in this study. The effect of extraction variables, namely buffer to sample ratio (2:1 to 8:1, X₁), extraction temperature (-15 to +25 °C, X₂) and buffer pH (4.0 to 12.0, X₃) on specific activity, temperature stability, storage stability and surfactant agent stability of pectinase from pitaya peel was investigated. The study demonstrated that the optimum conditions for the extraction of pectinase from pitaya sources could improve the enzymatic characteristics of the enzyme and protect its activity and stability during the extraction procedure. The optimum extraction conditions cause the pectinase to achieve high specific activity (15.31 U/mg), temperature stability (78%), storage stability (88%) and surfactant agent stability (83%). The most desirable conditions to achieve the highest activity and stability of pectinase enzyme from pitaya peel were the use of 5:1 buffer to sample ratio at 5 °C and pH 8.0.

Structural and physical properties of collagen extracted from moon jellyfish under neutral pH conditions.

PubMed

Miki, Ayako; Inaba, Satomi; Baba, Takayuki; Kihira, Koji; Fukada, Harumi; Oda, Masayuki

2015-01-01

We extracted collagen from moon jellyfish under neutral pH conditions and analyzed its amino acid composition, secondary structure, and thermal stability. The content of hydroxyproline was 4.3%, which is lower than that of other collagens. Secondary structure analysis using circular dichroism (CD) showed a typical collagen helix. The thermal stability of this collagen at pH 3.0 was lower than those from fish scale and pig skin, which also correlates closely with jellyfish collagen having lower hydroxyproline content. Because the solubility of jellyfish collagen used in this study at neutral pH was quite high, it was possible to analyze its structural and physical properties under physiological conditions. Thermodynamic analysis using CD and differential scanning calorimetry showed that the thermal stability at pH 7.5 was higher than at pH 3.0, possibly due to electrostatic interactions. During the process of unfolding, fibrillation would occur only at neutral pH.

A PARADOXICAL RELATION BETWEEN ZETA POTENTIAL AND SUSPENSION STABILITY IN S AND R VARIANTS OF INTESTINAL BACTERIA

PubMed Central

Joffe, Eleanore W.; Mudd, Stuart

1935-01-01

The relation between electrokinetic potential and suspension stability of four strains of non-flagellate intestinal bacteria has been studied. The smooth forms have ζ-potentials which approximate zero over a wide range of pH and salt concentration, yet nevertheless form stable suspensions. The rough variants have ζ-potentials which vary with pH and electrolyte concentration in the familiar way. The rough forms have values of ζ-potential critical for their suspension stability. PMID:19872869

Box-Behnken study design for optimization of bicalutamide-loaded nanostructured lipid carrier: stability assessment.

PubMed

Kudarha, Ritu; Dhas, Namdev L; Pandey, Abhijeet; Belgamwar, Veena S; Ige, Pradum P

2015-01-01

Bicalutamide (BCM) is an anti-androgen drug used to treat prostate cancer. In this study, nanostructured lipid carriers (NLCs) were chosen as a carrier for delivery of BCM using Box-Behnken (BB) design for optimizing various quality attributes such as particle size and entrapment efficiency which is very critical for efficient drug delivery and high therapeutic efficacy. Stability of formulated NLCs was assessed with respect to storage stability, pH stability, hemolysis, protein stability, serum protein stability and accelerated stability. Hot high-pressure homogenizer was utilized for formulation of BCM-loaded NLCs. In BB response surface methodology, total lipid, % liquid lipid and % soya lecithin was selected as independent variable and particle size and %EE as dependent variables. Scanning electron microscopy (SEM) was done for morphological study of NLCs. Differential scanning calorimeter and X-ray diffraction study were used to study crystalline and amorphous behavior. Analysis of design space showed that process was robust with the particle size less than 200 nm and EE up to 78%. Results of stability studies showed stability of carrier in various storage conditions and in different pH condition. From all the above study, it can be concluded that NLCs may be suitable carrier for the delivery of BCM with respect to stability and quality attributes.

Isoelectric focusing of red blood cells in a density gradient stabilized column

NASA Technical Reports Server (NTRS)

Smolka, A. J. K.; Miller, T. Y.

1980-01-01

The effects of Ficoll and cell application pH on red blood cell electrophoretic mobility and focusing pH were investigated by focusing cells in a density gradient stabilized column. Sample loading, cell dispersion, column conductivity, resolution of separation, and the effect of Ampholines were examined.

Distribution of chloride, pH, resistivity, and sulfate levels in backfill for mechanically-stabilized earth walls and implications for corrosion testing.

DOT National Transportation Integrated Search

2015-05-01

The ultimate goals of this research were to improve quality, speed completion, and reduce risk in mechanically-stabilized : earth (MSE) wall projects. Research objectives were to assure (1) that variability in the corrosion properties of soil (pH, : ...

Development of a Low Toxicity Urine Pretreatment for Water Recovery in Space

NASA Technical Reports Server (NTRS)

Adam, Niklas; Alvarez, Giraldo; Mitchell, Julie; Pickering, Karen; Shull, Sarah; Carrier, Chris; Vega, Letty

2015-01-01

Wastewater stabilization was an essential component of the spacecraft water cycle. The purpose of stabilizing wastewater was two-fold. First, stabilization prevents the breakdown of urea into ammonia, a toxic gas at high concentrations. Second, it prevents the growth of microorganisms, thereby mitigating hardware and water quality issues due to due biofilm and planktonic growth. Current stabilization techniques involve oxidizers and strong acids (pH=2) such as chromic and sulfuric acid, which are highly toxic and pose a risk to crew health. The purpose of this effort was to explore less toxic stabilization techniques, such as food-grade and commercial care preservatives. Additionally, certain preservatives were tested in the presence of a low-toxicity organic acid. Triplicate 300-mL volumes of urine were dosed with a predetermined quantity of stabilizer and stored for two weeks. During that time, pH, total organic carbon (TOC), ammonia, and turbidity were monitored. Those preservatives that showed the lowest visible microbial growth and stable pH were further tested in a six-month stability study. The results of the six-month study are also included in this paper. Additionally, the pretreatment formulations were tested to determine if the pretreated urine could be distilled to remove 85% of the water, as would occur on the ISS. The goal of the pretreatment was to produce no solids in the resulting brine at 85% water recovery.

Molecular Dynamics Driven Design of pH-Stabilized Mutants of MNEI, a Sweet Protein.

PubMed

Leone, Serena; Picone, Delia

2016-01-01

MNEI is a single chain derivative of monellin, a plant protein that can interact with the human sweet taste receptor, being therefore perceived as sweet. This unusual physiological activity makes MNEI a potential template for the design of new sugar replacers for the food and beverage industry. Unfortunately, applications of MNEI have been so far limited by its intrinsic sensitivity to some pH and temperature conditions, which could occur in industrial processes. Changes in physical parameters can, in fact, lead to irreversible protein denaturation, as well as aggregation and precipitation. It has been previously shown that the correlation between pH and stability in MNEI derives from the presence of a single glutamic residue in a hydrophobic pocket of the protein. We have used molecular dynamics to study the consequences, at the atomic level, of the protonation state of such residue and have identified the network of intramolecular interactions responsible for MNEI stability at acidic pH. Based on this information, we have designed a pH-independent, stabilized mutant of MNEI and confirmed its increased stability by both molecular modeling and experimental techniques.

The role of lecithin degradation on the pH dependent stability of halofantrine encapsulated fat nano-emulsions.

PubMed

Haidar, Iman; Harding, Ian H; Bowater, Ian C; Eldridge, Daniel S; Charman, William N

2017-08-07

We report on the successful incorporation of the antimalarial drug, halofantrine, into laboratory based soybean oil emulsions which were designed to mimic the commercially available parenteral fat emulsion, Intralipid ® . A high pH (minimum of pH 9, preferable pH of 11) was required for the drug laden emulsion to remain stable on storage and also to resist breaking under various stresses. Ageing of lecithin samples on storage was noted to result in degradation and a decrease in pH. We argue that this is the main reason for a similar decrease in pH for lecithin based emulsions and subsequent instability in drug laden emulsions. As expected, incorporation of the drug (halofantrine) resulted in lower stability. The (intensity weighted) particle size increased from 281nm for the drug free emulsion to 550nm following a loading of 1gL -1 of halofantrine, indicative of a lowering in stability and this was reflected in a shorter shelf life. Interestingly, incorporation of even higher concentrations of drug then resulted in better stability albeit never as stable as the drug free emulsion. We also report on unusual and complex surface tension behaviour for fresh lecithin where multiple critical concentration points were observed. Copyright © 2017 Elsevier B.V. All rights reserved.

The effect of pH and chloride concentration on the stability and antimicrobial activity of chlorine-based sanitizers.

PubMed

Waters, Brian W; Hung, Yen-Con

2014-04-01

Chlorinated water and electrolyzed oxidizing (EO) water solutions were made to compare the free chlorine stability and microbicidal efficacy of chlorine-containing solutions with different properties. Reduction of Escherichia coli O157:H7 was greatest in fresh samples (approximately 9.0 log CFU/mL reduction). Chlorine loss in "aged" samples (samples left in open bottles) was greatest (approximately 40 mg/L free chlorine loss in 24 h) in low pH (approximately 2.5) and high chloride (Cl(-) ) concentrations (greater than 150 mg/L). Reduction of E. coli O157:H7 was also negatively impacted (<1.0 log CFU/mL reduction) in aged samples with a low pH and high Cl(-) . Higher pH values (approximately 6.0) did not appear to have a significant effect on free chlorine loss or numbers of surviving microbial cells when fresh and aged samples were compared. This study found chloride levels in the chlorinated and EO water solutions had a reduced effect on both free chlorine stability and its microbicidal efficacy in the low pH solutions. Greater concentrations of chloride in pH 2.5 samples resulted in decreased free chlorine stability and lower microbicidal efficacy. © 2014 Institute of Food Technologists®

Optimization of protein solution by a novel experimental design method using thermodynamic properties.

PubMed

Kim, Nam Ah; An, In Bok; Lee, Sang Yeol; Park, Eun-Seok; Jeong, Seong Hoon

2012-09-01

In this study, the structural stability of hen egg white lysozyme in solution at various pH levels and in different types of buffers, including acetate, phosphate, histidine, and Tris, was investigated by means of differential scanning calorimetry (DSC). Reasonable pH values were selected from the buffer ranges and were analyzed statistically through design of experiment (DoE). Four factors were used to characterize the thermograms: calorimetric enthalpy (ΔH), temperature at maximum heat flux (T( m )), van't Hoff enthalpy (ΔH( V )), and apparent activation energy of protein solution (E(app)). It was possible to calculate E(app) through mathematical elaboration from the Lumry-Eyring model by changing the scan rate. The transition temperature of protein solution, T( m ), increased when the scan rate was faster. When comparing the T( m ), ΔH( V ), ΔH, and E(app) of lysozyme in various pH ranges and buffers with different priorities, lysozyme in acetate buffer at pH 4.767 (scenario 9) to pH 4.969 (scenario 11) exhibited the highest thermodynamic stability. Through this experiment, we found a significant difference in the thermal stability of lysozyme in various pH ranges and buffers and also a new approach to investigate the physical stability of protein by DoE.

Oxidative stability of soybean oil in oleosomes as affected by pH and iron.

PubMed

Kapchie, Virginie N; Yao, Linxing; Hauck, Catherine C; Wang, Tong; Murphy, Patricia A

2013-12-01

The oxidative stability of oil in soybean oleosomes, isolated using the Enzyme-Assisted Aqueous Extraction Process (EAEP), was evaluated. The effects of ferric chloride, at two concentration levels (100 and 500 μM), on lipid oxidation, was examined under pH 2 and 7. The peroxide value (PV) and thiobarbituric acid-reactive substance (TBARS) value of oil, in oleosome suspensions stored at 60 °C, were measured over a 12 day period. The presence of ferric chloride significantly (P<0.05) affected the oxidative stability of oil in the isolated oleosome, as measured by the PV and TBARS. Greater lipid oxidation occurred under an acidic pH. In the pH 7 samples, the positively charged transition metals were strongly attracted to the negatively charged droplets. However, the low ζ-potential and the high creaming rate at this pH, may have limited the oxidation. Freezing, freeze-drying or heating of oleosomes have an insignificant impact on the oxidative stability of oil in isolated soybean oleosomes. Manufacturers should be cautious when adding oleosomes as ingredients in food systems containing transition metal ions. Published by Elsevier Ltd.

One-year stability for a glucose/oxygen biofuel cell combined with pH reactivation of the laccase/carbon nanotube biocathode.

PubMed

Reuillard, Bertrand; Abreu, Caroline; Lalaoui, Noémie; Le Goff, Alan; Holzinger, Michael; Ondel, Olivier; Buret, Francois; Cosnier, Serge

2015-12-01

This study reports a mixed operational/storage stability of a MWCNT-based glucose biofuel cell (GBFC) over one year. The latter was examined by performing a one hour discharge every day during one month followed by several discharges over a period of 11 months. Under continuous discharge in physiological conditions (5 mM glucose, 37°, pH7), the GBFC exhibits a 25% power decrease after 1 h of operation. This decrease is mainly due to the deactivation of laccase biocathodes at neutral pH. Nevertheless, the biocathodes can be reversibly reactivated via storage in phosphate buffer (pH 5). Under these conditions, the GBFC finally exhibits 22% of its initial maximum power density after one year at intermittent reactivation/discharge cycles. Although both GBFC electrodes can exhibit one year stability, short-term experiments show that biocathodes are limited by hydroxide inhibition while long-term experiments indicate that bioanodes are likely limited by the stability of the GOx itself. While most of the GBFCs in the literature present stability in the range of several weeks, these results demonstrate the viability of a GBFC for industrial applications in a long period of time. Copyright © 2015 Elsevier B.V. All rights reserved.

Remote-loading labeling of liposomes with (99m)Tc-BMEDA and its stability evaluation: effects of lipid formulation and pH/chemical gradient.

PubMed

Li, Shihong; Goins, Beth; Phillips, William T; Bao, Ande

2011-03-01

Efficient, convenient, and stable radiolabeling plays a critical role for the monitoring of liposome behavior via either blood sampling, organ distribution, or noninvasive nuclear imaging. The direct labeling of liposome-carrying drugs without any prior modification undoubtedly is convenient and optimal for liposomal drug testing. In this article, we investigated the effect of various lipid formulations and pH/chemical gradients on the radiolabeling efficiency and entrapment stability of technetium-99m ((99m)Tc) remotely loaded into liposomes, using (99m)Tc-N,N-bis(2-mercaptoethyl)-N',N'-diethyl-ethylenediamine ((99m)Tc-BMEDA) complex. The tested liposomes either contained unsaturated lipid or possessed various surface charges. (99m)Tc could be efficiently loaded into various premanufactured liposomes containing either an ammonium sulfate pH, citrate pH, or glutathione (GSH) chemical gradient. (99m)Tc-entrapment stabilities of these liposomes in phosphate-buffered saline (PBS; pH 7.4) buffer at 25°C were mainly dependent on the pH/chemical gradient, but not lipid formulation. Stability sequence was ammonium sulfate pH-gradient>citrate pH-gradient>GSH-gradient. Stabilities of (99m)Tc-liposomes in 50% fetal bovine serum (FBS)/PBS (pH 7.4) buffer at 37°C are dependent on both lipid formulation and pH/chemical gradient. Specifically, (99m)Tc labeling of the ammonium sulfate pH-gradient liposomes were less stable in 50% FBS/PBS than in PBS, whereas noncationic liposomes with citrate pH- or GSH-gradient displayed higher stability, except that anionic citrate pH-gradient liposomes showed no stability difference in these two media. Cationic liposomes aggregated in 50% FBS/PBS, forming a new discrete fraction with larger particle sizes. These in vitro characterization results have indicated the optimism of using (99m)Tc-BMEDA for labeling pH/GSH gradient liposomes without the requirement of modifying lipid formulation for liposomal therapeutic-agent development.

Preparation and properties of immobilized pectinase onto the amphiphilic PS-b-PAA diblock copolymers.

PubMed

Lei, Zhongli; Bi, Shuxian

2007-01-30

Well-defined amphiphilic block copolymers poly(styrene-b-acrylic acid) (PS-b-PAA) with controlled block length were synthesized using atom transfer radical polymerization (ATRP). Pectinase enzyme was immobilized on the well-defined amphiphilic block copolymers PS-b-PAA. The carboxyl groups on the amphiphilic PS-b-PAA diblock copolymers present a very simple, mild, and time-saving process for enzyme immobilization. Various characteristics of immobilized pectinase such as the pH and temperature stability, thermal stability, and storage stability were valuated. Among them the pH optimum and temperature optimum of free and immobilized pectinase were found to be pH 6.0 and 65 degrees C.

A newly high alkaline lipase: an ideal choice for application in detergent formulations

PubMed Central

2011-01-01

Background Bacterial lipases received much attention for their substrate specificity and their ability to function in extreme environments (pH, temperature...). Many staphylococci produced lipases which were released into the culture medium. Reports of thermostable lipases from Staphylococcus sp. and active in alkaline conditions are not previously described. Results A newly soil-isolated Staphylococcus sp. strain ESW secretes an induced lipase in the culture medium. The effects of temperature, pH and various components in a detergent on the activity and stability of Staphylococcus sp. lipase (SL1) were studied in a preliminary evaluation for use in detergent formulation solutions. The enzyme was highly active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 12.0. The relative activity at pH 13.0 was about 60% of that obtained at pH 12.0. It exhibited maximal activity at 60°C. This novel lipase, showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40°C, and relative stability towards oxidizing agents. Additionally, the crude enzyme showed excellent stability and compatibility with various commercial solid and liquid detergents. Conclusions These properties added to the high activity in high alkaline pH make this novel lipase an ideal choice for application in detergent formulations. PMID:22123072

Stability of Hydrocortisone Preservative-Free Oral Solutions.

PubMed

Chappe, Julie; Osman, Névine; Cisternino, Salvatore; Fontan, Jean-Eudes; Schlatter, Joël

2015-01-01

The physical and chemical stability of a preservative-free oral solution of hydrocortisone succinate was studied at different pH values and storage temperatures. Oral solutions of hydrocortisone 1 mg/mL were prepared by dissolving hydrocortisone succinate powder in citrate buffers at pH 4.0, 5.5, and 6.5, or with sterile water (pH 7.4) stored in amber glass vials. Three identical samples of the formulations were prepared and stored under refrigeration (3-7°C), ambient temperature (20-22°C) and high temperature (29-31°C). A 200-μL sample was withdrawn from each of the 3 samples immediately after preparation and at 1, 7, 14, 21, and 35 days. Samples were assayed in duplicate using stability-indicating liquid chromatography. Stability was determined by evaluating the percentage of the initial concentration remaining at each time point; stability was defined as the retention of at least 90% of the initial concentration of hydrocortisone succinate. At least 92% of the initial hydrocortisone succinate concentration in solutions pH 5.5, 6.5, and 7.4 remained throughout the 14-day study period under refrigeration. There were no detectable changes in color, odor, or pH and no visible microbial growth in these samples. In other storage conditions, hydrocortisone succinate was rapidly degraded. The hydrocortisone succinate preservative-free oral solutions at pH 5.5, 6.5, or 7.4 are chemically stable when stored under refrigeration for at least 14 days. They provide flexible and convenient dosage forms without any preservatives for pediatric patients.

Physical Stability, Autoxidation, and Photosensitized Oxidation of ω-3 Oils in Nanoemulsions Prepared with Natural and Synthetic Surfactants.

PubMed

Uluata, Sibel; McClements, D Julian; Decker, Eric A

2015-10-28

The food industry is interested in the utilization of nanoemulsions stabilized by natural emulsifiers, but little research has been conducted to determine the oxidative stability of such emulsions. In this study, two natural (lecithin and quillaja saponin) and two synthetic (Tween 80 and sodium dodecyl sulfate) surfactants were used to fabricate omega-3 nanoemulsion using high pressure homogenization (microfluidization). Initially, all the nanoemulsions contained small (d from 45 to 89 nm) and anionic (ζ-potential from -8 to -65 mV) lipid droplets (pH 7). The effect of pH, ionic strength, and temperature on the physical stability of the nanoemulsion system was examined. Nanoemulsion stabilized with Tween 80, quillaja saponin, or sodium dodecyl sulfate (SDS) exhibited no major changes in particle size or visible creaming in the pH range of 3 to 8. All nanoemulsions were relatively stable to salt addition (0 to 500 mM NaCl, pH 7.0). Nanoemulsions stabilized with SDS and quillaja saponin were stable to heating (30 to 90 °C). The impact of surfactant type on lipid oxidation was determined in the presence and absence of the singlet oxygen photosensitizers, riboflavin, and rose bengal. Riboflavin and rose bengal accelerated lipid oxidation when compare to samples without photosensitizers. Lipid hydroperoxide formation followed the order Tween 80 > SDS > lecithin > quillaja saponin, and propanal formation followed the order lecithin > Tween 80 > SDS > quillaja saponin at 37 °C for autoxidation. The same order of oxidative stability was observed in the presence of photosensitized oxidation promoted by riboflavin. Quillaja saponin consistently produced the most oxidatively stable emulsions, which could be due to its high free radical scavenging capacity.

Emulsion properties of pork myofibrillar protein in combination with microbial transglutaminase and calcium alginate under various pH conditions.

PubMed

Hong, Geun Pyo; Min, Sang-Gi; Chin, Koo Bok

2012-01-01

In this study, the effects of microbial transglutaminase (MTG) and calcium alginate (CA) systems in combination with soybean oil on the emulsion properties of porcine myofibrillar protein (MP) were evaluated under various pH conditions. MTG was shown to improve emulsifying capacity and creaming stability, which increased with increasing pH values up to 6.5. The CA did not influence emulsifying capacity, but it improved the creaming stability of the MP-stabilized emulsions. Both MTG and CA enhanced the rheological properties, but their effects on the physical characteristics of the protein evidenced an opposite trend in relation to pH, i.e., the MTG system improved both the emulsion and gelling properties with increasing pH, whereas the CA system was effective when the pH was lowered. By combining the two MP gelling systems, a stable and pH-insensible emulsion could be produced. Copyright © 2011 Elsevier Ltd. All rights reserved.

Emulsifying properties of succinylated arabinoxylan-protein gum produced from corn ethanol residuals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiang, Zhouyang; Runge, Troy

This study investigated the possibilities of making valuable products from corn ethanol byproducts and providing the beverage industries more variety of high quality emulsifiers other than gum arabic. An arabinoxylan-protein gum (APG) was extracted from distillers' grains (DG), a low-value corn ethanol byproduct, and modified through acylation with succinic anhydride. The effects of pH and degree of substitution (DS) on the emulsifying properties of succinylated APG, referred to as SAPG, were investigated. Emulsion particle size and stability of APG and gum arabic were comparable at pH 3.5–6.5. Succinylation could enhance the emulsifying properties of APG. Compared to gum arabic, atmore » pH < 5, SAPG emulsions had larger particle size but comparable stability, whereas at pH > 5, SAPG had much smaller particle size and better stability than gum arabic. The results suggested that SAPG, compared to gum arabic, could be a comparable emulsifier at low pH values and a better emulsifier at neutral pH values.« less

Emulsifying properties of succinylated arabinoxylan-protein gum produced from corn ethanol residuals

DOE PAGES

Xiang, Zhouyang; Runge, Troy

2015-07-21

This study investigated the possibilities of making valuable products from corn ethanol byproducts and providing the beverage industries more variety of high quality emulsifiers other than gum arabic. An arabinoxylan-protein gum (APG) was extracted from distillers' grains (DG), a low-value corn ethanol byproduct, and modified through acylation with succinic anhydride. The effects of pH and degree of substitution (DS) on the emulsifying properties of succinylated APG, referred to as SAPG, were investigated. Emulsion particle size and stability of APG and gum arabic were comparable at pH 3.5–6.5. Succinylation could enhance the emulsifying properties of APG. Compared to gum arabic, atmore » pH < 5, SAPG emulsions had larger particle size but comparable stability, whereas at pH > 5, SAPG had much smaller particle size and better stability than gum arabic. The results suggested that SAPG, compared to gum arabic, could be a comparable emulsifier at low pH values and a better emulsifier at neutral pH values.« less

Physicochemical and microbiological stability studies of extemporaneous antihypertensive pediatric suspensions for hospital use.

PubMed

Mendes, Cassiana; Costa, Ana Paula; Oliveira, Paulo Renato; Tagliari, Monika Piazzon; Silva, Marcos Antônio Segatto

2013-01-01

Extemporaneous suspensions of the antihypertensive agents furosemide, spironolactone and hydrochlorothiazide for pediatric use have been prepared at University Hospital (Federal University of Santa Catarina - Brazil). The aim of this work was to investigate the physicochemical and microbiological stability of these suspensions over the estimated shelf-life period of seven days and, if necessary, to optimize the formulations by improving the chemical stability. The pediatric suspensions were prepared using drug raw material and were stored at 25 ± 2°C and 5 ± 3°C. Chemical stability was evaluated by HPLC assay of the suspensions for drug content. Physical stability was evaluated by sedimentation volume, redispersibility, particle size, and zeta potential. Viable bacterial and fungal contaminations were assessed according to the official compendium. Furosemide and spironolactone suspensions as prepared herein can be stored for 7 days. However, the hydrochlorothiazide suspension formulation at pH 6.5 demonstrated poor chemical stability and was optimized by adjusting the pH to 3.3 where the drug exhibited acceptable stability. The optimized formulation demonstrated to be stable over the required period of 7 days.

Rational design for the stability improvement of Armillariella tabescens β-mannanase MAN47 based on N-glycosylation modification.

PubMed

Hu, Weixiong; Liu, Xiaoyun; Li, Yufeng; Liu, Daling; Kuang, Zhihe; Qian, Chuiwen; Yao, Dongsheng

2017-02-01

β-Mannanase has been widely used in industries such as food and feed processing and thus has been a target enzyme for biotechnological development. In this study, we sought to improve the stability and protease resistance of a recombinant β-mannanase, MAN47 from Armillariella tabescens, through rationally designed N-glycosylation. Based on homology modeling, molecular docking, secondary structure analysis and glycosylation feasibility analysis, an enhanced aromatic sequon sequence was introduced into specific MAN47 loop regions to facilitate N-glycosylation. The mutant enzymes were expressed in Pichia pastoris SMD1168, and their thermal stability, pH stability, trypsin resistance and pepsin resistance were determined. Two mutant MAN47 enzymes, g-123 and g-347, were glycosylated as expected when expressed in yeast, and their thermal stability, pH stability, and protease resistance were significantly improved compared to the wild-type enzyme. An enzyme with multiple stability characterizations has broad prospects in practical applications, and the rational design N-glycosylation strategy may have applications in simultaneously improving several properties of other biotechnological targets. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of chitosan on the heat stability of whey protein solution as a function of pH.

PubMed

Zhao, Zhengtao; Xiao, Qian

2017-03-01

Chitosan was reported to interact with proteins through electrostatic interactions. Their interaction was influenced by pH, which was not fully characterized. Further research on the interactions between protein and chitosan at different pH and their influence on the thermal denaturation of proteins is necessary. In this research, the effect of chitosan on the heat stability of whey protein solution at pH 4.0-6.0 was studied. At pH 4.0, a small amount chitosan was able to prevent the heat-induced denaturation and aggregation of whey protein molecules. At higher pH values (5.5 and 6.0), whey proteins complexed with chitosan through electrostatic attraction. The formation of chitosan-whey protein complexes at pH 5.5 improved the heat stability of dispersions and no precipitation could be detected up to 20 days. The dispersion with a medium amount of chitosan (chitosan:whey protein 1:5) produced the most stable particles, which had an average radius of 135 ± 14 nm and a zeta potential value of 36 ± 1 mV. In contrast, at pH 6.0 only the dispersion with a high amount of chitosan (chitosan:whey protein 1:2) showed good shelf stability up to 20 days. It was possible to produce heat-stable whey protein beverages by regulating the interaction between chitosan and whey protein molecules. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Strategy for assessment of the colloidal and biological stability of H1N1 influenza A viruses.

PubMed

Hämmerling, Frank; Lorenz-Cristea, Oliver; Baumann, Pascal; Hubbuch, Jürgen

2017-01-30

Current influenza vaccines are mostly formulated as liquids which requires a continuous cold chain to maintain the stability of the antigen. For development of vaccines with an increased stability at ambient temperatures, manifold parameters and their influences on the colloidal stability and activity of the antigen have to be understood. This work presents a strategy to examine both, the colloidal stability and the remaining biological activity of H1N1 influenza viruses under various conditions after an incubation of 40 days. H1N1 phase diagrams were generated for several pH values and different initial H1N1 and NaCl concentrations. It was shown that the highest H1N1 recoveries were obtained for pH 6 and that moderate amounts of NaCl are favorable for increased recoveries. In contrast to colloidal stability, the highest remaining HA activity was observed at pH 9. The electrostatic and hydrophobic surface properties of H1N1 were investigated to reveal the mechanisms accounting for the decrease in stability. Secondly, the capability of virus precipitation by polyethylene glycol in combination with determination of surface hydrophobicity was proven to be useful as a predictive tool to rank stability under different conditions. This methodology enables the rapid assessment of aggregation propensity of H1N1 formulations and the influence on the activity of the virus particles and might become a standard tool during the development of vaccine formulations. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of pH on the stability of hemochromatosis factor E: a combined spectroscopic and molecular dynamics simulation-based study.

PubMed

Khan, Parvez; Shandilya, Ashutosh; Jayaram, B; Islam, Asimul; Ahmad, Faizan; Hassan, Md Imtaiyaz

2017-05-01

Hereditary hemochromatosis is an iron overburden condition, which is mainly governed by hereditary hemochromatosis factor E (HFE), a member of major histocompatibility complex class I. To understand the effect of pH on the structure and stability of HFE, we have cloned, expressed, and purified the HFE in the bacterial system and performed circular dichroism, fluorescence, and absorbance measurements at a wide pH range (pH 3.0-11.0). We found that HFE remains stable in the pH range 7.5-11.0 and gets completely acid denatured at low pH values. In this work, we also analyzed the contribution of salt bridges to the stability of HFE. We further performed molecular dynamics simulations for 80 ns at different pH values. An excellent agreement was observed between results from biophysical and MD simulation studies. At lower pH, HFE undergoes denaturation and may be driven toward a degradation pathway, such as ubiquitination. Hence, HFE is not available to bind again with transferrin receptor1 to negatively regulate iron homeostasis. Further we postulated that, might be low pH of cancerous cells helps them to meet their high iron requirement.

Mercury stabilization in chemically bonded phosphate ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagh, A. S.; Singh, D.; Jeong, S. Y.

2000-04-04

Mercury stabilization and solidification is a significant challenge for conventional stabilization technologies. This is because of the stringent regulatory limits on leaching of its stabilized products. In a conventional cement stabilization process, Hg is converted at high pH to its hydroxide, which is not a very insoluble compound; hence the preferred route for Hg sulfidation to convert it into insoluble cinnabar (HgS). Unfortunately, efficient formation of this compound is pH-dependent. At a high pH, one obtains a more soluble Hg sulfate, in a very low pH range, insufficient immobilization occurs because of the escape of hydrogen sulfide, while efficient formationmore » of HgS occurs only in a moderately acidic region. Thus, the pH range of 4 to 8 is where stabilization with Chemically Bonded Phosphate Ceramics (CBPC) is carried out. This paper discusses the authors experience on bench-scale stabilization of various US Department of Energy (DOE) waste streams containing Hg in the CBPC process. This process was developed to treat DOE's mixed waste streams. It is a room-temperature-setting process based on an acid-base reaction between magnesium oxide and monopotassium phosphate solution that forms a dense ceramic within hours. For Hg stabilization, addition of a small amount (< 1 wt.%) of Na{sub 2}S or K{sub 2}S is sufficient in the binder composition. Here the Toxicity Characteristic Leaching Procedure (TCLP) results on CBPC waste forms of surrogate waste streams representing secondary Hg containing wastes such as combustion residues and Delphi DETOX{trademark} residues are presented. The results show that although the current limit on leaching of Hg is 0.2 mg/L, the results from the CBPC waste forms are at least one order lower than this stringent limit. Encouraged by these results on surrogate wastes, they treated actual low-level Hg-containing mixed waste from their facility at Idaho. TCLP results on this waste are presented here. The efficient stabilization in all these cases is attributed to chemical immobilization as both a sulfide (cinnabar) and a phosphate, followed by its physical encapsulation in a dense matrix of the ceramic.« less

Chitosan based atorvastatin nanocrystals: effect of cationic charge on particle size, formulation stability, and in-vivo efficacy

PubMed Central

Kurakula, Mallesh; El-Helw, AM; Sobahi, Tariq R; Abdelaal, Magdy Y

2015-01-01

Cationic charged chitosan as stabilizer was evaluated in preparation of nanocrystals using probe sonication method. The influence of cationic charge densities of chitosan (low CSL, medium CSM, high CSH molecular weights) and Labrasol® in solubility enhancement and modifying the release was investigated, using atorvastatin (ATR) as poorly soluble model drug. Compared to CSM and CSH; low cationic charge of CSL acted as both electrostatic and steric stabilizer by significant size reduction to 394 nm with charge of 21.5 meV. Solubility of ATR-CSL increased to 60-fold relative to pure ATR and ATR-L. Nanocrystals were characterized for physiochemical properties. Scanning electron microscopy revealed scaffold-like structures with high surface area. X-ray powder diffractometry and differential scanning calorimetry revealed crystalline to slight amorphous state changes after cationic charge size reduction. Fourier transform-infrared spectra indicated no potent drug-excipient interactions. The enhanced dissolution profile of ATR-CSL indicates that sustained release was achieved compared with ATR-L and Lipitor®. Anti-hyperlipidemic performance was pH dependent where ATR-CSL exhibited 2.5-fold higher efficacy at pH 5 compared to pH 6 and Lipitor®. Stability studies indicated marked changes in size and charge for ATR-L compared to ATR-CSL exemplifying importance of the stabilizer. Therefore, nanocrystals developed with CSL as a stabilizer is a promising choice to enhance dissolution, stability, and in-vivo efficacy of major Biopharmaceutical Classification System II/IV drugs. PMID:25609947

Effects of the pH and Concentration on the Stability of Standard Solutions of Proteinogenic Amino Acid Mixtures.

PubMed

Kato, Megumi; Yamazaki, Taichi; Kato, Hisashi; Yamanaka, Noriko; Takatsu, Akiko; Ihara, Toshihide

2017-01-01

To prepare metrologically traceable amino acid mixed standard solutions, it is necessary to determine the stability of each amino acid present in the mixed solutions. In the present study, we prepared amino acid mixed solutions using certified reference standards of 17 proteinogenic amino acids, and examined the stability of each of these amino acids in 0.1 N HCl. We found that the concentration of glutamic acid decreased significantly during storage. LC/MS analysis indicated that the instability of glutamic acid was due to the partial degradation of glutamic acid to pyroglutamic acid in 0.1 N HCl. Using accelerated degradation tests, we investigated several solvent compositions to improve the stability of glutamic acid in amino acid mixed solution, and determined that the change of the pH by diluting the mixed solution improved the stability of glutamic acid.

Oxidative stability of egg and soy lecithin as affected by transition metal ions and pH in emulsion.

PubMed

Wang, Guang; Wang, Tong

2008-12-10

Oxidative stability of egg and soy lecithin in emulsion was evaluated with two transition metal ions, cupric and ferric ion, at two concentration levels (50 and 500 microM). The effect of pH on lipid oxidation was also examined under these two concentrations for each ion. Egg lecithin (EL) had similar peroxide value (PV) development pattern as soy lecithin (SL) when treated with cupric ion under both acidic and neutral pH. Acidic pH of 3 accelerated oxidation of both EL and SL, especially under high concentration of copper. When treated with ferric ion, EL oxidized much faster than SL did. EL had higher value of thiobarbituric acid-reactive substances (TBARS) than SL, possibly because of its higher content of long-chain polyunsaturated fatty acids (PUFA). Acidic pH accelerated TBARS development for both EL and SL, but EL had more significantly increased values. Cupric ion was more powerful than ferric in catalyzing oxidation of both EL and SL under both acidic and neutral pH conditions as measured by PV and TBARS. Linoleic acid may contribute to higher PV production, however, arachidonic acid and docosahexaenoic acid may have contributed more to TBARS production. Overall, SL showed better oxidative stability than EL under the experimental conditions. This study also suggests that using multiple methods is necessary in properly evaluating lipid oxidative stability.

The pH-dependent long-term stability of an amorphous manganese oxide in smelter-polluted soils: implication for chemical stabilization of metals and metalloids.

PubMed

Ettler, Vojtěch; Tomášová, Zdeňka; Komárek, Michael; Mihaljevič, Martin; Šebek, Ondřej; Michálková, Zuzana

2015-04-09

An amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH 3-8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH>5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that "labile" fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils. Copyright © 2015 Elsevier B.V. All rights reserved.

On the observation of the need for an unusually high concentration of cysteine and homocysteine to induce aggregation of polymer-stabilized gold nano particles

NASA Astrophysics Data System (ADS)

Radhakumary, C.; Sreenivasan, K.

2013-02-01

This study reports the interaction of chitosan-stabilized gold nanoparticles (CH-AuNPs) with cysteine (Cys) and homocysteine (Hcys) in aqueous media at pH 1.4. Since the polymer precipitates at higher pH, and the amino acids Cys and HCys are soluble at acidic pH, we kept the pH around 1.4 for stabilizing the particles. Zeta potential of CH-AuNPs was found to be positive and it is reasonable to assume that +ve Cys or Hcys at pH 1.4 will experience repulsive force. However, TEM images and absorption spectra indicated formation of aggregates including rod-like assembly. An interesting observation was the need for unusually high concentration of analytes (Cys and Hcys) to induce the assembly of CH-AuNPs. We also found time bound variation of the optical properties probably indicating the interaction is kinetically controlled and only a fraction of the analyte molecules having sufficient energy can bind onto the particles. We observed that at elevated temperature, the reaction was faster with a lower concentration of Cys or Hcys. These observations were supported by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory which describes the interparticle interaction and the colloidal stability in solution. Only molecules possessing enough energy to cross this force barrier can cause the aggregation. We also noted a time lag between Cys and Hcys to influence optical properties reflecting the possibility of using this simple approach to discriminate these two clinically relevant molecules. Our observation shows that simple sensing as well as generation of novel nanostructures could be manipulated by a judicious choice of conditions such as stabilizing agents, pH, etc.

pH-dependent stability of creatine ethyl ester: relevance to oral absorption.

PubMed

Gufford, Brandon T; Ezell, Edward L; Robinson, Dennis H; Miller, Donald W; Miller, Nicholas J; Gu, Xiaochen; Vennerstrom, Jonathan L

2013-09-01

Creatine ethyl ester hydrochloride (CEE) was synthesized as a prodrug of creatine (CRT) to improve aqueous solubility, gastrointestinal permeability, and ultimately the pharmacodynamics of CRT. We used high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (NMR) to characterize the pH-dependent stability of CEE in aqueous solution and compared the permeability of CEE to CRT and creatinine (CRN) across Caco-2 human epithelial cell monolayers and transdermal permeability across porcine skin. CEE was most stable in a strongly acidic condition (half-life = 570 hours at pH 1.0) where it undergoes ester hydrolysis to CRT and ethanol. At pH ≥ 1.0, CEE cyclizes to CRN with the logarithm of the first order rate constant increasing linearly with pH. Above pH 8.0 (half-life = 23 sec) the rate of degradation was too rapid to be determined. The rate of degradation of CEE in cell culture media and simulated intestinal fluid (SIF) was a function of pH and correlated well with the stability in aqueous buffered solutions. The permeability of CEE across Caco-2 monolayers and porcine skin was significantly greater than that of CRT or CRN. The stability of CEE in acidic media together with its improved permeability suggests that CEE has potential for improved oral absorption compared to CRT.

In situ chemical oxidation of BTEX and MTBE by ferrate: pH dependence and stability.

PubMed

Pepino Minetti, Roberto C; Macaño, Héctor R; Britch, Javier; Allende, M Carla

2017-02-15

Gasoline spills from underground storage tanks are a worldwide environmental problem. BTEX and MtBE are the compounds of gasoline that present the highest degree of migration due to their chemical properties, and are therefore able to impact groundwater reservoirs. In situ chemical oxidation (ISCO) is an emerging technology for groundwater remediation. Several compounds such as permanganate and hydrogen peroxide among others have been used as oxidants, a strong impact of pH on the relative stabilities and reduction potentials having been in each case determined. This paper presents a study of stability and degradation of BTEX and MtBE at different pH ranges of a novel oxidant for ISCO, potassium ferrate (K 2 FeO 4 ). To carry out this study, BTEX and MtBE solutions were prepared in different phosphate buffers (pH 5,8; 7; 9; 10 and 11) in concentration ratio of (FeO 4 -2 )/(BTEX+MtBE)=100:1. Each solution was analyzed at different times by gas chromatography with photoionization and tandem mass spectrometer detector. The results show a higher degree of degradation at pH 7 for Benzene and Toluene, and at pH 9 for Ethyl benzene and Xylenes, while MtBE proved recalcitrant to degradation by ferrate. The most favorable pH for stability of FeO 4 -2 solution was confirmed in 9-10. Copyright © 2016 Elsevier B.V. All rights reserved.

The effects of buffers and pH on the thermal stability, unfolding and substrate binding of RecA.

PubMed

Metrick, Michael A; Temple, Joshua E; MacDonald, Gina

2013-12-31

The Escherichia coli protein RecA is responsible for catalysis of the strand transfer reaction used in DNA repair and recombination. Previous studies in our lab have shown that high concentrations of salts stabilize RecA in a reverse-anionic Hofmeister series. Here we investigate how changes in pH and buffer alter the thermal unfolding and cofactor binding. RecA in 20mM HEPES, MES, Tris and phosphate buffers was studied in the pH range from 6.5 to 8.5 using circular dichroism (CD), infrared (IR) and fluorescence spectroscopies. The results show all of the buffers studied stabilize RecA up to 50°C above the Tris melting temperature and influence RecA's ability to nucleate on double-stranded DNA. Infrared and CD spectra of RecA in the different buffers do not show that secondary structural changes are associated with increased stability or decreased ability to nucleate on dsDNA. These results suggest the differences in stability arise from decreasing positive charge and/or buffer interactions. © 2013. Published by Elsevier B.V. All rights reserved.

Effect of various halide salts on the incompatibility of cyanocobalamin and ascorbic acid in aqueous solution.

PubMed

Ichikawa, Makoto; Ide, Nagatoshi; Shiraishi, Sumihiro; Ono, Kazuhisa

2005-06-01

Combination of cyanocobalamin (VB12) and ascorbic acid (VC) has been widely seen in pharmaceutical products and dietary supplements. However, VB12 has been reported that its behavior in stability in aqueous solution is quite different when VC is mixed. In the present study, we examined the stabilities of these vitamins in acetate buffer (pH 4.8) using high performance liquid chromatography. Degradation of VB12 was not observed in the absence of VC in the buffer. However, when VC was mixed in the VB12 solution, VB12 concentrations decreased in accordance with VC degradation. VB12 and VC degradations were inhibited by adding sodium halides to acetate buffer at pH 4.8. These stabilization effects were also observed in the range from pH 3.5 to 5.3 and by adding potassium, magnesium, and calcium halides. Furthermore, our data demonstrated that increases in the halide anion concentrations and atomic number (Cl-

Molecular Dynamics Driven Design of pH-Stabilized Mutants of MNEI, a Sweet Protein

PubMed Central

Picone, Delia

2016-01-01

MNEI is a single chain derivative of monellin, a plant protein that can interact with the human sweet taste receptor, being therefore perceived as sweet. This unusual physiological activity makes MNEI a potential template for the design of new sugar replacers for the food and beverage industry. Unfortunately, applications of MNEI have been so far limited by its intrinsic sensitivity to some pH and temperature conditions, which could occur in industrial processes. Changes in physical parameters can, in fact, lead to irreversible protein denaturation, as well as aggregation and precipitation. It has been previously shown that the correlation between pH and stability in MNEI derives from the presence of a single glutamic residue in a hydrophobic pocket of the protein. We have used molecular dynamics to study the consequences, at the atomic level, of the protonation state of such residue and have identified the network of intramolecular interactions responsible for MNEI stability at acidic pH. Based on this information, we have designed a pH-independent, stabilized mutant of MNEI and confirmed its increased stability by both molecular modeling and experimental techniques. PMID:27340829

Reformation of casein particles from alkaline-disrupted casein micelles.

PubMed

Huppertz, Thom; Vaia, Betsy; Smiddy, Mary A

2008-02-01

In this study, the properties of casein particles reformed from alkaline disrupted casein micelles were studied. For this purpose, micelles were disrupted completely by increasing milk pH to 10.0, and subsequently reformed by decreasing milk pH to 6.6. Reformed casein particles were smaller than native micelles and had a slightly lower zeta-potential. Levels of ionic and serum calcium, as well as rennet coagulation time did not differ between milk containing native micelles or reformed casein particles. Ethanol stability and heat stability, >pH 7.0, were lower for reformed casein particles than native micelles. Differences in heat stability, ethanol stability and zeta-potential can be explained in terms of the influence of increased concentrations of sodium and chloride ions in milk containing reformed casein particles. Hence, these results indicate that, if performed in a controlled manner, casein particles with properties closely similar to those of native micelles can be reformed from alkaline disrupted casein micelles.

Yeast mannoproteins improve thermal stability of anthocyanins at pH 7.0.

PubMed

Wu, Jine; Guan, Yongguang; Zhong, Qixin

2015-04-01

Anthocyanins are food colourants with strong antioxidant activities, but poor thermal stability limits their application in neutral foods. In the present study, impacts of yeast mannoproteins on the thermal stability of anthocyanins were studied at pH 7.0. The degradation of anthocyanins at 80 and 126 °C followed first order kinetics, and the addition of mannoproteins reduced the degradation rate constant and increased the half-life by 4 to 5-fold. After heating at 80 and 126 °C for 30 min, mannoproteins improved the colour stability of anthocyanins by 4 to 5-fold and maintained the antioxidant capacity of anthocyanins. Visible light absorption, fluorescence spectroscopy, and zeta-potential results suggest that anthocyanins bound with the protein moiety of mannoproteins by hydrophobic interactions, and that the inclusion of anthocyanins in complexes effectively reduced the thermal degradation at pH 7.0. Therefore, mannoproteins may expand the application of anthocyanins as natural colours or functional ingredients. Copyright © 2014 Elsevier Ltd. All rights reserved.

Study on the stability control strategy of Triphala solution based on the balance of physical stability and chemical stabilities.

PubMed

Huang, Hao-Zhou; Zhao, Sheng-Yu; Ke, Xiu-Mei; Lin, Jun-Zhi; Huang, Shu-Sen; Xu, Run-Chun; Ma, Hong-Yan; Zhang, Yi; Han, Li; Zhang, Ding-Kun

2018-06-04

Triphala is a well-known prescription in Indian Ayurveda and TCM medicine for its great effect on gingivitis and hyperlipidemia. However, its solution is unstable for the containing of excessive polyphenol, leading to the production of sediment in the short term and the decrease of efficacy. Based on the analysis of sediment formation, a novel control strategy is proposed. To conduct the analysis, the sediment formation was recorded for a consecutive five days. The changes in the composition of the supernatant and the sediment were studied by the HPLC profile analysis. The main components of the sediment were identified as corilagin, ellagic acid and gallic acid, and the amount of ellagic acid sediment increased with the storage time. Then, with a series of pH status adjustments of the Triphala solution, the physical and chemical stabilities were acquired by Turbiscan and HPLC respectively. The results showed that as the pH value increased, so did the physical stability, but the particle size and TSI of the association decreased. While the fingerprint of chemical profile similarity decreased, so did the chemical stability. Combining physical and chemical stability parameters, an equilibrium point was found out. When the pH value was adjusted to 5.0, both the physical and chemical stabilities were better: the verification test showed that the sedimentation inhibition rates on the 3rd, 5th,10th and15th days were 41%, 55%, 41%, and 23%, respectively. This manuscript provided a new control strategy that will pique pharmaceutical and food development engineers' interest and trigger research ideas controlling the quality of decoction. Copyright © 2018 Elsevier B.V. All rights reserved.

The effect of simulated acid rain on the stabilization of cadmium in contaminated agricultural soils treated with stabilizing agents.

PubMed

Zhu, Hao; Wu, Chunfa; Wang, Jun; Zhang, Xumei

2018-04-16

Stabilization technology is one of widely used remediation technologies for cadmium (Cd)-contaminated agricultural soils, but stabilized Cd in soil may be activated again when external conditions such as acid rain occurred. Therefore, it is necessary to study the effect of acid rain on the performance of different stabilizing agents on Cd-polluted agriculture soils. In this study, Cd-contaminated soils were treated with mono-calcium phosphate (MCP), mono-ammonium phosphate (MAP), and artificial zeolite (AZ) respectively and incubated 3 months. These treatments were followed by two types of simulated acid rain (sulfuric acid rain and mixed acid rain) with three levels of acidity (pH = 3.0, 4.0, and 5.6). The chemical forms of Cd in the soils were determined by Tessier's sequential extraction procedure, and the leaching toxicities of Cd in the soils were assessed by toxicity characteristic leaching procedure (TCLP). The results show that the three stabilizing agents could decrease the mobility of Cd in soil to some degree with or without simulated acid rain (SAR) treatment. The stabilization performances followed the order of AZ < MAP < MCP. Acid rain soaking promoted the activation of Cd in stabilized soil, and both anion composition and pH of acid rain were two important factors that influenced the stabilization effect of Cd.

Potential phosphorus eutrophication mitigation strategy: Biochar carbon composition, thermal stability and pH influence phosphorus sorption

Treesearch

L.W. Ngatia; Y.P. Hsieh; D. Nemours; R. Fu; R.W. Taylor

2017-01-01

Phosphorus (P) eutrophication is a major pollution problem globally, with unprecedented amount of P emanating from agricultural sources. But little is known about the optimization of soil-biochar P sorption capacity. The study objective was to determine how biochar feedstocks and pyrolysis conditions influences carbon (C) thermal stability, C composition and pH and in...

Aggregation and Stability of Reduced Graphene Oxide: Complex Roles of Divalent Cations, pH, and Natural Organic Matter

EPA Science Inventory

The aggregation and stability of graphene oxide (GO) and three successively reduced GO (rGO) nanomaterials were investigated. Reduced GO species were partially reduced GO (rGO-1h), intermediately reduced GO (rGO-2h), and fully reduced GO (rGO-5h). Specifically, influence of pH, i...

Amaranth proteins foaming properties: Film rheology and foam stability - Part 2.

PubMed

Bolontrade, Agustín J; Scilingo, Adriana A; Añón, María C

2016-05-01

In this work the influence of pH and ionic strength on the stability of foams prepared with amaranth protein isolate was analyzed. The behaviour observed was related to the physico-chemical and structural changes undergone by amaranth protein as a result of those treatments. The results obtained show that foams prepared at acidic pH were more stable than the corresponding to alkaline pH. At pH 2.0 the foams presented higher times and more volumes of drainage. This behaviour is consistent with the characteristics of the interfacial film, which showed a higher viscoelasticity and a greater flexibility at acidic pH than alkaline pH value, which in turn increased by increasing the concentration of proteins in the foaming solution. It is also important to note that the presence of insoluble protein is not necessarily detrimental to the properties of the foam. Detected changes in the characteristics of the interfacial film as in the foam stability have been attributed to the increased unfolding, greater flexibility and net charge of amaranth proteins at acidic conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

Gum arabic and Fe²⁺ synergistically improve the heat and acid stability of norbixin at pH 3.0-5.0.

PubMed

Guan, Yongguang; Zhong, Qixin

2014-12-31

Thermal and acid stabilities of norbixin are challenges for its application as a food colorant. In this work, gum arabic and Fe(2+) were studied for the possibility to improve the thermal and acid stabilities of norbixin. Norbixin was dissolved at 0.004% w/v in deionized water with and without 0.2% w/v gum arabic and/or 0.15 mM ferrous chloride, adjusted to pH 3.0-5.0, and heated at 90 or 126 °C for 30 min. Before heating, norbixin precipitated at pH 3.0-4.0, which was prevented by gum arabic. The thermal stability of norbixin was improved by the combination of gum arabic and Fe(2+). Fluorescence analyses indicated the complex formation between norbixin and gum arabic with and without Fe(2+). Particle size and atomic force microscopy results suggested Fe(2+) and gum arabic synergistically prevented the aggregation of norbixin at acidic pH and during heating. It was hypothesized that the core of gum arabic-norbixin complexes was strengthened by Fe(2+) to enable the synergy.

Validation of enhanced stabilization of municipal solid waste under controlled leachate recirculation using FTIR and XRD.

PubMed

Sethi, Sapna; Kothiyal, N C; Nema, Arvind K

2012-07-01

Leachate recirculation at neutral PH accompanied with buffer/nutrients addition has been used successfully in earlier stabilization of municipal solid waste in bioreactor landfills. In the present study, efforts were made to enhance the stabilization rate of municipal solid waste (MSW) and organic solid waste (OSW) in simulated landfill bioreactors by controlling the pH of recirculated leachate towards slightly alkaline side in absence of additional buffer and nutrients addition. Enhanced stabilization in waste samples was monitored with the help of analytical tools like Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). Predominance of bands assigned to inorganic compounds and comparatively lower intensities of bands for organic compounds in the FTIR spectra of waste samples degraded with leachate recirculation under controlled pH confirmed higher rate of biodegradation and mineralization of waste than the samples degraded without controlled leachate recirculation. XRD spectra also confirmed to a greater extent of mineralization in the waste samples degraded under leachate recirculation with controlled pH. Comparison of XRD spectra of two types of wastes pointed out higher degree of mineralization in organic solid waste as compared to municipal solid waste.

Influence of surface charge, binding site residues and glycosylation on Thielavia terrestris cutinase biochemical characteristics

PubMed Central

Shirke, Abhijit N.; Basore, Danielle; Holton, Samantha; Su, An; Baugh, Evan; Butterfoss, Glenn L.; Makhatadze, George

2016-01-01

Cutinases are esterases of industrial importance for applications in recycling and surface modification of polyesters. The cutinase from Thielavia terrestris (TtC) is distinct in terms of its ability to retain its stability and activity in acidic pH. Stability and activity in acidic pHs are desirable for esterases as the pH of the reaction tends to go down with the generation of acid. The pH stability and activity are governed by the charged state of the residues involved in catalysis or in substrate binding. In this study, we performed the detailed structural and biochemical characterization of TtC coupled with surface charge analysis to understand its acidic tolerance. The stability of TtC in acidic pH was rationalized by evaluating the contribution of charge interactions to the Gibbs free energy of unfolding at varying pHs. The activity of TtC was found to be limited by substrate binding affinity, which is a function of the surface charge. Additionally, the presence of glycosylation affects the biochemical characteristics of TtC owing to steric interactions with residues involved in substrate binding. PMID:26758295

Stability of self-assembled polymer films investigated by optical laser reflectometry.

PubMed

Dejeu, Jérôme; Diziain, Séverine; Dange, Catherine; Membrey, François; Charraut, Daniel; Foissy, Alain

2008-04-01

We studied the influence of post-treatment rinsing after the formation of self-assembled polyelectrolyte films made with the weak base poly(allylamine hydrochloride) (PAH) and the strong acid poly(styrene sulfonate) (PSS). The stability of the film was studied using optical fixed-angle laser reflectometry to measure the release of polymeric material and AFM experiments to reveal the change of morphology and thickness. We found that the polymer films were stable upon rinsing when the pH was the same in the solution as that used in the buildup (pH 9). The films released most of the polymeric material when rinsed at higher pH values, but a layer remained that corresponded to a PAH monolayer directly bound with the silica surface. Films containing at least four bilayers were stable upon rinsing at lower pH values, but the stability of thinner films depended on the type of the last polymer deposited. They were stable in the case of PSS as an outermost deposit, but they released a large part of their material in the case of PAH. The stability results were determined using a simple model of the step-by-step assembly of the polymer film described formerly.

The immobilization of lipase on PVDF-co-HFP membrane

NASA Astrophysics Data System (ADS)

Kayhan, Naciye; Eyüpoǧlu, Volkan; Adem, Şevki

2016-04-01

Lipase is an enzyme having a lot of different industrial applications such as biodiesel production, biopolymer synthesis, enantiopure pharmaceutical productions, agrochemicals, etc. Its immobilized form on different substances is more conventional and useful than its free form. Supporting material was prepared using PVDF-co-HFP in laboratory conditions and attached 1,4-diaminobutane (DA) and epichlorohydrin (EPI) ligands to the membrane to immobilize lipase enzyme. The immobilization conditions such as enzyme amount, pH, the concentration of salt, thermal stability and activity were stabilized for our experimental setup. Then, biochemical characterizations were performed on immobilized lipase PVDF-co-HFP regarding optimal pH activity, temperature and thermal stability. Also, the desorption ratios of immobilized enzyme in two different pathway were investigated to confirm immobilization stability for 24 hours.

Effect of pH, Mg2+, CO2 and Mercurials on the Circular Dichroism, Thermal Stability and Light Scattering of Ribulose 1,5-Bisphosphate Carboxylases from Alfalfa, Spinach and Tobacco

PubMed Central

Tomimatsu, Yoshio; Donovan, John W.

1981-01-01

Circular dichroism, differential scanning calorimetry and light-scattering measurements of ribulose 1,5-bisphosphate carboxylase (E.C. 4.1.1.39) from alfalfa, spinach and tobacco show: a) The conformation and thermal stability of the native carboxylases are sensitive to changes in pH and to activation of the enzyme with Mg2+ and CO2. The helical content, denaturation temperature (Td) and specific enthalpy of denaturation (Δq) decreased with increase in pH. Addition of Mg2+ and CO2 at pH 9 increased Td by 4 to 5 C; at pH 7.5 the changes in Td were smaller. b) Addition of mercurials produced changes in conformation and thermal stability. The decrease in helical content of the enzymes with increase in pH was enhanced by the addition of p-chloromercuribenzoate. At pH 9, addition of p-chloromercuribenzoate or of 1-(3-(chloromercuri)-2-methoxypropyl)urea decreased Td by 11.4 to 20.2 C and Δq by 2.1 to 2.8 calories per gram. c) The spinach carboxylase undergoes the largest and the tobacco the smallest changes in conformation and thermal stability upon change in pH or treatment with mercurials. d) The calorimetric data suggest that the large and small subunits are heat denatured independently but at the same temperature. e) Light scattering measurements at pH 9 of p-chloromercuribenzoate treated tobacco enzyme showed that there is no dissociation into subunits upon heating to temperatures greater than Td. A `ball and string' model for the carboxylase molecule is proposed to reconcile independence of subunit denaturation with apparent strong interactions between subunits. PMID:16662003

Stability of Adrenaline in Irrigating Solution for Intraocular Surgery.

PubMed

Shibata, Yuuka; Kimura, Yasuhiro; Taogoshi, Takanori; Matsuo, Hiroaki; Kihira, Kenji

2016-01-01

Intraocular irrigating solution containing 1 µg/mL adrenaline is widely used during cataract surgery to maintain pupil dilation. Prepared intraocular irrigating solutions are recommended for use within 6 h. After the irrigating solution is admistered for dilution, the adrenaline may become oxidized, and this may result in a decrease in its biological activity. However, the stability of adrenaline in intraocular irrigating solution is not fully understood. The aim of this study was to evaluate the stability of adrenaline in clinically used irrigating solutions of varying pH. Six hours after mixing, the adrenaline percentages remaining were 90.6%±3.7 (pH 7.2), 91.1%±2.2 (pH 7.5), and 65.2%±2.8 (pH 8.0) of the initial concentration. One hour after mixing, the percentages remaining were 97.6%±2.0 (pH 7.2), 97.4%±2.7 (pH 7.5), and 95.6%±3.3 (pH 8.0). The degradation was especially remarkable and time dependent in the solution at pH 8.0. These results indicate that the concentration of adrenaline is decreased after preparation. Moreover, we investigated the influence of sodium bisulfite on adrenaline stability in irrigating solution. The percentage adrenaline remaining at 6 h after mixing in irrigating solution (pH 8.0) containing sodium bisulfite at 0.5 µg/mL (concentration in irrigating solution) or at 500 µg/mL (concentration in the undiluted adrenaline preparation) were 57.5 and 97.3%, respectively. Therefore, the low concentration of sodium bisulfite in the irrigating solution may be a cause of the adrenaline loss. In conclusion, intraocular irrigation solution with adrenaline should be prepared just prior to its use in surgery.

Stability of nTiO2 particles and their attachment to sand: Effects of humic acid at different pH.

PubMed

Wu, Yang; Cheng, Tao

2016-01-15

The fate and transport of nano-scale or micro-scale titanium dioxide particles (nTiO2) in subsurface environments are strongly influenced by the stability of nTiO2 and their attachment to sediment grains. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the stability and transport of negatively-charged colloids, may influence nTiO2 in different manners. The objective of this study is to investigate the effects of pH and humic acid (HA) on the stability and attachment of nTiO2 to sand at HA concentrations that are relevant to typical groundwater conditions, so that mechanisms that control nTiO2 immobilization and transport in natural systems can be elucidated. Stability and attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand are experimentally measured under a range of HA concentrations at pH5 and 9. Results show that at pH5, negatively-charged HA strongly adsorbs to positively-charged nTiO2 and Fe oxyhydroxide, which, at low HA concentrations, partially neutralizes the positive charges on nTiO2 and Fe oxyhydroxide, and therefore decreases the repulsive electrostatic forces between the surfaces, resulting in nTiO2 aggregation and attachment. At high HA concentrations, adsorbed HA reverses the surface charges of nTiO2 and Fe oxyhydroxide, and makes nTiO2 and Fe oxyhydroxide strongly negatively charged, resulting in stable nTiO2 suspension and low nTiO2 attachment. At pH9, HA, nTiO2, and Fe oxyhydroxide are all negatively charged, and HA adsorption is low and does not have a strong impact on the stability and attachment of nTiO2. Overall, this study shows that changes in surface charges of nTiO2 and Fe oxyhydroxide coating caused by HA adsorption is a key factor that influences the stability and attachment of nTiO2. Copyright © 2015 Elsevier B.V. All rights reserved.

Colour and stability assessment of blue ferric anthocyanin chelates in liquid pectin-stabilised model systems.

PubMed

Buchweitz, M; Brauch, J; Carle, R; Kammerer, D R

2013-06-01

The formation of blue coloured ferric anthocyanin chelates and their colour stability during storage and thermal treatment were monitored in a pH range relevant to food (3.6-5.0). Liquid model systems were composed of different types of Citrus pectins, juices (J) and the respective phenolic extracts (E) from elderberry (EB), black currant (BC), red cabbage (RC) and purple carrot (PC) in the presence of ferric ions. For EB, BC and PC, pure blue colours devoid of a violet tint were exclusively observed for the phenolic extracts and at pH values ≥ 4.5 in model systems containing high methoxylated and amidated pectins, respectively. Colour and its stability strongly depended on the amount of ferric ions and the plant source; however, colour decay could generally be described as a pseudo-first-order kinetics. Despite optimal colour hues for RC-E and RC-J, storage and heat stabilities were poor. Highest colour intensities and best stabilities were observed for model systems containing PC-E at a molar anthocyanin:ferric ion ratio of 1:2. Ascorbic and lactic acids interfered with ferric ions, thus significantly affecting blue colour evolution and stability. Colour loss strongly depended on heat exposure with activation energies ranging between 60.5 and 78.4 kJ/mol. The comprehensive evaluation of the interrelationship of pigment source, pH conditions and pectin type on chelate formation and stability demonstrated that ferric anthocyanin chelates are promising natural blue food colourants. Copyright © 2012 Elsevier Ltd. All rights reserved.

Correlating the Impact of Well-Defined Oligosaccharide Structures on Physical Stability Profiles of IgG1-Fc Glycoforms.

PubMed

More, Apurva S; Toprani, Vishal M; Okbazghi, Solomon Z; Kim, Jae H; Joshi, Sangeeta B; Middaugh, C Russell; Tolbert, Thomas J; Volkin, David B

2016-02-01

As part of a series of articles in this special issue describing 4 well-defined IgG1-Fc glycoforms as a model system for biosimilarity analysis (high mannose-Fc, Man5-Fc, GlcNAc-Fc and N297Q-Fc aglycosylated), the focus of this work is comparisons of their physical properties. A trend of decreasing apparent solubility (thermodynamic activity) by polyethylene glycol precipitation (pH 4.5, 6.0) and lower conformational stability by differential scanning calorimetry (pH 4.5) was observed with reducing size of the N297-linked oligosaccharide structures. Using multiple high-throughput biophysical techniques, the physical stability of the Fc glycoproteins was then measured in 2 formulations (NaCl and sucrose) across a wide range of temperatures (10°C-90°C) and pH (4.0-7.5) conditions. The data sets were used to construct 3-index empirical phase diagrams and radar charts to visualize the regions of protein structural stability. Each glycoform showed improved stability in the sucrose (vs. salt) formulation. The HM-Fc and Man5-Fc displayed the highest relative stability, followed by GlcNAc-Fc, with N297Q-Fc being the least stable. Thus, the overall physical stability profiles of the 4 IgG1-Fc glycoforms also show a correlation with oligosaccharide structure. These data sets are used to develop a mathematical model for biosimilarity analysis (as described in a companion article by Kim et al. in this issue). Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Effect of Al on stability of DHMS up to the uppermost lower mantle

NASA Astrophysics Data System (ADS)

Xu, C.; Inoue, T.

2017-12-01

Water plays an important role on Earth. It influences the physical and chemical property of minerals and melts, which further effects the evolution of the Earth. A series of dense hydrous magnesium silicate (DHMS) phases such as phase A (PhA), phase E (PhE), superhydrous phase B (SUB) and phase D (PhD) have been suggested as potential water carriers to transition zone and even to the lower mantle under the conditions present in the cold subducting slabs [e.g. Kawamoto, 2004; Komabayashi and Omori, 2006]. Because of its importance, the DHMS have been widely studied by using different starting materials in MgO-SiO2-H2O system. Recently, the newly reported Al-PhD is stable at temperatures up to 2,000 °C at 26 GPa, which indicates aluminum increases stability regions of DHMS [e.g. Pamato et al., 2015]. To systematically study the effect of Al on the stability of hydrous phases, we use Kawai-type high pressure apparatus to investigate nature clinochlore, which contains about 15 wt% H2O and about 14 wt% Al2O3. The Al-bearing hydrous PhE, SUB and PhD were observed with P-T increasing. Following the P-T path of cold subduction, the phase assemblage PhE + PhD is stable at 14-23 GPa, and even a trace of PhE is detected at 1150°C and 25 GPa coexisting with PhD. The phase SUB is stable between 16-22 GPa coexisting with PhE + PhD. Following the P-T path of hot subduction, the phase assemblage PhE + Gt is observed at 14-18 GPa coexisting with fluid or melt. The phase assemblage SUB + PhD is stable at 18-25 GPa, which may extend to higher pressures and temperatures. Therefore, it is obvious that Al enhances the stabilities of these three hydrous minerals, which are stable even in the hot subducting conditions. On the other hand, the Al substitution mechanism in PhE, SUB and PhD were clarified according to chemical compositional relationship between Mg, Si, Al. This shows that they can hold a significant amount of H (water) in their structure. Our results may indicate that the wide stabilities of Al-bearing DHMS increase the chance of water transportation to deeper mantle after antigorite (serpentine) decomposition at the shallow region of the subduction zone.

Proximate composition of Karkadeh (Hibiscus sabdariffa) seeds and some functional properties of seed protein isolate as influenced by pH and NaCl.

PubMed

Salah, E O Mahgoub; Hayat, Z E Elbashir

2009-05-01

Seeds of an inbred line (B-11-90) of Karkadeh (Hibiscus sabdariffa) were investigated for their proximate composition (AOAC methods), nitrogen solubility and protein isolate (Karkadeh seed protein isolates [KSPI]) functional properties (standard methods). The fat and protein contents of the seeds were 22.43% and 32.46%, respectively. Nitrogen solubility was good in both water and 1.0 M NaCl at alkaline pH rather than at acidic pH, with better solubility at higher pH levels in water than in 1.0 M NaCl. The functional properties of the KSPI were as follows: water absorption capacity, 181 ml/100 g; fat absorption capacity, 110 ml/100 g; bulk density, 0.77 g/ml; and apparent viscosity (at 20 degrees C), 13.42 cps. KSPI showed a maximum foaming capacity at pH 12 and 1.6 M NaCl, a maximum emulsification capacity at pH 11 and 1.8 M NaCl, and a weaker foam stability at neutral pH than at acidic or alkaline pH, with a better foam stability at alkaline pH. The foam stability was considerably improved by treatment with 1.6 M NaCl.

Conformational stability of apoflavodoxin.

PubMed Central

Genzor, C. G.; Beldarraín, A.; Gómez-Moreno, C.; López-Lacomba, J. L.; Cortijo, M.; Sancho, J.

1996-01-01

Flavodoxins are alpha/beta proteins that mediate electron transfer reactions. The conformational stability of apoflavodoxin from Anaboena PCC 7119 has been studied by calorimetry and urea denaturation as a function of pH and ionic strength. At pH > 12, the protein is unfolded. Between pH 11 and pH 6, the apoprotein is folded properly as judged from near-ultraviolet (UV) circular dichroism (CD) and high-field 1H NMR spectra. In this pH interval, apoflavodoxin is a monomer and its unfolding by urea or temperature follows a simple two-state mechanism. The specific heat capacity of unfolding for this native conformation is unusually low. Near its isoelectric point (3.9), the protein is highly insoluble. At lower pH values (pH 3.5-2.0), apoflavodoxin adopts a conformation with the properties of a molten globule. Although apoflavodoxin at pH 2 unfolds cooperatively with urea in a reversible fashion and the fluorescence and far-UV CD unfolding curves coincide, the transition midpoint depends on the concentration of protein, ruling out a simple two-state process at acidic pH. Apoflavodoxin constitutes a promising system for the analysis of the stability and folding of alpha/beta proteins and for the study of the interaction between apoflavoproteins and their corresponding redox cofactors. PMID:8819170

Heavy metal stabilization in contaminated road-derived sediments.

PubMed

Rijkenberg, Micha J A; Depree, Craig V

2010-02-01

There is increasing interest in the stabilization of heavy metals in road-derived sediments (RDS), to enable environmentally responsible reuse applications and circumvent the need for costly landfill disposal. To reduce the mobility of heavy metals (i.e. Cu, Pb and Zn) the effectiveness of amendments using phosphate, compost and fly ash addition were investigated using batch leaching experiments. In general, phosphate amendments of RDS were found to be ineffective at stabilizing heavy metals, despite being used successfully in soils. Phosphate amendment resulted in enhanced concentrations of dissolved organic carbon (DOC), which increased the solubilisation of heavy metals via complexation. Amendment with humified organic matter (compost) successfully stabilized Cu and Pb in high DOC leaching RDS with an optimum loading of 15-20% (w/w). Compost, however, was ineffective at stabilizing Zn. Increasing the pH by amending RDS/compost blends with 2.5-15% (w/w) coal fly ash resulted in the stabilization of Zn, Cu and Pb. However, above a pH of approximately 7.5 and 8 enhanced leaching of organic matter resulted in an increase in leached Cu and Pb, respectively. Accordingly, the optimum level of fly ash amendment for the RDS/compost blends was estimated to be ca. 10%. Boosted regression trees analysis (BRT) of the data revealed that DOC accounted for 56% and 65% of the Cu and Pb leaching, respectively, whereas pH only accounted for ca. 18% of Cu and Pb leaching. RDS sample characteristics (i.e. metal concentrations, size fractionation and organic matter content) were more important at reconciling the leaching concentrations of copper Cu (27%) than Pb (16%). The most important parameter explaining Zn leaching was pH. Overall, the choice of a suitable stabilization agent/s depends on the composition of RDS with respect to the amount of organic matter present, and the sorption chemistry of the heavy metal of interest. Copyright 2009 Elsevier B.V. All rights reserved.

Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose

PubMed Central

2014-01-01

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed ~ 36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 μg/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7 ± 0.1. The maximum removal efficiency of both arsenic species was obtained at pH = 5 ± 0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

Influence of formulation properties on chemical stability of captopril in aqueous preparations.

PubMed

Kristensen, S; Lao, Y E; Brustugun, J; Braenden, J U

2008-12-01

The influence of various formulation properties on the chemical stability of captopril in aqueous media at pH 3 was investigated, in order to reformulate and increase the shelf-life of an oral mixture of the drug. At this pH, chemical stability is improved by an increase in drug concentration (1-5 mg/ml) and a decrease in temperature (5-36 degrees C), the latter demonstrated by a linear Arrhenius-plot. The activation energy is low (Ea = 10.2 kcal/mol), thus the Q10 value is only 1.8 in pure aqueous solutions. The degradation at the lowest concentration investigated in pure aqueous solution apparently follows zero order kinetics. The reaction order is changed at higher concentrations. We are presenting a hypothesis of intramolecular proton transfer from the thiol to the ionized carboxylic group as the initial step in the oxidative degradation pathways of captopril. Long-term stability of 1 mg/ml captopril in aqueous solutions at pH 3, stored at 36 degrees C for one year, shows that the sugar alcohol sorbitol accelerates degradation of the drug while Na-EDTA at a concentration as low as 0.01% is sufficient to stabilize these samples. Purging with N2-gas prior to storage is not essential for drug stability, as long as Na-EDTA is present. Only at a low level of Na-EDTA (0.01%) combined with a high level of sorbitol (35%), purging with N2-gas appears to have a small effect. The destabilizing effect of sugar alcohols is confirmed by accelerated degradation also in the presence of glycerol. The efficient stabilization in the presence of Na-EDTA at a low concentration indicates that the metal-ion-catalyzed oxidation pathway dominates the chemical degradation process at low pH, although several mechanisms seem to be involved depending on excipients present.

Hemoglobin bioconjugates with surface-protected gold nanoparticles in aqueous media: The stability depends on solution pH and protein properties.

PubMed

Del Caño, Rafael; Mateus, Lucia; Sánchez-Obrero, Guadalupe; Sevilla, José Manuel; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

2017-11-01

The identification of the factors that dictate the formation and physicochemical properties of protein-nanomaterial bioconjugates are important to understand their behavior in biological systems. The present work deals with the formation and characterization of bioconjugates made of the protein hemoglobin (Hb) and gold nanoparticles (AuNP) capped with three different molecular layers (citrate anions (c), 6-mercaptopurine (MP) and ω-mercaptoundecanoic acid (MUA)). The main focus is on the behavior of the bioconjugates in aqueous buffered solutions in a wide pH range. The stability of the bioconjugates have been studied by UV-visible spectroscopy by following the changes in the localized surface resonance plasmon band (LSRP), Dynamic light scattering (DLS) and zeta-potential pH titrations. It has been found that they are stable in neutral and alkaline solutions and, at pH lower than the protein isoelectric point, aggregation takes place. Although the surface chemical properties of the AuNPs confer different properties in respect to colloidal stability, once the bioconjugates are formed their properties are dictated by the Hb protein corona. The protein secondary structure, as analyzed by Attenuated total reflectance infrared (ATR-IR) spectroscopy, seems to be maintained under the conditions of colloidal stability but some small changes in protein conformation take place when the bioconjugates aggregate. These findings highlight the importance to keep the protein structure upon interaction with nanomaterials to drive the stability of the bioconjugates. Copyright © 2017 Elsevier Inc. All rights reserved.

Anions adsorption onto nanoparticles: effects on colloid stability and mobility in the environment

NASA Astrophysics Data System (ADS)

Missana, Tiziana; Benedicto, Ana; Mayordomo, Natalia; Alonso, Ursula

2013-04-01

Nanoparticles and colloids can enhance the contaminant transport in groundwater, if the contaminant is irreversibly adsorbed onto their surface; additionally colloids must be stable and mobile under the chemical conditions of the environment of interest. Colloid stability and mobility are factors directly related to the chemistry of the water, which determines the charge and size of the particles, but these colloidal properties can also be affected by the contaminant adsorption. This last point, which is potentially very relevant on the overall colloid-driven transport, is scarcely investigated. The evaluation of the stability of a colloidal system is generally carried out by measuring the aggregation kinetic after the change of a specific chemical condition, mainly pH or ionic strength of the aqueous solution. The effect of anion adsorption onto the stability of colloidal systems is mostly neglected. Parameters of the nanoparticles,as the point of zero charge (pH PCZ) or the isoelectric point (pH IEP) are determined with "inert" electrolytes and this might not be representative of their real behavior in natural systems. In this work, the effects of the Se(IV) (selenite) adsorption on alumina (Al2O3) nanoparticles have been analyzed. Selenite adsorption was studied in a wide range of pH (2-12) and ionic strengths (0.0005 - 0.1 M in NaClO4) and the effect of the adsorption on the main properties of the colloids (size and charge) were analyzed. Se adsorption on Al2O3 is almost independent of the ionic strength and decreases with increasing pH; sorption data were successfully fit by surface complexation modeling. Selenite adsorption (at medium-high surface occupancies) clearly affected the stability of Al2O3 colloids, with a clear shift of the isoelectric point towards more acid pH and enhancing colloid aggregation when the ionic strength increases. Considering the obtained results, the effect of anions in the chemical composition of natural water, frequently not accounted for in stability studies, will be discussed, as well as their implications on possible colloid-driven selenite transport in the environment.

pH-Dependent Stability of Creatine Ethyl Ester: Relevance to Oral Absorption

PubMed Central

Gufford, Brandon T.; Ezell, Edward L.; Robinson, Dennis H.; Miller, Donald W.; Miller, Nicholas J.; Gu, Xiaochen; Vennerstrom, Jonathan L.

2015-01-01

Creatine ethyl ester hydrochloride (CEE) was synthesized as a prodrug of creatine (CRT) to improve aqueous solubility, gastrointestinal permeability, and ultimately the pharmacodynamics of CRT. We used high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (NMR) to characterize the pH-dependent stability of CEE in aqueous solution and compared the permeability of CEE to CRT and creatinine (CRN) across Caco-2 human epithelial cell monolayers and transdermal permeability across porcine skin. CEE was most stable in a strongly acidic condition (half-life = 570 hours at pH 1.0) where it undergoes ester hydrolysis to CRT and ethanol. At pH ≥ 1.0, CEE cyclizes to CRN with the logarithm of the first order rate constant increasing linearly with pH. Above pH 8.0 (half-life = 23 sec) the rate of degradation was too rapid to be determined. The rate of degradation of CEE in cell culture media and simulated intestinal fluid (SIF) was a function of pH and correlated well with the stability in aqueous buffered solutions. The permeability of CEE across Caco-2 monolayers and porcine skin was significantly greater than that of CRT or CRN. The stability of CEE in acidic media together with its improved permeability suggests that CEE has potential for improved oral absorption compared to CRT. PMID:23957855

Anthrax vaccine powder formulations for nasal mucosal delivery.

PubMed

Jiang, Ge; Joshi, Sangeeta B; Peek, Laura J; Brandau, Duane T; Huang, Juan; Ferriter, Matthew S; Woodley, Wendy D; Ford, Brandi M; Mar, Kevin D; Mikszta, John A; Hwang, C Robin; Ulrich, Robert; Harvey, Noel G; Middaugh, C Russell; Sullivan, Vincent J

2006-01-01

Anthrax remains a serious threat worldwide as a bioterror agent. A second-generation anthrax vaccine currently under clinical evaluation consists of a recombinant Protective Antigen (rPA) of Bacillus anthracis. We have previously demonstrated that complete protection against inhalational anthrax can be achieved in a rabbit model, by intranasal delivery of a powder rPA formulation. Here we describe the preformulation and formulation development of such powder formulations. The physical stability of rPA was studied in solution as a function of pH and temperature using circular dichroism (CD), and UV-visible absorption and fluorescence spectroscopies. Extensive aggregation of rPA was observed at physiological temperatures. An empirical phase diagram, constructed using a combination of CD and fluorescence data, suggests that rPA is most thermally stable within the pH range of 6-8. To identify potential stabilizers, a library of GRAS excipients was screened using an aggregation sensitive turbidity assay, CD, and fluorescence. Based on these stability profiles, spray freeze-dried (SFD) formulations were prepared at pH 7-8 using trehalose as stabilizer and a CpG-containing oligonucleotide adjuvant. SFD formulations displayed substantial improvement in storage stability over liquid formulations. In combination with noninvasive intranasal delivery, such powder formulations may offer an attractive approach for mass biodefense immunization.

Pre-formulation and chemical stability studies of penethamate, a benzylpenicillin ester prodrug, in aqueous vehicles.

PubMed

Jain, Rohit; Wu, Zimei; Bork, Olaf; Tucker, Ian G

2012-01-01

Penethamate (PNT) is a diethylaminoethyl ester prodrug of benzylpenicillin used to treat bovine mastitis via the intramuscular route. Because of its instability, PNT products must be reconstituted before administration and the reconstituted injection has a short shelf life (7 days at 2-8°C). The purpose of this paper was to investigate whether the stability of PNT can be improved in order to achieve a chemically stable ready-to-use aqueous-based PNT formulation or at least to extend the shelf life of the reconstituted suspension. A chemical stability study of PNT in aqueous-based solutions as a function of pH, buffer strength, solvent mixtures and temperature, supported by studies of its solubility in mixed solvents, allowed predictions of the shelf life of PNT solution and suspension formulations. PNT degraded in aqueous solutions by several pathways over the pH range 2.0-9.3 with a V-shaped pH-rate profile and a minimum pH of around 4.5. The stability of PNT solutions in mixed solvents was greater than in aqueous solutions. For example, in propylene glycol:citrate buffer (60:40, v/v, pH 4.5), the half-life of PNT was 4.3 days compared with 1.8 days in aqueous buffer. However, solubility of PNT in the mixed solvent was higher than that in aqueous solution and this had an adverse effect on the stability of suspensions. By judicious choosing of pH and mixed solvent, it is possible to achieve a storage life of a PNT suspension of 5.5 months at 5°C, not sufficient for a ready-to-use product but a dramatic improvement in the storage life of the reconstituted product.

Surface acidity and solid-state compatibility of excipients with an acid-sensitive API: case study of atorvastatin calcium.

PubMed

Govindarajan, Ramprakash; Landis, Margaret; Hancock, Bruno; Gatlin, Larry A; Suryanarayanan, Raj; Shalaev, Evgenyi Y

2015-04-01

The objectives of this study were to measure the apparent surface acidity of common excipients and to correlate the acidity with the chemical stability of an acid-sensitive active pharmaceutical ingredient (API) in binary API-excipient powder mixtures. The acidity of 26 solid excipients was determined by two methods, (i) by measuring the pH of their suspensions or solutions and (ii) the pH equivalent (pHeq) measured via ionization of probe molecules deposited on the surface of the excipients. The chemical stability of an API, atorvastatin calcium (AC), in mixtures with the excipients was evaluated by monitoring the appearance of an acid-induced degradant, atorvastatin lactone, under accelerated storage conditions. The extent of lactone formation in AC-excipient mixtures was presented as a function of either solution/suspension pH or pHeq. No lactone formation was observed in mixtures with excipients having pHeq > 6, while the lactone levels were pronounced (> 0.6% after 6 weeks at 50°C/20% RH) with excipients exhibiting pHeq < 3. The three pHeq regions (> 6, 3-6, and < 3) were consistent with the reported solution pH-stability profile of AC. In contrast to the pHeq scale, lactone formation did not show any clear trend when plotted as a function of the suspension/solution pH. Two mechanisms to explain the discrepancy between the suspension/solution pH and the chemical stability data were discussed. Acidic excipients, which are expected to be incompatible with an acid-sensitive API, were identified based on pHeq measurements. The incompatibility prediction was confirmed in the chemical stability tests using AC as an example of an acid-sensitive API.

Stability studies of lincomycin hydrochloride in aqueous solution and intravenous infusion fluids.

PubMed

Czarniak, Petra; Boddy, Michael; Sunderland, Bruce; Hughes, Jeff D

2016-01-01

The purpose of this study was to evaluate the chemical stability of Lincocin(®) (lincomycin hydrochloride) in commonly used intravenous fluids at room temperature (25°C), at accelerated-degradation temperatures and in selected buffer solutions. The stability of Lincocin(®) injection (containing lincomycin 600 mg/2 mL as the hydrochloride) stored at 25°C±0.1°C in sodium lactate (Hartmann's), 0.9% sodium chloride, 5% glucose, and 10% glucose solutions was investigated over 31 days. Forced degradation of Lincocin(®) in hydrochloric acid, sodium hydroxide, and hydrogen peroxide was performed at 60°C. The effect of pH on the degradation rate of lincomycin hydrochloride stored at 80°C was determined. Lincomycin hydrochloride w as found to maintain its shelf life at 25°C in sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution, with less than 5% lincomycin degradation occurring in all intravenous solutions over a 31-day period. Lincomycin hydrochloride showed less rapid degradation at 60°C in acid than in basic solution, but degraded rapidly in hydrogen peroxide. At all pH values tested, lincomycin followed first-order kinetics. It had the greatest stability near pH 4 when stored at 80°C (calculated shelf life of 4.59 days), and was least stable at pH 2 (calculated shelf life of 0.38 days). Lincocin(®) injection was chemically found to have a shelf life of at least 31 days at 25°C when added to sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution. Solutions prepared at approximately pH 4 are likely to have optimum stability.

Preformulation stability study of the EGFR inhibitor HKI-272 (Neratinib) and mechanism of degradation.

PubMed

Lu, Qinghong; Ku, Mannching Sherry

2012-03-01

The stability in solution of HKI-272 (Neratinib) was studied as a function of pH. The drug is most stable from pH 3 to 4, and degradation rate increases rapidly around pH 6 and appears to approach a maximum asymptotic limit in the range of pH 812. Pseudo first-order reaction kinetics was observed at all pH values. The structure of the major degradation product indicates that it is formed by a cascade of reactions within the dimethylamino crotonamide group of HKI-272. It is assumed that the rate-determining step is the initial isomerization from allyl amine to enamine functionality, followed by hydrolysis and subsequent cyclization to a stable lactam. The maximum change in degradation rate as a function of pH occurs at about pH 6, which corresponds closely to the theoretical pKa value of the dimethylamino group of HKI-272 when accounting for solvent/temperature effects. The observed relationship between pH and degradation rate is discussed, and a self-catalyzed mechanism for the allylamine-enamine isomerization reaction is proposed. The relevance of these findings to other allylamine drugs is discussed in terms of the relative stability of the allylic anion intermediate through which, the isomerization occurs.

CIP (cleaning-in-place) stability of AlGaN/GaN pH sensors.

PubMed

Linkohr, St; Pletschen, W; Schwarz, S U; Anzt, J; Cimalla, V; Ambacher, O

2013-02-20

The CIP stability of pH sensitive ion-sensitive field-effect transistors based on AlGaN/GaN heterostructures was investigated. For epitaxial AlGaN/GaN films with high structural quality, CIP tests did not degrade the sensor surface and pH sensitivities of 55-58 mV/pH were achieved. Several different passivation schemes based on SiO(x), SiN(x), AlN, and nanocrystalline diamond were compared with special attention given to compatibility to standard microelectronic device technologies as well as biocompatibility of the passivation films. The CIP stability was evaluated with a main focus on the morphological stability. All stacks containing a SiO₂ or an AlN layer were etched by the NaOH solution in the CIP process. Reliable passivations withstanding the NaOH solution were provided by stacks of ICP-CVD grown and sputtered SiN(x) as well as diamond reinforced passivations. Drift levels about 0.001 pH/h and stable sensitivity over several CIP cycles were achieved for optimized sensor structures. Copyright © 2012 Elsevier B.V. All rights reserved.

High-Throughput Biophysical Analysis and Data Visualization of Conformational Stability of an IgG1 Monoclonal Antibody (mAb) After Deglycosylation

PubMed Central

Alsenaidy, Mohammad A.; Kim, Jae Hyun; Majumdar, Ranajoy; Weis, David D.; Joshi, Sangeeta B.; Tolbert, Thomas J.; Middaugh, C. Russell; Volkin, David B.

2013-01-01

The structural integrity and conformational stability of an IgG1 monoclonal antibody (mAb), after partial and complete enzymatic removal of the N-linked Fc glycan, was compared to the untreated mAb over a wide range of temperature (10° to 90°C) and solution pH (3 to 8) using circular dichroism, fluorescence spectroscopy, and static light scattering combined with data visualization employing empirical phase diagrams (EPDs). Subtle to larger stability differences between the different glycoforms were observed. Improved detection of physical stability differences was then demonstrated over narrower pH range (4.0-6.0) using smaller temperature increments, especially when combined with an alternative data visualization method (radar plots). Differential scanning calorimetry and differential scanning fluorimetry were then utilized and also showed an improved ability to detect differences in mAb glycoform physical stability. Based on these results, a two-step methodology was used in which mAb glycoform conformational stability is first screened with a wide variety of instruments and environmental stresses, followed by a second evaluation with optimally sensitive experimental conditions, analytical techniques and data visualization methods. With this approach, high-throughput biophysical analysis to assess relatively subtle conformational stability differences in protein glycoforms is demonstrated. PMID:24114789

Atomic view of the histidine environment stabilizing higher-pH conformations of pH-dependent proteins

PubMed Central

Valéry, Céline; Deville-Foillard, Stéphanie; Lefebvre, Christelle; Taberner, Nuria; Legrand, Pierre; Meneau, Florian; Meriadec, Cristelle; Delvaux, Camille; Bizien, Thomas; Kasotakis, Emmanouil; Lopez-Iglesias, Carmen; Gall, Andrew; Bressanelli, Stéphane; Le Du, Marie-Hélène; Paternostre, Maïté; Artzner, Franck

2015-01-01

External stimuli are powerful tools that naturally control protein assemblies and functions. For example, during viral entry and exit changes in pH are known to trigger large protein conformational changes. However, the molecular features stabilizing the higher pH structures remain unclear. Here we elucidate the conformational change of a self-assembling peptide that forms either small or large nanotubes dependent on the pH. The sub-angstrom high-pH peptide structure reveals a globular conformation stabilized through a strong histidine-serine H-bond and a tight histidine-aromatic packing. Lowering the pH induces histidine protonation, disrupts these interactions and triggers a large change to an extended β-sheet-based conformation. Re-visiting available structures of proteins with pH-dependent conformations reveals both histidine-containing aromatic pockets and histidine-serine proximity as key motifs in higher pH structures. The mechanism discovered in this study may thus be generally used by pH-dependent proteins and opens new prospects in the field of nanomaterials. PMID:26190377

Effect of pH on subunit association and heat protection of soybean alpha-galactosidase

NASA Technical Reports Server (NTRS)

Porter, J. E.; Sarikaya, A.; Herrmann, K. M.; Ladisch, M. R.; Mitchell, C. A. (Principal Investigator)

1992-01-01

Soybeans contain the enzyme alpha-galactosidase, which hydrolyzes alpha-1, 6 linkages in stachyose and raffinose to give sucrose and galactose. We have found that galactose, a competitive product inhibitor of alpha-galactosidase, strongly promotes the heat stability of the tetrameric form of the enzyme at pH 4.0 and at temperatures of up to 70 degrees C for 60 min. Stachyose and raffinose also protect alpha-galactosidase from denaturation at pH 4.0 although to a lesser extent. Glucose and mannose have little effect. At pH 7.0 the enzyme is a monomer, and galactose has no effect on the heat stability of the enzyme. In the absence of heat protection of the enzyme by added sugars, a series deactivation mechanism was found to describe the deactivation data. In comparison, a unimolecular, non-first order deactivation model applies at pH 4.0, where heat protection effects were observed. At a temperature above 60 degrees C, simple deactivation is a suitable model. The results suggest that alpha-galactosidase conformation and heat stability are directly related.

Testing the stability of magnetic iron oxides/kaolinite nanocomposite under various pH conditions

NASA Astrophysics Data System (ADS)

Tokarčíková, Michaela; Tokarský, Jonáš; Kutláková, Kateřina Mamulová; Seidlerová, Jana

2017-09-01

Magnetically modified clays containing iron oxides nanoparticles (FexOy NPs) are low-cost and environmentally harmless materials suitable for sorption of pollutants from wastewaters. Stability of this smart material was evaluated both experimentally and theoretically using molecular modelling. Original kaolinite and prepared FexOy/kaolinite nanocomposite were characterized using X-ray fluorescence spectroscopy, X-ray powder diffraction, infrared spectroscopy, and transmission electron microscopy, and the stability was studied using leaching tests performed according to the European technical standard EN 12457-2 in deionized water and extraction agents with varying pH (2, 4, 9, and 11). The influence of pH on amount of FexOy NPs released from the composite and amount of the basic elements released from the kaolinite structure was studied using inductively coupled plasma atomic emission spectroscopy. All experiments proved that the magnetic properties of the nanocomposite will not change even after leaching in extraction agents with various pH.

Improved stability of chokeberry juice anthocyanins by β-cyclodextrin addition and refrigeration.

PubMed

Howard, Luke R; Brownmiller, Cindi; Prior, Ronald L; Mauromoustakos, Andy

2013-01-23

Chokeberry anthocyanins are susceptible to degradation during processing and storage of processed products. This study determined the effects of three pH levels (2.8, 3.2, and 3.6) and four β-cyclodextrin (BCD) concentrations (0, 0.5, 1, and 3%) alone and in combination on the stability of chokeberry juice anthocyanins before and after pasteurization and over 8 months of storage at 4 and 25 °C. Lowering the pH from 3.6 to 2.8 in the absence of BCD provided marginal protection against anthocyanin losses during processing and storage. Addition of 3% BCD at the natural chokeberry pH of 3.6 resulted in excellent protection of anthocyanins, with 81 and 95% retentions after 8 months of storage at 25 and 4 °C, respectively. The protective effect of BCD was lessened with concentrations <3% and reduction in pH, indicating changes in anthocyanin structure play an important role in BCD stabilization of anthocyanins.

Antioxidant study of quercetin and their metal complex and determination of stability constant by spectrophotometry method.

PubMed

Ravichandran, R; Rajendran, M; Devapiriam, D

2014-03-01

Quercetin found chelate cadmium ions, scavenge free radicals produced by cadmium. Hence new complex, quercetin with cadmium was synthesised, and the synthesised complex structures were determined by UV-vis spectrophotometry, infrared spectroscopy, thermogravimetry and differential thermal analysis techniques (UV-vis, IR, TGA and DTA). The equilibrium stability constants of quercetin-cadmium complex were determined by Job's method. The determined stability constant value of quercetin-cadminum complex at pH 4.4 is 2.27×10(6) and at pH 7.4 is 7.80×10(6). It was found that the quercetin and cadmium ion form 1:1 complex in both pH 4.4 and pH 7.4. The structure of the compounds was elucidated on the basis of obtained results. Furthermore, the antioxidant activity of the free quercetin and quercetin-cadmium complexes were determined by DPPH and ABTS assays. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effect of excipients on the stability of levothyroxine sodium pentahydrate tablets.

PubMed

Patel, Himanshu; Stalcup, Apryll; Dansereau, Richard; Sakr, Adel

2003-10-02

Levothyroxine tablets, 50 microg, have been marketed for many decades but have had numerous recalls due to degradation and failure to meet potency. These experiments were devised to study the effects of various excipients on the stability of levothyroxine sodium pentahydrate in aqueous slurries and in formulated tablets. The active alone was found to be stable in the solid state for 6 months at 40 degrees C/75% RH whether stored in open or closed containers, and was found to be non-hygroscopic under normal processing conditions (>30% RH). In aqueous slurries with an excipient, the stability of the active improved as the pH of the slurry was increased from pH 3 to 11. Tablets manufactured with lactose anhydrous, starch, or microcrystalline cellulose failed to meet USP assay requirements at 3 months at 40 degrees C/75% RH. Tablets manufactured with dibasic calcium phosphate or mannitol met USP assay requirements at 3, but not 6 months when stored at 40 degrees C/75% RH. Tablets manufactured with dibasic calcium phosphate and a basic pH modifier, such as sodium carbonate, sodium bicarbonate, or magnesium oxide, met the USP assay requirements at both 3 and 6 months. Thus, the use of basic pH modifiers is a potential technique for improving the stability of levothyroxine sodium pentahydrate tablets.

Improved sugar beet pectin-stabilized emulsions through complexation with sodium caseinate.

PubMed

Li, Xiangyang; Fang, Yapeng; Phillips, Glyn O; Al-Assaf, Saphwan

2013-02-13

The study investigates the complexes formed between sodium caseinate (SC) and sugar beet pectin (SBP) and to harness them to stabilize SBP emulsions. We find that both hydrophobic and electrostatic interactions are involved in the complexation. In SC/SBP mixed solution, soluble SC/SBP complexes first form on acidification and then aggregate into insoluble complexes, which disassociate into soluble polymers upon further decreasing pH. The critical pH's for the formation of soluble and insoluble complexes and disappearance of insoluble complexes are designated as pH(c), pH(φ), and pH(d), respectively. These critical pH values define four regions in the phase diagram of complexation, and SC/SBP emulsions were prepared in these regions. The results show that the stability of SBP-stabilized emulsion is greatly improved at low SC/SBP ratios and acidic pH's. This enhancement can be attributed to an increase in the amount of adsorbed SBP as a result of cooperative adsorption to sodium caseinate. Using a low ratio of SC/SBP ensured that all caseinate molecules are completely covered by adsorbed SBP chains, which eliminates possible instability induced by thermal aggregation of caseinate molecules resulting from stress acceleration at elevated temperatures. A mechanistic model for the behavior is proposed.

The effect of net charge on the solubility, activity, and stability of ribonuclease Sa.

PubMed

Shaw, K L; Grimsley, G R; Yakovlev, G I; Makarov, A A; Pace, C N

2001-06-01

The net charge and isoelectric pH (pI) of a protein depend on the content of ionizable groups and their pK values. Ribonuclease Sa (RNase Sa) is an acidic protein with a pI = 3.5 that contains no Lys residues. By replacing Asp and Glu residues on the surface of RNase Sa with Lys residues, we have created a 3K variant (D1K, D17K, E41K) with a pI = 6.4 and a 5K variant (3K + D25K, E74K) with a pI = 10.2. We show that pI values estimated using pK values based on model compound data can be in error by >1 pH unit, and suggest how the estimation can be improved. For RNase Sa and the 3K and 5K variants, the solubility, activity, and stability have been measured as a function of pH. We find that the pH of minimum solubility varies with the pI of the protein, but that the pH of maximum activity and the pH of maximum stability do not.

Effects of pH, temperature, and chemical structure on the stability of S-(purin-6-yl)-L-cysteine: evidence for a novel molecular rearrangement mechanism to yield N-(purin-6-yl)-L-cysteine.

PubMed

Elfarra, A A; Hwang, I Y

1996-01-01

The stability of S-(purin-6-yl)-L-cysteine (SPC), a kidney-selective prodrug of 6-mercaptopurine and a putative metabolite of 6-chloropurine, was investigated under various pH and temperature conditions. At room temperature, the half-life (t 1/2) of SPC at either highly acidic (pH 3.6) or basic conditions (pH 9.6) was longer than at neutral or slightly acidic or basic conditions (pH 5.7-8.75). The primary degradation product, N-(purin-6-yl)-L-cysteine (NPC), was isolated using Sephadex LH-20 chromatography and characterized by 1H NMR and FAB/MS after derivatization with 2-iodoacetic acid. These results reveal novel stability requirements and implicate the cysteinyl amino group and the purinyl N-1 nitrogen in the mechanism of SPC rearrangement to NPC. Further evidence for this hypothesis was provided by the findings that the stability of SPC in phosphate buffer (pH 7.4) at 37 degrees C was similar to that of S-(guanin-6-yl)-L-cysteine, whereas S-(purin-6-yl)-N-acetyl-L-cysteine and S-(purin-6-yl)glutathione which have their cysteine amino groups blocked were much more stable than SPC. S-(Purin-6-yl)-L-homocysteine (SPHC) was also more stable than SPC, possibly because the formation of a 6-membered ring transition state as would be expected with SPHC is kinetically less favored than the formation of a 5-membered ring transition state as would be expected with SPC. These results may explain previous in vivo metabolism results of SPC and its analogs and may contribute to a better understanding of stability of structurally related cysteine S-conjugates.

Effects of copper on the antioxidant activity of olive polyphenols in bulk oil and oil-in-water emulsions.

PubMed

Paiva-Martins, Fátima; Santos, Vera; Mangericão, Hugo; Gordon, Michael H

2006-05-17

The antioxidant activity and interactions with copper of four olive oil phenolic compounds, namely oleuropein, hydroxytyrosol, 3,4-dihydroxyphenylethanol-elenolic acid (1), and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (2), in olive oil and oil-in-water emulsions stored at 60 degrees C were studied. All four phenolic compounds significantly extended the induction time of lipid oxidation in olive oil with the order of activity being hydroxytyrosol > compound 1 > compound 2 > oleuropein > alpha-tocopherol; but in the presence of Cu(ll), the stability of oil samples containing phenolic compounds decreased by at least 90%, and the antioxidant activity of hydroxytyrosol and compounds 1 and 2 became similar. In oil-in-water emulsions prepared from olive oil stripped of tocopherols, hydroxytyrosol enhanced the prooxidant effect of copper at pH 5.5 but not at pH 7.4. The stability of samples containing copper at pH 5.5 was not significantly different if oleuropein was present from that of the control. Oleuropein at pH 7.4, and compounds 1 and 2 at both pH values tested, reduced the prooxidant effect of copper. The lower stability and the higher reducing capacity of all compounds at pH 7.4 could not explain the higher stability of emulsions containing phenolic compounds at this pH value. However, mixtures containing hydroxytyrosol or oleuropein with copper showed higher 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity at pH 7.4 than at pH 5.5. Moreover, the compound 2-copper complex showed higher radical scavenging activity then the uncomplexed compound at pH 5.5. It can be concluded that the formation of a copper complex with radical scavenging activity is a key step in the antioxidant action of the olive oil phenolic compounds in an emulsion containing copper ions.

Evaluation of the pH- and Thermal Stability of the Recombinant Green Fluorescent Protein (GFP) in the Presence of Sodium Chloride

NASA Astrophysics Data System (ADS)

Ishii, Marina; Kunimura, Juliana Sayuri; Jeng, Hélio Tallon; Vessoni Penna, Thereza Christina; Cholewa, Olivia

The thermal stability of recombinant green fluorescent protein (GFP) in sodium chloride (NaCl) solutions at different concentrations, pH, and temperatures was evaluated by assaying the loss of fluorescence intensity as a measure of denaturation. GFP, extracted from Escherichia coli cells by the three-phase partitioning method and purified through a butyl hydrophobic interaction chromatography (HIC) column, was diluted in water for injection (WFI) (pH 6.0-7.0) and in 10 mM buffer solutions (acetate, pH 5.0; phosphate, pH 7.0; and Tris-EDTA, pH 8.0) with 0.9-30% NaCl or without and incubated at 80-95°C. The extent of protein denaturation was expressed as a percentage of the calculated decimal reduction time (D-value). In acetate buffer (pH 4.84 ±0.12), the mean D-values for 90% reduction in GFP fluorescence ranged from 2.3 to 3.6 min, independent of NaCl concentration and temperature. GFP thermal stability diluted in WFI (pH 5.94±0.60) was half that observed in phosphate buffer (pH 6.08±0.60); but in both systems, D-values decreased linearly with increasing NaCl concentration, with D-values (at 80°C) ranging from 3.44, min (WFI) to 6.1 min (phosphate buffer), both with 30% NaCl. However, D-values in Tris-EDTA (pH 7.65±0.17) were directly dependent on the NaCl concentration and 5-10 times higher than D-values for GFP in WFI at 80°C. GFP pH-and thermal stability can be easily monitored by the convenient measure of fluorescence intensity and potentially be used as an indicator to monitor that processing times and temperatures were attained.

[Thermostabilization of glutamin(asparagin)ase from Pseudomonas aurantica BKMB-548].

PubMed

Kabanova, E A; Lebedeva, Z I; Berezov, T T

1985-01-01

In studies on kinetics of thermoinactivation of glutaminase (asparaginase) from Ps. arantiaca BKMB-548 at 50 degrees and pH 7.0 in presence or in absence of L-glutamate the enzyme inactivation was found to obey the first order equation. Both the glutaminase and asparaginase activities decreased at a similar rate. L-Glutamate stabilized the enzyme due to direct interaction with its molecule. Stability of the complex formed was evaluated quantitatively. L-Glutamate reacted apparently with a specific site on the surface of the enzyme molecule; Kdiss was 0.42 +/- 0.03 mM at pH 7.0 and 50 degrees. No cooperative effect was found. L-Aspartate protected the enzyme completely; stabilizing effects of L-cysteine, L-serine and glycine were similar to the effect of L-glutamate (94%, 84%, 83% and 82%, respectively). At the same time, glutarate, succinate, alpha-ketobutyrate, alpha-ketoglutarate, gamma-aminobutyrate and N-benzoyl glutamate did not exhibit the stabilization effect. The data obtained suggest that the high stabilizing effect might exhibit only the substances containing simultaneously free alpha-NH2 and alpha-COOH groups in a molecule, whereas presence of COOH groups at beta--or gamma-carbon atoms was not essential for the stabilizing effect.

Formulation of a stable parenteral product; Clonidine Hydrochloride Injection.

PubMed

Kostecka, D; Duncan, M R; Wagenknecht, D

1998-01-01

Clonidine Hydrochloride Injection (Duraclon) is a clear, colorless, preservative-free, pyrogen free, aqueous solution of clonidine hydrochloride. The indication for this product is for use as an adjunct in pain management, administered epidurally, when opiates are insufficient. The drug formulation was evaluated under both normal and stress conditions in the preformulation/formulation studies. The list of studies conducted includes a light sensitivity study, an oxygen sensitivity study, a pH/stability study, a stopper compatibility evaluation, a freeze-thaw study, and a stability study. Samples from the light, oxygen, pH/stability, and stability studies were evaluated for color, visual clarity, pH, potency, and chromatographic purity. Samples from the freeze-thaw study were evaluated for all of the above except chromatographic purity. The results for these studies demonstrate the stability of the product as formulated. The pH of this unbuffered product was consistently within the acceptance criteria. The product remained clear and colorless for the duration of each study. The values obtained for the potency and chromatographic purity assays showed no evidence of degradation. The reasons for the lack of degradation can be found in the molecular structure of the drug substance and the formulation of the drug product. Since the molecular structure is that of a Schiff base, it is theoretically possible, although difficult, to cleave the molecule. A catalyst would be required, and none of the possible catalysts are present in the formulation. The molecule could also be cleaved upon exposure to light, and the evidence indicates that the molecule does interact with light. This interaction is not to the degree, however, that product stability is affected. The formulation contains only the active drug substance and sodium chloride in water for injection with a pH of approximately 6. Although the product is unbuffered, the influence of the stoppers and glass vials upon the formulation pH was minimal. In addition, the stopper compatibility of the product is enhanced by the absence of chelating agents, preservatives, acids, and bases. Since the dilute concentrations of both the active and excipient are well below their solubility limits, no solubility related issues would be expected upon freezing and subsequent thawing. Clonidine Hydrochloride Injection, as formulated, does not require protection from light, oxygen, or freezing. The product shows acceptable stability within the pH range, and the rubber closure is compatible with the product. Real time stability data combined with statistical projections support a 36-month expiration date.

Enhanced gastric stability of esomeprazole by molecular interaction and modulation of microenvironmental pH with alkalizers in solid dispersion.

PubMed

Van Nguyen, Hien; Baek, Namhyun; Lee, Beom-Jin

2017-05-15

Due to the instability of esomeprazole magnesium dihydrate (EPM), a proton pump inhibitor, in gastric fluid, enteric-coated dosage form is commonly used for therapeutic application. In this study, we prepared new gastric fluid resistant solid dispersions (SDs) containing alkalizers. Then, new mechanistic evidence regarding the effects of pharmaceutical alkalizers on the aqueous stability of EPM in simulated gastric fluid was investigated. The alkalizer-loaded SD were prepared by dissolving or dispersing EPM, hydroxypropyl methylcellulose (HPMC) 6 cps, and an alkalizer, in ethanol 50% (v/v) followed by spray drying. Nine different alkalizers were assessed for in vitro stability in two media, simulated gastric fluid (pH 1.2 buffer) and simulated intestinal fluid (pH 6.8 buffer). The microenvironmental pH (pH M ) was measured to evaluate the effect of the alkalizer on the pH M of SDs. Drug crystallinity and morphology of the SDs were also examined by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The interactions among EPM, the polymer, and the alkalizer were elucidated by Fourier transform infrared (FTIR) spectroscopy. The in vivo absorption studies of the optimized alkalizer-containing SD and the enteric-coated reference tablet Nexium ® were then conducted in beagle dogs. Among alkalizers, MgO loaded in SDs proved to be the best alkalizer to stabilize EPM in simulated gastric fluid. pH M values of the alkalizer-containing SDs were significantly higher than that of the SD without alkalizer. The pH M values decreased in the following order: MgO, Na 2 CO 3 , Ca(OH) 2 , and no alkalizer. DSC and PXRD data exhibited a change in the drug crystallinity of the SDs from crystalline to amorphous form. SEM data showed a relatively spherical shape of the MgO-loaded SD compared to the less-defined shape of pure drug. FTIR indicated a strong molecular interaction among EPM, alkalizer and polymer; in particular, MgO showed the strongest interaction with EPM. It was evident that alkalizer interacts with benzimidazole ring and/or sulfonyl group of EPM for enhancing EPM stability in gastric fluid. Regarding the in vivo absorption studies in beagle dogs, the optimized SD (C16) was bioequivalent to the reference Nexium ® and had a considerable greater absorption at the early stages. The current alkalizer-containing SD could provide a promising approach for aqueous stabilization of acid-labile drugs without using enteric coating method. Copyright © 2017 Elsevier B.V. All rights reserved.

Buffer capacity of biologics--from buffer salts to buffering by antibodies.

PubMed

Karow, Anne R; Bahrenburg, Sven; Garidel, Patrick

2013-01-01

Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions. Copyright © 2013 American Institute of Chemical Engineers.

Stabilization of T4 bacteriophage at acidic and basic pH by adsorption on paper.

PubMed

Meyer, Abigail; Greene, Melissa; Kimmelshue, Chad; Cademartiri, Rebecca

2017-12-01

Bacteriophages find applications in agriculture, medicine, and food safety. Many of these applications can expose bacteriophages to stresses that inactivate them including acidic and basic pH. Bacteriophages can be stabilized against these stresses by materials including paper, a common material in packaging and consumer products. Combining paper and bacteriophages creates antibacterial materials, which can reduce the use of antibiotics. Here we show that adsorption on paper protects T4, T5, and T7 bacteriophage from acidic and basic pH. We added bacteriophages to filter paper functionalized with carboxylic acid (carboxyl methyl cellulose) or amine (chitosan) groups, and exposed them to pH from 5.6 to 14. We determined the number of infective bacteriophages after exposure directly on the paper. All papers extended the lifetime of infective bacteriophage by at least a factor of four with some papers stabilizing bacteriophages for up to one week. The degree of stabilization depended on five main factors (i) the family of the bacteriophage, (ii) the charge of the paper and bacteriophages, (iii) the location of the bacteriophages within the paper, (iv) the ability of the paper to prevent bacteriophage-bacteriophage aggregation, and (v) the sensitivity of the bacteriophage proteins to the tested pH. Even when adsorbed on paper the bacteriophages were able to remove E. coli in milk. Choosing the right paper modification or material will protect bacteriophages adsorbed on that material against detrimental pH and other environmental challenges increasing the range of applications of bacteriophages on materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Pre-formulation studies of resveratrol

PubMed Central

Robinson, Keila; Mock, Charlotta; Liang, Dong

2015-01-01

Context Resveratrol, a natural compound found in grapes, has potential chemotherapy effects but very low oral bioavailability in humans. Objective To evaluate the solubility, pH stability profile, plasma protein binding (PPB) and stability in plasma for resveratrol. Methods Solubility of resveratrol was measured in 10 common solvents at 25 °C using HPLC. The solution state pH stability of resveratrol was assessed in various United States Pharmacopeia buffers ranging from pH 2 to 10 for 24 h at 37 °C. Samples were analyzed up to 24 h. Human PPB was determined using ultracentrifugation technique. Standard solutions of drug were spiked to blank human plasma to yield final concentrations of 5, 12.5 or 25 µg/mL for determination. Finally, stability of resveratrol in human and rat plasma was also assessed at 37 °C. Aliquots of blank plasma were spiked with a standard drug concentration to yield final plasma concentration of 50 µg/mL. Samples were analyzed for resveratrol concentration up to 96 h. Results Resveratrol has wide solubility ranging from 0.05 mg/mL in water to 374 mg/mL in polyethylene glycol 400 (PEG-400). Resveratrol is relatively stable above pH 6 and has maximum degradation at pH 9. The mean PPB of resveratrol is 98.3%. Resveratrol degrades in human and rat plasma in a first-order process with mean half lives of 54 and 25 h, respectively. Conclusion Resveratrol is more soluble in alcohol and PEG-400 and stable in acidic pH. It binds highly to plasma proteins and degrades slower in human then rat plasma. PMID:25224342

The effect of arginine glutamate on the stability of monoclonal antibodies in solution.

PubMed

Kheddo, Priscilla; Tracka, Malgorzata; Armer, Jonathan; Dearman, Rebecca J; Uddin, Shahid; van der Walle, Christopher F; Golovanov, Alexander P

2014-10-01

Finding excipients which mitigate protein self-association and aggregation is an important task during formulation. Here, the effect of an equimolar mixture of l-Arg and l-Glu (Arg·Glu) on colloidal and conformational stability of four monoclonal antibodies (mAb1-mAb4) at different pH is explored, with the temperatures of the on-set of aggregation (Tagg) and unfolding (Tm1) measured by static light scattering and intrinsic fluorescence, respectively. Arg·Glu increased the Tagg of all four mAbs in concentration-dependent manner, especially as pH increased to neutral. Arg·Glu also increased Tm1 of the least thermally stable mAb3, but without similar direct effect on the Tm1 of other mAbs. Raising pH itself from 5 to 7 increased Tm1 for all four mAbs. Selected mAb formulations were assessed under accelerated stability conditions for the monomer fraction remaining in solution after storage. The aggregation of mAb3 was suppressed to a greater extent by Arg·Glu than by Arg·HCl. Furthermore, Arg·Glu suppressed the aggregation of mAb1 at neutral pH such that the fraction monomer was near to that at the more typical formulation pH of 5.5. We conclude that Arg·Glu can suppress mAb aggregation with increasing temperature/pH and, importantly, under accelerated stability conditions at weakly acidic to neutral pH. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Overview of waste stabilization with cement.

PubMed

Batchelor, B

2006-01-01

Cement can treat a variety of wastes by improving physical characteristics (solidification) and reducing the toxicity and mobility of contaminants (stabilization). Potentially adverse waste-binder interactions are an important consideration because they can limit solidification. Stabilization occurs when a contaminant is converted from the dissolved (mobile) phase to a solid (immobile) phase by reactions, such as precipitation, sorption, or substitution. These reactions are often strongly affected by pH, so the presence of components of the waste that control pH are critical to stabilization reactions. Evaluating environmental impacts can be accomplished in a tiered strategy in which simplest approach would be to measure the maximum amount of contaminant that could be released. Alternatively, the sequence of release can be determined, either by microcosm tests that attempt to simulate conditions in the disposal zone or by mechanistic models that attempt to predict behavior using fundamental characteristics of the treated waste.

Design of template-stabilized active and earth-abundant oxygen evolution catalysts in acid† †Electronic supplementary information (ESI) available: CVs for unary metal oxides deposition, electrochemical stability at higher current densities for unary metal oxides at pH 2.5, EDS maps for CoMnOx and CoPbOx, STEM images and PXRD of CoMnOx and CoFePbOx, high-resolution XPS of Fe 2p for CoFePbOx, Pourbaix diagrams (of Mn, Co, Pb, and Fe), and elemental analysis. See DOI: 10.1039/c7sc01239j Click here for additional data file.

PubMed Central

Huynh, Michael; Ozel, Tuncay; Liu, Chong; Lau, Eric C.

2017-01-01

Oxygen evolution reaction (OER) catalysts that are earth-abundant and are active and stable in acid are unknown. Active catalysts derived from Co and Ni oxides dissolve at low pH, whereas acid stable systems such as Mn oxides (MnOx) display poor OER activity. We now demonstrate a rational approach for the design of earth-abundant catalysts that are stable and active in acid by treating activity and stability as decoupled elements of mixed metal oxides. Manganese serves as a stabilizing structural element for catalytically active Co centers in CoMnOx films. In acidic solutions (pH 2.5), CoMnOx exhibits the OER activity of electrodeposited Co oxide (CoOx) with a Tafel slope of 70–80 mV per decade while also retaining the long-term acid stability of MnOx films for OER at 0.1 mA cm–2. Driving OER at greater current densities in this system is not viable because at high anodic potentials, Mn oxides convert to and dissolve as permanganate. However, by exploiting the decoupled design of the catalyst, the stabilizing structural element may be optimized independently of the Co active sites. By screening potential–pH diagrams, we replaced Mn with Pb to prepare CoFePbOx films that maintained the high OER activity of CoOx at pH 2.5 while exhibiting long-term acid stability at higher current densities (at 1 mA cm–2 for over 50 h at pH 2.0). Under these acidic conditions, CoFePbOx exhibits OER activity that approaches noble metal oxides, thus establishing the viability of decoupling functionality in mixed metal catalysts for designing active, acid-stable, and earth-abundant OER catalysts. PMID:29163926

[Studies of local anaesthetics: part 205* studies of stability of heptacainium chloride and carbisocainium chloride using an accelerated non-isothermal test].

PubMed

Stankovičová, Mária; Lašáková, Andrea; Medlenová, Veronika; Bezáková, Zelmíra; Cižmárik, Jozef

2014-08-01

The paper studies the kinetics of alkaline hydrolysis and stability under non-isothermal conditions of heptacainium chloride and carbisocainium chloride in the medium of aqueous-ethanolic solution of sodium hydroxide c = 0.1 mol/l and buffer solutions of values of pH 7.0 and pH 8.0. The results of the study of the kinetics of hydrolysis by means of a non-isothermal test - rate constants and activation energy values served as the basis for exact evaluation of the stability of these potential pharmaceuticals. The objective of the paper links up with the previous studies of these substances.

Molecular gated-AlGaN/GaN high electron mobility transistor for pH detection.

PubMed

Ding, Xiangzhen; Yang, Shuai; Miao, Bin; Gu, Le; Gu, Zhiqi; Zhang, Jian; Wu, Baojun; Wang, Hong; Wu, Dongmin; Li, Jiadong

2018-04-18

A molecular gated-AlGaN/GaN high electron mobility transistor has been developed for pH detection. The sensing surface of the sensor was modified with 3-aminopropyltriethoxysilane to provide amphoteric amine groups, which would play the role of receptors for pH detection. On modification with 3-aminopropyltriethoxysilane, the transistor exhibits good chemical stability in hydrochloric acid solution and is sensitive for pH detection. Thus, our molecular gated-AlGaN/GaN high electron mobility transistor acheived good electrical performances such as chemical stability (remained stable in hydrochloric acid solution), good sensitivity (37.17 μA/pH) and low hysteresis. The results indicate a promising future for high-quality sensors for pH detection.

Pulsed Plasma Preparation for LWIR Materials

DTIC Science & Technology

1990-06-18

Reported Data: AlP is normally considered chemically unstable with respect to hydrolysis and formation of PH3 as a result of the exceptional stability of...A1203 (and consequently it is often used as a fumigant ). Its stability is thought to increase with purity. The thermal conductivity of crystalline...AlP is high (-1.3 Wcm’Kŕ at room temperature). Experimental Data: Initial films of aluminium phosphide, deposited from trimethylaluminium (TMA) and PH3

Cold denaturation as a tool to measure protein stability

PubMed Central

Sanfelice, Domenico; Temussi, Piero Andrea

2016-01-01

Protein stability is an important issue for the interpretation of a wide variety of biological problems but its assessment is at times difficult. The most common parameter employed to describe protein stability is the temperature of melting, at which the populations of folded and unfolded species are identical. This parameter may yield ambiguous results. It would always be preferable to measure the whole stability curve. The calculation of this curve is greatly facilitated whenever it is possible to observe cold denaturation. Using Yfh1, one of the few proteins whose cold denaturation occurs at neutral pH and low ionic strength, we could measure the variation of its full stability curve under several environmental conditions. Here we show the advantages of gauging stability as a function of external variables using stability curves. PMID:26026885

Stabilization of global temperature at 1.5°C and 2.0°C: implications for coastal areas

PubMed Central

Brown, Sally; Wolff, Claudia; Merkens, Jan-Ludolf

2018-01-01

The effectiveness of stringent climate stabilization scenarios for coastal areas in terms of reduction of impacts/adaptation needs and wider policy implications has received little attention. Here we use the Warming Acidification and Sea Level Projector Earth systems model to calculate large ensembles of global sea-level rise (SLR) and ocean pH projections to 2300 for 1.5°C and 2.0°C stabilization scenarios, and a reference unmitigated RCP8.5 scenario. The potential consequences of these projections are then considered for global coastal flooding, small islands, deltas, coastal cities and coastal ecology. Under both stabilization scenarios, global mean ocean pH (and temperature) stabilize within a century. This implies significant ecosystem impacts are avoided, but detailed quantification is lacking, reflecting scientific uncertainty. By contrast, SLR is only slowed and continues to 2300 (and beyond). Hence, while coastal impacts due to SLR are reduced significantly by climate stabilization, especially after 2100, potential impacts continue to grow for centuries. SLR in 2300 under both stabilization scenarios exceeds unmitigated SLR in 2100. Therefore, adaptation remains essential in densely populated and economically important coastal areas under climate stabilization. Given the multiple adaptation steps that this will require, an adaptation pathways approach has merits for coastal areas. This article is part of the theme issue ‘The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels’. PMID:29610380

Stabilization of global temperature at 1.5°C and 2.0°C: implications for coastal areas.

PubMed

Nicholls, Robert J; Brown, Sally; Goodwin, Philip; Wahl, Thomas; Lowe, Jason; Solan, Martin; Godbold, Jasmin A; Haigh, Ivan D; Lincke, Daniel; Hinkel, Jochen; Wolff, Claudia; Merkens, Jan-Ludolf

2018-05-13

The effectiveness of stringent climate stabilization scenarios for coastal areas in terms of reduction of impacts/adaptation needs and wider policy implications has received little attention. Here we use the Warming Acidification and Sea Level Projector Earth systems model to calculate large ensembles of global sea-level rise (SLR) and ocean pH projections to 2300 for 1.5°C and 2.0°C stabilization scenarios, and a reference unmitigated RCP8.5 scenario. The potential consequences of these projections are then considered for global coastal flooding, small islands, deltas, coastal cities and coastal ecology. Under both stabilization scenarios, global mean ocean pH (and temperature) stabilize within a century. This implies significant ecosystem impacts are avoided, but detailed quantification is lacking, reflecting scientific uncertainty. By contrast, SLR is only slowed and continues to 2300 (and beyond). Hence, while coastal impacts due to SLR are reduced significantly by climate stabilization, especially after 2100, potential impacts continue to grow for centuries. SLR in 2300 under both stabilization scenarios exceeds unmitigated SLR in 2100. Therefore, adaptation remains essential in densely populated and economically important coastal areas under climate stabilization. Given the multiple adaptation steps that this will require, an adaptation pathways approach has merits for coastal areas.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'. © 2018 The Authors.

Stabilization of global temperature at 1.5°C and 2.0°C: implications for coastal areas

NASA Astrophysics Data System (ADS)

Nicholls, Robert J.; Brown, Sally; Goodwin, Philip; Wahl, Thomas; Lowe, Jason; Solan, Martin; Godbold, Jasmin A.; Haigh, Ivan D.; Lincke, Daniel; Hinkel, Jochen; Wolff, Claudia; Merkens, Jan-Ludolf

2018-05-01

The effectiveness of stringent climate stabilization scenarios for coastal areas in terms of reduction of impacts/adaptation needs and wider policy implications has received little attention. Here we use the Warming Acidification and Sea Level Projector Earth systems model to calculate large ensembles of global sea-level rise (SLR) and ocean pH projections to 2300 for 1.5°C and 2.0°C stabilization scenarios, and a reference unmitigated RCP8.5 scenario. The potential consequences of these projections are then considered for global coastal flooding, small islands, deltas, coastal cities and coastal ecology. Under both stabilization scenarios, global mean ocean pH (and temperature) stabilize within a century. This implies significant ecosystem impacts are avoided, but detailed quantification is lacking, reflecting scientific uncertainty. By contrast, SLR is only slowed and continues to 2300 (and beyond). Hence, while coastal impacts due to SLR are reduced significantly by climate stabilization, especially after 2100, potential impacts continue to grow for centuries. SLR in 2300 under both stabilization scenarios exceeds unmitigated SLR in 2100. Therefore, adaptation remains essential in densely populated and economically important coastal areas under climate stabilization. Given the multiple adaptation steps that this will require, an adaptation pathways approach has merits for coastal areas. This article is part of the theme issue `The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

The Phosphorolytic Exoribonucleases Polynucleotide Phosphorylase and RNase PH Stabilize sRNAs and Facilitate Regulation of Their mRNA Targets

PubMed Central

2016-01-01

ABSTRACT Gene regulation by base pairing between small noncoding RNAs (sRNAs) and their mRNA targets is an important mechanism that allows bacteria to maintain homeostasis and respond to dynamic environments. In Gram-negative bacteria, sRNA pairing and regulation are mediated by several RNA-binding proteins, including the sRNA chaperone Hfq and polynucleotide phosphorylase (PNPase). PNPase and its homolog RNase PH together represent the two 3′ to 5′ phosphorolytic exoribonucleases found in Escherichia coli; however, the role of RNase PH in sRNA regulation has not yet been explored and reported. Here, we have examined in detail how PNPase and RNase PH interact to support sRNA stability, activity, and base pairing in exponential and stationary growth conditions. Our results indicate that these proteins facilitate the stability and regulatory function of the sRNAs RyhB, CyaR, and MicA during exponential growth. PNPase further appears to contribute to pairing between RyhB and its mRNA targets. During stationary growth, each sRNA responded differently to the absence or presence of PNPase and RNase PH. Finally, our results suggest that PNPase and RNase PH stabilize only Hfq-bound sRNAs. Taken together, these results confirm and extend previous findings that PNPase participates in sRNA regulation and reveal that RNase PH serves a similar, albeit more limited, role as well. These proteins may, therefore, act to protect sRNAs from spurious degradation while also facilitating regulatory pairing with their targets. IMPORTANCE In many bacteria, Hfq-dependent base-pairing sRNAs facilitate rapid changes in gene expression that are critical for maintaining homeostasis and responding to stress and environmental changes. While a role for Hfq in this process was identified more than 2 decades ago, the identity and function of the other proteins required for Hfq-dependent regulation by sRNAs have not been resolved. Here, we demonstrate that PNPase and RNase PH, the two phosphorolytic RNases in E. coli, stabilize sRNAs against premature degradation and, in the case of PNPase, also accelerate regulation by sRNA-mRNA pairings for certain sRNAs. These findings are the first to demonstrate that RNase PH influences and supports sRNA regulation and suggest shared and distinct roles for these phosphorolytic RNases in this process. PMID:27698082

Enhanced stability and permeation potential of nanoemulsion containing sefsol-218 oil for topical delivery of amphotericin B.

PubMed

Hussain, Afzal; Samad, Abdus; Singh, Sandeep Kumar; Ahsan, Mohd Neyaz; Faruk, Abdul; Ahmed, Farhan Jalees

2015-05-01

To characterize the enhanced stability and permeation potential of amphotericin B nanoemulsion comprising sefsol-218 oil at varying pH and temperature of aqueous continuous phase. Several batches of amphotericin B loaded nanoemulsion were prepared and evaluated for their physical and chemical stability at different pH and temperature. Also, a comparative study of ex vivo drug permeation across the albino rat skin was investigated with commercial Fungisome® and drug solution at 37 °C for 24 h. The extent of drug penetrated through the rat skin was thereby evaluated using the confocal laser scanning microscopy (CLSM). The optimized nanoemulsion demonstrated the highest flux rate 17.85 ± 0.5 µg/cm(2)/h than drug solution (5.37 ± 0.01 µg/cm(2)/h) and Fungisome® (7.97 ± 0.01 µg/cm(2)/h). Ex vivo drug penetration mechanism from the developed formulations at pH 6.8 and pH 7.4 of aqueous phase pH using the CLSM revealed enhanced penetration. Ex vivo drug penetration studies of developed formulation comprising of CLSM revealed enhanced penetration in aqueous phase at pH 6.8 and 7.4. The aggregation behavior of nanoemulsion at both the pH was found to be minimum and non-nephrotoxic. The stability of amphotericin B was obtained in terms of pH, optical density, globular size, polydispersity index and zeta potential value at different temperature for 90 days. The slowest drug degradation was observed in aqueous phase at pH 7.4 with shelf life 20.03-folds higher when stored at 4 °C (3.8 years) and 5-fold higher at 25 °C (0.951 years) than at 40 °C. The combined results suggested that nanoemulsion may hold an alternative for enhanced and sustained topical delivery system for amphotericin B.

Physicochemical properties and storage stability of soybean protein nanoemulsions prepared by ultra-high pressure homogenization.

PubMed

Xu, Jing; Mukherjee, Dipaloke; Chang, Sam K C

2018-02-01

This study investigated the effects of the ultrahigh pressure homogenization (pressure, protein concentration, oil phase fraction, pH, temperature, and ionic strength) and storage on the properties of nanoemulsions (100-500nm range), which were stabilized by laboratory-prepared soybean protein isolate (SPI), β-conglycinin (7S) and glycinin (11S). The nanoemulsions made with SPI, 7S and 11S proteins exhibited considerable stability over various ionic strengths (0-500mM NaCl), pH (<4 or >7), thermal treatments (30-60°C) and storage (0-45days). The far-UV spectra of SPI, 7S, 11S dispersions, and SPI-, 7S-, 11S protein-stabilized nanoemulsions were analyzed for the protein structural changes following lipid removal. The ultra-high pressure homogenization changed the secondary structure of SPI, 7S, 11S proteins in the nanoemulsions, and enhanced their stability. This study demonstrated that SPI, 7S, and 11S proteins can be used as effective emulsifiers in nanoemulsions prepared by ultra-high pressure homogenization. Copyright © 2017. Published by Elsevier Ltd.

Stability of florfenicol in drinking water.

PubMed

Hayes, John M; Eichman, Jonathan; Katz, Terry; Gilewicz, Rosalia

2003-01-01

Florfenicol, a broad-spectrum antibiotic, is being developed for veterinary application as an oral concentrate intended for dilution with drinking water. When a drug product is dosed via drinking water in a farm setting, a number of variables, including pH, chlorine content, hardness of the water used for dilution, and container material, may affect its stability, leading to a decrease in drug potency. The stability of florfenicol after dilution of Florfenicol Drinking Water Concentrate Oral Solution, 23 mg/mL, with drinking water was studied. A stability-indicating, validated liquid chromatographic method was used to evaluate florfenicol stability at 25 degrees C at 5, 10, and 24 h after dilution. The results indicate that florfenicol is stable under a range of simulated field conditions, including various pipe materials and conditions of hard or soft and chlorinated or nonchlorinated water at low or high pH. Significant degradation (> 10%) was observed only for isolated combinations in galvanized pipes. Analysis indicated that the florfenicol concentration in 8 of the 12 water samples stored in galvanized pipes remained above 90% of the initial concentration (100 mg/L) for 24 h after dilution.

Structure-Based Engineering of Methionine Residues in the Catalytic Cores of Alkaline Amylase from Alkalimonas amylolytica for Improved Oxidative Stability

PubMed Central

Yang, Haiquan; Wang, Mingxing; Li, Jianghua; Wang, Nam Sun; Du, Guocheng

2012-01-01

This work aims to improve the oxidative stability of alkaline amylase from Alkalimonas amylolytica through structure-based site-directed mutagenesis. Based on an analysis of the tertiary structure, five methionines (Met 145, Met 214, Met 229, Met 247, and Met 317) were selected as the mutation sites and individually replaced with leucine. In the presence of 500 mM H2O2 at 35°C for 5 h, the wild-type enzyme and the M145L, M214L, M229L, M247L, and M317L mutants retained 10%, 28%, 46%, 28%, 72%, and 43% of the original activity, respectively. Concomitantly, the alkaline stability, thermal stability, and catalytic efficiency of the M247L mutant were also improved. The pH stability of the mutants (M145L, M214L, M229L, and M317L) remained unchanged compared to that of the wild-type enzyme, while the stable pH range of the M247L mutant was extended from pH 7.0 to 11.0 for the wild type to pH 6.0 to 12.0 for the mutant. The wild-type enzyme lost its activity after incubation at 50°C for 2 h, and the M145L, M214L, M229L, and M317L mutants retained less than 14% of the activity, whereas the M247L mutant retained 34% of the activity under the same conditions. Compared to the wild-type enzyme, the kcat values of the M145L, M214L, M229L, and M317L mutants decreased, while that of the M247L mutant increased slightly from 5.0 × 104 to 5.6 × 104 min−1. The mechanism responsible for the increased oxidative stability, alkaline stability, thermal stability, and catalytic efficiency of the M247L mutant was further analyzed with a structure model. The combinational mutants were also constructed, and their biochemical properties were characterized. The resistance of the wild-type enzyme and the mutants to surfactants and detergents was also investigated. Our results indicate that the M247L mutant has great potential in the detergent and textile industries. PMID:22865059

[Nutrient contents and microbial populations of aeolian sandy soil in Sanjiangyuan region of Qinghai Province].

PubMed

Lin, Chao-feng; Chen, Zhan-quan; Xue, Quan-hong; Lai, Hang-xian; Chen, Lai-sheng; Zhang, Deng-shan

2007-01-01

Sanjiangyuan region (the headstream of three rivers) in Qinghai Province of China is the highest and largest inland alpine wetland in the world. The study on the nutrient contents and microbial populations of aeolian sandy soils in this region showed that soil organic matter content increased with the evolution of aeolian sand dunes from un-stabilized to stabilized state, being 5.9 and 3.8 times higher in stabilized sand dune than in mobile and semi-stabilized sand dunes, respectively. Soil nitrogen and phosphorus contents increased in line with the amount of organic matter, while potassium content and pH value varied slightly. The microbial populations changed markedly with the development of vegetation, fixing of mobile sand, and increase of soil nutrients. The quantities of soil bacteria, fungi and actinomycetes were 4.0 and 2.8 times, 19.6 and 6.3 times, and 12.4 and 2.6 times higher in stabilized and semi-stabilized sand dunes than in mobile sand dune, respectively, indicating that soil microbial bio-diversity was increased with the evolution of aeolian sand dunes from mobile to stabilized state. In addition, the quantities of soil microbes were closely correlated with the contents of soil organic matter, total nitrogen, and available nitrogen and phosphorus, but not correlated with soil total phosphorus, total and available potassium, or pH value.

Rotation in vibration, optimization, and aeroelastic stability problems. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Kaza, K. R. V.

1974-01-01

The effects of rotation in the areas of vibrations, dynamic stability, optimization, and aeroelasticity were studied. The governing equations of motion for the study of vibration and dynamic stability of a rapidly rotating deformable body were developed starting from the nonlinear theory of elasticity. Some common features such as the limitations of the classical theory of elasticity, the choice of axis system, the property of self-adjointness, the phenomenon of frequency splitting, shortcomings of stability methods as applied to gyroscopic systems, and the effect of internal and external damping on stability in gyroscopic systems are identified and discussed, and are then applied to three specific problems.

Effect of citronella essential oil fractions as oil phase on emulsion stability

NASA Astrophysics Data System (ADS)

Septiyanti, Melati; Meliana, Yenny; Agustian, Egi

2017-11-01

The emulsion system consists of water, oil and surfactant. In order to create stable emulsion system, the composition and formulation between water phase, surfactant and oil phase are very important. Essential oil such as citronella oil has been known as active ingredient which has ability as insect repellent. This research studied the effect of citronella oil and its fraction as oil phase on emulsion stability. The cycle stability test was conducted to check the emulsion stability and it was monitored by pH, density, viscosity, particle size, refractive index, zeta potential, physical appearance and FTIR for 4 weeks. Citronellal fraction has better stability compared to citronella oil and rhodinol fraction with slight change of physical and chemical properties before and after the cycle stability test. However, it is need further study to enhance the stability of the emulsion stability for this formulation.

Methylation of Brazilein on Secang (Caesalpinia sappan Linn) Wood Extract for Maintain Color Stability to the Changes of pH

NASA Astrophysics Data System (ADS)

Ulma, Zeni; Rahayuningsih, Edia; Dwi Wahyuningsih, Tutik

2018-01-01

The stability of natural dyes to the changes of pH is really necessary when the natural dyes are applied either on fabric or food. This research aimed to increase the stability of brazilein, a compound contained within the secang wood extract, to the changes of pH. The methylation process was done by reacting Dimethyl Carbonate (DMC) with the brazilein on the secang wood extract. DMC acts as a substance that substitute hydroxyl group on brazilein. The methylation reaction of brazilein on secang wood extract was operated on a three-necked round-bottomed flask fitted with mercury-sealed stirrer and reflux condenser under 80°C temperature and 250 rpm stirring speed. There were two variables observed in this research; the DMC amount ratio to the amount of secang wood extract and the time of the methylation process. The research showed that at the 1:10 the DMC amount ratio to the amount of wood extract and 8 hours of the methylation process give the better stability of color of the secang wood extract than the variation of the other variables.

Effect of polyethylene glycol conjugation on conformational and colloidal stability of a monoclonal antibody antigen-binding fragment (Fab').

PubMed

Roque, Cristopher; Sheung, Anthony; Rahman, Nausheen; Ausar, S Fernando

2015-02-02

We have investigated the effects of site specific "hinge" polyethylene glycol conjugation (PEGylation) on thermal, pH, and colloidal stability of a monoclonal antibody antigen-binding fragment (Fab') using a variety of biophysical techniques. The results obtained by circular dichroism (CD), ultraviolet (UV) absorbance, and fluorescence spectroscopy suggested that the physical stability of the Fab' is maximized at pH 6-7 with no apparent differences due to PEGylation. Temperature-induced aggregation experiments revealed that PEGylation was able to increase the transition temperature, as well as prevent the formation of visible and subvisible aggregates. Statistical comparison of the three-index empirical phase diagram (EPD) revealed significant differences in thermal and pH stability signatures between Fab' and PEG-Fab'. Upon mechanical stress, micro-flow imaging (MFI) and measurement of the optical density at 360 nm showed that the PEG-Fab' had significantly higher resistance to surface-induced aggregation compared to the Fab'. Analysis of the interaction parameter, kD, indicated repulsive intermolecular forces for PEG-Fab' and attractive forces for Fab'. In conclusion, PEGylation appears to protect Fab' against thermal and mechanical stress-induced aggregation, likely due to a steric hindrance mechanism.

Pinhão starch and coat extract as new natural cosmetic ingredients: Topical formulation stability and sensory analysis.

PubMed

Daudt, Renata Moschini; Back, Patrícia Inês; Cardozo, Nilo Sérgio Medeiros; Marczak, Ligia Damasceno Ferreira; Külkamp-Guerreiro, Irene Clemes

2015-12-10

The objective of this study was to use pinhão derivatives, starch and coat extract, as new natural ingredients to develop cosmetic formulations. Two types of formulation, gel and emulgel, and their controls were developed. The formulations were characterized by stability studies using thermal stress. The parameters analyzed were resistance to centrifugation, pH, spreadability, rheology, content of phenolic compounds and antioxidant activity. Sensory analysis was also performed to verify the acceptability of the ingredients to potential consumers. The pH was kept the same after heating/freezing cycles for all formulations, and the formulations showed stability by resistance to centrifugation. The formulations did not induce any skin irritation or cutaneous pH alteration. The pinhão starch addition improved spreadability stability and increased viscosity when compared with control formulations. The pinhão coat extract used in these formulations is a good source of phenolic compounds and antioxidant activity. Moreover, sensory analysis indicates that the emulgel formulation is the best vehicle for adding pinhão starch and pinhão coat extract. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stabilization and Solidification of Nitric Acid Effluent Waste at Y-12

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Dileep; Lorenzo-Martin, Cinta

Consolidated Nuclear Security, LLC (CNS) at the Y-12 plant is investigating approaches for the treatment (stabilization and solidification) of a nitric acid waste effluent that contains uranium. Because the pH of the waste stream is 1-2, it is a difficult waste stream to treat and stabilize by a standard cement-based process. Alternative waste forms are being considered. In this regard, Ceramicrete technology, developed at Argonne National Laboratory, is being explored as an option to solidify and stabilize the nitric acid effluent wastes.

Bacteriophage enzymes for the prevention and treatment of bacterial infections: Stability and stabilization of the enzyme lysing Streptococcus pyogenes cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klyachko, N. L.; Dmitrieva, N. F.; Eshchina, A. S.

2008-06-01

Recombinant, phage associated lytic enzyme Ply C capable to lyse streptococci of groups A and C was stabilized in the variety of the micelles containing compositions to improve the stability of the enzyme for further application in medicine. It was shown that, in the micellar polyelectrolyte composition M16, the enzyme retained its activity for 2 months; while in a buffer solution under the same conditions ((pH 6.3, room temperature), it completely lost its activity in 2 days

Analysis of SAT Type Foot-And-Mouth Disease Virus Capsid Proteins and the Identification of Putative Amino Acid Residues Affecting Virus Stability

PubMed Central

Maree, Francois F.; Blignaut, Belinda; de Beer, Tjaart A. P.; Rieder, Elizabeth

2013-01-01

Foot-and-mouth disease virus (FMDV) initiates infection by adhering to integrin receptors on target cells, followed by cell entry and disassembly of the virion through acidification within endosomes. Mild heating of the virions also leads to irreversible dissociation into pentamers, a characteristic linked to reduced vaccine efficacy. In this study, the structural stability of intra- and inter-serotype chimeric SAT2 and SAT3 virus particles to various conditions including low pH, mild temperatures or high ionic strength, was compared. Our results demonstrated that while both the SAT2 and SAT3 infectious capsids displayed different sensitivities in a series of low pH buffers, their stability profiles were comparable at high temperatures or high ionic strength conditions. Recombinant vSAT2 and intra-serotype chimeric viruses were used to map the amino acid differences in the capsid proteins of viruses with disparate low pH stabilities. Four His residues at the inter-pentamer interface were identified that change protonation states at pH 6.0. Of these, the H145 of VP3 appears to be involved in interactions with A141 in VP3 and K63 in VP2, and may be involved in orientating H142 of VP3 for interaction at the inter-pentamer interfaces. PMID:23717387

Effect of the inducers veratryl alcohol, Xylidine, and ligninosulphonates on activity and thermal stability and inactivation kinetics of laccase from Trametes versicolor.

PubMed

Saraiva, Jorge A; Tavares, Ana P M; Xavier, Ana M R B

2012-06-01

Laccase production from Trametes versicolor was improved in the presence of the inducers ligninosulphonates, veratryl alcohol, and xylidine respectively two-, four-, and eightfold. The thermal inactivation of the produced laccase, after partial purification with ammonium sulfate was kinetically investigated at various temperatures (60-70 °C) and pH values (3.5, 4.5, and 5.5). The inactivation process followed first-order kinetics for all conditions tested, except for veratryl alcohol, for which a constant activity level was observed at the end of the inactivation, also after first-order decay. Enzyme thermostability was affected by the type of inducer used in the culture medium for the production of laccase and also by the pH of incubation mixture. Generally, laccase stability increased with pH increment, being more stable at pH 5.5, except with xylidine. At pHs 4.5 and 5.5, the three inducers significantly increased laccase thermal stability, with the higher effect being observed for pH 5.5 and ligninosulphonates, where increment of half-life times ranged from 3- to 20-fold, depending on the temperature.

Nanoparticle titanium dioxide aqueous interfacial energy can be modified to control phase stability, coarsening, and morphology

NASA Astrophysics Data System (ADS)

Finnegan, Michael Patrick

The effect of solution chemistry on the phase stability, coarsening kinetics and morphology of titanium dioxide (TiO2) nanoparticles is investigated in order to attain efficient production pathways to desired nano-structures with optimal properties. To obtain sample, TiO2 was synthesized via hydrolysis of titanium isopropoxide producing an 85% anatase/15% brookite mixture. The titania was hydrothermally heated in an array of temperatures and pH values for various times. There are distinct phase stability fields for nanoscale titania based on pH alone due to slight interface charging behavior differences among the polymorphs. The mixture transforms to rutile below the pH of zero point of charge (ZPC) and remains anatase above the ZPC. This phenomenon is partially reversible. The solution chemistry also dictates the hydrothermal coarsening mechanism of the anatase polymorph. Ostwald ripening (OR) takes place in basic pH where titania solubility is elevated relative to neutral pH where lower solubility prevents rapid OR but allows for coarsening via oriented attachment (OA) of nanoparticles. This OA event can alter the symmetry of anatase causing unexpected and perhaps technically useful morphologies such as straight and curved nanorods during coarsening.

Biochemical stabilization of glucagon at alkaline pH.

PubMed

Caputo, Nicholas; Jackson, Melanie A; Castle, Jessica R; El Youssef, Joseph; Bakhtiani, Parkash A; Bergstrom, Colin P; Carroll, Julie M; Breen, Matthew E; Leonard, Gerald L; David, Larry L; Roberts, Charles T; Ward, W Kenneth

2014-11-01

For patients with type 1 diabetes mellitus, a bihormonal artificial endocrine pancreas system utilizing glucagon and insulin has been found to stabilize glycemic control. However, commercially available formulations of glucagon cannot currently be used in such systems because of physical instability characterized by aggregation and chemical degradation. Storing glucagon at pH 10 blocks protein aggregation but results in chemical degradation. Reductions in pH minimize chemical degradation, but even small reductions increase protein aggregation. We hypothesized that common pharmaceutical excipients accompanied by a new excipient would inhibit glucagon aggregation at an alkaline pH. As measured by tryptophan intrinsic fluorescence shift and optical density at 630 nm, protein aggregation was indeed minimized when glucagon was formulated with curcumin and albumin. This formulation also reduced chemical degradation, measured by liquid chromatography with mass spectrometry. Biological activity was retained after aging for 7 days in an in vitro cell-based bioassay and also in Yorkshire swine. Based on these findings, a formulation of glucagon stabilized with curcumin, polysorbate-80, l-methionine, and albumin at alkaline pH in glycine buffer may be suitable for extended use in a portable pump in the setting of a bihormonal artificial endocrine pancreas.

Biochemical Stabilization of Glucagon at Alkaline pH

PubMed Central

Jackson, Melanie A.; Castle, Jessica R.; El Youssef, Joseph; Bakhtiani, Parkash A.; Bergstrom, Colin P.; Carroll, Julie M.; Breen, Matthew E.; Leonard, Gerald L.; David, Larry L.; Roberts, Charles T.; Ward, W. Kenneth

2014-01-01

Abstract Background: For patients with type 1 diabetes mellitus, a bihormonal artificial endocrine pancreas system utilizing glucagon and insulin has been found to stabilize glycemic control. However, commercially available formulations of glucagon cannot currently be used in such systems because of physical instability characterized by aggregation and chemical degradation. Storing glucagon at pH 10 blocks protein aggregation but results in chemical degradation. Reductions in pH minimize chemical degradation, but even small reductions increase protein aggregation. We hypothesized that common pharmaceutical excipients accompanied by a new excipient would inhibit glucagon aggregation at an alkaline pH. Methods and Results: As measured by tryptophan intrinsic fluorescence shift and optical density at 630 nm, protein aggregation was indeed minimized when glucagon was formulated with curcumin and albumin. This formulation also reduced chemical degradation, measured by liquid chromatography with mass spectrometry. Biological activity was retained after aging for 7 days in an in vitro cell-based bioassay and also in Yorkshire swine. Conclusions: Based on these findings, a formulation of glucagon stabilized with curcumin, polysorbate-80, l-methionine, and albumin at alkaline pH in glycine buffer may be suitable for extended use in a portable pump in the setting of a bihormonal artificial endocrine pancreas. PMID:24968220

Optimizing acidified bleach solutions to improve sporicidal efficacy on building materials.

PubMed

Wood, J P; Calfee, M W; Clayton, M; Griffin-Gatchalian, N; Touati, A

2011-12-01

We evaluated whether lowering pH (with acetic acid) and raising free available chlorine (FAC) levels in bleach solutions would improve efficacy in inactivating Bacillus spores on different materials. We also determined how varying pH and FAC levels affected bleach stability. Acidified bleach solutions with pH levels of 4.5, 6 and 7.5 and FAC levels between 5000 and 10,000 ppm were evaluated for decontamination efficacy against Bacillus subtilis spores inoculated onto test coupons made from wood, ceramic and galvanized steel. Lowering the pH or increasing the FAC level improved efficacy in some of the tests, but depended on the material, which significantly affected decontamination efficacy. The acidified bleach at pH of 7.5 was significantly less effective than bleach at a pH of 4.5 or 6. The FAC levels in the bleach were the most stable at pH 4.5, and stability at pH 4.5 was not significantly affected by the initial FAC level. It may be advisable to use bleach solutions with lower pH (rather than high FAC levels) in light of both the decontamination efficacy and bleach stability results. For wood materials, use of sporicides other than acidified bleach may be warranted. These results may be useful in preparing acidified bleach solutions for decontamination of materials contaminated with spores such as Bacillus anthracis. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

Structure-activity relationships on the study of β-galactosidase folding/unfolding due to interactions with immobilization additives: Triton X-100 and ethanol.

PubMed

Soto, Dayana; Escobar, Sindy; Guzmán, Fanny; Cárdenas, Constanza; Bernal, Claudia; Mesa, Monica

2017-03-01

Improving the enzyme stability is a challenge for allowing their practical application. The surfactants are stabilizing agents, however, there are still questions about their influence on enzyme properties. The structure-activity/stability relationship for β-galactosidase from Bacillus circulans is studied here by Circular Dichroism and activity measurements, as a function of temperature and pH. The tendency of preserving the β-sheet and α-helix structures at temperatures below 65°C and different pH is the result of the balance between the large- and short-range effects, respecting to the active site. This information is fundamental for explaining the structural changes of this enzyme in the presence of Triton X-100 surfactant and ethanol. The enzyme thermal stabilization in the presence of this surfactant responds to the rearrangement of the secondary structure for having optimal activity/stability. The effect of ethanol is more related with changes in the dielectric properties of the aqueous solution than with protein structural transformations. These results contribute to understand the effects of surfactant-enzyme interactions on the enzyme behavior, from the structural point of view and to rationalize the surfactant-based stabilizing strategies for β-galactosidades. Copyright © 2016 Elsevier B.V. All rights reserved.

A spectroscopic study on stability of curcumin as a function of pH in silica nanoformulations, liposome and serum protein

NASA Astrophysics Data System (ADS)

Jain, Beena

2017-02-01

The effect of pH on the stability of curcumin formulated with different carriers has been studied spectroscopically. This was investigated by monitoring the absorption and emission kinetics and fluorescence decay time of four different curcumin formulations suspended in buffer with pH varying from 5 to 8.5. The carriers were organically modified silica NP (SiNP) having 3-amino propyl and/or vinyl groups, liposome and serum protein. The results reveal that stability of curcumin formulated with SiNP functionalized with 3-amino propyl group (SiNP-VA) is significantly higher as compared to SiNP with only vinyl group (SiNP-V) and buffer but lower as compared to serum protein and liposome. However, fluorescence quantum yield (QY) is highest in SiNP-VA among all the nano formulations at pH 7.4 and below, which is attributed to the excited state interaction of curcumin with the amino groups of SiNP-VA. Results suggest that SiNP-VA could be an effective carrier for curcumin, which may have applications for imaging and drug delivery.

Insights into Interfacial Changes and Photoelectrochemical Stability of In(x)Ga(1-x)N (0001) Photoanode Surfaces in Liquid Environments.

PubMed

Caccamo, Lorenzo; Cocco, Giulio; Martín, Gemma; Zhou, Hao; Fundling, Sönke; Gad, Alaaeldin; Mohajerani, Matin Sadat; Abdelfatah, Mahmoud; Estradé, Sonia; Peiró, Francesca; Dziony, Wanja; Bremers, Heiko; Hangleiter, Andreas; Mayrhofer, Leonhard; Lilienkamp, Gerhard; Moseler, Michael; Daum, Winfried; Waag, Andreas

2016-03-01

The long-term stability of InGaN photoanodes in liquid environments is an essential requirement for their use in photoelectrochemistry. In this paper, we investigate the relationships between the compositional changes at the surface of n-type In(x)Ga(1-x)N (x ∼ 0.10) and its photoelectrochemical stability in phosphate buffer solutions with pH 7.4 and 11.3. Surface analyses reveal that InGaN undergoes oxidation under photoelectrochemical operation conditions (i.e., under solar light illumination and constant bias of 0.5 VRHE), forming a thin amorphous oxide layer having a pH-dependent chemical composition. We found that the formed oxide is mainly composed of Ga-O bonds at pH 7.4, whereas at pH 11.3 the In-O bonds are dominant. The photoelectrical properties of InGaN photoanodes are intimately related to the chemical composition of their surface oxides. For instance, after the formation of the oxide layer (mainly Ga-O bonds) at pH 7.4, no photocurrent flow was observed, whereas the oxide layer (mainly In-O bonds) at pH 11.3 contributes to enhance the photocurrent, possibly because of its reported high photocatalytic activity. Once a critical oxide thickness was reached, especially at pH 7.4, no significant changes in the photoelectrical properties were observed for the rest of the test duration. This study provides new insights into the oxidation processes occurring at the InGaN/liquid interface, which can be exploited to improve InGaN stability and enhance photoanode performance for biosensing and water-splitting applications.

Stability of buffer-free freeze-dried formulations: A feasibility study of a monoclonal antibody at high protein concentrations.

PubMed

Garidel, Patrick; Pevestorf, Benjamin; Bahrenburg, Sven

2015-11-01

We studied the stability of freeze-dried therapeutic protein formulations over a range of initial concentrations (from 40 to 160 mg/mL) and employed a variety of formulation strategies (including buffer-free freeze dried formulations, or BF-FDF). Highly concentrated, buffer-free liquid formulations of therapeutic monoclonal antibodies (mAbs) have been shown to be a viable alternative to conventionally buffered preparations. We considered whether it is feasible to use the buffer-free strategy in freeze-dried formulations, as an answer to some of the known drawbacks of conventional buffers. We therefore conducted an accelerated stability study (24 weeks at 40 °C) to assess the feasibility of stabilizing freeze-dried formulations without "classical" buffer components. Factors monitored included pH stability, protein integrity, and protein aggregation. Because the protein solutions are inherently self-buffering, and the system's buffer capacity scales with protein concentration, we included highly concentrated buffer-free freeze-dried formulations in the study. The tested formulations ranged from "fully formulated" (containing both conventional buffer and disaccharide stabilizers) to "buffer-free" (including formulations with only disaccharide lyoprotectant stabilizers) to "excipient-free" (with neither added buffers nor stabilizers). We evaluated the impacts of varying concentrations, buffering schemes, pHs, and lyoprotectant additives. At the end of 24 weeks, no change in pH was observed in any of the buffer-free formulations. Unbuffered formulations were found to have shorter reconstitution times and lower opalescence than buffered formulations. Protein stability was assessed by visual inspection, sub-visible particle analysis, protein monomer content, charge variants analysis, and hydrophobic interaction chromatography. All of these measures found the stability of buffer-free formulations that included a disaccharide stabilizer comparable to buffer-based formulations, especially at protein concentrations up to and including 115 mg/mL. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterization, stabilization and activity of uricase loaded in lipid vesicles.

PubMed

Tan, Q Y; Wang, N; Yang, H; Zhang, L K; Liu, S; Chen, L; Liu, J; Zhang, L; Hu, N N; Zhao, C J; Zhang, J Q

2010-01-15

Uricase-containing lipid vesicles (UOXLVs) were prepared by reverse-phase evaporation method with high efficiency and the characteristics of UOXLVs were described. The average size and zeta potential of UOXLVs obtained by the optimized formulation were 205.47 nm and -37.33 mV, respectively. Uricase was encapsulated in the alkaline aqueous phase of the lipid vesicle and the stability of its tetrameric structure was thus improved and its activity preserved. The storage stability of uricase in lipid vesicles was significantly increased compared to that of free uricase at 4 degrees C in borate buffer of pH 8.5. At 55 degrees C, free uricase was deactivated much more quickly especially at lower concentration predominantly due to enhanced dissociation of uricase into subunits. An intrinsic tryptophan of uricase recovered from the lipid vesicle thermally treated at 55 degrees C revealed that a partially denatured uricase molecule was stabilized through its hydrophobic interaction with lipid vesicle membrane. This interaction was depressed mainly by dissociation of uricase into subunits. At the physiological pH, significant increase of enzyme activity was found for the uricase entrapped in the lipid vesicles (1.8 times that of free uricase) at their respective optimum pH. The shift of optimum pH and increased uricolytic activity suggested the conformation change of the uricase during the entrapment process. The stability to proteolytic digestion was increased obviously by entrapping the uricase in the lipid vesicles. UOXLVs also showed relatively slower loss in activity compared with free uricase when treated with some chemical reagents. Lastly, in vitro study explicitly indicated that the uricase entrapped by UOXLVs possessed higher uricolytic activity than that of native uricase solution.

Allele-specific Characterization of Alanine: Glyoxylate Aminotransferase Variants Associated with Primary Hyperoxaluria

PubMed Central

Lage, Melissa D.; Pittman, Adrianne M. C.; Roncador, Alessandro; Cellini, Barbara; Tucker, Chandra L.

2014-01-01

Primary Hyperoxaluria Type 1 (PH1) is a rare autosomal recessive kidney stone disease caused by deficiency of the peroxisomal enzyme alanine: glyoxylate aminotransferase (AGT), which is involved in glyoxylate detoxification. Over 75 different missense mutations in AGT have been found associated with PH1. While some of the mutations have been found to affect enzyme activity, stability, and/or localization, approximately half of these mutations are completely uncharacterized. In this study, we sought to systematically characterize AGT missense mutations associated with PH1. To facilitate analysis, we used two high-throughput yeast-based assays: one that assesses AGT specific activity, and one that assesses protein stability. Approximately 30% of PH1-associated missense mutations are found in conjunction with a minor allele polymorphic variant, which can interact to elicit complex effects on protein stability and trafficking. To better understand this allele interaction, we functionally characterized each of 34 mutants on both the major (wild-type) and minor allele backgrounds, identifying mutations that synergize with the minor allele. We classify these mutants into four distinct categories depending on activity/stability results in the different alleles. Twelve mutants were found to display reduced activity in combination with the minor allele, compared with the major allele background. When mapped on the AGT dimer structure, these mutants reveal localized regions of the protein that appear particularly sensitive to interactions with the minor allele variant. While the majority of the deleterious effects on activity in the minor allele can be attributed to synergistic interaction affecting protein stability, we identify one mutation, E274D, that appears to specifically affect activity when in combination with the minor allele. PMID:24718375

[Comparison between colorimetry and HPLC on the stability test of roxithromycin].

PubMed

Wei, Z P; Mao, S R; Bi, D Z

2000-11-01

To compare the stability of roxithromycin in solutions of different pH. Roxithromycin solutions of different pH were prepared with water, simulate intestinal fluid (SIF) and simulate gastric fluid (SGF) shown to be the stability of these solutions were tested by colorimetry and HPLC. Roxithromycin was stable in water, SGF and SIF determined by colorimetry. However, it was found to be stable only in water and SIF but unstable in SGF as determined by HPLC. Roxithromycin is unstable in acidic medium like SGF. The metabolite of roxithromycin showed unfavorable interference on the assay of roxithromycin when colorimetry was used. Colorimetry can not be used for the determination and assay of roxithromycin in acidic solution like SGF.

Maillard-Reaction-Functionalized Egg Ovalbumin Stabilizes Oil Nanoemulsions.

PubMed

Liu, Gang; Yuan, Dan; Wang, Qi; Li, Wanrong; Cai, Jie; Li, Shuyi; Lamikanra, Olusola; Qin, Xinguang

2018-04-25

Egg white proteins are an excellent source of nutrition, with high biological and technological values. However, their limited functional properties prevent their widespread industrial applications. In this study, the ovalbumin functionality was improved via glycation by Maillard reaction with d-lactose. The free amino groups and sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile were determined, confirming that glycation occurred between ovalbumin and lactose. The emulsification of the conjugate was 2.69-fold higher than that of ovalbumin at pH 7.0 after glycation. The thermal stability also improved remarkably. The glycated protein products were used to form an oil-water nanoemulsion for polymethoxyflavone-rich aged orange peel oil. The resulting nanoemulsion showed good pH, thermal, and storage stabilities.

Structural stability of E. coli transketolase to temperature and pH denaturation.

PubMed

Jahromi, Raha R F; Morris, Phattaraporn; Martinez-Torres, Ruben J; Dalby, Paul A

2011-09-10

We have previously shown that the denaturation of TK with urea follows a non-aggregating though irreversible denaturation pathway in which the cofactor binding appears to become altered but without dissociating, then followed at higher urea by partial denaturation of the homodimer prior to any further unfolding or dissociation of the two monomers. Urea is not typically present during biocatalysis, whereas access to TK enzymes that retain activity at increased temperature and extreme pH would be useful for operation under conditions that increase substrate and product stability or solubility. To provide further insight into the underlying causes of its deactivation in process conditions, we have characterised the effects of temperature and pH on the structure, stability, aggregation and activity of Escherichia coli transketolase. The activity of TK was initially found to progressively improve after pre-incubation at increasing temperatures. Loss of activity at higher temperature and low pH resulted primarily from protein denaturation and subsequent irreversible aggregation. By contrast, high pH resulted in the formation of a native-like state that was only partially inactive. The apo-TK enzyme structure content also increased at pH 9 to converge on that of the holo-TK. While cofactor dissociation was previously proposed for high pH deactivation, the observed structural changes in apo-TK but not holo-TK indicate a more complex mechanism. Copyright © 2011 Elsevier B.V. All rights reserved.

[Effects of soil properties on the stabilization process of cadmium in Cd alone and Cd-Pb contaminated soils].

PubMed

Wu, Man; Xu, Ming-Gang; Zhang, Wen-Ju; Wu, Hai-Wen

2012-07-01

In order to clarify the effects of soil properties on the stabilization process of the cadmium (Cd) added, 11 different soils were collected and incubated under a moisture content of 65%-70% at 25 degrees C. The changes of available Cd contents with incubation time (in 360 days) in Cd and Cd-Pb contaminated treatments were determined. The stabilization process was simulated using dynamic equations. The results showed that after 1.0 mg x kg(-1) Cd or 500 mg x kg(-1) Pb + 1.0 mg x kg(-1) Cd were added into the soil, the available Cd content decreased rapidly during the first 15 days, and then the decreasing rate slowed down, with an equilibrium content reached after 60 days' incubation. In Cd-Pb contaminated soils, the presence of Pb increased the content of available Cd. The stabilization process of Cd could be well described by the second-order equation and the first order exponential decay; meanwhile, dynamic parameters including equilibrium content and stabilization velocity were used to characterize the stabilization process of Cd. These two key dynamic parameters were significantly affected by soil properties. Correlation analysis and stepwise regression suggested that high pH and high cation exchange capacity (CEC) significantly retarded the availability of Cd. High pH had the paramount effect on the equilibrium content. The stabilization velocity of Cd was influenced by the soil texture. It took shorter time for Cd to get stabilized in sandy soil than in the clay.

Stability and maturity of biowaste composts derived by small municipalities: Correlation among physical, chemical and biological indices.

PubMed

Oviedo-Ocaña, E R; Torres-Lozada, P; Marmolejo-Rebellon, L F; Hoyos, L V; Gonzales, S; Barrena, R; Komilis, D; Sanchez, A

2015-10-01

Stability and maturity are important criteria to guarantee the quality of a compost that is applied to agriculture or used as amendment in degraded soils. Although different techniques exist to evaluate stability and maturity, the application of laboratory tests in municipalities in developing countries can be limited due to cost and application complexities. In the composting facilities of such places, some classical low cost on-site tests to monitor the composting process are usually implemented; however, such tests do not necessarily clearly identify conditions of stability and maturity. In this article, we have applied and compared results of stability and maturity tests that can be easily employed on site (i.e. temperature, pH, moisture, electrical conductivity [EC], odor and color), and of tests that require more complex laboratory techniques (volatile solids, C/N ratio, self-heating, respirometric index, germination index [GI]). The evaluation of the above was performed in the field scale using 2 piles of biowaste applied compost. The monitoring period was from day 70 to day 190 of the process. Results showed that the low-cost tests traditionally employed to monitor the composting process on-site, such as temperature, color and moisture, do not provide consistent determinations with the more complex laboratory tests used to assess stability (e.g. respiration index, self-heating, volatile solids). In the case of maturity tests (GI, pH, EC), both the on-site tests (pH, EC) and the laboratory test (GI) provided consistent results. Although, stability was indicated for most of the samples, the maturity tests indicated that products were consistently immature. Thus, a stable product is not necessarily mature. Conclusively, the decision on the quality of the compost in the installations located in developing countries requires the simultaneous use of a combination of tests that are performed both in the laboratory and on-site. Copyright © 2015 Elsevier Ltd. All rights reserved.

Validation and application of a stability-indicating HPLC method for the in vitro determination of gastric and intestinal stability of venlafaxine.

PubMed

Asafu-Adjaye, Ebenezer B; Faustino, Patrick J; Tawakkul, Mobin A; Anderson, Lawrence W; Yu, Lawrence X; Kwon, Hyojong; Volpe, Donna A

2007-04-11

Gastrointestinal stability of venlafaxine was evaluated in vitro in simulated gastric (SGF) and intestinal (SIF) fluids using a stability indicating HPLC method. The method was validated using a 5 microm Ascentis C18 column (150 mm x 4.6 mm) and mobile phase consisting of 30% acetonitrile in 20 mM potassium phosphate buffer (pH 6.5) delivered isocratically at a flow rate of 1 mL/min with UV detection at 228 nm. Venlafaxine in USP simulated gastric and intestinal fluids (0.4 mg/mL) was incubated at 37 degrees C in a shaking water bath. The gastric stability study samples were assayed at 0, 15, 30 and 60 min intervals while sampling for the intestinal stability study was at 0, 1, 2 and 3 h. System suitability determinations gave R.S.D.s of 0.68, 0.5 and 3.9% for retention factor (k'), peak area and tailing factor, respectively. The method was shown to be accurate, precise, specific, and linear over the analytical range. Intra- and inter-day precision was <5.3%. Forced degradation studies of drug substance in basic media at 70 degrees C as well as in H2O2 for 1 h and ultra-violet photostability studies at 255 and 365 nm for 24 h did not produce any detectable degradation products. Forced degradation studies of drug substance in acidic media at 70 degrees C for 1 h produced the dehydro-venlafaxine degradant. Venlafaxine was stable in SGF (pH approximately 1.2) for the 1-h incubation period and in SIF (pH 6.8) up to 3 h with <1.5% relative difference (RD) between the amount of drug added and that found for all time points. This stability experiment in simulated gastric and intestinal fluids suggests that drug loss in the gastrointestinal tract takes place by membrane permeation rather than a degradation process.

Effects of pH-Shift Processing and Microbial Transglutaminase on the Gel and Emulsion Characteristics of Porcine Myofibrillar System

PubMed Central

Hong, Geun-Pyo; Chun, Ji-Yeon; Jo, Yeon-Ji

2014-01-01

This study investigated the effects of microbial transglutaminase (MTGase) and pH-shift processing on the functional properties of porcine myofibrillar proteins (MP). The pH-shift processing was carried out by decreasing the pH of MP suspension to 3.0, followed by re-adjustment to pH 6.2. The native (CM) and pH-shifted MP (PM) was reacted with and without MTGase, and the gelling and emulsion characteristics were compared. To compare the pH-shifted MTGase-treated MP (PT), deamidation (DM) was conducted by reacting MTGase with MP at pH 3.0. Rigid thermal gel was produced by MTGase-treated native MP (CT) and PT. PM and DM showed the lowest storage modulus (G') at the end of thermal scanning. Both MTGase and pH-shifting produced harder MP gel, and the highest gel strength was obtained in PT. All treatments yielded lower than CM, and CT showed significantly higher yield than PM and DM treatments. For emulsion characteristics, pH-shifting improved the emulsifying ability of MP-stabilized emulsion, while the treatments had lower emulsion stability. PM-stabilized emulsion exhibited the lowest creaming stability among all treatments. The emulsion stability could be improved by the usage of MTGase. The results indicated that pH-shifting combined with MTGase had a potential application to modify or improve functional properties of MP in manufacturing of meat products. PMID:26760940

ARSENIC CONTAMINATION AT THE INDUSTRI-PLEX SUPERFUND SITE, WOBURN, MA

EPA Science Inventory

Arsenate coprecipitated with hydrous ferric oxide (HFO) was stabilized against dissolution during transformation of HFO to more crystalline iron (hydr)oxides. The rate of arsenate stabilization approximately coincided with the rate of HFO transformation at pH 6 and 40 ?C. Compa...

Coagulation removal of humic acid-stabilized carbon nanotubes from water by PACl: influences of hydraulic condition and water chemistry.

PubMed

Ma, Si; Liu, Changli; Yang, Kun; Lin, Daohui

2012-11-15

Discharged carbon nanotubes (CNTs) can adsorb the widely-distributed humic acid (HA) in aquatic environments and thus be stabilized. HA-stabilized CNTs can find their way into and challenge the potable water treatment system. This study investigated the efficiency of coagulation and sedimentation techniques in the removal of the HA-stabilized multi-walled carbon nanotubes (MWCNTs) using polyaluminum chloride (PACl) as a coagulant, with a focus on the effects of hydraulic conditions and water chemistry. Stirring speeds in the mixing and reacting stages were gradually changed to examine the effect of the hydraulic conditions on the removal rate. The stirring speed in the reacting stage affected floc formation and thereby had a greater impact on the removal rate than the stirring speed in the mixing stage. Water chemistry factors such as pH and ionic strength had a significant effect on the stability of MWCNT suspension and the removal efficiency. Low pH (4-7) was favorable for saving the coagulant and maintaining high removal efficiency. High ionic strength facilitated the destabilization of the HA-stabilized MWCNTs and thereby lowered the required PACl dosage for the coagulation. However, excessively high ionic strength (higher than the critical coagulation concentration) decreased the maximum removal rate, probably by inhibiting ionic activity of PACl hydrolyzate in water. These results are expected to shed light on the potential improvement of coagulation removal of aqueous stabilized MWCNTs in water treatment systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Probing the pH sensitivity of R-phycoerythrin: investigations of active conformational and functional variation.

PubMed

Liu, Lu-Ning; Su, Hai-Nan; Yan, Shi-Gan; Shao, Si-Mi; Xie, Bin-Bin; Chen, Xiu-Lan; Zhang, Xi-Ying; Zhou, Bai-Cheng; Zhang, Yu-Zhong

2009-07-01

Crystal structures of phycobiliproteins have provided valuable information regarding the conformations and amino acid organizations of peptides and chromophores, and enable us to investigate their structural and functional relationships with respect to environmental variations. In this work, we explored the pH-induced conformational and functional dynamics of R-phycoerythrin (R-PE) by means of absorption, fluorescence and circular dichroism spectra, together with analysis of its crystal structure. R-PE presents stronger functional stability in the pH range of 3.5-10 compared to the structural stability. Beyond this range, pronounced functional and structural changes occur. Crystal structure analysis shows that the tertiary structure of R-PE is fixed by several key anchoring points of the protein. With this specific association, the fundamental structure of R-PE is stabilized to present physiological spectroscopic properties, while local variations in protein peptides are also allowed in response to environmental disturbances. The functional stability and relative structural sensitivity of R-PE allow environmental adaptation.

Synthesis of Cross-Linked Polymeric Micelle pH Nanosensors: An Investigation of Design Flexibility.

PubMed

Kumar, E K Pramod; Jølck, Rasmus I; Andresen, Thomas L

2015-09-01

The design flexibility that polymeric micelles offer in the fabrication of optical nanosensors for ratiometric pH measurements is investigated. pH nanosensors based on polymeric micelles are synthesized either by a mixed-micellization approach or by a postmicelle modification strategy. In the mixed-micellization approach, self-assembly of functionalized unimers followed by shell cross-linking by copper-catalyzed azide-alkyne cycloaddition (CuAAC) results in stabilized cRGD-functionalized micelle pH nanosensors. In the postmicelle modification strategy, simultaneous cross-linking and fluorophore conjugation at the micelle shell using CuAAC results in a stabilized micelle pH nanosensor. Compared to the postmicelle modification strategy, the mixed-micellization approach increases the control of the overall composition of the nanosensors. Both approaches provide stable nanosensors with similar pKa profiles and thereby nanosensors with similar pH sensitivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel inexpensive fungi proteases: Production by solid state fermentation and characterization.

PubMed

Novelli, Paula Kern; Barros, Margarida Maria; Fleuri, Luciana Francisco

2016-05-01

A comparative study was carried out for proteases production using agroindustrial residues as substrate for solid state fermentation (SSF) of several fungal strains. High protease production was observed for most of the microorganisms studied, as well as very different biochemical characteristics, including activities at specific temperatures and a wide range of pH values. The enzymes produced were very different regarding optimum pH and they showed stability at 50 °C. Aspergillus oryzae showed stability at all pH values studied. Penicillium roquefortii and Aspergillus flavipes presented optimum activity at temperatures of 50 °C and 90 °C, respectively. Lyophilized protease from A. oryzae reached 1251.60 U/g and yield of 155010.66 U/kg of substrate. Therefore, the substrate as well as the microorganism strain can modify the biochemical character of the enzyme produced. The high protease activity and stability established plus the low cost of substrates, make these fungal proteases potential alternatives for the biotechnological industry. Copyright © 2015 Elsevier Ltd. All rights reserved.

SF2312 is a natural phosphonate inhibitor of Enolase

PubMed Central

Maxwell, David; Lin, Yu-Hsi; Hammoudi, Naima; Peng, Zhenghong; Pisaneschi, Federica; Link, Todd M.; Lee, Gilbert R.; Sun, Duoli; Prasad, Basvoju A. Bhanu; Di Francesco, Maria Emilia; Czako, Barbara; Asara, John M.; Wang, Y. Alan; Bornmann, William; DePinho, Ronald A.; Muller, Florian L.

2016-01-01

Despite being critical for energy generation in most forms of life, few if any microbial antibiotics specifically inhibit glycolysis. To develop a specific inhibitor of the glycolytic enzyme Enolase 2 for the treatment of cancers with deletion of Enolase 1, we modeled the synthetic tool compound inhibitor, Phosphonoacetohydroxamate (PhAH) into the active site of human ENO2. A ring-stabilized analogue of PhAH, with the hydroxamic nitrogen linked to the alpha-carbon by an ethylene bridge, was predicted to increase binding affinity by stabilizing the inhibitor in a bound conformation. Unexpectedly, a structure based search revealed that our hypothesized back-bone-stabilized PhAH bears strong similarity to SF2312, a phosphonate antibiotic of unknown mode of action produced by the actinomycete Micromonospora, which is active under anaerobic conditions. Here, we present multiple lines of evidence, including a novel X-ray structure, that SF2312 is a highly potent, low nM inhibitor of Enolase. PMID:27723749

Optimization of ultrasound-assisted extraction of pectinase enzyme from guava (Psidium guajava) peel: Enzyme recovery, specific activity, temperature, and storage stability.

PubMed

Amid, Mehrnoush; Murshid, Fara Syazana; Manap, Mohd Yazid; Islam Sarker, Zaidul

2016-01-01

This study aimed to investigate the effects of the ultrasound-assisted extraction conditions on the yield, specific activity, temperature, and storage stability of the pectinase enzyme from guava peel. The ultrasound variables studied were sonication time (10-30 min), ultrasound temperature (30-50 °C), pH (2.0-8.0), and solvent-to-sample ratio (2:1 mL/g to 6:1 mL/g). The main goal was to optimize the ultrasound-assisted extraction conditions to maximize the recovery of pectinase from guava peel with the most desirable enzyme-specific activity and stability. Under the optimum conditions, a high yield (96.2%), good specific activity (18.2 U/mg), temperature stability (88.3%), and storage stability (90.3%) of the extracted enzyme were achieved. The optimal conditions were 20 min sonication time, 40 °C temperature, at pH 5.0, using a 4:1 mL/g solvent-to-sample ratio. The study demonstrated that optimization of ultrasound-assisted process conditions for the enzyme extraction could improve the enzymatic characteristics and yield of the enzyme.

Stability of Prednisone in Oral Mix Suspending Vehicle.

PubMed

Friciu, Mihaela; Plourde, Kevin; Leclair, Grégoire; Danopoulos, Panagiota; Savji, Taslim

2015-01-01

The stability of prednisone (5 mg/mL) formulated as a suspension in Oral Mix vehicle was evaluated. Oral Mix is a novel oral, dye-free suspending vehicle developed by Medisca Pharmaceutique Inc. for preparation of extemporaneous dosage forms. This drug was chosen based on its high frequency of prescription among the pediatric population. Suspensions were prepared from both pure active and commercial tablets utilizing two different container closures: amber glass bottles and polypropylene syringes (PreciseDose Dispenser Medisca Pharmaceutique Inc.). Formulations were stored at 5°C or 25°C and organoleptic properties, pH, and concentration were evaluated at predetermined time points up to 90 days. Validated stability-indicating high-performance liquid chromatography methods were developed. Beyond-use date was evaluated by statistical analysis of the overall degradation trend. Prednisone was stable for at least 90 days at 25°C. No changes in organoleptic properties or pH were observed for either of the formulations, and the global stability was roughly equivalent and sometimes superior to the stability of the same drugs in other previously used vehicles. Thus, Oral Mix was found to be a suitable dye-free vehicle for extemporaneous formulations.

An investigation of the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in authentic urine samples.

PubMed

Skopp, Gisela; Pötsch, Lucia

2004-01-01

Preanalytical stability of a drug and its major metabolites is an important consideration in pharmacokinetic studies or whenever the analyte pattern is used to estimate drug habits. Firstly, the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH, THCCOOglu) in authentic urine samples was investigated. Random urine samples of cannabis users (n = 38) were stored at -20, 4, and 20 degrees C up to 15 days and up to 5 days at 40 degrees C, and alterations of the analyte pattern during storage were followed by liquid chromatography-tandem mass spectrometry. Secondly, the influence of pH (range 5.0-8.0) on the stability of the analytes was studied using spiked urine to elucidate the results obtained from authentic samples. In authentic urine samples, the initial pH ranged from 5.1 to 8.8. The glucuronide was found to be highly labile at a storage temperature of 4 degrees C and above. Initially, 18 urine samples tested positive for THCCOOH. After 2 days storage at 20 degrees C, THCCOOH was detectable in a further 4 samples, and 7 more samples tested positive for THCCOOH (5-81 ng/mL) after 15 days. Depending on time and temperature, the glucuronide concentration decreased, resulting in an increase of THCCOOH concentration. However, a loss in mean total THCCOOH concentration was found, which was significantly higher in deteriorated samples than in samples without signs of deterioration after 15 days of storage at 20 degrees C. In the drug-free urine sample separately spiked with THCCOOglu or THCCOOH, the investigations on the stability of the target analytes at various pH values revealed that THCCOOH was stable at pH 5.0. At higher pH values, its concentration slightly decreased with time, and about 69% of the initial THCCOOH concentration was still present at pH 8.0 on day 5. THCCOOglu concentrations rapidly decreased with increasing pH value. For example, only 72% of the initial THCCOOglu concentration could be detected at pH 5.0 on day 1. Degradation of the glucuronide resulted in formation of THCCOOH, which was observed even at pH 5.0. In light of the present findings, advanced forensic interpretations based on the presence of THCCOOH or the pattern of THCCOOH and THCCOOglu in stored urine samples seems questionable.

Effects of anticaking agents and relative humidity on the physical and chemical stability of powdered vitamin C.

PubMed

Lipasek, Rebecca A; Taylor, Lynne S; Mauer, Lisa J

2011-09-01

Vitamin C is an essential nutrient that is widely used by the food industry in the powder form for both its nutritional and functional properties. However, vitamin C is deliquescent, and deliquescence has been linked to physical and chemical instabilities. Anticaking agents are often added to powder systems to delay or prevent caking, but little is known about their effect on the chemical stability of powders. In this study, various anticaking agents (calcium phosphate, calcium silicate, calcium stearate, corn starch, and silicon dioxide) were combined with sodium ascorbate at 2% and 50% w/w ratios and stored at various relative humidities (23%, 43%, 64%, 75%, 85%, and 98% RHs). Chemical and physical stability and moisture sorption were monitored over time. Additionally, saturated solution samples were stored at various pHs to determine the effect of surface pH and dissolution on the vitamin degradation rate. Storage RH, time, and anticaking agent type and ratio all significantly affected (P < 0.05) moisture sorption and vitamin C stability. Silicon dioxide and calcium silicate (50% w/w) and calcium stearate (at both ratios) were the only anticaking agents to improve the physical stability of powdered sodium ascorbate while none of the anticaking agents improved its chemical stability. However, corn starch and calcium stearate had the least adverse effect on chemical stability. Dissolution rate and pH were also important factors affecting the chemical and physical stability of the powders. Therefore, monitoring storage environmental conditions and anticaking agent usage are important for understanding the stability of vitamin C. Anticaking agent type and ratio significantly affected the physical and chemical stability of vitamin C over time and over a range of RHs. No anticaking agent improved the chemical stability of the vitamin, and most caused an increase in chemical degradation even if physical stability was improved. It is possible that anticaking agents would greatly affect other chemically labile deliquescent ingredients, and therefore, anticaking agent usage and storage conditions should be monitored in blended powder systems. © 2011 Institute of Food Technologists®

Spray dried microparticles of chia oil using emulsion stabilized by whey protein concentrate and pectin by electrostatic deposition.

PubMed

Noello, C; Carvalho, A G S; Silva, V M; Hubinger, M D

2016-11-01

Chia seed oil has a high content of α-linolenic acid (60%) and linoleic acid (20%). Use of this oil in different products is limited due to its liquid state, and the presence of insaturation is a trigger for oxidation. In this context, to facilitate the incorporation of chia oil in food products and increase its protection against oxidation, the aim of this work was to produce chia oil microparticles by spray drying using emulsions stabilized by whey protein concentrate (ζ-potential +13.4 at pH3.8) and pectin (ζ-potential -40.4 at pH3.8) through the electrostatic layer-by-layer deposition technique and emulsions prepared with only whey protein concentrate. Emulsions stabilized by whey protein concentrate and stabilized by whey protein concentrate-pectin were prepared using maltodextrin (10 DE) and modified starch (Hi-Cap® 100). They were characterized in relation to stability, droplet size, ζ-Potential and optical microscopy. The microparticles were characterized in relation to moisture content, water activity, particle size, microstructure and oxidative stability by the Rancimat method. Emulsions stabilized by whey protein concentrate-pectin with added maltodextrin 10 DE and emulsions stabilized by whey protein concentrate with added modified starch (Hi-Cap® 100) were stable after 24h. Emulsions stabilized by whey protein concentrate and by whey protein concentrate-pectin showed droplets with mean diameter ranging from 0.80 to 1.31μm, respectively and ζ-potential varying from -6.9 to -27.43mV, respectively. After spray drying, the microparticles showed an mean diameter ranging from 7.00 to 9.00μm. All samples presented high encapsulation efficiency values, above 99%. Microparticles produced with modified starch showed a smoother spherical surface than particles with maltodextrin 10 DE, which presented a wrinkled surface. All microparticles exhibited higher oxidative stability than chia oil in pure form. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Influence of Arginine on the Response of Enamel Matrix Derivative (EMD) Proteins to Thermal Stress: Towards Improving the Stability of EMD-Based Products

PubMed Central

Bolisetty, Sreenath; Marascio, Matteo; Gemperli Graf, Anja; Garamszegi, Laszlo; Mezzenga, Raffaele; Fischer, Peter; Månson, Jan-Anders

2015-01-01

In a current procedure for periodontal tissue regeneration, enamel matrix derivative (EMD), which is the active component, is mixed with a propylene glycol alginate (PGA) gel carrier and applied directly to the periodontal defect. Exposure of EMD to physiological conditions then causes it to precipitate. However, environmental changes during manufacture and storage may result in modifications to the conformation of the EMD proteins, and eventually premature phase separation of the gel and a loss in therapeutic effectiveness. The present work relates to efforts to improve the stability of EMD-based formulations such as Emdogain™ through the incorporation of arginine, a well-known protein stabilizer, but one that to our knowledge has not so far been considered for this purpose. Representative EMD-buffer solutions with and without arginine were analyzed by 3D-dynamic light scattering, UV-Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy at different acidic pH and temperatures, T, in order to simulate the effect of pH variations and thermal stress during manufacture and storage. The results provided evidence that arginine may indeed stabilize EMD against irreversible aggregation with respect to variations in pH and T under these conditions. Moreover, stopped-flow transmittance measurements indicated arginine addition not to suppress precipitation of EMD from either the buffers or the PGA gel carrier when the pH was raised to 7, a fundamental requirement for dental applications. PMID:26670810

The Influence of Arginine on the Response of Enamel Matrix Derivative (EMD) Proteins to Thermal Stress: Towards Improving the Stability of EMD-Based Products.

PubMed

Apicella, Alessandra; Heunemann, Peggy; Bolisetty, Sreenath; Marascio, Matteo; Gemperli Graf, Anja; Garamszegi, Laszlo; Mezzenga, Raffaele; Fischer, Peter; Plummer, Christopher J; Månson, Jan-Anders

2015-01-01

In a current procedure for periodontal tissue regeneration, enamel matrix derivative (EMD), which is the active component, is mixed with a propylene glycol alginate (PGA) gel carrier and applied directly to the periodontal defect. Exposure of EMD to physiological conditions then causes it to precipitate. However, environmental changes during manufacture and storage may result in modifications to the conformation of the EMD proteins, and eventually premature phase separation of the gel and a loss in therapeutic effectiveness. The present work relates to efforts to improve the stability of EMD-based formulations such as Emdogain™ through the incorporation of arginine, a well-known protein stabilizer, but one that to our knowledge has not so far been considered for this purpose. Representative EMD-buffer solutions with and without arginine were analyzed by 3D-dynamic light scattering, UV-Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy at different acidic pH and temperatures, T, in order to simulate the effect of pH variations and thermal stress during manufacture and storage. The results provided evidence that arginine may indeed stabilize EMD against irreversible aggregation with respect to variations in pH and T under these conditions. Moreover, stopped-flow transmittance measurements indicated arginine addition not to suppress precipitation of EMD from either the buffers or the PGA gel carrier when the pH was raised to 7, a fundamental requirement for dental applications.

Proposal of a sequential treatment methodology for the safe reuse of oil sludge-contaminated soil.

PubMed

Mater, L; Sperb, R M; Madureira, L A S; Rosin, A P; Correa, A X R; Radetski, C M

2006-08-25

In this study sequential steps were used to treat and immobilize oil constituents of an oil sludge-contaminated soil. Initially, the contaminated soil was oxidized by a Fenton type reaction (13 wt% for H(2)O(2); 10mM for Fe(2+)). The oxidative treatment period of 80 h was carried out under three different pH conditions: 20 h at pH 6.5, 20 h at pH 4.5, and 40 h at pH 3.0. The oxidized contaminated sample (3 kg) was stabilized and solidified for 2h with clay (1 kg) and lime (2 kg). Finally, this mixture was solidified by sand (2 kg) and Portland cement (4 kg). In order to evaluate the efficiency of different processes to treat and immobilize oil contaminants of the oil sludge-contaminated soil, leachability and solubility tests were performed and extracts were analyzed according to the current Brazilian waste regulations. Results showed that the Fenton oxidative process was partially efficient in degrading the oil contaminants in the soil, since residual concentrations were found for the PAH and BTEX compounds. Leachability tests showed that clay-lime stabilization/solidification followed by Portland cement stabilization/solidification was efficient in immobilizing the recalcitrant and hazardous constituents of the contaminated soil. These two steps stabilization/solidification processes are necessary to enhance environmental protection (minimal leachability) and to render final product economically profitable. The treated waste is safe enough to be used on environmental applications, like roadbeds blocks.

RATES OF HYDROUS FERRIC OXIDE CRYSTALLIZATION AND THE INFLUENCE ON COPRECIPITATED ARSENATE

EPA Science Inventory

Arsenate coprecipitated with hydrous ferric oxide (HFO) was stabilized against dissolution during transformation of HFO to more crystalline iron (hydr)oxides. The rate of arsenate stabilization approximately coincided with the rate of HFO transformation at pH 6 and 40 ?C. Compa...

Immobilization and stabilization of pectinase by multipoint attachment onto an activated agar-gel support.

PubMed

Li, Tuoping; Li, Suhong; Wang, Na; Tain, Lirui

2008-08-15

Pectinase was immobilized on an activated agar-gel support by multipoint attachment. The maximal activity of immobilized pectinase was obtained at 5°C, pH 3.6, with a 24h reaction time at an enzyme dose of 0.52mg protein/g gel, and the gel was activated with 1.0M glycidol. These conditions increased the thermal stability of the immobilized pectinase 19-fold compared with the free enzyme at 65°C. The optimal temperature for pectinase activity changed from 40 to 50°C after immobilization; however, the optimal pH remained unchanged. The immobilized enzyme also exhibited great operational stability, and an 81% residual activity was observed in the immobilized enzyme after 10 batch reactions. Copyright © 2008 Elsevier Ltd. All rights reserved.

Effect of glycine on pH changes and protein stability during freeze-thawing in phosphate buffer systems.

PubMed

Pikal-Cleland, Katherine A; Cleland, Jeffrey L; Anchordoquy, Thomas J; Carpenter, John F

2002-09-01

Previous studies have established that the selective precipitation of a less soluble buffer component during freezing can induce a significant pH shift in the freeze concentrate. During freezing of sodium phosphate solutions, crystallization of the disodium salt can produce a pH decrease as great as 3 pH units which can dramatically affect protein stability. The objective of our study was to determine how the presence of glycine (0-500 mM), a commonly used bulking agent in pharmaceutical protein formulations, affects the pH changes normally observed during freezing in sodium phosphate buffer solutions and to determine whether these pH changes contribute to instability of model proteins in glycine/phosphate formulations. During freezing in sodium phosphate buffers, the presence of glycine significantly influenced the pH. Glycine at the lower concentrations (< or = 50 mM) suppressed the pH decrease normally observed during freezing in 10 and 100 mM sodium phosphate buffer, possibly by reducing the nucleation rate of salt and thereby decreasing the extent of buffer salt crystallization. The presence of glycine at higher concentration (> 100 mM) in the sodium phosphate buffer resulted in a more complete crystallization of the disodium salt as indicated by the frozen pH values closer to the equilibrium value (pH 3.6). Although high concentrations of glycine can facilitate more buffer salt crystallization and these pH shifts may prove to be potentially damaging to the protein, glycine, in its amorphous state, can also act to stabilize a protein via the preferential exclusion mechanism. Copyright 2002 Wiley-Liss Inc.

Stability of Acetazolamide, Baclofen, Dipyridamole, Mebeverine Hydrochloride, Propylthiouracil, Quinidine Sulfate, and Topiramate Oral Suspensions in SyrSpend SF PH4.

PubMed

Ferreira, Anderson de Oliveira; Polonini, Hudson; da Silva, Sharlene Loures; Aglio, Natália Cristina Buzinari; Abreu, Jordana; Fernandes, Brandão Marcos Antônio

2017-01-01

The objective of this study was to evaluate the stability of 7 commonly used active pharmaceutical ingredients compounded in oral suspensions using an internationally used suspending vehicle (SyrSpend SF PH4): acetazolamide 25.0 mg/mL, baclofen 10.0 mg/mL, dipyridamole 10.0 mg/mL, mebeverine hydrochloride 10.0 mg/mL, propylthiouracil 5.0 mg/mL, quinidine sulfate 10.0 mg/mL, and topiramate 5.0 mg/mL. All suspensions were stored both at controlled refrigerated (2°C to 8°C) and room temperature (20°C to 25°C). Stability was assessed by measuring the percentage recovery at varying time points throughout a 90-day period. Active pharmaceutical ingredient quantification was performed by ultraviolet (UV) high-performance liquid chromatography, via a stability-indicating method. Given the percentage of recovery of the active pharmaceutical ingredients within the suspensions, the beyond-use date of the final products (active pharmaceutical ingredient + vehicle) was at least 90 days for all suspensions with regards to both temperatures. This suggests that SyrSpend SF PH4 is suitable for compounding active pharmaceutical ingredients from different pharmacological classes. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Pediatric oral solutions with propranolol hydrochloride for extemporaneous compounding: the formulation and stability study.

PubMed

Klovrzová, Sylva; Zahálka, Lukáš; Matysová, Ludmila; Horák, Petr; Sklubalová, Zdenka

2013-02-01

The aim of this study is to formulate an extemporaneous pediatric oral solution of propranolol hydrochloride (PRO) 2 mg/ml for the therapy of infantile haemangioma or hypertension in a target age group of 1 month to school children and to evaluate its stability. A citric acid solution and/or a citrate-phosphate buffer solution, respectively, were used as the vehicles to achieve pH value of about 3, optimal for the stability of PRO. In order to mask the bitter taste of PRO, simple syrup was used as the sweetener. All solutions were stored in tightly closed brown glass bottles at 5 ± 3 °C and/or 25 ± 3 °C, respectively. The validated HPLC method was used to evaluate the concentration of PRO and a preservative, sodium benzoate, at time intervals of 0-180 days. All preparations were stable at both storage temperatures with pH values in the range of 2.8-3.2. According to pharmacopoeial requirements, the efficacy of sodium benzoate 0.05 % w/v was proved (Ph.Eur., 5.1.3). The preparation formulated with the citrate-phosphate buffer, in our experience, had better palatability than that formulated with the citric acid solution. propranolol hydrochloride pediatric preparation extemporaneous preparation solution stability testing HPLC.

Effects of pH and Iminosugar Pharmacological Chaperones on Lysosomal Glycosidase Structure and Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lieberman, Raquel L.; D’aquino, J. Alejandro; Ringe, Dagmar

2009-06-05

Human lysosomal enzymes acid-{beta}-glucosidase (GCase) and acid-{alpha}-galactosidase ({alpha}-Gal A) hydrolyze the sphingolipids glucosyl- and globotriaosylceramide, respectively, and mutations in these enzymes lead to the lipid metabolism disorders Gaucher and Fabry disease, respectively. We have investigated the structure and stability of GCase and {alpha}-Gal A in a neutral-pH environment reflective of the endoplasmic reticulum and an acidic-pH environment reflective of the lysosome. These details are important for the development of pharmacological chaperone therapy for Gaucher and Fabry disease, in which small molecules bind mutant enzymes in the ER to enable the mutant enzyme to meet quality control requirements for lysosomal trafficking.more » We report crystal structures of apo GCase at pH 4.5, at pH 5.5, and in complex with the pharmacological chaperone isofagomine (IFG) at pH 7.5. We also present thermostability analysis of GCase at pH 7.4 and 5.2 using differential scanning calorimetry. We compare our results with analogous experiments using {alpha}-Gal A and the chaperone 1-deoxygalactonijirimycin (DGJ), including the first structure of {alpha}-Gal A with DGJ. Both GCase and {alpha}-Gal A are more stable at lysosomal pH with and without their respective iminosugars bound, and notably, the stability of the GCase-IFG complex is pH sensitive. We show that the conformations of the active site loops in GCase are sensitive to ligand binding but not pH, whereas analogous galactose- or DGJ-dependent conformational changes in {alpha}-Gal A are not seen. Thermodynamic parameters obtained from {alpha}-Gal A unfolding indicate two-state, van't Hoff unfolding in the absence of the iminosugar at neutral and lysosomal pH, and non-two-state unfolding in the presence of DGJ. Taken together, these results provide insight into how GCase and {alpha}-Gal A are thermodynamically stabilized by iminosugars and suggest strategies for the development of new pharmacological chaperones for lysosomal storage disorders.« less

Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties.

PubMed

Boguta, Patrycja; Sokołowska, Zofia

2016-01-01

The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic acids with zinc.

Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties

PubMed Central

Boguta, Patrycja; Sokołowska, Zofia

2016-01-01

The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic acids with zinc. PMID:27077915

Engineering of acidic O/W emulsions with pectin.

PubMed

Alba, K; Sagis, L M C; Kontogiorgos, V

2016-09-01

Pectins with distinct molecular design were isolated by aqueous extraction at pH 2.0 or 6.0 and were examined in terms of their formation and stabilisation capacity of model n-alkane-in-water emulsions at acidic pH (pH 2.0). The properties and stability of the resulting emulsions were examined by means of droplet size distribution analysis, Lifshitz-Slyozov-Wagner modelling, bulk rheology, interfacial composition analysis, large-amplitude oscillatory surface dilatational rheology, electrokinetic analysis and fluorescence microscopy. Both pectin preparations were able to emulsify alkanes in water but exhibited distinct ageing characteristics. Emulsions prepared using pectin isolated at pH 6.0 were remarkably stable with respect to droplet growth after thirty days of ageing, while those prepared with pectin isolated at pH 2.0 destabilised rapidly. Examination of chemical composition of interfacial layers indicated multi-layered adsorption of pectins at the oil-water interface. The higher long-term stability of emulsions prepared with pectin isolated at high pH is attributed to mechanically stronger interfaces, the highly branched nature and the low hydrodynamic volume of the chains that result in effective steric stabilisation whereas acetyl and methyl contents do not contribute to the long-term stability. The present work shows that it is possible by tailoring the fine structure of pectin to engineer emulsions that operate in acidic environments. Copyright © 2016 Elsevier B.V. All rights reserved.

The matrix gene segment destabilizes the acid and thermal stability of the hemagglutinin of pandemic live attenuated influenza virus vaccines.

PubMed

O'Donnell, Christopher D; Vogel, Leatrice; Matsuoka, Yumiko; Jin, Hong; Subbarao, Kanta

2014-11-01

The threat of future influenza pandemics and their potential for rapid spread, morbidity, and mortality has led to the development of pandemic vaccines. We generated seven reassortant pandemic live attenuated influenza vaccines (pLAIVs) with the hemagglutinin (HA) and neuraminidase (NA) genes derived from animal influenza viruses on the backbone of the six internal protein gene segments of the temperature sensitive, cold-adapted (ca) A/Ann Arbor/60 (H2N2) virus (AA/60 ca) of the licensed seasonal LAIV. The pLAIV viruses were moderately to highly restricted in replication in seronegative adults; we sought to determine the biological basis for this restriction. Avian influenza viruses generally replicate at higher temperatures than human influenza viruses and, although they shared the same backbone, the pLAIV viruses had a lower shutoff temperature than seasonal LAIV viruses, suggesting that the HA and NA influence the degree of temperature sensitivity. The pH of HA activation of highly pathogenic avian influenza viruses was greater than human and low-pathogenicity avian influenza viruses, as reported by others. However, pLAIV viruses had a consistently higher pH of HA activation and reduced HA thermostability compared to the corresponding wild-type parental viruses. From studies with single-gene reassortant viruses bearing one gene segment from the AA/60 ca virus in recombinant H5N1 or pH1N1 viruses, we found that the lower HA thermal stability and increased pH of HA activation were associated with the AA/60 M gene. Together, the impaired HA acid and thermal stability and temperature sensitivity likely contributed to the restricted replication of the pLAIV viruses we observed in seronegative adults. There is increasing evidence that the HA stability of influenza viruses depends on the virus strain and host species and that HA stability can influence replication, virulence, and transmission of influenza A viruses in different species. We investigated the HA stability of pandemic live attenuated influenza vaccine (pLAIV) viruses and observed that the pLAIV viruses consistently had a less stable HA than the corresponding wild-type influenza viruses. The reduced HA stability and temperature sensitivity of the pLAIV viruses may account for their restricted replication in clinical trials. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

The Matrix Gene Segment Destabilizes the Acid and Thermal Stability of the Hemagglutinin of Pandemic Live Attenuated Influenza Virus Vaccines

PubMed Central

O'Donnell, Christopher D.; Vogel, Leatrice; Matsuoka, Yumiko; Jin, Hong

2014-01-01

ABSTRACT The threat of future influenza pandemics and their potential for rapid spread, morbidity, and mortality has led to the development of pandemic vaccines. We generated seven reassortant pandemic live attenuated influenza vaccines (pLAIVs) with the hemagglutinin (HA) and neuraminidase (NA) genes derived from animal influenza viruses on the backbone of the six internal protein gene segments of the temperature sensitive, cold-adapted (ca) A/Ann Arbor/60 (H2N2) virus (AA/60 ca) of the licensed seasonal LAIV. The pLAIV viruses were moderately to highly restricted in replication in seronegative adults; we sought to determine the biological basis for this restriction. Avian influenza viruses generally replicate at higher temperatures than human influenza viruses and, although they shared the same backbone, the pLAIV viruses had a lower shutoff temperature than seasonal LAIV viruses, suggesting that the HA and NA influence the degree of temperature sensitivity. The pH of HA activation of highly pathogenic avian influenza viruses was greater than human and low-pathogenicity avian influenza viruses, as reported by others. However, pLAIV viruses had a consistently higher pH of HA activation and reduced HA thermostability compared to the corresponding wild-type parental viruses. From studies with single-gene reassortant viruses bearing one gene segment from the AA/60 ca virus in recombinant H5N1 or pH1N1 viruses, we found that the lower HA thermal stability and increased pH of HA activation were associated with the AA/60 M gene. Together, the impaired HA acid and thermal stability and temperature sensitivity likely contributed to the restricted replication of the pLAIV viruses we observed in seronegative adults. IMPORTANCE There is increasing evidence that the HA stability of influenza viruses depends on the virus strain and host species and that HA stability can influence replication, virulence, and transmission of influenza A viruses in different species. We investigated the HA stability of pandemic live attenuated influenza vaccine (pLAIV) viruses and observed that the pLAIV viruses consistently had a less stable HA than the corresponding wild-type influenza viruses. The reduced HA stability and temperature sensitivity of the pLAIV viruses may account for their restricted replication in clinical trials. PMID:25122789

Multifunctional Nanocomposites for Breast Cancer Imaging and Therapy

DTIC Science & Technology

2008-07-01

compounds, because of the low stability of the thiolate -capped PbS QDs at physiological pH values. The following approach, consisting of 3 phases, was...syntheses employed amphiphilic polymers to stabilize CdSe/ZnS QDs, or phospholipids micelles to stabilize Si QDs, or used ligand exchange followed...attached per surface. However, it is very difficult to estimate the exact amount within the large G6- polymer of MW= 69,351 without measuring the 800 or

One-step formation of multiple Pickering emulsions stabilized by self-assembled poly(dodecyl acrylate-co-acrylic acid) nanoparticles.

PubMed

Zhu, Ye; Sun, Jianhua; Yi, Chenglin; Wei, Wei; Liu, Xiaoya

2016-09-13

In this study, a one-step generation of stable multiple Pickering emulsions using pH-responsive polymeric nanoparticles as the only emulsifier was reported. The polymeric nanoparticles were self-assembled from an amphiphilic random copolymer poly(dodecyl acrylate-co-acrylic acid) (PDAA), and the effect of the copolymer content on the size and morphology of PDAA nanoparticles was determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The emulsification study of PDAA nanoparticles revealed that multiple Pickering emulsions could be generated through a one-step phase inversion process by using PDAA nanoparticles as the stabilizer. Moreover, the emulsification performance of PDAA nanoparticles at different pH values demonstrated that multiple emulsions with long-time stability could only be stabilized by PDAA nanoparticles at pH 5.5, indicating that the surface wettability of PDAA nanoparticles plays a crucial role in determining the type and stability of the prepared Pickering emulsions. Additionally, the polarity of oil does not affect the emulsification performance of PDAA nanoparticles, and a wide range of oils could be used as the oil phase to prepare multiple emulsions. These results demonstrated that multiple Pickering emulsions could be generated via the one-step emulsification process using self-assembled polymeric nanoparticles as the stabilizer, and the prepared multiple emulsions have promising potential to be applied in the cosmetic, medical, and food industries.

Stability of Fentanyl Citrate in Polyolefin Bags.

PubMed

Donnelly, Ronald F

2016-01-01

Fentanyl is used to manage pain because it is a potent lipophilic opiate agonist. The stability of fentanyl in polyolefin bags when diluted to either 10 µg/mL or 50 µg/mL with sodium chloride 0.9% has not been studied. The chemical stability of fentanyl 50 µg/mL packaged in polyvinyl chloride bags has been studied, however, the stability in polyolefin bags is lacking. Polyolefin bags were aseptically filled with either 10-µg/mL or 50-µg/mL fentanyl solution. Containers were then stored at either 5°C and protected from light or 22°C and exposed to light for 93 days. Fentanyl peaks were monitored using a stability-indicatin high-performance liquid chromatographic method. Changes to color, clarity, and pH were also monitored. There were no signs of chemical degradation of fentanyl packaged in polyolefin bags at either 5°C or 22°C after storage for 93 days. Over the course of the study, all solutions remained colorless and clear. The pH showed a slight decrease during the 93 days of storage. The stability of both undiluted (50-µg/mL) and diluted (10-µg/mL) fentanyl solutions when packaged in polyolefin bags was 93 days when stored at either 5°C or 22°C. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Stability of thermostable alkaline protease from Bacillus licheniformis RP1 in commercial solid laundry detergent formulations.

PubMed

Sellami-Kamoun, Alya; Haddar, Anissa; Ali, Nedra El-Hadj; Ghorbel-Frikha, Basma; Kanoun, Safia; Nasri, Moncef

2008-01-01

The stability of crude extracellular protease produced by Bacillus licheniformis RP1, isolated from polluted water, in various solid laundry detergents was investigated. The enzyme had an optimum pH and temperature at pH 10.0-11.0 and 65-70 degrees C. Enzyme activity was inhibited by PMSF, suggesting that the preparation contains a serine-protease. The alkaline protease showed extreme stability towards non-ionic (5% Tween 20% and 5% Triton X-100) and anionic (0.5% SDS) surfactants, which retained 100% and above 73%, respectively, of its initial activity after preincubation 60 min at 40 degrees C. The RP1 protease showed excellent stability and compatibility with a wide range of commercial solid detergents at temperatures from 40 to 50 degrees C, suggesting its further application in detergent industry. The enzyme retained 95% of its initial activity with Ariel followed by Axion (94%) then Dixan (93.5%) after preincubation 60 min at 40 degrees C in the presence of 7 mg/ml of detergents. In the presence of Nadhif and New Det, the enzyme retained about 83.5% of the original activity. The effects of additives such as maltodextrin, sucrose and PEG 4000 on the stability of the enzyme during spray-drying and during subsequent storage in New Det detergent were also examined. All additives tested enhanced stability of the enzyme.

[Stabilization and long-term effect of chromium contaminated soil].

PubMed

Wang, Jing; Luo, Qi-Shi; Zhang, Chang-Bo; Tan, Liang; Li, Xu

2013-10-01

Short-term (3 d and 28 d) and long-term (1 a) stabilization effects of Cr contaminated soil were investigated through nature curing, using four amendments including ferrous sulfide, ferrous sulfate, zero-valent iron and sodium dithionite. The results indicated that ferrous sulfide and zero-valent iron were not helpful for the stabilization of Cr(VI) when directly used because of their poor solubility and immobility. Ferrous sulfate could effectively and rapidly decrease total leaching Cr and Cr(VI) content. The stabilization effect was further promoted by the generation of iron hydroxides after long-term curing. Sodium dithionite also had positive effect on soil stabilization. Appropriate addition ratio of the two chemicals could help maintain the soil pH in range of 6-8.

Formulation design space for stable, pH sensitive crystalline nifedipine nanoparticles.

PubMed

Jog, Rajan; Unachukwu, Kenechi; Burgess, Diane J

2016-11-30

Enteric coated formulations protect drugs from degrading in the harsh environment of the stomach (acidic pH and enzymes), and promotes drug delivery to and absorption into the duodenum and/or later parts of the intestine. Four DoE models were applied to optimize formulation parameters for the preparation of pH sensitive nifedipine nanoparticles. Stability studies were performed on the optimized formulations to monitor any possible variation in particle size distribution, homogeneity index, surface charge and drug release (pH 1.2 and pH 6.8). Stability studies were performed for 3 months at 4°C, 25°C and 40°C. A combination of Eudragit ® L 100-55 and polyvinyl alcohol was determined to be the most effective in stabilizing the nanoparticle suspension. The average particle size distribution, polydispersity index and surface charge of the optimized pH sensitive nifedipine nanoparticles were determined to be 131.86±8.21nm, 0.135±0.008 and -7.631±0.146mV, respectively. Following three months storage, it was observed that the formulations stored at 4°C were stable in terms of particle size distribution, polydispersity index, surface charge, drug loading and drug release, whereas those stored at 25°C and 40°C were relatively unstable. A predictive model to prepare stable pH sensitive nifedipine nanoparticles, was successfully developed using multiple linear regression analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Distribution of chloride, pH, resistivity, and sulfate levels in backfill for mechanically-stabilized earth walls and implications for corrosion testing : [summary].

DOT National Transportation Integrated Search

2015-04-01

Road construction projects often require mechanically stabilized earth (MSE), earthwork : construction in which soil is retained by walls and reinforced with wire mesh, metal strips, : and structural geosynthetics (geotextile or geogrid). The fill so...

pH-Dependent Binding of Chloride to a Marine Alkaline Phosphatase Affects the Catalysis, Active Site Stability, and Dimer Equilibrium.

PubMed

Hjörleifsson, Jens G; Ásgeirsson, Bjarni

2017-09-26

The effect of ionic strength on enzyme activity and stability varies considerably between enzymes. Ionic strength is known to affect the catalytic activity of some alkaline phosphatases (APs), such as Escherichia coli AP, but how ions affect APs is debated. Here, we studied the effect of various ions on a cold-adapted AP from Vibrio splendidus (VAP). Previously, we have found that the active form of VAP is extremely unstable at low ionic strengths. Here we show that NaCl increased the activity and stability of VAP and that the effect was pH-dependent in the range of pH 7-10. The activity profile as a function of pH formed two maxima, indicating a possible conformational change. Bringing the pH from the neutral to the alkaline range was accompanied by a large increase in both the K i for inorganic phosphate (product inhibition) and the K M for p-nitrophenyl phosphate. The activity transitions observed as the pH was varied correlated with structural changes as monitored by tryptophan fluorescence. Thermal and urea-induced inactivation was shown to be accompanied by neither dissociation of the active site metal ions nor dimer dissociation. This would suggest that the inactivation involved subtle changes in active site conformation. Furthermore, the VAP dimer equilibrium was studied for the first time and shown to highly favor dimerization, which was dependent on pH and NaCl concentration. Taken together, the data support a model in which anions bind to some specific acceptor in the active site of VAP, resulting in great stabilization and catalytic rate enhancement, presumably through a different mechanism.

Glycolipid Biosurfactants Activate, Dimerize, and Stabilize Thermomyces lanuginosus Lipase in a pH-Dependent Fashion.

PubMed

Madsen, Jens Kvist; Kaspersen, Jørn Døvling; Andersen, Camilla Bertel; Nedergaard Pedersen, Jannik; Andersen, Kell Kleiner; Pedersen, Jan Skov; Otzen, Daniel E

2017-08-15

We present a study of the interactions between the lipase from Thermomyces lanuginosus (TlL) and the two microbially produced biosurfactants (BSs), rhamnolipid (RL) and sophorolipid (SL). Both RL and SL are glycolipids; however, RL is anionic, while SL is a mixture of anionic and non-ionic species. We investigate the interactions of RL and SL with TlL at pH 6 and 8 and observe different effects at the two pH values. At pH 8, neither RL nor SL had any major effect on TlL stability or activity. At pH 6, in contrast, both surfactants increase TlL's thermal stability and fluorescence and activity measurements indicate interfacial activation of TlL, resulting in 3- and 6-fold improved activity in SL and RL, respectively. Nevertheless, isothermal titration calorimetry reveals binding of only a few BS molecules per lipase. Size-exclusion chromatography and small-angle X-ray scattering suggest formation of TlL dimers with binding of small amounts of either RL or SL at the dimeric interface, forming an elongated complex. We conclude that RL and SL are compatible with TlL and constitute promising green alternatives to traditional surfactants.

Examination of the effect of ageing and temperature at rigor on colour stability of lamb meat.

PubMed

Hopkins, D L; Lamb, T A; Kerr, M J; van de Ven, R J; Ponnampalam, E N

2013-10-01

A study of factors (ageing period, rigor temperature and vitamin E level) impacting on the colour stability of lamb m. longissimus thoracis et lumborum (LL) during 3 days of simulated retail display was undertaken. The LL were taken from 84 lambs from 3 slaughters. Slices of LL were measured fresh (24h post-mortem) or after ageing for 5 days in vacuum packaging. The oxy/met ratio (630/580 nm), declined with display time, and increased with increasing temperature at pH6.0. Redness (a*) values also declined with display time and a reduction in redness values was observed as LL pH at 24h post-mortem and/or pH at 18°C increased. There was no effect of ageing period or vitamin E level on the oxy/met ratio or a* values when the vitamin E level averaged 3.76 mg/kg LL. These results suggest that maximising vitamin E levels in lambs and achieving a moderate rate of pH decline will optimise colour stability irrespective of ageing period. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Influence of pH on heat-induced aggregation and degradation of therapeutic monoclonal antibodies.

PubMed

Ishikawa, Tomoyoshi; Ito, Takahiko; Endo, Ryosuke; Nakagawa, Keiko; Sawa, Eiji; Wakamatsu, Kaori

2010-01-01

Monoclonal antibodies are widely used for the treatment of various diseases, and because therapeutic monoclonal antibodies are stored in an aqueous solution or in a lyophilized state, the preparation of a stabilizing formulation that prevents their deterioration (degradation and aggregation) is crucial. Given the structural similarities of the immunoglobulin G (IgG) framework regions and a diversity of only four subclasses, we aimed to find common conditions that stabilize many different antibodies. In this study, we analyzed the effect of pH (the most critical factor in establishing a stable formulation) on human monoclonal antibodies from subclasses IgG1, IgG2, and IgG4, all of which have been utilized in antibody therapeutics. We found that human IgGs are stable with minimal heat-induced degradation and aggregation at pH 5.0-5.5 irrespective of their subclass. We also found that IgG1 is more susceptible to fragmentation, whereas IgG4 is more susceptible to aggregation. This basic information emphasizing the influence of pH on IgG stability should facilitate the optimization of formulation conditions tailored to individual antibodies for specific uses.

Effect of additive on Zeta potential and particle size of nickel nanoparticles

NASA Astrophysics Data System (ADS)

Sharma, Vikash; Tarachand, Chotia, Chandrabhan; Okram, G. S.

2017-05-01

Nickel nanoparticles (NPs) were prepared by thermal decomposition method using Oleylamine (OLY) as a solvent and Trioctylphosphine (TOP) as a surfactant. We have investigated the effect of pH and addition of Ethylenediamine tetraacetic acid (EDTA) on the stability and particle size of Ni NPs using zeta potential and particle size analyser. Coating of the surfactants on the surface of Ni NPs was confirmed by Fourier transform infrared (FTIR) spectroscopy. Autotitration study of zeta potential of these NPs in ethanol by dynamic light scattering (DLS) at different pH values confirmed an isoelectric point (IEP) at pH = 3.64 in ethanol and pH = 3.04 after addition of EDTA in ethanol. It was observed that addition of EDTA in nanosuspension enhances stability of Ni-NPs significantly.

pH regulation of the kinetic stability of the lipase from Thermomyces lanuginosus.

PubMed

Wang, H; Andersen, K K; Sehgal, P; Hagedorn, J; Westh, P; Borch, K; Otzen, D E

2013-01-08

Thermomyces lanuginosus lipase (TlL) is a kinetically stable protein, resistant toward both denaturation and refolding in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant decyl maltoside (DecM). We investigate the pH dependence of this kinetic stability. At pH 8, TlL remains folded and enzymatically active at multimillimolar surfactant concentrations but fails to refold from the acid urea-denatured state at submillimolar concentrations of SDS and DecM, indicating a broad concentration range of kinetic trapping or hysteresis. At pH 8, very few SDS molecules bind to TlL. The hysteresis SDS concentration range shrinks when moving to pH 4-6; in this pH range, SDS binds as micellelike clusters. Although hysteresis can be eliminated by reducing disulfide bonds, destabilizing the native state, and lowering the unfolding activation barrier, SDS sensitivity is not directly linked to intrinsic kinetic stability [its resistance to the general chemical denaturant guanidinium chloride (GdmCl)], because TlL unfolds more slowly in GdmCl at pH 6.0 than at pH 8.0. However, the estimated net charge drops from approximately -12 to approximately -5 between pH 8 and 6. SDS denatures TlL at pH 6.0 by nucleating via a critical number of bound SDS molecules on the surface of native TlL to form clusters. These results imply that SDS sensitivity is connected to the availability of appropriately charged regions on the protein. We suggest that conformational rigidity is a necessary but not sufficient feature of SDS resistance, because this has to be combined with sufficient negative electrostatic potential to avoid extensive SDS binding.

The dimensional stability analysis of seventeen stepped specimens of 18Ni 200 grade, PH13-8Mo and A-286

NASA Technical Reports Server (NTRS)

Wigley, D. A.

1983-01-01

This report documents the results of a dimensional stability analysis of seventeen stepped specimens that were used in the evaluation of factors influencing warpage in metallic alloys being used for cryogenic wind tunnel models. Specimens used in the analysis were manufactured from 18Ni 200 Grade Maaraging steel, PH13-8Mo, and A-286 stainless steel. Quantitative data are provided on the behavior of the specimens due to the effects of both machining and cryogenic cycling effects.

New coordination compounds of Cr(III) used in leather tanning

NASA Astrophysics Data System (ADS)

Crudu, Marian; Sibiescu, Doina; Rosca, Ioan; Sutiman, Daniel; Vizitiu, Mihaela; Apostolescu, Gabriela

2009-01-01

Some new coordination compounds of Cr(III) using as ligand N-hydroxy - succinimide, were obtained and studied. The combination ratio, central atom: ligand were 1:1; 1:2 and 1:3. The new complex compounds were studied using UV-Vis spectroscopy, conductance and pH measurements. The studies of obtaining and of stability of the new compounds were accomplished in aqueous solutions using methods characteristic for coordination compounds: conductance and pH measurements. The combination ratios and the stability constants were determined with methods characteristic for studies in solutions.

Cooperative alpha-helix formation of beta-lactoglobulin induced by sodium n-alkyl sulfates.

PubMed

Chamani, J; Moosavi-Movahedi, A A; Rajabi, O; Gharanfoli, M; Momen-Heravi, M; Hakimelahi, G H; Neamati-Baghsiah, A; Varasteh, A R

2006-01-01

It is generally assumed that folding intermediates contain partially formed native-like secondary structures. However, if we consider the fact that the conformational stability of the intermediate state is simpler than that of the native state, it would be expected that the secondary structures in a folding intermediate would not necessarily be similar to those of the native state. beta-Lactoglobulin is a predominantly beta-sheet protein, although it has a markedly high intrinsic preference for alpha-helical structure. The formation of non-native alpha-helical intermediate of beta-lactoglobulin was induced by n-alkyl sulfates including sodium octyl sulfate, SOS; sodium decyl sulfate, SDeS; sodium dodecyl sulfate, SDS; and sodium tetradecyl sulfate, STS at special condition. The effect of n-alkyl sulfates on the structure of native beta-lactoglobulin at pH 2 was utilized to investigate the contribution of hydrophobic interactions to the stability of non-native alpha-helical intermediate. The addition of various concentrations of n-alkyl sulfates to the native state of beta-lactoglobulin (pH 2) appears to support the stabilized form of non-native alpha-helical intermediate at pH 2. The m values of the intermediate state of beta-lactoglobulin by SOS, SDeS, SDS and STS showed substantial variation. The enhancement of m values as the stability criterion of non-native alpha-helical intermediate state corresponded with increasing chain length of the cited n-alkyl sulfates. The present results suggest that the folding reaction of beta-lactoglobulin follows a non-hierarchical mechanism and hydrophobic interactions play important roles in stabilizing the non-native alpha-helical intermediate state.

Study of chemical stability of lemon oil components in sodium caseinate-lactose glycoconjugate-stabilized oil-in-water emulsions using solid-phase microextraction-gas chromatography.

PubMed

Sabik, Hassan; Achouri, Allaoua; Alfaro, Maria; Pelletier, Marylène; Belanger, Denis; Britten, Michel; Fustier, Patrick

2014-07-25

A headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC/MS) method was developed to quantify lemon oil components and their degradation products in oil-in-water (O/W) emulsions prepared with sodium caseinate-heated-lactose (NaC-T + Lact) glycoconjugates as wall materials at two pH values (3.0 and 6.8). NaC-T + Lact conjugates had a significantly lower solubility at both pHs. Hydrolysis prior to glycation enhanced the solubility of glycoconjugates. Glycation with lactose did not improve the emulsion activity of NaC, while caseinate glycoconjugates showed much stronger antioxidant activity than the NaC-control sample. This might be due to the presence of melanoidins formed between the sugar and amino acid compounds as supported by the increase in browning intensity. Among the SPME-fibres tested, carboxen/polydimethylsiloxane (CAR/PDMS) provided better results in terms of sensitivity and selectivity for oil lemon components and their degradation products. Storage studies of these emulsions demonstrated that glycated NaC-T + Lact showed protection against peroxidation compared to the control. However, acidic pH conditions altered their stability over storage time. The major off-flavor components (α-terpineol and carvone) were inhibited in emulsions stabilized with glycated NaC, particularly at pH 6.8. The use of NaC-T + Lact conjugates showed improved encapsulation efficiency and stability and could be used as potential food ingredient-emulsifiers for stabilising citrus oils against oxidative degradation in food and beverage applications.

pH-induced inversion of water-in-oil emulsions to oil-in-water high internal phase emulsions (HIPEs) using core cross-linked star (CCS) polymer as interfacial stabilizer.

PubMed

Chen, Qijing; Deng, Xiaoyong; An, Zesheng

2014-06-01

A pH-responsive core cross-linked star (CCS) polymer containing poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) arms was used as an interfacial stabilizer for emulsions containing toluene (80 v%) and water (20 v%). In the pH range of 12.1-9.3, ordinary water-in-oil emulsions were formed. Intermediate multiple emulsions of oil-in-water-in-oil and water-in-oil-in-water were formed at pH 8.6 and 7.5, respectively. Further lowering the pH resulted in the formation of gelled high internal phase emulsions of oil-in-water type in the pH range of 6.4-0.6. The emulsion behavior was correlated with interfacial tension, conductivity and configuration of the CCS polymer at different pH. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production of imidazole alkaloids in cell cultures of jaborandi as affected by the medium pH.

PubMed

Andreazza, N L; Abreu, I N; Sawaya, A C H F; Eberlin, M N; Mazzafera, P

2009-04-01

The effect of pH (from 4.8 to 9.8) on the production of pilosine and pilocarpine and on their partition between cell and medium was studied in two lineages (P and PP) of Pilocarpus microphyllus cell suspension cultures. Highest mass accumulation was observed at high pHs and both lineages produced pilocarpine while only lineage PP produced pilosine. Both alkaloids were released in the medium but higher accumulation occurred in the cells. The highest production of pilocarpine was at pH 8.8-9.8 in both cell lineages. Other imidazole alkaloids were also identified in both lineages. At all pHs tested, the pH in the media cultures tended to stabilize around 6 after 10-15 days of cultivation. NO3(-) and NH4+ variation in the media might partially explain the pH stabilization.

An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

NASA Technical Reports Server (NTRS)

Bugbee, B. G.; Salisbury, F. B.

1985-01-01

All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

One-Phase Synthesis of Water-Soluble Gold Nanoparticles with Control over Size and Surface Functionalities

DTIC Science & Technology

2010-01-01

groups for further coupling to target molecules. Since the classic citrate reduction of aurate to prepare citrate - stabilized AuNPs was pioneered by the...reduced stability against excess salts and changes in solution pH (e.g., citrate -stabilized NPs); (2) the inability to prepare nanocrystals over a wide...size regime ( citrate reduction usually producesAuNPs smaller than 10 nm, but larger sizes require additional refluxing in the presence of sodium citrate

Stabilization of gold nanoparticles by 6-mercaptopurine monolayers. Effects of the solvent properties.

PubMed

Viudez, Alfonso J; Madueño, Rafael; Pineda, Teresa; Blázquez, Manuel

2006-09-14

6-Mercaptopurine-coated gold nanoparticles (6MP-AuNPs) have been prepared by modification of the nanoparticle surface with 6MP upon displacement of the protective layer of citrate anions. The modification has been studied by UV-vis and FTIR spectroscopies. A study of the stability of these 6MP-AuNPs in aqueous solutions as a function of ionic strength and pH has shown the importance of the charges on the stabilization. The protonation of N9 of the 6MP molecules brings about a sudden flocculation phenomenon. However, the flocculation is reversible upon changing the pH to values where the molecules become newly charged. Evidence of the competence between the interaction of capping solvent molecules and the attractive forces between particles is also shown in this paper.

Influence of droplet charge on the chemical stability of citral in oil-in-water emulsions.

PubMed

Choi, Seung Jun; Decker, Eric Andrew; Henson, Lulu; Popplewell, L Michael; McClements, David Julian

2010-08-01

The chemical stability of citral, a flavor component widely used in beverage, food, and fragrance products, in oil-in-water emulsions stabilized by surfactants with different charge characteristics was investigated. Emulsions were prepared using cationic (lauryl alginate, LAE), non-ionic (polyoxyethylene (23) lauryl ether, Brij 35), and anionic (sodium dodecyl sulfate, SDS) surfactants at pH 3.5. The citral concentration decreased over time in all the emulsions, but the rate of decrease depended on surfactant type. After 7 d storage, the citral concentrations remaining in the emulsions were around 60% for LAE- or Brij 35-stabilized emulsions and 10% for SDS-stabilized emulsions. An increase in the local proton (H(+)) concentration around negatively charged droplet surfaces may account for the more rapid citral degradation observed in SDS-stabilized emulsions. A strong metal ion chelator (EDTA), which has previously been shown to be effective at increasing the oxidative stability of labile components, had no effect on citral stability in LAE- or Brij 35-stabilized emulsions, but it slightly decreased the initial rate of citral degradation in SDS-stabilized emulsions. These results suggest the surfactant type used to prepare emulsions should be controlled to improve the chemical stability of citral in emulsion systems.

Accelerating Vaccine Formulation Development Using Design of Experiment Stability Studies.

PubMed

Ahl, Patrick L; Mensch, Christopher; Hu, Binghua; Pixley, Heidi; Zhang, Lan; Dieter, Lance; Russell, Ryann; Smith, William J; Przysiecki, Craig; Kosinski, Mike; Blue, Jeffrey T

2016-10-01

Vaccine drug product thermal stability often depends on formulation input factors and how they interact. Scientific understanding and professional experience typically allows vaccine formulators to accurately predict the thermal stability output based on formulation input factors such as pH, ionic strength, and excipients. Thermal stability predictions, however, are not enough for regulators. Stability claims must be supported by experimental data. The Quality by Design approach of Design of Experiment (DoE) is well suited to describe formulation outputs such as thermal stability in terms of formulation input factors. A DoE approach particularly at elevated temperatures that induce accelerated degradation can provide empirical understanding of how vaccine formulation input factors and interactions affect vaccine stability output performance. This is possible even when clear scientific understanding of particular formulation stability mechanisms are lacking. A DoE approach was used in an accelerated 37(°)C stability study of an aluminum adjuvant Neisseria meningitidis serogroup B vaccine. Formulation stability differences were identified after only 15 days into the study. We believe this study demonstrates the power of combining DoE methodology with accelerated stress stability studies to accelerate and improve vaccine formulation development programs particularly during the preformulation stage. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Fabrication, characterization and antimicrobial activities of thymol-loaded zein nanoparticles stabilized by sodium caseinate-chitosan hydrochloride double layers.

PubMed

Zhang, Yaqiong; Niu, Yuge; Luo, Yangchao; Ge, Mei; Yang, Tian; Yu, Liangli Lucy; Wang, Qin

2014-01-01

Thymol-loaded zein nanoparticles stabilized with sodium caseinate (SC) and chitosan hydrochloride (CHC) were prepared and characterized. The SC stabilized nanoparticles had well-defined size range and negatively charged surface. Due to the presence of SC, the stabilized zein nanoparticles showed a shift of isoelectric point from 6.18 to 5.05, and had a desirable redispersibility in water at neutral pH after lyophilization. Coating with CHC onto the SC stabilized zein nanoparticles resulted in increased particle size, reversal of zeta potential value from negative to positive, and improved encapsulation efficiency. Both thymol-loaded zein nanoparticles and SC stabilized zein nanoparticles had a spherical shape and smooth surface, while the surfaces of CHC-SC stabilized zein nanoparticles seemed rough and had some clumps. Encapsulated thymol was more effective in suppressing gram-positive bacterium than un-encapsulated thymol for a longer time period. Copyright © 2013 Elsevier Ltd. All rights reserved.

Colloidal stability of CeO2 nanoparticles coated with either natural organic matter or organic polymers under various hydrochemical conditions

NASA Astrophysics Data System (ADS)

Dippon, Urs; Pabst, Silke; Klitzke, Sondra

2016-04-01

The worldwide marked for engineered nanoparticles (ENPs) is growing and concerns on the environmental fate- and toxicity of ENPs are rising. Understanding the transport of ENPs within and between environmental compartments such as surface water and groundwater is crucial for exposition modeling, risk assessment and ultimately the protection of drinking water resources. The transport of ENPs is strongly influenced by the surface properties and aggregation behavior of the particles, which is strongly controlled by synthetic and natural organic coatings. Both, surface properties and aggregation characteristics are also key properties for the industrial application of ENPs, which leads to the development and commercialization of an increasing number of surface-functionalized ENPs. These include metals and oxides such as Cerium dioxide (CeO2) with various organic coatings. Therefore, we investigate CeO2 ENPs with different surface coatings such as weakly anionic polyvinyl alcohol (PVA) or strongly anionic poly acrylic acid (PAA) with respect to their colloidal stability in aqueous matrix under various hydrochemical conditions (pH, ionic strength) and their transport behavior in sand filter columns. Furthermore, we investigate the interaction of naturally occurring organic matter (NOM) with CeO2 ENPs and its effect on surface charge (zeta potential), colloidal stability and transport. While uncoated CeO2 ENPs aggregate at pH > 4 in aqueous matrix, our results show that PAA and PVA surface coatings as well as NOM sorbed to CeO2-NP surfaces can stabilize CeO2 ENPs under neutral and alkaline pH conditions in 1 mM KCl solution. Under slightly acidic conditions, differences between the three particle types were observed. PVA can stabilize particle suspensions in presence of 1 mM KCl at pH > 4.3, PAA at pH >4.0 and NOM at >3.2. While the presence of KCl did not influence particle size of NOM-CeO2 ENPs, CaCl2 at >2 mM lead to aggregation. Further results on the influence of KCl and CaCl2 on aggregation of coated CeO2 ENPs and transport in sand filter columns will be presented.

A Pilot Chemical and Physical Stability Study of Extemporaneously Compounded Levetiracetam Intravenous Solution.

PubMed

Raphael, Chenzira D; Zhao, Fang; Hughes, Susan E; Juba, Katherine M

2015-01-01

Levetiracetam is a commonly used antiepileptic medication for tumor-related epilepsy. However, the 100 mL intravenous (IV) infusion volume can be burdensome to imminently dying hospice patients. A reduced infusion volume would improve patient tolerability. The purpose of this study was to evaluate the stability of 1000 mg/25 mL (40 mg/mL) levetiracetam IV solution in sodium chloride 0.9%. We prepared levetiracetam 40 mg/mL IV solution and added it to polyvinyl chloride (PVC) bags, polyolefin bags, and polypropylene syringes. Triplicate samples of each product were stored at refrigeration (2-8°C) and analyzed on days 0, 1, 4, 7, and 14. Samples were subjected to visual inspection, pH measurement, and stability-indicating high-performance liquid chromatography (HPLC) analysis. Over the 2-week storage period, there was no significant change in visual appearance or pH for any of the stability samples. The HPLC results confirmed that all stability samples retained 94.2-101.3% of initial drug concentration and no degradation products or leachable material from the packaging materials were observed. We conclude that levetiracetam 1000 mg/25 mL IV solution in sodium chloride 0.9% is physically and chemically stable for up to 14 days under refrigeration in polypropylene syringes, PVC bags, and polyolefin bags.

Linear Dimensional Stability of Irreversible Hydrocolloid Materials Over Time.

PubMed

Garrofé, Analía B; Ferrari, Beatriz A; Picca, Mariana; Kaplan, Andrea E

2015-12-01

The aim of this study was to evaluate the linear dimensional stability of different irreversible hydrocolloid materials over time. A metal mold was designed with custom trays made of thermoplastic sheets (Sabilex, sheets 0.125 mm thick). Perforations were made in order to improve retention of the material. Five impressions were taken with each of the following: Kromopan 100 (LASCOD) [AlKr], which has dimensional stability of 100 hours, and Phase Plus (ZHERMACK) [AlPh], which has dimensional stability of 48 hours. Standardized digital photographs were taken at different time intervals (0, 15, 30, 45, 60, 120 minutes; 12, 24 and 96 hours), using an "ad-hoc" device. The images were analyzed with software (UTHSCSA Image Tool) by measuring the distance between intersection of the lines previously made at the top of the mold. The results were analyzed by ANOVA for repeated measures. Initial and final values were (mean and standard deviation): AlKr: 16.44 (0.22) and 16.34 (0.11), AlPh: 16.40 (0.06) and 16.18 (0.06). Statistical evaluation showed significant effect of material and time factors. Under the conditions in this study, time significantly affects the linear dimensional stability of irreversible hydrocolloid materials. Sociedad Argentina de Investigación Odontológica.

CASE STUDY: IN-SITU SOLIDIFICATION/STABILIZATION OF HAZARDOUS ACID WASTE OIL SLUDGE AND LESSONS LEARNED

EPA Science Inventory

The South 8th Street site contained a 2.5 acre oily sludge pit with very low pH waste produced by oil recycling activities. This sludge was treated using in-situ solidification/stabilization technology applied by deep soil mixing augers. The problems encountered, solutions develo...

LABORATORY STUDIES ON THE STABILITY AND TRANSPORT OF INORGANIC COLLOIDS THROUGH NATURAL AQUIFER MATERIAL

EPA Science Inventory

The stability and transport of radio-labeled Fe2O3 particles were studied using laboratory batch and column techniques. Core material collected from shallow sand and gravel aquifer was used as the immobile column matrix material. Variables in the study included flow rate, pH, i...

Green synthesis of Au nanoparticles using potato extract: stability and growth mechanism

NASA Astrophysics Data System (ADS)

Castillo-López, D. N.; Pal, U.

2014-08-01

We report on the synthesis of spherical, well-dispersed colloidal gold nanoparticles of 17.5-23.5 nm average sizes in water using potato extract (PE) both as reducing and stabilizing agent. The effects of PE content and the pH value of the reaction mixture have been studied. Formation and growth dynamics of the Au nanoparticles in the colloids were studied using transmission electron microscopy and UV-Vis optical absorption spectroscopy techniques. While the reductor content and, hence, the nucleation and growth rates of the nanoparticles could be controlled by controlling the PE content in the reaction solution, the stability of the nanoparticles depended strongly on the pH of the reaction mixture. The mechanisms of Au ion reduction and stabilization of Au nanoparticles by potato starch have been discussed. The use of common natural solvent like water and biological reductor like PE in our synthesis process opens up the possibility of synthesizing Au nanoparticles in fully green (environmental friendly) way, and the Au nanoparticles produced in such way should have good biocompatibility.

Vermicomposting of food waste: assessing the stability and maturity

PubMed Central

2012-01-01

The vermicompost using earthworms (Eisenia Fetida) was produced from food waste and chemical parameters (EC, pH, carbon to nitrogen contents (C/N)) and germination bioassay was examined in order to assess the stability and maturity indicators during the vermicomposting process. The seed used in the germination bioassay was cress. The ranges of EC, pH, C/N and germination index were 7.5-4.9 mS/cm, 5.6-7.53, 30.13-14.32% and 12.8-58.4%, respectively. The germination index (GI) value revealed that vermicompost rendered as moderate phytotoxic to cress seed. Pearson correlation coefficient was used to evaluate the relationship between the parameters. High statistically significant correlation coefficient was calculated between the GI value and EC in the vermicompost at the 99% confidence level. The C/N value showed that the vermicompost was stable. As a result of these observations, stability test alone, was not able to ensure high vermicompost quality. Therefore, it appears that determining vermicompost quality requires a simultaneous use of maturity and stability tests. PMID:23369642

Stability of Metronidazole Suspensions.

PubMed

Donnelly, Ronald F; Ying, James

2015-01-01

Metronidazole is an antiprotozoal agent used in the treatment of bacterial and protozoal anaerobic infections. The objectives of this study were to develop concentrated metronidazole suspensions that are inexpensive and easy to prepare and determine the stability of these suspensions after storage in amber polyvinyl chloride bottles at room temperature (23°C) and under refrigeration (5°C). Metronidazole suspensions (50 mg/mL) were prepared from powder using Ora-Blend or simple syrup as the vehicles. Samples were collected in triplicate from each container on days 0, 7, 14, 28, 56, and 93. Samples were assayed using a high-performance liquid chromatography method that had been validated as stability indicating. Color, change in physical appearance, and pH were also monitored at each time interval. There was no apparent change in color or physical appearance. The pH values changed by less than 0.20 units over the 93 days. The stability of metronidazole suspensions compounded from United States Pharmacopeia powder using Ora-Blend or simple syrup and packaged in amber polyvinyl chloride bottles was determined to be 93 days when stored at either room temperature or under refrigeration.

Using amorphous manganese oxide for remediation of smelter-polluted soils: a pH-dependent long-term stability study

NASA Astrophysics Data System (ADS)

Ettler, Vojtech; Tomasova, Zdenka; Komarek, Michael; Mihaljevic, Martin; Sebek, Ondrej

2015-04-01

In soil systems, manganese (Mn) oxides are commonly found to be powerful sorbents of metals and metalloids and are thus potentially useful in soil remediation. A novel amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH = 3 - 8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH > 5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that "labile" fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils and other in situ applications need to be evaluated. This study was supported by the Czech Science Foundation (GAČR 15-07117S).

Doxorubicin-conjugated mesoporous magnetic colloidal nanocrystal clusters stabilized by polysaccharide as a smart anticancer drug vehicle.

PubMed

Li, Dian; Tang, Jing; Wei, Chuan; Guo, Jia; Wang, Shilong; Chaudhary, Deeptangshu; Wang, Changchun

2012-09-10

Fabrication of magnetic nanocarriers that demonstrate enhanced biocompatibility and excellent colloidal stability is critical for the application of magnetic-motored drug delivery, and it remains a challenge. Herein, a novel approach to synthesize mesoporous magnetic colloidal nanocrystal clusters (MMCNCs) that are stabilized by agarose is described; these clusters demonstrate high magnetization, large surface area and pore volume, excellent colloidal stability, enhanced biocompatibility, and acid degradability. The hydroxyl groups of agarose, which cover the surface of the magnetic nanocrystals, are modified with vinyl groups, followed by click reaction with mercaptoacetyl hydrazine to form the terminal hydrazide (-CONHNH(2)). The anticancer agent doxorubicin (DOX) is then conjugated to MMCNCs through a hydrazone bond. The resulting hydrazone is acid cleavable, thereby providing a pH-sensitive drug release capability. This novel carrier provides an important step towards the construction of a new family of magnetic-motored drug-delivery systems. The experimental results show that the release rate of DOX from the DOX-conjugated MMCNCs (MMCNCs-DOX) is dramatically improved at low pH (tumor cell: pH 4-5 in the late stage of endolysosome and pH 5-6 from the early to late endosome), while almost no DOX is released at neutral pH (blood plasma). The cell cytotoxicity of the MMCNCs-DOX measured by MTT assay exhibits a comparable antitumor efficacy but lower cytotoxicity for normal cell lines, when measured against the free drug, thus achieving the aim of reducing side effects to normal tissues associated with controlled drug release. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional properties of protein isolates extracted from stabilized rice bran by microwave, dry heat, and parboiling.

PubMed

Khan, Saima Hafeez; Butt, Masood Sadiq; Sharif, Mian Kamran; Sameen, Ayesha; Mumtaz, Semee; Sultan, Muhammad Tauseef

2011-03-23

Protein isolates extracted from differently stabilized rice bran were analyzed to work out the food use potential. Bulk density remained higher for isolates obtained from heat stabilized bran, the treatments were found to have positive impact on the oil absorption properties, while the water absorption was slightly impaired owing to some possible configurational changes. Surface hydrophobicity and emulsion properties were improved with bran stabilization. Isolates exhibited better foaming properties owing to the flexible nature of protein molecules, with less intensive disulfide bonding, that were slightly affected by the stabilization treatment. Nitrogen solubility index followed a curved pattern with the least value near isoelectric point that showed an increasing trend toward basic pH, and parboiled protein isolates exhibited better gelling properties among the isolates.

Grape seed and apple tannins: emulsifying and antioxidant properties.

PubMed

Figueroa-Espinoza, Maria Cruz; Zafimahova, Andrea; Alvarado, Pedro G Maldonado; Dubreucq, Eric; Poncet-Legrand, Céline

2015-07-01

Tannins are natural antioxidants found in plant-based foods and beverages, whose amphiphilic nature could be useful to both stabilize emulsions and protect unsaturated lipids from oxidation. In this paper, the use of tannins as antioxidant emulsifiers was studied. The main parameters influencing the stability of emulsions (i.e. tannins structure and concentration, aqueous phase pH, and ionic strength) were identified and optimized. Oil in water emulsions stabilized with tannins were compared with those stabilized with two commercial emulsifying agents, poly(vinyl alcohol) (PVA) and polyoxyethylene hydrogenated castor oil. In optimized conditions, the condensed tannins allowed to obtain a stability equivalent to that of PVA. Tannins presented good antioxidant activity in oil in water emulsion, as measured by the conjugated autoxidizable triene (CAT) assay. Copyright © 2015 Elsevier Ltd. All rights reserved.

X-Ray Crystallographic Studies of Electrostatic Effects in Cubic Insulin

NASA Astrophysics Data System (ADS)

Gursky, Olga

1992-09-01

Cubic crystals of bovine insulin were obtained at pH 9 from sodium phosphate buffer. Pathway dependence of crystallization was analysed and crystallization using controlled nucleation was developed. Crystal stability and solubility were surveyed by dialysing the crystals against salt solutions varying in salt composition and ionic strength. Crystals dialysed in 0.1-0.2M Li, Na, K, Rb, NH(4) or Tl salt solutions at pH 9 diffracted to beyond 2.8A, while crystals dialysed in Cs, Mg, Ca or La rapidly lost lattice order. Change in the solvent anion did not affect crystal stability. Electron density maps calculated from X-ray data to 2.8A resolution showed two specific cation binding sites which may be occupied by monovalent cations with ionic radii <1.5A. One site lies between insulin dimers near crystallographic two-fold axis without the close involvement of protein charged groups. Cation binding at this site is important for crystal stability. The other site is alternatively occupied by B10 His in one of its two conformations. At pH 7, the Tl occupancy at both sites was decreased, at pH 9.5 the Tl occupancy of the site near B10 His was increased. The structure was refined using the refined model of cubic porcine insulin and the X-ray data collected to 2A resolution from a bovine insulin crystal at pH 9, to R = 16.1% for the data extending from 10A to 2A. High -resolution data from crystals at pH 7 and pH 10 were collected and analysed. The weights of the two B10 His conformers and the cation occupancy near B10 vary in the pH range from 7 to 10, indicating histidine titration. Shifts in the positions of B1-B4 at pH 7 suggest titration of the B-chain terminal amino groups. Co-operative conformational changes in the surface charged residues A1, A4, B21, B29, B30 at pH 10.2 suggest titration of the A-chain terminal amino groups. In several crystals treated with dichloroethane, the syn-dichloroethane was bound in the niche across the two-fold axis connecting insulin monomers. Dichloroethane binding does not perturb the site geometry and probably leads to cubic insulin preparations of increased stability.

The pH Stability of Foot-and-Mouth Disease Virus Particles Is Modulated by Residues Located at the Pentameric Interface and in the N Terminus of VP1.

PubMed

Caridi, Flavia; Vázquez-Calvo, Angela; Sobrino, Francisco; Martín-Acebes, Miguel A

2015-05-01

The picornavirus foot-and-mouth disease virus (FMDV) is the etiological agent of a highly contagious disease that affects important livestock species. The FMDV capsid is highly acid labile, and viral particles lose infectivity due to their disassembly at pH values slightly below neutrality. This acid sensitivity is related to the mechanism of viral uncoating and genome penetration from endosomes. In this study, we have analyzed the molecular basis of FMDV acid-induced disassembly by isolating and characterizing a panel of novel FMDV mutants differing in acid sensitivity. Amino acid replacements altering virion stability were preferentially distributed in two different regions of the capsid: the N terminus of VP1 and the pentameric interface. Even more, the acid labile phenotype induced by a mutation located at the pentameric interface in VP3 could be compensated by introduction of an amino acid substitution in the N terminus of VP1. These results indicate that the acid sensitivity of FMDV can be considered a multifactorial trait and that virion stability is the fine-tuned product of the interaction between residues from different capsid proteins, in particular those located within the N terminus of VP1 or close to the pentameric interface. The viral capsid protects the viral genome from environmental factors and contributes to virus dissemination and infection. Thus, understanding of the molecular mechanisms that modulate capsid stability is of interest for the basic knowledge of the biology of viruses and as a tool to improve the stability of conventional vaccines based on inactivated virions or empty capsids. Using foot-and-mouth disease virus (FMDV), which displays a capsid with extreme acid sensitivity, we have performed a genetic study to identify the molecular determinants involved in capsid stability. A panel of FMDV mutants with differential sensitivity to acidic pH was generated and characterized, and the results showed that two different regions of FMDV capsid contribute to modulating viral particle stability. These results provide new insights into the molecular mechanisms of acid-mediated FMDV uncoating. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Investigation of complexes tannic acid and myricetin with Fe(III)

NASA Astrophysics Data System (ADS)

Sungur, Şana; Uzar, Atike

2008-01-01

The pH dependence of the complexes was determined by both potentiometric and spectrophotometric studies. Stability constants and stoichiometries of the formed complexes were determined using slope ratio method. Fe(III) was formed complexes with tannic acid of various stoichiometries, which in the 1:1 molar ratio at pH < 3, in the 2:1 molar ratio at pH 3-7 and in the 4:1 molar ratio at pH > 7. Fe(III) was formed complexes with myricetin in the 1:2 molar ratio at pH 4 and 5 and in the 1:1 molar ratio at pH 6. Stability constant values were found to be 10 5 to 10 17 and 10 5 to 10 9 for Fe(III)-tannic acid complexes and Fe(III)-myricetin complexes. Both tannic acid and myricetin were possessed minimum affinities to Cu(II) and Zn(II). They had less affinity for Al(III) than for Fe(III).

Environmental responsiveness of polygalacturonic acid-based multilayers to variation of pH.

PubMed

Westwood, Marta; Noel, Timothy R; Parker, Roger

2011-02-14

The effect of pH on the stability of layer-by-layer deposited polygalacturonic acid (PGalA)-based multilayer films prepared with the polycations poly-L-lysine, chitosan, and lysozyme is studied. The response was characterized using a quartz crystal microbalance, dual polarization interferometry, and Fourier transform infrared spectroscopy which probe multilayer thickness, density, polymer mass (composition and speciation), and hydration. All multilayers showed irreversible changes in response to pH change becoming thinner due to the partial disassembly. Preferential loss of the polycation (50-80% w/w) and relative small losses of PGaLA (10-35% w/w) occurred. The charge density on the polycation has a strong influence on the response to the acid cycle. Most of the disassembly takes place at the pH lower that pK(a) of PGaLA, indicating that this factor was crucial in determining the stability of the films. The pH challenge also revealed a polycation-dependent shift to acid pH in the PGaLA pK(a).

Acid decomposition and thiourea leaching of silver from hazardous jarosite residues: Effect of some cations on the stability of the thiourea system.

PubMed

Calla-Choque, D; Nava-Alonso, F; Fuentes-Aceituno, J C

2016-11-05

The recovery of silver from hazardous jarosite residues was studied employing thiourea as leaching agent at acid pH and 90°C. The stability of the thiourea in synthetic solutions was evaluated in the presence of some cations that can be present in this leaching system: cupric and ferric ions as oxidant species, and zinc, lead and iron as divalent ions. Two silver leaching methods were studied: the simultaneous jarosite decomposition-silver leaching, and the jarosite decomposition followed by the silver leaching. The study with synthetic solutions demonstrated that cupric and ferric ions have a negative effect on thiourea stability due to their oxidant properties. The effect of cupric ions is more significant than the effect of ferric ions; other studied cations (Fe(2+), Zn(2+), Pb(2+)) had no effect on the stability of thiourea. When the decomposition of jarosite and the silver leaching are carried out simultaneously, 70% of the silver can be recovered. When the acid decomposition was performed at pH 0.5 followed by the leaching step at pH 1, total silver recovery increased up to 90%. The zinc is completely dissolved with any of these processes while the lead is practically insoluble with these systems producing a lead-rich residue. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of different source additives and wilt conditions on the pH value, aerobic stability, and carbohydrate and protein fractions of alfalfa silage.

PubMed

Tao, Lian; Zhou, He; Zhang, Naifeng; Si, Bingwen; Tu, Yan; Ma, Tao; Diao, Qiyu

2017-01-01

To improve the silage quality and reduce the silage additive cost, the present experiment was designed to evaluate the potential of applying the fermented juice of epiphytic lactic acid bacteria (FJLB) as an additive in alfalfa silage. The effects of FJLB on the fermentation quality, carbohydrate and protein fractions, and aerobic stability of alfalfa silage wilted under five different conditions were investigated and compared with commercial lactic acid bacteria (CLAB) and the control. The FJLB application decreased the pH value, the volatile fatty acids and non-protein nitrogen content, and the loss of sugar by 9.9%, 22.9%, 19.6% and 9.6%, respectively; it increased the lactic acid concentration by 29.5% and the aerobic stability by 17 h in comparison to the control. The FJLB application also decreased the pH value (4.44 vs. 4.66) and volatile fatty acid content (38.32 vs. 44.82) and increased the lactic acid concentration (68.99 vs. 63.29) in comparison to the CLAB-treated silage. However, the FJLB treatment had lower aerobic stability (254 h vs. 274 h) than the CLAB treatment. The FJLB application improved silage quality in comparison to the control; in addition, its effect as a fermentation stimulant may be comparable to or even better than CLAB. © 2016 Japanese Society of Animal Science.

Colour evaluation of a phycobiliprotein-rich extract obtained from Nostoc PCC9205 in acidic solutions and yogurt.

PubMed

de O Moreira, Isabela; Passos, Thaís S; Chiapinni, Claudete; Silveira, Gabrielle K; Souza, Joana C M; Coca-Vellarde, Luis Guillermo; Deliza, Rosires; de Lima Araújo, Kátia G

2012-02-01

Phycobiliproteins are coloured proteins produced by cyanobacteria, which have several applications because of their colour properties. However, there is no available information about the colour stability of phycobiliproteins from Nostoc sp. in food systems. The aim of this work was to study the colour stability of a purple-coloured phycobiliprotein-rich extract from the cyanobacterium Nostoc PCC9205 in acidic solutions and yogurt. Variations of pH for Nostoc PCC9205 extract have shown stability for the L* (lightness) and a* (redness) indexes in the range 1.0-7.0. The b* index (blueness), however, increased at pH values below 4.0, indicating loss of the blue colour. The Nostoc PCC9205 extract was used as colorant in yogurt (pH 4.17) stored for 60 days. Instrumental colour analysis showed no changes for the L* and a* indexes during storage, whereas the b* index changed after 20 days of storage. A multiple comparison test showed colour instability after 20 days of storage. A hedonic scale test performed on the 60th day of storage showed acceptability of the product. The red component of the phycobiliprotein-rich extract from Nostoc PCC9205 presented an improved stability in acidic media and yogurt compared with the blue component of this extract. Copyright © 2011 Society of Chemical Industry.

Orange pectin mediated growth and stability of aqueous gold and silver nanocolloids

NASA Astrophysics Data System (ADS)

Nigoghossian, Karina; dos Santos, Molíria V.; Barud, Hernane S.; da Silva, Robson R.; Rocha, Lucas A.; Caiut, José M. A.; de Assunção, Rosana M. N.; Spanhel, Lubomir; Poulain, Marcel; Messaddeq, Younes; Ribeiro, Sidney J. L.

2015-06-01

The role of orange based pectin in the nucleation and growth of silver and gold nanoparticles is addressed. Pectin is a complex polysaccharide found in fruits such as oranges, lemons, passion fruits or apples. It displays smooth and hairy chain regions containing hydroxyl-, ester-, carboxylate- and eventually amine groups that can act as surface ligands interacting under various pH conditions more or less efficiently with growing nanometals. Here, a high methoxy pectin (>50% esterified) was used as a stabilizer/reducing agent in the preparation of gold, silver and silver-gold nanoparticles. Commercial pectin (CP) and pectin extracted from orange bagasse (OP) were used. Optionally, trisodium citrate or oxalic acid we used to reduce AgNO3 and HAuCl4 in aqueous environment. Characterization methods included UV-vis absorption spectroscopy, transmission electron microscopy, electron diffraction and energy-dispersive X-ray spectroscopy. The results show that under different pH conditions, pectin and reducing agents allow producing various nanostructures shapes (triangles, spheres, rods, octahedrons and decahedrons) often with high polydispersity and sizes ranging between 5 nm and 30 nm. In addition, depending on Ag/Au-ratio and pH, the surface plasmon bands can be continuously shifted between 410 nm and 600 nm. Finally, pectin seems to be a highly efficient stabilizer of the colloidal systems that show a remarkable stability and unchanged optical spectral response even after five years.

Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

PubMed

Zhang, Jiewen; Bell, Leonard N

2017-04-01

Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm 2 for dark conditions, 27 μW/cm 2 for low intensity, and 190 μW/cm 2 for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability. © 2017 Institute of Food Technologists®.

Aerobic stability of maize silage stored under plastic films with different oxygen permeability.

PubMed

Borreani, Giorgio; Piano, Serenella; Tabacco, Ernesto

2014-10-01

The most important factor that can influence silage quality is the degree of anaerobiosis maintained during conservation. The quality of the plastic film is a key factor, since the permeability of polyethylene to oxygen is too high for silage conservation. The aim of this work was to assess the effects of the interaction between three plastic films with different degrees of oxygen permeability and two different maize silage conservation times on fermentation, microbial quality and aerobic stability. The conservation time affected the pH, lactic and acetic acids, 1,2-propanediol and lactic/acetic acid ratio, with higher pH, lower lactic acid concentration and lactic/acetic acid ratio but higher acetic acid and 1,2-propanediol concentrations being found in silages conserved for 110 days versus silages conserved for 55 days. The plastic film affected the pH, lactic and acetic acids and lactic/acetic acid ratio. The yeast count was lower and aerobic stability higher for silage conserved under the oxygen barrier film for both conservation periods. The positive interaction between length of storage and the increased anaerobiosis of silage during conservation provided by the oxygen barrier compared with polyethylene film helped reduce the yeast count and increase the aerobic stability of maize silage, even when less acetic acid was produced during ensiling. © 2014 Society of Chemical Industry.

Stability of Atenolol, Clonazepam, Dexamethasone, Diclofenac Sodium, Diltiazem, Enalapril Maleate, Ketoprofen, Lamotrigine, Penicillamine-D, and Thiamine in SyrSpend SF PH4 Oral Suspensions.

PubMed

Polonini, Hudson C; Loures, Sharlene; Lima, Luis Claudio; Ferreira, Anderson O; Brandão, Marcos Antônio F

2016-01-01

The objective of this study was to evaluate the stability of 10 commonly used active pharmaceutical ingredients compounded in oral suspensions using SyrSpend SF PH4 (atenolol 1.0 and 5.0 mg/mL, clonazepam 0.2 mg/mL, dexamethasone 1.0 mg/mL, diclofenac sodium 5.0 mg/mL, diltiazem 12.0 mg/mL, enalapril maleate 1.0 mg/mL, ketoprofen 20.0 mg/mL, lamotrigine 1.0 mg/mL, penicillamine-D 50.0 mg/mL, thiamine 100 mg/m) and stored both at controlled refrigerated (2°C to 8°C) and room temperature (20°C to 25°C). Stability was assessed by means of measuring percent recovery at varying time points throughout a 90-day period. The quantification of the active pharmaceutical ingredients was performed by a stability-indicating, high-performance liquid chromatographic method. The beyond-use date of the products was found to be at least 90 days for all suspensions (except atenolol 1 mg/mL, which was stable up to 60 days), both for controlled refrigerated temperature and room temperature. This confirms that SyrSpend SF PH4 is a stable suspending vehicle for compounding with a broad range of different active pharmaceutical ingredients.

Validation of a high performance liquid chromatography method for the stabilization of epigallocatechin gallate.

PubMed

Fangueiro, Joana F; Parra, Alexander; Silva, Amélia M; Egea, Maria A; Souto, Eliana B; Garcia, Maria L; Calpena, Ana C

2014-11-20

Epigallocatechin gallate (EGCG) is a green tea catechin with potential health benefits, such as anti-oxidant, anti-carcinogenic and anti-inflammatory effects. In general, EGCG is highly susceptible to degradation, therefore presenting stability problems. The present paper was focused on the study of EGCG stability in HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) medium regarding the pH dependency, storage temperature and in the presence of ascorbic acid a reducing agent. The evaluation of EGCG in HEPES buffer has demonstrated that this molecule is not able of maintaining its physicochemical properties and potential beneficial effects, since it is partially or completely degraded, depending on the EGCG concentration. The storage temperature of EGCG most suitable to maintain its structure was shown to be the lower values (4 or -20 °C). The pH 3.5 was able to provide greater stability than pH 7.4. However, the presence of a reducing agent (i.e., ascorbic acid) was shown to provide greater protection against degradation of EGCG. A validation method based on RP-HPLC with UV-vis detection was carried out for two media: water and a biocompatible physiological medium composed of Transcutol®P, ethanol and ascorbic acid. The quantification of EGCG for purposes, using pure EGCG, requires a validated HPLC method which could be possible to apply in pharmacokinetic and pharmacodynamics studies. Copyright © 2014. Published by Elsevier B.V.

Impact of pH on the structure and function of neural cadherin.

PubMed

Jungles, Jared M; Dukes, Matthew P; Vunnam, Nagamani; Pedigo, Susan

2014-12-02

Neural (N-) cadherin is a transmembrane protein within adherens junctions that mediates cell-cell adhesion. It has 5 modular extracellular domains (EC1-EC5) that bind 3 calcium ions between each of the modules. Calcium binding is required for dimerization. N-Cadherin is involved in diverse processes including tissue morphogenesis, excitatory synapse formation and dynamics, and metastasis of cancer. During neurotransmission and tumorigenesis, fluctuations in extracellular pH occur, causing tissue acidosis with associated physiological consequences. Studies reported here aim to determine the effect of pH on the dimerization properties of a truncated construct of N-cadherin containing EC1-EC2. Since N-cadherin is an anionic protein, we hypothesized that acidification of solution would cause an increase in stability of the apo protein, a decrease in the calcium-binding affinity, and a concomitant decrease in the formation of adhesive dimer. The stability of the apo monomer was increased and the calcium-binding affinity was decreased at reduced pH, consistent with our hypothesis. Surprisingly, analytical SEC studies showed an increase in calcium-induced dimerization as solution pH decreased from 7.4 to 5.0. Salt-dependent dimerization studies indicated that electrostatic repulsion attenuates dimerization affinity. These results point to a possible electrostatic mechanism for moderating dimerization affinity of the Type I cadherin family. Extrapolating these results to cell adhesion in vivo leads to the assertion that decreased pH promotes adhesion by N-cadherin, thereby stabilizing synaptic junctions.

Effect of Salivary pH on Color Stability of Different Flowable Composites - A Prospective In-vitro Study.

PubMed

Batra, Renu; Kataria, Pratik; Kapoor, Sonali

2016-10-01

Scientifically and clinically there has been lot of development in the field of aesthetic dentistry. However, there is limited or restricted information regarding the color stability of flowable composite materials. The aim of this study was to evaluate the spectrophotometric color stability of three different flowable composite materials with respect to three different pH of saliva. The study included 90 different samples. Thirty samples in each composite group; (Group A: G-aenial universal flo; Group B: Z 350 XT flowable; Group C: Esthet x flow). All samples from each group were immersed in distilled water for 24 hours. Total color difference (ΔE) was recorded for each sample. After this 10 samples from each group were respectively immersed in 6.5, 7 and 7.5 pH of artificial saliva. All samples were kept in dark room for seven days and then ΔE for each sample was recorded and was compared to previous recorded ΔE for the same sample. Maximum color change was seen irrespective of material in 6.5 pH of saliva. G-aenial universal flo showed least change irrespective of pH of saliva. Thus, the present study reveals that acidic pH level affects the coloration of composite resins by affecting the surface integrity and as reported in previous studies, various coloring agents in beverages and other dietary components assists the process due to absorption of these coloring substances into the resin matrix.

A pH-responsive emulsion stabilized by alginate-grafted anisotropic silica and its application in the controlled release of λ-cyhalothrin.

PubMed

Chen, Kai; Yu, Gaobo; He, Furui; Zhou, Qingfeng; Xiao, Dunchao; Li, Jiacheng; Feng, Yuhong

2017-11-15

Alginate (Alg) was grafted on the surface of anisotropic silica (SiO 2 -x) via the Ugi reaction (Alg-SiO 2 -1, Alg-SiO 2 -2, and Alg-SiO 2 -4). Compared with pristine SiO 2 -x, modified SiO 2 -x is more sensitive to pH. Three stable liquid paraffin-in-water emulsions were prepared with Alg-SiO2-1, Alg-SiO2-2, and Alg-SiO2-4. Alg-SiO 2 -2 exhibited satisfactory emulsification ability. The emulsions became more stable as emulsion pH varied from 2.0 to 6.2 because of polymer chain interactions that led to the formation of a three-dimensional network. When the emulsion pH varied from 6.2 to 8.0, the particle charge increased, in turn increasing interparticle the electrostatic interactions that increased emulsion stability. When the emulsion pH was 9.0, the subsequent decrease in particle charge, decreased the emulsion stability. The model drug λ-cyhalothrin was embedded in the emulsions. A sustained-release assay demonstrated that increasing emulsion pH from 3.0 to 8.0 decreased cumulative drug release from the emulsion from 99.7% to 13.5%. This result indicated that the emulsion is a pH triggered drug delivery system. The sustained-release curves of λ-cyhalothrin are describable by the Weibull model. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Structure of Carbonic Anhydrase IX Is Adapted for Low-pH Catalysis.

PubMed

Mahon, Brian P; Bhatt, Avni; Socorro, Lilien; Driscoll, Jenna M; Okoh, Cynthia; Lomelino, Carrie L; Mboge, Mam Y; Kurian, Justin J; Tu, Chingkuang; Agbandje-McKenna, Mavis; Frost, Susan C; McKenna, Robert

2016-08-23

Human carbonic anhydrase IX (hCA IX) expression in many cancers is associated with hypoxic tumors and poor patient outcome. Inhibitors of hCA IX have been used as anticancer agents with some entering Phase I clinical trials. hCA IX is transmembrane protein whose catalytic domain faces the extracellular tumor milieu, which is typically associated with an acidic microenvironment. Here, we show that the catalytic domain of hCA IX (hCA IX-c) exhibits the necessary biochemical and biophysical properties that allow for low pH stability and activity. Furthermore, the unfolding process of hCA IX-c appears to be reversible, and its catalytic efficiency is thought to be correlated directly with its stability between pH 3.0 and 8.0 but not above pH 8.0. To rationalize this, we determined the X-ray crystal structure of hCA IX-c to 1.6 Å resolution. Insights from this study suggest an understanding of hCA IX-c stability and activity in low-pH tumor microenvironments and may be applicable to determining pH-related effects on enzymes.

Thermal stability and structural characterization of organic/inorganic hybrid nonlinear optical material containing a two-dimensional chromophore.

PubMed

Chang, Po-Hsun; Tsai, Hsieh-Chih; Chen, Yu-Ren; Chen, Jian-Yu; Hsiue, Ging-Ho

2008-10-21

In this study, two nonlinear optic hybrid materials with different dimensional alkoxysilane dyes were prepared and characterized. One NLO silane (Cz2PhSO 2OH- TES), a two-dimensional structure based on carbazole, had a larger rotational volume than the other (DR19-TES). Second harmonic ( d 33) analysis verified there is an optimum heating process for the best poling efficiency. The maximum d 33 value of NLO hybrid film containing Cz2PhSO 2OH was obtained for 10.7 pm/V after precuring at 150 degrees C for 3 h and poling at 210 degrees C for 60 min. The solid-state (29)Si NMR spectrum shows that the main factor influencing poling efficiency and thermal stability was cross-linking degree of NLO silane, but not that of TMOS. In particular, the two-dimensional sol-gel system has a greater dynamic and temporary stability than the one-dimensional system due to Cz2PhSO 2OH-TES requiring a larger volume to rotate in the hybrid matrix after cross-linking.

Stabilization of Cr(VI) from fine ferrochrome dust using exfoliated vermiculite.

PubMed

Mulange Wa Mulange, Delphin; Garbers-Craig, Andrie Mariana

2012-07-15

This study proved that vermiculite, a natural occurring mineral, can effectively remove and stabilize Cr(VI) from fine ferrochrome dust leachate. Batch adsorption studies were carried out to determine the effect of pH, contact time and adsorbent dose on the removal of Cr(VI). The process was found to be highly pH dependent. The optimum conditions for the Cr(VI) removal are at a pH of 1.5, contact time of 2h and adsorbent dose of 10gL(-1). The stability of the Cr(VI)-loaded vermiculite remained unchanged after 12 months, when the vermiculite was evaluated with the ASTM and TCLP Cr(VI) leach methods. However, Cr(VI) desorption did take place when the Acid Rain Test was used. The adsorption kinetic data fits the pseudo-second order model, while the equilibrium data of Cr(VI) adsorption onto vermiculite are best described by the Langmuir isotherm. The presence of hydrobiotite and biotite in the industrial vermiculite slightly decreased the degree of adsorption of Cr(VI). Copyright © 2012 Elsevier B.V. All rights reserved.

Effects of pH on nano-bubble stability and transport in saturated porous media

NASA Astrophysics Data System (ADS)

Hamamoto, Shoichiro; Takemura, Takato; Suzuki, Kenichiro; Nishimura, Taku

2018-01-01

An understanding of nano-scale bubble (NB) transport in porous media is important for potential application of NBs in soil/groundwater remediation. It is expected that the solution chemistry of NB water highly influences the surface characteristics of NBs and porous media and the interaction between them, thus affecting the stability and transport characteristics of NB. In this study, in addition to stability experiments, one-dimensional column transport experiments using glass beads were conducted to investigate the effects of pH on the NB transport behavior. The results showed that the NBs were more stable under higher pH. Column transport experiments revealed that entrapment of NBs, especially larger ones, was enhanced in lower-pH water, likely suggesting pH-dependent NB attachment and physical straining, both of which are also probably influenced by bubble size. Although relatively smaller NBs were released after switching the eluting fluid to one with lower ionic strength, most of the NBs in lower-pH water were still retained in the porous media even altering the chemical condition.

Influence of pH, curing time and environmental stress on the immobilization of hazardous waste using activated fly ash.

PubMed

Srivastava, Shefali; Chaudhary, Rubina; Khale, Divya

2008-05-30

The current work is related to inorganic species in sludge generated from Common Effluent Treatment Plant contaminated with hazardous wastes at relatively high concentration. The environmental sensitive metals studied in the sludge are Pb, Fe, Ni, Zn and Mn. The solidification/stabilization (S/S) of heavy metals within fly ash-cement-based matrix was conducted for low cost treatment and reuse of sludge. The study examines the strength of the S/S product by predicting the effect of supplementary cementing material from efficiency factor (k) at 60 degrees C curing temperature. The leaching test was performed at two different pH 7 and 4 to determine the efficiency of heavy metal immobilization. It was observed that replacing 76% OPC by 56% fly ash and 20% sludge for 28 days curing period shows increase in strength as well as rate of stabilization for zinc, iron and manganese at pH 7, lead and nickel were stabilized by 79 and 82%, respectively. Environmental stress test was performed to evaluate the tolerance of extreme adverse environmental condition.

Coordination-Enabled One-Step Assembly of Ultrathin, Hybrid Microcapsules with Weak pH-Response.

PubMed

Yang, Chen; Wu, Hong; Yang, Xiao; Shi, Jiafu; Wang, Xiaoli; Zhang, Shaohua; Jiang, Zhongyi

2015-05-06

In this study, an ultrathin, hybrid microcapsule is prepared though coordination-enabled one-step assembly of tannic acid (TA) and titanium(IV) bis(ammonium lactate) dihydroxide (Ti-BALDH) upon a hard-templating method. Briefly, the PSS-doped CaCO3 microspheres with a diameter of 5-8 μm were synthesized and utilized as the sacrificial templates. Then, TA-Ti(IV) coatings were formed on the surface of the PSS-doped CaCO3 templates through soaking in TA and Ti-BALDH aqueous solutions under mild conditions. After removing the template by EDTA treatment, the TA-Ti(IV) microcapsules with a capsule wall thickness of 15 ± 3 nm were obtained. The strong coordination bond between polyphenol and Ti(IV) conferred the TA-Ti(IV) microcapsules high structural stability in the range of pH values 3.0-11.0. Accordingly, the enzyme-immobilized TA-Ti(IV) microcapsules exhibited superior pH and thermal stabilities. This study discloses the formation of TA-Ti(IV) microcapsules that are suitable for use as supports in catalysis due to their extensive pH and thermal stabilities.

Effects of pH on nano-bubble stability and transport in saturated porous media.

PubMed

Hamamoto, Shoichiro; Takemura, Takato; Suzuki, Kenichiro; Nishimura, Taku

2018-01-01

An understanding of nano-scale bubble (NB) transport in porous media is important for potential application of NBs in soil/groundwater remediation. It is expected that the solution chemistry of NB water highly influences the surface characteristics of NBs and porous media and the interaction between them, thus affecting the stability and transport characteristics of NB. In this study, in addition to stability experiments, one-dimensional column transport experiments using glass beads were conducted to investigate the effects of pH on the NB transport behavior. The results showed that the NBs were more stable under higher pH. Column transport experiments revealed that entrapment of NBs, especially larger ones, was enhanced in lower-pH water, likely suggesting pH-dependent NB attachment and physical straining, both of which are also probably influenced by bubble size. Although relatively smaller NBs were released after switching the eluting fluid to one with lower ionic strength, most of the NBs in lower-pH water were still retained in the porous media even altering the chemical condition. Copyright © 2017 Elsevier B.V. All rights reserved.

Accelerated Stability Testing of a Clobetasol Propionate-Loaded Nanoemulsion as per ICH Guidelines.

PubMed

Ali, Mohammad Sajid; Alam, Mohammad Sarfaraz; Alam, Nawazish; Anwer, Tarique; Safhi, Mohammed Mohsen A

2013-01-01

The physical and chemical degradation of drugs may result in altered therapeutic efficacy and even toxic effects. Therefore, the objective of this work was to study the stability of clobetasol propionate (CP) in a nanoemulsion. The nanoemulsion formulation containing CP was prepared by the spontaneous emulsification method. For the formulation of the nanoemulsion, Safsol, Tween 20, ethanol, and distilled water were used. The drug was incorporated into an oil phase in 0.05% w/v. The lipophilic nature of the drug led to the O/W nanoemulsion formulation. This was characterized by droplet size, pH, viscosity, conductivity, and refractive index. Stability studies were performed as per ICH guidelines for a period of three months. The shelf life of the nanoemulsion formulation was also determined after performing accelerated stability testing (40°C ± 2°C and 75% ± 5% RH). We also performed an intermediate stability study (30°C ± 2°C/65% RH ± 5% RH). It was found that the droplet size, conductivity, and refractive index were slightly increased, while the viscosity and pH slightly decreased at all storage conditions during the 3-month period. However, the changes in these parameters were not statistically significant (p≥0.05). The degradation (%) of the optimized nanoemulsion of CP was determined and the shelf life was found to be 2.18 years at room temperature. These studies confirmed that the physical and chemical stability of CP were enhanced in the nanoemulsion formulation.

SAT2 Foot-and-Mouth Disease Virus Structurally Modified for Increased Thermostability.

PubMed

Scott, Katherine A; Kotecha, Abhay; Seago, Julian; Ren, Jingshan; Fry, Elizabeth E; Stuart, David I; Charleston, Bryan; Maree, Francois F

2017-05-15

Foot-and-mouth disease virus (FMDV), particularly strains of the O and SAT serotypes, is notoriously unstable. Consequently, vaccines derived from heat-labile SAT viruses have been linked to the induction of immunity with a poor duration and hence require more frequent vaccinations to ensure protection. In silico calculations predicted residue substitutions that would increase interactions at the interpentamer interface, supporting increased stability. We assessed the stability of the 18 recombinant mutant viruses in regard to their growth kinetics, antigenicity, plaque morphology, genetic stability, and temperature, ionic, and pH stability by using Thermofluor and inactivation assays in order to evaluate potential SAT2 vaccine candidates with improved stability. The most stable mutant for temperature and pH stability was the S2093Y single mutant, while other promising mutants were the E3198A, L2094V, and S2093H single mutants and the F2062Y-H2087M-H3143V triple mutant. Although the S2093Y mutant had the greatest stability, it exhibited smaller plaques, a reduced growth rate, a change in monoclonal antibody footprint, and poor genetic stability properties compared to those of the wild-type virus. However, these factors affecting production can be overcome. The addition of 1 M NaCl was found to further increase the stability of the SAT2 panel of viruses. The S2093Y and S2093H mutants were selected for future use in stabilizing SAT2 vaccines. IMPORTANCE Foot-and-mouth disease virus (FMDV) causes a highly contagious acute vesicular disease in cloven-hoofed livestock and wildlife. The control of the disease by vaccination is essential, especially at livestock-wildlife interfaces. The instability of some serotypes, such as SAT2, affects the quality of vaccines and therefore the duration of immunity. We have shown that we can improve the stability of SAT2 viruses by mutating residues at the capsid interface through predictive modeling. This is an important finding for the potential use of such mutants in improving the stability of SAT2 vaccines in countries where FMD is endemic, which rely heavily on the maintenance of the cold chain, with potential improvement to the duration of immune responses. Copyright © 2017 American Society for Microbiology.

SAT2 Foot-and-Mouth Disease Virus Structurally Modified for Increased Thermostability

PubMed Central

Scott, Katherine A.; Kotecha, Abhay; Seago, Julian; Ren, Jingshan; Fry, Elizabeth E.; Stuart, David I.; Charleston, Bryan

2017-01-01

ABSTRACT Foot-and-mouth disease virus (FMDV), particularly strains of the O and SAT serotypes, is notoriously unstable. Consequently, vaccines derived from heat-labile SAT viruses have been linked to the induction of immunity with a poor duration and hence require more frequent vaccinations to ensure protection. In silico calculations predicted residue substitutions that would increase interactions at the interpentamer interface, supporting increased stability. We assessed the stability of the 18 recombinant mutant viruses in regard to their growth kinetics, antigenicity, plaque morphology, genetic stability, and temperature, ionic, and pH stability by using Thermofluor and inactivation assays in order to evaluate potential SAT2 vaccine candidates with improved stability. The most stable mutant for temperature and pH stability was the S2093Y single mutant, while other promising mutants were the E3198A, L2094V, and S2093H single mutants and the F2062Y-H2087M-H3143V triple mutant. Although the S2093Y mutant had the greatest stability, it exhibited smaller plaques, a reduced growth rate, a change in monoclonal antibody footprint, and poor genetic stability properties compared to those of the wild-type virus. However, these factors affecting production can be overcome. The addition of 1 M NaCl was found to further increase the stability of the SAT2 panel of viruses. The S2093Y and S2093H mutants were selected for future use in stabilizing SAT2 vaccines. IMPORTANCE Foot-and-mouth disease virus (FMDV) causes a highly contagious acute vesicular disease in cloven-hoofed livestock and wildlife. The control of the disease by vaccination is essential, especially at livestock-wildlife interfaces. The instability of some serotypes, such as SAT2, affects the quality of vaccines and therefore the duration of immunity. We have shown that we can improve the stability of SAT2 viruses by mutating residues at the capsid interface through predictive modeling. This is an important finding for the potential use of such mutants in improving the stability of SAT2 vaccines in countries where FMD is endemic, which rely heavily on the maintenance of the cold chain, with potential improvement to the duration of immune responses. PMID:28298597

PHYSICAL AND CHEMICAL STABILITY ANALYSIS OF COSMETIC MULTI- PLE EMULSIONS LOADED WITH ASCORBYL PALMITATE AND SODIUM ASCORBYL PHOSPHATE SALTS.

PubMed

Khan, Hira; Akhtar, Naveed; Ali, Atif; Khan, Haji M Shoaib; Sohail, Muhammad; Naeem, Muhammad; Nawaz, Zarqa

2016-09-01

Stability of hydrophilic and lipophilic vitamin C derivatives for quenching synergistic antioxidant activities and to treat oxidative related diseases is a major issue. This study was aimed to encapsulate hydrophilic and lipophilic vitamin C derivatives (ascorbyl palmitate and sodium ascorbyl phosphate) as functional ingredients in a newly formulated multiple emulsion of the W//W type to attain the synergistic antioxidant effects and the resultant system's long term physical and chemical stability. Several multiple emulsions using the same concentration of emulsifiers but different concentrations of ascorbyl palmitate and sodium ascorbyl phosphate were developed. Three finally selected multiple emulsions (ME₁, ME₂ and ME₃) were evaluated for physical stability in terms of rheology, microscopy, conductivity, pH, and organoleptic characteristics under different storage conditions for 3 months. Chemical stability was determined by HPLC on Sykam GmbH HPLC system (Germany), equipped with a variable UV detector. Results showed that at accelerated storage conditions all the three multiple emulsions had shear thinning behavior of varying shear stress with no influence of location of functional ingredients in a carrier system. Conductivity values increased and pH values remained within the skin pH range for 3 months. Microscopic analysis showed an increase in globule size with the passage of time, especially at higher temperatures while decreased at low temperatures. Centrifugation test did not cause phase separation till the 45th day, but little effects after 2 months. Chemical stability analysis by HPLC at the end of 3 months showed that ascorbyl palmitate and sodium ascorbyl phosphate were almost stable in all multiple emulsions with no influence of their location in a carrier system. Multiple emulsions were found a stable carrier for hydrophilic and lipophilic vitamin C derivatives to enhance their desired effects. Considering that many topical formulations contain simple vitamin C it is suggested that present study may contribute to the development of more stable formulations with a combination of vitamin C derivatives to enhance their cosmetic benefits.

Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part I—Storage performance

DOE PAGES

Wendt, Lynn M.; Wahlen, Bradley D.; Li, Chenlin; ...

2017-06-01

Here, algal biomass is becoming increasingly attractive as a feedstock for biofuel production. However, the swing in algal biomass production between summer and winter months poses a challenge for delivering predictable, constant feedstock supply to a conversion facility. Drying is one approach for stabilizing algal biomass produced in excess during high productivity summer months for utilization during low productivity months, yet drying is energy intensive and thus costly. Wet, anaerobic storage, or ensiling, is a low-cost approach that is commonly used to preserve high moisture herbaceous feedstock. The potential for microalgae stabilization without the need for drying was investigated inmore » this study by simulating ensiling, in which oxygen limitation drives anaerobic fermentation of soluble sugars to organic acids, dropping the pH and thereby stabilizing the material. Algal biomass, Scenedesmus obliquus, was blended with corn stover and stored in acidic, anaerobic conditions at 60% moisture (wet basis) to simulate wet storage by means of ensiling. Results demonstrate that algae and corn stover blends were successfully preserved in anaerobic, acidic conditions for 30 days with < 2% dry matter loss occurring during storage compared to 21% loss in aerobic, non-acidified conditions. Likewise, Scenedesmus obliquus stored alone at 80% moisture (wet basis) in acidified, anaerobic conditions for 30 days, resulted in dry matter losses of 6–14%, compared to 44% loss in neutral pH, anaerobic storage and 37% loss in a neutral pH, aerobically stored condition. Additional experiments were performed at a larger scale in which an algae and corn stover blend was subject to mechanical oxygen exclusion and a Lactobacillus acidophilus inoculum, resulting in 8% loss over 35 days and further indicating that acidic, anaerobic conditions can stabilize microalgae biomass. In summary, the stabilization of harvested algae can be achieved through anaerobic storage, securing a feedstock that is labile yet of high value.« less

Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part I—Storage performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendt, Lynn M.; Wahlen, Bradley D.; Li, Chenlin

Here, algal biomass is becoming increasingly attractive as a feedstock for biofuel production. However, the swing in algal biomass production between summer and winter months poses a challenge for delivering predictable, constant feedstock supply to a conversion facility. Drying is one approach for stabilizing algal biomass produced in excess during high productivity summer months for utilization during low productivity months, yet drying is energy intensive and thus costly. Wet, anaerobic storage, or ensiling, is a low-cost approach that is commonly used to preserve high moisture herbaceous feedstock. The potential for microalgae stabilization without the need for drying was investigated inmore » this study by simulating ensiling, in which oxygen limitation drives anaerobic fermentation of soluble sugars to organic acids, dropping the pH and thereby stabilizing the material. Algal biomass, Scenedesmus obliquus, was blended with corn stover and stored in acidic, anaerobic conditions at 60% moisture (wet basis) to simulate wet storage by means of ensiling. Results demonstrate that algae and corn stover blends were successfully preserved in anaerobic, acidic conditions for 30 days with < 2% dry matter loss occurring during storage compared to 21% loss in aerobic, non-acidified conditions. Likewise, Scenedesmus obliquus stored alone at 80% moisture (wet basis) in acidified, anaerobic conditions for 30 days, resulted in dry matter losses of 6–14%, compared to 44% loss in neutral pH, anaerobic storage and 37% loss in a neutral pH, aerobically stored condition. Additional experiments were performed at a larger scale in which an algae and corn stover blend was subject to mechanical oxygen exclusion and a Lactobacillus acidophilus inoculum, resulting in 8% loss over 35 days and further indicating that acidic, anaerobic conditions can stabilize microalgae biomass. In summary, the stabilization of harvested algae can be achieved through anaerobic storage, securing a feedstock that is labile yet of high value.« less

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces.

PubMed

Manga, Mohamed S; Hunter, Timothy N; Cayre, Olivier J; York, David W; Reichert, Matthew D; Anna, Shelly L; Walker, Lynn M; Williams, Richard A; Biggs, Simon R

2016-05-03

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher than previously reported for nanoparticle and surfactant systems, and similar in magnitude to protein stabilized droplets.

Functional Properties of Pea (Pisum sativum, L.) Protein Isolates Modified with Chymosin

PubMed Central

Barać, Miroljub; Čabrilo, Slavica; Pešić, Mirjana; Stanojević, Slađana; Pavlićević, Milica; Maćej, Ognjen; Ristić, Nikola

2011-01-01

In this paper, the effects of limited hydrolysis on functional properties, as well as on protein composition of laboratory-prepared pea protein isolates, were investigated. Pea protein isolates were hydrolyzed for either 15, 30 and 60 min with recombined chymosin (Maxiren). The effect of enzymatic action on solubility, emulsifying and foaming properties at different pH values (3.0; 5.0; 7.0 and 8.0) was monitored. Chymosin can be a very useful agent for improvement of functional properties of isolates. Action of this enzyme caused a low degree of hydrolysis (3.9–4.7%), but improved significantly functional properties of pea protein isolates (PPI), especially at lower pH values (3.0–5.0). At these pH values all hydrolysates had better solubility, emulsifying activity and foaming stability, while longer-treated samples (60 min) formed more stable emulsions at higher pH values (7.0, 8.0) than initial isolates. Also, regardless of pH value, all hydrolysates showed improved foaming ability. A moderate positive correlation between solubility and emulsifying activity index (EAI) (0.74) and negative correlation between solubility and foam stability (−0.60) as well as between foam stability (FS) and EAI (−0.77) were observed. Detected enhancement in functional properties was a result of partial hydrolysis of insoluble protein complexes. PMID:22272078

Anaerobic digestion of municipal solid wastes containing variable proportions of waste types.

PubMed

Akunna, J C; Abdullahi, Y A; Stewart, N A

2007-01-01

In many parts of the world there are significant seasonal variations in the production of the main organic wastes, food and green wastes. These waste types display significant differences in their biodegradation rates. This study investigated the options for ensuring process stability during the start up and operation of thermophilic high-solids anaerobic digestion of feedstock composed of varying proportions of food and green wastes. The results show that high seed sludge to feedstock ratio (or low waste loading rate) is necessary for ensuring process pH stability without chemical addition. It was also found that the proportion of green wastes in the feedstock can be used to regulate process pH, particularly when operating at high waste loading rates (or low seed sludge to feedstock ratios). The need for chemical pH correction during start-up and digestion operation decreased with increase in green wastes content of the feedstock. Food wastes were found to be more readily biodegradable leading to higher solids reduction while green wastes brought about pH stability and higher digestate solid content. Combining both waste types in various proportions brought about feedstock with varying buffering capacity and digestion performance. Thus, careful selection of feedstock composition can minimise the need for chemical pH regulation as well as reducing the cost for digestate dewatering for final disposal.

Modulating secretory pathway pH by proton channel co-expression can increase recombinant protein stability in plants.

PubMed

Jutras, Philippe V; D'Aoust, Marc-André; Couture, Manon M-J; Vézina, Louis-Philippe; Goulet, Marie-Claire; Michaud, Dominique; Sainsbury, Frank

2015-09-01

Eukaryotic expression systems are used for the production of complex secreted proteins. However, recombinant proteins face considerable biochemical challenges along the secretory pathway, including proteolysis and pH variation between organelles. As the use of synthetic biology matures into solutions for protein production, various host-cell engineering approaches are being developed to ameliorate host-cell factors that can limit recombinant protein quality and yield. We report the potential of the influenza M2 ion channel as a novel tool to neutralize the pH in acidic subcellular compartments. Using transient expression in the plant host, Nicotiana benthamiana, we show that ion channel expression can significantly raise pH in the Golgi apparatus and that this can have a strong stabilizing effect on a fusion protein separated by an acid-susceptible linker peptide. We exemplify the utility of this effect in recombinant protein production using influenza hemagglutinin subtypes differentially stable at low pH; the expression of hemagglutinins prone to conformational change in mildly acidic conditions is considerably enhanced by M2 co-expression. The co-expression of a heterologous ion channel to stabilize acid-labile proteins and peptides represents a novel approach to increasing the yield and quality of secreted recombinant proteins in plants and, possibly, in other eukaryotic expression hosts. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of acidic pH on the stability of α-synuclein dimers.

PubMed

Lv, Zhengjian; Krasnoslobodtsev, Alexey V; Zhang, Yuliang; Ysselstein, Daniel; Rochet, Jean Christophe; Blanchard, Scott C; Lyubchenko, Yuri L

2016-10-01

Environmental factors, such as acidic pH, facilitate the assembly of α-synuclein (α-Syn) in aggregates, but the impact of pH on the very first step of α-Syn aggregation remains elusive. Recently, we developed a single-molecule approach that enabled us to measure directly the stability of α-Syn dimers. Unlabeled α-Syn monomers were immobilized on a substrate, and fluorophore-labeled monomers were added to the solution to allow them to form dimers with immobilized α-Syn monomers. The dimer lifetimes were measured directly from the fluorescence bursts on the time trajectories. Herein, we applied the single-molecule tethered approach for probing of intermolecular interaction to characterize the effect of acidic pH on the lifetimes of α-Syn dimers. The experiments were performed at pH 5 and 7 for wild-type α-Syn and for two mutants containing familial type mutations E46K and A53T. We demonstrate that a decrease of pH resulted in more than threefold increase in the α-Syn dimers lifetimes with some variability between the α-Syn species. We hypothesize that the stabilization effect is explained by neutralization of residues 96-140 of α-Syn and this electrostatic effect facilitates the association of the two monomers. Given that dimerization is the first step of α-Syn aggregation, we posit that the electrostatic effect thereby contributes to accelerating α-Syn aggregation at acidic pH. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 715-724, 2016. © 2016 Wiley Periodicals, Inc.

Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Applegate, Brian E.; Park, Jesung; Carbajal, Esteban

Phase-sensitive Optical Coherence Tomography (PhOCT) is an emerging tool for in vivo investigation of the vibratory function of the intact middle and inner ear. PhOCT is able to resolve micron scale tissue morphology in three dimensions as well as measure picometer scale motion at each spatial position. Most PhOCT systems to date have relied upon the phase stability offered by spectrometer detection. On the other hand swept laser source based PhOCT offers a number of advantages including balanced detection, long imaging depths, and high imaging speeds. Unfortunately the inherent phase instability of traditional swept laser sources has necessitated complex usermore » developed hardware/software solutions to restore phase sensitivity. Here we present recent results using a prototype swept laser that overcomes these issues. The akinetic swept laser is electronically tuned and precisely controls sweeps without any mechanical movement, which results in high phase stability. We have developed an optical fiber based PhOCT system around the akinetic laser source that had a 1550 nm center wavelength and a sweep rate of 140 kHz. The stability of the system was measured to be 4.4 pm with a calibrated reflector, thus demonstrating near shot noise limited performance. Using this PhOCT system, we have acquired structural and vibratory measurements of the middle ear in a mouse model, post mortem. The quality of the results suggest that the akinetic laser source is a superior laser source for PhOCT with many advantages that greatly reduces the required complexity of the imaging system.« less

An amperometric biosensor for glucose detection from glucose oxidase immobilized in polyaniline-polyvinylsulfonate-potassium ferricyanide film.

PubMed

Arslan, Fatma; Beskan, Umut

2014-08-01

In this study, a novel amperometric glucose biosensor with immobilization of glucose oxidase on electrochemically polymerized polyaniline-polyvinylsulphonate-potassium ferricyanide (Pani-Pvs-Fc) films has been accomplished via the entrapment technique. Potassium ferricyanide was used as the mediator. Determination of glucose was carried out by the oxidation of potassium ferrocyanide at 0.3 V vs. Ag/AgCl. The effects of pH and temperature were investigated, and the optimum pH value was found to be 7.5. The storage stability and the operational stability of the enzyme electrode were also studied.

On the origin of the halo stabilization.

PubMed

Trulsson, Martin; Jönsson, Bo; Labbez, Christophe

2013-01-14

Monte Carlo simulations show that charge-regulation alone can cause highly charged zirconium nanoparticles to adsorb to a similarly charged or neutral silica particle and thereby stabilizing the latter. This mechanism, referred to as halo stabilization, is quite general and applicable in a range of systems provided that pH, van der Waals forces, and dissociation constants of the charge-regulating particles are properly chosen. In our modeling we see an overall attraction at low volume fractions of nanoparticles, while at higher a repulsive barrier is created, stabilizing the microparticles and protecting them from aggregation. The charge-regulation mechanism also turns the silica surface from positively charged, without nanoparticles, to negatively charged in the presence of nanoparticles.

Development of lysozyme-combined antibacterial system to reduce sulfur dioxide and to stabilize Italian Riesling ice wine during aging process

PubMed Central

Chen, Kai; Han, Shun-yu; Zhang, Bo; Li, Min; Sheng, Wen-jun

2015-01-01

For the purpose of SO2 reduction and stabilizing ice wine, a new antibacterial technique was developed and verified in order to reduce the content of sulfur dioxide (SO2) and simultaneously maintain protein stability during ice wine aging process. Hazardous bacterial strain (lactic acid bacteria, LAB) and protein stability of Italian Riesling ice wine were evaluated in terms of different amounts of lysozyme, SO2, polyphenols, and wine pH by single-factor experiments. Subsequently, a quadratic rotation-orthogonal composite design with four variables was conducted to establish the multiple linear regression model that demonstrated the influence of different treatments on synthesis score between LAB inhibition and protein stability of ice wine. The results showed that, synthesis score can be influenced by lysozyme and SO2 concentrations on an extremely significant level (P < 0.01). Furthermore, the lysozyme-combined antibacterial system, which is specially designed for ice wine aging, was optimized step by step by response surface methodology and ridge analysis. As a result, the optimal proportion should be control in ice wine as follows: 179.31 mg L−1 lysozyme, 177.14 mg L−1 SO2, 0.60 g L−1 polyphenols, and 4.01 ice wine pH. Based on this system, the normalized synthesis score between LAB inhibition and protein stability can reach the highest point 0.920. Finally, by the experiments of verification and comparison, it was indicated that lysozyme-combined antibacterial system, which was a practical and prospective method to reduce SO2 concentration and effectively prevent contamination from hazardous LAB, can be used to stabilize ice wine during aging process. PMID:26405531

Similar influence of stabilized alkaline and neutral sodium hypochlorite solutions on the fracture resistance of root canal-treated bovine teeth.

PubMed

Souza, Erick Miranda; Calixto, Amanda Martins; Lima, Camila Nara E; Pappen, Fernanda Geraldo; De-Deus, Gustavo

2014-10-01

Stabilizing sodium hypochlorite (NaOCl) at an alkaline pH is proposed to increase solution stability and tissue dissolution ability; however, a reduction on the flexural strength of dentin discs has been found to be a side effect. This study sought to determine whether a stabilized alkaline NaOCl reduces the fracture resistance of root canal-treated bovine teeth after root canal preparation compared with a neutral solution counterpart. The 4 anterior incisors were removed from 20 mandibular bovine jaws, and each 1 was randomly assigned to 1 of 4 groups (20 teeth each). Teeth were prepared with a sequence of 6 K-type files. The following experimental groups received a different irrigation regimen: G1: distilled water (negative control), G2: 5% NaOCl at a pH of 7.2, and G3: 5% NaOCl at a pH of 12.8; in the positive control group (G4), teeth remained untreated. The time of contact and volume of solution were carefully standardized. After bone and periodontal ligament simulation, teeth were subjected to a fracture resistance test. A significant difference was observed among the 4 groups tested (analysis of variance, P < .05). The 5% NaOCl groups (G2 and G3) presented significantly lower resistance to fracture than the control (G1 and G4) (Tukey test, P < .05). Both NaOCl solutions similarly reduced the fracture resistance at approximately 30% (Tukey test, P > .05). No differences were observed between positive and negative control groups (Tukey test, P > .05). Stabilized alkaline and neutral NaOCl solutions similarly reduced the fracture resistance of root canal-treated bovine teeth by about 30%. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Substituent effects and pH profiles for stability constants of arylboronic acid diol esters.

PubMed

Martínez-Aguirre, Mayte A; Villamil-Ramos, Raul; Guerrero-Alvarez, Jorge A; Yatsimirsky, Anatoly K

2013-05-17

Stability constants of boronic acid diol esters in aqueous solution have been determined potentiometrically for a series of meta-, para-substituted phenylboronic acids and diols of variable acidity. The constants β(11-1) for reactions between neutral forms of reactants producing the anionic ester plus proton follow the Hammett equation with ρ depending on pKa of diol and varying from 2.0 for glucose to 1.29 for 4-nitrocatechol. Observed stability constants (K(obs)) measured by UV-vis and fluorometric titrations at variable pH for esters of 4,5-dihydroxy-1,3-benzenedisulfonate (Tiron) generally agree with those expected on the basis of β(11-1) values, but the direct fitting of K(obs) vs pH profiles gives shifted pKa values both for boronic acids and diol as a result of significant interdependence of fitting parameters. The subsituent effects on absorption and fluorescence spectra of Tiron arylboronate esters are characterized. The K(obs) for Tiron determined by (11)B NMR titrations are approximately 1 order of magnitude smaller than those determined by UV-vis titrations under identical conditions. A general equation, which makes possible an estimate of β(11-1) for any pair of boronic acid and diol from their pKa values, is proposed on the basis of established Brönsted-type correlation of Hammett parameters for β(11-1) with acidity of diols. The equation allows one to calculate stability constants expected only on basis of acid-base properties of the components, thus permitting more strict evaluation of contributions of additional factors such as steric or charge effects to the ester stability.

Bacterial exopolysaccharides as a modern biotechnological tool for modification of fungal laccase properties and metal ion binding.

PubMed

Osińska-Jaroszuk, Monika; Jaszek, Magdalena; Starosielec, Magdalena; Sulej, Justyna; Matuszewska, Anna; Janczarek, Monika; Bancerz, Renata; Wydrych, Jerzy; Wiater, Adrian; Jarosz-Wilkołazka, Anna

2018-03-26

Four bacterial EPSs extracted from Rhizobium leguminosarum bv. trifolii Rt24.2, Sinorhizobium meliloti Rm1021, Bradyrhizobium japonicum USDA110, and Bradyrhizobium elkanii USDA76 were determined towards their metal ion adsorption properties and possible modification of Cerrena unicolor laccase properties. The highest magnesium and iron ion-sorption capacity (~ 42 and ~ 14.5%, respectively) was observed for EPS isolated from B. japonicum USDA110. An evident influence of EPSs on the stability of laccase compared to the control values (without EPSs) was shown after 30-day incubation at 25 °C. The residual activity of laccases was obtained in the presence of Rh76EPS and Rh1021EPS, i.e., 49.5 and 41.5% of the initial catalytic activity, respectively. This result was confirmed by native PAGE electrophoresis. The EPS effect on laccase stability at different pH (from 3.8 to 7.0) was also estimated. The most significant changes at the optimum pH value (pH 5.8) was observed in samples of laccase stabilized by Rh76EPS and Rh1021EPS. Cyclic voltamperometry was used for analysis of electrochemical parameters of laccase stabilized by bacterial EPS and immobilized on single-walled carbon nanotubes (SWCNTs) with aryl residues. Laccases with Rh76EPS and Rh1021EPS had an evident shift of the value of the redox potential compared to the control without EPS addition. In conclusion, the results obtained in this work present a new potential use of bacterial EPSs as a metal-binding component and a modulator of laccase properties especially stability of enzyme activity, which can be a very effective tool in biotechnology and industrial applications.

ON THE RELATIVE STABILITY OF ALUMINUM, TITANIUM, VANADIUM, IRON, AND COPPER TARTRATE COMPLEXES IN ALKALI MEDIA (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyatnitskii, I.V.; Kostyshina, A.P.

1959-06-01

The stability of aluminum, copper, iron, titunium, and vanadium tartrate complexes was determined using bond magnitudes as criteria (the ratio between the concentrations of complexed and free ions at a certain standard acid condition). A method is suggested for determining the ratio of the bonds combining the complexes of two metals. The partition constaats of aluminum, copper, iron(III), and vanadium hydroxyquinolinates between the aqueous solution and chloroform were 2.6 x 10/sup -33/, 7.3 x 10/sup -23/, 1.5 x 10/sup -37/, and 4.2 x 10/sup -23/, respectively. The relative stability of copper and iron turtrate complexes in alkali solution (pH 13)more » and aluminum, iron(III), titunium, and vanadium(IV) tartrate complexes in ammonium solution (pH 9.5) was determined. (R.V.J.)« less

Green coconut fiber: a novel carrier for the immobilization of commercial laccase by covalent attachment for textile dyes decolourization.

PubMed

Cristóvão, Raquel O; Silvério, Sara C; Tavares, Ana P M; Brígida, Ana Iraidy S; Loureiro, José M; Boaventura, Rui A R; Macedo, Eugénia A; Coelho, Maria Alice Z

2012-09-01

Commercial laccase formulation was immobilized on modified green coconut fiber silanized with 3-glycidoxypropyltrimethoxysilane, aiming to achieve a cheap and effective biocatalyst. Two different strategies were followed: one point (pH 7.0) and multipoint (pH 10.0) covalent attachment. The influence of immobilization time on enzymatic activity and the final reduction with sodium borohydride were evaluated. The highest activities were achieved after 2 h of contact time in all situations. Commercial laccase immobilized at pH 7.0 was found to have higher activity and higher affinity to the substrate. However, the immobilization by multipoint covalent attachment improved the biocatalyst thermal stability at 50 °C, when compared to soluble enzyme and to the immobilized enzyme at pH 7.0. The Schiff's bases reduction by sodium borohydride, in spite of causing a decrease in enzyme activity, showed to contribute to the increase of operational stability through bonds stabilization. Finally, these immobilized enzymes showed high efficiency in the continuous decolourization of reactive textile dyes. In the first cycle, the decolourization is mainly due to dyes adsorption on the support. However, when working in successive cycles, the adsorption capacity of the support decreases (saturation) and the enzymatic action increases, indicating the applicability of this biocatalyst for textile wastewater treatment.

Molecular layer deposition of APTES on silicon nanowire biosensors: Surface characterization, stability and pH response

NASA Astrophysics Data System (ADS)

Liang, Yuchen; Huang, Jie; Zang, Pengyuan; Kim, Jiyoung; Hu, Walter

2014-12-01

We report the use of molecular layer deposition (MLD) for depositing 3-aminopropyltriethoxysilane (APTES) on a silicon dioxide surface. The APTES monolayer was characterized using spectroscopic ellipsometry, contact angle goniometry, and atomic force microscopy. Effects of reaction time of repeating pulses and simultaneous feeding of water vapor with APTES were tested. The results indicate that the synergistic effects of water vapor and reaction time are significant for the formation of a stable monolayer. Additionally, increasing the number of repeating pulses improved the APTES surface coverage but led to saturation after 10 pulses. In comparing MLD with solution-phase deposition, the APTES surface coverage and the surface quality were nearly equivalent. The hydrolytic stability of the resulting films was also studied. The results confirmed that the hydrolysis process was necessary for MLD to obtain stable surface chemistry. Furthermore, we compared the pH sensing results of Si nanowire field effect transistors (Si NWFETs) modified by both the MLD and solution methods. The highly repeatable pH sensing results reflected the stability of APTES monolayers. The results also showed an improved pH response of the sensor prepared by MLD compared to the one prepared by the solution treatment, which indicated higher surface coverage of APTES.

Structural and denaturation studies of two mutants of a cold adapted superoxide dismutase point to the importance of electrostatic interactions in protein stability.

PubMed

Merlino, Antonello; Russo Krauss, Irene; Castellano, Immacolata; Ruocco, Maria Rosaria; Capasso, Alessandra; De Vendittis, Emmanuele; Rossi, Bianca; Sica, Filomena

2014-03-01

A peculiar feature of the psychrophilic iron superoxide dismutase from Pseudoalteromonas haloplanktis (PhSOD) is the presence in its amino acid sequence of a reactive cysteine (Cys57). To define the role of this residue, a structural characterization of the effect of two PhSOD mutations, C57S and C57R, was performed. Thermal and denaturant-induced unfolding of wild type and mutant PhSOD followed by circular dichroism and fluorescence studies revealed that C→R substitution alters the thermal stability and the resistance against denaturants of the enzyme, whereas C57S only alters the stability of the protein against urea. The crystallographic data on the C57R mutation suggest an involvement of the Arg side chain in the formation of salt bridges on protein surface. These findings support the hypothesis that the thermal resistance of PhSOD relies on optimization of charge-charge interactions on its surface. Our study contributes to a deeper understanding of the denaturation mechanism of superoxide dismutases, suggesting the presence of a structural dimeric intermediate between the native state and the unfolded state. This hypothesis is supported by the crystalline and solution data on the reduced form of the enzyme. Copyright © 2014 Elsevier B.V. All rights reserved.

Expression of Glutamine Transporter Slc38a3 (SNAT3) During Acidosis is Mediated by a Different Mechanism than Tissue-Specific Expression

PubMed Central

Balkrishna, Sarojini; Bröer, Angelika; Welford, Scott M.; Hatzoglou, Maria; Bröer, Stefan

2015-01-01

Background Despite homeostatic pH regulation, systemic and cellular pH changes take place and strongly influence metabolic processes. Transcription of the glutamine transporter SNAT3 (Slc38a3) for instance is highly up-regulated in the kidney during metabolic acidosis to provide glutamine for ammonia production. Methods Slc38a3 promoter activity and messenger RNA stability were measured in cultured cells in response to different extracellular pH values. Results Up-regulation of SNAT3 mRNA was mediated both by the stabilization of its mRNA and by the up-regulation of gene transcription. Stabilisation of the mRNA involved a pH-response element, while enhanced transcription made use of a second pH-sensitive Sp1 binding site in addition to a constitutive Sp1 binding site. Transcriptional regulation dominated the early response to acidosis, while mRNA stability was more important for chronic adaptation. Tissue-specific expression of SNAT3, by contrast, appeared to be controlled by promoter methylation and histone modifications. Conclusions Regulation of SNAT3 gene expression by extracellular pH involves post-transcriptional and transcriptional mechanisms, the latter being distinct from the mechanisms that control the tissue-specific expression of the gene. PMID:24854847

Controlled Aggregation and Increased Stability of β-Glucuronidase by Cellulose Binding Domain Fusion

PubMed Central

Kim, Moonjung; Kwon, Kil Koang; Fu, Yaoyao; Kim, Haseong; Lee, Hyewon; Lee, Dae-Hee; Jung, Heungchae; Lee, Seung-Goo

2017-01-01

Cellulose-binding domains (CBDs) are protein domains with cellulose-binding activity, and some act as leaders in the localization of cellulosomal scaffoldin proteins to the hydrophobic surface of crystalline cellulose. In this study, we found that a CBD fusion enhanced and improved soluble β-glucuronidase (GusA) enzyme properties through the formation of an artificially oligomeric state. First, a soluble CBD fused to the C-terminus of GusA (GusA-CBD) was obtained and characterized. Interestingly, the soluble GusA-CBD showed maximum activity at higher temperatures (65°C) and more acidic pH values (pH 6.0) than free GusA did (60°C and pH 7.5). Moreover, the GusA-CBD enzyme showed higher thermal and pH stabilities than the free GusA enzyme did. Additionally, GusA-CBD showed higher enzymatic activity in the presence of methanol than free GusA did. Evaluation of the protease accessibility of both enzymes revealed that GusA-CBD retained 100% of its activity after 1 h incubation in 0.5 mg/ml protease K, while free GusA completely lost its activity. Simple fusion of CBD as a single domain may be useful for tunable enzyme states to improve enzyme stability in industrial applications. PMID:28099480

Controlled Aggregation and Increased Stability of β-Glucuronidase by Cellulose Binding Domain Fusion.

PubMed

Yeom, Soo-Jin; Han, Gui Hwan; Kim, Moonjung; Kwon, Kil Koang; Fu, Yaoyao; Kim, Haseong; Lee, Hyewon; Lee, Dae-Hee; Jung, Heungchae; Lee, Seung-Goo

2017-01-01

Cellulose-binding domains (CBDs) are protein domains with cellulose-binding activity, and some act as leaders in the localization of cellulosomal scaffoldin proteins to the hydrophobic surface of crystalline cellulose. In this study, we found that a CBD fusion enhanced and improved soluble β-glucuronidase (GusA) enzyme properties through the formation of an artificially oligomeric state. First, a soluble CBD fused to the C-terminus of GusA (GusA-CBD) was obtained and characterized. Interestingly, the soluble GusA-CBD showed maximum activity at higher temperatures (65°C) and more acidic pH values (pH 6.0) than free GusA did (60°C and pH 7.5). Moreover, the GusA-CBD enzyme showed higher thermal and pH stabilities than the free GusA enzyme did. Additionally, GusA-CBD showed higher enzymatic activity in the presence of methanol than free GusA did. Evaluation of the protease accessibility of both enzymes revealed that GusA-CBD retained 100% of its activity after 1 h incubation in 0.5 mg/ml protease K, while free GusA completely lost its activity. Simple fusion of CBD as a single domain may be useful for tunable enzyme states to improve enzyme stability in industrial applications.

Crystallization and preliminary characterization of a highly thermostable lectin from Trichosanthes dioica and comparison with other Trichosanthes lectins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dharkar, Poorva D.; Anuradha, P.; Gaikwad, Sushama M.

2006-03-01

A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris–HCl pH 8.5 and 50 µl 0.5%(w/v) n-octyl β-d-glucopyranoside as thick needles belonging to hexagonal space group P6{sub 4}. A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris–HCl pH 8.5 and 50 µl 0.5%(w/v) n-octyl β-d-glucopyranoside as thick needles belonging to hexagonal space group P6{sub 4}. Unit-cell parameters were a = b = 167.54, c = 77.42 Å. The crystals diffracted to a Braggmore » spacing of 2.8 Å. Both the structures of abrin-a and T. kirilowii lectin could be used as a model in structure determination using the molecular-replacement method; however, T. kirilowii lectin coordinates gave better values of reliability and correlation parameters. The thermal, chemical and pH stability of this lectin have also been studied. When heated, its haemagglutination activity remained unaffected up to 363 K. Other stability studies show that 4 M guanidinium hydrochloride (Gdn–HCl) initiates unfolding and that the protein is completely unfolded at 6 M Gdn–HCl. Treatment with urea resulted in a total loss of activity at higher concentrations of denaturant with no major structural changes. The protein remained stable over a wide pH range, from pH 6 to pH 12, except for partial unfolding at extremely alkaline pH. The role of disulfide bonds in the protein stability was found to be insignificant. Rayleigh light-scattering studies showed no molecular aggregation in any of the extreme treated conditions. The unusual stability of this lectin resembles that of type II ribosome-inactivating proteins (type II RIPs), which is also supported by structure determination. The structural features observed in a preliminary electron-density map were compared with the other two available Trichosanthes lectin structures.« less

Formaldehyde emission and high-temperature stability of cured urea-formaldehyde resins

Treesearch

Shin-ichiro Tohmura; Chung-Yun Hse; Mitsuo Higuchi

2000-01-01

A test method for measuring formaldehyde from urea-formaldehyde (UF) resins at high temperature was developed and used to assess the influence of the reaction pH on the formaldehyde emission and heat stability of the cured resins. Additionally, solid-state 13C CP/MAS nuclear magnetic resonance (NMR) techniques were used to investigate the...

Vortex sheet modeling with higher order curved panels. Ph.D Thesis Final Technical Report

NASA Technical Reports Server (NTRS)

Nagati, M. G.

1985-01-01

A numerical technique is presented for modeling the vortex sheet with a deformable surface definition, along which a continuous vortex strength distribution in the spanwise direction is applied, so that by repeatedly modifying its shape, its true configuration is approached, in the proximity of its generating wing. Design problems requiring the inclusion of a realistic configuration of the vortex sheet are numerous. Examples discussed include: control effectiveness and stability derivatives, longitudinal stability, lateral stability, canards, propellers and helicopter rotors, and trailing vortex hazards.

Factors affecting fixation of heavy metals in solidified/stabilized matrix: a review.

PubMed

Malviya, Rachana; Chaudhary, Rubina

2010-07-01

In this paper, an effort has been made to understand the factors, which affect fixation of heavy metals in solidified/stabilized matrix. Various aspects related to the solidification/stabilization of different heavy metals (Ar, Ba, Cu, Cr, Pb, Zn, Hg) are reviewed. A comparative study of different binders for the fixation of each metal has also been carried out to suggest the most suitable binder, pretreatment required for the metal. Valence, speciation, pH and other factors are also considered while reviewing metal retention capacity of different matrix.

Factors affecting the stability of viral vaccines.

PubMed

Peetermans, J

1996-01-01

The stability of viral vaccines is determined by the rate of loss of "integrity" of the viral antigen during storage. For live vaccines, such as measles, mumps, rubella, canine distemper, stability is equivalent to the preservation of the infectious titres. For inactivated and subunit vaccines, the preservation of the antigenic structure and the correct steric presentation of the relevant epitopes are the parameters which determine their stability. In general, the following factors may have a negative effect on stability: temperature, pH outside the physiological limits, organic solvents, repeated freezing and thawing, some antiseptics and inactivating agents, and light. However their negative effect is in most cases specific for the individual viruses. Approaches to stabilisation of most vaccines are based on the elimination or neutralisation of the negative factors. Practical examples for the most relevant existing vaccines are described.

Nuclear Magnetic Resonance Structures of GCN4p Are Largely Conserved When Ion Pairs Are Disrupted at Acidic pH but Show a Relaxation of the Coiled Coil Superhelix.

PubMed

Kaplan, Anne R; Brady, Megan R; Maciejewski, Mark W; Kammerer, Richard A; Alexandrescu, Andrei T

2017-03-21

To understand the roles ion pairs play in stabilizing coiled coils, we determined nuclear magnetic resonance structures of GCN4p at three pH values. At pH 6.6, all acidic residues are fully charged; at pH 4.4, they are half-charged, and at pH 1.5, they are protonated and uncharged. The α-helix monomer and coiled coil structures of GCN4p are largely conserved, except for a loosening of the coiled coil quaternary structure with a decrease in pH. Differences going from neutral to acidic pH include (i) an unwinding of the coiled coil superhelix caused by the loss of interchain ion pair contacts, (ii) a small increase in the separation of the monomers in the dimer, (iii) a loosening of the knobs-into-holes packing motifs, and (iv) an increased separation between oppositely charged residues that participate in ion pairs at neutral pH. Chemical shifts (HN, N, C', Cα, and Cβ) of GCN4p display a seven-residue periodicity that is consistent with α-helical structure and is invariant with pH. By contrast, periodicity in hydrogen exchange rates at neutral pH is lost at acidic pH as the exchange mechanism moves into the EX1 regime. On the basis of 1 H- 15 N nuclear Overhauser effect relaxation measurements, the α-helix monomers experience only small increases in picosecond to nanosecond backbone dynamics at acidic pH. By contrast, 13 C rotating frame T 1 relaxation (T 1ρ ) data evince an increase in picosecond to nanosecond side-chain dynamics at lower pH, particularly for residues that stabilize the coiled coil dimerization interface through ion pairs. The results on the structure and dynamics of GCNp4 over a range of pH values help rationalize why a single structure at neutral pH poorly predicts the pH dependence of the unfolding stability of the coiled coil.

Stability studies of anticancer agent bis(4-fluorobenzyl)trisulfide and synthesis of related substances.

PubMed

Bao, Yimei; Mo, Xiaopeng; Xu, Xiaoying; He, Yuyu; Xu, Xiao; An, Haoyun

2008-11-04

Bis(4-fluorobenzyl)trisulfide, fluorapacin, has been extensively developed as a promising new anticancer drug candidate. Its degradation products were identified and verified by the newly synthesized compounds bis(4-fluorobenzyl)disulfide (A) and bis(4-fluorobenzyl)tetrasulfide (B) which were resulted from the disproportionation of fluorapacin under forced conditions. A stability-indicating HPLC method was used for the stability evaluation of active pharmaceutical ingredient (API) fluorapacin and finished pharmaceutical product (FPP) under various conditions. High recovery (99.57%) of API was found after three freeze-thaw cycle processes of fluorapacin FPP. Susceptibility of fluorapacin to oxidative degradation was studied by treating fluorapacin and FPP in 30% hydrogen peroxide aqueous solution, and the result verified the oxidative stability of fluorapacin. However, treatment of this drug candidate under strong light (4500 Lx+/-500 Lx) for 10 days showed substantial effect on the recovery of fluorapacin, especially from fluorapacin FPP. Strong acid (1.0M, HCl) did not affect the recovery of fluorapacin while strong basic condition (1.0M, NaOH) accelerated the disproportionation of fluorapacin to its related substances A and B. The stability of fluorapacin in its aqueous media at a pH range of 2.0-10.0 for up to 6h was further investigated, and 4.0-8.0 was found to be the most stable pH range. Fluorapacin and FPP were exposed to the elevated temperatures of 40 and 60 degrees C for 10 days without obvious impact on their stability. The thermal stability of fluorapacin API and FPP under constant humidity with light protection was also thoroughly investigated under accelerated (40+/-2 degrees C, RH 75+/-5%, 6 months) and long-term (25+/-2 degrees C, RH 60+/-10%, 24 months) conditions. There was no significant change except minor color change of fluorapacin FPP. Therefore, fluorapacin has excellent stability as a potential drug candidate for further clinical development investigation.

pH Shifting alters solubility characteristics and thermal stability of soy protein isolate and its globulin fractions in different pH, salt concentration, and temperature conditions.

PubMed

Jiang, Jiang; Xiong, Youling L; Chen, Jie

2010-07-14

Soy protein isolate (SPI), beta-conglycinin (7S), and glycinin (11S) were subjected to pH-shifting treatments, that is, unfolding at pH 1.5 or 12.0 followed by refolding at pH 7.0, to induce molten globule structures. Treated samples were analyzed for protein solubility, thermal stability, and aggregation in 0, 0.1, and 0.6 M NaCl solutions at pH 2.0-8.0. The pH(12) shifting resulted in drastic increases (up to 2.5-fold) in SPI solubility in the pH 6.0-7.0 range, especially at 0 M NaCl. The pH(1.5) shifting had a generally lesser effect on solubility. 11S exhibited a solubility pattern similar to that of SPI, but the solubility of 7S was unaffected by pH shifting except at 0.6 M NaCl. The pH shifting, notably at pH 12.0, produced soluble, disulfide-linked polymers from 11S and reduced (P < 0.05) its enthalpy but not its temperature of denaturation. Soy proteins structurally altered by pH shifting had a reduced sensitivity to thermal aggregation.

Immobilization of Moniliella spathulata R25L270 Lipase on Ionic, Hydrophobic and Covalent Supports: Functional Properties and Hydrolysis of Sardine Oil.

PubMed

Souza, Lívia T de A; Moreno-Perez, Sonia; Fernández Lorente, Gloria; Cipolatti, Eliane P; de Oliveira, Débora; Resende, Rodrigo R; Pessela, Benevides C

2017-09-25

The oleaginous yeast Moniliella spathulata R25L270 was the first yeast able to grow and produce extracellular lipase using Macaúba ( Acrocomia aculeate ) cake as substrate. The novel lipase was recently identified, and presented promising features for biotechnological applications. The M. spathulata R25L270 lipase efficiently hydrolyzed vegetable and animal oils, and showed selectivity for generating cis -5,8,11,15,17-eicosapentaenoic acid from sardine oil. The enzyme can act in a wide range of temperatures (25-48 °C) and pH (6.5-8.4). The present study deals with the immobilization of M. spathulata R25L270 lipase on hydrophobic, covalent and ionic supports to select the most active biocatalyst capable to obtain omega-3 fatty acids (PUFA) from sardine oil. Nine immobilized agarose derivatives were prepared and biochemically characterized for thermostability, pH stability and catalytic properties (K M and V max ). Ionic supports improved the enzyme-substrate affinity; however, it was not an effective strategy to increase the M. spathulata R25L270 lipase stability against pH and temperature. Covalent support resulted in a biocatalyst with decreased activity, but high thermostability. The enzyme was most stabilized when immobilized on hydrophobic supports, especially Octyl-Sepharose. Compared with the free enzyme, the half-life of the Octyl-Sepharose derivative at 60 °C increased 10-fold, and lipase stability under acidic conditions was achieved. The Octyl-Sepharose derivative was selected to obtain omega-3 fatty acids from sardine oil, and the maximal enzyme selectivity was achieved at pH 5.0.

Influence of protein fold stability on immunogenicity and its implications for vaccine design

PubMed Central

Scheiblhofer, Sandra; Laimer, Josef; Machado, Yoan; Weiss, Richard; Thalhamer, Josef

2017-01-01

ABSTRACT Introduction: In modern vaccinology and immunotherapy, recombinant proteins more and more replace whole organisms to induce protective or curative immune responses. Structural stability of proteins is of crucial importance for efficient presentation of antigenic peptides on MHC, which plays a decisive role for triggering strong immune reactions. Areas covered: In this review, we discuss structural stability as a key factor for modulating the potency of recombinant vaccines and its importance for antigen proteolysis, presentation, and stimulation of B and T cells. Moreover, the impact of fold stability on downstream events determining the differentiation of T cells into effector cells is reviewed. We summarize studies investigating the impact of protein fold stability on the outcome of the immune response and provide an overview on computational methods to estimate the effects of point mutations on protein stability. Expert commentary: Based on this information, the rational design of up-to-date vaccines is discussed. A model for predicting immunogenicity of proteins based on their conformational stability at different pH values is proposed. PMID:28290225

Enzyme stability, thermodynamics and secondary structures of α-amylase as probed by the CD spectroscopy.

PubMed

Kikani, B A; Singh, S P

2015-11-01

An amylase of a thermophilic bacterium, Bacillus sp. TSSC-3 (GenBank Number, EU710557) isolated from the Tulsi Shyam hot spring reservoir (Gujarat, India) was purified to the homogeneity in a single step on phenyl sepharose 6FF. The molecular weight of the enzyme was 25kD, while the temperature and pH optima for the enzyme catalysis were 80°C and 7, respectively. The purified enzyme was highly thermostable with broad pH stability and displayed remarkable resistance against surfactants, chelators, urea, guanidine HCl and various solvents as well. The stability and changes in the secondary structure of the enzyme under various extreme conditions were determined by the circular dichroism (CD) spectroscopy. The stability trends and the changes in the α-helices and β-sheets were analyzed by Mean Residual Ellipticity (MRE) and K2D3. The CD data confirmed the structural stability of the enzyme under various harsh conditions, yet it indicated reduced α-helix content and increased β-sheets upon denaturation. The thermodynamic parameters; deactivation rate constant, half-life, changes in entropy, enthalpy, activation energy and Gibb's free energy indicated that the enzyme-substrate reactions were highly stable. The overall profile of the enzyme: high thermostability, alkalitolerance, calcium independent nature, dextrose equivalent values and resistance against chemical denaturants, solvents and surfactants suggest its commercial applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Studies of obtaining and stability in aqueous medium of new complex compounds of Ti(IV) and Zr(IV) used in ecological leather tanning

NASA Astrophysics Data System (ADS)

Crudu, Marian; Sibiescu, Doina; Rosca, Ioan; Sutiman, Daniel; Vizitiu, Mihaela

2009-01-01

In this paper, the study of obtaining new coordination compounds of Ti(IV) and Zr(IV) using as ligand: D,L-β-iso-butyric acid, is presented. Also, the stability of these compounds in aqueous medium is studied. The studies of obtaining and of stability of the new compounds were accomplished in aqueous solutions using methods characteristic for coordination compounds: conductance and pH measurements. The combination ratios and the stability were determined with methods characteristic for studies in solutions. From experimental data resulted that the combination ratio of central metallic atoms with the ligand derived from D,L-β-iso-butyric acid was 1:2. From experimental data resulted that in strong acid and strong basic mediums, the coordination compounds could not be obtained. The optimal stability of the studied compounds is limited between 3-6, pH - values. This fact is in accordance with the conditions of using these compounds in ecological leather tanning. Of great importance is that these compounds were used with very good results in tanning processes of different types of leather. This fact evidenced that the ecological alternative of tanning is better than non-ecological tanning using chrome compounds. The importance of this paper consists in obtaining new coordination compounds that can be used in ecological leather tanning.

Improving clarity and stability of skim milk powder dispersions by dissociation of casein micelles at pH 11.0 and acidification with citric acid.

PubMed

Pan, Kang; Zhong, Qixin

2013-09-25

Casein micelles in milk cause turbidity and have poor stability at acidic conditions. In this study, skim milk powder dispersions were alkalized to pH 10.0 or 11.0, corresponding to reduced particle mass. In the following acidification with hydrochloric or citric acid, the re-formation of casein particles was observed. The combination of treatment at pH 11.0 and acidification with citric acid resulted in dispersions with the lowest turbidity and smallest particles, which enabled translucent dispersions at pH 5.5-7.0, corresponding to discrete nanoparticles. The concentration of ionic calcium was lower when acidified with citric acid than hydrochloric acid, corresponding to smaller particles with less negative zeta potential. The pH 11.0 treatment followed by acidification with citric acid also resulted in smaller particles than the simple chelating effects (directly implementing sodium citrate). The produced casein nanoparticles with reduced dimensions can be used for beverage and other novel applications.

Comparable stability of Hoogsteen and Watson-Crick base pairs in ionic liquid choline dihydrogen phosphate.

PubMed

Tateishi-Karimata, Hisae; Nakano, Miki; Sugimoto, Naoki

2014-01-08

The instability of Hoogsteen base pairs relative to Watson-Crick base pairs has limited biological applications of triplex-forming oligonucleotides. Hydrated ionic liquids (ILs) provide favourable environments for a wide range of chemical reactions and are known to impact the stabilities of Watson-Crick base pairs. We found that DNA triplex formation was significantly stabilized in hydrated choline dihydrogen phosphate as compared with an aqueous buffer at neutral pH. Interestingly, the stability of Hoogsteen base pairs was found to be comparable with that of Watson-Crick base pairs in the hydrated IL. Molecular dynamics simulations of a DNA triplex in the presence of choline ions revealed that the DNA triplex was stabilized because of the binding of choline ion around the third strand in the grooves. Our finding will facilitate the development of new DNA materials. Our data also indicate that triplex formation may be stabilized inside cells where choline ions and their derivatives are abundant in vivo.

Comparable Stability of Hoogsteen and Watson–Crick Base Pairs in Ionic Liquid Choline Dihydrogen Phosphate

PubMed Central

Tateishi-Karimata, Hisae; Nakano, Miki; Sugimoto, Naoki

2014-01-01

The instability of Hoogsteen base pairs relative to Watson–Crick base pairs has limited biological applications of triplex-forming oligonucleotides. Hydrated ionic liquids (ILs) provide favourable environments for a wide range of chemical reactions and are known to impact the stabilities of Watson–Crick base pairs. We found that DNA triplex formation was significantly stabilized in hydrated choline dihydrogen phosphate as compared with an aqueous buffer at neutral pH. Interestingly, the stability of Hoogsteen base pairs was found to be comparable with that of Watson–Crick base pairs in the hydrated IL. Molecular dynamics simulations of a DNA triplex in the presence of choline ions revealed that the DNA triplex was stabilized because of the binding of choline ion around the third strand in the grooves. Our finding will facilitate the development of new DNA materials. Our data also indicate that triplex formation may be stabilized inside cells where choline ions and their derivatives are abundant in vivo. PMID:24399194

Effect of thermal behavior of β-lactoglobulin on the oxidative stability of menhaden oil-in-water emulsions.

PubMed

Phoon, Pui Yeu; Narsimhan, Ganesan; San Martin-Gonzalez, Maria Fernanda

2013-02-27

This study reports how emulsion oxidative stability was affected by the interfacial structure of β-lactoglobulin due to different heat treatments. Four percent (v/v) menhaden oil-in-water emulsions, stabilized by 1% (w/v) β-lactoglobulin at pH 7, were prepared by homogenization under different thermal conditions. Oxidative stability was monitored by the ferric thiocyanate peroxide value assay. Higher oxidative stability was attained by β-lactoglobulin in the molten globule state than in the native or denatured state. From atomic force microscopy of β-lactoglobulin adsorbed onto highly ordered pyrolytic graphite in buffer, native β-lactoglobulin formed a relatively smooth interfacial layer of 1.2 GPa in Young's modulus, whereas additional aggregates of similar stiffness were found when β-lactoglobulin was preheated to the molten globule state. For denatured β-lactoglobulin, although aggregates were also observed, they were larger and softer (Young's modulus = 0.45 GPa), suggesting increased porosity and thus an offset in the advantage of increased layer coverage on oxidative stability.

Stabilization of Phenylalanine Ammonia Lyase from Rhodotorula glutinis by Encapsulation in Polyethyleneimine-Mediated Biomimetic Silica.

PubMed

Cui, Jiandong; Liang, Longhao; Han, Cong; Lin Liu, Rong

2015-06-01

Phenylalanine ammonia lyase (PAL) from Rhodotorula glutinis was encapsulated within polyethyleneimine-mediated biomimetic silica. The main factors in the preparation of biomimetic silica were optimized by response surface methodology (RSM). Compared to free PAL (about 2 U), the encapsulated PAL retained more than 43 % of their initial activity after 1 h of incubation time at 60 °C, whereas free PAL lost most of activity in the same conditions. It was clearly indicated that the thermal stability of PAL was improved by encapsulation. Moreover, the encapsulated PAL exhibited the excellent stability of the enzyme against denaturants and storage stability, and pH stability was improved by encapsulation. Operational stability of 7 reaction cycles showed that the encapsulated PAL was stable. Nevertheless, the K m value of encapsulated PAL in biomimetic silica was higher than that of the free PAL due to lower total surface area and increased mass transfer resistance.

Accelerated Stability Studies on Dried Extracts of Centella asiatica Through Chemical, HPLC, HPTLC, and Biological Activity Analyses.

PubMed

Kaur, Ishtdeep; Suthar, Nancy; Kaur, Jasmeen; Bansal, Yogita; Bansal, Gulshan

2016-10-01

Regulatory guidelines recommend systematic stability studies on a herbal product to establish its shelf life. In the present study, commercial extracts (Types I and II) and freshly prepared extract (Type III) of Centella asiatica were subjected to accelerated stability testing for 6 months. Control and stability samples were evaluated for organoleptics, pH, moisture, total phenolic content (TPC), asiatic acid, kaempherol, and high-performance thin layer chromatography fingerprints, and for antioxidant and acetylcholinesterase inhibitory activities. Markers and TPC and both the activities of each extract decreased in stability samples with respect to control. These losses were maximum in Type I extract and minimum in Type III extract. Higher stability of Type III extract than others might be attributed to the additional phytoconstituents and/or preservatives in it. Pearson correlation analysis of the results suggested that TPC, asiatic acid, and kaempferol can be taken as chemical markers to assess chemical and therapeutic shelf lives of herbal products containing Centella asiatica. © The Author(s) 2016.

Enhanced stability of superparamagnetic iron oxide nanoparticles in biological media using a pH adjusted-BSA adsorption protocol

NASA Astrophysics Data System (ADS)

Yu, Si-Ming; Laromaine, Anna; Roig, Anna

2014-07-01

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used for biological applications due to their unique properties compared to their bulk counterparts, simplified SPIONs stabilization protocols applicable for a wide spectra of biological media remains a challenging issue. In this work, SPIONs with different surface coatings, tetramethylammonium hydroxide-coated SPIONs (T-SPIONs), and citrate-coated SPIONs (C-SPIONs) were synthesized by a facile, rapid and cost effective microwave-assisted method. C-SPIONs show robust stability in biological media of phosphate buffered saline and Roswell Park Memorial Institute Medium, while destabilize in DMEM. T-SPIONs were found to aggregate rapidly and significantly in all tested media. Then, a modified pH adjusted-BSA adsorption protocol and an addition of excess trisodium citrate dihydrate (Na3Cit) were used to enhance their stability in the media. The BSA adsorption protocol showed great efficiency in stabilizing the dispersed state of both SPIONs in the tested media, while the addition of excess Na3Cit showed limited effect, and it was only applicable for C-SPIONs. The formed BSA layer on SPIONs could be imaged by negative staining TEM, and revealed by Cryo-TEM, FTIR, DLS, and the zeta potential measurements. Results indicated that BSA forms a monolayer of a thickness of about 3 ± 1 nm and BSA interacts with C-SPIONs and T-SPIONs through their coating, rather than by replacing them. This synthetic method and stabilization protocol offer a general methodology to obtain SPIONs with a variety of surfactants, stable in different biological media in few minutes.

Extraction and characterization of oil bodies from soy beans: a natural source of pre-emulsified soybean oil.

PubMed

Iwanaga, Daigo; Gray, David A; Fisk, Ian D; Decker, Eric Andrew; Weiss, Jochen; McClements, David Julian

2007-10-17

Soybeans contain oil bodies that are coated by a layer of oleosin proteins. In nature, this protein coating protects the oil bodies from environmental stresses and may be utilized by food manufacturers for the same purpose. In this study, oil bodies were extracted from soybean using an aqueous extraction method that involved blending, dispersion (pH 8.6), filtration, and centrifugation steps. The influence of NaCl (0-250 mM), thermal processing (30-90 degrees C, 20 min) and pH (2-8) on the properties and stability of the oil bodies was analyzed using zeta-potential, particle size, and creaming stability measurements. The extracted oil bodies were relatively small ( d 32 approximately 250 nm), and their zeta-potential went from around +12 mV to -20 mV as the pH was increased from 2 to 8, with an isoelectric point around pH 4. The oil bodies were stable to aggregation and creaming at low (pH = 2) and high (pH >/= 6) pH values but were unstable at intermediate values (3

Studies on the potent bacterial mutagen, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone: aqueous stability, XAD recovery and analytical determination in drinking water and in chlorinated humic acid solutions.

PubMed

Meier, J R; Knohl, R B; Coleman, W E; Ringhand, H P; Munch, J W; Kaylor, W H; Streicher, R P; Kopfler, F C

1987-12-01

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was detected by gas chromatography/mass spectrometry in drinking water samples from 3 locations in the U.S.A., and also in a chlorinated humic acid solution. MX appears to account for a significant proportion of the mutagenicity of these samples, as measured in the Ames test using strain TA100 without metabolic activation. Studies on recovery of MX from spiked water samples by XAD-2/8 resin adsorption/acetone elution indicated that sample acidification prior to resin adsorption was essential to the effective recovery of MX. The stability of MX in aqueous solution was pH and temperature dependent. At 23 degrees C the order of stability, based on persistence of mutagenic activity was found to be: pH 2 greater than pH 4 greater than pH 8 greater than pH 6. The half-life at pH 8 and 23 degrees C was 4.6 days. One of the degradation products has been tentatively identified as 2-chloro-3-(dichloromethyl)-4-oxo-2-butenoic acid, an open form of MX which appears to be in the "E" configuration. Overall, these results suggest that MX is formed during water chlorination as a result of reaction of chlorine with humic substances, and that a substantial fraction of the MX formed is likely to persist throughout the distribution system.

Experimental and theoretical investigation of the stability of stepwise pH gradients in continuous flow electrophoresis

NASA Technical Reports Server (NTRS)

Kuhn, Reinhard; Wagner, Horst; Mosher, Richard A.; Thormann, Wolfgang

1987-01-01

Isoelectric focusing in the continuous flow mode can be more quickly and economically performed by admitting a stepwise pH gradient composed of simple buffers instead of uniform mixtures of synthetic carrier ampholytes. The time-consuming formation of the pH gradient by the electric field is thereby omitted. The stability of a three-step system with arginine - morpholinoethanesulfonic acid/glycylglycine - aspartic acid is analyzed theoretically by one-dimensional computer simulation as well as experimentally at various flow rates in a continuous flow apparatus. Excellent agreement between experimental and theoretical data was obtained. This metastable configuration was found to be suitable for focusing of proteins under continuous flow conditions. The influence of various combinations of electrolytes and membranes between electrophoresis chamber and electrode compartments is also discussed.

Comparative leaching of six toxic metals from raw and chemically stabilized MSWI fly ash using citric acid.

PubMed

Wang, Huawei; Fan, Xinxiu; Wang, Ya-Nan; Li, Weihua; Sun, Yingjie; Zhan, Meili; Wu, Guizhi

2018-02-15

The leaching behavior of six typical toxic metals (Pb, Zn, Cr, Cd, Cu and Ni) from raw and chemically stabilized (phosphate and chelating agent) municipal solid waste incineration (MSWI) fly ash were investigated using citric acid. Leaching tests indicated that phosphate stabilization can effectively decrease the leaching of Zn, Cd and Cr; whereas chelating agent stabilization shows a strong ability to lower the release of Pb, Cd and Cu, but instead increases the solubility of Zn and Cr at low pH conditions. Sequential extraction results suggested that the leaching of Pb, Zn and Cd in both the stabilized MSWI fly ash samples led to the decrease in Fe/Mn oxide fraction and the increase in exchangeable and carbonate fractions. The leaching of Cr was due to the decrease in exchangeable, carbonate and Fe/Mn oxide fractions in phosphate-stabilized and chelating agent-stabilized MSWI fly ash. The leaching of Cu in both stabilized MSWI fly ash was greatly ascribed to the decrease in Fe/Mn oxide and oxidisable fractions. Moreover, predicted curves by geochemical model indicated that both stabilized MSWI fly ash have the risk of releasing toxic metals under strong acid environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Stability studies of saponins in Bacopa monnieri dried ethanolic extracts.

PubMed

Phrompittayarat, Watoo; Wittaya-areekul, Sakchai; Jetiyanon, Kanchalee; Putalun, Waraporn; Tanaka, Hiroyuki; Ingkaninan, Kornkanok

2008-11-01

Bacopa monnieri (L.) Wettst. (Brahmi) is currently used as a drug and food supplement for memory improvement. However, studies on the physical and chemical stability of the extract components, especially on the lead compound important for pre-formulation, have not yet been reported. In this study, the stabilities of the crude extract and the diluted crude extract were investigated at various temperatures using saponin glycosides, bacopaside I and bacoside A3 as markers for quantitative analysis. The stability testing of bacopaside I and bacoside A3 standard solution was performed at various temperatures and pH values. The quantity of both compounds under all conditions was analyzed using HPLC techniques. The moisture adsorption of the crude extract was determined at 5, 40, 60 and 80 degrees C at 75 % relative humidity using gravimetric methods. The results revealed that the crude extract quickly adsorbed moisture up to 54 % w/w at both 40 and 80 degrees C, while it only slowly adsorbed moisture at 5 degrees C. The amounts of intact bacopaside I and bacoside A3 in the crude extract decreased drastically at 80 degrees C, slowly at 40 and 60 degrees C, and remained unchanged at 5 degrees C during the period of investigation. Moreover, the amount of both compounds in the standard solution dropped sharply at a pH of 1.2 but slowly at pH 6.8 and 9.0, respectively. The pre-formulation data could be further used for improvement of the final product quality.

Dehydration and Stabilization of a Reactive Tertiary Hydroxyl Group in Solid Oral Dosage Forms of BMS-779788.

PubMed

Adams, Monica L; Sharma, Vijayata; Gokhale, Madhushree; Huang, Yande; Stefanski, Kevin; Su, Ching; Hussain, Munir A

2016-04-01

BMS-779788 contains a reactive tertiary hydroxyl attached to a weakly basic imidazole ring. Propensity of the carbinol toward dehydration to yield the corresponding alkene, BMS-779788-ALK, was evaluated. Elevated levels of BMS-779788-ALK were observed in excipient compatibility samples. Stability studies revealed that BMS-779788 degrades to BMS-779788-ALK in capsules and tablets prepared by both dry and wet granulation processes. An acid-catalyzed dehydration mechanism, in which the heterocyclic core contributes resonance stability to the cationic intermediate via charge transfer to the imidazole ring, was proposed. Therefore, neutralization via a buffered (pH 7.0) granulating solution was used to mitigate dehydration. Solution studies revealed degradation of BMS-779788 to BMS-779788-ALK over the pH range of 1-7.5. Reversibility was confirmed by initiating reactions with BMS-779788-ALK over the same pH range. Accordingly, a simple reversible scheme can be used to describe reactions initiated with either BMS-779788 or BMS-779788-ALK. To eliminate potential for charge delocalization across the heterocycle and probe the degradation mechanism, the imidazole ring of BMS-779788 was methylated (BMS-779788-Me). The propensity for acid-catalyzed dehydration was then evaluated. The acid stability of BMS-779788-Me confirmed that the heterocyclic core contributes to reactivity liability of the tertiary hydroxyl. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions: from protein buffer capacity prediction to bioprocess applications.

PubMed

Bahrenburg, Sven; Karow, Anne R; Garidel, Patrick

2015-04-01

Protein therapeutics, including monoclonal antibodies (mAbs), have significant buffering capacity, particularly at concentrations>50 mg/mL. This report addresses pH-related issues critical to adoption of self-buffered monoclonal antibody formulations. We evaluated solution conditions with protein concentrations ranging from 50 to 250 mg/mL. Samples were both buffer-free and conventionally buffered with citrate. Samples were non-isotonic or adjusted for isotonicity with NaCl or trehalose. Studies included accelerated temperature stability tests, shaking stability studies, and pH changes in infusion media as protein concentrate is added. We present averaged buffering slopes of capacity that can be applied to any mAb and present a general method for calculating buffering capacity of buffer-free, highly concentrated antibody liquid formulations. In temperature stability tests, neither buffer-free nor conventionally buffered solution conditions showed significant pH changes. Conventionally buffered solutions showed significantly higher opalescence than buffer-free ones. In general, buffer-free solution conditions showed less aggregation than conventionally buffered solutions. Shaking stability tests showed no differences between buffer-free and conventionally buffered solutions. "In-use" preparation experiments showed that pH in infusion bag medium can rapidly approximate that of self-buffered protein concentrate as concentrate is added. In summary, the buffer capacity of proteins can be predicted and buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Purification and biochemical characterization of a thermostable and acid-stable alpha-amylase from Bacillus licheniformis B4-423.

PubMed

Wu, Xiangrong; Wang, Yuxia; Tong, Bending; Chen, Xianghua; Chen, Jianhua

2018-04-01

Novel thermostable amylase need to be continuously explored with the improvement of industrial requirements. A new acidophilic and thermostable amylase producing bacterium isolated from spring was identified as Bacillus strain on the basis of 16S rDNA. The amylase was purified by ammonium sulphate precipitation, gel chromatography and anion exchange chromatography. SDS-PAGE revealed that the enzyme was monomeric with a molecular weight of 58 kDa. The amylase exhibited optimal activity at pH 5.0 and temperature 100 °C. Then the enzyme showed high stability in pH ranges 4.0-10.0 and more than 90% of maximal activity was found from 20 °C to 80 °C. Apart from good stability toward SDS and non-ionic detergent, the purified enzyme exhibited high compatibility with some inhibitors such as urea and EDTA. The results demonstrated the stability of the enzyme in different organic solvents. Moreover, we determined the amylase gene, compared the structure with α-amylase BAA and BLA and found some thermostability determinants in our enzyme. Overall, presenting various properties were including high thermostability, Ca 2+ -independency, broad temperature and pH profiles, organic-solvent tolerance as well as excellent stability with detergents. Such characteristics have not been reported for this type of enzyme, and the α-amylase will be a suitable candidate in industrial fields. Copyright © 2017 Elsevier B.V. All rights reserved.

Collaborative study for the calibration of the Ph. Eur. prekallikrein activator in albumin BRP batches 4, 5 and 6.

PubMed

Lackner, F; Daas, A; Terao, E

2015-01-01

An international collaborative study was organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM, Council of Europe) to calibrate replacement batches for the current European Pharmacopoeia (Ph. Eur.) prekallikrein activator (PKA) in albumin biological reference preparation (BRP), whose stocks were dwindling. The study was run in the framework of the Biological Standardisation Programme (BSP) of the Council of Europe and the European Union (EU) Commission. Twenty three laboratories from official medicines control authorities and manufacturers in Europe and outside Europe took part in the study. Three candidate replacement batches were produced from the same material as the one used for the World Health Organization (WHO) 2(nd) International Standard (IS) for PKA in albumin (02/168) and the Ph. Eur. PKA in albumin BRP batches 1, 2 and 3. Participants were requested to evaluate the candidate batches against the current WHO IS using their routine assay method. The Ph. Eur. PKA in albumin BRP batch 3 (BRP3) was also included in the test panel to ensure the continuity of the consecutive BRP batches. The study confirmed the stability of the PKA content of the current BRP3. The candidate batches were found to be comparable. Previous data on the starting material support its high stability. Thermal stress study on the candidate batches confirmed the stability of their PKA activity. The Commission of the Ph. Eur. officially adopted in November 2013 the 3 candidate batches as Ph. Eur. PKA in albumin BRP batches 4, 5 and 6 with an assigned content of 38 IU/vial. The activity of the 3 new batches of Ph. Eur. PKA in albumin BRP will be regularly monitored.

Heat stability of cured urea-formaldehyde resins by measuring formaldehyde emission

Treesearch

Shin-ichiro Tohmura; Chung-Yun Hse; Mitsuo Higuchi

1999-01-01

A test method for measuring formaldehyde from urea-formaldehyde (UF) resins at high tempera­tures was developed and used to assess the influence of the reaction pH at synthesis on the formaldehyde emission during cure and heat stability of the cured resins without water. Additionally, 13C-CP/MAS solid-state nuclear magnetic resonance (NMR)...

Properties of ribulose diphosphate carboxylase immobilized on porous glass

NASA Technical Reports Server (NTRS)

Shapira, J.; Hanson, C. L.; Lyding, J. M.; Reilly, P. J.

1974-01-01

Ribulose-1,5-diphosphate carboxylase from spinach has been bound to arylamine porous glass with a diazo linkage and to alklamine porous glass with glutaraldehyde. Stability at elevated temperatures and responses to changes of pH and ribulose-1,5-diphosphate, Mg(2+), and dithiothreitol concentrations were not significantly different from the soluble enzyme, though stability at 4 C was somewhat improved.

Stabilization of model beverage cloud emulsions using protein-polysaccharide electrostatic complexes formed at the oil-water interface.

PubMed

Harnsilawat, Thepkunya; Pongsawatmanit, Rungnaphar; McClements, David J

2006-07-26

The potential of utilizing interfacial complexes, formed through the electrostatic interactions of proteins and polysaccharides at oil-water interfaces, to stabilize model beverage cloud emulsions has been examined. These interfacial complexes were formed by mixing charged polysaccharides with oil-in-water emulsions containing oppositely charged protein-coated oil droplets. Model beverage emulsions were prepared that consisted of 0.1 wt % corn oil droplets coated by beta-lactoglobulin (beta-Lg), beta-Lg/alginate, beta-Lg/iota-carrageenan, or beta-Lg/gum arabic interfacial layers (pH 3 or 4). Stable emulsions were formed when the polysaccharide concentration was sufficient to saturate the protein-coated droplets. The emulsions were subjected to variations in pH (from 3 to 7), ionic strength (from 0 to 250 mM NaCl), and thermal processing (from 30 or 90 degrees C), and the influence on their stability was determined. The emulsions containing alginate and carrageenan had the best stability to ionic strength and thermal processing. This study shows that the controlled formation of protein-polysaccharide complexes at droplet surfaces may be used to produce stable beverage emulsions, which may have important implications for industrial applications.

Effects of heat, pH, antioxidant, agitation and light on betacyanin stability using red-fleshed dragon fruit (Hylocereus polyrhizus) juice and concentrate as models.

PubMed

Wong, Yen-Ming; Siow, Lee-Fong

2015-05-01

Red-fleshed dragon fruit (Hylocereus polyrhizus) is rich in antioxidants. The aim of this study was to determine the effects of heat pasteurization, pH adjustment, ascorbic acid addition as well as storage under agitation and light or dark condition on betacyanin content in red-fleshed dragon fruit (Hylocereus polyrhizus) juice and concentrate. The concentrate was produced by concentrating clarified red-fleshed dragon fruit juice in a rotary evaporator at 40 °C. UV-Visible spectrophotometer was used for analyzing betacyanin content. Addition of 0.25 % ascorbic acid, pH 4.0, and pasteurization at 65 °C for 30 min were selected as the best processing conditions to retain betacyanin content in red-fleshed dragon fruit juice. Storage at the agitation speed of 220 rpm showed that the concentrated samples had higher betacyanin stability compared to juice, while both juice and concentrate had almost similar betacyanin stability when tested for storage in the presence of light. In summary, ascorbic acid stabilized betacyanin in both juice and concentrate at agitated or non-agitated conditions. In contrast, light degraded betacyanin in both juice and concentrate models.

Liquid permeation and chemical stability of anodic alumina membranes

PubMed Central

Buldakov, Dmitrii A; Tishkin, Alexey A; Lukashin, Alexey V; Eliseev, Andrei A

2017-01-01

A study on the chemical stability of anodic alumina membranes and their performance in long-term water and organic solvent permeation experiments is reported. Anodic alumina possesses high stability for both protonic and aprotonic organic solvents. However, serious degradation of the membrane occurs in pure water, leading to a drastic decrease of permeance (over 20% of the initial value after the passing of 0.250 m3/m2 of pure water). The drying of the membrane induces further permeance drop-off. The rate of membrane degradation strongly depends on the pH of the penetrant solution and increases in basic media. According to 27Al NMR and thermogravimetry results, the degradation of the membranes is associated with the dissolution of water-soluble [Al13O4(OH)24(H2O)12]7+ polyhydroxocomplexes and their further redeposition in the form of [Al(OH)4]−, resulting in channels blocking. This process intensifies in basic pH due to the high positive charge of the anodic alumina surface. An approach for improving anodic aluminum oxide stability towards dissolution in water by carbon CVD coating of the membrane walls is suggested. PMID:28382245

Cold denaturation and 2H2O stabilization of a staphylococcal nuclease mutant.

PubMed Central

Antonino, L C; Kautz, R A; Nakano, T; Fox, R O; Fink, A L

1991-01-01

Cold denaturation is now recognized as a general property of proteins but has been observed only under destabilizing conditions, such as moderate denaturant concentration or low pH. By destabilizing the protein using site-directed mutagenesis, we have observed cold denaturation at pH 7.0 in the absence of denaturants in a mutant of staphylococcal nuclease, which we call NCA S28G for a hybrid protein between staphylococcal nuclease and concanavalin A in which there is the point mutation Ser-28----Gly. The temperature of maximum stability (tmax) as determined by circular dichroism (CD) was 18.1 degrees C, and the midpoints of the thermal unfolding transitions (tm) were 0.6 degrees C and 30.0 degrees C. These values may be compared with the tm of 52.5 degrees C for wild-type staphylococcal nuclease, for which no cold denaturation was observed under these conditions. When the stability of the mutant was examined in 2H2O by NMR, CD, or fluorescence, a substantial increase in the amount of folded protein at the tmax was noted as well as a decrease in tmax, reflecting increased stability. PMID:1652762

Low Molecular Weight Chitosan–Insulin Polyelectrolyte Complex: Characterization and Stability Studies

PubMed Central

Al-Kurdi, Zakieh I.; Chowdhry, Babur Z.; Leharne, Stephen A.; Al Omari, Mahmoud M. H.; Badwan, Adnan A.

2015-01-01

The aim of the work reported herein was to investigate the effect of various low molecular weight chitosans (LMWCs) on the stability of insulin using USP HPLC methods. Insulin was found to be stable in a polyelectrolyte complex (PEC) consisting of insulin and LMWC in the presence of a Tris-buffer at pH 6.5. In the presence of LMWC, the stability of insulin increased with decreasing molecular weight of LMWC; 13 kDa LMWC was the most efficient molecular weight for enhancing the physical and chemical stability of insulin. Solubilization of insulin-LMWC polyelectrolyte complex (I-LMWC PEC) in a reverse micelle (RM) system, administered to diabetic rats, results in an oral delivery system for insulin with acceptable bioactivity. PMID:25830681

Effects of protein phosphorylation on color stability of ground meat.

PubMed

Li, Meng; Li, Xin; Xin, Jianzeng; Li, Zheng; Li, Guixia; Zhang, Yan; Du, Manting; Shen, Qingwu W; Zhang, Dequan

2017-03-15

The influence of protein phosphorylation on meat color stability was investigated in this study. Phosphatase and protein kinase inhibitors were added to minced ovine Longissimus thoracis et lumborum (LTL) muscle to manipulate the global phosphorylation of sarcoplasmic proteins. The data obtained show that the rate and extent of pH decline, along with lactate accumulation in postmortem muscle, were related to protein phosphorylation. Analysis of meat color and the relative content of myoglobin redox forms revealed that meat color stability was inversely related to the phosphorylation of sarcoplasmic proteins. Thus, this study suggests that protein phosphorylation may be involved in meat color development by regulating glycolysis and the redox stability of myoglobin. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stability of gabapentin in extemporaneously compounded oral suspensions.

PubMed

Friciu, Mihaela; Roullin, V Gaëlle; Leclair, Grégoire

2017-01-01

This study reports the stability of extemporaneously prepared gabapentin oral suspensions prepared at 100 mg/mL from bulk drug and capsules in either Oral Mix or Oral Mix SF suspending vehicles. Suspensions were packaged in amber plastic bottles and amber plastic syringes at 25°C / 60%RH for up to 90 days. Throughout the study period, the following tests were performed to evaluate the stability of the preparations: organoleptic inspection to detect homogeneity, color or odor changes; pH measurements; and gabapentin assay using a stability-indicating HPLC-UV method. As crystallization was observed at 5°C, storage at this temperature condition is not recommended. All preparations stored at 25°C / 60%RH remained stable for the whole study duration of 90 days.

Foaming and emulsifying properties of porcine red cell protein concentrate.

PubMed

Salvador, P; Saguer, E; Parés, D; Carretero, C; Toldrà, M

2010-08-01

This work focuses on studying the effects of pH (7.0 and 4.5) and protein concentration on the foaming and emulsifying properties of fresh (F) and spray-dried (SD) porcine red cell protein (RCP) concentrates in order to evaluate the proper use of this blood protein as a functional food ingredient. Also, protein solubility is measured through the pH range from 3.0 to 8.0. In each case, all concentrates show a high solubility, although this is significantly affected by pH. Spray drying slightly reduces the solubility at mild acid and neutral conditions. The foaming capacity is found to be dependent on pH as well as on the drying treatment. SD-RCP concentrates show better foaming capacity than F-RCP. The minimum protein concentration required to attain the highest foaming capacity is found under acid pH for the spray-dried concentrates. Although F-RCP shows low foam stability at acid and neutral pH, spray drying and protein content enhance the stability of foams. Emulsifying properties show dependence on pH as well as on protein content. Furthermore, spray drying affects the emulsifying properties but in different ways, depending on pH and protein concentration.

Stability of Beriplast P fibrin sealant: storage and reconstitution.

PubMed

Eberhard, Ulrich; Broder, Martin; Witzke, Günther

2006-04-26

This study was performed to investigate the stability of Beriplast P fibrin sealant (FS) across a range of storage conditions, both pre- and post-reconstitution. Storage stability of the FS was evaluated during long-term refrigeration (24 months) with or without interim storage at elevated temperatures (40 degrees C for 1 week and 25 degrees C for 1 and 3 months). Stability of individual FS components was assessed by measuring: fibrinogen content, Factor XIII activity (FXIII), thrombin activity and aprotinin potency. The package integrity of each component was also checked (sterility testing, moisture content and pH). Storage stability was also evaluated by testing the reconstituted product for adhesion (tearing force testing after mixing the solutions) and sterility. Reconstitution stability was evaluated following 3-months' storage, for up to 50 h post-reconstitution using the same tests as for the storage stability investigations. Pre-defined specifications were met for fibrinogen content, Factor XIII activity, and thrombin activity, demonstrating storage stability. Package integrity and the functionality and sterility of the reconstituted product were confirmed throughout. Reconstitution stability was demonstrated for up to 50 h following reconstitution, in terms of both tearing force and sterility tests. In conclusion, the storage stability of Beriplast P was demonstrated over a range of 24-month storage schedules including interim exposure to elevated temperature, and the reconstituted product was stable for up to 50 h.

Process for preparing a stabilized coal-water slurry

DOEpatents

Givens, E.N.; Kang, D.

1987-06-23

A process is described for preparing a stabilized coal particle suspension which includes the steps of providing an aqueous media substantially free of coal oxidizing constituents, reducing, in a nonoxidizing atmosphere, the particle size of the coal to be suspended to a size sufficiently small to permit suspension thereof in the aqueous media and admixing the coal of reduced particle size with the aqueous media to release into the aqueous media coal stabilizing constituents indigenous to and carried by the reduced coal particles in order to form a stabilized coal particle suspension. The coal stabilizing constituents are effective in a nonoxidizing atmosphere to maintain the coal particle suspension at essentially a neutral or alkaline pH. The coal is ground in a nonoxidizing atmosphere such as an inert gaseous atmosphere to reduce the coal to a sufficient particle size and is admixed with an aqueous media that has been purged of oxygen and acid-forming gases. 2 figs.

Process for preparing a stabilized coal-water slurry

DOEpatents

Givens, Edwin N.; Kang, Doohee

1987-01-01

A process for preparing a stabilized coal particle suspension which includes the steps of providing an aqueous media substantially free of coal oxidizing constituents, reducing, in a nonoxidizing atmosphere, the particle size of the coal to be suspended to a size sufficiently small to permit suspension thereof in the aqueous media and admixing the coal of reduced particle size with the aqueous media to release into the aqueous media coal stabilizing constituents indigenous to and carried by the reduced coal particles in order to form a stabilized coal particle suspension. The coal stabilizing constituents are effective in a nonoxidizing atmosphere to maintain the coal particle suspension at essentially a neutral or alkaline pH. The coal is ground in a nonoxidizing atmosphere such as an inert gaseous atmosphere to reduce the coal to a sufficient particle size and is admixed with an aqueous media that has been purged of oxygen and acid-forming gases.

Role of Buffers in Protein Formulations.

PubMed

Zbacnik, Teddy J; Holcomb, Ryan E; Katayama, Derrick S; Murphy, Brian M; Payne, Robert W; Coccaro, Richard C; Evans, Gabriel J; Matsuura, James E; Henry, Charles S; Manning, Mark Cornell

2017-03-01

Buffers comprise an integral component of protein formulations. Not only do they function to regulate shifts in pH, they also can stabilize proteins by a variety of mechanisms. The ability of buffers to stabilize therapeutic proteins whether in liquid formulations, frozen solutions, or the solid state is highlighted in this review. Addition of buffers can result in increased conformational stability of proteins, whether by ligand binding or by an excluded solute mechanism. In addition, they can alter the colloidal stability of proteins and modulate interfacial damage. Buffers can also lead to destabilization of proteins, and the stability of buffers themselves is presented. Furthermore, the potential safety and toxicity issues of buffers are discussed, with a special emphasis on the influence of buffers on the perceived pain upon injection. Finally, the interaction of buffers with other excipients is examined. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Effect of pH on Structural Changes in Perch Hemoglobin that Can Alter Redox Stability and Heme Affinity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richards, Mark P.; Aranda, IV, Roman; He, Cai

2010-01-07

pH can be manipulated to alter the oxidative stability of fish-based foods during storage. X-ray diffraction was used to investigate the ability of reduced pH to cause structural changes in fish hemoglobins that lead to enhanced oxidative degradation. Decreasing pH from 8.0 to 6.3 and 5.7 created a large channel for solvent entry into the heme crevice of perch hemoglobin beta chains. The proton-induced opening of this channel occurred between site CD3 and the heme-6-propionate. Solvent entry into the heme crevice can enhance metHb formation and hemin loss, processes that accelerate lipid oxidation. Reduced pH also decreased the distance betweenmore » Ile at E11 in one of the alpha chains and the ligand above the heme iron atom. This sterically displaces O{sub 2} and protonated O{sub 2} which increases metHb formation. These studies demonstrate that pH reduction causes structural changes in perch hemoglobin which increase oxidative degradation of the heme pigment.« less

Rational Development of Neutral Aqueous Electrolytes for Zinc–Air Batteries

PubMed Central

Clark, Simon; Latz, Arnulf

2017-01-01

Abstract Neutral aqueous electrolytes have been shown to extend both the calendar life and cycling stability of secondary zinc–air batteries (ZABs). Despite this promise, there are currently no modeling studies investigating the performance of neutral ZABs. Traditional continuum models are numerically insufficient to simulate the dynamic behavior of these complex systems because of the rapid, orders‐of‐magnitude concentration shifts that occur. In this work, we present a novel framework for modeling the cell‐level performance of pH‐buffered aqueous electrolytes. We apply our model to conduct the first continuum‐scale simulation of secondary ZABs using aqueous ZnCl2–NH4Cl as electrolyte. We first use our model to interpret the results of two recent experimental studies of neutral ZABs, showing that the stability of the pH value is a significant factor in cell performance. We then optimize the composition of the electrolyte and the design of the cell considering factors including pH stability, final discharge product, and overall energy density. Our simulations predict that the effectiveness of the pH buffer is limited by slow mass transport and that chlorine‐containing solids may precipitate in addition to ZnO. PMID:28898553

Improvements in SiC{sub w}/Al{sub 2}O{sub 3} composites through colloidally stabilized suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crimp, M.J.; Oppermann, D.A.; Zhang, M.

1994-12-31

Through manipulation of colloidal parameters, suspensions of SiC(whisker)/Al{sub 2}O{sub 3} were prepared, at 5, 10 and 20 vol% SiC whisker, using processing conditions established in Stable Suspension{copyright}. Utilizing Hogg, Healy and Furstenau`s modifications to DLVO theory, this program predicts stability conditions for composite suspensions. Variations in the suspension pH induce changes in the attractive/repulsive interactions between components. This type of interaction in turn influences the packing and green density. Composite suspensions were prepared, freeze dried, then cold consolidated. The distribution of the SiC whiskers within the Al{sub 2}O{sub 3} matrix was determined from SEM micrographs and the composite green densitymore » correlated to the extent of homo- versus heterostability within the composite suspension. The green density of the pure Al{sub 2}O{sub 3} and the 5 vol% SiC whisker additions was the highest at the pH of maximum stability for each interaction. In contrast, at whisker additions of 10 and 20 vol%, the green density is the highest at a pH of low heterostability.« less

Stability of α-tocotrienol and α-tocopherol in salami-type sausages and curing brine depending on nitrite and pH.

PubMed

Gerling, Eva-Maria; Ternes, Waldemar

2014-12-01

We studied the stability of the valuable vitamer nutrients α-tocotrienol and α-tocopherol and options for their protection in salami-type sausages (blended with α-tocotrienol-rich barley oil) and curing brine. Four different sausage formulations were produced containing nitrite curing salt; nitrite curing salt and ascorbic acid (300mg/kg); nitrite curing salt and carnosic acid (45mg/kg); or sodium chloride. Initial vitamer contents (100mg/kg) did not decrease significantly during ripening and decreased only slightly during storage. Ascorbic acid and carnosic acid were found to be effective in preserving the vitamers in fresh sausages. Freeze-drying of sausages resulted in a significant loss of vitamers (97%), particularly after 14-day storage at room temperature, even in the presence of shielding gases. The vitamer content in the curing brine decreased with decreasing pH in the presence of nitrite. A nitrite concentration of 136mg/L at pH4 resulted in significant loss (90%) of the vitamers. Sufficient stability of the vitamers in salami-type sausage and curing brine can be achieved by processing, formulation, and storage conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Studies of pilocarpine:carbomer intermolecular interactions.

PubMed

Zoppi, Ariana; Linck, Yamila Garro; Monti, Gustavo A; Genovese, Diego B; Jimenez Kairuz, Alvaro F; Manzo, Rubén H; Longhi, Marcela R

2012-05-10

The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were investigated. The effects of the chemical interactions on the chemical stability of the drug also were evaluated. The binary system was characterized by nuclear magnetic resonance techniques, Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction, scanning electron microscopy (SEM) and thermal analysis. The experiments showed that the complex, prepared by freeze-drying, is a solid amorphous form different from its precursors, thereby offering an interesting alternative for the preparation of extended release matrices. The solution stability of PIL was studied at pH 7 and 8, at 70 °C. The PIL solution stability was evaluated alone and in the presence of CBR. Results indicated that the drug in the presence of the polymer is 3.3 and 3.5 times more stable, at pH 7 and pH 8, respectively, than the drug without CBR. The activation energy and the frequency factor, according to Arrhenius plot, were estimated to be 13.9 ± 0.4 and 14.8 ± 0.5 kcalmol(-1), and 6.1 ± 0.3 and 7.6 ± 0.3, with and without the polymer, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Selection for increased muscling in Angus cattle did not increase the glycolytic potential or negatively impact pH decline, retail colour stability or mineral content.

PubMed

McGilchrist, P; Greenwood, P L; Pethick, D W; Gardner, G E

2016-04-01

This study determined the impact of selection for greater muscling in Angus cattle on myofibre characteristics, muscle enzymatics, retail colour stability, pH decline and mineral content of the semimembranosus (SM), semitendinosus (ST) and longissimus thoracis (LT). Muscle from 10 low muscled (low) and 11 high muscled (high) steers were analysed. The high steers had myofibres 22% and 24% larger in cross-sectional area in the SM and ST (P<0.05), and 8.6% less type IIX myofibres in the LT than the low steers (P<0.05). The highs had 4.9% lower lactate dehydrogenase activity, 10.2% and 12.3% higher citrate synthase and isocitrate dehydrogenase activity than lows (P<0.05). The highs had 27% more iron in the LT (P<0.05). The results indicate that the oxidative capacity of muscle can be maintained in more muscular cattle with no detrimental effects to mineral content, pH decline or retail colour stability. Myofibre hypertrophy is one mechanism leading to greater muscle mass of these high muscled cattle. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrochemical behavior and pH stability of artificial salivas for corrosion tests.

PubMed

Queiroz, Gláucia Maria Oliveira de; Silva, Leandro Freitas; Ferreira, José Tarcísio Lima; Gomes, José Antônio da Cunha P; Sathler, Lúcio

2007-01-01

It is assumed that the compositions of artificial salivas are similar to that of human saliva. However, the use of solutions with different compositions in in vitro corrosion studies can lead dissimilar electrolytes to exhibit dissimilar corrosivity and electrochemical stability. This study evaluated four artificial salivas as regards pH stability with time, redox potentials and the polarization response of an inert platinum electrode. The tested solutions were: SAGF medium, Mondelli artificial saliva, UFRJ artificial saliva (prepared at the School of Pharmacy, Federal University of Rio de Janeiro, RJ, Brazil) and USP-RP artificial saliva (prepared at the School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, SP, Brazil). It was observed that pH variations were less than 1 unit during a 50-hour test. The SAGF medium, and the UFRJ and USP-RP solutions exhibited more oxidizing characteristics, whereas the Mondelli solution presented reducing properties. Anodic polarization revealed oxidation of the evaluated electrolytes at potentials below +600 mV SCE. It was observed that the UFRJ and USP-RP solutions presented more intense oxidation and reduction processes as compared to the Mondelli and SAGF solutions.

Interaction of Triapine and related thiosemicarbazones with iron(III)/(II) and gallium(III): a comparative solution equilibrium study†

PubMed Central

Enyedy, Éva A.; Primik, Michael F.; Kowol, Christian R.; Arion, Vladimir B.; Kiss, Tamás; Keppler, Bernhard K.

2012-01-01

Stoichiometry and stability of GaIII, FeIII, FeII complexes of Triapine and five related α-N heterocyclic thiosemicarbazones with potential antitumor activity have been determined by pH-potentiometry, UV-vis spectrophotometry, 1H NMR spectroscopy, and spectrofluorimetry in aqueous solution (with 30% DMSO), together with the characterization of the proton dissociation processes. Additionally, the redox properties of the iron complexes were studied by cyclic voltammetry at various pH values. Formation of high stability bis-ligand complexes was found in all cases, which are predominant at physiological pH with FeIII/FeII, whilst only at the acidic pH range with GaIII. The results show that among the thiosemicarbazones with various substituents the N-terminal dimethylation does not exert a measurable effect on the redox potential, but has the highest impact on the stability of the complexes as well as the cytotoxicity, especially in the absence of a pyridine-NH2 group in the molecule. In addition the fluorescence properties of the ligands in aqueous solution and their changes caused by GaIII were studied. PMID:21523301

Acacia gum as modifier of thermal stability, solubility and emulsifying properties of α-lactalbumin.

PubMed

de Oliveira, Fabíola Cristina; Dos Reis Coimbra, Jane Sélia; de Oliveira, Eduardo Basílio; Rodrigues, Marina Quadrio Raposo Branco; Sabioni, Rachel Campos; de Souza, Bartolomeu Warlene Silva; Santos, Igor José Boggione

2015-03-30

Protein-polysaccharide conjugates often display improved techno-functional properties when compared to their individual involved biomolecules. α-Lactalbumin:acacia gum (α-la:AG) conjugates were prepared via Maillard reaction by the dry-heating method. Conjugate formation was confirmed using results of absorbance, o-phthalaldehyde test, sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography. Techno-functional properties (emulsifying characteristics, solubility, and thermal stability) were evaluated for α-la, α-la/AG mixtures and α-la:AG conjugates. Conjugate thermal stability was improved compared to pure α-la treated at the same conditions of conjugate formation. Response surface methodology was used to establish models to predict solubility and emulsifying activity as functions of the salt concentration, pH and reaction time. α-la:AG conjugate solubility is affected in a complex manner by the three factors analyzed. Emulsifying activity index (EAI) of α-la is significantly affected by pH, while the α-la:AG EAI is affected by the three analyzed factors. Both solubility and EAI are maximized with pH 8.0, NaCl concentration of 0.3 mol L(-1) and two days of Maillard reaction. Copyright © 2014 Elsevier Ltd. All rights reserved.

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing.

PubMed

Yang, Qingbo; Wang, Hanzheng; Lan, Xinwei; Cheng, Baokai; Chen, Sisi; Shi, Honglan; Xiao, Hai; Ma, Yinfa

2015-02-01

pH sensing at the single-cell level without negatively affecting living cells is very important but still a remaining issue in the biomedical studies. A 70 μm reflection-mode fiber-optic micro-pH sensor was designed and fabricated by dip-coating thin layer of organically modified aerogel onto a tapered spherical probe head. A pH sensitive fluorescent dye 2', 7'-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF) was employed and covalently bonded within the aerogel networks. By tuning the alkoxide mixing ratio and adjusting hexamethyldisilazane (HMDS) priming procedure, the sensor can be optimized to have high stability and pH sensing ability. The in vitro real-time sensing capability was then demonstrated in a simple spectroscopic way, and showed linear measurement responses with a pH resolution up to an average of 0.049 pH unit within a narrow, but biological meaningful pH range of 6.12-7.81. Its novel characterizations of high spatial resolution, reflection mode operation, fast response and high stability, great linear response within biological meaningful pH range and high pH resolutions, make this novel pH probe a very cost-effective tool for chemical/biological sensing, especially within the single cell level research field.

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing

PubMed Central

Yang, Qingbo; Wang, Hanzheng; Lan, Xinwei; Cheng, Baokai; Chen, Sisi; Shi, Honglan; Xiao, Hai; Ma, Yinfa

2014-01-01

pH sensing at the single-cell level without negatively affecting living cells is very important but still a remaining issue in the biomedical studies. A 70 μm reflection-mode fiber-optic micro-pH sensor was designed and fabricated by dip-coating thin layer of organically modified aerogel onto a tapered spherical probe head. A pH sensitive fluorescent dye 2′, 7′-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF) was employed and covalently bonded within the aerogel networks. By tuning the alkoxide mixing ratio and adjusting hexamethyldisilazane (HMDS) priming procedure, the sensor can be optimized to have high stability and pH sensing ability. The in vitro real-time sensing capability was then demonstrated in a simple spectroscopic way, and showed linear measurement responses with a pH resolution up to an average of 0.049 pH unit within a narrow, but biological meaningful pH range of 6.12–7.81. Its novel characterizations of high spatial resolution, reflection mode operation, fast response and high stability, great linear response within biological meaningful pH range and high pH resolutions, make this novel pH probe a very cost-effective tool for chemical/biological sensing, especially within the single cell level research field. PMID:25530670

Stability of Allopurinol, Amitriptyline Hydrochloride, Carbamazepine, Domperidone, Isoniazid, Ketoconazole, Lisinopril, Naproxen, Paracetamol (Acetaminophen), and Sertraline Hydrochloride in SyrSpend SF PH4 Oral Suspensions.

PubMed

Polonini, Hudson C; Loures, Sharlene; de Araujo, Edson Peter; Brandão, Marcos Antônio F; Ferreira, Anderson O

2016-01-01

Oral liquids are safe alternatives to solid dosage forms, notably for elderly and pediatric patients that present dysphagia. The use of ready-to-use suspending vehicles such as SyrSpend SF PH4 is a suitable resource for pharmacists as they constitute a safe and timesaving option that has been studied often. The objective of this study was to evaluate the stability of 10 commonly used active pharmaceutical ingredients (allopurinol 20 mg/mL; amitriptyline hydrochloride 10 mg/mL; carbamazepine 25 mg/mL; domperidone 5 mg/mL; isoniazid 10 mg/mL; ketoconazole 20 mg/mL; lisinopril 1 mg/mL; naproxen 25 mg/mL; paracetamol [acetaminophen] 50 mg/mL; and sertraline hydrochloride 10 mg/mL) compounded in oral suspensions using SyrSpend SF PH4 as the vehicle throughout the study period and stored both at controlled refrigerated (2°C to 8°C) and room temperature (20°C to 25°C). Stability was assessed by means of measuring the percent recovery at varying time points throughout a 90-day period. The quantification of the active pharmaceutical ingredients was performed by high-performance liquid chromatography through a stability-indicating method. Methods were adequately validated. Forced-degradation studies showed that at least one parameter influenced the stability of the active pharmaceutical ingredients. All suspensions were assayed and showed active pharmaceutical ingredient contents between 90% and 110% during the 90-day study period. Although the forced-degradation experiments led to visible fluctuations in the chromatographic responses, the final preparations were stable in the storage conditions. The beyond-use dates of the preparations were found to be at least 90 days for all suspensions, both for controlled refrigerated temperature and room temperature. This confirms that SyrSpend SF PH4 is a stable suspending vehicle for compounding with a broad range of different active pharmaceutical ingredients for different medical usages. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Influence of pH and light on the stability of some antioxidants.

PubMed

Racine, P

1981-06-01

Summary Many organic molecules can be oxidized in the presence of oxygen. Light and traces of heavy metal ions catalyse the process of oxidation. The addition of a very small quantity of antioxidant to alcoholic perfumes and cosmetic bases is often made to retard auto-oxidations. Among the parameters which could influence the efficiency of an antioxidant, its intrinsic stability should be considered in the medium to be protected. This stability might conceivably be influenced by the pH, the presence of light, heavy metal ions and microorganisms. In this study we have concentrated on the role played by the first two factors. To eliminate a possible interference by the last two, analytical grades reagents together with chelators and high proof (80% v/v) hydroalcoholic solutions have been used. The antioxidants tested were: BHT, BHA, ethyl gallate, 2, carboxy-6, hydroxy, 2, 5, 7, 8, tetramethyl chroman (Trolox C(R)) and D-L-alpha-tocopherol. Solutions of 0.5 mmol/kg of each antioxidant were prepared in 80% v/v hydroalcoholic solutions and the pH adjusted with citric acid and potassium hydroxyde or hydrochloric acid. The pH extended from 2.5 to 10 and thus largely covers the pH range of cosmetic products. Of each solution, 100ml were kept in hermetically closed 125ml white glass bottles stored at room temperature (22 +/- 2 degrees C) and kept in the dark or exposed to the diffuse daylight of the laboratory. The antioxidants concentrations were determined by linear sweep voltametry on gold or glassy carbon electrodes. Significant differences in behaviour were observed. BHA and BHT are stable regardless of light and pH except at high pH (

Expression and characterization of plant aspartic protease nepenthesin-1 from Nepenthes gracilis.

PubMed

Kadek, Alan; Tretyachenko, Vyacheslav; Mrazek, Hynek; Ivanova, Ljubina; Halada, Petr; Rey, Martial; Schriemer, David C; Man, Petr

2014-03-01

Carnivorous plants of the genus Nepenthes produce their own aspartic proteases, nepenthesins, to digest prey trapped in their pitchers. Nepenthesins differ significantly in sequence from other aspartic proteases in the animal or even plant kingdoms. This difference, which also brings more cysteine residues into the structure of these proteases, can be a cause of uniquely high temperature and pH stabilities of nepenthesins. Their detailed structure characterization, however, has not previously been possible due to low amounts of protease present in the pitcher fluid and also due to limited accessibility of Nepenthes plants. In the present study we describe a convenient way for obtaining high amounts of nepenthesin-1 from Nepenthes gracilis using heterologous production in Escherichia coli. The protein can be easily refolded in vitro and its characteristics are very close to those described for a natural enzyme isolated from the pitcher fluid. Similarly to the natural enzyme, recombinant nepenthesin-1 is sensitive to denaturing and reducing agents. It also has maximal activity around pH 2.5, shows unusual stability at high pH and its activity is not irreversibly inhibited even after prolonged incubation in the basic pH range. On the other hand, temperature stability of the recombinant enzyme is lower in comparison with the natural enzyme, which can be attributed to missing N-glycosylation in the recombinant protein. Copyright © 2013 Elsevier Inc. All rights reserved.

Study of a binary interpenetrated polymeric complex by correlation of rheological parameters with zeta potential and conductivity.

PubMed

Nita, Loredana Elena; Chiriac, Aurica P; Neamtu, Iordana; Bercea, Maria

2010-03-01

The interpenetrated macromolecular chains complexation between poly(aspartic acid) and poly(vinyl alcohol) in aqueous solution it was investigated. The interpolymer complexation process was evaluated through dynamic rheology. The aspects concerning the stability of the tested homopolymers and the prepared interpolymeric complex there were achieved from the evaluation of the aqueous solutions'zeta potential and also by determining the pH influence upon the zeta potential and the conductivity. The data obtained through the rheological dynamic measurements were correlated with the composition of the polymeric mixture, the dependence of zeta potential and conductivity. The study reveals the conditions for the formation of interpenetrated polymeric complex as being a ratio of 70wt.% PAS to 30wt.% PVA at 22 degrees C and 50/50 PAS/PVA ratio at 37 degrees C temperature. From the pH influence upon the zeta potential values it was evidenced the PAS aqueous solution does not reach the isoelectric point. At the same time, PVA solution and the complex PAS/PVA reaches the isoelectric point at strongly acid pH. The better stability of PAS, PVA and their mixture in solution is recorded in the alkaline domain (7.5or=12). The conductivity increases with the rising of the PAS content, pH and temperature. Other characteristics of the prepared interpenetrated polymeric structure, as for example thermal stability, there are also presented.

Stability and reactivity of 2-nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline.

PubMed

Lakshmi, Vijaya M; Hsu, Fong Fu; Schut, Herman A J; Zenser, Terry V

2006-02-01

2-Nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline (N-NO-MeIQx) is a nitrosation product of the food carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and is proposed to form in vivo under inflammatory conditions. This study evaluated the stability and reactivity of N-NO-MeIQx to assess its possible role in the initiation of colon cancer by MeIQx. 14C-N-NO-MeIQx (4 microM) was incubated for 4 h over a range of pH values, and its stability was monitored by HPLC. At pH values from pH 7.4 to 9.0, N-NO-MeIQx was very stable with no detectable change observed. Glutathione (1 mM) did not alter stability at pH 7.4. As the pH decreased, this nitrosamine was less stable with only 48 +/- 1% remaining at pH 5.5 and none remaining at pH 3.5 or 2.0. Major products identified by electrospray ionization mass spectrometry were 3,8-dimethylimidazo[4,5-f]quinoxaline and 2-hydroxy-3,8-dimethylimidazo[4,5-f]quinoxaline. MeIQx was a minor product. At pH 2.0, the t(1/2) for N-NO-MeIQx was reduced from 2.1 +/- 0.2 to 1.2 +/- 0.1 min with 10 mM NaN3. This effect of azide was due to the formation of 2-azido-MeIQx. The binding of 14C-N-NO-MeIQx to DNA increased with decreasing pH. The 10-fold increase in binding observed at pH 2.0 as compared to pH 5.5 was completely inhibited by 10 mM NaN3 due to 2-azido-MeIQx formation. The reactivity of N-NO-MeIQx was compared to N-OH-MeIQx by evaluating adduct formation with 2'-deoxyguanosine 3'-monophosphate (dGp) by 32P-postlabeling. N-OH-MeIQx formed a single major adduct, N-(deoxyguanosin-8-yl)-MeIQx (dG-C8-MeIQx). Incubation of N-NO-MeIQx under inflammatory conditions (pH 5.5 +/- HOCl) produced dG-C8-MeIQx along with 4-6 other adducts. dG-C8-MeIQx formation increased in the presence of HOCl. Liver from a MeIQx-treated mouse contained dG-C8-MeIQx and two other adducts detected with N-NO-MeIQx but not N-OH-MeIQx. These results suggest that N-NO-MeIQx could be genotoxic, is activated by conditions that mediate inflammatory responses, and is a possible cancer risk factor for individuals with inflammation of the colon.

Stability and Reactivity of 2-Nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline

PubMed Central

Lakshmi, Vijaya M.; Hsu, Fong Fu; Schut, Herman A. J.; Zenser, Terry V.

2008-01-01

2-Nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline (N-NO-MeIQx) is a nitrosation product of the food carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and proposed to form in vivo under inflammatory conditions. This study evaluated the stability and reactivity of N-NO-MeIQx to assess its possible role in initiation of colon cancer by MeIQx. 14C-N-NO-MeIQx (4 μM) was incubated for 4 hours over a range of pH values and its stability monitored by HPLC. At pH values from pH 7.4 to 9.0, N-NO-MeIQx was very stable with no detectable change observed. Glutathione (1 mM) did not alter stability at pH 7.4. As pH decreased, this nitrosamine was less stable with only 48 ± 1 % remaining at pH 5.5 and none remaining at pH 3.5 or 2.0. Major products identified by electrospray ionization mass spectrometry were 3,8-dimethylimidazo[4,5-f]quinoxaline and 2-hydroxy-3,8-dimethylimidazo[4,5-f]quinoxaline. MeIQx was a minor product. At pH 2.0, the t1/2 for N-NO-MeIQx was reduced from 2.1 ± 0.2 to 1.2 ± 0.1 min with 10 mM NaN3. This effect of azide was due to formation of 2-azido-MeIQx. The binding of 14C-N-NO-MeIQx to DNA increased with decreasing pH. The 10-fold increase in binding observed at pH 2.0 compared to pH 5.5 was completely inhibited by 10 mM NaN3 due to 2-azido-MeIQx formation. The reactivity of N-NO-MeIQx was compared to N-OH-MeIQx by evaluating adduct formation with 2′-deoxyguanosine 3′-monophosphate (dGp) by 32P-postlabeling. N-OH-MeIQx formed a single major adduct, N-(deoxyguanosin-8-yl)-MeIQx (dG-C8-MeIQx). Incubation of N-NO-MeIQx under inflammatory conditions (pH 5.5 ± HOCl) produced dG-C8-MeIQx along with 4 to 6 other adducts. dG-C8-MeIQx formation increased in the presence of HOCl. Liver from a MeIQx-treated mouse contained dG-C8-MeIQx and two other adducts detected with N-NO-MeIQx, but not N-OH-MeIQx. These results suggest that N-NO-MeIQx could be genotoxic, is activated by conditions that mediate inflammatory responses, and is a possible cancer risk factor for individuals with inflammation of the colon. PMID:16485910

Single cytidine units-templated syntheses of multi-colored water-soluble Au nanoclusters

NASA Astrophysics Data System (ADS)

Jiang, Hui; Zhang, Yuanyuan; Wang, Xuemei

2014-08-01

Ultra-small metallic nanoparticles, or so-called ``nanoclusters'' (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications.Ultra-small metallic nanoparticles, or so-called ``nanoclusters'' (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications. Electronic supplementary information (ESI) available: The feed amount for preparation of Au NCs, photophysical properties of Au NCs, the FL spectra under different pH and reaction time, and XPS results are included. See DOI: 10.1039/c4nr02180k

Microbiological assessment of the application of quicklime and limestone as a measure to stabilize the structure of compaction-prone soils

NASA Astrophysics Data System (ADS)

Deltedesco, Evi; Bauer, Lisa-Maria; Unterfrauner, Hans; Peticzka, Robert; Zehetner, Franz; Keiblinger, Katharina Maria

2014-05-01

Compaction of soils is caused by increasing mechanization of agriculture and forestry, construction of pipelines, surface mining and land recultivation. This results in degradation of aggregate stability and a decrease of pore space, esp. of macropores. It further impairs the water- and air permeability, and restricts the habitat of soil organisms. A promising approach to stabilize the structure and improve the permeability of soils is the addition of polyvalent ions like Ca2+ which can be added in form of quicklime (CaO) and limestone (CaCO3). In this study, we conducted a greenhouse pot experiment using these two different sources of calcium ions in order to evaluate their effect over time on physical properties and soil microbiology. We sampled silty and clayey soils from three different locations in Austria and incubated them with and without the liming materials (application 12.5 g) for 3 months in four replicates. In order to assess short-term and medium-term effects, soil samples were taken 2 days, 1 month and 3 months after application of quicklime and limestone, respectively. For these samples, we determined pH, bulk density, aggregate stability and water retention characteristics. Further, we measured microbiological parameters, such as potential enzyme activities (cellulase, phosphatase, chitinase, protease, phenoloxidase and peroxidase activity), PLFAs, microbial biomass carbon and nitrogen, dissolved organic carbon and nitrogen, nitrate nitrogen and ammonium nitrogen. In contrast to limestone, quicklime significantly improved soil aggregate stability in all tested soils only 2 days after application. Initially, soil pH was strongly increased by quicklime; however, after the second sampling (one month) the pH values of all tested soils returned to levels comparable to the soils treated with limestone. Our preliminary microbiological results show an immediate inhibition effect of quicklime on most potential hydrolytic enzyme activities and an increase in oxidative enzyme activities. These effects seem to be less pronounced in the medium term. In summary our results indicate, that the application of quicklime is a feasible measure for immediate stabilization of the structure of compaction-prone soils, showing only short-term impact on most microbial parameters.

Effect of pH and interaction between egg white protein and hydroxypropymethylcellulose in bulk aqueous medium on foaming properties.

PubMed

Sadahira, Mitie S; Lopes, Fernanda C Rezende; Rodrigues, Maria I; Yamada, Aureo T; Cunha, Rosiane L; Netto, Flavia M

2015-07-10

Egg white protein (EW) is used as surface-active ingredient in aerated food and hydroxypropylmethylcellulose (HPMC) is a polysaccharide that behaves as a surfactant. This study aimed at investigating the effects of process parameters biopolymer concentration (2.0-5.0%, w/w), EW:HPMC ratio (2:1-18:1), pH (3.0-6.0), and the influence of biopolymers' behavior in aqueous solution at different pH on the foaming properties (overrun, drainage, and bubble growth rate). Process parameters had effect on foaming properties. The pH was the major factor influencing the type of EW/HPMC interaction and affected the foaming properties of biopolymer mixture. At pH 3.0, EW and HPMC showed thermodynamic compatibility leading to better foaming properties, higher foaming capacity, and stability than without HPMC addition whereas at pH 4.5 and 6.0, EW and HPMC are incompatible that causes lower stability concerning the disproportionation comparing to foam without HPMC. At pH between 3.0 and 4.5, HPMC improves foaming properties of aerated products. Copyright © 2015 Elsevier Ltd. All rights reserved.

TRLFS study on the complexation of Cm(III) and Eu(III) with SO3-Ph-BTBP.

PubMed

Wagner, Christoph; Müllich, Udo; Geist, Andreas; Panak, Petra J

2015-10-21

The complexation of Cm(iii) and Eu(iii) with a water soluble BTBP (sodium 3,3',3'',3'''-([2,2'-bipyridine]-6,6'-diylbis(1,2,4-triazine-3,5,6-triyl))tetrabenzenesulfonate, SO3-Ph-BTBP) is studied using time resolved laser fluorescence spectroscopy. For the complexation of Cm(iii) the influence of the medium (10(-3) M HClO4→ 0.5 M HNO3) is investigated in detail revealing important impacts of the applied medium (pH, ionic strength, anions) on the speciation and conditional stability constants. SO3-Ph-BTBP forms 1 : 2 complexes with Cm(iii) and Eu(iii). The conditional stability constants of [Cm(SO3-Ph-BTBP)2](5-) and [Eu(SO3-Ph-BTBP)2](5-) in 0.5 M HNO3 are determined to be log β02 = 7.3 ± 0.3 and log β02 = 5.4 ± 0.5, respectively. The difference of 1.9 orders of magnitude is in line with hydrophobic BT(B)P type ligands and shows that the selectivity is not affected by tuning the hydrophilicity using SO3-Ph-side chains.

The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions.

PubMed

Kalliola, Simo; Repo, Eveliina; Srivastava, Varsha; Heiskanen, Juha P; Sirviö, Juho Antti; Liimatainen, Henrikki; Sillanpää, Mika

2017-05-01

In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca 2+ ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca 2+ ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH 3 + and COO - groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Development of a pH sensor using nanoporous nanostructures of NiO.

PubMed

Ibupoto, Z H; Khun, K; Willander, M

2014-09-01

Glass is the conventional material used in pH electrodes to monitor pH in various applications. However, the glass-based pH electrode has some limitations for particular applications. The glass sensor is limited in the use of in vivo biomedical, clinical or food applications because of the brittleness of glass, its large size, the difficulty in measuring small volumes and the absence of deformation (inflexibility). Nanostructure-based pH sensors are very sensitive, reliable, fast and applicable towards in vivo measurements. In this study, nanoporous NiO nanostructures are synthesized on a gold-coated glass substrate by a hydrothermal route using poly(vinyl alcohol) (PVA) as a stabilizer. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used for the morphological and crystalline studies. The grown NiO nanostructures are uniform and dense, and they possess good crystallinity. A pH sensor based on these NiO nanostructures was developed by testing the different pH values from 2-12 of phosphate buffered saline solution. The proposed pH sensor showed robust sensitivity of -43.74 ± 0.80 mV/pH and a quick response time of less than 10 s. Moreover, the repeatability, reproducibility and stability of the presented pH sensor were also studied.

The mechanical stability of polyimide films at high pH

NASA Technical Reports Server (NTRS)

Croall, Catharine I.; St.clair, Terry L.

1990-01-01

Polyimide insulated electrical wire has been widely used in the aerospace industry in commercial, military, and to a lesser degree, general aviation aircraft since the early 1970s. Wiring failures linked to insulation damage have drawn much attention in the media and concerns have developed regarding the long term stability and safety of polyimide insulated electrical wire. The mechanical durability and chemical stability of polyimide insulated wire are affected by hydrolysis, notch propagation, wet and dry arc tracking, topcoat flaking, and degradation due to high pH fluids. Several polyimides were selected for evaluation for resistance to degradation by various aqueous alkaline solutions. The polyimides under evaluation include commercially available films such as KAPTON (tradename), APICAL (tradename), LARC-TPI, and UPILEX (tradename) R and S, as well as a number of experimental films prepared at NASA-Langley. Material properties investigated include viscosity, solubility, moisture absorption, glass transition temperature, dielectric constant, and mechanical properties before and after exposure to various conditions.

Preparation of pH-sensitive anionic liposomes designed for drug delivery system (DDS) application.

PubMed

Aoki, Asami; Akaboshi, Hikaru; Ogura, Taku; Aikawa, Tatsuo; Kondo, Takeshi; Tobori, Norio; Yuasa, Makoto

2015-01-01

We prepared pH-sensitive anionic liposomes composed solely of anionic bilayer membrane components that were designed to promote efficient release of entrapped agents in response to acidic pH. The pH-sensitive anionic liposomes showed high dispersion stability at neutral pH, but the fluidity of the bilayer membrane was enhanced in an acidic environment. These liposomes were rather simple and were composed of dimyristoylphosphatidylcholine (DMPC), an anionic bilayer membrane component, and polyoxyethylene sorbitan monostearate (Tween 80). In particular, the present pH-sensitive anionic liposomes showed higher temporal stability than those of conventional DMPC/DPPC liposomes. We found that pHsensitive properties strongly depended on the molecular structure, pKa value, and amount of an incorporated anionic bilayer membrane component, such as sodium oleate (SO), dimyristoylphosphatidylserine (DMPS), or sodium β-sitosterol sulfate (SS). These results provide an opportunity to manipulate liposomal stability in a pH-dependent manner, which could lead to the formulation of a high performance drug delivery system (DDS).

Microencapsulation by freeze-drying of potassium norbixinate and curcumin with maltodextrin: stability, solubility, and food application.

PubMed

Sousdaleff, Mirian; Baesso, Mauro Luciano; Medina Neto, Antonio; Nogueira, Ana Cláudia; Marcolino, Vanessa Aparecida; Matioli, Graciette

2013-01-30

Stability of potassium norbixinate and curcumin by microencapsulation with maltodextrin DE20 and freeze-drying was evaluated as a function of exposition to light, air, different pH, water solubility, and in food applications. The best results were obtained with microencapsulated potassium norbixinate 1:20, which, when vacuum-packed and in the presence of natural light, showed color retention of 78%, while microencapsulated curcumin 1:20 showed color retention of 71%. Differential scanning calorimetry and thermogravimetry provided an indication of interaction between colorants and maltodextrin. Photoacoustic spectroscopy (PAS) showed that free and microencapsulated colorants exhibited high rates of absorption throughout the measured spectral region. This work evidenced that the freeze-drying process is favorable for microencapsulation of curcumin by maltodextrin, providing improved solubility to the microencapsulated colorant. Both microencapsulated colorants showed relevant results for use in a wide range of pH and food applications. The PAS technique was useful for the evaluation of the stability of free and microencapsulated colorants.

Imaging carbon nanotube interactions, diffusion, and stability in nanopores.

PubMed

Eichmann, Shannon L; Smith, Billy; Meric, Gulsum; Fairbrother, D Howard; Bevan, Michael A

2011-07-26

We report optical microscopy measurements of three-dimensional trajectories of individual multiwalled carbon nanotubes (MWCNTs) in nanoscale silica slit pores. Trajectories are analyzed to nonintrusively measure MWCNT interactions, diffusion, and stability as a function of pH and ionic strength. Evanescent wave scattering is used to track MWCNT positions normal to pore walls with nanometer-scale resolution, and video microscopy is used to track lateral positions with spatial resolution comparable to the diffraction limit. Analysis of MWCNT excursions normal to pore walls yields particle-wall potentials that agree with theoretical electrostatic and van der Waals potentials assuming a rotationally averaged potential of mean force. MWCNT lateral mean square displacements are used to quantify translational diffusivities, which are comparable to predictions based on the best available theories. Finally, measured MWCNT pH and ionic strength dependent stabilities are in excellent agreement with predictions. Our findings demonstrate novel measurement and modeling tools to understand the behavior of confined MWCNTs relevant to a broad range of applications.

Stability of extemporaneous enalapril maleate suspensions for pediatric use prepared from commercially available tablets.

PubMed

Sosnowska, Katarzyna; Winnicka, Katarzyna; Czajkowska-Kośnik, Anna

2009-01-01

In this paper, the stability of enalapril maleate in oral formulations prepared from commercially available tablets was investigated. Extemporaneously compounded, 0.1 mg/mL and 1.0 mg/mL, oral suspensions of enalapril maleate in sugar-containing and sugar-free vehicles were stored in the absence of light at 4 degrees and 25 degrees C for 30 days. Enalapril maleate stability was quantified after 7, 14, 21, and 30 days using HPLC method. Viscosities and pH of prepared suspensions were measured on each study day and no appreciable changes from the initial pH and initial viscosities occurred in any of the samples both at 25 degrees and 4 degrees C. It was shown that all the formulations retain minimum 98% of the initial enalapril maleate concentration after 30 days of storage at 25 degrees and 4 degrees C and they may provide an option in situations where the marketed suspension is unavailable.

The biochemical characterization, stabilization studies and the antiproliferative effect of bromelain against B16F10 murine melanoma cells.

PubMed

São Paulo Barretto Miranda, Íngara Keisle; Fontes Suzart Miranda, Anderson; Souza, Fernanda Vidigal Duarte; Vannier-Santos, Marcos André; Pirovani, Carlos Priminho; Pepe, Iuri Muniz; Rodowanski, Ivanoé João; Ferreira, Katiúcia Tícila de Souza Eduvirgens; Mendes Souza Vaz, Luciano; de Assis, Sandra Aparecida

2017-06-01

The current study aims to extract bromelain from different parts (stem, crown, peels, pulp and leaves) of Ananas comosus var. comosus AGB 772; to determine of optimum pH and temperature; to test bromelain stability in disodium EDTA and sodium benzoate, and to investigate its pharmacological activity on B16F10 murine melanoma cells in vitro. The highest enzymatic activity was found in bromelain extracted from the pulp and peel. The optimum bromelain pH among all studied pineapple parts was 6.0. The optimum temperature was above 50 °C in all bromelain extracts. The fluorescence analysis confirmed the stability of bromelain in the presence of EDTA and sodium benzoate. Bromelain was pharmacologically active against B16F10 melanoma cells and it was possible verifying approximately 100% inhibition of tumor cell proliferation in vitro. Since bromelain activity was found in different parts of pineapple plants, pineapple residues from the food industry may be used for bromelain extraction.

Stability of gabapentin in extemporaneously compounded oral suspensions

PubMed Central

Friciu, Mihaela; Roullin, V. Gaëlle

2017-01-01

This study reports the stability of extemporaneously prepared gabapentin oral suspensions prepared at 100 mg/mL from bulk drug and capsules in either Oral Mix or Oral Mix SF suspending vehicles. Suspensions were packaged in amber plastic bottles and amber plastic syringes at 25°C / 60%RH for up to 90 days. Throughout the study period, the following tests were performed to evaluate the stability of the preparations: organoleptic inspection to detect homogeneity, color or odor changes; pH measurements; and gabapentin assay using a stability-indicating HPLC-UV method. As crystallization was observed at 5°C, storage at this temperature condition is not recommended. All preparations stored at 25°C / 60%RH remained stable for the whole study duration of 90 days. PMID:28414771

[Injectable hospital preparation of valine labeled with the carbon 13 and nitrogen 15 (5 mg/mL) for a clinical trial on the brain tumor metabolism: Pharmaceutical control of active pharmaceutical ingredient and stability study of the finished product].

PubMed

Tall, M L; Diouf, E; Filali, S; Sauvinet, V; Laleye, D; Dhelens, C; Salmon, D; Gabert, L; Nugue, G; Sandre-Balester, C; Berger, F; Pirot, F; Pivot, C

2015-09-01

The L-Valine labeled (L-[U-(13)C,(15)N] Val) is a stable isotopic tracer administered by parenteral route within the framework of a new clinical research program concerning the brain tumor metabolism. To meet regulatory requirements and have ready to use solution with an expiration date, a pharmaceutical control of active pharmaceutical ingredient followed by stability study of hospital preparation were realised. After the pharmaceutical control of the L-[U-(13)C,(15)N] Val, the hospital preparation was prepared according to the good manufacturing preparation. Prepared bottles were stored at 5°C±3°C and 25°C±2°C for six months. The stability of the preparation was determined by physico-chemical controls (pH, osmolality, sub-visible particles, L-[U-(13)C,(15)N] Val concentration, sodium concentration, isotopic enrichment) and microbiological (bacterial endotoxin and sterility). Concentrations of L-[U-(13)C, (15)N] Val and sodium does not significantly decrease during the stability study. In parallel, no change in pH and osmolality were highlighted. Isotopic enrichment higher than 99.9% reflected the stability of labeling of L-valine molecule. The sub-visible particles, the bacterial endotoxin and sterility were in accordance with the European Pharmacopoeia attesting limpidity, apyrogenicity and sterility of this injectable preparation. The stability of this hospital preparation of L-[U-(13)C, (15)N] Val has been demonstrated for six months at 5°C±3°C and 25°C±2°C, ensuring a parenteral administration as part of the clinical trial. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Fabrication of amorphous curcumin nanosuspensions using β-lactoglobulin to enhance solubility, stability, and bioavailability.

PubMed

Aditya, N P; Yang, Hanjoo; Kim, Saehoon; Ko, Sanghoon

2015-03-01

Curcumin has low aqueous stability and solubility in its native form. It also has a low bioavailability which presents a major barrier to its use in fortifying food products. The aim of this work was to reduce the size of curcumin crystals to the nanoscale and subsequently stabilize them in an amorphous form. To this end, amorphous curcumin nanosuspensions were fabricated using the antisolvent precipitation method with β-lactoglobulin (β-lg) as a stabilizer. The resulting amorphous curcumin nanosuspensions were in the size range of 150-175 nm with unimodal size distribution. The curcumin particles were amorphous and were molecularly dispersed within the β-lg as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The solubility of the amorphous curcumin nanosuspension was enhanced ∼35-fold due to the reduced size and lower crystallinity. Among the formulations, the amorphous curcumin nanosuspensions stabilized with β-lg and prepared at pH 3.4 (β-lg-cur 3.4), showed maximum aqueous stability which was >90% after 30 days. An in vitro study using Caco-2 cell lines showed a significant increase in curcumin bioavailability after stabilization with β-lg. Copyright © 2015 Elsevier B.V. All rights reserved.

Design of experiments reveals critical parameters for pilot-scale freeze-and-thaw processing of L-lactic dehydrogenase.

PubMed

Roessl, Ulrich; Humi, Sebastian; Leitgeb, Stefan; Nidetzky, Bernd

2015-09-01

Freezing constitutes an important unit operation of biotechnological protein production. Effects of freeze-and-thaw (F/T) process parameters on stability and other quality attributes of the protein product are usually not well understood. Here a design of experiments (DoE) approach was used to characterize the F/T behavior of L-lactic dehydrogenase (LDH) in a 700-mL pilot-scale freeze container equipped with internal temperature and pH probes. In 24-hour experiments, target temperature between -10 and -38°C most strongly affected LDH stability whereby enzyme activity was retained best at the highest temperature of -10°C. Cooling profile and liquid fill volume also had significant effects on LDH stability and affected the protein aggregation significantly. Parameters of the thawing phase had a comparably small effect on LDH stability. Experiments in which the standard sodium phosphate buffer was exchanged by Tris-HCl and the non-ionic surfactant Tween 80 was added to the protein solution showed that pH shift during freezing and protein surface exposure were the main factors responsible for LDH instability at the lower freeze temperatures. Collectively, evidence is presented that supports the use of DoE-based systematic analysis at pilot scale in the identification of F/T process parameters critical for protein stability and in the development of suitable process control strategies. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Relative Stability of the Scleroglucan Triple-Helix and Single Strand: an Insight from Computational and Experimental Techniques

NASA Astrophysics Data System (ADS)

Bocchinfuso, Gianfranco; Mazzuca, Claudia; Conflitti, Paolo; Cori, Davide; Coviello, Tommasina; Palleschi, Antonio

2016-09-01

Scleroglucan (Sclg) is a polysaccharide that exhibits a triple helix conformation (triplex), both in aqueous solution and in the solid state, which is lost in DMSO solution, at high temperature and at high pH values. The triplex conformation is characterized by a high rigidity, responsible of Sclg peculiar properties. Although the relative stability of triplex and single strand has already been investigated, different structural details are still missing. In the present study, we analyse the structural properties and the factors stabilizing the single chain and the triple helix of Sclg in different conditions. To this end, we simulated both systems in water and in DMSO. The triple helix has been also simulated in the presence of chemical damages on one of the three strands (to reproduce in silico the effect of sonication) or by inducing a partial unfolding of the triplex structure. The computational results have been compared with experimental evidences in which the triplex denaturation, at alkaline pH values, has been followed by monitoring the UV and CD spectra of Congo red, used as a probe molecule. Our results indicate that sonication breaks the Sclg chains without appreciably changing the stability of the other tracts of triple helix. The simulated perturbed or partially unfolded triplexes show a clear tendency to form less ordered aggregates. Finally, our simulations put in evidence an important role of the hydrophobic interactions both in the triplex stability and in the aggregation processes observed after induced denaturation.

Computational design of a pH stable enzyme: understanding molecular mechanism of penicillin acylase's adaptation to alkaline conditions.

PubMed

Suplatov, Dmitry; Panin, Nikolay; Kirilin, Evgeny; Shcherbakova, Tatyana; Kudryavtsev, Pavel; Svedas, Vytas

2014-01-01

Protein stability provides advantageous development of novel properties and can be crucial in affording tolerance to mutations that introduce functionally preferential phenotypes. Consequently, understanding the determining factors for protein stability is important for the study of structure-function relationship and design of novel protein functions. Thermal stability has been extensively studied in connection with practical application of biocatalysts. However, little work has been done to explore the mechanism of pH-dependent inactivation. In this study, bioinformatic analysis of the Ntn-hydrolase superfamily was performed to identify functionally important subfamily-specific positions in protein structures. Furthermore, the involvement of these positions in pH-induced inactivation was studied. The conformational mobility of penicillin acylase in Escherichia coli was analyzed through molecular modeling in neutral and alkaline conditions. Two functionally important subfamily-specific residues, Gluβ482 and Aspβ484, were found. Ionization of these residues at alkaline pH promoted the collapse of a buried network of stabilizing interactions that consequently disrupted the functional protein conformation. The subfamily-specific position Aspβ484 was selected as a hotspot for mutation to engineer enzyme variant tolerant to alkaline medium. The corresponding Dβ484N mutant was produced and showed 9-fold increase in stability at alkaline conditions. Bioinformatic analysis of subfamily-specific positions can be further explored to study mechanisms of protein inactivation and to design more stable variants for the engineering of homologous Ntn-hydrolases with improved catalytic properties.

Computational Design of a pH Stable Enzyme: Understanding Molecular Mechanism of Penicillin Acylase's Adaptation to Alkaline Conditions

PubMed Central

Suplatov, Dmitry; Panin, Nikolay; Kirilin, Evgeny; Shcherbakova, Tatyana; Kudryavtsev, Pavel; Švedas, Vytas

2014-01-01

Protein stability provides advantageous development of novel properties and can be crucial in affording tolerance to mutations that introduce functionally preferential phenotypes. Consequently, understanding the determining factors for protein stability is important for the study of structure-function relationship and design of novel protein functions. Thermal stability has been extensively studied in connection with practical application of biocatalysts. However, little work has been done to explore the mechanism of pH-dependent inactivation. In this study, bioinformatic analysis of the Ntn-hydrolase superfamily was performed to identify functionally important subfamily-specific positions in protein structures. Furthermore, the involvement of these positions in pH-induced inactivation was studied. The conformational mobility of penicillin acylase in Escherichia coli was analyzed through molecular modeling in neutral and alkaline conditions. Two functionally important subfamily-specific residues, Gluβ482 and Aspβ484, were found. Ionization of these residues at alkaline pH promoted the collapse of a buried network of stabilizing interactions that consequently disrupted the functional protein conformation. The subfamily-specific position Aspβ484 was selected as a hotspot for mutation to engineer enzyme variant tolerant to alkaline medium. The corresponding Dβ484N mutant was produced and showed 9-fold increase in stability at alkaline conditions. Bioinformatic analysis of subfamily-specific positions can be further explored to study mechanisms of protein inactivation and to design more stable variants for the engineering of homologous Ntn-hydrolases with improved catalytic properties. PMID:24959852

Oligomeric stability of Rapana venosa hemocyanin (RvH) and its structural subunits.

PubMed

Dolashka-Angelova, Pavlina; Schwarz, Heinz; Dolashki, Aleksandar; Stevanovic, Stefan; Fecker, Miriam; Saeed, Muhammad; Voelter, Wolfgang

2003-03-21

The two structural subunits RvH1 and RvH2 were separated after overnight dialysis of Rapana venosa Hc against 130 mM Gly/NaOH buffer, pH 9.6, on an ion exchange column Hiload 26/10 Sepharose Q using a fast performance liquid chromatography (FPLC) system. The reassociation characteristics of these two RvH isoforms and the native molecule were studied in buffers with different pH values and concentrations of Ca(2+) and Mg(2+). Reassociation of mixed RvH subunits was performed over a period of several days using a stabilizing buffer (SB) of pH 7.0 containing different concentrations of Ca(2+) and Mg(2+) ions. After 2 days of dialysis, an RvH subunit mixture of didecamers and multidecamers was observed in the presence of 100 mM CaCl(2) and MgCl(2), though RvH1 and RvH2 are biochemically and immunologically different and have also different dissociation properties. The reassociation, performed at pH 9.6 with 2 mM CaCl(2) and MgCl(2) at 4 degrees C over a period of one to several weeks, led to the formation of decameric oligomers, while didecamers formed predominantly in the SB at pH 7.0. Higher concentrations of calcium and magnesium ions led to a more rapid reassociation of RvH1 resulting in long stable multidecamers and helical tubules, which were stable and slowly dissociated into shorter multidecamers and decamers at higher pH values. The reassociation of the RvH2 structural subunit in the same buffers processed slowly and yielded didecamers, shorter tubule polymers and long multidecamers which are less stable at higher pH values. The stability of RvH isoforms under varying ionic conditions is compared with the stability of keyhole limpet (KLH, Megathura crenulata) hemocyanin (KLH) and Haliotis tuberculata hemocyanin (HtH) isoforms. The process of dissociation and reassociation is connected with changes of the fluorescence intensity at 600 nm, which can be explained by differences in opalescence of the solutions of these two isoforms. The solutions of longer tubule polymers and multidecamers of RvH1 show a higher opalescence compared to the solutions of shorter helical tubules and multidecamers of RvH2.

Chemical Stability of Bioglass in Simulated Oral Environment.

PubMed

Sm, Moazzami; R, Sadid Zadeh; K, Kianoush; M, Sarmad; F, Barani Karbaski; R, Amiri Daluyi; Rb, Kazemi

2016-09-01

Bioglasses are a series of biocompatible dental materials, which are considered as light conducting inserts in resin composite restorations. Consequently, their chemical stability is more essential when they are used in conjunction with resin composite. The aim of this study was to evaluate and compare the chemical stability of Bioglass with dental porcelain and resin composite by determining the amount of released K+, Na+, Ca2+ ions and silicone elements from these materials as a result of exposure to tested solutions with different pH levels including: Sodium Bicarbonate [SB, (pH=9.2)], Sodium Buffer Lactate [SBL, (pH=2.4)], Acetic Acid [AA, (pH=2.4)], and Distilled Water [DW, (pH=6.2)]. In this experimental study, forty 2.0 × 4.0 cylindrical rods for each tested material group (Dental porcelain, Resin composite and Bioglass) were prepared. They were divided into four subgroups of 10 rods each, which immersed in one of the four testing solutions in a designated container. The containers were stored at 50°C and 100% humidity for one week. The released ions were measured by using a spectrophotometer (µg/cm 2 /ml). The data were statistically analyzed by nonparametric Kruskal-Wallis H test. It was observed that the tested materials released ions at different levels of concentration. The significant amounts of Sodium, Calcium, and Silicon ions release were measured in Bioglass subgroups in all the tested solutions ( p < 0.001). Potassium ion release from dental porcelain was the largest in all solutions except for AA in which Bioglass had the greatest potassium ion release ( p < 0.001). A greater structural instability was observed for Biogalss group than dental porcelain and resin composite in testing solutions with different pH levels.

pH driven fibrillar aggregation of the super-sweet protein Y65R-MNEI: A step-by-step structural analysis.

PubMed

Pica, Andrea; Leone, Serena; Di Girolamo, Rocco; Donnarumma, Federica; Emendato, Alessandro; Rega, Michele Fortunato; Merlino, Antonello; Picone, Delia

2018-04-01

MNEI and its variant Y65R-MNEI are sweet proteins with potential applications as sweeteners in food industry. Also, they are often used as model systems for folding and aggregation studies. X-ray crystallography was used to structurally characterize Y65R-MNEI at five different pHs, while circular dichroism and fluorescence spectroscopy were used to study their thermal and chemical stability. ThT assay and AFM were used for studying the kinetics of aggregation and morphology of the aggregates. Crystal structures of Y65R-MNEI revealed the existence of a dimer in the asymmetric unit, which, depending on the pH, assumes either an open or a closed conformation. The pH dramatically affects kinetics of formation and morphology of the aggregates: both MNEI and Y65R-MNEI form fibrils at acidic pH while amorphous aggregates are observed at neutral pH. The mutation Y65R induces structural modifications at the C-terminal region of the protein, which account for the decreased stability of the mutant when compared to MNEI. Furthermore, the pH-dependent conformation of the Y65R-MNEI dimer may explain the different type of aggregates formed as a function of pH. The investigation of the structural bases of aggregation gets us closer to the possibility of controlling such process, either by tuning the physicochemical environmental parameters or by site directed mutagenesis. This knowledge is helpful to expand the range of stability of proteins with potential industrial applications, such as MNEI and its mutant Y65R-MNEI, which should ideally preserve their structure and soluble state through a wide array of conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Physico-chemical stability of eribulin mesylate containing concentrate and ready-to-administer solutions.

PubMed

Spindeldreier, Kirsten; Thiesen, Judith; Lipp, Hans-Peter; Krämer, Irene

2014-06-01

The aim of this study was to determine the stability of commercially available eribulin mesylate containing injection solution as well as diluted ready-to-administer solutions stored under refrigeration or at room temperature. Stability was studied by a novel developed stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) assay with ultraviolet detection (detection wavelength 200 nm). Triplicate test solutions of eribulin mesylate containing injection concentrate (0.5 mg/mL) and with 0.9% sodium chloride solution diluted ready-to-administer preparations (0.205 mg/mL eribulin mesylate in polypropylene (PP) syringes, 0.020 mg/mL eribulin mesylate in polypropylene/polyethylene (PE) bags) were stored protected from light either at room temperature (25) or under refrigeration (2-8). Samples were withdrawn on day 0 (initial), 1, 3, 5, 7, 14, 21 and 28 of storage and assayed. Physical stability was determined by measuring the pH value once a week and checking for visible precipitations or colour changes. The stability tests revealed that concentrations of eribulin mesylate remained unchanged over a period of 28 days irrespective of concentration, container material or storage temperature. Neither colour changes nor visible particles have been observed. The pH value varied slightly over time but remained in the stability favourable range of 5-9. Eribulin mesylate injection (0.5 mg/mL) is physico-chemically stable over a period of 28 days after first puncture of the vial. After dilution with 0.9% NaCl vehicle solution, ready-to-administer eribulin mesylate injection solutions (0.205 mg/mL in PP syringe) and infusion solutions (0.02 mg/mL in prefilled PP/PE bags) are physico-chemically stable for a period of at least four weeks either refrigerated or stored at room temperature. For microbiological reasons storage under refrigeration is recommended.

Alcohol oxidase protein mediated in-situ synthesized and stabilized gold nanoparticles for developing amperometric alcohol biosensor.

PubMed

Chinnadayyala, Somasekhar R; Santhosh, Mallesh; Singh, Naveen K; Goswami, Pranab

2015-07-15

A simple one step method for the alcohol oxidases (AOx) protein mediated synthesis of gold nano-particles (AuNPs) in alkaline (pH 8.5) condition with simultaneous stabilization of the nanoparticles on the AOx protein surface under native environment has been developed. The formation of the AOx conjugated AuNPs was confirmed by advanced analytical and spectroscopic techniques. The significant increase in zeta potential (ζ) value of -57mV for the synthesized AOx-AuNPs conjugate from the AOx (pI 4.5) protein (ζ, -30mV) implied good stability of the in-situ synthesized nano-conjugate. The AOx-AuNPs conjugate showed steady stability in alkaline (upto pH 8.5) and NaCl (up to 10(-1)M) solutions. The efficiency (Kcat/Km) of the AuNP conjugated AOx was increased by 18% from the free enzyme confirming the activating role of the surface stabilized AuNPs for the enzyme. The AuNPs-AOx conjugate was encapsulated with polyaniline (PANI) synthesized by oxidative polymerization of aniline using H2O2 generated in-situ from the AOx catalysed oxidation of alcohol. The PANI encapsulated AuNPs-AOx assembly was stabilized on a glassy carbon electrode (GCE) by chitosan-Nafion mixture and then utilized the fabricated bioelectrode for detection of alcohol amperometrically using H2O2 as redox indicator at +0.6V. The constructed biosensor showed high operational stability (6.3% loss after 25 measurements), wide linear detection range of 10µM-4.7mM (R(2)=0.9731), high sensitivity of 68.3±0.35µAmM(-1) and low detection limit of 7±0.027µM for ethanol. The fabricated bioelectrode was successfully used for the selective determination of alcohol in beverage samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Conformational and Thermal Stability Improvements for the Large-Scale Production of Yeast-Derived Rabbit Hemorrhagic Disease Virus-Like Particles as Multipurpose Vaccine

PubMed Central

Méndez, Lídice; González, Nemecio; Parra, Francisco; Martín-Alonso, José M.; Limonta, Miladys; Sánchez, Kosara; Cabrales, Ania; Estrada, Mario P.; Rodríguez-Mallón, Alina; Farnós, Omar

2013-01-01

Recombinant virus-like particles (VLP) antigenically similar to rabbit hemorrhagic disease virus (RHDV) were recently expressed at high levels inside Pichia pastoris cells. Based on the potential of RHDV VLP as platform for diverse vaccination purposes we undertook the design, development and scale-up of a production process. Conformational and stability issues were addressed to improve process control and optimization. Analyses on the structure, morphology and antigenicity of these multimers were carried out at different pH values during cell disruption and purification by size-exclusion chromatography. Process steps and environmental stresses in which aggregation or conformational instability can be detected were included. These analyses revealed higher stability and recoveries of properly assembled high-purity capsids at acidic and neutral pH in phosphate buffer. The use of stabilizers during long-term storage in solution showed that sucrose, sorbitol, trehalose and glycerol acted as useful aggregation-reducing agents. The VLP emulsified in an oil-based adjuvant were subjected to accelerated thermal stress treatments. None to slight variations were detected in the stability of formulations and in the structure of recovered capsids. A comprehensive analysis on scale-up strategies was accomplished and a nine steps large-scale production process was established. VLP produced after chromatographic separation protected rabbits against a lethal challenge. The minimum protective dose was identified. Stabilized particles were ultimately assayed as carriers of a foreign viral epitope from another pathogen affecting a larger animal species. For that purpose, a linear protective B-cell epitope from Classical Swine Fever Virus (CSFV) E2 envelope protein was chemically coupled to RHDV VLP. Conjugates were able to present the E2 peptide fragment for immune recognition and significantly enhanced the peptide-specific antibody response in vaccinated pigs. Overall these results allowed establishing improved conditions regarding conformational stability and recovery of these multimers for their production at large-scale and potential use on different animal species or humans. PMID:23460801

Protein-silver nanoparticle interactions to colloidal stability in acidic environments.

PubMed

Tai, Jui-Ting; Lai, Chao-Shun; Ho, Hsin-Chia; Yeh, Yu-Shan; Wang, Hsiao-Fang; Ho, Rong-Ming; Tsai, De-Hao

2014-11-04

We report a kinetic study of Ag nanoparticles (AgNPs) under acidic environments (i.e., pH 2.3 to pH ≈7) and systematically investigate the impact of protein interactions [i.e., bovine serum albumin (BSA) as representative] to the colloidal stability of AgNPs. Electrospray-differential mobility analysis (ES-DMA) was used to characterize the particle size distributions and the number concentrations of AgNPs. Transmission electron microscopy was employed orthogonally to provide visualization of AgNPs. For unconjugated AgNPs, the extent of aggregation, or the average particle size, was shown to be increased significantly with an increase of acidity, where a partial coalescence was found between the primary particles of unconjugated AgNP clusters. Aggregation rate constant, kD, was also shown to be proportional to acidity, following a correlation of log(kD) = -1.627(pH)-9.3715. Using ES-DMA, we observe BSA had a strong binding affinity (equilibrium binding constant, ≈ 1.1 × 10(6) L/mol) to the surface of AgNPs, with an estimated maximum molecular surface density of ≈0.012 nm(-2). BSA-functionalized AgNPs exhibited highly-improved colloidal stability compared to the unconjugated AgNPs under acidic environments, where both the acid-induced interfacial dissolution and the particle aggregation became negligible. Results confirm a complex mechanism of colloidal stability of AgNPs: the aggregation process was shown to be dominant, and the formation of BSA corona on AgNPs suppressed both particle aggregation and interfacial dissolution of AgNP samples under acidic environments.

Nano-assemblies of cationic mPEG brush block copolymers with gadolinium polyoxotungstate [Gd(W5O18)2]9- form stable, high relaxivity MRI contrast agents.

PubMed

Ly, Joanne; Li, Yuhuan; Vu, Mai N; Moffat, Bradford A; Jack, Kevin S; Quinn, John F; Whittaker, Michael R; Davis, Thomas P

2018-04-19

Polyoxometalates (POMs) incorporating paramagnetic ions, such as gadolinium, show promise as contrast agents for application in magnetic resonance imaging (MRI). Specifically, [Gd(W5O18)2]9- (denoted as GdWO) has been reported to have a higher relaxivity than commercially available contrast agents, but it's clinical utility has been limited by the intrinsic instability of POMs at physiological pH (7.4). In the current report we present a stability study on neat GdWO and nano-assemblies of block copolymers with GdWO in the pH range 5.0-7.4 to assess their suitability as MRI contrast agents. Neat GdWO only maintained structural stability between pH 5.4 and 6.4, and demonstrated poor MRI contrast at pH 7.4. To address this pH instability, GdWO was self-assembled with cationic mPEG brush block copolymers containing 20 or 40 units derived from the cationic monomer, 2-dimethylaminoethyl methacrylate (DMAEMA). Nano-assemblies with different charge ratios were synthesised and characterised according to their size, stability, contrasting properties and toxicity. The longitudinal relaxivity (r1) of the nano-assemblies was found to be dependent on the charge ratio, but not on the length of the cationic polymer block. Further investigation of PDMAEMA20 nano-assemblies demonstrated that they were stable over the pH range 5.0-7.4, exhibiting a higher r1 than either neat GdWO (2.77 s-1 mM-1) or clinical MRI contrast agent Gd-DTPA (4.1 s-1 mM-1) at pH 7.4. Importantly, the nano-assembly with the lowest charge ratio (0.2), showed the highest r1 (12.1 s-1 mM-1) whilst, stabilising GdWO over the pH range studied, eliciting low toxicity with MDA-MB231 cells.

Engineering cocrystal solubility, stability, and pH(max) by micellar solubilization.

PubMed

Huang, Neal; Rodríguez-Hornedo, Naír

2011-12-01

Cocrystals offer great promise in enhancing drug aqueous solubilities, but face the challenge of conversion to a less soluble drug when in contact with solvent. This manuscript shows that differential solubilization of cocrystal components by micelles can impart thermodynamic stability to otherwise unstable cocrystals. The theoretical foundation for controlling cocrystal solubility and stability is presented by considering the contributions of micellar solubilization and ionization of cocrystal components. A surfactant critical stabilization concentration (CSC) and a solution pH (pH(max)) where cocrystal and drug are thermodynamically stable are shown to characterize cocrystal stability in micellar solutions. The solubility, CSC, and pH(max) of carbamazepine cocrystals in micellar solutions of sodium lauryl sulfate predicted by the models are in very good agreement with experimental measurements. The findings from this work demonstrate that cocrystal CSC and pH(max) can be tailored from the selection of coformer and solubilizing additives such as surfactants, thus providing an unprecedented level of control over cocrystal stability and solubility via solution phase chemistry. Copyright © 2011 Wiley-Liss, Inc.

Effect of natural ageing on volume stability of MSW and wood waste incineration residues

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gori, Manuela, E-mail: manuela.gori@dicea.unifi.it; Bergfeldt, Britta; Reichelt, Jürgen

2013-04-15

Highlights: ► Natural weathering on BA from MSW and wood waste incineration was evaluated. ► Type of mineral phases, pH and volume stability were considered. ► Weathering reactions effect in improved stability of the materials. - Abstract: This paper presents the results of a study on the effect of natural weathering on volume stability of bottom ash (BA) from municipal solid waste (MSW) and wood waste incineration. BA samples were taken at different steps of treatment (fresh, 4 weeks and 12 weeks aged) and then characterised for their chemical and mineralogical composition and for volume stability by means of themore » mineralogical test method (M HMVA-StB), which is part of the German quality control system for using aggregates in road construction (TL Gestein-StB 04). Changes of mineralogical composition with the proceeding of the weathering treatment were also monitored by leaching tests. At the end of the 12 weeks of treatment, almost all the considered samples resulted to be usable without restrictions in road construction with reference to the test parameter volume stability.« less

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization.

PubMed

Morales-Álvarez, Edwin D; Rivera-Hoyos, Claudia M; Cardozo-Bernal, Ángela M; Poutou-Piñales, Raúl A; Pedroza-Rodríguez, Aura M; Díaz-Rincón, Dennis J; Rodríguez-López, Alexander; Alméciga-Díaz, Carlos J; Cuervo-Patiño, Claudia L

2017-01-01

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZ α A- GlucPost -Stop in Pichia pastoris . Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL -1 at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a V max of 6.87 × 10 -5  mM s -1 , with an apparent K m of 5.36 × 10 -2  mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges.

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization

PubMed Central

Morales-Álvarez, Edwin D.; Rivera-Hoyos, Claudia M.; Cardozo-Bernal, Ángela M.; Pedroza-Rodríguez, Aura M.; Díaz-Rincón, Dennis J.; Rodríguez-López, Alexander; Alméciga-Díaz, Carlos J.; Cuervo-Patiño, Claudia L.

2017-01-01

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZαA-GlucPost-Stop in Pichia pastoris. Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL−1 at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a Vmax of 6.87 × 10−5 mM s−1, with an apparent Km of 5.36 × 10−2 mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges. PMID:28421142

Cost-effective alternative to nano-encapsulation: Amorphous curcumin-chitosan nanoparticle complex exhibiting high payload and supersaturation generation.

PubMed

Nguyen, Minh Hiep; Yu, Hong; Kiew, Tie Yi; Hadinoto, Kunn

2015-10-01

While the wide-ranging therapeutic activities of curcumin have been well established, its successful delivery to realize its true therapeutic potentials faces a major challenge due to its low oral bioavailability. Even though nano-encapsulation has been widely demonstrated to be effective in enhancing the bioavailability of curcumin, it is not without drawbacks (i.e. low payload and costly preparation). Herein we present a cost-effective bioavailability enhancement strategy of curcumin in the form of amorphous curcumin-chitosan nanoparticle complex (or curcumin nanoplex in short) exhibiting a high payload (>80%). The curcumin nanoplex was prepared by a simple yet highly efficient drug-polysaccharide complexation method that required only mixing of the curcumin and chitosan solutions under ambient condition. The effects of (1) pH and (2) charge ratio of chitosan to curcumin on the (i) physical characteristics of the nanoplex (i.e. size, colloidal stability and payload), (ii) complexation efficiency, and (iii) production yield were investigated from which the optimal preparation condition was determined. The nanoplex formation was found to favor low acidic pH and charge ratio below unity. At the optimal condition (i.e. pH 4.4. and charge ratio=0.8), stable curcumin nanoplex (≈260nm) was prepared at >90% complexation efficiency and ≈50% production yield. The amorphous state stability, colloidal stability, and in vitro non-cytotoxicity of the nanoplex were successfully established. The curcumin nanoplex produced prolonged supersaturation (3h) in the presence of hydroxypropyl methylcellulose (HPMC) at five times of the saturation solubility of curcumin. In addition, curcumin released from the nanoplex exhibited improved chemical stability owed to the presence of chitosan. Both results (i.e. high supersaturation and improved chemical stability) bode well for the ability of the curcumin nanoplex to enhance the bioavailability of curcumin clinically. Copyright © 2015 Elsevier B.V. All rights reserved.

TiO2 nanoparticles aggregation and disaggregation in presence of alginate and Suwannee River humic acids. pH and concentration effects on nanoparticle stability.

PubMed

Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

2013-10-15

The behavior of manufactured TiO2 nanoparticles is studied in a systematic way in presence of alginate and Suwannee River humic acids at variable concentrations. TiO2 nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO2 nanoparticles is discussed by considering three pH-dependent electrostatic scenarios. In the first scenario, when pH is below the TiO2 nanoparticle point of zero charge, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee River humic acids are negatively charged. Fast adsorption at the TiO2 nanoparticles occurs, promotes surface charge neutralization and aggregation. By increasing further alginate and Suwannee River humic acids concentrations charge inversion and stabilization of TiO2 nanoparticles are obtained. In the second electrostatic scenario, at the surface charge neutralization pH, TiO2 nanoparticles are rapidly forming aggregates. Adsorption of alginate and Suwannee River humic acids on aggregates leads to their partial fragmentation. In the third electrostatic scenario, when nanoparticles, alginate and Suwannee River humic acids are negatively charged, only a small amount of Suwannee River humic acids is adsorbed on TiO2 nanoparticles surface. It is found that the fate and behavior of individual and aggregated TiO2 nanoparticles in presence of environmental compounds are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions, steric and van der Waals interactions, as well as concentration ratio. Results also suggest that environmental aquatic concentration ranges of humic acids and biopolymers largely modify the stability of aggregated or dispersed TiO2 nanoparticles. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of pH on the functional properties of Arthrospira (Spirulina) platensis protein isolate.

PubMed

Benelhadj, Sonda; Gharsallaoui, Adem; Degraeve, Pascal; Attia, Hamadi; Ghorbel, Dorra

2016-03-01

In the present study, a protein isolate extracted from Arthrospira platensis by isoelectric precipitation was evaluated for its functional properties. The maximum nitrogen solubility was 59.6±0.7% (w/w) at pH 10. The A. platensis protein isolate (API) showed relatively high oil (252.7±0.3g oil/100g API) and water (428.8±15.4g of water/100g of API at pH 10) absorption capacities. The protein zeta potential, the emulsifying capacity, the emulsion ageing stability, the emulsion microstructure and the emulsion opacity as well as the foaming capacity and the foam stability were shown to be greatly affected by pH. Especially, emulsifying and foaming capacities were positively correlated to the protein solubility. Moreover, the API was able to form films when sorbitol (30% (w/w)) was used as plasticizer and to form gels when the API concentration exceeded 12% (w/w). Copyright © 2015 Elsevier Ltd. All rights reserved.

Physicochemical stability and inactivation of human and simian rotaviruses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Z.D.; Birch, C.; Heath, R.

1987-04-01

The effects of various physical and chemical treatments on the stability of a human serotype 1 rotavirus and simian agent 11 (SA11) were compared by using a fluorescence focus assay. The infectivity of both strains was retained after storage at room temperature for 14 days, 4 degree C for 22 days, and -20 degree C for 32 days; lyophilization; and treatment at pH 3 to 11. Both viruses were inactivated at pH 12, as was the human virus at pH 2, although this pH resulted in only partial inactivation of SA11. The human virus also appeared to be more sensitivemore » than SA11 to the action of ether and chloroform. The infectivity of both viruses was lost after UV irradiation for 15 min and after treatment with 8% formaldehyde for 5 min, 70% (vol/vol) ethanol for 30 min, and 2% lysol, 2% phenol, and 1% H/sub 2/O/sub 2/ for 1 h each.« less

Citrobacter amalonaticus Phytase on the Cell Surface of Pichia pastoris Exhibits High pH Stability as a Promising Potential Feed Supplement

PubMed Central

Li, Cheng; Lin, Ying; Huang, Yuanyuan; Liu, Xiaoxiao; Liang, Shuli

2014-01-01

Phytase expressed and anchored on the cell surface of Pichia pastoris avoids the expensive and time-consuming steps of protein purification and separation. Furthermore, yeast cells with anchored phytase can be used as a whole-cell biocatalyst. In this study, the phytase gene of Citrobacter amalonaticus was fused with the Pichia pastoris glycosylphosphatidylinositol (GPI)-anchored glycoprotein homologue GCW61. Phytase exposed on the cell surface exhibits a high activity of 6413.5 U/g, with an optimal temperature of 60°C. In contrast to secreted phytase, which has an optimal pH of 5.0, phytase presented on the cell surface is characterized by an optimal pH of 3.0. Moreover, our data demonstrate that phytase anchored on the cell surface exhibits higher pH stability than its secreted counterpart. Interestingly, our in vitro digestion experiments demonstrate that phytase attached to the cell surface is a more efficient enzyme than secreted phytase. PMID:25490768

Citrobacter amalonaticus phytase on the cell surface of Pichia pastoris exhibits high pH stability as a promising potential feed supplement.

PubMed

Li, Cheng; Lin, Ying; Huang, Yuanyuan; Liu, Xiaoxiao; Liang, Shuli

2014-01-01

Phytase expressed and anchored on the cell surface of Pichia pastoris avoids the expensive and time-consuming steps of protein purification and separation. Furthermore, yeast cells with anchored phytase can be used as a whole-cell biocatalyst. In this study, the phytase gene of Citrobacter amalonaticus was fused with the Pichia pastoris glycosylphosphatidylinositol (GPI)-anchored glycoprotein homologue GCW61. Phytase exposed on the cell surface exhibits a high activity of 6413.5 U/g, with an optimal temperature of 60°C. In contrast to secreted phytase, which has an optimal pH of 5.0, phytase presented on the cell surface is characterized by an optimal pH of 3.0. Moreover, our data demonstrate that phytase anchored on the cell surface exhibits higher pH stability than its secreted counterpart. Interestingly, our in vitro digestion experiments demonstrate that phytase attached to the cell surface is a more efficient enzyme than secreted phytase.

Production and Characterization of Lipases by Two New Isolates of Aspergillus through Solid-State and Submerged Fermentation

PubMed Central

Colla, Luciane Maria; Ficanha, Aline M. M.; Rizzardi, Juliana; Bertolin, Telma Elita; Reinehr, Christian Oliveira; Costa, Jorge Alberto Vieira

2015-01-01

Due to the numerous applications of lipases in industry, there is a need to study their characteristics, because lipases obtained from different sources may present different properties. The aim of this work was to accomplish the partial characterization of lipases obtained through submerged fermentation and solid-state fermentation by two species of Aspergillus. Fungal strains were isolated from a diesel-contaminated soil and selected as good lipases producers. Lipases obtained through submerged fermentation presented optimal activities at 37°C and pH 7.2 and those obtained through solid-state fermentation at 35°C and pH 6.0. The enzymes produced by submerged fermentation were more temperature-stable than those obtained by solid-state fermentation, presenting 72% of residual activity after one hour of exposition at 90°C. Lipases obtained through submerged fermentation had 80% of stability in acidic pH and those obtained through solid-state fermentation had stability greater than 60% in alkaline pH. PMID:26180809

Comperative study of catalase immobilization on chitosan, magnetic chitosan and chitosan-clay composite beads.

PubMed

Başak, Esra; Aydemir, Tülin; Dinçer, Ayşe; Becerik, Seda Çınar

2013-12-01

Catalase was immobilized on chitosan and modified chitosan. Studies were carried out on free-immobilized catalase concerning the determination of optimum temperature, pH, thermal, storage stability, reusability, and kinetic parameters. Optimum temperature and pH for free catalase and catalase immobilized were found as 35°C and 7.0, respectively. After 100 times of repeated tests, the immobilized catalases on chitosan-clay and magnetic chitosan maintain over 50% and 60% of the original activity, respectively. The ease of catalase immobilization on low-cost matrices and good stability upon immobilization in the present study make it a suitable product for further use in the food industry.

Effect of sonication on the colloidal stability of iron oxide nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sodipo, Bashiru Kayode; Aziz, Azlan Abdul

2015-04-24

Colloidal stability of superparamagnetic iron oxide nanoparticles’ (SPION) suspensions, ultrasonically irradiated at various pH was studied. Electrophoresis measurement of the sonicated SPION showed that the shock waves and other unique conditions generated from the acoustic cavitation process (formation, growth and collapse of bubbles) affect the zeta potential value of the suspension. In this work, stabled colloidal suspensions of SPION were prepared and their pH is varied between 3 and 5. Prior to ultrasonic irradiation of the suspensions, their initial zeta potential values were determined. After ultrasonic irradiation of the suspensions, we observed that the sonication process interacts with colloidal stabilitymore » of the nanoparticles. The results demonstrated that only suspensions with pH less 4 were found stable and able to retain more than 90% of its initial zeta potential value. However, at pH greater than 4, the suspensions were found unstable. The result implies that good zeta potential value of SPION can be sustained in sonochemical process as long as the pH of the mixture is kept below 4.« less

Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

NASA Astrophysics Data System (ADS)

Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

2015-12-01

A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl-]/[OH-] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete.

PubMed

Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

2015-12-17

A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl(-)]/[OH(-)] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

Degradation kinetics of chlorogenic acid at various pH values and effects of ascorbic acid and epigallocatechin gallate on its stability under alkaline conditions.

PubMed

Narita, Yusaku; Inouye, Kuniyo

2013-01-30

5-Caffeoylquinic acid (5-CQA) is generally referred to as chlorogenic acid and exhibits various biological activities such as antioxidant activity and porcine pancreas α-amylase inhibitory activities. 5-CQA may be useful as an antioxidant for food and to prevent diabetes and obesity. The degradation of 5-CQA and caffeic acid (CA) in an aqueous solution at 37 °C and pH 5.0-9.0 was studied. The degradation of 5-CQA and CA, demonstrating time and pH dependence (i.e., the rate constant, k, was higher at higher pH), was satisfactorily described by the Weibull equation. The stability of 5-CQA at pH 7.4 and 9.0 was improved by adding (-)-epigallocatechin gallate (EGCG) and ascorbic acid (AA). Moreover, the degradation of 5-CQA in the presence of EGCG or AA could be described by the Weibull equation. The k value in the presence of EGCG or AA was dependent on their concentration.

Degradation kinetics of anthocyanins from European cranberrybush (Viburnum opulus L.) fruit extracts. Effects of temperature, pH and storage solvent.

PubMed

Moldovan, Bianca; David, Luminiţa; Chişbora, Cristian; Cimpoiu, Claudia

2012-09-28

European cranberrybush (Viburnum opulus L.) fruits are well known for their biological properties, of which some are due to the presence of anthocyanins in the berries. Current literature provides little information concerning these fruits. The stability of anthocyanins from Viburnum opulus fruits, in aqueous and ethanolic extracts, stored under darkness for 7 days at different temperatures (2 °C, 37 °C and 75 °C) and pH values (pH = 3 and 7), was studied here. The lowest stability was showed by the anthocyanins from the water extract stored at 75 °C and pH = 7, with half-life and constant rate values of 1.98 h and 0.3488 h⁻¹, respectively. The results showed a good correlation between the total anthocyanin content (determined using the pH differential method) and the time of storage, with determination coefficients varying from R² = 0.9298 to R² = 0.9971. Results indicate that the storage degradation of anthocyanins followed first-order reaction kinetics under all investigated conditions.

Stabilized aqueous hydrogen peroxide solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malin, M.J.; Sciafani, L.D.

1988-05-17

This patent describes a stabilized aqueous hydrogen peroxide solution having a pH below 7 and an amount of Ferric ion up to about 2 ppm comprising hydrogen peroxide, acetanilide having a concentration which ranges between 0.74 M Mol/L and 2.22 mMol/L, and o-benzene disulfonic acid or salt thereof at a concentration between about 0.86 mMol/L to about 1.62 mMol/L.

Immobilization of Candida antarctica lipase B by adsorption to green coconut fiber.

PubMed

Brígida, Ana I S; Pinheiro, Alvaro D T; Ferreira, Andrea L O; Gonçalves, Luciana R B

2008-03-01

An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after 2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined. CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 degrees C, as half-lives (t (1/2)) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle. However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction.

Immobilization of Candida antarctica Lipase B by Adsorption to Green Coconut Fiber

NASA Astrophysics Data System (ADS)

Brígida, Ana I. S.; Pinheiro, Álvaro D. T.; Ferreira, Andrea L. O.; Gonçalves, Luciana R. B.

An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after 2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined. CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 °C, as half-lives (t 1/2) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle. However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction.

In Vitro Plasma Stability, Permeability and Solubility of Mercaptoacetamide Histone Deacetylase Inhibitors

PubMed Central

Konsoula, Roula; Jung, Mira

2008-01-01

Histone deacetylase inhibitors (HDACIs) are emerging as a new class of therapeutic agents with potent antitumor activities in a broad spectrum of human cancers. In this study, the in vitro plasma stability, permeability, solubility, and lipophilicity (logD) of two mercaptoacetamide-based HDACIs (coded as W2 and S2) were evaluated and compared to Vorinostat (SAHA). The results demonstrated that the compounds manifested high solubility in HCl (pH 1.2) but lower in PBS (pH 7.4) than SAHA. Moreover, mercaptoacetamide-based HDACIs exhibited higher lipophilicity values compared to SAHA. The permeability of these compounds was evaluated using the Caco-2 cell monolayer as a model of the intestinal mucosa. The Caco-2 studies revealed that the compounds S2 and W2 are highly permeable with apparent permeability coefficients (Papp) in the apical to basolateral direction of 7.33 × 10−6 and 15.0 × 10−6 cm/s, respectively. The in vitro stability was determined in human, mouse, porcine and rat plasma. Data showed that the compound W2 is more stable in human and rat plasma and the S2 is more stable in all plasma species than SAHA. Taken together, these results indicate that the mercaptoacetamide-based HDACIs possess favorable solubility, lipophilicity, permeability and plasma stability features. PMID:18562136

Design and introduction of a disulfide bridge in firefly luciferase: increase of thermostability and decrease of pH sensitivity.

PubMed

Imani, Mehdi; Hosseinkhani, Saman; Ahmadian, Shahin; Nazari, Mahboobeh

2010-08-01

The thermal sensitivity and pH-sensitive spectral properties of firefly luciferase have hampered its application in a variety of fields. It is proposed that the stability of a protein can be increased by introduction of disulfide bridge that decreases the configurational entropy of unfolding. A disulfide bridge is introduced into Photinus pyralis firefly luciferase to make two separate mutant enzymes with a single bridge. Even though the A103C/S121C mutant showed remarkable thermal stability, its specific activity decreased, whereas the A296C/A326C mutant showed tremendous thermal stability, relative pH insensitivity and 7.3-fold increase of specific activity. Moreover, the bioluminescence emission spectrum of A296C/A326C was resistant against higher temperatures (37 degrees C). Far-UV CD analysis showed slight secondary structure changes for both mutants. Thermal denaturation analysis showed that conformational stabilities of A103C/S121C and A296C/A326C are more than native firefly luciferase. It is proposed that since A296 and A326 are situated in the vicinity of the enzyme active site microenvironment in comparison with A103 and S121, the formation of a disulfide bridge in this region has more impact on enzyme kinetic characteristics.

Cloning and expression of a novel prolyl endopeptidase from Aspergillus oryzae and its application in beer stabilization.

PubMed

Kang, Chao; Yu, Xiao-Wei; Xu, Yan

2015-02-01

A novel prolyl endopeptidase gene from Aspergillus oryzae was cloned and expressed in Pichia pastoris. Amino acid sequence analysis of the prolyl endopeptidase from Aspergillus oryzae (AO-PEP) showed that this enzyme belongs to a class serine peptide S28 family. Expression, purification and characterization of AO-PEP were analyzed. The optimum pH and temperature were pH 5.0 and 40 °C, respectively. The enzyme was activated and stabilized by metal ion Ca(2+) and inhibited by Zn(2+), Mn(2+), Al(3+), and Cu(2+). The K m and k cat values of the purified enzyme for different substrates were evaluated. The results implied that the recombinant AO-PEP possessed higher affinity for the larger substrate. A fed-batch strategy was developed for the high-cell-density fermentation and the enzyme activity reached 1,130 U/l after cultivation in 7 l fermentor. After addition of AO-PEP during the fermentation phase of beer brewing, demonstrated the potential application of AO-PEP in the non-biological stability of beer, which favor further industrial development of this new enzyme in beer stabilization, due to its reducing operational costs, as well as no beer losses unlike regeneration process and beer lost with regenerated polyvinylpolypyrrolidone system.

On the pH of Aqueous Attoliter-Volume Droplets

NASA Astrophysics Data System (ADS)

Ramos, Kieran P.; Velpula, Samson S.; Demille, Trevor B.; Pajela, Ryan; Goldner, Lori S.

Droplets of water dispersed in perfluorinated liquids have widespread use including microfluidics, drug delivery and single-molecule measurements. Perfluorinated liquids are distinctly biocompatible due to their stability, low surface tension, lipophobicity, and hydrophobicity. For this reason, the effect of the perfluorinated surface on droplet contents is usually ignored. However, as the droplet diameter is reduced, we expect that any effect of the water/oil interface on droplet contents will become more obvious. We studied the pH of attoliter-volume aqueous droplets in perfluorinated liquids using pH-sensing fluorescent dyes. Droplets were prepared either by sonication or extrusion from buffer and perfluorinated liquids (FC40 or FC77). A non-ionic surfactant was used to stabilize the droplets. Buffer strength, ionic strength, and pH of the aqueous phase were varied and resulting droplet pH compared to the pH of the buffer from which they were formed. Preliminary data are consistent with a pH in droplets that depends on the concentration of non-ionic surfactant. At low surfactant concentrations, the pH in droplets is distinctly lower than the stock buffer. However, as the concentration of non-ionic surfactant is increased the change in pH decreases. This work was funded by NSF/DBI-1152386.

Molecular Docking of Potential Inhibitors of Broccoli Myrosinase.

PubMed

Román, J; Castillo, A; Mahn, A

2018-05-30

Glucosinolates are secondary metabolites occurring in Brassicaceae plants whose hydrolysis may yield isothiocyanates, widely recognized as health-promoting compounds. Myrosinase catalyzes this conversion. The chemical mechanism involves an unstable intermediary (thiohydroxamate- O -sulfonate) that spontaneously decomposes into isothiocyanates or other non-bioactive compounds depending on pH and cofactors. At acidic pH, non-bioactive compounds such as nitriles and thiocyanates are formed, while at neutral pH isothiocyanates are obtained. Broccoli myrosinase has been poorly studied so far. Recently, its amino acidic sequence was elucidated, and a structural model was built. The aim of this work was to study the molecular interaction of broccoli myrosinase with different ligands at acidic pH to propose possible inhibitors that prevent formation of undesirable compounds at acidic pH, and that at neutral pH dissociate from the enzyme, allowing formation of isothiocyanates. The interaction between broccoli myrosinase and 40 ligands was studied by molecular docking simulations. Both the enzyme and each inhibitor were set at pH 3.0. Amygdaline and arbutin showed the highest affinity to broccoli myrosinase in this condition. The residues that stabilize the complexes agree with those that stabilize the substrate (Gln207, Glu429, Tyr352, and Ser433). Accordingly, amygdaline and arbutin would perform as competitive inhibitors of myrosinase at pH 3.0.

Multilayer biomimetics: reversible covalent stabilization of a nanostructured biofilm.

PubMed

Li, Bingyun; Haynie, Donald T

2004-01-01

Designed polypeptides and electrostatic layer-by-layer self-assembly form the basis of promising research in bionanotechnology and medicine on development of polyelectrolyte multilayer films (PEMs). We show that PEMs can be formed from oppositely charged 32mers containing several cysteine residues. The polypeptides in PEMs become cross-linked under mild oxidizing conditions. This mimicking of disulfide (S-S) bond stabilization of folded protein structure confers on the PEMs a marked increase in resistance to film disassembly at acidic pH. The reversibility of S-S bond stabilization of PEMs presents further advantages for controlling physical properties of films, coatings, and other applications involving PEMs.

Rheology of interfacial protein-polysaccharide composites

NASA Astrophysics Data System (ADS)

Fischer, P.

2013-05-01

The morphology and mechanical properties of protein adsorption layers can significantly be altered by the presence of surfactants, lipids, particles, other proteins, and polysaccharides. In food emulsions, polysaccharides are primarily considered as bulk thickener but can under appropriate environmental conditions stabilize or destabilize the protein adsorption layer and, thus, the entire emulsion system. Despite their ubiquitous usage as stabilization agent, relatively few investigations focus on the interfacial rheology of composite protein/polysaccharide adsorption layers. The manuscript provides a brief review on both main stabilization mechanisms, thermodynamic phase separation and electrostatic interaction and discusses the rheological response in light of the environmental conditions such as ionic strength and pH.

Effects of pH and cation adsorption on colloidal stability of graphene oxide in aquatic environments

NASA Astrophysics Data System (ADS)

Terracciano, Amalia

The presented doctoral research aims to improve the current understanding of the chemistry of Graphene Oxide Nanoparticles (GONPs) in common water systems. The widespread demand and future use of this nanomaterial in a broad range of different applications (i.e. biomedical, electronic, environmental) will certainly lead to its release in the environment with consequent exposure of ecosystems to graphene oxide (GO) toxicity. The described scenario demand a careful investigation and deep understanding of the environmental behavior and fate of GONPs, especially in water systems. Therefore this study focused on the investigation the effects of pH some of the most common water electrolytes (monovalent and divalent) and on GO colloidal stability. The interactions between the selected ions and the GO functional groups was also studied. The mobility of GO in porous media was first studied through filtrations tests that determine influence of ionic strength (IS) and solution composition on GO mobility. The GONPs showed to be completely retained in the porous media in presence of 3.5 mM of CaCl2 and in tap water while no retention was found for 10 mM of NaCl solution. The results indicated significant impact of divalent cations on the mobility of GO. Serial experiments were performed to quantify the adsorption of several cations (Na+, Ca2+ and Ba2+) on GO. The divalent cations showed to be strongly adsorbed on the GO surface with increasing pH and cation concentrations, while no significant sodium adsorption was detected. Raman spectroscopy and XPS analysis also showed strong differences in the typical spectra of GO, before and after adsorption of Ca2+ and Ba2+ which suggest chemical bond formation with the GO functional groups. The aggregation regime and the colloidal stability of the GO suspension in presence of selected electrolytes (Na+, Mg2+, Ca2+ and Ba2+) as function of pH was also extensively studied. The zeta potential, which is index of the stability of a colloidal suspension, was found to became more negative for GO in NaCl solutions for solution pH from 4 to 10 which is due to increased deprotonation of carboxyl (-COOH) and hydroxyl (-COH) groups on GO. Values of the zeta potential higher than +/-30 indicated increase stability of the colloidal suspension; however in presence of Ca2+ in solution, the zeta potential of GONPs become less negative (>-10 mV) with formation of aggregates which can be attributed to increased Ca2+ adsorption, especially at high pH. The increase adsorption will neutralize the negative surface charge to reduce electrostatic repulsion and promote aggregation. The same trend was found in presence of Ba2+ in solution. The critical coagulation concentration (CCC) of GO also showed to be strongly affected by Ca2+ and pH. The CCC value of GO remained at about 48 mM NaCl with increasing pH from 4.4 to 7 while it dramatically decreased from about 1.7 to 0.3 mM in CaCl2 solution with increasing pH. The results of this study suggest that pH and divalent cations, especially Ca2+ could significantly affect the colloidal stability of GONPs and therefore influence their mobility in the environment. Moreover the interactions between Ca2+ and Ba2+ and the GO nanosheets showed to be particularly strong which suggest inner-sphere complexation formation. The findings obtained from this doctoral research will contribute in improving the understanding of the fate and transport of the GONPs in aquatic environments and to develop more suitable models to predict its behavior.

Stability of nitroglycerin in intravenous admixtures.

PubMed

Klamerus, K J; Ueda, C T; Newton, D W

1984-02-01

The stability of nitroglycerin in intravenous admixtures was studied. Admixtures containing nitroglycerin 400 micrograms/ml and each of seven injectable drugs in concentrations used clinically were prepared in triplicate in 5% dextrose and 0.9% sodium chloride injections. Admixtures were stored in glass bottles at room temperature for 24 hours in the upright position and then for 24 hours in the inverted position to ensure contact of the solution with the rubber stopper of the container. At 0, 24, and 48 hours, samples of each admixture were assayed by high-performance liquid chromatography for nitroglycerin concentration. The pH of one randomly chosen bottle of each admixture was measured at 0, 24, and 48 hours. A significant loss of nitroglycerin potency at 48 hours was observed only in admixtures containing phenytoin; in these solutions, a 9% decrease in initial nitroglycerin concentration was noted. Phenytoin crystallization was present in all phenytoin admixtures by 24 hours. Compared with initial values, no significant differences in the pH values of any admixture samples assayed at 24 and 48 hours were noted; however, admixtures containing phenytoin had the most alkaline pH values. Under the conditions studied, nitroglycerin concentrations remained above 90% of their initial values for 48 hours in all tested admixtures; however, phenytoin crystallization limits the stability of phenytoin admixtures.

Silver colloidal nanoparticle stability: influence on Candida biofilms formed on denture acrylic.

PubMed

Monteiro, Douglas Roberto; Takamiya, Aline Satie; Feresin, Leonardo Perina; Gorup, Luiz Fernando; de Camargo, Emerson Rodrigues; Delbem, Alberto Carlos Botazzo; Henriques, Mariana; Barbosa, Debora Barros

2014-08-01

Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) influences their efficacy against Candida albicans and C. glabrata biofilms. Several parameters of SN stability were tested, namely, temperature (50ºC, 70ºC, and 100ºC), pH (5.0 and 9.0), and time of contact (5 h and 24 h) with biofilms. The control was defined as SNs without temperature treatment, pH 7, and 24 h of contact. These colloidal suspensions at 54 mg/L were used to treat mature Candida biofilms (48 h) formed on acrylic. Their efficacy was determined by total biomass and colony-forming unit quantification. Data were analyzed using analysis of variance and the Bonferroni post hoc test (α = 0.05). The temperature and pH variations of SNs did not affect their efficacy against the viable cells of Candida biofilms (P > 0.05). Moreover, the treatment periods were not decisive in terms of the susceptibility of Candida biofilms to SNs. These findings provide an important advantage of SNs that may be useful in the treatment of Candida-associated denture stomatitis. © The Author 2014. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Rational Development of Neutral Aqueous Electrolytes for Zinc-Air Batteries.

PubMed

Clark, Simon; Latz, Arnulf; Horstmann, Birger

2017-12-08

Neutral aqueous electrolytes have been shown to extend both the calendar life and cycling stability of secondary zinc-air batteries (ZABs). Despite this promise, there are currently no modeling studies investigating the performance of neutral ZABs. Traditional continuum models are numerically insufficient to simulate the dynamic behavior of these complex systems because of the rapid, orders-of-magnitude concentration shifts that occur. In this work, we present a novel framework for modeling the cell-level performance of pH-buffered aqueous electrolytes. We apply our model to conduct the first continuum-scale simulation of secondary ZABs using aqueous ZnCl 2 -NH 4 Cl as electrolyte. We first use our model to interpret the results of two recent experimental studies of neutral ZABs, showing that the stability of the pH value is a significant factor in cell performance. We then optimize the composition of the electrolyte and the design of the cell considering factors including pH stability, final discharge product, and overall energy density. Our simulations predict that the effectiveness of the pH buffer is limited by slow mass transport and that chlorine-containing solids may precipitate in addition to ZnO. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Norovirus-like VP1 particles exhibit isolate dependent stability profiles

NASA Astrophysics Data System (ADS)

Pogan, Ronja; Schneider, Carola; Reimer, Rudolph; Hansman, Grant; Uetrecht, Charlotte

2018-02-01

Noroviruses are the main cause of viral gastroenteritis with new variants emerging frequently. There are three norovirus genogroups infecting humans. These genogroups are divided based on the sequence of their major capsid protein, which is able to form virus-like particles (VLPs) when expressed recombinantly. VLPs of the prototypical GI.1 Norwalk virus are known to disassemble into specific capsid protein oligomers upon alkaline treatment. Here, native mass spectrometry and electron microscopy on variants of GI.1 and of GII.17 were performed, revealing differences in terms of stability between these groups. Beyond that, these experiments indicate differences even between variants within a genotype. The capsid stability was monitored in different ammonium acetate solutions varying both in ionic strength and pH. The investigated GI.1 West Chester isolate showed comparable disassembly profiles to the previously studied GI.1 Norwalk virus isolate. However, differences were observed with the West Chester being more sensitive to alkaline pH. In stark contrast to that, capsids of the variant belonging to the currently prevalent genogroup GII were stable in all tested conditions. Both variants formed smaller capsid particles already at neutral pH. Certain amino acid substitutions in the S domain of West Chester relative to the Norwalk virus potentially result in the formation of these T  =  1 capsids.

HPLC & NMR-based forced degradation studies of ifosfamide: The potential of NMR in stability studies.

PubMed

Salman, D; Peron, J-M R; Goronga, T; Barton, S; Swinden, J; Nabhani-Gebara, S

2016-03-01

The aim of this study is to conduct a forced degradation study on ifosfamide under several stress conditions to investigate the robustness of the developed HPLC method. It also aims to provide further insight into the stability of ifosfamide and its degradation profile using both HPLC and NMR. Ifosfamide solutions (20mg/mL; n=15, 20mL) were stressed in triplicate by heating (70°C), under acidic (pH 1 & 4) and alkaline (pH 10 & 12) conditions. Samples were analysed periodically using HPLC and FT-NMR. Ifosfamide was most stable under weakly acidic conditions (pH 4). NMR results suggested that the mechanism of ifosfamide degradation involves the cleavage of the PN bond. For all stress conditions, HPLC was not able to detect ifosfamide degradation products that were detected by NMR. These results suggest that the developed HPLC method for ifosfamide did not detect the degradation products shown by NMR. It is possible that degradation products co-elute with ifosfamide, do not elute altogether or are not amenable to the detection method employed. Therefore, investigation of ifosfamide stability requires additional techniques that do not suffer from the aforementioned shortcomings. Copyright © 2015 Académie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

Formation and stabilization of nanoemulsion-based vitamin E delivery systems using natural biopolymers: Whey protein isolate and gum arabic.

PubMed

Ozturk, Bengu; Argin, Sanem; Ozilgen, Mustafa; McClements, David Julian

2015-12-01

Natural biopolymers, whey protein isolate (WPI) and gum arabic (GA), were used to fabricate emulsion-based delivery systems for vitamin E-acetate. Stable delivery systems could be formed when vitamin E-acetate was mixed with sufficient orange oil prior to high pressure homogenization. WPI (d32=0.11 μm, 1% emulsifier) was better than GA (d32=0.38 μm, 10% emulsifier) at producing small droplets at low emulsifier concentrations. However, WPI-stabilized nanoemulsions were unstable to flocculation near the protein isoelectric point (pH 5.0), at high ionic strength (>100mM), and at elevated temperatures (>60 °C), whereas GA-stabilized emulsions were stable. This difference was attributed to differences in emulsifier stabilization mechanisms: WPI by electrostatic repulsion; GA by steric repulsion. These results provide useful information about the emulsifying and stabilizing capacities of natural biopolymers for forming food-grade vitamin-enriched delivery systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

Enhancement of colour stability of anthocyanins in model beverages by gum arabic addition.

PubMed

Chung, Cheryl; Rojanasasithara, Thananunt; Mutilangi, William; McClements, David Julian

2016-06-15

This study investigated the potential of gum arabic to improve the stability of anthocyanins that are used in commercial beverages as natural colourants. The degradation of purple carrot anthocyanin in model beverage systems (pH 3.0) containing L-ascorbic acid proceeded with a first-order reaction rate during storage (40 °C for 5 days in light). The addition of gum arabic (0.05-5.0%) significantly enhanced the colour stability of anthocyanin, with the most stable systems observed at intermediate levels (1.5%). A further increase in concentration (>1.5%) reduced its efficacy due to a change in the conformation of the gum arabic molecules that hindered their exposure to the anthocyanins. Fluorescence quenching measurements showed that the anthocyanin could have interacted with the glycoprotein fractions of the gum arabic through hydrogen bonding, resulting in enhanced stability. Overall, this study provides valuable information about enhancing the stability of anthocyanins in beverage systems using natural ingredients. Copyright © 2016 Elsevier Ltd. All rights reserved.

Study of Water-Oil Emulsion Breaking by Stabilized Solution Consisting of Anionic Surface Acting Agent - Soda Ash - Polymer (ASP)

NASA Astrophysics Data System (ADS)

Kulichkov, S. V.; Avtomonov, E. G.; Andreeva, L. V.; Solomennik, S. F.; Nikitina, A. V.

2018-01-01

The paper provides a laboratory research of breaking natural water-oil emulsions: - by non-stabilized ASP; by stabilized ASP; by mixture of stabilized and non-stabilized ASP in different proportions and production of refinery water of the required quality with the use of IronGuard 2495 as flocculant. Oil-in-water emulsion is stable. Classic methods are not suitable for residual water treatment: sediment gravity flow; filtration; centrifuge test. Microemulsion formed after ASP application has low boundary tension and high pH. It contributes to transfer of oil phase into a water one, forming oil-in-water emulsion. Alkaline condition has adverse effect on demulsifying ability of agents, flocculation and boundary tension. For breaking of water-oil emulsion at EBU before the interchanger water or water-oil emulsion from the wells that were not APS-treated in ratio of 1:9 shall be delivered. Residual water after EBU must be prepared in water tanks by dilution in great volume.

Stabilization of polymer lipid complexes prepared with lipids of lactic acid bacteria upon preservation and internalization into eukaryotic cells.

PubMed

Alves, P; Hugo, A A; Szymanowski, F; Tymczyszyn, E E; Pérez, P F; Coelho, J F J; Simões, P N; Gómez-Zavaglia, A

2014-11-01

The physicochemical characterization of polymer liposome complexes (PLCs) prepared with lipids of lactic acid bacteria and poly(N,N-dimethylaminoethyl methacrylate) covalently bound to cholesterol (CHO-PDMAEMA) was carried out in an integrated approach, including their stability upon preservation and incorporation into eukaryotic cells. PLCs were prepared with different polymer:lipid molar ratios (0, 0.05 and 0.10). Zeta potential, particle size distribution and polydispersity index were determined. The optimal polymer:lipid ratio and the stability of both bare liposomes and PLCs were evaluated at 37 °C and at different pHs, as well as after storage at 4 °C, -80 °C and freeze-drying in the presence or absence of trehalose 250 mM. Internalization of PLCs by eukaryotic cells was assessed to give a complete picture of the system. Incorporation of CHO-PDMAEMA onto bacterial lipids (ratio 0.05 and 0.10) led to stabilization at 37 °C and pH 7. A slight decrease of pH led to their strong destabilization. Bacteria PLCs showed to be more stable than lecithin (LEC) PLCs (used for comparison) upon preservation at 4 and -80 °C. The harmful nature of the preservation processes led to a strong decrease in the stability of PLCs, bacterial formulations being more stable than LEC PLCs. The addition of trehalose to the suspension of liposomes stabilized LEC PLC and did not have effect on bacterial PLCs. In vitro studies on Raw 264.7 and Caco-2/TC7 cells demonstrated an efficient incorporation of PLCs into the cells. Preparations with higher stability were the ones that showed a better cell-uptake. The nature of the lipid composition is determinant for the stability of PLCs. Lipids from lactic acid bacteria are composed of glycolipids and phospholipids like cardiolipin and phosphatidylglycerol. The presence of negatively charged lipids strongly improves the interaction with the positively charged CHO-PDMAEMA, thus stabilizing liposomes. In addition, glycolipids and phosphatidylglycerol act as intrinsic protectants of PLCs upon preservation. This particular lipid composition of lactic acid bacteria makes them natural formulations potentially useful as drug delivery systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of pH on structure, function, and stability of mitochondrial carbonic anhydrase VA.

PubMed

Idrees, Danish; Shahbaaz, Mohd; Bisetty, Krishna; Islam, Asimul; Ahmad, Faizan; Hassan, Md Imtaiyaz

2017-02-01

Mitochondrial carbonic anhydrase VA (CAVA) catalyzes the hydration of carbon dioxide to produce proton and bicarbonate which is primarily expressed in the mitochondrial matrix of liver, and involved in numerous physiological processes including lipogenesis, insulin secretion from pancreatic cells, ureagenesis, gluconeogenesis, and neuronal transmission. To understand the effect of pH on the structure, function, and stability of CAVA, we employed spectroscopic techniques such as circular dichroism, fluorescence, and absorbance measurements in wide range of pH (from pH 2.0 to pH 11.5). CAVA showed an aggregation at acidic pH range from pH 2.0 to pH 5.0. However, it remains stable and maintains its secondary structure in the pH range, pH 7.0-pH 11.5. Furthermore, this enzyme has an appreciable activity at more than pH 7.0 (7.0 < pH ≤ 11.5) with maximum activity at pH 9.0. The maximal values of k cat and k cat /K m at pH 9.0 are 3.7 × 10 6  s -1 and 5.5 × 10 7  M -1  s -1 , respectively. However, this enzyme loses its activity in the acidic pH range. We further performed 20-ns molecular dynamics simulation of CAVA to see the dynamics at different pH values. An excellent agreement was observed between in silico and in vitro studies. This study provides an insight into the activity of CAVA in the pH range of subcellular environment.

Superparamagnetic iron oxide nanoparticles incorporated into silica nanoparticles by inelastic collision via ultrasonic field: Role of colloidal stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sodipo, Bashiru Kayode; Azlan, Abdul Aziz; Innovation

2015-04-24

Superparamagnetic iron oxide nanoparticles (SPION)/Silica composite nanoparticles were prepared by ultrasonically irradiating colloidal suspension of silica and SPION mixture. Both silica and SPION were synthesized independently via co-precipitation and sol-gel method, respectively. Their mixtures were sonicated at different pH between 3 and 5. Electrophoresis measurement and other physicochemical analyses of the products demonstrate that at lower pH SPION was found incorporated into the silica. However, at pH greater than 4, SPION was unstable and unable to withstand the turbulence flow and shock wave from the ultrasonic field. Results suggest that the formation of the SPION/silica composite nanoparticles is strongly relatedmore » to the inelastic collision induced by ultrasonic irradiation. More so, the formation the composite nanoparticles via the ultrasonic field are dependent on the zeta potential and colloidal stability of the particles.« less

Physical Instability of a Therapeutic Fc Fusion Protein: Domain Contributions to Conformational and Colloidal Stability†

PubMed Central

Fast, Jonas L; Cordes, Amanda A; Carpenter, John F; Randolph, Theodore W

2009-01-01

Protein therapeutics made up of artificially combined proteins or protein domains, so called fusion proteins, are a novel and growing class of biopharmaceuticals. We have studied abatacept (Orencia®), a fusion protein that is constructed of a modified IgG Fc domain and the soluble part of the T-cell receptor CTLA-4. In accelerated degradation studies conducted at at 40 °C, a pH shift from 7.5 to 6.0 yields significantly faster aggregation kinetics, as measured by size-exclusion chromatography. To understand how the fusion domains and their interactions contribute to this result, we considered aggregation in light of the modified Lumry-Eyring reaction pathway. Protein conformational stabilities against chaotropes and temperature were measured. The structural consequences of these perturbations were observed by a variety of experimental techniques, including differential scanning calorimetry, circular dichroism, and intrinsic fluorescence. Abatacept’s colloidal stability was studied by measuring zeta potentials and osmotic second virial coefficients, as well as by modeling electrostatic potentials on the protein’s surface. The domains of abatacept exhibit different conformational stabilities that are highly pH dependent, whereas abatacept was weakly colloidally unstable at pH 6 or pH 7.5. These results are ascribed to conformational instability of the CTLA-4 and CH2 domains, which unfold to form a molten globule-like structure that is aggregation-prone. We suggest the instability against aggregation is determined by the least stable domains. PMID:19899812

Efficiency and protective effect of encapsulation of milk immunoglobulin G in multiple emulsion.

PubMed

Chen, C C; Tu, Y Y; Chang, H M

1999-02-01

Milk immunoglobulin G (IgG), separated with protein G affinity chromatography, and IgG in colostral whey were encapsulated by 0.5% (w/v) of Tween 80, sucrose stearate, or soy protein, which were used as secondary emulsifiers in the water in oil in water type multiple emulsion. The residual contents of separated IgG and IgG in colostral whey, ranging from 58.7 to 49.7% and from 13.2 to 21.3%, respectively, in the inner water phase (water phase surrounded by oil phase) with emulsifiers were determined by ELISA. However, the emulsion stability decreased after 24 h, and the residual IgG content in the inner water phase was lowered. Encapsulation of IgG in the multiple emulsion increased the stability of separated IgG against acid (pH 2.0) and alkali (pH 12.0) by 21-56% and 33-62%, respectively, depending on the emulsifier used. Moreover, multiple emulsion also provided a remarkable protective effect on separated IgG stability against proteases. The residual contents of separated IgG in multiple emulsion, using Tween 80 as secondary emulsifier, incubated for 2 h with pepsin (pH 2.0) and trypsin and chymotrypsin (pH 7.6) (enzyme/substrate = 1/20) were 35.4, 72.5, and 82.3%, whereas those of separated IgG in enzyme solution were only 7.2, 33. 1, and 35.2%, respectively. However, the separated IgG loss during the preparation of multiple emulsion was almost 41-50%.

Heat resistance of Bacillus cereus spores: effects of milk constituents and stabilizing additives.

PubMed

Mazas, M; López, M; Martínez, S; Bernardo, A; Martin, R

1999-04-01

Heat resistance of Bacillus cereus spores (ATCC 7004, 4342, and 9818) heated in different types of milk (skim, whole, and concentrated skim milk), skim milk containing stabilizing additives (sodium citrate, monopotassium phosphate, or disodium phosphate, 0.1%), and cream was investigated. Thermal resistance experiments were performed at temperatures within the range of 92 to 115 degrees C under continuous monitoring of pH. For strain 4342 no significant differences (P < 0.05) in D values were detected in any case. For strains 7004 and 9818 higher D values of about 20% were obtained in whole and concentrated skim milk than those calculated in skim milk. From all stabilizing additives tested, only sodium citrate and sodium phosphate increased the heat resistance for strain 9818. However, when the menstruum pH was measured at the treatment temperature, different pH values were found between the heating media. The differences in heat resistance observed could be due to a pH effect rather than to the difference in the substrates in which spores were heated. In contrast, when cream (fat content 20%) was used, lower D values were obtained, especially for strains 7004 and 9818. z values were not significantly modified by the milk composition, with an average z value of 7.95+/-0.20 degrees C for strain 7004, 7.88+/-0.10 degrees C for strain 4342, and 9.13+/-0.16 degrees C for strain 9818.

Close relationship of a novel Flavobacteriaceae α-amylase with archaeal α-amylases and good potentials for industrial applications

PubMed Central

2014-01-01

Background Bioethanol production from various starchy materials has received much attention in recent years. α-Amylases are key enzymes in the bioconversion process of starchy biomass to biofuels, food or other products. The properties of thermostability, pH stability, and Ca-independency are important in the development of such fermentation process. Results A novel Flavobacteriaceae Sinomicrobium α-amylase (FSA) was identified and characterized from genomic analysis of a novel Flavobacteriaceae species. It is closely related with archaeal α-amylases in the GH13_7 subfamily, but is evolutionary distant with other bacterial α-amylases. Based on the conserved sequence alignment and homology modeling, with minor variation, the Zn2+- and Ca2+-binding sites of FSA were predicated to be the same as those of the archaeal thermophilic α-amylases. The recombinant α-amylase was highly expressed and biochemically characterized. It showed optimum activity at pH 6.0, high enzyme stability at pH 6.0 to 11.0, but weak thermostability. A disulfide bond was introduced by site-directed mutagenesis in domain C and resulted in the apparent improvement of the enzyme activity at high temperature and broad pH range. Moreover, about 50% of the enzyme activity was detected under 100°C condition, whereas no activity was observed for the wild type enzyme. Its thermostability was also enhanced to some extent, with the half-life time increasing from 25 to 55 minutes at 50°C. In addition, after the introduction of the disulfide bond, the protein became a Ca-independent enzyme. Conclusions The improved stability of FSA suggested that the domain C contributes to the overall stability of the enzyme under extreme conditions. In addition, successfully directed modification and special evolutionary status of FSA imply its directional reconstruction potentials for bioethanol production, as well as for other industrial applications. PMID:24485248

An oxidant- and solvent-stable protease produced by Bacillus cereus SV1: application in the deproteinization of shrimp wastes and as a laundry detergent additive.

PubMed

Manni, Laila; Jellouli, Kemel; Ghorbel-Bellaaj, Olfa; Agrebi, Rym; Haddar, Anissa; Sellami-Kamoun, Alya; Nasri, Moncef

2010-04-01

The current increase in amount of shrimp wastes produced by the shrimp industry has led to the need in finding new methods for shrimp wastes disposal. In this study, an extracellular organic solvent- and oxidant-stable metalloprotease was produced by Bacillus cereus SV1. Maximum protease activity (5,900 U/mL) was obtained when the strain was grown in medium containing 40 g/L shrimp wastes powder as a sole carbon source. The optimum pH, optimum temperature, pH stability, and thermal stability of the crude enzyme preparation were pH 8.0, 60 degrees C, pH 6-9.5, and <55 degrees C, respectively. The crude protease was extremely stable toward several organic solvents. No loss of activity was observed even after 60 days of incubation at 30 degrees C in the presence of 50% (v/v) dimethyl sulfoxide and ethyl ether; the enzyme retained more than 70% of its original activity in the presence of ethanol and N,N-dimethylformamide. The protease showed high stability toward anionic (SDS) and non-ionic (Tween 80, Tween 20, and Triton X-100) surfactants. Interestingly, the activity of the enzyme was significantly enhanced by oxidizing agents. In addition, the enzyme showed excellent compatibility with some commercial liquid detergents. The protease of B. cereus SV1, produced under the optimal culture conditions, was tested for shrimp waste deproteinization in the preparation of chitin. The protein removal with a ratio E/S of 20 was about 88%. The novelties of the SV1 protease include its high stability to organic solvents and surfactants. These unique properties make it an ideal choice for application in detergent formulations and enzymatic peptide synthesis. In addition, the enzyme may find potential applications in the deproteinization of shrimp wastes to produce chitin.

Close relationship of a novel Flavobacteriaceae α-amylase with archaeal α-amylases and good potentials for industrial applications.

PubMed

Li, Chunfang; Du, Miaofen; Cheng, Bin; Wang, Lushan; Liu, Xinqiang; Ma, Cuiqing; Yang, Chunyu; Xu, Ping

2014-01-31

Bioethanol production from various starchy materials has received much attention in recent years. α-Amylases are key enzymes in the bioconversion process of starchy biomass to biofuels, food or other products. The properties of thermostability, pH stability, and Ca-independency are important in the development of such fermentation process. A novel Flavobacteriaceae Sinomicrobium α-amylase (FSA) was identified and characterized from genomic analysis of a novel Flavobacteriaceae species. It is closely related with archaeal α-amylases in the GH13_7 subfamily, but is evolutionary distant with other bacterial α-amylases. Based on the conserved sequence alignment and homology modeling, with minor variation, the Zn2+- and Ca2+-binding sites of FSA were predicated to be the same as those of the archaeal thermophilic α-amylases. The recombinant α-amylase was highly expressed and biochemically characterized. It showed optimum activity at pH 6.0, high enzyme stability at pH 6.0 to 11.0, but weak thermostability. A disulfide bond was introduced by site-directed mutagenesis in domain C and resulted in the apparent improvement of the enzyme activity at high temperature and broad pH range. Moreover, about 50% of the enzyme activity was detected under 100°C condition, whereas no activity was observed for the wild type enzyme. Its thermostability was also enhanced to some extent, with the half-life time increasing from 25 to 55 minutes at 50°C. In addition, after the introduction of the disulfide bond, the protein became a Ca-independent enzyme. The improved stability of FSA suggested that the domain C contributes to the overall stability of the enzyme under extreme conditions. In addition, successfully directed modification and special evolutionary status of FSA imply its directional reconstruction potentials for bioethanol production, as well as for other industrial applications.

Marburg Virus Glycoprotein GP2: pH-Dependent Stability of the Ectodomain α-Helical Bundle†

PubMed Central

Harrison, Joseph S.; Koellhoffer, Jayne F.; Chandran, Kartik; Lai, Jonathan R.

2012-01-01

Marburg virus (MARV) and Ebola virus (EBOV) constitute the family Filoviridae of enveloped viruses (filoviruses) that cause severe hemorrhagic fever. Infection by MARV is required for fusion between the host cell and viral membranes, a process that is mediated by the two subunits of the envelope glycoprotein GP1 (surface subunit) and GP2 (transmembrane subunit). Upon viral attachment and uptake, it is believed that the MARV viral fusion machinery is triggered by host factors and environmental conditions found in the endosome. Next, conformational rearrangements in the GP2 ectodomain result in the formation of a highly stable six-helix bundle; this refolding event provides the energetic driving force for membrane fusion. Both GP1 and GP2 from EBOV have been extensively studied, but there is little information available for the MARV glycoproteins. Here we have expressed two variants of the MARV GP2 ectodomain in Escherichia coli and analyzed their biophysical properties. Circular dichroism indicates that the MARV GP2 ectodomain adopts an α-helical conformation, and one variant sediments as a trimer by equilibrium analytical ultracentrifugation. Denaturation studies indicate the α-helical structure is highly stable at pH 5.3 (unfolding energy, ΔGunf H2O, of 33.4 ± 2.5 kcal/mol and melting temperature, Tm, of 75.3 ± 2.1 °C for one variant). Furthermore, we found the α-helical stability to be strongly dependent on pH with higher stability under lower pH conditions (Tm values ranging from ~92 °C at pH 4.0 to ~38 °C at pH 8.0). Mutational analysis suggests two glutamic acid residues (E579 and E580) are partially responsible for this pH-dependent behavior. Based on these results, we hypothesize that pH-dependent folding stability of the MARV GP2 ectodomain provides a mechanism to control conformational preferences such that the six-helix bundle ‘post-fusion’ state is preferred under conditions of appropriately matured endosomes. PMID:22369502

Investigation of the polyvinyl alcohol stabilization mechanism and adsorption properties on the surface of ternary mixed nanooxide AST 50 (Al2O3-SiO2-TiO2)

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Ostolska, Iwona; Szewczuk-Karpisz, Katarzyna; Chibowski, Stanisław; Terpiłowski, Konrad; Gun'ko, Vladimir Moiseevich; Zarko, Vladimir Iljich

2015-01-01

A new adsorbent consisting of fumed, mixed alumina, silica, and titania in various proportions (AST 50) was investigated. The studied material was prepared by chemical vapor deposition method. The diameter of AST 50 primary particles was equal to about 51 nm which denotes that it can be classified as a nanomaterial. In the presented paper, the adsorption properties of polyvinyl alcohol on the ternary oxide were investigated. The polymer macromolecules were characterized by two different molecular weights and degree of hydrolysis. The polymer adsorption reaches the maximum at pH 3 and decreases with the solution pH rise. The reduction of the adsorbed PVA macromolecules is related to the electrostatic repulsion forces occurring in the studied system. The AST 50 point of zero charge (pHpzc) obtained from the potentiometric titration is equal to 4.7. Due to the nonionic character of the analyzed macromolecular compound, the polymer attendance has an insignificant effect on the AST 50 surface charge density. In the case of the adsorbent particles zeta potential, the obtained dependencies are different in the absence and presence of PVA. The shift of the slipping plane and displacement of the counter-ions from Stern layer by the adsorbed polymer chains have the greatest effect on the ζ potential value. The stability measurements indicate that the AST 50 suspensions in the presence of the background electrolyte at pH 3 and 6 are unstable. In turn, in an alkaline medium the mixed oxide suspensions exhibit the highest durability, which is a result of a large number of the negative charges on the AST 50 surface. The addition of PVA 100 significantly improves the suspension stability at pH 3 and 6; at higher pH value, the polymer presence does not influence the system durability. It is related to the steric and electrosteric stabilization of the colloidal particles by the adsorbed polyvinyl alcohol macromolecules.

Trehalose delays the reversible but not the irreversible thermal denaturation of cutinase.

PubMed

Baptista, R P; Cabral, J M; Melo, E P

2000-12-20

The effect of trehalose (0.5 M) on the thermal stability of cutinase in the alkaline pH range was studied. The thermal unfolding induced by increasing temperature was analyzed in the absence and in the presence of trehalose according to a two-state model (which assumes that only the folded and unfolded states of cutinase were present). Trehalose delays the reversible unfolding. The midpoint temperature of the unfolding transition (Tm) increases by 4.0 degrees C and 2. 6 degrees C at pH 9.2 and 10.5, respectively, in the presence of trehalose. At pH 9.2 the thermal unfolding occurs at higher temperatures (Tm is 52.6 degrees C compared to 42.0 degrees C at pH 10.5) and a refolding yield of around 80% was obtained upon cooling. This pH value was chosen to study the irreversible inactivation (long-term stability) of cutinase. Temperatures in the transition range from folded to unfolded state were selected and the rate constants of irreversible inactivation determined. Inactivation followed first-order kinetics and trehalose reduced the observed rate constants of inactivation, pointing to a stabilizing effect on the irreversible inactivation step of thermal denaturation. However, if the contribution of reversible unfolding on the irreversible inactivation of cutinase was taken into account, i.e., considering the fraction of cutinase molecules in the reversible unfolded conformation, the intrinsic rate constants can be calculated. Based on the intrinsic rate constants it was concluded that trehalose does not delay the irreversible inactivation. This conclusion was further supported by comparing the activation energy of the irreversible inactivation in the absence and in the presence of trehalose. The apparent activation energy in the absence and in the presence of trehalose were 67 and 99 Kcal/mol, respectively. The activation energy calculated from intrinsic rate constants was higher in the absence (30 Kcal/mol) than in the presence of trehalose (16 Kcal/mol), showing that kinetics of the irreversible inactivation step increased in the presence of trehalose. In fact, trehalose stabilized only the reversible step of thermal denaturation of cutinase.

Synthetic Polymers at Interfaces: Monodisperse Emulsions Multiple Emulsions and Liquid Marbles

NASA Astrophysics Data System (ADS)

Sun, Guanqing

The adsorption of polymeric materials at interfaces is an energetically favorable process which is investigated in much diversified fields, such as emulsions, bubbles, foams, liquid marbles. Pickering emulsion, which is emulsion stabilized by solid particles has been investigated for over one century and preparation of Pickering emulsion with narrow size distribution is crucial for both the theoretical study of the stabilization mechanism and practical application, such as templated fabrication of colloidosomes. The precise control over the size and functionality of polymer latices allows the preparation of monodisperse Pickering emulsions with desired sizes through SPG membrane emulsification at rather rapid rate compared to microfludic production. Double or multiple emulsions have long been investigated but its rapid destabilization has always been a major obstacle in applying them into practical applications. The modern living polymerization techniques allow us to prepare polymers with designed structure of block copolymers which makes it possible to prepare ultra-stable multiple emulsions. The precise tuning of the ratio of hydrophobic part over the hydrophilic can unveil the stabilization mechanism. Liquid marble is a new type of materials of which liquid droplets are coated by dry particles. The coating of an outer layer of dry particles renders the liquid droplets non-sticky at solid surface which is useful in transportation of small amount of liquid without leakage at extreme low friction force. The property of liquid marbles relies largely on the stabilizers and the drying condition of polymeric latices is shown to have great influence on the property of liquid marbles. Firstly, an introduction to the interfacial and colloidal science with special attention to topics on emulsions, multiple emulsion and liquid marbles is given in Chapter 1. The unique features of an interface and a discussion on the definition of colloids are introduced prior to the discussion of emulsion stabilization and preparation. A historical review of multiple emulsions is presented subsequently and the stability mechanism is discussed in details with regard to the transportation kinetics of small molecules through the separating membrane of double emulsions. The principle, property and applications of liquid marbles are then summarized. Secondly, the preparation of monodisperse Pickering emulsions stabilized by soft PNIPAM-co-MAA microgels through SPG membrane emulsification is described. The influence of the membrane pore size, pH of the particle dispersion, particle size and the operating parameters of the membrane emulsification device on the size of the emulsion droplets was investigated systematically. The improvement in monodispersity of the emulsion droplets allows us to measure the release profiles of a small molecular dye and a larger nanoparticle through the colloidosomes. It is further demonstrated that the preparation of monodisperse emulsions stabilized by other types of soft particles allows us control the stability of the emulsion with a pH trigger and improved biocompatibility. Thirdly, the preparation of multiple emulsions stabilized by a special designed PEG-b-PS diblock copolymer with desired hydrophobicity by one-step method was presented. The ultra-stability of the as-obtained multiple emulsions was ascribed to the effective steric stabilization of the two interfaces with different polymer configurations at the interfaces. A series of diblock copolymer with increasing PS chain length was then synthesized to investigate the influence of asymmetry ratio on the type of emulsions prepared. It is found that the diblock copolymers with the asymmetry ratio of approximately 1 had the highest power to stabilize multiple emulsions. The multiple emulsions were demonstrated to be a promising platform for controlled release. In the end, particle-stabilized water-in-air liquid marbles were investigated. PSco-MAA nanoparticles synthesized from surfactant-free emulsion polymerization were proved to be effective liquid marble stabilizers. The influence of drying conditions on the properties of liquid marbles was investigated through a macroscopic way. The pH value of the particle dispersion, which influences the protonation states of the particles before freeze-drying, has a profound influence on the property of the stabilized liquid marbles. A brief comment to the future of work of these investigated systems is delivered in the last part.

Elucidation of stabilizing oil-in-water Pickering emulsion with different modified maize starch-based nanoparticles.

PubMed

Ye, Fan; Miao, Ming; Jiang, Bo; Campanella, Osvaldo H; Jin, Zhengyu; Zhang, Tao

2017-08-15

The aim of present study was to study the medium-chain triacylglycerol-in-water (O/W) Pickering emulsion stabilized using different modified starch-based nanoparticles (octenylsuccinylation treated soluble starch nanoparticle, OSA-SSNP, and insoluble starch nanoparticle, ISNP). The major factors for affecting the system stability, rheological behaviour and microstructure of the emulsions were also investigated. The parameters of the O/W emulsions stabilized by OSA-SSNP or ISNP were selected as follows: 3.0% of starch nanoparticles concentration, 50% of MCT fraction and 7.0 of system pH. The rheological properties indicated that both emulsions displayed shear-thinning behaviour as a non-Newtonian fluid. For OSA-SSNP, the viscosities of the emulsion were higher than those of ISNP throughout shear rate range for the same condition. The plot of droplet size distribution for emulsion stabilized OSA-SSNP appeared as a single narrow peak, whereas a broader droplet size distribution with bimodal pattern was observed for emulsion stabilized ISNP. The microscopy results showed that both OSA-SSNP and ISNP were adsorbed at oil-water interface to form a barrier film and retard the phase separation. When emulsion was stored for 30d, no phase separation was detected for O/W emulsion, revealing high stability of emulsion stabilized by both OSA-SSNP and ISNP. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microencapsulation of Ascorbic Acid for Enhanced Long-term Retention during Storage

DTIC Science & Technology

2011-01-01

in fortified instant Asian noodles by use of capillary electrophoresis. Food Chemistry 112(2): 507–514. Hau Fung Cheung, R., Marriott, P.J . and...D., Small, D. M. and Marriott, P. J. (2008). Investigation of folic acid stability in fortified instant noodles by use of capillary electrophoresis...processing and preparation of instant Asian noodles . PhD thesis, RMIT University: Melbourne. Head, M.K. and Hansen, A.P. (1979). Stability of L

Anthrax Vaccine Powder Formulations for Nasal Mucosal Delivery

DTIC Science & Technology

2005-08-04

inhalational anthrax can be achieved in a rabbit model, by intranasal delivery of a powder rPA formulation. Here we describe the preformulation and...fluorescence. Based on these stability profiles, spray freeze-dried (SFD) formulations were prepared at pH 7–8 using trehalose as stabilizer and a CpG...gas- trointestinal, and pulmonary routes. The inhaled form is of particular concern considering its de- monstrated use as a bioweapon.1–4 Inhalational

Effect of pH, temperature, and salt on the stability of Escherichia coli- and Chinese hamster ovary cell-derived IgG1 Fc.

PubMed

Li, Cynthia H; Narhi, Linda O; Wen, Jie; Dimitrova, Mariana; Wen, Zai-qing; Li, Jenny; Pollastrini, Joseph; Nguyen, Xichdao; Tsuruda, Trace; Jiang, Yijia

2012-12-18

The circulation half-life of a potential therapeutic can be increased by fusing the molecule of interest (an active peptide, the extracellular domain of a receptor, an enzyme, etc.) to the Fc fragment of a monoclonal antibody. For the fusion protein to be a successful therapeutic, it must be stable to process and long-term storage conditions, as well as to physiological conditions. The stability of the Fc used is critical for obtaining a successful therapeutic protein. The effects of pH, temperature, and salt on the stabilities of Escherichia coli- and Chinese hamster ovary cell (CHO)-derived IgG1 Fc high-order structure were probed using a variety of biophysical techniques. Fc molecules derived from both E. coli and CHO were compared. The IgG1 Fc molecules from both sources (glycosylated and aglycosylated) are folded at neutral pH and behave similarly upon heat- and low pH-induced unfolding. The unfolding of both IgG1 Fc molecules occurs via a multistep unfolding process, with the tertiary structure and C(H)2 domain unfolding first, followed by changes in the secondary structure and C(H)3 domain. The acid-induced unfolding of IgG1 Fc molecules is only partially reversible, with the formation of high-molecular weight species. The CHO-derived Fc protein (glycosylated) is more compact (smaller hydrodynamic radius) than the E. coli-derived protein (aglycosylated) at neutral pH. Unfolding is dependent on pH and salt concentration. The glycosylated C(H)2 domain melts at a temperature 4-5 °C higher than that of the aglycosylated domain, and the low-pH-induced unfolding of the glycosylated Fc molecule occurs at a pH ~0.5 pH unit lower than that of the aglycosylated protein. The difference observed between E. coli- and CHO-derived Fc molecules primarily involves the C(H)2 domain, where the glycosylation of the Fc resides.

Density functional investigation of the adsorption effects of PH3 and SH2 on the structure stability of the Au55 and Pt55 nanoclusters

NASA Astrophysics Data System (ADS)

Guedes-Sobrinho, Diego; Chaves, Anderson S.; Piotrowski, Maurício J.; Da Silva, Juarez L. F.

2017-04-01

Although several studies have been reported for Pt55 and Au55 nanoclusters, our atomistic understanding of the interplay between the adsorbate-surface interactions and the mechanisms that lead to the formation of the distorted reduced core (DRC) structures, instead of the icosahedron (ICO) structure in gas phase, is still far from satisfactory. Here, we report a density functional theory (DFT) investigation of the role of the adsorption effects of PH3 (one lone pair of electrons) and SH2 (two lone pairs) on the relative stability of the Pt55 and Au55 nanoclusters. In gas phase, we found that the DRC structures with 7 and 9 atoms in the core region are about 5.34 eV (Pt55) and 2.20 eV (Au55) lower in energy than the ICO model with Ih symmetry and 13 atoms in the core region. However, the stability of the ICO structure increases by increasing the number of adsorbed molecules from 1 to 18, in which both DRC and ICO structures are nearly degenerate in energy at the limit of 18 ligands, which can be explained as follows. In gas phase, there is a strong compression of the cationic core region by the anionic surface atoms induced by the attractive Coulomb interactions (core+-surface-), and hence, the strain release is obtained by reducing the number of atoms in the cationic core region, which leads to the 55 atoms distorted reduced core structures. Thus, the Coulomb interactions between the core+ and surface- contribute to break the symmetry in the ICO55 structure. On the other hand, the addition of ligands on the anionic surface reduces the charge transfer between the core and surface, which contributes to decrease the Coulomb interactions and the strain on the core region of the ICO structure, and hence, it stabilizes a compact ICO structure. The same conclusion is obtained by adding van der Waals corrections to the plain DFT calculations. Similar results are obtained by the addition of steric effects, which are considered through the adsorption of triphenylphosphine (PPh3) molecules on Au55, in which the relative stability between ICO and DRC is the same as for PH3 and SH2. However, for Pt55, we found an inversion of stability due to the PPh3 ligand effects, where ICO has higher stability than DRC by 2.40 eV. Our insights are supported by several structural, electronic, and energetic analyses.

Density functional investigation of the adsorption effects of PH3 and SH2 on the structure stability of the Au55 and Pt55 nanoclusters.

PubMed

Guedes-Sobrinho, Diego; Chaves, Anderson S; Piotrowski, Maurício J; Da Silva, Juarez L F

2017-04-28

Although several studies have been reported for Pt 55 and Au 55 nanoclusters, our atomistic understanding of the interplay between the adsorbate-surface interactions and the mechanisms that lead to the formation of the distorted reduced core (DRC) structures, instead of the icosahedron (ICO) structure in gas phase, is still far from satisfactory. Here, we report a density functional theory (DFT) investigation of the role of the adsorption effects of PH 3 (one lone pair of electrons) and SH 2 (two lone pairs) on the relative stability of the Pt 55 and Au 55 nanoclusters. In gas phase, we found that the DRC structures with 7 and 9 atoms in the core region are about 5.34 eV (Pt 55 ) and 2.20 eV (Au 55 ) lower in energy than the ICO model with I h symmetry and 13 atoms in the core region. However, the stability of the ICO structure increases by increasing the number of adsorbed molecules from 1 to 18, in which both DRC and ICO structures are nearly degenerate in energy at the limit of 18 ligands, which can be explained as follows. In gas phase, there is a strong compression of the cationic core region by the anionic surface atoms induced by the attractive Coulomb interactions (core + -surface - ), and hence, the strain release is obtained by reducing the number of atoms in the cationic core region, which leads to the 55 atoms distorted reduced core structures. Thus, the Coulomb interactions between the core + and surface - contribute to break the symmetry in the ICO 55 structure. On the other hand, the addition of ligands on the anionic surface reduces the charge transfer between the core and surface, which contributes to decrease the Coulomb interactions and the strain on the core region of the ICO structure, and hence, it stabilizes a compact ICO structure. The same conclusion is obtained by adding van der Waals corrections to the plain DFT calculations. Similar results are obtained by the addition of steric effects, which are considered through the adsorption of triphenylphosphine (PPh 3 ) molecules on Au 55 , in which the relative stability between ICO and DRC is the same as for PH 3 and SH 2 . However, for Pt 55 , we found an inversion of stability due to the PPh 3 ligand effects, where ICO has higher stability than DRC by 2.40 eV. Our insights are supported by several structural, electronic, and energetic analyses.

HYDROLYSIS OF HALOACETONITRILES: LINEAR FREE ENERGY RELATIONSHIP, KINETICS AND PRODUCTS. (R825362)

EPA Science Inventory

Abstract

The hydrolysis rates of mono-, di- and trihaloacetonitriles were studied in aqueous buffer solutions at different pH. The stability of haloacetonitriles decreases and the hydrolysis rate increases with increasing pH and number of halogen atoms in the molecule:...

Cation effects on phosphatidic acid monolayers at various pH conditions.

PubMed

Zhang, Ting; Cathcart, Matthew G; Vidalis, Andrew S; Allen, Heather C

2016-10-01

The impact of pH and cations on phase behavior, stability, and surface morphology for dipalmitoylphosphatidic acid (DPPA) monolayers was investigated. At pH<10, DPPA monolayers on water are predominantly populated by neutral species and display the highest packing density. Cations are found to expand and stabilize the monolayer in the following order of increasing magnitude at pH 5.6: Na + >K + ∼Mg 2+ >Ca 2+ . Additionally, cation complexation is tied to the pH and protonation state of DPPA, which are the primary factors controlling the monolayer surface behavior. The binding affinity of cations to the headgroup and thus deprotonation capability of the cation, ranked in the order of Ca 2+ >Mg 2+ >Na + >K + , is found to be well explained by the law of matching water affinities. Nucleation of surface 3D lipid structures is observed from Ca 2+ , Mg 2+ , and Na + , but not from K + , consistent with the lowest binding affinity of K + . Unraveling cation and pH effects on DPPA monolayers is useful in further understanding the surface properties of complex systems such as organic-coated marine aerosols where organic films are directly influenced by the pH and ionic composition of the underlying aqueous phase. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Design of Stomach Acid-Stable and Mucin-Binding Enzyme Polymer Conjugates.

PubMed

Cummings, Chad S; Campbell, Alan S; Baker, Stefanie L; Carmali, Sheiliza; Murata, Hironobu; Russell, Alan J

2017-02-13

The reduced immunogenicity and increased stability of protein-polymer conjugates has made their use in therapeutic applications particularly attractive. However, the physicochemical interactions between polymer and protein, as well as the effect of this interaction on protein activity and stability, are still not fully understood. In this work, polymer-based protein engineering was used to examine the role of polymer physicochemical properties on the activity and stability of the chymotrypsin-polymer conjugates and their degree of binding to intestinal mucin. Four different chymotrypsin-polymer conjugates, each with the same polymer density, were synthesized using "grafting-from" atom transfer radical polymerization. The influence of polymer charge on chymotrypsin-polymer conjugate mucin binding, bioactivity, and stability in stomach acid was determined. Cationic polymers covalently attached to chymotrypsin showed high mucin binding, while zwitterionic, uncharged, and anionic polymers showed no mucin binding. Cationic polymers also increased chymotrypsin activity from pH 6-8, while zwitterionic polymers had no effect, and uncharged and anionic polymers decreased enzyme activity. Lastly, cationic polymers decreased the tendency of chymotrypsin to structurally unfold at extremely low pH, while uncharged and anionic polymers induced unfolding more quickly. We hypothesized that when polymers are covalently attached to the surface of a protein, the degree to which those polymers interact with the protein surface is the predominant determinant of whether the polymer will stabilize or inactivate the protein. Preferential interactions between the polymer and the protein lead to removal of water from the surface of the protein, and this, we believe, inactivates the enzyme.

Responsiveness of emulsions stabilized by lactoferrin nano-particles to simulated intestinal conditions.

PubMed

Meshulam, Dafna; Lesmes, Uri

2014-01-01

There is an upsurge of interest in the use of nano-particles to fabricate emulsions and modulate their functionality, with particular emphasis on modulating emulsion digestive fate. Food grade nano-particles formed through controlled processing and electrostatic biopolymer interactions are yet to be systematically studied for their ability to stabilize emulsions and modulate emulsion digestibility. This study focused on the responsiveness of emulsions stabilized by lactoferrin (LF) nano-particles (NPs) and dietary fibers to key digestive parameters. Compared to native LF, LF-NPs comprised emulsion exhibited elevated creaming rates as evident from accelerated stability tests performed by analytical centrifugation. The electrostatic deposition of alginate or carrageenan onto the LF-NPs significantly improved the stability of the corresponding emulsions. Further, the use of various nano-particles showed to have both beneficial and deleterious effects on emulsion responsiveness to pH (2.0 < pH < 10.0), CaCl2 (0-40 mM) and bile (0-25 mg mL(-1)). Simulated pH-stat lipolysis experiments show that the use of LF or LF-NPs had no marked effect on lipolysis. Intriguingly, the use of LF-NPs and alginate reduced emulsion lipolysis by 14% while the use of LF-NPs and carrageenan increased lipolysis by 10%. Microscopy images as well as droplet characterization in terms of size and charge indicate that the altered emulsion responsiveness may be due to physical differences in emulsion properties (e.g. droplet size) and overall organization during digestion (e.g. aggregation vs. coalescence). Overall, this study's insights could prospectively be used to harness protein nano-particles to tweak emulsion behavior during digestion.

Interactions between natural organic matter and gold nanoparticles stabilized with different organic capping agents.

PubMed

Stankus, Dylan P; Lohse, Samuel E; Hutchison, James E; Nason, Jeffrey A

2011-04-15

The adsorption of natural organic matter (NOM) to the surfaces of natural colloids and engineered nanoparticles is known to strongly influence, and in some cases control, their surface properties and aggregation behavior. As a result, the understanding of nanoparticle fate, transport, and toxicity in natural systems must include a fundamental framework for predicting such behavior. Using a suite of gold nanoparticles (AuNPs) with different capping agents, the impact of surface functionality, presence of natural organic matter, and aqueous chemical composition (pH, ionic strength, and background electrolytes) on the surface charge and colloidal stability of each AuNP type was investigated. Capping agents used in this study were as follows: anionic (citrate and tannic acid), neutral (2,2,2-[mercaptoethoxy(ethoxy)]ethanol and polyvinylpyrrolidone), and cationic (mercaptopentyl(trimethylammonium)). Each AuNP type appeared to adsorb Suwannee River Humic Acid (SRHA) as evidenced by measurable decreases in zeta potential in the presence of 5 mg C L(-1) SRHA. It was found that 5 mg C L(-1) SRHA provided a stabilizing effect at low ionic strength and in the presence of only monovalent ions while elevated concentrations of divalent cations lead to enhanced aggregation. The colloidal stability of the NPs in the absence of NOM is a function of capping agent, pH, ionic strength, and electrolyte valence. In the presence of NOM at the conditions examined in this study, the capping agent is a less important determinant of stability, and the adsorption of NOM is a controlling factor.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boggs, S. Jr.; Livermore, D.; Seitz, M.G.

Dissolved humic substances (humic and fulvic acids) occur in surface waters and groundwaters in concentrations ranging from less than 1 mg(C)/L to more than 100 mg(C)/L. Humic substances are strong complexing agents for many trace metals in the environment and are also capable of forming stable soluble complexes or chelates with radionuclides. Concentrations of humic materials as low as 1 mg(C)/L can produce a detectable increase in the mobility of some actinide elements by forming soluble complexes that inhibit sorption of the radionuclides onto rock materials. The stability of trace metal- or radionuclide-organic complexes is commonly measured by an empiricallymore » determined conditional stability constant (K'), which is based on the ratio of complexed metal (radionuclide) in solution to the product concentration of uncomplexed metal and humic complexant. Larger values of stability constants indicate greater complex stability. The stability of radionuclide-organic complexes is affected both by concentration variables and envionmental factors. In general, complexing is favored by increased of radionuclide, increased pH, and decreased ionic strength. Actinide elements are generally most soluble in their higher oxidation states. Radionuclides can also form stable, insoluble complexes with humic materials that tend to reduce radionuclide mobility. These insoluble complexes may be radionuclide-humate colloids that subsequently precipitate from solution, or complexes of radionuclides and humic substances that sorb to clay minerals or other soil particulates strongly enough to immobilize the radionuclides. Colloid formation appears to be favored by increased radionuclide concentration and lowered pH; however, the conditions that favor formation of insoluble complexes that sorb to particulates are still poorly understood. 129 refs., 25 figs., 19 tabs.« less

Poly(organo phosphazene) nanoparticles surface modified with poly(ethylene oxide).

PubMed

Vandorpe, J; Schacht, E; Stolnik, S; Garnett, M C; Davies, M C; Illum, L; Davis, S S

1996-10-05

The use of biodegradable derivatives of poly(organo phosphazenes) for the preparation of nanoparticles and their surface modification with the novel poly(ethylene oxide) derivative of poly(organo phosphazene) has been assessed using a range of in vitro characterization methods. The nanoparticles were produced by the precipitation solvent evaporation method from the derivative co-substituted with phenylalanine and glycine ethyl ester side groups. A reduction in particle size to less than 200 nm was achieved by an increase in pH of the preparation medium. The formation (and colloidal stability) of these nanoparticles seems to be controlled by two opposite effects: attractive hydrophobic interactions between phenylalanine ester groups and electrostatic repulsions arising from the carboxyl groups formed due to (partial) hydrolysis of the ester bond(s) at the high pH of the preparation medium. The poly[(glycine ethyl ester)phosphazene] derivative containing 5000-Da poly(ethylene oxide) as 5% of the side groups was used for the surface modification of nanoparticles. Adsorbed onto the particles, the polymer produced a thick coating layer of approximately 35 nm. The coated nanoparticles exhibited reduced surface negative potential and improved colloidal stability toward electrolyte-induced flocculation, relative to the uncoated system. However, the steric stabilization provided was less effective than that of a Poloxamine 908 coating. This difference in effectiveness of the steric stabilization might indicate that, although both the stabilizing polymers possess a 5000-Da poly(ethylene oxide) moiety, there is a difference in the arrangements of these poly(ethylene oxide) chains at the particle surface. (c) 1996 John Wiley & Sons, Inc.

Tuning of shell thickness of solid lipid particles impacts the chemical stability of encapsulated ω-3 fish oil.

PubMed

Salminen, Hanna; Helgason, Thrandur; Kristinsson, Bjarki; Kristbergsson, Kristberg; Weiss, Jochen

2017-03-15

This study demonstrates that tuning the shell thickness of lipid particles can modulate their oxidative stability. We hypothesized that a thick crystallized shell around the incorporated fish oil would improve the oxidative stability due to the reduced diffusion of prooxidants and oxygen. We prepared solid lipid nanoparticles (5%w/w lipid phase, 1.5%w/w surfactant, pH 7) by using different ratios of tristearin as carrier lipid and ω-3 fish oil as incorporated liquid lipid stabilized by high- or low-melting lecithin. The physical, polymorphic and oxidative stability of the lipid particles was assessed. The high-melting lecithin was the key in inducing the formation of a solidified tristearin shell around the lipid particles by interfacial heterogeneous nucleation. Lipid particles containing a higher ratio of tristearin showed a better oxidative stability. The results revealed that a crystallized tristearin layer above 10nm was required to inhibit oxidation of the incorporated fish oil. This cut-off was shown for lipid particles containing 50-60% fish oil. This research gives important insights into understanding the relation between the thickness of the crystallized shell around the lipid particles and their chemical stability. Copyright © 2016 Elsevier Inc. All rights reserved.

Potential phosphorus eutrophication mitigation strategy: Biochar carbon composition, thermal stability and pH influence phosphorus sorption.

PubMed

Ngatia, L W; Hsieh, Y P; Nemours, D; Fu, R; Taylor, R W

2017-08-01

Phosphorus (P) eutrophication is a major pollution problem globally, with unprecedented amount of P emanating from agricultural sources. But little is known about the optimization of soil-biochar P sorption capacity. The study objective was to determine how biochar feedstocks and pyrolysis conditions influences carbon (C) thermal stability, C composition and pH and in turn influence the phosphorus sorption optimization. Biochar was produced from switchgrass, kudzu and Chinese tallow at 200, 300, 400, 500, 550, 650,750 °C. Carbon thermal stability was determined by multi-element scanning thermal analysis (MESTA), C composition was determined using solid state 13 C NMR. Phosphorus sorption was determined using a mixture of 10% biochar and 90% sandy soil after incubation. Results indicate increased P sorption (P < 0.0001) and decreased P availability (P < 0.0001) with increasing biochar pyrolysis temperature. However, optimum P sorption was feedstock specific with switchgrass indicating P desorption between 200 and 550 °C. Phosphorus sorption was in the order of kudzu > switchgrass > Chinese tallow. Total C, C thermal stability, aromatic C and alkalinity increased with elevated pyrolysis temperature. Biochar alkalinity favored P sorption. There was a positive relationship between high thermal stable C and P sorption for Kudzu (r = 0.62; P = 0.0346) and Chinese tallow (r = 0.73; P = 0.0138). In conclusion, biochar has potential for P eutrophication mitigation, however, optimum biochar pyrolysis temperature for P sorption is feedstock specific and in some cases might be out of 300-500 °C temperature range commonly used for agronomic application. High thermal stable C dominated by aromatic C and alkaline pH seem to favor P sorption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hydroxide stabilization as a new tool for ballast disinfection: Efficacy of treatment on zooplankton

USGS Publications Warehouse

Moffitt, Christine M.; Watten, Barnaby J.; Barenburg, Amber; Henquinet, Jeffrey

2015-01-01

Effective and economical tools are needed for treating ship ballast to meet new regulatory requirements designed to reduce the introduction of invasive aquatic species from ship traffic. We tested the efficacy of hydroxide stabilization as a ballast disinfection tool in replicated, sequential field trials on board the M/V Ranger III in waters of Lake Superior. Ballast water was introduced into each of four identical 1,320 L stainless steel tanks during a simulated ballasting operation. Two tanks were treated with NaOH to elevate the pH to 11.7 and the remaining two tanks were held as controls without pH alteration. After retention on board for 14–18 h, CO2-rich gas recovered from one of two diesel propulsion engines was sparged into tanks treated with NaOH for 2 h to force conversion of NaOH ultimately to sodium bicarbonate, thereby lowering pH to about 7.1. Prior to gas sparging, the engine exhaust was treated by a unique catalytic converter/wet scrubber process train to remove unwanted combustion byproducts and to provide cooling. The contents of each tank were then drained and filtered through 35-µm mesh plankton nets to collect all zooplankton. The composition and relative survival of zooplankton in each tank were evaluated by microscopy. Zooplankton populations were dominated by rotifers, but copepods and cladocerans were also observed. Hydroxide stabilization was 100% effective in killing all zooplankton present at the start of the tests. Our results suggest hydroxide stabilization has potential to be an effective and practical tool to disinfect ship ballast. Further, using CO2 released from the ship engine reduces emissions and the neutralized by product, sodium bicarbonate, can have beneficial impacts on the aquatic environment.

Human Neuronal Calcium Sensor-1 Protein Avoids Histidine Residues To Decrease pH Sensitivity.

PubMed

Gong, Yehong; Zhu, Yuzhen; Zou, Yu; Ma, Buyong; Nussinov, Ruth; Zhang, Qingwen

2017-01-26

pH is highly regulated in mammalian central nervous systems. Neuronal calcium sensor-1 (NCS-1) can interact with numerous target proteins. Compared to that in the NCS-1 protein of Caenorhabditis elegans, evolution has avoided the placement of histidine residues at positions 102 and 83 in the NCS-1 protein of humans and Xenopus laevis, possibly to decrease the conformational sensitivity to pH gradients in synaptic processes. We used all-atom molecular dynamics simulations to investigate the effects of amino acid substitutions between species on human NCS-1 by substituting Arg102 and Ser83 for histidine at neutral (R102H and S83H) and acidic pHs (R102H p and S83H p ). Our cumulative 5 μs simulations revealed that the R102H mutation slightly increases the structural flexibility of loop L2 and the R102H p mutation decreases protein stability. Community network analysis illustrates that the R102H and S83H mutations weaken the interdomain and strengthen the intradomain communications. Secondary structure contents in the S83H and S83H p mutants are similar to those in the wild type, whereas the global structural stabilities and salt-bridge probabilities decrease. This study highlights the conformational dynamics effects of the R102H and S83H mutations on the local structural flexibility and global stability of NCS-1, whereas protonated histidine decreases the stability of NCS-1. Thus, histidines at positions 102 and 83 may not be compatible with the function of NCS-1 whether in the neutral or protonated state.

Stability study of the anticonvulsant enaminone (E118) using HPLC and LC-MS.

PubMed

Abdel-Hamid, Mohammed E; Edafiogho, Ivan O; Hamza, Huda M

2002-01-01

The stability of the new chemical synthetic enaminone derivative (E118) was investigated using a stability-indicating high-performance liquid chromatography (HPLC) procedure. The examined samples were analyzed using a chiral HSA column and a mobile phase (pH 7.5) containing n-octanoic acid (5 mM), isopropyl alcohol and 100 mM disodium hydrogen phosphate solution (1:9 v/v) at a flow rate of 1 ml min(-1). The developed method was specific, accurate and reproducible. The HPLC chromatograms exhibited well-resolved peaks of E118 and the degradation products at retention times <5 min. The stability of E118 was performed in 0.1 M hydrochloric acid, 0.1 M sodium hydroxide, water/ethanol (1:1) and phosphate buffer (pH approximately 7.5) solutions. E118 was found to undergo fast hydrolysis in 0.1 M hydrochloric acid solution. The decomposition of E118 followed first order kinetics under the experimental conditions. The results confirmed that protonation of the enaminone system in the molecule enhanced the hydrolysis of E118 at degradation rate constant of 0.049 min(-1) and degradation half-life of 14.1 min at 25 degrees C. However, E118 was significantly stable in 0.1 M sodium hydroxide, physiological phosphate buffer (pH 7.5) and ethanol/water (1:1) solutions. The degradation rate constants and degradation half-lives were in the ranges 0.0023-0.0086 h(-1) and 80.6-150.6 h, respectively. Analysis of the acid-induced degraded solution of E118 by liquid chromatography-mass spectrometry (LC-MS) revealed at least two degradation products of E118 at m/z 213.1 and 113.1, respectively.

Relating the variation of secondary structure of gelatin at fish oil-water interface to adsorption kinetics, dynamic interfacial tension and emulsion stability.

PubMed

Liu, Huihua; Wang, Bo; Barrow, Colin J; Adhikari, Benu

2014-01-15

The objectives of this study were to quantify the relationship between secondary structure of gelatin and its adsorption at the fish-oil/water interface and to quantify the implication of the adsorption on the dynamic interfacial tension (DST) and emulsion stability. The surface hydrophobicity of the gelatin solutions decreased when the pH increased from 4.0 to 6.0, while opposite tend was observed in the viscosity of the solution. The DST values decreased as the pH increased from 4.0 to 6.0, indicating that higher positive charges (measured trough zeta potential) in the gelatin solution tended to result in higher DST values. The adsorption kinetics of the gelatin solution was examined through the calculated diffusion coefficients (Deff). The addition of acid promoted the random coil and β-turn structures at the expense of α-helical structure. The addition of NaOH decreased the β-turn and increased the α-helix and random coil. The decrease in the random coil and triple helix structures in the gelatin solution resulted into increased Deff values. The highest diffusion coefficients, the highest emulsion stability and the lowest amount of random coil and triple helix structures were observed at pH=4.8. The lowest amount of random coil and triple helix structures in the interfacial protein layer correlated with the highest stability of the emulsion (highest ESI value). The lower amount of random coil and triple helix structures allowed higher coverage of the oil-water interface by relatively highly ordered secondary structure of gelatin. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modified granulation of red mud by weak gelling and its application to stabilization of Pb.

PubMed

Luo, Hui-li; Huang, Sheng-sheng; Luo, Lin; Wu, Gen-yi; Liu, Yan

2012-08-15

This study presents a novel modification of red mud (RM) with cementitious materials by rotary drum granulation under partial hydration. Admixtures and surfactants were applied to improve the microspore structure of red mud-based granules in order to stabilize Pb steadily. Through XRD and SEM-EDS analyses, it was demonstrated that calcite, the main alkali in RM, was partially concreted and coated. Compared to pH 12.47 for RM, the lowest pH of the granules was 10.66 implying that the release of OH(-) from hydrolysis and decomposition was decreased. Based on stabilization of Pb, influence on soil properties and forming qualities, composition of the optimum granule PSP was determined as 5% cement, 5% gypsum, 1% rice straw, and 0.1% emulsifier OP-10. Within a 90 d remediation, immobilization of ionic Pb in a 500 mg kg(-1) Pb-contaminated artificial soil was 9.85 mg kg(-1) at day 30 with 5% PSP2 as substitute. Furthermore, the reverse increase diminished as the final concentration was 11.13 mg kg(-1) while it was 14.25 mg kg(-1) by RM. The increase of residual Pb was 122.61%, which was better than the 83.92% of RM. Particularly, the highest pH in mine soil was 11.09 at day 1 with RM, but the decrease of ionic Pb was 46.26%. Meanwhile, a significant deviation from the control soil zeta-potential lasted longer and the recovery was more difficult, as compared to the granules. Therefore, a granulated modification of RM is shown to be very important when aiming at steady release of OH(-) to improve the later stabilization of Pb. Copyright © 2012 Elsevier B.V. All rights reserved.

pH-Responsive Mercaptoundecanoic Acid Functionalized Gold Nanoparticles and Applications in Catalysis

PubMed Central

Ansar, Siyam M.; Chakraborty, Saptarshi

2018-01-01

Mercaptoundecanoic acid (MUA) functionalized gold nanoparticles (AuNP-MUA) were synthesized and demonstrated to possess pH-triggered aggregation and re-dispersion, as well as the capability of phase transfer between aqueous and organic phases in response to changes in pH. The pH of aggregation for AuNP-MUA is consistent with the pKa of MUA (pH ~4) in solution, while AuNP-MUA phase transition between aqueous and organic phases occurs at pH ~9. The ion pair formation between the amine group in octadecylamine (ODA), the carboxylate group in MUA, and the hydrophobic alkyl chain of ODA facilitates the phase transfer of AuNP-MUA into an organic medium. The AuNP-MUA were investigated as a reusable catalyst in the catalytic reduction of 4-nitrophenol by borohydride—a model reaction for AuNPs. It was determined that 100% MUA surface coverage completely inhibits the catalytic activity of AuNPs. Decreasing the surface coverage was shown to increase catalytic activity, but this decrease also leads to decreased colloidal stability, recoverability, and reusability in subsequent reactions. At 60% MUA surface coverage, colloidal stability and catalytic activity were achieved, but the surface coverage was insufficient to enable redispersion following pH-induced recovery. A balance between AuNP colloidal stability, recoverability, and catalytic activity with reusability was achieved at 90% MUA surface coverage. The AuNP-MUA catalyst can also be recovered at different pH ranges depending on the recovery method employed. At pH ~4, protonation of the MUA results in reduced surface charge and aggregation. At pH ~9, ODA will form an ion-pair with the MUA and induce phase transfer into an immiscible organic phase. Both the pH-triggered aggregation/re-dispersion and aqueous/organic phase transfer methods were employed for catalyst recovery and reuse in subsequent reactions. The ability to recover and reuse the AuNP-MUA catalyst by two different methods and different pH regimes is significant, based on the fact that nanoparticle-catalyzed reactions may occur under different pH conditions. PMID:29772775

Gallium(III) complexes of DOTA and DOTA-monoamide: kinetic and thermodynamic studies.

PubMed

Kubícek, Vojtech; Havlícková, Jana; Kotek, Jan; Tircsó, Gyula; Hermann, Petr; Tóth, Eva; Lukes, Ivan

2010-12-06

Given the practical advantages of the (68)Ga isotope in positron emission tomography applications, gallium complexes are gaining increasing importance in biomedical imaging. However, the strong tendency of Ga(3+) to hydrolyze and the slow formation and very high stability of macrocyclic complexes altogether render Ga(3+) coordination chemistry difficult and explain why stability and kinetic data on Ga(3+) complexes are rather scarce. Here we report solution and solid-state studies of Ga(3+) complexes formed with the macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, (DOTA)(4-), and its mono(n-butylamide) derivative, (DO3AM(Bu))(3-). Thermodynamic stability constants, log K(GaDOTA) = 26.05 and log K(GaDO3AM(Bu)) = 24.64, were determined by out-of-cell pH-potentiometric titrations. Due to the very slow formation and dissociation of the complexes, equilibration times of up to ∼4 weeks were necessary. The kinetics of complex dissociation were followed by (71)Ga NMR under both acidic and alkaline conditions. The GaDOTA complex is significantly more inert (τ(1/2) ∼12.2 d at pH = 0 and τ(1/2) ∼6.2 h at pH = 10) than the GaDO3AM(Bu) analogue (τ(1/2) ∼2.7 d at pH = 0 and τ(1/2) ∼0.7 h at pH = 10). Nevertheless, the kinetic inertness of both chelates is extremely high and approves the application of Ga(3+) complexes of such DOTA-like ligands in molecular imaging. The solid-state structure of the GaDOTA complex, crystallized from a strongly acidic solution (pH < 1), evidenced a diprotonated form with protons localized on the free carboxylate pendants.

Multilayer ZnO/Pd/ZnO Structure as Sensing Membrane for Extended-Gate Field-Effect Transistor (EGFET) with High pH Sensitivity

NASA Astrophysics Data System (ADS)

Rasheed, Hiba S.; Ahmed, Naser M.; Matjafri, M. Z.; Al-Hardan, Naif H.; Almessiere, Munirah Abdullah; Sabah, Fayroz A.; Al-Hazeem, Nabeel Z.

2017-10-01

Metal oxide nanostructures have attracted considerable attention as pH-sensitive membranes because of their unique advantages. Specifically, the special properties of ZnO thin film, including high surface-to-volume ratio, nontoxicity, thermal stability, chemical stability, electrochemical activity, and high mechanical strength, have attracted massive interest. ZnO exhibits wide bandgap of 3.37 eV, good biocompatibility, high reactivity, robustness, and environmental stability. These unique properties explain why ZnO has the most applications among all nanostructured metal oxides based on its structure and properties. Moreover, ZnO has excellent electrical characteristics, enabling its use in accurate sensors with rapid response. ZnO nanostructures can be used in novel pH and biomedical sensing applications. However, ZnO thin film exhibits large sheet resistance and low conductivity. Increasing the conductivity or reducing the resistivity of ZnO sensing membranes is important to achieve low impedance. We propose herein a new design using a multilayer ZnO/Pd/ZnO structure as a pH-sensing membrane. Multiple layers were deposited by radio frequency (RF) sputtering for ZnO and direct current (DC) sputtering for Pd to achieve low sheet resistance. These multilayers with low sheet resistance of 15.8 Ω/sq were then successfully used to control the conductivity in extended-gate field-effect transistors (EGFETs). The resulting multilayered EGFET pH-sensor demonstrated improved sensing performance. The measured sensitivity of the pH sensor was 40 μA/pH and 52 mV/pH within the pH range from 2 to 12, rendering this structure suitable for use in various applications, including pH sensors and biosensors.

Constitutive expression of human gastric lipase in Pichia pastoris and site-directed mutagenesis of key lid-stabilizing residues.

PubMed

Sams, Laura; Amara, Sawsan; Chakroun, Almahdi; Coudre, Sébastien; Paume, Julie; Giallo, Jacqueline; Carrière, Frédéric

2017-10-01

The cDNA encoding human gastric lipase (HGL) was integrated into the genome of Pichia pastoris using the pGAPZα A transfer vector. The HGL signal peptide was replaced by the yeast α-factor to achieve an efficient secretion. Active rHGL was produced by the transformed yeast but its levels and stability were dependent on the pH. The highest activity was obtained upon buffering the culture medium at pH5, a condition that allowed preserving enzyme activity over time. A large fraction (72±2%) of secreted rHGL remained however bound to the yeast cells, and was released by washing the cell pellet with an acid glycine-HCl buffer (pH2.2). This procedure allowed establishing a first step of purification that was completed by size exclusion chromatography. N-terminal sequencing and MALDI-ToF mass spectrometry revealed that rHGL was produced in its mature form, with a global mass of 50,837±32Da corresponding to a N-glycosylated form of HGL polypeptide (43,193Da). rHGL activity was characterized as a function of pH, various substrates and in the presence of bile salts and pepsin, and was found similar to native HGL, except for slight changes in pH optima. We then studied by site-directed mutagenesis the role of three key residues (K4, E225, R229) involved in salt bridges stabilizing the lid domain that controls the access to the active site and is part of the interfacial recognition site. Their substitution has an impact on the pH-dependent activity of rHGL and its relative activities on medium and long chain triglycerides. Copyright © 2017 Elsevier B.V. All rights reserved.

Unfolding of a model protein on ion exchange and mixed mode chromatography surfaces.

PubMed

Gospodarek, Adrian M; Hiser, Diana E; O'Connell, John P; Fernandez, Erik J

2014-08-15

Recent studies with proteins indicate that conformational changes and aggregation can occur during ion exchange chromatography (IEC). Such behavior is not usually expected, but could lead to decreased yield and product degradation from both IEC and multi mode chromatography (MMC) that has ligands of both hydrophobic and charged functionalities. In this study, we used hydrogen exchange mass spectrometry to investigate unfolding of the model protein BSA on IEC and MMC surfaces under different solution conditions at 25°C. Increased solvent exposure, indicating greater unfolding relative to that in solution, was found for protein adsorbed on cationic IEC and MMC surfaces in the pH range of 3.0 to 4.5, where BSA has decreased stability in solution. There was no effect of anionic surfaces at pH values in the range from 6.0 to 9.0. Differences of solvent exposure of whole molecules when adsorbed and in solution suggest that adsorbed BSA unfolds at lower pH values and may show aggregation, depending upon pH and the surface type. Measurements on digested peptides showed that classifications of stability can be made for various regions; these are generally retained as pH is changed. When salt was added to MMC systems, where electrostatic interactions would be minimized, less solvent exposure was seen, implying that it is the cationic moieties, rather than the hydrophobic ligands, which cause greater surface unfolding at low salt concentrations. These results suggest that proteins of lower stability may exhibit unfolding and aggregation during IEC and MMC separations, as they can with hydrophobic interaction chromatography. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

NASA Astrophysics Data System (ADS)

Wang, Bin; Lou, Zhichao; Zhang, Haiqian; Xu, Bingqian

2016-03-01

The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobic β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.

Preparation of Essential Oil-Based Microemulsions for Improving the Solubility, pH Stability, Photostability, and Skin Permeation of Quercetin.

PubMed

Lv, Xia; Liu, Tiantian; Ma, Huipeng; Tian, Yan; Li, Lei; Li, Zhen; Gao, Meng; Zhang, Jianbin; Tang, Zeyao

2017-11-01

Quercetin can bring many benefits to skin based on its various bioactivities. However, the therapeutic effect of quercetin is limited due to the poor water solubility, pH instability, light instability, and skin permeation. The aim of the present work was applying essential oil-based microemulsions to improve the solubility, pH stability, photostability, and skin permeation of quercetin for topical application. Peppermint oil (PO-ME), clove oil (CO-ME), and rosemary oil (RMO-ME) were selected as model essential oils. Microemulsions composed of Cremophor EL/1,2-propanediol/essential oils (47:23:30, w/w) were selected as model formulations, based on the pseudo-ternary phase diagram and the characterizations. In the solubility study, the solubility of quercetin was improved dozens of times by microemulsions. Quercetin was found instable under alkaline condition, with 50% degraded in the solution of pH 13. However, PO-ME, CO-ME, and RMO-ME could protect quercetin from the hydroxide ions, with 47, 9, and 12% of quercetin degraded. In the photostability study, the essential oil-based microemulsions showed the capability of protecting quercetin from degradation under UV radiation. Where more than 67% of quercetin was degraded in aqueous solution, while less than 7% of quercetin degraded in microemulsions. At last, the in vitro skin permeation study showed that the essential oil-based microemulsions could enhance the permeation capacity of quercetin by 2.5-3 times compared to the aqueous solution. Hence, the prepared essential oil microemulsions could improve the solubility, pH stability, photostability, and skin permeation of quercetin, which will be beneficial for its topical application.

N-Glycosylation Improves the Pepsin Resistance of Histidine Acid Phosphatase Phytases by Enhancing Their Stability at Acidic pHs and Reducing Pepsin's Accessibility to Its Cleavage Sites

PubMed Central

Niu, Canfang; Luo, Huiying; Shi, Pengjun; Huang, Huoqing; Wang, Yaru; Yang, Peilong

2015-01-01

N-Glycosylation can modulate enzyme structure and function. In this study, we identified two pepsin-resistant histidine acid phosphatase (HAP) phytases from Yersinia kristensenii (YkAPPA) and Yersinia rohdei (YrAPPA), each having an N-glycosylation motif, and one pepsin-sensitive HAP phytase from Yersinia enterocolitica (YeAPPA) that lacked an N-glycosylation site. Site-directed mutagenesis was employed to construct mutants by altering the N-glycosylation status of each enzyme, and the mutant and wild-type enzymes were expressed in Pichia pastoris for biochemical characterization. Compared with those of the N-glycosylation site deletion mutants and N-deglycosylated enzymes, all N-glycosylated counterparts exhibited enhanced pepsin resistance. Introduction of the N-glycosylation site into YeAPPA as YkAPPA and YrAPPA conferred pepsin resistance, shifted the pH optimum (0.5 and 1.5 pH units downward, respectively) and improved stability at acidic pH (83.2 and 98.8% residual activities at pH 2.0 for 1 h). Replacing the pepsin cleavage sites L197 and L396 in the immediate vicinity of the N-glycosylation motifs of YkAPPA and YrAPPA with V promoted their resistance to pepsin digestion when produced in Escherichia coli but had no effect on the pepsin resistance of N-glycosylated enzymes produced in P. pastoris. Thus, N-glycosylation may improve pepsin resistance by enhancing the stability at acidic pH and reducing pepsin's accessibility to peptic cleavage sites. This study provides a strategy, namely, the manipulation of N-glycosylation, for improvement of phytase properties for use in animal feed. PMID:26637601

Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bin; Xu, Bingqian, E-mail: bxu@engr.uga.edu; Lou, Zhichao

2016-03-21

The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobicmore » β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.« less

A Novel Method to Quantify Soil Aggregate Stability by Measuring Aggregate Bond Energies

NASA Astrophysics Data System (ADS)

Efrat, Rachel; Rawlins, Barry G.; Quinton, John N.; Watts, Chris W.; Whitmore, Andy P.

2016-04-01

Soil aggregate stability is a key indicator of soil quality because it controls physical, biological and chemical functions important in cultivated soils. Micro-aggregates are responsible for the long term sequestration of carbon in soil, therefore determine soils role in the carbon cycle. It is thus vital that techniques to measure aggregate stability are accurate, consistent and reliable, in order to appropriately manage and monitor soil quality, and to develop our understanding and estimates of soil as a carbon store to appropriately incorporate in carbon cycle models. Practices used to assess the stability of aggregates vary in sample preparation, operational technique and unit of results. They use proxies and lack quantification. Conflicting results are therefore drawn between projects that do not provide methodological or resultant comparability. Typical modern stability tests suspend aggregates in water and monitor fragmentation upon exposure to an un-quantified amount of ultrasonic energy, utilising a laser granulometer to measure the change in mean weight diameter. In this project a novel approach has been developed based on that of Zhu et al., (2009), to accurately quantify the stability of aggregates by specifically measuring their bond energies. The bond energies are measured operating a combination of calorimetry and a high powered ultrasonic probe, with computable output function. Temperature change during sonication is monitored by an array of probes which enables calculation of the energy spent heating the system (Ph). Our novel technique suspends aggregates in heavy liquid lithium heteropolytungstate, as opposed to water, to avoid exposing aggregates to an immeasurable disruptive energy source, due to cavitation, collisions and clay swelling. Mean weight diameter is measured by a laser granulometer to monitor aggregate breakdown after successive periods of calculated ultrasonic energy input (Pi), until complete dispersion is achieved and bond energy (Pb; input energy used in aggregate breakdown) can be calculated by the following equation: ΣPi - Ph = Pb The novel technique was tested by comparing the bond energies measured from a series of soil aggregates sampled from different land management histories, to the samples corresponding stability measurement obtained from standard modern stability tests. The effectiveness of the heavy liquid as a suspension (as opposed to water) was evaluated by comparing the bond energies of samples measured in both suspensions. Our results determine i) how disruptive water is in aggregate stability tests, ii) how accurate and representative standard aggregate stability tests are, and iii) how bond strength varies depending on land use. Keywords: Aggregate; Bond; Fragmentation; Soil; Sonication; Stability References: Zhu, Z. L., Minasny, B. & Field D. J. 2009. Measurement of aggregate bond energy using ultrasonic dispersion. European Journal of Soil Science, 60, 695-705

Stability of Diazoxide in Extemporaneously Compounded Oral Suspensions.

PubMed

Friciu, Mihaela; Zaraa, Sarra; Roullin, V Gaëlle; Leclair, Grégoire

2016-01-01

The objective of this study was to evaluate the stability of diazoxide in extemporaneously compounded oral suspensions. Oral suspensions of diazoxide 10 mg/mL were prepared from either bulk drug or capsules dispersed in either Oral Mix or Oral Mix Sugar Free. These suspensions were stored at 5°C and 25°C/60%RH in bottles and oral syringes for a total of 90 days. At predetermined time intervals, suspensions were inspected for homogeneity, color or odor change; the pH was measured and the concentration of diazoxide was evaluated by ultraviolet detection using a stability-indicating high pressure liquid chromatography method. All preparations were demonstrated to be chemically stable for at least 90 days.

Structure of the Small Outer Capsid Protein, Soc: A Clamp for Stabilizing Capsids of T4-like Phages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Li; Fokine, Andrei; O'Donnell, Erin

2010-07-22

Many viruses need to stabilize their capsid structure against DNA pressure and for survival in hostile environments. The 9-kDa outer capsid protein (Soc) of bacteriophage T4, which stabilizes the virus, attaches to the capsid during the final stage of maturation. There are 870 Soc molecules that act as a 'glue' between neighboring hexameric capsomers, forming a 'cage' that stabilizes the T4 capsid against extremes of pH and temperature. Here we report a 1.9 {angstrom} resolution crystal structure of Soc from the bacteriophage RB69, a close relative of T4. The RB69 crystal structure and a homology model of T4 Soc weremore » fitted into the cryoelectron microscopy reconstruction of the T4 capsid. This established the region of Soc that interacts with the major capsid protein and suggested a mechanism, verified by extensive mutational and biochemical studies, for stabilization of the capsid in which the Soc trimers act as clamps between neighboring capsomers. The results demonstrate the factors involved in stabilizing not only the capsids of T4-like bacteriophages but also many other virus capsids.« less

Optimization of scintillator loading with the tellurium-130 isotope for long-term stability

NASA Astrophysics Data System (ADS)

Duhamel, Lauren; Song, Xiaoya; Goutnik, Michael; Kaptanoglu, Tanner; Klein, Joshua; SNO+ Collaboration

2017-09-01

Tellurium-130 was selected as the isotope for the SNO + neutrinoless double beta decay search, as 130Te decays to 130Xe via double beta decay. Linear alkyl benzene(LAB) is the liquid scintillator for the SNO + experiment. To load tellurium into scintillator, it is combined with 1,2-butanediol to form an organometallic complex, commonly called tellurium butanediol (TeBD). This study focuses on maximizing the percentage of tellurium loaded into scintillator and evaluates the complex's long-term stability. Studies on the effect of nucleation due to imperfections in the detector's surface and external particulates were employed by filtration and induced nucleation. The impact of water on the stability of TeBD complex was evaluated by liquid-nitrogen sparging, variability in pH and induced humidity. Alternative loading methods were evaluated, including the addition of stability-inducing organic compounds. Samples of tellurium-loaded scintillator were synthesized, treated, and consistently monitored in a controlled environment. It was found that the hydronium ions cause precipitation in the loaded scintillator, demonstrating that water has a detrimental effect on long-term stability. Optimization of loaded scintillator stability can contribute to the SNO + double beta decay search.

Bioelectrochemical desalination and electricity generation in microbial desalination cell with dewatered sludge as fuel.

PubMed

Meng, Fanyu; Jiang, Junqiu; Zhao, Qingliang; Wang, Kun; Zhang, Guodong; Fan, Qingxin; Wei, Liangliang; Ding, Jing; Zheng, Zhen

2014-04-01

Microbial desalination cells (MDCs) with common liquid anodic substrate exhibit a slow startup and destructive pH drop, and abiotic cathodes have high cost and low sustainability. A biocathode MDC with dewatered sludge as fuel was developed for synergistic desalination, electricity generation and sludge stabilization. Experimental results indicated that the startup period was reduced to 3d, anodic pH was maintained between 6.6 and 7.6, and high stability was shown under long-term operation (300d). When initial NaCl concentrations were 5 and 10g/L, the desalinization rates during stable operation were 46.37±1.14% and 40.74±0.89%, respectively. The maximum power output of 3.178W/m(3) with open circuit voltage (OCV) of 1.118V was produced on 130d. After 300d, 25.71±0.15% of organic matter was removed. These results demonstrated that dewatered sludge was an appropriate anodic substrate to enhance MDC stability for desalination and electricity generation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Phenotypic characterisation of colour stability of lamb meat.

PubMed

Jacob, Robin H; D'Antuono, Mario F; Gilmour, Arthur R; Warner, Robyn D

2014-02-01

A study was undertaken, using 2701 overwrapped loin samples aged for 5 days and subjected to a simulated retail display (SRD) for 3 days; sourced from lambs in the Cooperative Research Centre for Sheep Industry Innovation information nucleus flock, born 2007-2009. The ratio of reflectance of light in the wavelengths of 630 nm and 580 nm (oxy/met) was measured daily during the SRD, using a Hunterlab spectrophotometer. A series of linear mixed models was fitted to the oxy/met and time data to compare 4 breed types and identify relevant covariates, of 19, using a forward selection process. Breed type, pH at 24 h post slaughter and Linoleic acid concentration (LA) were the most important factors and covariates, in that order. Merino breed type, high pH and high LA reduced colour stability. Fitting a spline model to predict the time for oxy/met to reach a set value, represents an alternative to comparing oxy/met at a set time, for describing colour stability. Copyright © 2012 The Authors. Published by Elsevier Ltd.. All rights reserved.

Effects of tetraethyl orthosilicate (TEOS) on the light and temperature stability of a pigment from Beta vulgaris and its potential food industry applications.

PubMed

Molina, Gustavo A; Hernández-Martínez, Angel Ramon; Cortez-Valadez, Manuel; García-Hernández, Fernando; Estevez, Miriam

2014-11-05

A novel, simple and inexpensive modification method using TEOS to increase the UV light, pH and temperature stability of a red-beet-pigment extracted from Beta vulgaris has been proposed. The effects on the molecular structure of betalains were studied by FTIR spectroscopy. The presence of betacyanin was verified by UV-Vis spectroscopy and its degradation in modified red-beet-pigment was evaluated and compared to the unmodified red-beet-pigment; performance improvements of 88.33%, 16.84% and 20.90% for UV light, pH and temperature stability were obtained, respectively,. Measurements of reducing sugars, phenol, and antioxidant contents were performed on unmodified and modified red-beet-pigment and losses of close to 21%, 54% and 36%, respectively, were found to be caused by the addition of TEOS. Polar diagrams of color by unmodified and modified red-beet-pigment in models of a beverage and of a yogurt were obtained and the color is preserved, although here is a small loss in the chromaticity parameter of the modified red-beet-pigment.

Thermal stability and gel quality of myofibrillar protein as affected by soy protein isolates subjected to an acidic pH and mild heating.

PubMed

Niu, Haili; Xia, Xiufang; Wang, Chao; Kong, Baohua; Liu, Qian

2018-03-01

Thermal stability and gel quality of myofibrillar protein were evaluated with regard to the addition of native soy protein isolates (SPI) and SPI subjected to acidic pH and mild heating (modified SPI). Compared with the control, the addition of modified SPI increased the compression force of the protein gel and decreased water loss (P<0.05). Differential scanning calorimetry results showed that an addition of 0.75% native SPI decreased the first transition temperature (P<0.05), and addition of 0.5% and 0.75% modified SPI exhibited no appreciable changes on it (P>0.05), indicating that a higher concentration of modified SPI would not damage the protein thermal stability. Moreover, the addition of modified SPI enhanced hydrogen bonding and disulphide linkages. Atomic force microscopy analysis revealed that the addition of modified SPI decreased the roughness of the mixed myofibrillar protein gels. Overall, modified SPI has the potential to improve myofibrillar protein gel texture and water holding capacity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Production and characterization of cosmetic nanoemulsions containing Opuntia ficus-indica (L.) mill extract as moisturizing agent.

PubMed

Ribeiro, Renato Cesar de Azevedo; Barreto, Stella Maria de Andrade Gomes; Ostrosky, Elissa Aarantes; da Rocha-Filho, Pedro Alves; Veríssimo, Lourena Mafra; Ferrari, Márcio

2015-02-02

This study aimed to produce and characterize an oil in water (O/W) nanoemulsion containing Opuntia ficus-indica (L.) Mill hydroglycolic extract, as well as evaluate its preliminary and accelerated thermal stability and moisturizing efficacy. The formulations containing 0.5% of xanthan gum (FX) and 0.5% of xanthan gum and 1% of Opuntia ficus-indica MILL extract (FXE) were white, homogeneus and fluid in aspect. Both formulations were stable during preliminary and accelerated stability tests. FX and FXE presented a pH compatible to skin pH (4.5-6.0); droplet size varying from 92.2 to 233.6 nm; a polydispersion index (PDI) around 0.200 and a zeta potential from -26.71 to -47.01 mV. FXE was able to increase the water content of the stratum corneum for 5 h after application on the forearm. The O/W nanoemulsions containing 1% of Opuntia ficus-indica (L.) Mill extract presented suitable stability for at least for 60 days. Besides, this formulation was able to increase the water content of stratum corneum, showing its moisturizing efficacy.

A propofol microemulsion with low free propofol in the aqueous phase: formulation, physicochemical characterization, stability and pharmacokinetics.

PubMed

Cai, WeiHui; Deng, WanDing; Yang, HuiHui; Chen, XiaoPing; Jin, Fang

2012-10-15

The purpose of this study was to develop a propofol microemulsion with a low concentration of free propofol in the aqueous phase. Propofol microemulsions were prepared based on single-factor experiments and orthogonal design. The optimal microemulsion was evaluated for pH, osmolarity, particle size, zeta potential, morphology, free propofol in the aqueous phase, stability, and pharmacokinetics in beagle dogs, and comparisons made with the commercial emulsion, Diprivan(®). The pH and osmolarity of the microemulsion were similar to those of Diprivan(®). The average particle size was 22.6±0.2 nm, and TEM imaging indicated that the microemulsion particles were spherical in appearance. The concentration of free propofol in the microemulsion was 21.3% lower than that of Diprivan(®). Storage stability tests suggested that the microemulsion was stable long-term under room temperature conditions. The pharmacokinetic profile for the microemulsion showed rapid distribution and elimination compared to Diprivan(®). We conclude that the prepared microemulsion may be clinically useful as a potential carrier for propofol delivery. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis, fluorescence, TGA and crystal structure of thiazolyl-pyrazolines derived from chalcones

NASA Astrophysics Data System (ADS)

Suwunwong, T.; Chantrapromma, S.; Fun, H.-K.

2015-04-01

Thiazolyl-pyrazolines 3a-3d were synthesized in a three step procedure using chalcones as starting materials and characterized by FT-IR, UV-Vis, and 1H NMR techniques. The crystal structure of compound 3a was also determined by X-ray diffraction analysis. Compound 3a crystallized out in the orthorhombic P212121 space group with the unit cell dimensions: a = 5.2106(2) Å, b = 12.4341(5) Å, c = 33.3254(13) Å, α = β = γ = 90°, V = 2159.12(15) Å3, Z = 4, D cald = 1.372 M gm-3 and F(000) = 928. Fluorescence of 3a-3d were studied in solid state and acetonitrile solution. It was found that, these compounds exhibit the green fluorescence light (506-508 nm) in both solid and solution states. The pH stability on fluorescence property and the thermal gravimetric analysis of compound 3a were specifically carried out. It was revealed that 3a shows high thermal stability up to around 250°C and presenting high stability in various pH ranges in the acetonitrilewater matrix.

Stability-indicating HPLC-DAD methods for determination of two binary mixtures: Rabeprazole sodium-mosapride citrate and rabeprazole sodium-itopride hydrochloride.

PubMed

El-Fatatry, Hamed M; Mabrouk, Mokhtar M; Hewala, Ismail I; Emam, Ehab H

2014-08-01

Two selective stability-indicating HPLC methods are described for determination of rabeprazole sodium (RZ)-mosapride citrate (MR) and RZ-itopride hydrochloride (IO) mixtures in the presence of their ICH-stress formed degradation products. Separations were achieved on X-Bridge C18 column using two mobile phases: the first for RZ-MR mixture consisted of acetonitrile: 0.025 M KH 2 PO 4 solution: TEA (30:69:1 v/v; pH 7.0); the second for RZ-IO mixture was at ratio of 25:74:1 (v/v; pH 9.25). The detection wavelength was 283 nm. The two methods were validated and validation acceptance criteria were met in all cases. Peak purity testing using contrast angle theory, relative absorbance and log  A versus the wavelengths plots were presented. The % recoveries of the intact drugs were between 99.1% and 102.2% with RSD% values less than 1.6%. Application of the proposed HPLC methods indicated that the methods could be adopted to follow the stability of their formulations.

Stability study of oral pediatric idebenone suspensions.

PubMed

Schlatter, Joël; Bourguignon, Elodie; Majoul, Elyes; Kabiche, Sofiane; Balde, Issa-Bella; Cisternino, Salvatore; Fontan, Jean-Eudes

2017-03-01

Adapted forms for administration to infants are limited. The proposed study was performed to propose oral liquid formulations of idebenone in Ora-Plus and either Ora-Sweet or Ora-Sweet SF, Ora-Blend, Ora-Blend SF and Inorpha. Each formulation was stored in 30 ml amber glass bottle at 5 or 25 °C for 90 days. Idebenone contents in these suspensions, determined by a stability-indicating high-performance liquid chromatography method, remained stable at least 90 days in Inorpha when stored at the two temperatures. In Ora-Blend, the stability was estimated at 14 days and in other suspensions at 20 days at the two temperatures. After 90 days storage, the pH of Ora-Plus and Ora-Sweet or Ora-Sweet SF changed between -0.10 and -0.25 units. For others suspensions, the pH changes were not significant (< -0.09 unit). No change was observed in color, odor or visual microbiology. To conclude, we recommended the use of idebenone in Inorpha vehicle stable for at least 90 days at 25 °C.

Fish skin gelatin hydrolysates produced by visceral peptidase and bovine trypsin: Bioactivity and stability.

PubMed

Ketnawa, Sunantha; Benjakul, Soottawat; Martínez-Alvarez, Oscar; Rawdkuen, Saroat

2017-01-15

The peptidase from the viscera of farmed giant catfish was used for producing gelatin hydrolysates (HG) and compared with those produced from commercial bovine trypsin (HB). The degree of hydrolysis (DH) observed suggests that proteolytic cleavage rapidly occurred within the first 120min of incubation, and there was higher DH in HG than in HB. HG demonstrated the highest ACE-inhibitory activity, DPPH, ABTS radical scavenging activity, and FRAP. HB showed the highest FRAP activity. The DPPH radical scavenging activity of HG was quite stable over the pH range of 1-11, but it increased slightly when the heating duration time reached 240min at 100°C. The ACE-inhibitory activity of HG showed the highest stability at a pH of 7, and it remained very stable at 100°C for over 15-240min. The visceral peptidase from farmed giant catfish could be an alternative protease for generating protein hydrolysates with desirable bioactivities. The resulting hydrolysates showed good stability, making them potential functional ingredients for food formulations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Clay facial masks: physicochemical stability at different storage temperatures.

PubMed

Zague, Vivian; de Almeida Silva, Diego; Baby, André Rolim; Kaneko, Telma Mary; Velasco, Maria Valéria Robles

2007-01-01

Clay facial masks--formulations that contain a high percentage of solids dispersed in a liquid vehicle--have become of special interest due to specific properties presented by clays, such as particle size, cooling index, high adsorption capacity, and plasticity. Although most of the physicochemical properties of clay dispersions have been studied, specific aspects concerning the physicochemical stability of clay mask products remain unclear. This work aimed at investigating the accelerated physicochemical stability of clay mask formulations stored at different temperatures. Formulations were subjected to centrifuge testing and to thermal treatment for 15 days, during which temperature was varied from -5.0 degrees to 45.0 degrees C. The apparent viscosity and visual aspect (homogeneity) of all formulations were affected by temperature variation, whereas color, odor, and pH value remained unaltered. These results, besides the estimation of physicochemical stability under aging, can be useful in determining the best storage conditions for clay-based formulations.

Studies on electronic structure of interfaces between Ag and gelatin for stabilization of Ag nanoparticles

NASA Astrophysics Data System (ADS)

Tani, Tadaaki; Uchida, Takayuki

2015-06-01

Extremely high stability of Ag nanoparticles in photographic materials has forced us to study the electronic structures of the interfaces between thin layers of Ag, Au, and Pt and their surface membranes in ambient atmosphere by photoelectron yield spectroscopy in air and Kelvin probe method. Owing to the Fermi level equalization between a metal layer and a membrane coming from air, the electron transfer took place from the membrane to Pt and Au layers and from an Ag layer to the membrane, giving the reason for poor stability of Ag nanoparticles in air. The control of the Fermi level of an Ag layer with respect to that of a gelatin membrane in air could be widely made according to Nernst’s equation by changing the pH and pAg values of an aqueous gelatin solution used to form the membrane, and thus available to stabilize Ag nanoparticles in a gelatin matrix.

Stability of Alprazolam, Atropine Sulfate, Glutamine, Levofloxacin, Metoprolol Tartrate, Nitrofurantoin, Ondansetron Hydrochloride, Oxandrolone, Pregabaline, and Riboflavin in SyrSpend SF pH4 Oral Suspensions.

PubMed

Ferreira, Anderson O; Polonini, Hudson C; Loures da Silva, Sharlene; Cerqueira de Melo, Victor Augusto; de Andrade, Laura; Brandão, Marcos Antônio Fernandes

2017-01-01

The objective of this study was to evaluate the stability of 10 commonly used active pharmaceutical ingredients compounded in oral suspensions using an internationally used suspending vehicle (SyrSpend SF PH4): alprazolam 1.0 mg/mL, atropine sulfate 0.1 mg/mL, glutamine 250.0 mg/mL, levofloxacin 50.0 mg/mL, metoprolol tartrate 10.0 mg/mL, nitrofurantoin 2.0 mg/mL, ondansetron hydrochloride 0.8 mg/mL, oxandrolone 3.0 mg/mL, pregabaline 20.0 mg/mL, riboflavin 10.0 mg/mL. All suspensions were stored at both controlled refrigeration (2°C to 8°C) and controlled room temperature (20°C to 25°C). Stability was assessed by measuring the percent recovery at varying time points throughout a 90-day period. Active pharmaceutical ingredients quantification was performed by high-performance liquid chromatography via a stability-indicating method. Given the percentage of recovery of the active pharmaceutical ingredients within the suspensions, the beyond-use date of the final products (active pharmaceutical ingredients + vehicle) was at least 90 days for all suspensions with regard to both temperatures. This suggests that the vehicle is stable for compounding active pharmaceutical ingredients from different pharmacological classes. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

The chemical stability of abasic RNA compared to abasic DNA

PubMed Central

Küpfer, Pascal A.; Leumann, Christian J.

2007-01-01

We describe the synthesis of an abasic RNA phosphoramidite carrying a photocleavable 1-(2-nitrophenyl)ethyl (NPE) group at the anomeric center and a triisopropylsilyloxymethyl (TOM) group as 2′-O-protecting group together with the analogous DNA and the 2′-OMe RNA abasic building blocks. These units were incorporated into RNA-, 2′-OMe-RNA- and DNA for the purpose of studying their chemical stabilities towards backbone cleavage in a comparative way. Stability measurements were performed under basic conditions (0.1 M NaOH) and in the presence of aniline (pH 4.6) at 37°C. The kinetics and mechanisms of strand cleavage were followed by High pressure liquid chromotography and ESI-MS. Under basic conditions, strand cleavage at abasic RNA sites can occur via β,δ-elimination and 2′,3′-cyclophosphate formation. We found that β,δ-elimination was 154-fold slower compared to the same mechanism in abasic DNA. Overall strand cleavage of abasic RNA (including cyclophosphate formation) was still 16.8 times slower compared to abasic DNA. In the presence of aniline at pH 4.6, where only β,δ-elimination contributes to strand cleavage, a 15-fold reduced cleavage rate at the RNA abasic site was observed. Thus abasic RNA is significantly more stable than abasic DNA. The higher stability of abasic RNA is discussed in the context of its potential biological role. PMID:17151071