Diffusion of macromolecules through sclera.

PubMed

Miao, Heng; Wu, Bi-Dong; Tao, Yong; Li, Xiao-Xin

2013-02-01

To quantify the in vitro permeability coefficient over different topographical locations of porcine sclera to macromolecules with different molecular weight. Fresh equatorial and posterior superotemporal porcine sclera was mounted in a two-chamber diffusion apparatus, and its permeability to fluorescein isothiocyanate (FITC)-conjugated dextrans ranging in molecular weight from 40 kDa to 150 kDa was determined by fluorescence spectrophotometry. The sclera was processed as frozen sections and viewed with a fluorescence microscope. The thickness of the area and the thickness that macromolecules enriched in the surface of sclera were measured. The permeability coefficient (Pc) of porcine sclera to macromolecules was significantly higher (40 kDa, p = 0.028; 70 kDa, p = 0.033; 150 kDa, p = 0.007) in equatorial region than posterior, which could be attributed to the significant difference of thickness (p < 0.001, Kruskal-Wallis) between them. Moreover, linear regression indicated a significant negative relationship (40 kDa, p < 0.001; 70 kDa, p = 0.015; 150 kDa, p < 0.001) between scleral permeability coefficient and thickness. Also, Pc declined significantly with increasing molecular weight (MW, p < 0.001, Kruskal-Wallis). The area that the macromolecules enriched in the scleral surface was thicker for those with larger MW (p < 0.001, Kruskal-Wallis). The maximum MW and size for equatorial and posterior superotemporal scleral tissue were 185.01 KDa and 180.42 KDa, 9.92 nm and 9.67 nm, respectively. The permeability coefficient of porcine sclera has a significant negative relationship with scleral thickness and MW of macromolecules. Larger macromolecules are more likely to accumulate in scleral surface. The difference between topographical locations may have pharmacokinetic implications when considering transscleral diffusion of macromolecules. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

Retention of 14C-labeled multiwall carbon nanotubes by humic acid and polymers: Roles of macromolecule properties

PubMed Central

Zhao, Qing; Petersen, Elijah J.; Cornelis, Geert; Wang, Xilong; Guo, Xiaoying; Tao, Shu; Xing, Baoshan

2016-01-01

Developing methods to measure interactions of carbon nanotubes (CNTs) with soils and sediments and understanding the impact of soil and sediment properties on CNT deposition are essential for assessing CNT environmental risks. In this study, we utilized functionalized carbon-14 labeled nanotubes to systematically investigate retention of multiwall CNTs (MWCNTs) by 3 humic acids, 3 natural biopolymers, and 10 model solid-phase polymers, collectively termed macromolecules. Surface properties, rather than bulk properties of macromolecules, greatly influenced MWCNT retention. As shown via multiple linear regression analysis and path analysis, aromaticity and surface polarity were the two most positive factors for retention, suggesting retention was regulated by π-π stacking and hydrogen bonding interactions. Moreover, MWCNT deposition was irreversible. These observations may explain the high retention of MWCNT in natural soils. Moreover, our findings on the relative contribution of each macromolecule property on CNT retention provide information on macromolecule selection for removal of MWCNTs from wastewater and provide a method for measuring CNT interactions with organic macromolecules. PMID:27458320

Oriented antibody immobilization to polystyrene macrocarriers for immunoassay modified with hydrazide derivatives of poly(meth)acrylic acid

PubMed Central

Shmanai, Vadim V; Nikolayeva, Tamara A; Vinokurova, Ludmila G; Litoshka, Anatoli A

2001-01-01

Background Hydrophobic polystyrene is the most common material for solid phase immunoassay. Proteins are immobilized on polystyrene by passive adsorption, which often causes considerable denaturation. Biological macromolecules were found to better retain their functional activity when immobilized on hydrophilic materials. Polyacrylamide is a common material for solid-phase carriers of biological macromolecules, including immunoreagents used in affinity chromatography. New macroformats for immunoassay modified with activated polyacrylamide derivatives seem to be promising. Results New polymeric matrices for immunoassay in the form of 0.63-cm balls which contain hydrazide functional groups on hydrophilic polymer spacer arms at their surface shell are synthesized by modification of aldehyde-containing polystyrene balls with hydrazide derivatives of poly(meth)acrylic acid. The beads contain up to 0.31 μmol/cm2 active hydrazide groups accessible for covalent reaction with periodate-oxidized antibodies. The matrices obtained allow carrying out the oriented antibody immobilization, which increases the functional activity of immunosorbents. Conclusions An efficient site-directed antibody immobilization on a macrosupport is realized. The polymer hydrophilic spacer arms are the most convenient and effective tools for oriented antibody coupling with molded materials. The suggested scheme can be used for the modification of any other solid supports containing electrophilic groups reacting with hydrazides. PMID:11545680

The electrokinetic behavior of calcium oxalate monohydrate in macromolecular solutions

NASA Technical Reports Server (NTRS)

Curreri, P. A.; Onoda, G. Y., Jr.; Finlayson, B.

1988-01-01

Electrophoretic mobilities were measured for calcium oxalate monohydrate (COM) in solutions containing macromolecules. Two mucopolysaccharides (sodium heparin and chrondroitin sulfate) and two proteins (positively charged lysozyme and negatively charged bovine serum albumin) were studied as adsorbates. The effects of pH, calcium oxalate surface charge (varied by calcium or oxalate ion activity), and citrate concentration were investigated. All four macromolecules showed evidence for chemical adsorption. The macromolecule concentrations needed for reversing the surface charge indicated that the mucopopolysacchrides have greater affinity for the COM surface than the proteins. The amount of proteins that can chemically adsorb appears to be limited to approximately one monomolecular layer. When the surface charge is high, an insufficient number of proteins can chemically adsorb to neutralize or reverse the surface charge. The remaining surface charge is balanced by proteins held near the surface by longer range electrostatic forces only. Citrate ions at high concentrations appear to compete effectively with the negative protein for surface sites but show no evidence for competing with the positively charged protein.

Separation of macromolecular proteins and rejection of toxic heavy metal ions by PEI/cSMM blend UF membranes.

PubMed

Kanagaraj, P; Nagendran, A; Rana, D; Matsuura, T; Neelakandan, S

2015-01-01

The charged surface modifying macromolecule (cSMM) was blended into the casting solution of poly(ether imide) (PEI) to prepare surface modified ultrafiltration membranes by phase inversion technique. The separation of proteins including bovine serum albumin, egg albumin, pepsin and trypsin was investigated by the fabricated membranes. On increasing cSMM content, solute rejection decreases whereas membrane flux increases. The pore size and surface porosity of the 5 wt% cSMM blend PEI membranes increases to 41.4 Å and 14.8%, respectively. Similarly, the molecular weight cut-off of the membranes ranged from 20 to 45 kDa, depending on the various compositions of the prepared membranes. The toxic heavy metal ions Cu(II), Cr(III), Zn(II) and Pb(II) from aqueous solutions were subjected to rejection by the prepared blended membrane with various concentration of polyethyleneimine (PETIM) as water soluble polymeric ligand. It was found that the rejection behavior of metal ion depends on the PETIM concentration and the stability complexation of metal ion with ligand. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of polymethacrylic acid from aqueous solutions on disperse titanium dioxide

NASA Astrophysics Data System (ADS)

Yaremko, Z. M.; Tkachenko, N. G.; Fedushinskaya, L. B.

2011-10-01

The state of macromolecules of polymethacrylic acid adsorbed on the surface of disperse titanium dioxide was assessed using a combination of the differential concentration approach to the determination of adsorption and methods for determining the size of disperse adsorbents by dynamic light scattering and sedimentation analysis in the field of centrifugal forces. Three sections were found on the isotherm of adsorption: in the first, isolated islands of adsorbed macromolecules formed; in the second, layers of macromolecules with a different degree of deformation were observed; in the third, determining the adsorption of macromolecules is complicated by other accompanying processes, and assessing the state of macromolecules in the adsorption layer becomes difficult.

Multifunctional Delivery Systems for Advanced oral Uptake of Peptide/Protein Drugs.

PubMed

Park, Jin Woo; Kim, Sun Jin; Kwag, Dong Sup; Kim, Sol; Park, Jeyoung; Youn, Yu Seok; Bae, You Han; Lee, Eun Seong

2015-01-01

In recent years, advances in biotechnology and protein engineering have enabled the production of large quantities of proteins and peptides as important therapeutic agents. Various researchers have used biocompatible functional polymers to prepare oral dosage forms of proteins and peptides for chronic use and for easier administration to enhance patient compliance. However, there is a need to enhance their safety and effectiveness further. Most macromolecules undergo severe denaturation at low pH and enzymatic degradation in the gastrointestinal tract. The macromolecules' large molecular size and low lipophilicity cause low permeation through the intestinal membrane. The major strategies that have been used to overcome these challenges (in oral drug carrier systems) can be classified as follows: enteric coating or encapsulation with pH-sensitive polymers or mucoadhesive polymers, co-administration of protease inhibitors, incorporation of absorption enhancers, modification of the physicochemical properties of the macromolecules, and site-specific delivery to the colon. This review attempts to summarize the various advanced oral delivery carriers, including nanoparticles, lipid carriers, such as liposomes, nano-aggregates using amphiphilic polymers, complex coacervation of oppositely charged polyelectrolytes, and inorganic porous particles. The particles were formulated and/or surface modified with functional polysaccharides or synthetic polymers to improve oral bioavailability of proteins and peptides. We also discuss formulation strategies to overcome barriers, therapeutic efficacies in vivo, and potential benefits and issues for successful oral dosage forms of the proteins and peptides.

Structure, cell wall elasticity and polysaccharide properties of living yeast cells, as probed by AFM

NASA Astrophysics Data System (ADS)

Alsteens, David; Dupres, Vincent; McEvoy, Kevin; Wildling, Linda; Gruber, Hermann J.; Dufrêne, Yves F.

2008-09-01

Although the chemical composition of yeast cell walls is known, the organization, assembly, and interactions of the various macromolecules remain poorly understood. Here, we used in situ atomic force microscopy (AFM) in three different modes to probe the ultrastructure, cell wall elasticity and polymer properties of two brewing yeast strains, i.e. Saccharomyces carlsbergensis and S. cerevisiae. Topographic images of the two strains revealed smooth and homogeneous cell surfaces, and the presence of circular bud scars on dividing cells. Nanomechanical measurements demonstrated that the cell wall elasticity of S. carlsbergensis is homogeneous. By contrast, the bud scar of S. cerevisiae was found to be stiffer than the cell wall, presumably due to the accumulation of chitin. Notably, single molecule force spectroscopy with lectin-modified tips revealed major differences in polysaccharide properties of the two strains. Polysaccharides were clearly more extended on S. cerevisiae, suggesting that not only oligosaccharides, but also polypeptide chains of the mannoproteins were stretched. Consistent with earlier cell surface analyses, these findings may explain the very different aggregation properties of the two organisms. This study demonstrates the power of using multiple complementary AFM modalities for probing the organization and interactions of the various macromolecules of microbial cell walls.

Controlling adsorption of albumin with hyaluronan on silica surfaces and sulfonated latex particles.

PubMed

Berts, Ida; Fragneto, Giovanna; Porcar, Lionel; Hellsing, Maja S; Rennie, Adrian R

2017-10-15

Polysaccharides are known to modify binding of proteins at interfaces and this paper describes studies of these interactions and how they are modified by pH. Specifically, the adsorption of human serum albumin on to polystyrene latex and to silica is described, focusing on how this is affected by hyaluronan. Experiments were designed to test how such binding might be modified under relevant physiological conditions. Changes in adsorption of albumin alone and the co-adsorption of albumin and hyaluronan are driven by electrostatic interactions. Multilayer binding is found to be regulated by the pH of the solution and the molecular mass and concentration of hyaluronan. Highest adsorption was observed at pH below 4.8 and for low molecular mass hyaluronan (≤150kDa) at concentrations above 2mgml -1 . On silica with grafted hyaluronan, albumin absorption is reversed by changes in solvent pH due to their strong electrostatic attraction. Albumin physisorbed on silica surfaces is also rinsed away with dilute hyaluronan solution at pH 4.8. The results demonstrate that the protein adsorption can be controlled both by changes of pH and by interaction with other biological macromolecules. Copyright © 2017 Elsevier Inc. All rights reserved.

Small-Molecule-Based Self-Assembled Ligands for G-Quadruplex DNA Surface Recognition.

PubMed

Rivera-Sánchez, María Del C; García-Arriaga, Marilyn; Hobley, Gerard; Morales-de-Echegaray, Ana V; Rivera, José M

2017-10-31

Most drugs are small molecules because of their attractive pharmacokinetics, manageable development and manufacturing, and effective binding into the concave crevices of bio-macromolecules. Despite these features, they often fall short when it comes to effectively recognizing the surfaces of bio-macromolecules. One way to overcome the challenge of biomolecular surface recognition is to develop small molecules that become self-assembled ligands (SALs) prior to binding. Herein, we report SALs made from 8-aryl-2'-deoxyguanosine derivatives forming precise hydrophilic supramolecular G-quadruplexes (SGQs) with excellent size, shape, and charge complementarity to G-quadruplex DNA (QDNA). We show that only those compounds forming SGQs act as SALs, which in turn differentially stabilize QDNAs from selected oncogene promoters and the human telomeric regions. Fluorescence resonance energy-transfer melting assays are consistent with spectroscopic, calorimetric, and light scattering studies, showing the formation of a "sandwichlike" complex QDNA·SGQ·QDNA. These results open the door for the advent of SALs that recognize QDNAs and potentially the surfaces of other bio-macromolecules such as proteins.

Strong, low-density nanocomposites by chemical vapor deposition and polymerization of cyanoacrylates on aminated silica aerogels.

PubMed

Boday, Dylan J; Stover, Robert J; Muriithi, Beatrice; Keller, Michael W; Wertz, Jason T; Defriend Obrey, Kimberly A; Loy, Douglas A

2009-07-01

Strong polymer-silica aerogel composites were prepared by chemical vapor deposition of cyanoacrylate monomers onto amine-modified aerogels. Amine-modified silica aerogels were prepared by copolymerizing small amounts of (aminopropyl)triethoxysilane with tetraethoxysilane. After silation of the aminated gels with hexamethyldisilazane, they were dried as aerogels using supercritical carbon dioxide processing. The resulting aerogels had only the amine groups as initiators for the cyanoacrylate polymerizations, resulting in cyanoacrylate macromolecules that were higher in molecular weight than those observed with unmodified silica and that were covalently attached to the silica surface. Starting with aminated silica aerogels that were 0.075 g/cm(3) density, composite aerogels were made with densities up to 0.220 g/cm(3) and up to 31 times stronger (flexural strength) than the precursor aerogel and about 2.3 times stronger than an unmodified silica aerogel of the same density.

Cellulose microfibrils grafted with PBA via surface-initiated atom transfer radical polymerization for biocomposite reinforcement.

PubMed

Li, Shuzhao; Xiao, Miaomiao; Zheng, Anna; Xiao, Huining

2011-09-12

Immobilizing poly(butyl acrylate) (PBA) on cellulose microfibrils (CMFs) by atom transfer radical polymerization (ATRP) of butyl acrylate (BA) on the surface of 2-bromoisobutyryl-functionalized CMF generated highly hydrophobic microfibrils (CMF-PBA) with a hard core and a soft-shell structure. TGA and static water contact angle results suggested that the surfaces of the modified CMF samples were not completely covered by PBA chains until the molecular weight of grafts became sufficiently long. The GPC results indicated that the grafts with low molecular weight showed controlled/"living" characteristics of the surface-initiated ATRP; however, there existed more side reactions with the increase in molecular weights. Biocomposites consisting of polypropylene (PP) and CMF-PBA samples exhibited significantly improved compatibility, interface adhesion, and mechanical properties with the increase in PBA graft length. The findings confirmed that the longer grafts facilitated the better entanglement of PBA grafts with PP macromolecules and thus further improved the mechanical properties.

FTIR and Vis-FUV real time spectroscopic ellipsometry studies of polymer surface modifications during ion beam bombardment

NASA Astrophysics Data System (ADS)

Laskarakis, A.; Gravalidis, C.; Logothetidis, S.

2004-02-01

The continuously increasing application of polymeric materials in many scientific and technological fields has motivated an extensive use of polymer surface treatments, which modify the physical and chemical properties of polymer surfaces leading to surface activation and promotion of the surface adhesion. Fourier transform IR spectroscopic ellipsometry (FTIRSE) and phase modulated ellipsometry (PME) in the IR and Vis-FUV spectral regions respectively have been employed for in situ and real time monitoring of the structural changes on the polymer surface obtained by Ar + ion bombardment. The polymers were industrially supplied polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) membranes. The Ar + ion bombardment has found to change the chemical bonding of the films and especially the amount of the CO, C-C and CC groups. The detailed study of the FTIRSE spectra reveals important information about the effect of the Ar + ion bombardment on each of the above bonding groups. Also, the modification of the characteristic features, attributed to electronic transitions in specific bonds of PET and PEN macromolecules, has been studied using PME.

A Study of Biomolecules as Growth Modifiers of Calcium Oxalate Crystals

NASA Astrophysics Data System (ADS)

Kwak, Junha John

Crystallization processes are ubiquitous in nature, science, and technology. Controlling crystal growth is pivotal in many industries as material properties and functions can be tailored by tuning crystal habits (e.g. size, shape, phase). In biomineralization, organisms exert excellent control over bottom-up synthesis and assembly of inorganic-organic structures (e.g. bones, teeth, exoskeletons). This is made possible by growth modifiers that range from small molecules to macromolecules, such as proteins. Molecular recognition of the mineral phase allows proteins to function as nucleation templates, matrices, and growth inhibitors or promoters. We are interested in taking a biomimetic approach to control crystallization via biomolecular growth modifiers. We investigated calcium oxalate monohydrate (COM), found in plants and kidney stones, as a model system of crystallization. We studied the effects of four common proteins on COM crystallization: bovine serum albumin (BSA), transferrin, lactoferrin, and lysozyme. Through kinetic studies of COM crystallization, we classified BSA and lysozyme as COM growth inhibitor and promoter respectively. Their inhibition and promotion effects were also evident in the macroscopic crystal habit. Through adsorption and microscopy experiments, we showed that BSA exhibits binding specificity for the apical surfaces of macroscopic COM crystals. Lysozyme, on the other, functions via a non-binding mechanism at the surface to accelerate the growth of the apical surfaces. We also synthesized and studied peptides derived from the protein primary sequences to identify putative domains responsible for these inhibition and promotion effects. Collectively, our study of physiologically relevant biomolecules suggests potential roles of COM modifiers in pathological crystallization and helps to develop guidelines for rational design of biomolecular growth modifiers for applications in crystal engineering.

Specificity of marine microbial surface interactions.

PubMed Central

Imam, S H; Bard, R F; Tosteson, T R

1984-01-01

The macromolecular surface components involved in intraspecific cell surface interactions of the green microalga Chlorella vulgaris and closely associated bacteria were investigated. The specific surface attachment between this alga and its associated bacteria is mediated by lectin-like macromolecules associated with the surfaces of these cells. The binding activity of these surface polymers was inhibited by specific simple sugars; this suggests the involvement of specific receptor-ligand binding sites on the interactive surfaces. Epifluorescent microscopic evaluation of bacteria-alga interactions in the presence and absence of the macromolecules that mediate these interactions showed that the glycoproteins active in these processes were specific to the microbial sources from which they were obtained. The demonstration and definition of the specificity of these interactions in mixed microbial populations may play an important role in our understanding of the dynamics of marine microbial populations in the sea. PMID:6508293

High Relaxivity Gadolinium Hydroxypyridonate-Viral Capsid Conjugates: Nano-sized MRI Contrast Agents

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

Meux, Susan C.; Datta, Ankona; Hooker, Jacob M.

2007-08-29

High relaxivity macromolecular contrast agents based on the conjugation of gadolinium chelates to the interior and exterior surfaces of MS2 viral capsids are assessed. The proton nuclear magnetic relaxation dispersion (NMRD) profiles of the conjugates show up to a five-fold increase in relaxivity, leading to a peak relaxivity (per Gd{sup 3+} ion) of 41.6 mM{sup -1}s{sup -1} at 30 MHz for the internally modified capsids. Modification of the exterior was achieved through conjugation to flexible lysines, while internal modification was accomplished by conjugation to relatively rigid tyrosines. Higher relaxivities were obtained for the internally modified capsids, showing that (1) theremore » is facile diffusion of water to the interior of capsids and (2) the rigidity of the linker attaching the complex to the macromolecule is important for obtaining high relaxivity enhancements. The viral capsid conjugated gadolinium hydroxypyridonate complexes appear to possess two inner-sphere water molecules (q = 2) and the NMRD fittings highlight the differences in the local motion for the internal ({tau}{sub RI} = 440 ps) and external ({tau}{sub RI} = 310 ps) conjugates. These results indicate that there are significant advantages of using the internal surface of the capsids for contrast agent attachment, leaving the exterior surface available for the installation of tissue targeting groups.« less

Adsorption at air-water and oil-water interfaces and self-assembly in aqueous solution of ethoxylated polysorbate nonionic surfactants.

PubMed

Penfold, Jeffrey; Thomas, Robert K; Li, Peixun X; Petkov, Jordan T; Tucker, Ian; Webster, John R P; Terry, Ann E

2015-03-17

The Tween nonionic surfactants are ethoxylated sorbitan esters, which have 20 ethylene oxide groups attached to the sorbitan headgroup and a single alkyl chain, lauryl, palmityl, stearyl, or oleyl. They are an important class of surfactants that are extensively used in emulsion and foam stabilization and in applications associated with foods, cosmetics and pharmaceuticals. A range of ethoxylated polysorbate surfactants, with differing degrees of ethoxylation from 3 to 50 ethylene oxide groups, have been synthesized and characterized by neutron reflection, small-angle neutron scattering, and surface tension. In conjunction with different alkyl chain groups, this provides the opportunity to modify their surface properties, their self-assembly in solution, and their interaction with macromolecules, such as proteins. Adsorption at the air-water and oil-water interfaces and solution self-assembly of the range of ethoxylated polysorbate surfactants synthesized are presented and discussed.

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

NASA Astrophysics Data System (ADS)

Siegel, Jakub; Lyutakov, Oleksiy; Polívková, Markéta; Staszek, Marek; Hubáček, Tomáš; Švorčík, Václav

2017-10-01

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV-vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

Rapid transport within cerebral perivascular spaces underlies widespread tracer distribution in the brain after intranasal administration.

PubMed

Lochhead, Jeffrey J; Wolak, Daniel J; Pizzo, Michelle E; Thorne, Robert G

2015-03-01

The intranasal administration route is increasingly being used as a noninvasive method to bypass the blood-brain barrier because evidence suggests small fractions of nasally applied macromolecules may reach the brain directly via olfactory and trigeminal nerve components present in the nasal mucosa. Upon reaching the olfactory bulb (olfactory pathway) or brainstem (trigeminal pathway), intranasally delivered macromolecules appear to rapidly distribute within the brains of rodents and primates. The mechanisms responsible for this distribution have yet to be fully characterized. Here, we have used ex vivo fluorescence imaging to show that bulk flow within the perivascular space (PVS) of cerebral blood vessels contributes to the rapid central distribution of fluorescently labeled 3 and 10 kDa dextran tracers after intranasal administration in anesthetized adult rats. Comparison of tracer plasma levels and fluorescent signal distribution associated with the PVS of surface arteries and internal cerebral vessels showed that the intranasal route results in unique central access to the PVS not observed after matched intravascular dosing in separate animals. Intranasal targeting to the PVS was tracer size dependent and could be regulated by modifying nasal epithelial permeability. These results suggest cerebral perivascular convection likely has a key role in intranasal drug delivery to the brain.

Film Self-Assembly of Oppositely Charged Macromolecules Triggered by Electrochemistry through a Morphogenic Approach.

PubMed

Dochter, Alexandre; Garnier, Tony; Pardieu, Elodie; Chau, Nguyet Trang Thanh; Maerten, Clément; Senger, Bernard; Schaaf, Pierre; Jierry, Loïc; Boulmedais, Fouzia

2015-09-22

The development of new surface functionalization methods that are easy to use, versatile, and allow local deposition represents a real scientific challenge. Overcoming this challenge, we present here a one-pot process that consists in self-assembling, by electrochemistry on an electrode, films made of oppositely charged macromolecules. This method relies on a charge-shifting polyanion, dimethylmaleic-modified poly(allylamine) (PAHd), that undergoes hydrolysis at acidic pH, leading to an overall switching of its charge. When a mixture of the two polyanions, PAHd and poly(styrenesulfonate) (PSS), is placed in contact with an electrode, where the pH is decreased locally by electrochemistry, the transformation of PAHd into a polycation (PAH) leads to the continuous self-assembly of a nanometric PAH/PSS film by electrostatic interactions. The pH decrease is obtained by the electrochemical oxidation of hydroquinone, which produces protons locally over nanometric distances. Using a negatively charged enzyme, alkaline phosphatase (AP), instead of PSS, this one-pot process allows the creation of enzymatically active films. Under mild conditions, self-assembled PAH/AP films have an enzymatic activity which is adjustable simply by controlling the self-assembly time. The selective functionalization of microelectrode arrays by PAH/AP was achieved, opening the route toward miniaturized biosensors.

Perfect mixing of immiscible macromolecules at fluid interfaces

NASA Astrophysics Data System (ADS)

Sheiko, Sergei S.; Zhou, Jing; Arnold, Jamie; Neugebauer, Dorota; Matyjaszewski, Krzysztof; Tsitsilianis, Constantinos; Tsukruk, Vladimir V.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; Rubinstein, Michael

2013-08-01

The difficulty of mixing chemically incompatible substances—in particular macromolecules and colloidal particles—is a canonical problem limiting advances in fields ranging from health care to materials engineering. Although the self-assembly of chemically different moieties has been demonstrated in coordination complexes, supramolecular structures, and colloidal lattices among other systems, the mechanisms of mixing largely rely on specific interfacing of chemically, physically or geometrically complementary objects. Here, by taking advantage of the steric repulsion between brush-like polymers tethered to surface-active species, we obtained long-range arrays of perfectly mixed macromolecules with a variety of polymer architectures and a wide range of chemistries without the need of encoding specific complementarity. The net repulsion arises from the significant increase in the conformational entropy of the brush-like polymers with increasing distance between adjacent macromolecules at fluid interfaces. This entropic-templating assembly strategy enables long-range patterning of thin films on sub-100 nm length scales.

Flexible Charged Macromolecules on Mixed Fluid Lipid Membranes: Theory and Monte Carlo Simulations

PubMed Central

Tzlil, Shelly; Ben-Shaul, Avinoam

2005-01-01

Fluid membranes containing charged lipids enhance binding of oppositely charged proteins by mobilizing these lipids into the interaction zone, overcoming the concomitant entropic losses due to lipid segregation and lower conformational freedom upon macromolecule adsorption. We study this energetic-entropic interplay using Monte Carlo simulations and theory. Our model system consists of a flexible cationic polyelectrolyte, interacting, via Debye-Hückel and short-ranged repulsive potentials, with membranes containing neutral lipids, 1% tetravalent, and 10% (or 1%) monovalent anionic lipids. Adsorption onto a fluid membrane is invariably stronger than to an equally charged frozen or uniform membrane. Although monovalent lipids may suffice for binding rigid macromolecules, polyvalent counter-lipids (e.g., phosphatidylinositol 4,5 bisphosphate), whose entropy loss upon localization is negligible, are crucial for binding flexible macromolecules, which lose conformational entropy upon adsorption. Extending Rosenbluth's Monte Carlo scheme we directly simulate polymer adsorption on fluid membranes. Yet, we argue that similar information could be derived from a biased superposition of quenched membrane simulations. Using a simple cell model we account for surface concentration effects, and show that the average adsorption probabilities on annealed and quenched membranes coincide at vanishing surface concentrations. We discuss the relevance of our model to the electrostatic-switch mechanism of, e.g., the myristoylated alanine-rich C kinase substrate protein. PMID:16126828

Fluid Physics and Macromolecular Crystal Growth in Microgravity

NASA Technical Reports Server (NTRS)

Pusey, M.; Snell, E.; Judge, R.; Chayen, N.; Boggon, T.; Helliwell, J.; Rose, M. Franklin (Technical Monitor)

2000-01-01

The molecular structure of biological macromolecules is important in understanding how these molecules work and has direct application to rational drug design for new medicines and for the improvement and development of industrial enzymes. In order to obtain the molecular structure, large, well formed, single macromolecule crystals are required. The growth of macromolecule crystals is a difficult task and is often hampered on the ground by fluid flows that result from the interaction of gravity with the crystal growth process. One such effect is the bulk movement of the crystal through the fluid due to sedimentation. A second is buoyancy driven convection close to the crystal surface. On the ground the crystallization process itself induces both of these flows.

Adsorption properties of the nanozirconia/anionic polyacrylamide system-Effects of surfactant presence, solution pH and polymer carboxyl groups content

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

2016-05-01

The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate-SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level.

Adsorbed poly(aspartate) coating limits the adverse effects of dissolved groundwater solutes on Fe0 nanoparticle reactivity with trichloroethylene.

PubMed

Phenrat, Tanapon; Schoenfelder, Daniel; Kirschling, Teresa L; Tilton, Robert D; Lowry, Gregory V

2018-03-01

For in situ groundwater remediation, polyelectrolyte-modified nanoscale zerovalent iron particles (NZVIs) have to be delivered into the subsurface, where they degrade pollutants such as trichloroethylene (TCE). The effect of groundwater organic and ionic solutes on TCE dechlorination using polyelectrolyte-modified NZVIs is unexplored, but is required for an effective remediation design. This study evaluates the TCE dechlorination rate and reaction by-products using poly(aspartate) (PAP)-modified and bare NZVIs in groundwater samples from actual TCE-contaminated sites in Florida, South Carolina, and Michigan. The effects of groundwater solutes on short- and intermediate-term dechlorination rates were evaluated. An adsorbed PAP layer on the NZVIs appeared to limit the adverse effect of groundwater solutes on the TCE dechlorination rate in the first TCE dechlorination cycle (short-term effect). Presumably, the pre-adsorption of PAP "trains" and the Donnan potential in the adsorbed PAP layer prevented groundwater solutes from further blocking NZVI reactive sites, which appeared to substantially decrease the TCE dechlorination rate of bare NZVIs. In the second and third TCE dechlorination cycles (intermediate-term effect), TCE dechlorination rates using PAP-modified NZVIs increased substantially (~100 and 200%, respectively, from the rate of the first spike). The desorption of PAP from the surface of NZVIs over time due to salt-induced desorption is hypothesized to restore NZVI reactivity with TCE. This study suggests that NZVI surface modification with small, charged macromolecules, such as PAP, helps to restore NZVI reactivity due to gradual PAP desorption in groundwater.

The role of chitosan on oral delivery of peptide-loaded nanoparticle formulation.

PubMed

Wong, Chun Y; Al-Salami, Hani; Dass, Crispin R

2017-12-01

Therapeutic peptides are conventionally administered via subcutaneous injection. Chitosan-based nanoparticles are gaining increased attention for their ability to serve as a carrier for oral delivery of peptides and vaccination. They offered superior biocompatibiltiy, controlled drug release profile and facilitated gastrointestinal (GI) absorption. The encapsulated peptides can withstand enzymatic degradation and various pH. Chitosan-based nanoparticles can also be modified by ligand conjugation to the surface of nanoparticle for transcellular absorption and specific-targeted delivery of macromolecules to the tissue of interest. Current research suggests that chitosan-based nanoparticles can deliver therapeutic peptide for the treatment of several medical conditions such as diabetes, bacterial infection and cancer. This review summarises the role of chitosan in oral nanoparticle delivery and identifies the clinical application of peptide-loaded chitosan-based nanoparticles.

Biomimetic approaches to modulate cellular adhesion in biomaterials: A review.

PubMed

Rahmany, Maria B; Van Dyke, Mark

2013-03-01

Natural extracellular matrix (ECM) proteins possess critical biological characteristics that provide a platform for cellular adhesion and activation of highly regulated signaling pathways. However, ECM-based biomaterials can have several limitations, including poor mechanical properties and risk of immunogenicity. Synthetic biomaterials alleviate the risks associated with natural biomaterials but often lack the robust biological activity necessary to direct cell function beyond initial adhesion. A thorough understanding of receptor-mediated cellular adhesion to the ECM and subsequent signaling activation has facilitated development of techniques that functionalize inert biomaterials to provide a biologically active surface. Here we review a range of approaches used to modify biomaterial surfaces for optimal receptor-mediated cell interactions, as well as provide insights into specific mechanisms of downstream signaling activation. In addition to a brief overview of integrin receptor-mediated cell function, so-called "biomimetic" techniques reviewed here include (i) surface modification of biomaterials with bioadhesive ECM macromolecules or specific binding motifs, (ii) nanoscale patterning of the materials and (iii) the use of "natural-like" biomaterials. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Host plasma proteins on the surface of pathogenic Trichomonas vaginalis.

PubMed

Peterson, K M; Alderete, J F

1982-08-01

Sodium dodecyl sulfate-gel electrophoresis and fluorography and fluorography technology revealed that pathogenic Trichomonas vaginalis was able to acquire numerous loosely associated plasma proteins during incubation in normal human plasma. These proteins were readily removed by repeated washing of the parasite in phosphate-buffered saline. Plasma proteins avidly bound to the surface of T. vaginalis were also detected using a highly sensitive and specific agglutination assay with protein A-bearing Staphylococcus aureus pretreated with monospecific antiserum directed against individual human serum proteins. These avidly associated plasma proteins could not be removed by repeated washing in phosphate-buffered saline or by treatment of washed, live organisms with surface-modifying reagents such as trypsin and periodate. A combined radioimmunoprecipitation-gel electrophoresis-fluorography methodology indicated that parasite biosynthesis of hostlike macromolecules was not responsible for the observed agglutination and reinforced the idea of trichosomal acquisition of plasma components. Finally, incubation of trichomonads with plasma in various buffers at different pH values did not alter the agglutination patterns. These and other data suggest that specific membrane sites trichomonal binding of host proteins. The biological significance of our results is discussed.

Flocculation of colloidal clay by bacterial polysaccharides: effect of macromolecule charge and structure.

PubMed

Labille, J; Thomas, F; Milas, M; Vanhaverbeke, C

2005-04-01

The molecular mechanism of montmorillonite flocculation by bacterial polysaccharides was investigated, with special emphasis on the effect of carboxylic charges in the macromolecules on the mechanisms of interaction with the clay surface. An indirect way to quantify the energy of interaction was used, by comparing the flocculation ability of variously acidic polysaccharides. Data on tensile strength of aggregates in diluted suspension were collected by timed size measurements in the domain 0.1-600 microm, using laser diffraction. The flow behavior of settled aggregates was studied by rheology measurements. Flocculation of colloidal clay suspension by polysaccharides requires cancelling of the electrostatic repulsions by salts, which allows approach of clay surfaces close enough to be bridged by adsorbing macromolecules. The amount of acidic charges of the polysaccharides, and especially their location in the molecular structure, governs the bridging mechanism and the resulting tensile strength of the aggregates. The exposure of carboxylate groups located on side chains strongly promotes flocculation. In turn, charges located on the backbone of the polysaccharide are less accessible to interaction, and the flocculation ability of such polysaccharides is lowered. Measurements at different pH indicate that adsorption of acidic polysaccharides occurs via electrostatic interactions on the amphoteric edge surface of clay platelets, whereas neutral polysaccharides rather adsorb via weak interactions. Increased tensile strength in diluted aggregates due to strong surface interactions results in proportionally increased viscosity of the concentrated aggregates.

Physicochemical properties of cross-linked and acetylated starches and products of their hydrolysis in continuous recycle membrane reactor.

PubMed

Prochaska, Krystyna; Konował, Emilia; Sulej-Chojnacka, Joanna; Lewandowicz, Grazyna

2009-11-01

The aim of the present work was to study the physicochemical properties of doubly modified, by cross-linking and acetylating, starches as well as the products of their enzymatic hydrolysis. A two step procedure of hydrolysis, including the batch and membrane reactors, were investigated. The second step of enzymatic processes were carried out in a continuous recycle membrane reactor (CRMR). Three kinds of commercial starches--two preparations of acetylated distarch adipate E1422 of different degrees of cross-linking, as well as one preparation of acetylated distarch phosphate E1414 were examined. It was found that the degree of substitution of acetyl groups in the macromolecules of starch did not influence the effectiveness of hydrolysis. However, the degree of cross-linking with adipate groups slightly decreased the efficiency of processing in the CRMR. Additionally, the relationship between the type of hydrocolloid and its adsorption activity in the air/water and oil/water systems was considered. All obtained derivatives revealed adsorption properties and reduced the surface/interface tension in the air/water and oil/water systems. The efficiency and effectiveness of adsorption of the investigated hydrocolloids were affected by the type of modification as well as the degree of substitution of acetyl groups in the macromolecules of starch. Particle size distributions formed in aqueous solutions for all investigated hydrolyses were determined and compared with results obtained for commercial products.

Importance of the Debye Screening Length on Nanowire Field Effect Transistor Sensors

PubMed Central

Stern, Eric; Wagner, Robin; Sigworth, Fred J.; Breaker, Ronald; Fahmy, Tarek M.; Reed, Mark A.

2009-01-01

Nanowire field effect transistors (NW-FETs) can serve as ultrasensitive detectors for label-free reagents. The NW-FET sensing mechanism assumes a controlled modification in the local channel electric field created by the binding of charged molecules to the nanowire surface. Careful control of the solution Debye length is critical for unambiguous selective detection of macromolecules. Here we show the appropriate conditions under which the selective binding of macromolecules is accurately sensed with NW-FET sensors. PMID:17914853

Importance of the Debye screening length on nanowire field effect transistor sensors.

PubMed

Stern, Eric; Wagner, Robin; Sigworth, Fred J; Breaker, Ronald; Fahmy, Tarek M; Reed, Mark A

2007-11-01

Nanowire field effect transistors (NW-FETs) can serve as ultrasensitive detectors for label-free reagents. The NW-FET sensing mechanism assumes a controlled modification in the local channel electric field created by the binding of charged molecules to the nanowire surface. Careful control of the solution Debye length is critical for unambiguous selective detection of macromolecules. Here we show the appropriate conditions under which the selective binding of macromolecules is accurately sensed with NW-FET sensors.

The renal excretion and retention of macromolecules: The chemical structure effect.

PubMed

Rypácek, F; Drobník, J; Chmelar, V; Kálal, J

1982-01-01

Five derivatives of polyaspartamide were used as macromolecular models to study the effect of chemical structure of macromolecules on their renal excretion and retention. The parent polymer was formed solely by N(2-hydroxyethyl)aspartamide units (I) and in its derivatives about 20% of 2-hydroxyethyl groups were randomly replaced by either n-butyl- (II), 2(4-hydroxyphenyl)ethyl- (III, N- dimethylamino propyl- (IV) or the aspartamide unit was modified to free aspartic acid carboxyl (V). The rate of clearance from the serum, the deposition in the kidney tissue in comparison with the deposition in reticuloendothelial system organs-liver and spleen, as well as tissue and cellular localisation of deposits were studied on rabbits and mice taking advantage of fluorescence labelling. The clearance of macromolecular models from the serum compartment by the glomerular filtration is mainly molecular weight controlled, while the retention of macromolecules possessing the same molecular weight by the kidney tubular epithelium is strongly affected chemical modification. About thirty and hundred times higher retentions due to reabsorption in proximal tubule were found with macromolecular models II and III respectively.

Turning theory into practice: the development of modern transdermal drug delivery systems and future trends.

PubMed

Perumal, O; Murthy, S N; Kalia, Y N

2013-01-01

Despite its remarkable barrier function, the skin remains an attractive site for systemic drug delivery given its easy accessibility, large surface area and the possibility to bypass the gastrointestinal tract and the liver and so modify drug absorption kinetics. The pioneering work of Scheuplein, Higuchi and others in the 1960s helped to explain the processes involved in passive percutaneous absorption and led to the development of mathematical models to describe transdermal drug delivery. The intervening years have seen these theories turned to practice and a significant number of transdermal systems are now available including some that employ active drug delivery. This review briefly discusses the evolution of transdermal therapeutic systems over the years and the potential of newer transdermal technologies to deliver hydrophilic drugs and macromolecules through the skin. © 2013 S. Karger AG, Basel.

Vasoactive intestinal peptide stimulates tracheal submucosal gland secretion in ferret

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

Peatfield, A.C.; Barnes, P.J.; Bratcher, C.

1983-07-01

We studied the effect of vasoactive intestinal peptide (VIP) on the output of 35S-labeled macromolecules from ferret tracheal explants either placed in beakers or suspended in modified Ussing chambers. In Ussing chamber experiments, the radiolabel precursor, sodium (35S)sulfate, and all drugs were placed on the submucosal side of the tissue. Washings were collected at 30-min intervals from the luminal side and were dialyzed to remove unbound 35S, leaving radiolabeled macromolecules. Vasoactive intestinal peptide at 3 X 10(-7) M stimulated bound 35S output by a mean of + 252.6% (n . 14). The VIP response was dose-dependent with a near maximalmore » response and a half maximal response at approximately 10(-6) M and 10(-8), M, respectively. The VIP effect was not inhibited by a mixture of tetrodotoxin, atropine, I-propranolol, and phentolamine. Vasoactive intestinal peptide had no effect on the electrical properties of the of the tissues. We conclude that VIP stimulates output of sulfated-macromolecules from ferret tracheal submucosal glands without stimulating ion transport. Our studies also suggest that VIP acts on submucosal glands via specific VIP receptors. Vasoactive intestinal peptide has been shown to increase intracellular levels of cyclic AMP, and we suggest that this may be the mechanism for its effect on the output of macromolecules. This mechanism may be important in the neural regulation of submucosal gland secretion.« less

Surface-functionalized polymethacrylic acid based hydrogel microparticles for oral drug delivery.

PubMed

Sajeesh, S; Bouchemal, K; Sharma, C P; Vauthier, C

2010-02-01

Aim of the present work was to develop novel thiol-functionalized hydrogel microparticles based on poly(methacrylic acid)-chitosan-poly(ethylene glycol) (PCP) for oral drug delivery applications. PCP microparticles were prepared by a modified ionic gelation process in aqueous medium. Thiol modification of surface carboxylic acid groups of PCP micro particles was carried out by coupling l-cysteine with a water-soluble carbodiimide. Ellman's method was adopted to quantify the sulfhydryl groups, and dynamic light-scattering technique was used to measure the average particle size. Cytotoxicity of the modified particles was evaluated on Caco 2 cells by MTT assay. Effect of thiol modification on permeability of paracellular marker fluorescence dextran (FD4) was evaluated on Caco 2 cell monolayers and freshly excised rat intestinal tissue with an Ussing chamber set-up. Mucoadhesion experiments were carried out by an ex vivo bioadhesion method with excised rat intestinal tissue. The average size of the PCP microparticles was increased after thiol modification. Thiolated microparticles significantly improved the paracellular permeability of FD4 across Caco 2 cell monolayers, with no sign of toxicity. However, the efficacy of thiolated system remained low when permeation experiments were carried out across excised intestinal membrane. This was attributed to the high adhesion of the thiolated particles on the gut mucosa. Nevertheless, it can be concluded that surface thiolation is an interesting strategy to improve paracellular permeability of hydrophilic macromolecules. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Measuring the shapes of macromolecules – and why it matters

PubMed Central

Li, Jie; Mach, Paul; Koehl, Patrice

2013-01-01

The molecular basis of life rests on the activity of biological macromolecules, mostly nucleic acids and proteins. A perhaps surprising finding that crystallized over the last handful of decades is that geometric reasoning plays a major role in our attempt to understand these activities. In this paper, we address this connection between geometry and biology, focusing on methods for measuring and characterizing the shapes of macromolecules. We briefly review existing numerical and analytical approaches that solve these problems. We cover in more details our own work in this field, focusing on the alpha shape theory as it provides a unifying mathematical framework that enable the analytical calculations of the surface area and volume of a macromolecule represented as a union of balls, the detection of pockets and cavities in the molecule, and the quantification of contacts between the atomic balls. We have shown that each of these quantities can be related to physical properties of the molecule under study and ultimately provides insight on its activity. We conclude with a brief description of new challenges for the alpha shape theory in modern structural biology. PMID:24688748

Global distribution and surface activity of macromolecules in offline simulations of marine organic chemistry

DOE PAGES

Ogunro, Oluwaseun O.; Burrows, Susannah M.; Elliott, Scott; ...

2015-10-13

Here, organic macromolecules constitute high percentage components of remote sea spray. They enter the atmosphere through adsorption onto bubbles followed by bursting at the ocean surface, and go on to influence the chemistry of the fine mode aerosol. We present a global estimate of mixed-layer organic macromolecular distributions, driven by offline marine systems model output. The approach permits estimation of oceanic concentrations and bubble film surface coverages for several classes of organic compound. Mixed layer levels are computed from the output of a global ocean biogeochemistry model by relating the macromolecules to standard biogeochemical tracers. Steady state is assumed formore » labile forms, and for longer-lived components we rely on ratios to existing transported variables. Adsorption is then represented through conventional Langmuir isotherms, with equilibria deduced from laboratory analogs. Open water concentrations locally exceed one micromolar carbon for the total of protein, polysaccharide and refractory heteropolycondensate. The shorter-lived lipids remain confined to regions of strong biological activity. Results are evaluated against available measurements for all compound types, and agreement is generally quite reasonable. Global distributions are further estimated for both fractional coverage of bubble films at the air-water interface and the two-dimensional concentration excess. Overall, we show that macromolecular mapping provides a novel tool for the comprehension of oceanic surfactant distributions. Results may prove useful in planning field experiments and assessing the potential response of surface chemical behaviors to global change.« less

Surface engineering of nanoparticles with macromolecules for epoxy curing: Development of super-reactive nitrogen-rich nanosilica through surface chemistry manipulation

NASA Astrophysics Data System (ADS)

Jouyandeh, Maryam; Jazani, Omid Moini; Navarchian, Amir H.; Shabanian, Meisam; Vahabi, Henri; Saeb, Mohammad Reza

2018-07-01

Curing behavior of epoxy-based nanocomposites depends on dispersion state of nanofillers and their physical and chemical interactions with the curing moieties. In this work, a systematic approach was introduced for chemical functionalization of nanoparticles with macromolecules in order to enrich crosslinking potential of epoxy/amine systems, particularly at late stages of cure where the curing is diffusion-controlled. Super-reactive hyperbranched polyethylenimine (PEI)-attached nanosilica was materialized in this work to facilitate epoxy-amine curing. Starting from coupling [3-(2,3-epoxypropoxy) propyl] trimethoxysilane (EPPTMS) with hyperbranched PEI, a super-reactive macromolecule was obtained and subsequently grafted onto the nanosilica surface. Eventually, a thermally-stable highly-curable nanocomposite was attained by replacement of amine and imine groups of the PEI with imide and amide groups through the reaction with pyromellitic acid dianhydride. Fourier-transform infrared spectrophotometry, X-ray diffractometry, X-ray photoelectron spectroscopy and transmission electron microscopy approved successful grafting of polymer chains onto the nanosilica surface. Thermogravimetric analyses approved a relatively high grafting ratio of ca. 21%. Curing potential of the developed super-reactive nanoparticle was uncovered through nonisothermal differential scanning calorimetry signifying an enthalpy rise of ca. 120 J/g by addition of 2 wt.% to epoxy at 5 °C/min heating rate. Even at low concentration of 0.5 wt.%, the glass transition temperature of epoxy increased from 128 to 156 °C, demonstrating prolonged crosslinking.

SURFACE MODIFICATION OF SILICA- AND CELLULOSE-BASED MICROFILTRATION MEMBRANES WITH FUNCTIONAL POLYAMINO ACIDS FOR HEAVY METAL SORPTION

EPA Science Inventory

Functionalized membranes represent a field with multiple applications. Examination of specific metal-macromolecule interactions on these surfaces presents an excellent method for characterizion of these materials. These interactions may also be exploited for heavy metal sorptio...

Coupled Segmentation of Nuclear and Membrane-bound Macromolecules through Voting and Multiphase Level Set

PubMed Central

Wen, Quan

2014-01-01

Membrane-bound macromolecules play an important role in tissue architecture and cell-cell communication, and is regulated by almost one-third of the genome. At the optical scale, one group of membrane proteins expresses themselves as linear structures along the cell surface boundaries, while others are sequestered; and this paper targets the former group. Segmentation of these membrane proteins on a cell-by-cell basis enables the quantitative assessment of localization for comparative analysis. However, such membrane proteins typically lack continuity, and their intensity distributions are often very heterogeneous; moreover, nuclei can form large clump, which further impedes the quantification of membrane signals on a cell-by-cell basis. To tackle these problems, we introduce a three-step process to (i) regularize the membrane signal through iterative tangential voting, (ii) constrain the location of surface proteins by nuclear features, where clumps of nuclei are segmented through a delaunay triangulation approach, and (iii) assign membrane-bound macromolecules to individual cells through an application of multi-phase geodesic level-set. We have validated our method using both synthetic data and a dataset of 200 images, and are able to demonstrate the efficacy of our approach with superior performance. PMID:25530633

Measurement of drug and macromolecule diffusion across atherosclerotic rabbit aorta ex vivo by attenuated total reflection-Fourier transform infrared imaging

NASA Astrophysics Data System (ADS)

Palombo, Francesca; Danoux, Charlène B.; Weinberg, Peter D.; Kazarian, Sergei G.

2009-07-01

Diffusion of two model drugs-benzyl nicotinate and ibuprofen-and the plasma macromolecule albumin across atherosclerotic rabbit aorta was studied ex vivo by attenuated total reflection-Fourier transform infrared (ATR-FTIR) imaging. Solutions of these molecules were applied to the endothelial surface of histological sections of the aortic wall that were sandwiched between two impermeable surfaces. An array of spectra, each corresponding to a specific location in the section, was obtained at various times during solute diffusion into the wall and revealed the distribution of the solutes within the tissue. Benzyl nicotinate in Ringer's solution showed higher affinity for atherosclerotic plaque than for apparently healthy tissue. Transmural concentration profiles for albumin demonstrated its permeation across the section and were consistent with a relatively low distribution volume for the macromolecule in the middle of the wall. The ability of albumin to act as a drug carrier for ibuprofen, otherwise undetected within the tissue, was demonstrated by multivariate subtraction image analysis. In conclusion, ATR-FTIR imaging can be used to study transport processes in tissue samples with high spatial and temporal resolution and without the need to label the solutes under study.

The dynamics of magnetic nanoparticles exposed to non-heating alternating magnetic field in biochemical applications: theoretical study

NASA Astrophysics Data System (ADS)

Golovin, Yuri I.; Gribanovsky, Sergey L.; Golovin, Dmitry Y.; Zhigachev, Alexander O.; Klyachko, Natalia L.; Majouga, Alexander G.; Sokolsky, Marina; Kabanov, Alexander V.

2017-02-01

In the past decade, magneto-nanomechanical approach to biochemical systems stimulation has been studied intensively. This method involves macromolecule structure local deformation via mechanical actuation of functionalized magnetic nanoparticles (f-MNPs) by non-heating low frequency (LF) alternating magnetic field (AMF). Specificity at cellular or molecular level and spatial locality in nanometer scale are its key advantages as compared to magnetic fluid hyperthermia. However, current experimental studies have weak theoretical basis. Several models of magneto-nanomechanical actuation of macromolecules and cells in non-heating uniform LF AMF are presented in the article. Single core-shell spherical, rod-like, and Janus MNPs, as well as dimers consisting of two f-MNPs with macromolecules immobilized on their surfaces are considered. AMF-induced rotational oscillations of MNPs can affect properties and functioning of macromolecules or cellular membranes attached to them via periodic deformations in nanometer scale. This could be widely used in therapy, in particular for targeted drug delivery, controlled drug release, and cancer cell killing. An aggregate composed of MNPs can affect associated macromolecules by force up to several hundreds of piconewton in the case of MNPs of tens of nanometers in diameter and LF AMF below 1 T. AMF parameters and MNP design requirements for effective in vitro and in vivo magneto-nanomechanical treatment are presented.

Validating metal binding sites in macromolecule structures using the CheckMyMetal web server

PubMed Central

Zheng, Heping; Chordia, Mahendra D.; Cooper, David R.; Chruszcz, Maksymilian; Müller, Peter; Sheldrick, George M.

2015-01-01

Metals play vital roles in both the mechanism and architecture of biological macromolecules. Yet structures of metal-containing macromolecules where metals are misidentified and/or suboptimally modeled are abundant in the Protein Data Bank (PDB). This shows the need for a diagnostic tool to identify and correct such modeling problems with metal binding environments. The "CheckMyMetal" (CMM) web server (http://csgid.org/csgid/metal_sites/) is a sophisticated, user-friendly web-based method to evaluate metal binding sites in macromolecular structures in respect to 7350 metal binding sites observed in a benchmark dataset of 2304 high resolution crystal structures. The protocol outlines how the CMM server can be used to detect geometric and other irregularities in the structures of metal binding sites and alert researchers to potential errors in metal assignment. The protocol also gives practical guidelines for correcting problematic sites by modifying the metal binding environment and/or redefining metal identity in the PDB file. Several examples where this has led to meaningful results are described in the anticipated results section. CMM was designed for a broad audience—biomedical researchers studying metal-containing proteins and nucleic acids—but is equally well suited for structural biologists to validate new structures during modeling or refinement. The CMM server takes the coordinates of a metal-containing macromolecule structure in the PDB format as input and responds within a few seconds for a typical protein structure modeled with a few hundred amino acids. PMID:24356774

Fast surface-based travel depth estimation algorithm for macromolecule surface shape description.

PubMed

Giard, Joachim; Alface, Patrice Rondao; Gala, Jean-Luc; Macq, Benoît

2011-01-01

Travel Depth, introduced by Coleman and Sharp in 2006, is a physical interpretation of molecular depth, a term frequently used to describe the shape of a molecular active site or binding site. Travel Depth can be seen as the physical distance a solvent molecule would have to travel from a point of the surface, i.e., the Solvent-Excluded Surface (SES), to its convex hull. Existing algorithms providing an estimation of the Travel Depth are based on a regular sampling of the molecule volume and the use of the Dijkstra's shortest path algorithm. Since Travel Depth is only defined on the molecular surface, this volume-based approach is characterized by a large computational complexity due to the processing of unnecessary samples lying inside or outside the molecule. In this paper, we propose a surface-based approach that restricts the processing to data defined on the SES. This algorithm significantly reduces the complexity of Travel Depth estimation and makes possible the analysis of large macromolecule surface shape description with high resolution. Experimental results show that compared to existing methods, the proposed algorithm achieves accurate estimations with considerably reduced processing times.

Targeted delivery of peptide-conjugated biocompatible gold nanoparticles into cancer cell nucleus

NASA Astrophysics Data System (ADS)

Qian, Wei; Curry, Taeyjuana; Che, Yong; Kopelman, Raoul

2013-02-01

Nucleus remains a significant target for nanoparticles with diagnostic and therapeutic applications because both genetic information of the cell and transcription machinery reside there. Novel therapeutic strategies (for example, gene therapy), enabled by safe and efficient delivery of nanoparticles and drug molecules into the nucleus, are heralded by many as the ultimate treatment for severe and intractable diseases. However, most nanomaterials and macromolecules are incapable of reaching the cell nucleus on their own, because of biological barriers carefully honed by evolution including cellular membrane and nuclear envelope. In this paper, we have demonstrated an approach of fabrication of biocompatible gold nanoparticle (Au NP)-based vehicles which can entering into cancer cell nucleus by modifying Au NPs with both PEG 5000 and two different peptides (RGD and nuclear localization signal (NLS) peptide). The Au NPs used were fabricated via femtosecond laser ablation of Au bulk target in deionized water. The Au NPs produced by this method provide chemical free, virgin surface, which allows us to carry out "Sequential Conjugation" to modify their surface with PEG 5000, RGD, and NLS. "Sequential Conjugation" described in this presentation is very critical for the fabrication of Au NP-based vehicles capable of entering into cancer cell nucleus as it enables the engineering and tuning surface chemistries of Au NPs by independently adjusting amounts of PEG and peptides bound onto surface of Au NPs so as to maximize their nuclear targeting performance and biocompatibility regarding the cell line of interest. Both optical microscopy and transmission electron microscopy (TEM) are used to confirm the in vitro targeted nuclear delivery of peptide-conjugated biocompatible Au NPs by showing their presence in the cancer cell nucleus.

Charging and Release Mechanisms of Flexible Macromolecules in Droplets

NASA Astrophysics Data System (ADS)

Oh, Myong In; Consta, Styliani

2017-08-01

We study systematically the charging and release mechanisms of a flexible macromolecule, modeled by poly(ethylene glycol) (PEG), in a droplet by using molecular dynamics simulations. We compare how PEG is solvated and charged by sodium Na+ ions in a droplet of water (H2O), acetonitrile (MeCN), and their mixtures. Initially, we examine the location and the conformation of the macromolecule in a droplet bearing no net charge. It is revealed that the presence of charge carriers do not affect the location of PEG in aqueous and MeCN droplets compared with that in the neutral droplets, but the location of the macromolecule and the droplet size do affect the PEG conformation. PEG is charged on the surface of a sodiated aqueous droplet that is found close to the Rayleigh limit. Its charging is coupled to the extrusion mechanism, where PEG segments leave the droplet once they coordinate a Na+ ion or in a correlated motion with Na+ ions. In contrast, as PEG resides in the interior of a MeCN droplet, it is sodiated inside the droplet. The compact macro-ion transitions through partially unwound states to an extended conformation, a process occurring during the final stage of desolvation and in the presence of only a handful of MeCN molecules. For charged H2O/MeCN droplets, the sodiation of PEG is determined by the H2O component, reflecting its slower evaporation and preference over MeCN for solvating Na+ ions. We use the simulation data to construct an analytical model that suggests that the droplet surface electric field may play a role in the macro-ion-droplet interactions that lead to the extrusion of the macro-ion. This study provides the first evidence of the effect of the surface electric field by using atomistic simulations. [Figure not available: see fulltext.

Refolding and characterization of the functional ligand-binding domain of human lectin-like oxidized LDL receptor.

PubMed

Xie, Qiuhong; Matsunaga, Shigeru; Shi, Xiaohua; Ogawa, Setsuko; Niimi, Setsuko; Wen, Zhesheng; Tokuyasu, Ken; Machida, Sachiko

2003-11-01

Lectin-like oxidized low-density lipoprotein receptor (LOX-1), a type II membrane protein that can recognize a variety of structurally unrelated macromolecules, plays an important role in host defense and is implicated in atherogenesis. To understand the interaction between human LOX-1 and its ligands, in this study the functional C-type lectin-like domain (CTLD) of LOX-1 was reconstituted at high efficiency from inactive aggregates in Escherichia coli using a refolding technique based on an artificial chaperone. The CD spectra of the purified domain suggested that the domain has alpha-helical structure and the blue shift of Trp residues was observed on refolding of the domain. Like wild-type hLOX-1, the refolded CTLD domain was able to bind modified LDL. Thus, even though CTLD contains six Cys residues that form disulfide bonds, it recovered its specific binding ability on refolding. This suggests that the correct disulfide bonds in CTLD were formed by the artificial chaperone technique. Although the domain lacked N-glycosylation, it showed high affinity for its ligand in surface plasmon resonance experiments. Thus, unglycosylated CTLD is sufficient for binding modified LDL.

Recent innovations in edible and/or biodegradable packaging materials.

PubMed

Guilbert, S; Cuq, B; Gontard, N

1997-01-01

Certain newly discovered characteristics of natural biopolymers should make them a choice material to be used for different types of wrappings and films. Edible and/or biodegradable packagings produced from agricultural origin macromolecules provide a supplementary and sometimes essential means to control physiological, microbiological, and physicochemical changes in food products. This is accomplished (i) by controlling mass transfers between food product and ambient atmosphere or between components in heterogeneous food product, and (iii) by modifying and controlling food surface conditions (pH, level of specific functional agents, slow release of flavour compounds), it should be stressed that the material characteristics (polysaccharide, protein, or lipid, plasticized or not, chemically modified or not, used alone or in combination) and the fabrication procedures (casting of a film-forming solution, thermoforming) must be adapted to each specific food product and usage condition (relative humidity, temperature). Some potential uses of these materials (e.g. wrapping of various fabricated foods; protection of fruits and vegetables by control of maturation; protection of meat and fish; control of internal moisture transfer in pizzas), which are hinged on film properties (e.g. organoleptic, mechanical, gas and solute barrier) are described with examples.

Modified polymethylmethacrylate as a base for thermostable optical recording media

NASA Astrophysics Data System (ADS)

Krul, L. P.; Matusevich, V.; Hoff, D.; Kowarschik, R.; Matusevich, Yu. I.; Butovskaya, G. V.; Murashko, E. A.

2007-07-01

A possibility to improve the thermal properties of holographic gratings in a photosensitive system based on polymethylmethacrylate (PMMA) and to enhance simultaneously the adhesion of the photopolymer to soda-lime glass is demonstrated. The modified PMMA was prepared by radical copolymerisation of methylmethacrylate (MMA) with acrylic acid (AA). Polymer films deposited from samples of the copolymer of MMA with AA containing 9,10-phenanthrenequinone additives were used as a photosensitive material for the recording of holographic gratings. It is possible to generate gratings that are thermally stable up to 200ºC using this modified PMMA. Dynamic thermogravimetry, differential thermal analysis and thermal mechanic analyses were used to determine the dependence of the thermal stability of the modified PMMA on the composition and the structure of its macromolecules.

Amphiphilic invertible polymers: Self-assembly into functional materials driven by environment polarity

NASA Astrophysics Data System (ADS)

Hevus, Ivan

Stimuli-responsive polymers adapt to environmental changes by adjusting their chain conformation in a fast and reversible way. Responsive polymeric materials have already found use in electronics, coatings industry, personal care, and bio-related areas. The current work aims at the development of novel responsive functional polymeric materials by manipulating environment-dependent self-assembly of a new class of responsive macromolecules strategically designed in this study,—amphiphilic invertible polymers (AIPs). Environment-dependent micellization and self-assembly of three different synthesized AIP types based on poly(ethylene glycol) as a hydrophilic fragment and varying hydrophobic constituents was demonstrated in polar and nonpolar solvents, as well as on the surfaces and interfaces. With increasing concentration, AIP micelles self-assemble into invertible micellar assemblies composed of hydrophilic and hydrophobic domains. Polarity-responsive properties of AIPs make invertible micellar assemblies functional in polar and nonpolar media including at interfaces. Thus, invertible micellar assemblies solubilize poorly soluble substances in their interior in polar and nonpolar solvents. In a polar aqueous medium, a novel stimuli-responsive mechanism of drug release based on response of AIP-based drug delivery system to polarity change upon contact with the target cell has been established using invertible micellar assemblies loaded with curcumin, a phytochemical drug. In a nonpolar medium, invertible micellar assemblies were applied simultaneously as nanoreactors and stabilizers for size-controlled synthesis of silver nanoparticles stable in both polar and nonpolar media. The developed amphiphilic nanosilver was subsequently used as seeds to promote anisotropic growth of CdSe semiconductor nanoparticles that have potential in different applications ranging from physics to medicine. Amphiphilic invertible polymers were shown to adsorb on the surface of silica nanoparticles strongly differing in polarity. AIP modified silica nanoparticles are able to adsolubilize molecules of poorly water-soluble 2-naphthol into the adsorbed polymer layer. The adsolubilization ability of adsorbed invertible macromolecules makes AIP-modified silica nanoparticles potentially useful in wastewater treatment or biomedical applications. Finally, the invertible micellar assemblies were used as functional additives to improve the appearance of electrospun silicon wires based on cyclohexasilane, a liquid silicon precursor. AIP-assisted fabrication of silicon wires from the liquid cyclohexasilane precursor has potential as a scalable method for developing electronic functional materials.

Versatile and Rapid Postfunctionalization from Cyclodextrin Modified Host Polymeric Membrane Substrate.

PubMed

Deng, Jie; Liu, Xinyue; Zhang, Shuqing; Cheng, Chong; Nie, Chuanxiong; Zhao, Changsheng

2015-09-08

Surface modification has long been of great interest to impart desired functionalities to the bioimplants. However, due to the limitations of recent technologies in surface modification, it is highly desirable to explore novel protocols, which can advantageously and efficiently endow the inert material surfaces with versatile biofunctionalities. Herein, to achieve versatile and rapid postfunctionalization of polymeric membrane, we demonstrate a new strategy for the fabrication of β-cyclodextrin (β-CD) modified host membrane substrate that can recognize a series of well-designed guest macromolecules. The surface assembly procedure was driven by the host-guest interaction between adamantane (Ad) and β-CD. β-CD immobilized host membrane was fabricated via two steps: (1) epoxy groups enriched poly(ether sulfone) (PES) membrane was first prepared via in situ cross-linking polymerization and subsequently phase separation; (2) mono-6-deoxy-6-ethylenediamine-β-CD (EDA-β-CD) was then anchored onto the surface of the epoxy functionalized PES membrane to obtain PES-CD. Subsequently, three types of Ad-terminated polymers, including Ad-poly(styrenesulfonate-co-sodium acrylate) (Ad-PSA), Ad-methoxypoly(ethylene glycol) (Ad-PEG), and Ad-poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate (Ad-PMT), were separately assembled onto the β-CD immobilized surfaces to endow the membranes with anticoagulant, antifouling, and antibacterial capability, respectively. Activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) measurements were carried out to explore the anticoagulant activity. The antifouling capability was evaluated via protein adsorption and platelet adhesion measurements. Moreover, Staphyllococcous aureus (S. aureus) was selected as model bacteria to evaluate the antibacterial ability of the functionalized membranes. The results indicated that well-regulated blood compatibility, antifouling capability, and bactericidal activity could be achieved by the proposed rapid postfunctionalization on polymeric membranes. This approach of versatile and rapid postfunctionalization is promising for the preparation of multifunctional polymeric membrane materials to meet with various demands for the further applications.

Identification of Characteristic Macromolecules of Escherichia coli Genotypes by Atomic Force Microscope Nanoscale Mechanical Mapping

NASA Astrophysics Data System (ADS)

Chang, Alice Chinghsuan; Liu, Bernard Haochih

2018-02-01

The categorization of microbial strains is conventionally based on the molecular method, and seldom are the morphological characteristics in the bacterial strains studied. In this research, we revealed the macromolecular structures of the bacterial surface via AFM mechanical mapping, whose resolution was not only determined by the nanoscale tip size but also the mechanical properties of the specimen. This technique enabled the nanoscale study of membranous structures of microbial strains with simple specimen preparation and flexible working environments, which overcame the multiple restrictions in electron microscopy and label-enable biochemical analytical methods. The characteristic macromolecules located among cellular surface were considered as surface layer proteins and were found to be specific to the Escherichia coli genotypes, from which the averaged molecular sizes were characterized with diameters ranging from 38 to 66 nm, and the molecular shapes were kidney-like or round. In conclusion, the surface macromolecular structures have unique characteristics that link to the E. coli genotype, which suggests that the genomic effects on cellular morphologies can be rapidly identified using AFM mechanical mapping. [Figure not available: see fulltext.

Cellular and Molecular Biology of Airway Mucins

PubMed Central

Lillehoj, Erik P.; Kato, Kosuke; Lu, Wenju; Kim, Kwang C.

2017-01-01

Airway mucus constitutes a thin layer of airway surface liquid with component macromolecules that covers the luminal surface of the respiratory tract. The major function of mucus is to protect the lungs through mucociliary clearance of inhaled foreign particles and noxious chemicals. Mucus is comprised of water, ions, mucin glycoproteins, and a variety of other macromolecules, some of which possess anti-microbial, anti-protease, and anti-oxidant activities. Mucins comprise the major protein component of mucus and exist as secreted and cell-associated glycoproteins. Secreted, gel-forming mucins are mainly responsible for the viscoelastic property of mucus, which is crucial for effective mucociliary clearance. Cell-associated mucins shield the epithelial surface from pathogens through their extracellular domains and regulate intracellular signaling through their cytoplasmic regions. However, neither the exact structures of mucin glycoproteins, nor the manner through which their expression is regulated, are completely understood. This chapter reviews what is currently known about the cellular and molecular properties of airway mucins. PMID:23445810

Surface tailored organobentonite enhances bacterial proliferation and phenanthrene biodegradation under cadmium co-contamination.

PubMed

Mandal, Asit; Biswas, Bhabananda; Sarkar, Binoy; Patra, Ashok K; Naidu, Ravi

2016-04-15

Co-contamination of soil and water with polycyclic aromatic hydrocarbon (PAH) and heavy metals makes biodegradation of the former extremely challenging. Modified clay-modulated microbial degradation provides a novel insight in addressing this issue. This study was conducted to evaluate the growth and phenanthrene degradation performance of Mycobacterium gilvum VF1 in the presence of a palmitic acid (PA)-grafted Arquad® 2HT-75-based organobentonite in cadmium (Cd)-phenanthrene co-contaminated water. The PA-grafted organobentonite (ABP) adsorbed a slightly greater quantity of Cd than bentonite at up to 30mgL(-1) metal concentration, but its highly negative surface charge imparted by carboxylic groups indicated the potential of being a significantly superior adsorbent of Cd at higher metal concentrations. In systems co-contained with Cd (5 and 10mgL(-1)), the Arquad® 2HT-75-modified bentonite (AB) and PA-grafted organobentonite (ABP) resulted in a significantly higher (72-78%) degradation of phenanthrene than bentonite (62%) by the bacterium. The growth and proliferation of bacteria were supported by ABP which not only eliminated Cd toxicity through adsorption but also created a congenial microenvironment for bacterial survival. The macromolecules produced during ABP-bacteria interaction could form a stable clay-bacterial cluster by overcoming the electrostatic repulsion among individual components. Findings of this study provide new insights for designing clay modulated PAH bioremediation technologies in mixed-contaminated water and soil. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrostatic potential of B-DNA: effect of interionic correlations.

PubMed Central

Gavryushov, S; Zielenkiewicz, P

1998-01-01

Modified Poisson-Boltzmann (MPB) equations have been numerically solved to study ionic distributions and mean electrostatic potentials around a macromolecule of arbitrarily complex shape and charge distribution. Results for DNA are compared with those obtained by classical Poisson-Boltzmann (PB) calculations. The comparisons were made for 1:1 and 2:1 electrolytes at ionic strengths up to 1 M. It is found that ion-image charge interactions and interionic correlations, which are neglected by the PB equation, have relatively weak effects on the electrostatic potential at charged groups of the DNA. The PB equation predicts errors in the long-range electrostatic part of the free energy that are only approximately 1.5 kJ/mol per nucleotide even in the case of an asymmetrical electrolyte. In contrast, the spatial correlations between ions drastically affect the electrostatic potential at significant separations from the macromolecule leading to a clearly predicted effect of charge overneutralization. PMID:9826596

General Characteristics of the Changes in the Thermal Stability of Proteins and Enzymes After the Chemical Modification of Their Functional Groups

NASA Astrophysics Data System (ADS)

Kutuzova, G. D.; Ugarova, N. N.; Berezin, Ilya V.

1984-11-01

The principal structural and physicochemical factors determining the stability of protein macromolecules in solution and the characteristics of the structure of the proteins from thermophilic microorganisms are examined. The mechanism of the changes in the thermal stability of proteins and enzymes after the chemical modification of their functional side groups and the experimental data concerning the influence of chemical modification on the thermal stability of proteins are analysed. The dependence of the stabilisation effect and of the changes in the structure of protein macromolecules on the degree of modification and on the nature of the modified groups and the groups introduced into proteins in the course of modification (their charge and hydrophobic properties) is demonstrated. The great practical value of the method of chemical modification for the preparation of stabilised forms of biocatalysts is shown in relation to specific examples. The bibliography includes 178 references.

Analysis of macromolecules, ligands and macromolecule-ligand complexes

DOEpatents

Von Dreele, Robert B [Los Alamos, NM

2008-12-23

A method for determining atomic level structures of macromolecule-ligand complexes through high-resolution powder diffraction analysis and a method for providing suitable microcrystalline powder for diffraction analysis are provided. In one embodiment, powder diffraction data is collected from samples of polycrystalline macromolecule and macromolecule-ligand complex and the refined structure of the macromolecule is used as an approximate model for a combined Rietveld and stereochemical restraint refinement of the macromolecule-ligand complex. A difference Fourier map is calculated and the ligand position and points of interaction between the atoms of the macromolecule and the atoms of the ligand can be deduced and visualized. A suitable polycrystalline sample of macromolecule-ligand complex can be produced by physically agitating a mixture of lyophilized macromolecule, ligand and a solvent.

Workshop on High-Field NMR and Biological Applications

NASA Astrophysics Data System (ADS)

Scientists at the Pacific Northwest Laboratory have been working toward the establishment of a new Molecular Science Research Center (MSRC). The primary scientific thrust of this new research center is in the areas of theoretical chemistry, chemical dynamics, surface and interfacial science, and studies on the structure and interactions of biological macromolecules. The MSRC will provide important new capabilities for studies on the structure of biological macromolecules. The MSRC program includes several types of advanced spectroscopic techniques for molecular structure analysis, and a theory and modeling laboratory for molecular mechanics/dynamics calculations and graphics. It is the goal to closely integrate experimental and theoretical studies on macromolecular structure, and to join these research efforts with those of the molecular biological programs to provide new insights into the structure/function relationships of biological macromolecules. One of the areas of structural biology on which initial efforts in the MSRC will be focused is the application of high field, 2-D NMR to the study of biological macromolecules. First, there is interest in obtaining 3-D structural information on large proteins and oligonucleotides. Second, one of the primary objectives is to closely link theoretical approaches to molecular structure analysis with the results obtained in experimental research using NMR and other spectroscopies.

Application of flow field-flow fractionation for the characterization of macromolecules of biological interest: a review

PubMed Central

Qureshi, Rashid Nazir

2010-01-01

An overview is given of the recent literature on (bio) analytical applications of flow field-flow fractionation (FlFFF). FlFFF is a liquid-phase separation technique that can separate macromolecules and particles according to size. The technique is increasingly used on a routine basis in a variety of application fields. In food analysis, FlFFF is applied to determine the molecular size distribution of starches and modified celluloses, or to study protein aggregation during food processing. In industrial analysis, it is applied for the characterization of polysaccharides that are used as thickeners and dispersing agents. In pharmaceutical and biomedical laboratories, FlFFF is used to monitor the refolding of recombinant proteins, to detect aggregates of antibodies, or to determine the size distribution of drug carrier particles. In environmental studies, FlFFF is used to characterize natural colloids in water streams, and especially to study trace metal distributions over colloidal particles. In this review, first a short discussion of the state of the art in instrumentation is given. Developments in the coupling of FlFFF to various detection modes are then highlighted. Finally, application studies are discussed and ordered according to the type of (bio) macromolecules or bioparticles that are fractionated. PMID:20957473

Self-assembly in densely grafted macromolecules with amphiphilic monomer units: diagram of states.

PubMed

Lazutin, A A; Vasilevskaya, V V; Khokhlov, A R

2017-11-22

By means of computer modelling, the self-organization of dense planar brushes of macromolecules with amphiphilic monomer units was addressed and their state diagram was constructed. The diagram of states includes the following regions: disordered position of monomer units with respect to each other, strands composed of a few polymer chains and lamellae with different domain spacing. The transformation of lamellae structures with different domain spacing occurred within the intermediate region and could proceed through the formation of so-called parking garage structures. The parking garage structure joins the lamellae with large (on the top of the brushes) and small (close to the grafted surface) domain spacing, which appears like a system of inclined locally parallel layers connected with each other by bridges. The parking garage structures were observed for incompatible A and B groups in selective solvents, which result in aggregation of the side B groups and dense packing of amphiphilic macromolecules in the restricted volume of the planar brushes.

Polar Nature of Biomimetic Fluorapatite/Gelatin Composites: A Comparison of Bipolar Objects and the Polar State of Natural Tissue.

PubMed

Burgener, Matthias; Putzeys, Tristan; Gashti, Mazeyar Parvinzadeh; Busch, Susanne; Aboulfadl, Hanane; Wübbenhorst, Michael; Kniep, Rüdiger; Hulliger, Jürg

2015-09-14

The correspondence of the state of alignment of macromolecules in biomimetic materials and natural tissues is demonstrated by investigating a mechanism of electrical polarity formation: An in vitro grown biomimetic FAp/gelatin composite is investigated for its polar properties by second harmonic (SHGM) and scanning pyroelectric microscopy (SPEM). Hexagonal prismatic seed crystals formed in gelatin gels represent a monodomain polar state, due to aligned mineralized gelatin molecules. Later growth stages, showing dumbbell morphologies, develop into a bipolar state because of surface recognition by gelatin functionality: A reversal of the polar alignment of macromolecules, thus, takes place close to that basal plane of the seed. In natural hard tissues (teeth and bone investigated by SPEM) and the biomimetic FAp/gelatin composite, we find a surprising analogy in view of growth-induced states of polarity: The development of polarity in vivo and in vitro can be explained by a Markov-type mechanism of molecular recognition during the attachment of macromolecules.

Angle-Dependent Atomic Force Microscopy Single-Chain Pulling of Adsorbed Macromolecules from Planar Surfaces Unveils the Signature of an Adsorption-Desorption Transition.

PubMed

Grebíková, Lucie; Whittington, Stuart G; Vancso, Julius G

2018-05-23

The adsorption-desorption behavior of polymer chains is at the heart of macromolecular surface science and technology. With the current developments in atomic force microscopy (AFM), it has now become possible to address the desorption problem from the perspective of a single macromolecule. Here, we report on desorption of single polymer chains on planar surfaces by AFM-based single molecule force spectroscopy (SMFS) as a function of the pulling angle with respect to the surface-normal direction. SMFS experiments were performed in water with various substrates using different polymers covalently attached to the AFM probe tip. End-grafting at the AFM tip was achieved by surface-initiated polymerization using initiator functionalized tips. We found that the desorption force increases with a decreasing pulling angle, i.e., an enhanced adhesion of the polymer chain was observed. The magnitude of the desorption force shows a weak angular dependence at pulling angles close to the surface normal. A significant increase of the force is observed at shallower pulling from a certain pulling angle. This behavior carries the signature of an adsorption-desorption transition. The angular dependence of the normalized desorption force exhibits a universal behavior. We compared and interpreted our results using theoretical predictions for single-chain adsorption-desorption transitions.

Angle-Dependent Atomic Force Microscopy Single-Chain Pulling of Adsorbed Macromolecules from Planar Surfaces Unveils the Signature of an Adsorption–Desorption Transition

PubMed Central

2018-01-01

The adsorption–desorption behavior of polymer chains is at the heart of macromolecular surface science and technology. With the current developments in atomic force microscopy (AFM), it has now become possible to address the desorption problem from the perspective of a single macromolecule. Here, we report on desorption of single polymer chains on planar surfaces by AFM-based single molecule force spectroscopy (SMFS) as a function of the pulling angle with respect to the surface-normal direction. SMFS experiments were performed in water with various substrates using different polymers covalently attached to the AFM probe tip. End-grafting at the AFM tip was achieved by surface-initiated polymerization using initiator functionalized tips. We found that the desorption force increases with a decreasing pulling angle, i.e., an enhanced adhesion of the polymer chain was observed. The magnitude of the desorption force shows a weak angular dependence at pulling angles close to the surface normal. A significant increase of the force is observed at shallower pulling from a certain pulling angle. This behavior carries the signature of an adsorption–desorption transition. The angular dependence of the normalized desorption force exhibits a universal behavior. We compared and interpreted our results using theoretical predictions for single-chain adsorption–desorption transitions. PMID:29712430

International Symposium on Polymer Electrolytes (1st)

DTIC Science & Technology

1987-06-01

second order transitions, and chemical stability, e.g. dehydration or chemical decomposition . This is a powerful technique which can be used...References (M.Watanabe et. al) 1) Polym.J., 15, 65, 175 (1983). 2) Polym.J., 16, 711 (1984); 17, 549 (1985). 3) Macromolecules, 18, 1945 (1985). 4) Nippon...material is an organically modified silicate which gives, alter hydrolysis and condensation, an organic-inorganic glass. The silica network gives good

RNA-modifying proteins as anticancer drug targets.

PubMed

Boriack-Sjodin, P Ann; Ribich, Scott; Copeland, Robert A

2018-06-01

All major biological macromolecules (DNA, RNA, proteins and lipids) undergo enzyme-catalysed covalent modifications that impact their structure, function and stability. A variety of covalent modifications of RNA have been identified and demonstrated to affect RNA stability and translation to proteins; these mechanisms of translational control have been termed epitranscriptomics. Emerging data suggest that some epitranscriptomic mechanisms are altered in human cancers as well as other human diseases. In this Review, we examine the current understanding of RNA modifications with a focus on mRNA methylation, highlight their possible roles in specific cancer indications and discuss the emerging potential of RNA-modifying proteins as therapeutic targets.

Using time-of-flight secondary ion mass spectrometry and multivariate statistical analysis to detect and image octabenzyl-polyhedral oligomeric silsesquioxane in polycarbonate

NASA Astrophysics Data System (ADS)

Smentkowski, V. S.; Duong, H. M.; Tamaki, R.; Keenan, M. R.; Ohlhausen, J. A. Tony; Kotula, P. G.

2006-11-01

Silsesquioxane, with an empirical formula of RSiO3/2, has the potential to combine the mechanical properties of plastics with the oxidative stability of ceramics in one material [D.W. Scott, J. Am. Chem. Soc. 68 (1946) 356; K.J. Shea, D.A. Loy, Acc. Chem. Res. 34 (2001) 707; K.-M. Kim, D.-K. Keum, Y. Chujo, Macromolecules 36 (2003) 867; M.J. Abad, L. Barral, D.P. Fasce, R.J.J. William, Macromolecules 36 (2003) 3128]. The high sensitivity, surface specificity, and ability to detect and image high mass additives make time-of-flight secondary ion mass spectrometry (ToF-SIMS) a powerful surface analytical instrument for the characterization of polymer composite surfaces in an analytical laboratory [J.C. Vickerman, D. Briggs (Eds.), ToF-SIMS Surface Analysis by Mass Spectrometry, Surface Spectra/IMPublications, UK, 2001; X. Vanden Eynde, P. Bertand, Surf. Interface Anal. 27 (1999) 157; P.M. Thompson, Anal. Chem. 63 (1991) 2447; S.J. Simko, S.R. Bryan, D.P. Griffis, R.W. Murray, R.W. Linton, Anal. Chem. 57 (1985) 1198; S. Affrossman, S.A. O'Neill, M. Stamm, Macromolecules 31 (1998) 6280]. In this paper, we compare ToF-SIMS spectra of control samples with spectra generated from polymer nano-composites based on octabenzyl-polyhedral oligomeric silsesquioxane (BnPOSS) as well as spectra (and images) generated from multivariate statistical analysis (MVSA) of the entire spectral image. We will demonstrate that ToF-SIMS is able to detect and image low concentrations of BnPOSS in polycarbonate. We emphasize the use of MVSA tools for converting the massive amount of data contained in a ToF-SIMS spectral image into a smaller number of useful chemical components (spectra and images) that fully describe the ToF-SIMS measurement.

Clearance Properties of Nano-sized Particles and Molecules as Imaging Agents: Considerations and Caveats

PubMed Central

Longmire, Michelle; Choyke, Peter L.; Kobayashi, Hisataka

2009-01-01

Summary Nanoparticles possess enormous potential as diagnostic imaging agents and hold promise for the development of multimodality agents with both imaging and therapeutic capabilities. Yet, some of the most promising nanoparticles demonstrate prolonged tissue retention and contain heavy metals. This presents serious concerns for toxicity. The creation of nanoparticles with optimal clearance characteristics will minimize toxicity risks by reducing the duration of exposure to these agents. Given that many nanoparticles possess easily modifiable surface and interior chemistry, if nanoparticle characteristics associated with optimal clearance from the body were well established, it would be feasible to design and create agents with more favorable clearance properties. This paper presents a thorough discussion of the physiologic aspects of nanoparticle clearance, focusing on renal mechanisms, as well as provides an overview of current research investigating clearance of specific types of nanoparticles and nano-sized macromolecules, including dendrimers, quantum dots, liposomes and carbon, gold, and silica-based nanoparticles. PMID:18817471

Fabricating pH-stable and swellable very thin hyperbranched poly(ethylene imine)-oligosaccharide films fabricated without precoating: first view on protein adsorption.

PubMed

Warenda, Monika; Richter, Anne; Schmidt, Diana; Janke, Andreas; Müller, Martin; Simon, Frank; Zimmermann, Ralf; Eichhorn, Klaus-Jochen; Voit, Brigitte; Appelhans, Dietmar

2012-09-14

For using successful (ultra)thin dendritic macromolecule films in (bio)sensing and microfluidic devices and for obtaining reproducible film properties, alteration effects arising from precoatings have to be avoided. Here, oligosaccharide-modified hyperbranched poly(ethylene imine)s (PEI-OS) were used to fabricate very thin PEI-OS films (15-20 nm in dry state), cross-linked with citric acid under condensation, and vacuum condition. However, no reactive precoating is necessary to obtain stable films, which allows very simple film preparation and avoids alteration of the PEIS-OS film properties arising from precoating. Several methods [(in situ) ellipsometry, AFM, XPS, (in situ) ATR-IR, streaming potential measurements] were applied to characterize homogeneity, surface morphology, and stability of these PEI-OS films between pH 2 and pH 10, but also the low protein adsorption behavior. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large volume continuous counterflow dialyzer has high efficiency

NASA Technical Reports Server (NTRS)

Mandeles, S.; Woods, E. C.

1967-01-01

Dialyzer separates macromolecules from small molecules in large volumes of solution. It takes advantage of the high area/volume ratio in commercially available 1/4-inch dialysis tubing and maintains a high concentration gradient at the dialyzing surface by counterflow.

A rapid and practical technique for real-time monitoring of biomolecular interactions using mechanical responses of macromolecules

NASA Astrophysics Data System (ADS)

Tarhan, Mehmet C.; Lafitte, Nicolas; Tauran, Yannick; Jalabert, Laurent; Kumemura, Momoko; Perret, Grégoire; Kim, Beomjoon; Coleman, Anthony W.; Fujita, Hiroyuki; Collard, Dominique

2016-06-01

Monitoring biological reactions using the mechanical response of macromolecules is an alternative approach to immunoassays for providing real-time information about the underlying molecular mechanisms. Although force spectroscopy techniques, e.g. AFM and optical tweezers, perform precise molecular measurements at the single molecule level, sophisticated operation prevent their intensive use for systematic biosensing. Exploiting the biomechanical assay concept, we used micro-electro mechanical systems (MEMS) to develop a rapid platform for monitoring bio/chemical interactions of bio macromolecules, e.g. DNA, using their mechanical properties. The MEMS device provided real-time monitoring of reaction dynamics without any surface or molecular modifications. A microfluidic device with a side opening was fabricated for the optimal performance of the MEMS device to operate at the air-liquid interface for performing bioassays in liquid while actuating/sensing in air. The minimal immersion of the MEMS device in the channel provided long-term measurement stability (>10 h). Importantly, the method allowed monitoring effects of multiple solutions on the same macromolecule bundle (demonstrated with DNA bundles) without compromising the reproducibility. We monitored two different types of effects on the mechanical responses of DNA bundles (stiffness and viscous losses) exposed to pH changes (2.1 to 4.8) and different Ag+ concentrations (1 μM to 0.1 M).

The role of energetic ions from plasma in the creation of nanostructured materials and stable polymer surface treatments

NASA Astrophysics Data System (ADS)

Bilek, M. M. M.; Newton-McGee, K.; McKenzie, D. R.; McCulloch, D. G.

2006-01-01

Plasma processes for the synthesis of new materials as thin films have enabled the production of a wide variety of new materials. These include meta-stable phases, which are not readily found in nature, and more recently, materials with structure on the nanoscale. Study of plasma synthesis processes at the fundamental level has revealed that ion energy, depositing flux and growth surface temperature are the critical parameters affecting the microstructure and the properties of the thin film materials formed. In this paper, we focus on the role of ion flux and impact energy in the creation of thin films with nanoscale structure in the form of multilayers. We describe three synthesis strategies, based on the extraction of ions from plasma sources and involving modulation of ion flux and ion energy. The microstructure, intrinsic stress and physical properties of the multilayered samples synthesized are studied and related back to the conditions at the growth surface during deposition. When energetic ions of a non-condensing species are used, it is possible to place active groups on the surfaces of materials such as polymers. These active groups can then be used as bonding sites in subsequent chemical attachment of proteins or other macromolecules. If the energy of the non-condensing ions is increased to a few keV then modified layers buried under the surface can be produced. Here we describe a method by which the aging effect, which is often observed in plasma surface modifications on polymers, can be reduced and even eliminated using high energy ion bombardment.

Enhancement of Cell Membrane Invaginations, Vesiculation and Uptake of Macromolecules by Protonation of the Cell Surface

PubMed Central

Ben-Dov, Nadav; Korenstein, Rafi

2012-01-01

The different pathways of endocytosis share an initial step involving local inward curvature of the cell’s lipid bilayer. It has been shown that to generate membrane curvature, proteins or lipids enforce transversal asymmetry of the plasma membrane. Thus it emerges as a general phenomenon that transversal membrane asymmetry is the common required element for the formation of membrane curvature. The present study demonstrates that elevating proton concentration at the cell surface stimulates the formation of membrane invaginations and vesiculation accompanied by efficient uptake of macromolecules (Dextran-FITC, 70 kD), relative to the constitutive one. The insensitivity of proton induced uptake to inhibiting treatments and agents of the known endocytic pathways suggests the entry of macromolecules to proceeds via a yet undefined route. This is in line with the fact that neither ATP depletion, nor the lowering of temperature, abolishes the uptake process. In addition, fusion mechanism such as associated with low pH uptake of toxins and viral proteins can be disregarded by employing the polysaccharide dextran as the uptake molecule. The proton induced uptake increases linearly in the extracellular pH range of 6.5 to 4.5, and possesses a steep increase at the range of 4> pH>3, reaching a plateau at pH≤3. The kinetics of the uptake implies that the induced vesicles release their content to the cytosol and undergo rapid recycling to the plasma membrane. We suggest that protonation of the cell’s surface induces local charge asymmetries across the cell membrane bilayer, inducing inward curvature of the cell membrane and consequent vesiculation and uptake. PMID:22558127

Controlled method of reducing electrophoretic mobility of various substances

NASA Technical Reports Server (NTRS)

Vanalstine, James M. (Inventor)

1989-01-01

A method of reducing electrophoretic mobility of macromolecules, particles, cells, and the like is provided. The method comprises interacting the particles or cells with a polymer-linked affinity compound composed of: a hydrophilic neutral polymer such as polyethylene glycol, and an affinity component consisting of a hydrophobic compound such as a fatty acid ester, an immunocompound such as an antibody or active fragment thereof or simular macromolecule, or other ligands. The reduction of electrophoretic mobility achieved is directly proportional to the concentration of the polymer-linked affinity compound employed, and the mobility reduction obtainable is up to 100 percent for particular particles and cells. The present invention is advantageous in that analytical electrophoretic separation can not be achieved for macromolecules, particles, and cells whose native surface charge structure had prevented them from being separated by normal electrophoretic means. Depending on the affinity component utilized, separation can be achieved on the basis of specific/irreversible, specific/reversible, semi-specific/reversible, relatively nonspecific/reversible, or relatively nonspecific/irreversible ligand-substance interactions. The present method is also advantageous in that it can be used in a variety of standard laboratory electrophoresis equipment.

Effect of Osmolytes on the Conformational Behavior of a Macromolecule in a Cytoplasm-like Crowded Environment: A Femtosecond Mid-IR Pump-Probe Spectroscopy Study.

PubMed

Kundu, Achintya; Verma, Pramod Kumar; Cho, Minhaeng

2018-02-15

Osmolytes found endogenously in almost all living beings play an important role in regulating cell volume under harsh environment. Here, to address the longstanding questions about the underlying mechanism of osmolyte effects, we use femtosecond mid-IR pump-probe spectroscopy with two different IR probes that are the OD stretching mode of HDO and the azido stretching mode of azido-derivatized poly(ethylene glycol) dimethyl ether (PEGDME). Our experimental results show that protecting osmolytes bind strongly with water molecules and dehydrate polymer surface, which results in promoting intramolecular interactions of the polymer. By contrast, urea behaves like water molecules without significantly disrupting water H-bonding network and favors extended and random-coil segments of the polymer chain by directly participating in solvation of the polymer. Our findings highlight the importance of direct interaction between urea and macromolecule, while protecting osmolytes indirectly affect the macromolecule through enhancing the water-osmolyte interaction in a crowded environment, which is the case that is often encountered in real biological systems.

Fluid Physics and Macromolecular Crystal Growth in Microgravity

NASA Technical Reports Server (NTRS)

Pusey, M.; Snell, E.; Judge, R.; Chayen, N.; Boggon, T.

2000-01-01

The molecular structure of biological macromolecules is important in understanding how these molecules work and has direct application to rational drug design for new medicines and for the improvement and development of industrial enzymes. In order to obtain the molecular structure, large, well formed, single macromolecule crystals are required. The growth of macromolecule crystals is a difficult task and is often hampered on the ground by fluid flows that result from the interaction of gravity with the crystal growth process. One such effect is the bulk movement of the crystal through the fluid due to sedimentation. A second is buoyancy driven convection close to the crystal surface. On the ground the crystallization process itself induces both of these flows. Buoyancy driven convection results from density differences between the bulk solution and fluid close to the crystal surface which has been depleted of macromolecules due to crystal growth. Schlieren photograph of a growing lysozyme crystal illustrating a 'growth plume' resulting from buoyancy driven convection. Both sedimentation and buoyancy driven convection have a negative effect on crystal growth and microgravity is seen as a way to both greatly reduce sedimentation and provide greater stability for 'depletion zones' around growing crystals. Some current crystal growth hardware however such as those based on a vapor diffusion techniques, may also be introducing unwanted Marangoni convection which becomes more pronounced in microgravity. Negative effects of g-jitter on crystal growth have also been observed. To study the magnitude of fluid flows around growing crystals we have attached a number of different fluorescent probes to lysozyme molecules. At low concentrations, less than 40% of the total protein, the probes do not appear to effect the crystal growth process. By using these probes we expect to determine not only the effect of induced flows due to crystal growth hardware design but also hope to optimize crystallization hardware so that destructive flows are minimized both on the ground and in microgravity.

Long charged macromolecule in an entropic trap with rough surfaces.

PubMed

Mamasakhlisov, Yevgeni Sh; Hayryan, Shura; Hu, Chin-Kun

2012-11-01

The kinetics of the flux of a charged macromolecular solution through an environment of changing geometry with wide and constricted regions is investigated analytically. A model device consisting of alternating deep and shallow slits known as an "entropic trap" is used to represent the environment. The flux is supported by the external electrostatic field. The "wormlike chain" model is used for the macromolecule (dsDNA in the present study). The chain entropy in both the deep and the shallow slits, the work by the electric field, and the energy of the elastic bending of the chain are taken into account accurately. Based on the calculated free energy, the kinetics and the scaling behavior of the chain escaping from the entropic trap are studied. We find that the escape process occurs in two kinetic stages with different time scales and discuss the possible influence of the surface roughness. The scope of the accuracy of the proposed model is discussed.

Flow-induced conformational changes in gelatin structure and colloidal stabilization.

PubMed

Akbulut, Mustafa; Reddy, Naveen K; Bechtloff, Bernd; Koltzenburg, Sebastian; Vermant, Jan; Prud'homme, Robert K

2008-09-02

Flow can change the rate at which solutes adsorb on surfaces by changing mass transfer to the surface, but moreover, flow can induce changes in the conformation of macromolecules in solution by providing sufficient stresses to perturb the segmental distribution function. However, there are few studies where the effect of flow on macromolecules has been shown to alter the structure of macromolecules adsorbed on surfaces. We have studied how the local energy dissipation alters the adsorption of gelatin onto polystyrene nanoparticles ( r = 85 nm). The change in the nature of the adsorbed layer is manifest in the change in the ability of the nanoparticles to resist aggregation. Circular dichroism spectroscopy was used to assess conformational changes in gelatin, and dynamic light scattering was used to assess the colloid stability. Experiments were conducted in a vortex jet mixer where energy density and mixing times have been quantified; mixing of the gelatin and unstable nanoparticles occurs on the order of milliseconds. The adsorption of the gelatin provides steric stabilization to the nanoparticles. We found that the stability of the gelatin-adsorbed nanoparticles increased with increasing mixing velocities: when the mixing velocities were changed from 0.9 to 550 m/s, the radius of the nanoclusters (aggregates) formed 12 h after the mixing decreased from 2620 to 600 nm. Increasing temperature also gave rise to similar trends in the stability behavior with increasing temperature, leading to increasing colloid stability. Linear flow birefringence studies also suggested that the velocity fields in the mixer are sufficiently strong to produce conformational changes in the gelatin. These results suggest that the energy dissipation produced by mixing can activate conformational changes in gelatin to alter its adsorption on the surfaces of nanoparticles. Understanding how such conformational changes in gelatin can be driven by local fluid mechanics and how these changes are related to the adsorption behavior of gelatin is very important both industrially and scientifically.

Nanometer-scale structure of alkali-soluble bio-macromolecules of maize plant residues explains their recalcitrance in soil.

PubMed

Adani, Fabrizio; Salati, Silvia; Spagnol, Manuela; Tambone, Fulvia; Genevini, Pierluigi; Pilu, Roberto; Nierop, Klaas G J

2009-07-01

The quantity and quality of plant litter in the soil play an important role in the soil organic matter balance. Besides other pedo-climatic aspects, the content of recalcitrant molecules of plant residues and their chemical composition play a major role in the preservation of plant residues. In this study, we report that intrinsically resistant alkali-soluble bio-macromolecules extracted from maize plant (plant-humic acid) (plant-HA) contribute directly to the soil organic matter (OM) by its addition and conservation in the soil. Furthermore, we also observed that a high syringyl/guaiacyl (S/G) ratio in the lignin residues comprising the plant tissue, which modifies the microscopic structure of the alkali-soluble plant biopolymers, enhances their recalcitrance because of lower accessibility of molecules to degrading enzymes. These results are in agreement with a recent study, which showed that the humic substance of soil consists of a mixture of identifiable biopolymers obtained directly from plant tissues that are added annually by maize plant residues.

Induced liquid-crystalline ordering in solutions of stiff and flexible amphiphilic macromolecules: Effect of mixture composition

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

Glagolev, Mikhail K.; Vasilevskaya, Valentina V., E-mail: vvvas@polly.phys.msu.ru; Khokhlov, Alexei R.

Impact of mixture composition on self-organization in concentrated solutions of stiff helical and flexible macromolecules was studied by means of molecular dynamics simulation. The macromolecules were composed of identical amphiphilic monomer units but a fraction f of macromolecules had stiff helical backbones and the remaining chains were flexible. In poor solvents the compacted flexible macromolecules coexist with bundles or filament clusters from few intertwined stiff helical macromolecules. The increase of relative content f of helical macromolecules leads to increase of the length of helical clusters, to alignment of clusters with each other, and then to liquid-crystalline-like ordering along a singlemore » direction. The formation of filament clusters causes segregation of helical and flexible macromolecules and the alignment of the filaments induces effective liquid-like ordering of flexible macromolecules. A visual analysis and calculation of order parameter relaying the anisotropy of diffraction allow concluding that transition from disordered to liquid-crystalline state proceeds sharply at relatively low content of stiff components.« less

Investigation of chemical modifications of micro- and macromolecules in bio-oil during hydrodeoxygenation with Pd/C catalyst in supercritical ethanol.

PubMed

Oh, Shinyoung; Hwang, Hyewon; Choi, Hang Seok; Choi, Joon Weon

2014-12-01

Miscanthus bio-oil was subjected to hydrodeoxygenation (HDO) with Pd/C at different temperatures (250, 300 and 350°C) and times (30, 45 and 60 min) to investigate the chemical modification of micro- and macromolecules in bio-oil. Four main products - char, gas and two immiscible oils (light and heavy oil) - were obtained from the HDO reaction. Yields of heavy oil as a targeting product of HDO varied from 60% to 13%, whereas those of gas and char were ranged from 7% to 36% and 6% to 17%, respectively. Water content was estimated to<1% and heating value was 26-31 MJ kg(-1). Reduction of unstable oxygen-containing compounds such as acids (2-hydroxy-butanoic acid), aldehydes (furfural), alcohols (butanedial) and sugars (levoglucosan) were characteristic in heavey oil. Apart from hydrogenation and deoxygenation, micromolecules in bio-oil were plausibly modified to stable ketones, esters and saturated components via demethoxylation, dealkylation, decarbonylation, dehydroxylation and ring opening. Macromolecular lignin fragments (referred to as pyrolytic lignins in bio-oil and phenol polymers in heavy oil) were extracted and subjected to several analyses. Approximately 60% of the pyrolytic lignins were decomposed into low molecular weight compounds during HDO reaction. Moreover, essential functional groups, OCH3 and phen-OH groups attached to pyrolytic lignin, were severely modified during HDO reaction. Copyright © 2014 Elsevier Ltd. All rights reserved.

Preparation and Characterization of Thermoresponsive Poly(N-isopropylacrylamide-co-acrylic acid)-Grafted Hollow Fe3O4/SiO2 Microspheres with Surface Holes for BSA Release

PubMed Central

Zhao, Jing; Zeng, Ming; Zheng, Kaiqiang; He, Xinhua; Xie, Minqiang; Fu, Xiaoyi

2017-01-01

Thermoresponsive P(NIPAM-AA)/Fe3O4/SiO2 microspheres with surface holes serving as carriers were prepared using p-Fe3O4/SiO2 microspheres with a thermoresponsive copolymer. The p-Fe3O4/SiO2 microspheres was obtained using a modified Pickering method and chemical etching. The surface pore size of p-Fe3O4/SiO2 microspheres was in the range of 18.3 nm~37.2 nm and the cavity size was approximately 60 nm, which are suitable for loading and transporting biological macromolecules. P(NIPAM-AA) was synthesized inside and outside of the p-Fe3O4/SiO2 microspheres via atom transfer radical polymerization of NIPAM, MBA and AA. The volume phase transition temperature (VPTT) of the specifically designed P(NIPAM-AA)/Fe3O4/SiO2 microspheres was 42.5 °C. The saturation magnetization of P(NIPAM-AA)/Fe3O4/SiO2 microspheres was 72.7 emu/g. The P(NIPAM-AA)/Fe3O4/SiO2 microspheres were used as carriers to study the loading and release behavior of BSA. This microsphere system shows potential for the loading of proteins as a drug delivery platform. PMID:28772770

Correlative atomic force microscopy quantitative imaging-laser scanning confocal microscopy quantifies the impact of stressors on live cells in real-time.

PubMed

Bhat, Supriya V; Sultana, Taranum; Körnig, André; McGrath, Seamus; Shahina, Zinnat; Dahms, Tanya E S

2018-05-29

There is an urgent need to assess the effect of anthropogenic chemicals on model cells prior to their release, helping to predict their potential impact on the environment and human health. Laser scanning confocal microscopy (LSCM) and atomic force microscopy (AFM) have each provided an abundance of information on cell physiology. In addition to determining surface architecture, AFM in quantitative imaging (QI) mode probes surface biochemistry and cellular mechanics using minimal applied force, while LSCM offers a window into the cell for imaging fluorescently tagged macromolecules. Correlative AFM-LSCM produces complimentary information on different cellular characteristics for a comprehensive picture of cellular behaviour. We present a correlative AFM-QI-LSCM assay for the simultaneous real-time imaging of living cells in situ, producing multiplexed data on cell morphology and mechanics, surface adhesion and ultrastructure, and real-time localization of multiple fluorescently tagged macromolecules. To demonstrate the broad applicability of this method for disparate cell types, we show altered surface properties, internal molecular arrangement and oxidative stress in model bacterial, fungal and human cells exposed to 2,4-dichlorophenoxyacetic acid. AFM-QI-LSCM is broadly applicable to a variety of cell types and can be used to assess the impact of any multitude of contaminants, alone or in combination.

Development of a novel monoclonal antibody against 4-hydroxy-2E,6Z-dodecadienal (4-HDDE)-protein adducts: Immunochemical application in quantitative and qualitative analyses of lipid peroxidation in vitro and ex vivo.

PubMed

Uchida, Koji; Shibata, Takahiro; Toyokuni, Shinya; Daniel, Bareket; Zarkovic, Kamelija; Zarkovic, Neven; Sasson, Shlomo

2018-05-25

Non-enzymatic peroxidation of polyunsaturated fatty acids (PUFA) results in the formation of various α,β-unsaturated aldehydes, of which 4-hydroxyalkenals are abundant. The propensity of n-6 PUFA, such as linoleic acid, γ-linolenic acid and arachidonic acid, to undergo radical-induced peroxidation and generate 4-hydroxy-2E-nonenal (4-HNE) has been widely demonstrated. The ability of the latter to form covalent adducts with macromolecules and modify cellular functions has been linked to numerous pathological processes. Concomitantly, evidence has accumulated on specific signaling properties of low concentrations of 4-HNE that may induce hormetic and protective responses to peroxidation stress in cells. It has long been known that peroxidation of PUFA, and particularly arachidonic acid, also give rise to 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), which is more chemically reactive than 4-HNE. Few studies on 4-HDDE revealed its ability to avidly interact covalently with electronegative moieties in macromolecules and to its ability to selectively activate the transcriptional regulator Peroxisome Proliferator-Activated Receptor (PPAR)-β/δ. The research on 4-HDDE has been impeded due to the lack of available pure 4-HDDE and antibodies that recognize 4-HDDE-modified epitopes in proteins. The purpose of this study was to employ an established procedure to synthesize 4-HDDE and use it to create and characterize a monoclonal antibody against 4-HDDE-modified proteins and establish its application for ELISA and immunohistochemical analysis of cells and tissues and further expand lipid peroxidation research. Copyright © 2018 Elsevier Inc. All rights reserved.

Molecular modifiers reveal a mechanism of pathological crystal growth inhibition

NASA Astrophysics Data System (ADS)

Chung, Jihae; Granja, Ignacio; Taylor, Michael G.; Mpourmpakis, Giannis; Asplin, John R.; Rimer, Jeffrey D.

2016-08-01

Crystalline materials are crucial to the function of living organisms, in the shells of molluscs, the matrix of bone, the teeth of sea urchins, and the exoskeletons of coccoliths. However, pathological biomineralization can be an undesirable crystallization process associated with human diseases. The crystal growth of biogenic, natural and synthetic materials may be regulated by the action of modifiers, most commonly inhibitors, which range from small ions and molecules to large macromolecules. Inhibitors adsorb on crystal surfaces and impede the addition of solute, thereby reducing the rate of growth. Complex inhibitor-crystal interactions in biomineralization are often not well elucidated. Here we show that two molecular inhibitors of calcium oxalate monohydrate crystallization—citrate and hydroxycitrate—exhibit a mechanism that differs from classical theory in that inhibitor adsorption on crystal surfaces induces dissolution of the crystal under specific conditions rather than a reduced rate of crystal growth. This phenomenon occurs even in supersaturated solutions where inhibitor concentration is three orders of magnitude less than that of the solute. The results of bulk crystallization, in situ atomic force microscopy, and density functional theory studies are qualitatively consistent with a hypothesis that inhibitor-crystal interactions impart localized strain to the crystal lattice and that oxalate and calcium ions are released into solution to alleviate this strain. Calcium oxalate monohydrate is the principal component of human kidney stones and citrate is an often-used therapy, but hydroxycitrate is not. For hydroxycitrate to function as a kidney stone treatment, it must be excreted in urine. We report that hydroxycitrate ingested by non-stone-forming humans at an often-recommended dose leads to substantial urinary excretion. In vitro assays using human urine reveal that the molecular modifier hydroxycitrate is as effective an inhibitor of nucleation of calcium oxalate monohydrate nucleation as is citrate. Our findings support exploration of the clinical potential of hydroxycitrate as an alternative treatment to citrate for kidney stones.

Mechanics of the Adhesive Properties of Ivy Nanoparticles

DTIC Science & Technology

2013-11-21

macromolecule with multiple physiological functions in the growth of plants, such as signaling, cell wall plasticizer, guiding pollen tube growth, and many...others. The AGPs on the stigma surface were believed to act as an adhesive base for pollens , indicating the adhesion function that AGPs play in plants

Orienting the Microstructure Evolution of Copper Phthalocyanine as an Anode Interlayer in Inverted Polymer Solar Cells for High Performance.

PubMed

Li, Zhiqi; Liu, Chunyu; Zhang, Xinyuan; Li, Shujun; Zhang, Xulin; Guo, Jiaxin; Guo, Wenbin; Zhang, Liu; Ruan, Shengping

2017-09-20

Recent advances in the interfacial modification of inverted-type polymer solar cells (PSCs) have resulted from controlling the surface energy of the cathode-modified layer (TiO 2 or ZnO) to enhance the short-circuit current (J sc ) or optimizing the contact morphology of the cathode (indium tin oxide or fluorine-doped tin oxide) and active layer to increase the fill factor. Herein, we report that the performance enhancement of PSCs is achieved by incorporating a donor macromolecule copper phthalocyanine (CuPc) as an anode modification layer. Using the approach based on orienting the microstructure evolution, uniformly dispersed island-shaped CuPc spot accumulations are built on the top of PTB7:PC 71 BM blend film, leading to an efficient spectral absorption and photogenerated exciton splitting. The best power conversion efficiency of PSCs is increased up to 9.726%. In addition to the enhanced light absorption, the tailored anode energy level alignment and optimized boundary morphology by incorporating the CuPc interlayer boost charge extraction efficiency and suppress the interfacial molecular recombination. These results demonstrate that surface morphology induction through molecular deposition is an effective method to improve the performance of PSCs, which reveals the potential implications of the interlayer between the organic active layer and the electrode buffer layer.

Pulmonary vascular clearance of harmful endogenous macromolecules in a porcine model of acute liver failure.

PubMed

Nedredal, Geir I; Elvevold, Kjetil; Chedid, Marcio F; Ytrebø, Lars M; Rose, Christopher F; Sen, Sambit; Smedsrød, Bård; Jalan, Rajiv; Revhaug, Arthur

2016-01-01

Pulmonary complications are common in acute liver failure (ALF). The role of the lungs in the uptake of harmful soluble endogenous macromolecules was evaluated in a porcine model of ALF induced by hepatic devascularization (n = 8) vs. controls (n = 8). In additional experiments, pulmonary uptake was investigated in healthy pigs. Fluorochrome-labeled modified albumin (MA) was applied to investigate the cellular uptake. As compared to controls, the ALF group displayed a 4-fold net increased lung uptake of hyaluronan, and 5-fold net increased uptake of both tissue plasminogen activator and lysosomal enzymes. Anatomical distribution experiments in healthy animals revealed that radiolabeled MA uptake (taken up by the same receptor as hyaluronan) was 53% by the liver, and 24% by the lungs. The lung uptake of LPS was 14% whereas 60% remained in the blood. Both fluorescence and electron microscopy revealed initial uptake of MA by pulmonary endothelial cells (PECs) with later translocation to pulmonary intravascular macrophages (PIMs). Moreover, the presence of PIMs was evident 10 min after injection. Systemic inflammatory markers such as leukopenia and increased serum TNF-α levels were evident after 20 min in the MA and LPS groups. Significant lung uptake of harmful soluble macromolecules compensated for the defect liver scavenger function in the ALF-group. Infusion of MA induced increased TNF-α serum levels and leukopenia, similar to the effect of the known inflammatory mediator LPS. These observations suggest a potential mechanism that may contribute to lung damage secondary to liver disease.

The Ice Nucleation Activity of Surface Modified Soot

NASA Astrophysics Data System (ADS)

Häusler, Thomas; Witek, Lorenz; Felgitsch, Laura; Hitzenberger, Regina; Grothe, Hinrich

2017-04-01

The ice nucleation efficiency of many important atmospheric particles remains poorly understood. Since soot is ubiquitous in the Earth's troposphere, they might have the potential to significantly impact the Earth's climate (Finlayson-Pitts and Pitts, 2000; Seinfeld and Pandis, 1998). Here we present the ice nucleation activity (INA) in immersion freezing mode of different types of soot. Therefor a CAST (combustion aerosol standard) generator was used to produce different kinds of soot samples. The CAST generator combusts a propane-air-mixture and deposits thereby produced soot on a polyvinyl fluoride filter. By varying the propane to air ratio, the amount of organic portion of the soot can be varied from black carbon (BC) with no organic content to brown carbon (BrC) with high organic content. To investigate the impact of functional sites of ice nuclei (IN), the soot samples were exposed to NO2 gas for a certain amount of time (30 to 360 minutes) to chemically modify the surface. Immersion freezing experiments were carried out in a unique reaction gadget. In this device a water-in-oil suspension (with the soot suspended in the aqueous phase) was cooled till the freezing point and was observed through a microscope (Pummer et al., 2012; Zolles et al., 2015) It was found that neither modified nor unmodified BC shows INA. On the contrary, unmodified BrC shows an INA at -32˚ C, which can be increased up to -20˚ C. The INA of BrC depends on the duration of NO2- exposure. To clarify the characteristics of the surface modifications, surface sensitive analysis like infrared spectroscopy and X-ray photoelectron spectroscopy were carried out. Finlayson-Pitts, B. J. and Pitts, J. N. J.: Chemistry of the Upper and Lower Atmosphere, Elsevier, New York, 2000. Pummer, B. G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos Chem Phys, 12, 2541-2550, 2012. Seinfeld, J. H. and Pandis, S. N.: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, Wiley-Interscience, N. J., 1998. Zolles, T., Burkart, J., Hausler, T., Pummer, B., Hitzenberger, R., and Grothe, H.: Identification of Ice Nucleation Active Sites on Feldspar Dust Particles, Journal of Physical Chemistry A, 119, 2692-2700, 2015.

Highly Regioregular Polythiophenes for Magneto-Optical Applications

DTIC Science & Technology

2010-07-01

Macromolecules, 2007, 40, 8142-8150 Lieven De Cremer et.al., Macromolecules, 2008, 41, 568-578 Lieven De Cremer et.al., Macromolecules, 2008, 41, 591-598 Marnix...Vangheluwe et.al., Macromolecules, 2008, 41, 1041-1044 David Cornelis et.al., Chem. Mater. 2008, 20, 2133-2143 Palash Gangopadhyay et.al., J. Phys

Lessons from a Stone Farm

NASA Astrophysics Data System (ADS)

Kavanagh, John P.; Rao, P. Nagaraj

2007-04-01

The stone farm is a system for measuring macroscopic stone growth of 12 calcium stones simultaneously. It is based on mixed suspension, mixed product removal continuous crystallization principles and the stones are grown continuously for about 500 hours or more. The growth of the stones follows a surface area dependent pattern and the growth rate constants are very similar irrespective of whether the stating materials are fragments of human stone or pieces of marble chip. Increasing citrate from 2mM to 6mM caused a significant growth inhibition which persisted in the presence of urinary macromolecules. Phytate was a very effective inhibitor (about 50% at sub-μM concentrations) but the effective concentration was increased by an order of magnitude in the presence of urinary macromolecules. The effective concentration for inhibition in a crystallization assay was a further two orders of magnitude higher. Urinary macromolecules or almost whole urine were also strongly inhibitory although neither human serum albumin nor bovine mucin had any great effect. The relationship between the size distribution of crystals in suspension and the stone enlargement rate suggests that the primary enlargement mechanism for these in vitro stones is through aggregation. The stone farm is a powerful tool with which to study crystallization inhibitors in a new light. Some differences between inhibition of crystallization and inhibition of stone growth have emerged and we have obtained quantitative evidence on the mechanism of stone enlargement in vitro. Our findings suggest that the interface between crystals in suspension and the stone surface is the key to controlling stone enlargement.

Robust hydrophobic polyurethane fibrous membranes with tunable porous structure for waterproof and breathable application

NASA Astrophysics Data System (ADS)

Gu, Jiatai; Gu, Haihong; Cao, Jin; Chen, Shaojie; Li, Ni; Xiong, Jie

2018-05-01

In this work, novel nanofibrous membranes with waterproof and breathable (W&B) performance were successfully fabricated by the combination of electrospinning and surface modification technology. This fibrous membranes consisted of polyurethane (PU), NaCl, and fluoroalkylsilane (FAS). Firstly, The fibrous construction and porous structure of fibrous membranes were regulated by tuning the NaCl concentrations in PU solutions. Then, the obtained PU/NaCl fibrous membranes were further modified with fluoroalkylsilane (FAS) to improve hydrophobic property. The synergistic effect of porous structure and hydrophobicity on waterproof and breathable performance was investigated. Furthermore, the mechanical property of fibrous membranes was deeply analysed on the basis of macromolecule orientation and adhesive structure. Benefiting from the optimized porous structure and hydrophobic modification, the resultant fibrous membranes exhibited excellent waterproof (hydrostatic pressure of 1261 Mbar), breathable (water vapor transmission (WVT) rate of 9.06 kg m-2 d-1 and air permeability of 4.8 mm s-1) performance, as well as high tensile strength (breakage stress of 10.4 MPa), suggesting a promising candidate for various applications, especially in protective clothing.

Macromolecules Inquiry: Transformation of a Standard Biochemistry Lab

ERIC Educational Resources Information Center

Unsworth, Elizabeth

2014-01-01

Identification of macromolecules in food is a standard introductory high school biology lab. The intent of this article is to describe the conversion of this standard cookbook lab into an inquiry investigation. Instead of verifying the macromolecules found in food, students use their knowledge of the macromolecules in food to determine the…

Robust Plasma Polymerized-Titania/Silica Janus Microparticles

DTIC Science & Technology

2010-04-29

vladimir@mse.gatech.edu. (1) De Gennes, P. G. Rev. Mod. Phys. 1992, 64, 645. (2) Perro , A.; Reculusa, S.; Ravaine, S.; Bourgeat-Lami, E.; Duguet, E. J. Mater...Rubner,M. F.; Cohen, R. E.Macromolecules 2005, 38, 7876. (12) Perro ,A.;Meunier, F.; Schmitt, V.;Ravaine, S.Colloid. Surface.A. 2009, 332, 57. (13

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.

Will ethylene oxide sterilization influence the application of novel Cu/LDPE nanocomposite intrauterine devices?

PubMed

Xia, Xianping; Wang, Yun; Cai, Shuizhou; Xie, Changsheng; Zhu, Changhong

2009-01-01

Copper/low-density polyethylene (Cu/LDPE) nanocomposite intrauterine device (IUD) is an implanted medicinal device that must be sterilized before use. Sterilization processes act either chemically or physically, leading to a lethal change in the structure or function of organic macromolecules in microorganisms. Given the nature of their action, sterilization might also attack the macromolecules of polymers by the same mechanisms, resulting in changes in surface functional groups and in the internal structure of the polymer. If sterilization leads to changes in surface functional groups and in the internal structure of the LDPE matrix, which will influence the mechanical property and cupric ions release rate of novel Cu/LDPE nanocomposite IUDs, potential clinical application will be limited. Therefore, it is necessary to study the influence of ethylene oxide sterilization on the potential clinical application of novel Cu/LDPE nanocomposite IUDs. The influence of ethylene oxide sterilization on the internal structure, surface functional groups, mechanical property and cupric ions release rate of novel Cu/LDPE nanocomposite IUDs was studied using differential scanning calorimetry, attenuated total reflection Fourier transform infrared spectroscopy, tensile testing and absorbance measurement. Ethylene oxide sterilization did not have any influence on the internal structure, surface functional groups, mechanical property and cupric ions release rate of novel Cu/LDPE nanocomposite intrauterine devices. Ethylene oxide sterilization will not affect the potential application of novel Cu/LDPE nanocomposite IUDs.

Efficient gaussian density formulation of volume and surface areas of macromolecules on graphical processing units.

PubMed

Zhang, Baofeng; Kilburg, Denise; Eastman, Peter; Pande, Vijay S; Gallicchio, Emilio

2017-04-15

We present an algorithm to efficiently compute accurate volumes and surface areas of macromolecules on graphical processing unit (GPU) devices using an analytic model which represents atomic volumes by continuous Gaussian densities. The volume of the molecule is expressed by means of the inclusion-exclusion formula, which is based on the summation of overlap integrals among multiple atomic densities. The surface area of the molecule is obtained by differentiation of the molecular volume with respect to atomic radii. The many-body nature of the model makes a port to GPU devices challenging. To our knowledge, this is the first reported full implementation of this model on GPU hardware. To accomplish this, we have used recursive strategies to construct the tree of overlaps and to accumulate volumes and their gradients on the tree data structures so as to minimize memory contention. The algorithm is used in the formulation of a surface area-based non-polar implicit solvent model implemented as an open source plug-in (named GaussVol) for the popular OpenMM library for molecular mechanics modeling. GaussVol is 50 to 100 times faster than our best optimized implementation for the CPUs, achieving speeds in excess of 100 ns/day with 1 fs time-step for protein-sized systems on commodity GPUs. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Nanotribology of charged polymer brushes

NASA Astrophysics Data System (ADS)

Klein, Jacob

Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.

Effect of plasticizer on surface of free films prepared from aqueous solutions of salts of cationic polymers with different plasticizers

NASA Astrophysics Data System (ADS)

Bajdik, János; Fehér, Máté; Pintye-Hódi, Klára

2007-06-01

Acquisition of a more detailed understanding of all technological processes is currently a relevant tendency in pharmaceutical technology and hence in industry. A knowledge of film formation from dispersion of polymers is very important during the coating of solid dosage forms. This process and the structure of the film can be influenced by different additives. In the present study, taste-masking films were prepared from aqueous citric acid solutions of a cationic polymer (Eudragit ® E PO) with various hydrophilic plasticizers (glycerol, propylene glycol and different poly(ethylene glycols)). The mechanical properties, film thickness, wetting properties and surface free energy of the free films were studied. The aim was to evaluate the properties of surface of free films to predict the arrangement of macromolecules in films formed from aqueous solutions of salts of cationic polymers. A high molecular weight of the plasticizer decreased the work of deformation. The surface free energy and the polarity were highest for the film without plasticizer; the hydrophilic additives decreased these parameters. The direction of the change in polarity (a hydrophilic component caused a decrease in the polarity) was unexpected. It can be explained by the change in orientation of the macromolecules, a hydrophobic surface being formed. Examination of the mechanical properties and film thickness can furnish additional results towards a knowledge of film formation by this not frequently applied type of polymer from aqueous solution.

Molecular surface mesh generation by filtering electron density map.

PubMed

Giard, Joachim; Macq, Benoît

2010-01-01

Bioinformatics applied to macromolecules are now widely spread and in continuous expansion. In this context, representing external molecular surface such as the Van der Waals Surface or the Solvent Excluded Surface can be useful for several applications. We propose a fast and parameterizable algorithm giving good visual quality meshes representing molecular surfaces. It is obtained by isosurfacing a filtered electron density map. The density map is the result of the maximum of Gaussian functions placed around atom centers. This map is filtered by an ideal low-pass filter applied on the Fourier Transform of the density map. Applying the marching cubes algorithm on the inverse transform provides a mesh representation of the molecular surface.

Influence of hesperidin on renal cell surface glycoprotein content, nucleic acids, lysosomal enzymes and macromolecules against 7, 12-dimethylbenz [a] anthracene induced experimental breast carcinoma.

PubMed

Nandakumar, Natarajan; Jayaprakash, Ramachandran; Balasubramanian, Maruthaiveeran Periyasamy

2012-01-01

Therapeutic substances may reduce the risk of developing cancer by modulating the factors responsible for carcinogenesis. To evaluate these hypotheses, the present study was designed to investigate the modulatory effect of bioflavonoid "Hesperidin" against DMBA induced experimental breast cancer with reference to renal cell surface glycoproteins, nucleic acids, protein content, lipid profile and lysosomal enzymes. The female sprague-dawley rats were orally administered with single dose of 7, 12-DMBA to induce breast cancer and were treated with hesperidin [30 mg/kg/body weight] for a consecutive 45 days. The results revealed that there was a significant elevation in the levels of glycoproteins, nucleic acids, lysosomal enzymes and also significant alterations in macromolecules in renal tissues of cancer bearing animals. Interestingly, the altered levels of these parameters were remarkably reverted back to near normal in hesperidin treatment. The histopathological analysis of liver and kidney tissues were well supported the biochemical alterations and inevitably proves the protective role of hesperidin. It is proposed that, the effect of hesperidin during DMBA induced breast cancer could be due to the intervention strategies of hesperidin in the protein, nucleic acid biosynthesis, membrane stabilizing potentials on lysosomal compartment and inhibitory effect on cell surface glycoproteins and bio-fuel such as lipids.

Effects of hydration on steric and electric charge-induced interstitial volume exclusion--a model.

PubMed

Øien, Alf H; Justad, Sigrid R; Tenstad, Olav; Wiig, Helge

2013-09-03

The presence of collagen and charged macromolecules like glycosaminoglycans (GAGs) in the interstitial space limits the space available for plasma proteins and other macromolecules. This phenomenon, known as interstitial exclusion, is of importance for interstitial fluid volume regulation. Physical/mathematical models are presented for calculating the exclusion of electrically charged and neutral macromolecules that equilibrate in the interstitium under various degrees of hydration. Here, a central hypothesis is that the swelling of highly electrically charged GAGs with increased hydration shields parts of the neutral collagen of the interstitial matrix from interacting with electrically charged macromolecules, such that exclusion of charged macromolecules exhibits change due to steric and charge effects. GAGs are also thought to allow relatively small neutral, but also charged macromolecules neutralized by a very high ionic strength, diffuse into the interior of GAGs, whereas larger macromolecules may not. Thus, in the model, relatively small electrically charged macromolecules, such as human serum albumin, and larger neutral macromolecules such as IgG, will have quite similar total volume exclusion properties in the interstitium. Our results are in agreement with ex vivo and in vivo experiments, and suggest that the charge of GAGs or macromolecular drugs may be targeted to increase the tissue uptake of macromolecular therapeutic agents. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

INFLUENCE OF MACROMOLECULES ON CHEMICAL TRANSPORT

EPA Science Inventory

Macromolecules in the pore fluid influence the mobility of hydrophobic compounds through soils. his study evaluated the significance of macromolecules in facilitating chemical transport under laboratory conditions. Partition coefficients between 14C-labeled hexachlorobenzene and ...

Anti-Arrhenius cleavage of covalent bonds in bottlebrush macromolecules on substrate.

PubMed

Lebedeva, Natalia V; Nese, Alper; Sun, Frank C; Matyjaszewski, Krzysztof; Sheiko, Sergei S

2012-06-12

Spontaneous degradation of bottlebrush macromolecules on aqueous substrates was monitored by atomic force microscopy. Scission of C ─ C covalent bonds in the brush backbone occurred due to steric repulsion between the adsorbed side chains, which generated bond tension on the order of several nano-Newtons. Unlike conventional chemical reactions, the rate of bond scission was shown to decrease with temperature. This apparent anti-Arrhenius behavior was caused by a decrease in the surface energy of the underlying substrate upon heating, which results in a corresponding decrease of bond tension in the adsorbed macromolecules. Even though the tension dropped minimally from 2.16 to 1.89 nN, this was sufficient to overpower the increase in the thermal energy (k(B)T) in the Arrhenius equation. The rate constant of the bond-scission reaction was measured as a function of temperature and surface energy. Fitting the experimental data by a perturbed Morse potential V = V(0)(1 - e(-βx))(2) - fx, we determined the depth and width of the potential to be V(0) = 141 ± 19 kJ/mol and β(-1) = 0.18 ± 0.03 Å, respectively. Whereas the V(0) value is in reasonable agreement with the activation energy E(a) = 80-220 kJ/mol of mechanical and thermal degradation of organic polymers, it is significantly lower than the dissociation energy of a C ─ C bond D(e) = 350 kJ/mol. Moreover, the force constant K(x) = 2β(2)V(0) = 1.45 ± 0.36 kN/m of a strained bottlebrush along its backbone is markedly larger than the force constant of a C ─ C bond K(l) = 0.44 kN/m, which is attributed to additional stiffness due to deformation of the side chains.

Micropore surface area of alkali-soluble plant macromolecules (humic acids) drives their decomposition rates in soil.

PubMed

Papa, Gabriella; Spagnol, Manuela; Tambone, Fulvia; Pilu, Roberto; Scaglia, Barbara; Adani, Fabrizio

2010-02-01

Previous studies suggested that micropore surface area (MSA) of alkali-soluble bio-macromolecules of aerial plant residues of maize constitutes an important factor that explains their humification in soil, that is, preservation against biological degradation. On the other hand, root plant residue contributes to the soil humus balance, as well. Following the experimental design used in a previous paper published in this journal, this study shows that the biochemical recalcitrance of the alkali-soluble acid-insoluble fraction of the root plant material, contributed to the root maize humification of both Wild-type maize plants and its corresponding mutant brown midrib (bm3), this latter characterized by reduced lignin content. Humic acids (HAs) existed in root (root-HAs) were less degraded in soil than corresponding HAs existed in shoot (shoot-HAs): shoot-HAs bm3 (48%)>shoot-HAs Wild-type (37%)>root-HAs Wild-type (33%)>root-HAs bm3 (22%) (degradability shown in parenthesis). These differences were related to the MSA of HAs, that is, root-HAs having a higher MSA than shoot-HAs: shoot-HAs bm3 (41.43+/-1.2m(2)g(-1))

Glycan Engineering for Cell and Developmental Biology.

PubMed

Griffin, Matthew E; Hsieh-Wilson, Linda C

2016-01-21

Cell-surface glycans are a diverse class of macromolecules that participate in many key biological processes, including cell-cell communication, development, and disease progression. Thus, the ability to modulate the structures of glycans on cell surfaces provides a powerful means not only to understand fundamental processes but also to direct activity and elicit desired cellular responses. Here, we describe methods to sculpt glycans on cell surfaces and highlight recent successes in which artificially engineered glycans have been employed to control biological outcomes such as the immune response and stem cell fate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impacts of Organic Macromolecules, Chlorophyll and Soot on Arctic Sea Ice

NASA Astrophysics Data System (ADS)

Ogunro, O. O.; Wingenter, O. W.; Elliott, S.; Flanner, M.; Dubey, M. K.

2014-12-01

Recent intensification of Arctic amplification can be strongly connected to positive feedback relating black carbon deposition to sea ice surface albedo. In addition to soot deposition on the ice and snow pack, ice algal chlorophyll is likely to compete as an absorber and redistributor of energy. Hence, solar radiation absorption by chlorophyll and some components of organic macromolecules in/under the ice column is currently being examined to determine the level of influence on predicted rate of ice loss. High amounts of organic macromolecules and chlorophyll are produced in global sea ice by the bottom microbial community and also in vertically distributed layers where substantial biological activities take place. Brine channeling in columnar ice can allow for upward flow of nutrients which leads to greater primary production in the presence of moderate light. Modeling of the sea-ice processes in tandem with experiments and field observations promises rapid progress in enhancing Arctic ice predictions. We are designing and conducting global climate model experiments to determine the impact of organic macromolecules and chlorophyll on Arctic sea ice. Influences on brine network permeability and radiation/albedo will be considered in this exercise. Absorption by anthropogenic materials such as soot and black carbon will be compared with that of natural pigments. We will indicate areas of soot and biological absorption dominance in the sense of single scattering, then couple into a full radiation transfer scheme to attribute the various contributions to polar climate change amplification. The work prepares us to study more traditional issues such as chlorophyll warming of the pack periphery and chemical effects of the flow of organics from ice internal communities. The experiments started in the Arctic will broaden to include Antarctic sea ice and shelves. Results from the Arctic simulations will be presented.

Chemical and Conformational Diversity of Modified Nucleosides Affects tRNA Structure and Function.

PubMed

Väre, Ville Y P; Eruysal, Emily R; Narendran, Amithi; Sarachan, Kathryn L; Agris, Paul F

2017-03-16

RNAs are central to all gene expression through the control of protein synthesis. Four major nucleosides, adenosine, guanosine, cytidine and uridine, compose RNAs and provide sequence variation, but are limited in contributions to structural variation as well as distinct chemical properties. The ability of RNAs to play multiple roles in cellular metabolism is made possible by extensive variation in length, conformational dynamics, and the over 100 post-transcriptional modifications. There are several reviews of the biochemical pathways leading to RNA modification, but the physicochemical nature of modified nucleosides and how they facilitate RNA function is of keen interest, particularly with regard to the contributions of modified nucleosides. Transfer RNAs (tRNAs) are the most extensively modified RNAs. The diversity of modifications provide versatility to the chemical and structural environments. The added chemistry, conformation and dynamics of modified nucleosides occurring at the termini of stems in tRNA's cloverleaf secondary structure affect the global three-dimensional conformation, produce unique recognition determinants for macromolecules to recognize tRNAs, and affect the accurate and efficient decoding ability of tRNAs. This review will discuss the impact of specific chemical moieties on the structure, stability, electrochemical properties, and function of tRNAs.

Surface modification of strontium-doped porous bioactive ceramic scaffolds via poly(DOPA) coating and immobilizing silk fibroin for excellent angiogenic and osteogenic properties.

PubMed

Wang, Xu; Gu, Zhipeng; Jiang, Bo; Li, Li; Yu, Xixun

2016-04-01

For bioceramic scaffolds employed in clinical applications, excellent bioactivity and tenacity were of great importance. Modifying inorganic SCPP scaffolds with biological macromolecules could obviously improve its bioactivity and eliminate its palpable brittleness. However, it was hard to execute directly due to extremely bad interfacial compatibility between them. In this research, dopamine (DOPA) was introduced onto strontium-doped calcium polyphosphate (SCPP) scaffolds, subsequently the preliminary material was successfully further modified by silk fibroin (SF). SCPP/D/SF possessed suitable biomechanical properties, ability to stimulate angiogenic factor secretion and excellent biocompatibility. Biomechanical examination demonstrated that SCPP/D/SF scaffolds yielded better compressive strength because of improved interfacial compatibility. MTT assay and CLSM observation showed that SCPP/D/SF scaffolds had good cytocompatibility and presented better inducing-cell-migration potential than pure SCPP scaffolds. Meanwhile, its ability to stimulate angiogenic factor secretion was measured through the ELISA assay and immunohistological analysis in vitro and in vivo respectively. The results revealed, superior to SCPP, SCPP/D/SF could effectively promote VEGF and bFGF expression, possibly leading to enhancing angiogenesis and osteogenesis. In a word, SCPP/D/SF could serve as a potential bone tissue engineering scaffold for comparable biomechanical properties and excellent bioactivity. It provided a novel idea for modification of inorganic materials to prepare promising bone tissue engineering scaffolds with the ability to accelerate bone regeneration and vascularization.

Physical effects at the cellular level under altered gravity conditions

NASA Technical Reports Server (NTRS)

Todd, Paul

1992-01-01

Several modifications of differentiated functions of animal cells cultivated in vitro have been reported when cultures have been exposed to increased or decreased inertial acceleration fields by centrifugation, clinorotation, and orbital space flight. Variables modified by clinorotation conditions include inertial acceleration, convection, hydrostatic pressure, sedimentation, and shear stress, which also affect transport processes in the extracellular chemical environment. Autocrine, paracrine and endocrine substances, to which cells are responsive via specific receptors, are usually transported in vitro (and possibly in certain embryos) by convection and in vivo by a circulatory system or ciliary action. Increased inertial acceleration increases convective flow, while microgravity nearly abolishes it. In the latter case the extracellular transport of macromolecules is governed by diffusion. By making certain assumptions it is possible to calculate the Peclet number, the ratio of convective transport to diffusive transport. Some, but not all, responses of cells in vitro to modified inertial environments could be manifestations of modified extracellular convective flow.

Contact Kinetics in Fractal Macromolecules.

PubMed

Dolgushev, Maxim; Guérin, Thomas; Blumen, Alexander; Bénichou, Olivier; Voituriez, Raphaël

2015-11-13

We consider the kinetics of first contact between two monomers of the same macromolecule. Relying on a fractal description of the macromolecule, we develop an analytical method to compute the mean first contact time for various molecular sizes. In our theoretical description, the non-Markovian feature of monomer motion, arising from the interactions with the other monomers, is captured by accounting for the nonequilibrium conformations of the macromolecule at the very instant of first contact. This analysis reveals a simple scaling relation for the mean first contact time between two monomers, which involves only their equilibrium distance and the spectral dimension of the macromolecule, independently of its microscopic details. Our theoretical predictions are in excellent agreement with numerical stochastic simulations.

Interfacial properties of hydrosoluble polymers. Final report, June 15, 1993--June 15, 1996

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

NONE

1996-12-31

During this period, the authors treated a myriad of problems associated with the interfacial properties of macromolecules. Many of them concerned indirect interactions between surfaces engendered by intervening species. The issues ranged from colloidal forces to membrane induced coupling between embedded macromolecules (membrane-bound proteins). This report presents summaries of the following papers published as a result of this study: membrane interactions with polymers and colloids; escape transitions and force laws for compressed polymer mushrooms; interaction between finite-sized particles and end grafted polymers; one long chain among shorter chains--the Flory approach revisited; conformation of star polymers in high molecular weight solvents;more » membrane-induced interactions between inclusions; filled polymer brushes--a hydrodynamic analogy; polymer adsorption at liquid/air interfaces under lateral pressure; flow induced instability of the interface between a fluid and a gel at low Reynolds number; and fluctuation-induced forces in stacked fluid membranes.« less

Molecular interactions in a surfactant-water-polyacrylamide system, according to densimetry, viscometry, conductometry, and spectroscopy data

NASA Astrophysics Data System (ADS)

Harutyunyan, R. S.

2013-08-01

Molecular interactions in a surfactant-polyacrylamide-water system are investigated. It is established that the interactions affect such physicochemical parameters of the system as viscosity, density, surface tension, conductivity, and critical micelle concentration. It is shown that in a polyacrylamide-water system, raising the polyacrylamide concentration to 0.02% causes conformational changes in its macromolecule.

Effective protection of biological membranes against photo-oxidative damage: Polymeric antioxidant forming a protecting shield over the membrane.

PubMed

Mertins, Omar; Mathews, Patrick D; Gomide, Andreza B; Baptista, Mauricio S; Itri, Rosangela

2015-10-01

We have prepared a chitosan polymer modified with gallic acid in order to develop an efficient protection strategy biological membranes against photodamage. Lipid bilayers were challenged with photoinduced damage by photosensitization with methylene blue, which usually causes formation of hydroperoxides, increasing area per lipid, and afterwards allowing leakage of internal materials. The damage was delayed by a solution of gallic acid in a concentration dependent manner, but further suppressed by the polymer at very low concentrations. The membrane of giant unilamellar vesicles was covered with this modified macromolecule leading to a powerful shield against singlet oxygen and thus effectively protecting the lipid membrane from oxidative stress. The results have proven the discovery of a promising strategy for photo protection of biological membranes. Copyright © 2015 Elsevier B.V. All rights reserved.

MACROMOLECULES FACILITATE THE TRANSPORT OF TRACE ORGANICS

EPA Science Inventory

Macromolecules in the pore fluid of a soil may influence the mobility of hydrophobic compounds by their partitioning to the macromolecule, which moves with, or even faster than, the water. The mobility is described mathematically by a chemical transport model. The significance of...

Observation of chain stretching in Langmuir diblock copolymer monolayers

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

Factor, B.J.; Lee, L.; Kent, M.S.

1993-10-01

We report observations of chain stretching in diblock copolymer monolayers on the surface of a selective solvent. Using neutron reflectivity, we have studied the concentration profile of the submerged block over a large range of surface density [sigma] (chains per area) for two different molecular weights. The observed increase in the layer thickness is weaker than the [sigma][sup 1/3] prediction of mean-field and scaling theories for the limiting behavior, but is in agreement with recent numerical self-consistent-field calculations by Whitmore and Noolandi [Macromolecules 23, 3321 (1990)].

Carbohydrates, proteins, cell surfaces, and the biochemistry of pathogenesis

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

Albersheim, P.; Anderson-Prouty, A.J.

1975-01-01

General plant resistance to pathogenic attack by a myriad of microorganisms, viruses, nematodes, and insects are reviewed. Specifically discussed are: The role of the cell wall and wall-degrading enzymes in infective processes; an hypothesis to account for varietal specificity in gene-for-gene host-pathogen systems; examples which demonstrate that cell surface recognition phenomena are mediated through the interaction of carbohydrate-containing macromolecules and proteins; elicitors of phytoalexin production; and further consideration of the hypothesis and how the gene-for-gene relationship may have evolved. (JWP)

Systematic analysis of barrier-forming FG hydrogels from Xenopus nuclear pore complexes

PubMed Central

Labokha, Aksana A; Gradmann, Sabine; Frey, Steffen; Hülsmann, Bastian B; Urlaub, Henning; Baldus, Marc; Görlich, Dirk

2013-01-01

Nuclear pore complexes (NPCs) control the traffic between cell nucleus and cytoplasm. While facilitating translocation of nuclear transport receptors (NTRs) and NTR·cargo complexes, they suppress passive passage of macromolecules ⩾30 kDa. Previously, we reconstituted the NPC barrier as hydrogels comprising S. cerevisiae FG domains. We now studied FG domains from 10 Xenopus nucleoporins and found that all of them form hydrogels. Related domains with low FG motif density also substantially contribute to the NPC's hydrogel mass. We characterized all these hydrogels and observed the strictest sieving effect for the Nup98-derived hydrogel. It fully blocks entry of GFP-sized inert objects, permits facilitated entry of the small NTR NTF2, but arrests importin β-type NTRs at its surface. O-GlcNAc modification of the Nup98 FG domain prevented this arrest and allowed also large NTR·cargo complexes to enter. Solid-state NMR spectroscopy revealed that the O-GlcNAc-modified Nup98 gel lacks amyloid-like β-structures that dominate the rigid regions in the S. cerevisiae Nsp1 FG hydrogel. This suggests that FG hydrogels can assemble through different structural principles and yet acquire the same NPC-like permeability. PMID:23202855

Involvement of specific macrophage-lineage cells surrounding arterioles in barrier and scavenger function in brain cortex.

PubMed Central

Mato, M; Ookawara, S; Sakamoto, A; Aikawa, E; Ogawa, T; Mitsuhashi, U; Masuzawa, T; Suzuki, H; Honda, M; Yazaki, Y; Watanabe, E; Luoma, J; Yla-Herttuala, S; Fraser, I; Gordon, S; Kodama, T

1996-01-01

The transport of solutes between blood and brain is regulated by a specific barrier. Capillary endothelial cells of brain are known to mediate barrier function and facilitate transport. Here we report that specific cells surrounding arterioles, known as Mato's fluorescent granular perithelial (FGP) cells or perivascular microglial cells, contribute to the barrier function. Immunohistochemical and in situ hybridization studies indicate that, in normal brain cortex, type I and type II macrophage scavenger receptors are expressed only in FGP/perivascular microglial cells, and surface markers of macrophage lineage are also detected on them. These cells mediate the uptake of macromolecules, including modified low density lipoprotein, horseradish peroxidase, and ferritin injected either into the blood or into the cerebral ventricles. Accumulation of scavenged materials with aging or after the administration of a high-fat diet results in the formation of honeycomb-like foam cells and the narrowing of the lumen of arterioles in the brain cortex. These results indicate involvement of FGP/perivascular microglial cells in the barrier and scavenger functions in the central nervous system. Images Fig. 1 Fig. 2 Fig. 4 Fig. 5 Fig. 6 PMID:8622926

Structured Water Layers Adjacent to Biological Membranes

PubMed Central

Higgins, Michael J.; Polcik, Martin; Fukuma, Takeshi; Sader, John E.; Nakayama, Yoshikazu; Jarvis, Suzanne P.

2006-01-01

Water amid the restricted space of crowded biological macromolecules and at membrane interfaces is essential for cell function, though the structure and function of this “biological water” itself remains poorly defined. The force required to remove strongly bound water is referred to as the hydration force and due to its widespread importance, it has been studied in numerous systems. Here, by using a highly sensitive dynamic atomic force microscope technique in conjunction with a carbon nanotube probe, we reveal a hydration force with an oscillatory profile that reflects the removal of up to five structured water layers from between the probe and biological membrane surface. Further, we find that the hydration force can be modified by changing the membrane fluidity. For 1,2-dipalmitoyl-sn-glycero-3-phosphocholine gel (Lβ) phase bilayers, each oscillation in the force profile indicates the force required to displace a single layer of water molecules from between the probe and bilayer. In contrast, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine fluid (Lα) phase bilayers at 60°C and 1,2-dioleoyl-sn-glycero-3-phosphocholine fluid (Lα) phase bilayers at 24°C seriously disrupt the molecular ordering of the water and result predominantly in a monotonic force profile. PMID:16798815

Recent advancement of gelatin nanoparticles in drug and vaccine delivery.

PubMed

Sahoo, Nityananda; Sahoo, Ranjan Ku; Biswas, Nikhil; Guha, Arijit; Kuotsu, Ketousetuo

2015-11-01

Novel drug delivery system using nanoscale materials with a broad spectrum of applications provides a new therapeutic foundation for technological integration and innovation. Nanoparticles are suitable drug carrier for various routes of administration as well as rapid recognition by the immune system. Gelatin, the biological macromolecule is a versatile drug/vaccine delivery carrier in pharmaceutical field due to its biodegradable, biocompatible, non-antigenicity and low cost with easy availability. The surface of gelatin nanoparticles can be modified with site-specific ligands, cationized with amine derivatives or, coated with polyethyl glycols to achieve targeted and sustained release drug delivery. Compared to other colloidal carriers, gelatin nanoparticles are better stable in biological fluids to provide the desired controlled and sustained release of entrapped drug molecules. The current review highlights the different formulation aspects of gelatin nanoparticles which affect the particle characteristics like zeta potential, polydispersity index, entrapment efficacy and drug release properties. It has also given emphasis on the major applications of gelatin nanoparticles in drug and vaccine delivery, gene delivery to target tissues and nutraceutical delivery for improving the poor bioavailabity of bioactive phytonutrients. Copyright © 2015 Elsevier B.V. All rights reserved.

Organometallic macromolecules with piano stool coordination repeating units: chain configuration and stimulated solution behaviour.

PubMed

Cao, Kai; Ward, Jonathan; Amos, Ryan C; Jeong, Moon Gon; Kim, Kyoung Taek; Gauthier, Mario; Foucher, Daniel; Wang, Xiaosong

2014-09-11

Theoretical calculations illustrate that organometallic macromolecules with piano stool coordination repeating units (Fe-acyl complex) adopt linear chain configuration with a P-Fe-C backbone surrounded by aromatic groups. The macromolecules show molecular weight-dependent and temperature stimulated solution behaviour in DMSO.

Noise reduction methods for nucleic acid and macromolecule sequencing

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

Schuller, Ivan K.; Di Ventra, Massimiliano; Balatsky, Alexander

Methods, systems, and devices are disclosed for processing macromolecule sequencing data with substantial noise reduction. In one aspect, a method for reducing noise in a sequential measurement of a macromolecule comprising serial subunits includes cross-correlating multiple measured signals of a physical property of subunits of interest of the macromolecule, the multiple measured signals including the time data associated with the measurement of the signal, to remove or at least reduce signal noise that is not in the same frequency and in phase with the systematic signal contribution of the measured signals.

Quantification of in vivo short echo-time proton magnetic resonance spectra at 14.1 T using two different approaches of modelling the macromolecule spectrum

NASA Astrophysics Data System (ADS)

Cudalbu, C.; Mlynárik, V.; Xin, L.; Gruetter, Rolf

2009-10-01

Reliable quantification of the macromolecule signals in short echo-time 1H MRS spectra is particularly important at high magnetic fields for an accurate quantification of metabolite concentrations (the neurochemical profile) due to effectively increased spectral resolution of the macromolecule components. The purpose of the present study was to assess two approaches of quantification, which take the contribution of macromolecules into account in the quantification step. 1H spectra were acquired on a 14.1 T/26 cm horizontal scanner on five rats using the ultra-short echo-time SPECIAL (spin echo full intensity acquired localization) spectroscopy sequence. Metabolite concentrations were estimated using LCModel, combined with a simulated basis set of metabolites using published spectral parameters and either the spectrum of macromolecules measured in vivo, using an inversion recovery technique, or baseline simulated by the built-in spline function. The fitted spline function resulted in a smooth approximation of the in vivo macromolecules, but in accordance with previous studies using Subtract-QUEST could not reproduce completely all features of the in vivo spectrum of macromolecules at 14.1 T. As a consequence, the measured macromolecular 'baseline' led to a more accurate and reliable quantification at higher field strengths.

New Directions in Biotechnology

NASA Technical Reports Server (NTRS)

2003-01-01

The macromolecule crystallization program within NASA is undergoing considerable pressure, particularly budgetary pressure. While it has shown some successes, they have not lived up to the expectations of others, and technological advances may rapidly overtake the natural advantages offered by crystallization in microgravity. Concomitant with the microgravity effort has been a research program to study the macromolecule crystallization process. It was believed that a better understanding of the process would lead to growth of improved crystals for X-ray diffraction studies. The results of the various research efforts have been impressive in improving our understanding of macromolecule crystallization, but have not led to any improved structures. Macromolecule crystallization for structure determination is "one of", the job being unique for every protein and finished once a structure is obtained. However, the knowledge gained is not lost, but instead lays the foundation for developments in new areas of biotechnology and nanotechnology. In this it is highly analogous to studies into small molecule crystallization, the results of which have led to our present day microelectronics-based society. We are conducting preliminary experiments into areas such as designed macromolecule crystals, macromolecule-inorganic hybrid structures, and macromolecule-based nanotechnology. In addition, our protein crystallization studies are now being directed more towards industrial and new approaches to membrane protein crystallization.

Rapid Brownian Motion Primes Ultrafast Reconstruction of Intrinsically Disordered Phe-Gly Repeats Inside the Nuclear Pore Complex.

PubMed

Moussavi-Baygi, R; Mofrad, M R K

2016-07-29

Conformational behavior of intrinsically disordered proteins, such as Phe-Gly repeat domains, alters drastically when they are confined in, and tethered to, nan channels. This has challenged our understanding of how they serve to selectively facilitate translocation of nuclear transport receptor (NTR)-bearing macromolecules. Heterogeneous FG-repeats, tethered to the NPC interior, nonuniformly fill the channel in a diameter-dependent manner and adopt a rapid Brownian motion, thereby forming a porous and highly dynamic polymeric meshwork that percolates in radial and axial directions and features two distinguishable zones: a dense hydrophobic rod-like zone located in the center, and a peripheral low-density shell-like zone. The FG-meshwork is locally disrupted upon interacting with NTR-bearing macromolecules, but immediately reconstructs itself between 0.44 μs and 7.0 μs, depending on cargo size and shape. This confers a perpetually-sealed state to the NPC, and is solely due to rapid Brownian motion of FG-repeats, not FG-repeat hydrophobic bonds. Elongated-shaped macromolecules, both in the presence and absence of NTRs, penetrate more readily into the FG-meshwork compared to their globular counterparts of identical volume and surface chemistry, highlighting the importance of the shape effects in nucleocytoplasmic transport. These results can help our understanding of geometrical effects in, and the design of, intelligent and responsive biopolymer-based materials in nanofiltration and artificial nanopores.

Ordered mesoporous polymer-silica hybrid nanoparticles as vehicles for the intracellular controlled release of macromolecules.

PubMed

Kim, Tae-Wan; Slowing, Igor I; Chung, Po-Wen; Lin, Victor Shang-Yi

2011-01-25

A two-dimensional hexagonal ordered mesoporous polymer-silica hybrid nanoparticle (PSN) material was synthesized by polymerization of acrylate monomers on the surface of SBA-15 mesoporous silica nanoparticles. The structure of the PSN material was analyzed using a series of different techniques, including transmission electron microscopy, powder X-ray diffraction, and N(2) sorption analysis. These structurally ordered mesoporous polymer-silica hybrid nanoparticles were used for the controlled release of membrane-impermeable macromolecules inside eukaryotic cells. The cellular uptake efficiency and biocompatibility of PSN with human cervical cancer cells (HeLa) were investigated. Our results show that the inhibitory concentration (IC(50)) of PSN is very high (>100 μg/mL per million cells), while the median effective concentration for the uptake (EC(50)) of PSN is low (EC(50) = 4.4 μg/mL), indicating that PSNs are fairly biocompatible and easily up-taken in vitro. A membrane-impermeable macromolecule, 40 kDa FITC-Dextran, was loaded into the mesopores of PSNs at low pH. We demonstrated that the PSN material could indeed serve as a transmembrane carrier for the controlled release of FITC-Dextran at the pH level inside live HeLa cells. We believe that further developments of this PSN material will lead to a new generation of nanodevices for intracellular controlled delivery applications.

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.

Distributions of phytoplankton carbohydrate, protein and lipid in the world oceans from satellite ocean colour.

PubMed

Roy, Shovonlal

2018-06-01

Energy value of phytoplankton regulates the growth of higher trophic species, affecting the tropic balance and sustainability of marine food webs. Therefore, developing our capability to estimate and monitor, on a global scale, the concentrations of macromolecules that determine phytoplankton energy value, would be invaluable. Reported here are the first estimates of carbohydrate, protein, lipid, and overall energy value of phytoplankton in the world oceans, using ocean-colour data from satellites. The estimates are based on a novel bio-optical method that utilises satellite-derived bio-optical fingerprints of living phytoplankton combined with allometric relationships between phytoplankton cells and cellular macromolecular contents. The annually averaged phytoplankton energy value, per cubic metre of sub-surface ocean, varied from less than 0.1 kJ in subtropical gyres, to 0.5-1.0 kJ in parts of the equatorial, northern and southern latitudes, and rising to >10 kJ in certain coastal and optically complex waters. The annually averaged global stocks of carbohydrate, protein and lipid were 0.044, 0.17 and 0.108 gigatonnes, respectively, with monthly stocks highest in September and lowest in June, over 1997-2013. The fractional contributions of phytoplankton size classes e.g., picoplankton, nanoplankton and microplankton to surface concentrations and global stocks of macromolecules varied considerably across marine biomes classified as Longhurst provinces. Among these provinces, the highest annually averaged surface concentrations of carbohydrate, protein, and lipid were in North-East Atlantic Coastal Shelves, whereas, the lowest concentration of carbohydrate or lipid were in North Atlantic Tropical Gyral, and that of protein was in North Pacific Subtropical Gyre West. The regional accuracy of the estimates and their sensitivity to satellite inputs are quantified from the bio-optical model, which show promise for possible operational monitoring of phytoplankton energy value from satellite ocean colour. Adequate in situ measurements of macromolecules and improved retrievals of inherent optical properties from high-resolution satellite images, would be required to validate these estimates at local sites, and to further improve their accuracy in the world oceans.

Characterization of Nylon 6 by 15N Solid State NMR

DTIC Science & Technology

1989-05-31

M.; Ritchey, W.; de Boer, E. Macromolecules, 1979, 12, 924. 2. Garroway , A. N.; Ritchey, W. M.; Moniz, W. B.; Macromolecules, 1982, It, 1051. 3...E. Macromolecules, 1982, 15, 1406. 23. Veeman, W. S.; Menger, E. M. Bull. Magn. Reson., 1980,2,77. 24. VanderHart, D. L.; Garroway , A. N. J. Chem

Macromolecule diffusion and confinement in prokaryotic cells.

PubMed

Mika, Jacek T; Poolman, Bert

2011-02-01

We review recent observations on the mobility of macromolecules and their spatial organization in live bacterial cells. We outline the major fluorescence microscopy-based methods to determine the mobility and thus the diffusion coefficients (D) of molecules, which is not trivial in small cells. The extremely high macromolecule crowding of prokaryotes is used to rationalize the reported lower diffusion coefficients as compared to eukaryotes, and we speculate on the nature of the barriers for diffusion observed for proteins (and mRNAs) in vivo. Building on in vitro experiments and modeling studies, we evaluate the size dependence of diffusion coefficients for macromolecules in vivo, in case of both water-soluble and integral membrane proteins. We comment on the possibilities of anomalous diffusion and provide examples where the macromolecule mobility may be limiting biological processes. Copyright © 2010 Elsevier Ltd. All rights reserved.

Small molecule annotation for the Protein Data Bank

PubMed Central

Sen, Sanchayita; Young, Jasmine; Berrisford, John M.; Chen, Minyu; Conroy, Matthew J.; Dutta, Shuchismita; Di Costanzo, Luigi; Gao, Guanghua; Ghosh, Sutapa; Hudson, Brian P.; Igarashi, Reiko; Kengaku, Yumiko; Liang, Yuhe; Peisach, Ezra; Persikova, Irina; Mukhopadhyay, Abhik; Narayanan, Buvaneswari Coimbatore; Sahni, Gaurav; Sato, Junko; Sekharan, Monica; Shao, Chenghua; Tan, Lihua; Zhuravleva, Marina A.

2014-01-01

The Protein Data Bank (PDB) is the single global repository for three-dimensional structures of biological macromolecules and their complexes, and its more than 100 000 structures contain more than 20 000 distinct ligands or small molecules bound to proteins and nucleic acids. Information about these small molecules and their interactions with proteins and nucleic acids is crucial for our understanding of biochemical processes and vital for structure-based drug design. Small molecules present in a deposited structure may be attached to a polymer or may occur as a separate, non-covalently linked ligand. During curation of a newly deposited structure by wwPDB annotation staff, each molecule is cross-referenced to the PDB Chemical Component Dictionary (CCD). If the molecule is new to the PDB, a dictionary description is created for it. The information about all small molecule components found in the PDB is distributed via the ftp archive as an external reference file. Small molecule annotation in the PDB also includes information about ligand-binding sites and about covalent and other linkages between ligands and macromolecules. During the remediation of the peptide-like antibiotics and inhibitors present in the PDB archive in 2011, it became clear that additional annotation was required for consistent representation of these molecules, which are quite often composed of several sequential subcomponents including modified amino acids and other chemical groups. The connectivity information of the modified amino acids is necessary for correct representation of these biologically interesting molecules. The combined information is made available via a new resource called the Biologically Interesting molecules Reference Dictionary, which is complementary to the CCD and is now routinely used for annotation of peptide-like antibiotics and inhibitors. PMID:25425036

Bio-inspired materials for electrochemical devices

NASA Astrophysics Data System (ADS)

Pawlicka, A.; Firmino, A.; Sentanin, F.; Sabadini, R. C.; Jimenez, D. E. Q.; Jayme, C. C.; Mindroiu, M.; Zgarian, R. G.; Tihan, G. T.; Rau, I.; Silva, M. M.; Nogueira, A. F.; Kanicki, J.; Kajzar, F.

2015-10-01

Natural macromolecules are very promising row materials to be used in modern technology including security and defense. They are abundant in nature, easy to extract and possess biocompatibility and biodegradability properties. These materials can be modified throughout chemical or physical processes, and can be doped with lithium and rare earth salts, ionic liquids, organic and inorganic acids. In this communication samples of DNA and modified DNA were doped with Prussian Blue (PB), poly(ethylene dioxythiophene) (PEDOT), europium and erbium triflate and organic dyes such as Nile Blue (NB), Disperse Red 1 (DR1) and Disperse Orange 3 (DO3). The colored or colorless membranes were characterized by electrochemical and spectroscopic measurements, and they were applied in electrochromic devices (ECDs) and dye sensitized solar cells (DSSC). ECDs change the color under applied potential, so they can modulate the intensity of transmitted light of 15 to 35%. As the electrochromic materials, WO3 or Prussian blue (PB), are usually blue colored, the color change is from transparent to blue. DNA, and the complexes: DNA-CTMA, DNA-DODA and DNAPEDOT: PSS were also investigated as either hole carrier material (HTM) or polymer electrolyte in dye-sensitized solar cells (DSSC). The DNA-based samples as HTM in small DSSCs revealed a solar energy conversion efficiency of 0.56%. Polymer electrolytes of DNA-CTMA and DNA-DODA, both with 10 wt% of LiI/I2, applied in small DSSC, exhibited the efficiencies of 0.18 and 0.66%, respectively. The obtained results show that natural macromolecules-based membranes are not only environmentally friendly but are also promising materials to be investigated for several electrochemical devices. However, to obtain better performances more research is still needed.

Small molecule annotation for the Protein Data Bank.

PubMed

Sen, Sanchayita; Young, Jasmine; Berrisford, John M; Chen, Minyu; Conroy, Matthew J; Dutta, Shuchismita; Di Costanzo, Luigi; Gao, Guanghua; Ghosh, Sutapa; Hudson, Brian P; Igarashi, Reiko; Kengaku, Yumiko; Liang, Yuhe; Peisach, Ezra; Persikova, Irina; Mukhopadhyay, Abhik; Narayanan, Buvaneswari Coimbatore; Sahni, Gaurav; Sato, Junko; Sekharan, Monica; Shao, Chenghua; Tan, Lihua; Zhuravleva, Marina A

2014-01-01

The Protein Data Bank (PDB) is the single global repository for three-dimensional structures of biological macromolecules and their complexes, and its more than 100,000 structures contain more than 20,000 distinct ligands or small molecules bound to proteins and nucleic acids. Information about these small molecules and their interactions with proteins and nucleic acids is crucial for our understanding of biochemical processes and vital for structure-based drug design. Small molecules present in a deposited structure may be attached to a polymer or may occur as a separate, non-covalently linked ligand. During curation of a newly deposited structure by wwPDB annotation staff, each molecule is cross-referenced to the PDB Chemical Component Dictionary (CCD). If the molecule is new to the PDB, a dictionary description is created for it. The information about all small molecule components found in the PDB is distributed via the ftp archive as an external reference file. Small molecule annotation in the PDB also includes information about ligand-binding sites and about covalent and other linkages between ligands and macromolecules. During the remediation of the peptide-like antibiotics and inhibitors present in the PDB archive in 2011, it became clear that additional annotation was required for consistent representation of these molecules, which are quite often composed of several sequential subcomponents including modified amino acids and other chemical groups. The connectivity information of the modified amino acids is necessary for correct representation of these biologically interesting molecules. The combined information is made available via a new resource called the Biologically Interesting molecules Reference Dictionary, which is complementary to the CCD and is now routinely used for annotation of peptide-like antibiotics and inhibitors. © The Author(s) 2014. Published by Oxford University Press.

The effects of bound state motion on macromolecular diffusion

NASA Astrophysics Data System (ADS)

Hough, Loren; Stefferson, Michael; Norris, Samantha; Maguire, Laura; Vernerey, Franck; Betterton, Meredith

The diffusion of macromolecules is modified in crowded environments by both inert obstacles and interaction sites. Molecules are generally slowed in their movement inducing transient anomalous subdiffusion. Obstacles also modify the kinetics and equilibrium behavior of interaction between mobile proteins. In some biophysical contexts, bound molecules can still experience mobility, for example transcription factors sliding along DNA, membrane proteins with some entry and diffusion within lipid domains, or proteins that can enter into non-membrane bound compartments such as the nucleolus. We used lattice and continuum models to study the diffusive behavior of tracer particles which bind to obstacles and can diffuse within them. We show that binding significantly alters the motion of tracers. The type and degree of motion while bound is a key determinant of the tracer mobility. Our work has implications for protein-protein movement and interactions within living cells, including those involving intrinsically disordered proteins.

Sulfation effect on levan polysaccharide chains structure with molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Coskunkan, Binnaz; Turgut, Deniz; Rende, Deniz; Malta, Seyda; Baysal, Nihat; Ozisik, Rahmi; Toksoy-Oner, Ebru

Diversity in conformations and structural heterogeneity make polysaccharides the most challenging biopolymer type for experimental and theoretical characterization studies. Levan is a biopolymer chain that consists of fructose rings with β(2-6) linkages. It is a glycan that has great potential as a functional biopolymer in foods, feeds, cosmetics, pharmaceutical and chemical industries. Sulfated polysaccharides are group of macromolecules with sulfated groups in their hydroxyl parts with a range of important biological properties. Sulfate groups and their positions have a major effect on anticoagulant activity. It is reported that sulfate modified levan has anticoagulant activity such as heparin. In the current study, the effect of sulfation on the structure and dynamics of unmodified and sulfate modified levan are investigated via fully atomistic Molecular Dynamics simulations in aqueous media and varying salt concentrations at 310 K. This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1538730.

PlaMoM: a comprehensive database compiles plant mobile macromolecules

PubMed Central

Guan, Daogang; Yan, Bin; Thieme, Christoph; Hua, Jingmin; Zhu, Hailong; Boheler, Kenneth R.; Zhao, Zhongying; Kragler, Friedrich; Xia, Yiji; Zhang, Shoudong

2017-01-01

In plants, various phloem-mobile macromolecules including noncoding RNAs, mRNAs and proteins are suggested to act as important long-distance signals in regulating crucial physiological and morphological transition processes such as flowering, plant growth and stress responses. Given recent advances in high-throughput sequencing technologies, numerous mobile macromolecules have been identified in diverse plant species from different plant families. However, most of the identified mobile macromolecules are not annotated in current versions of species-specific databases and are only available as non-searchable datasheets. To facilitate study of the mobile signaling macromolecules, we compiled the PlaMoM (Plant Mobile Macromolecules) database, a resource that provides convenient and interactive search tools allowing users to retrieve, to analyze and also to predict mobile RNAs/proteins. Each entry in the PlaMoM contains detailed information such as nucleotide/amino acid sequences, ortholog partners, related experiments, gene functions and literature. For the model plant Arabidopsis thaliana, protein–protein interactions of mobile transcripts are presented as interactive molecular networks. Furthermore, PlaMoM provides a built-in tool to identify potential RNA mobility signals such as tRNA-like structures. The current version of PlaMoM compiles a total of 17 991 mobile macromolecules from 14 plant species/ecotypes from published data and literature. PlaMoM is available at http://www.systembioinfo.org/plamom/. PMID:27924044

Polyacid macromolecule primers

DOEpatents

Sugama, Toshifumi

1989-01-01

Hydrophylic polyacids, such as macromolecules of polyitaconic acid and polyacrylic acid, where such macromolecules have molecular weights >50,000 as primers between a polymeric top coating, such as polyurethane, and an oxidized aluminum or aluminum alloy. A near monolayer of primer is used in polymeric adhesive/oxidized aluminum adhered joint systems in 0.05% primer concentration to give superior results in standard peel tests.

Macromolecule mapping of the brain using ultrashort-TE acquisition and reference-based metabolite removal.

PubMed

Lam, Fan; Li, Yudu; Clifford, Bryan; Liang, Zhi-Pei

2018-05-01

To develop a practical method for mapping macromolecule distribution in the brain using ultrashort-TE MRSI data. An FID-based chemical shift imaging acquisition without metabolite-nulling pulses was used to acquire ultrashort-TE MRSI data that capture the macromolecule signals with high signal-to-noise-ratio (SNR) efficiency. To remove the metabolite signals from the ultrashort-TE data, single voxel spectroscopy data were obtained to determine a set of high-quality metabolite reference spectra. These spectra were then incorporated into a generalized series (GS) model to represent general metabolite spatiospectral distributions. A time-segmented algorithm was developed to back-extrapolate the GS model-based metabolite distribution from truncated FIDs and remove it from the MRSI data. Numerical simulations and in vivo experiments have been performed to evaluate the proposed method. Simulation results demonstrate accurate metabolite signal extrapolation by the proposed method given a high-quality reference. For in vivo experiments, the proposed method is able to produce spatiospectral distributions of macromolecules in the brain with high SNR from data acquired in about 10 minutes. We further demonstrate that the high-dimensional macromolecule spatiospectral distribution resides in a low-dimensional subspace. This finding provides a new opportunity to use subspace models for quantification and accelerated macromolecule mapping. Robustness of the proposed method is also demonstrated using multiple data sets from the same and different subjects. The proposed method is able to obtain macromolecule distributions in the brain from ultrashort-TE acquisitions. It can also be used for acquiring training data to determine a low-dimensional subspace to represent the macromolecule signals for subspace-based MRSI. Magn Reson Med 79:2460-2469, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Preferential Surface Adsorption in Miscible Blends of Polystyrene and Poly(vinyl methyl ether).

DTIC Science & Technology

1988-02-02

D. J. Phys. Chem. 1973, 74, 356. , c’’ 26~’::~ ~ ~ q,.,rf~.. w KRINMNIMVWU94M ~ ~ W-.TO"Kśtv X"- uV 23 25. Ober, R.; Paz, L.: Taupin , C.; Pincus, P...Boileau, S. Macromolecules 1983, 16 50. 26. DiMeglio, J.M.; Ober, R.; Paz, L.; Taupin , C.; Pincus, P.; Boileau, S. J. Physique 1983,4!, 1035. 27

Formation of polymeric toroidal-spiral particles.

PubMed

Sharma, Vishal; Szymusiak, Magdalena; Shen, Hao; Nitsche, Ludwig C; Liu, Ying

2012-01-10

Compared to spherical matrices, particles with well-defined internal structure provide large surface to volume ratio and predictable release kinetics for the encapsulated payloads. We describe self-assembly of polymeric particles, whereby competitive kinetics of viscous sedimentation, diffusion, and cross-linking yield a controllable toroidal-spiral (T-S) structure. Precursor polymeric droplets are splashed through the surface of a less dense, miscible solution, after which viscous forces entrain the surrounding bulk solution into the sedimenting polymer drop to form T-S channels. The intricate structure forms because low interfacial tension between the two miscible solutions is dominated by viscous forces. The biocompatible polymer, poly(ethylene glycol) diacrylate (PEG-DA), is used to demonstrate the solidification of the T-S shapes at various configurational stages by UV-triggered cross-linking. The dimensions of the channels are controlled by Weber number during impact on the surface, and Reynolds number and viscosity ratio during subsequent sedimentation. We anticipate applications of the T-S particle in drug delivery, wherein diffusion through these T-S channels and the polymer matrix would offer parallel release pathways for molecules of different sizes. Polyphosphate, as a model macromolecule, is entrained in T-S particles during their formation. The in vitro release kinetics of polyphosphate from the T-S particles with various channel length and width is reported. In addition, self-assembly of T-S particles occurs in a single step under benign conditions for delicate macromolecules, and appears conducive to scaleup.

The Biological Macromolecule Crystallization Database and NASA Protein Crystal Growth Archive

PubMed Central

Gilliland, Gary L.; Tung, Michael; Ladner, Jane

1996-01-01

The NIST/NASA/CARB Biological Macromolecule Crystallization Database (BMCD), NIST Standard Reference Database 21, contains crystal data and crystallization conditions for biological macromolecules. The database entries include data abstracted from published crystallographic reports. Each entry consists of information describing the biological macromolecule crystallized and crystal data and the crystallization conditions for each crystal form. The BMCD serves as the NASA Protein Crystal Growth Archive in that it contains protocols and results of crystallization experiments undertaken in microgravity (space). These database entries report the results, whether successful or not, from NASA-sponsored protein crystal growth experiments in microgravity and from microgravity crystallization studies sponsored by other international organizations. The BMCD was designed as a tool to assist x-ray crystallographers in the development of protocols to crystallize biological macromolecules, those that have previously been crystallized, and those that have not been crystallized. PMID:11542472

High throughput screening of ligand binding to macromolecules using high resolution powder diffraction

DOEpatents

Von Dreele, Robert B.; D'Amico, Kevin

2006-10-31

A process is provided for the high throughput screening of binding of ligands to macromolecules using high resolution powder diffraction data including producing a first sample slurry of a selected polycrystalline macromolecule material and a solvent, producing a second sample slurry of a selected polycrystalline macromolecule material, one or more ligands and the solvent, obtaining a high resolution powder diffraction pattern on each of said first sample slurry and the second sample slurry, and, comparing the high resolution powder diffraction pattern of the first sample slurry and the high resolution powder diffraction pattern of the second sample slurry whereby a difference in the high resolution powder diffraction patterns of the first sample slurry and the second sample slurry provides a positive indication for the formation of a complex between the selected polycrystalline macromolecule material and at least one of the one or more ligands.

Preparation of polymeric Janus particles by directional UV-induced reactions.

PubMed

Liu, Lianying; Ren, Mingwei; Yang, Wantai

2009-09-15

Polymeric Janus particles are obtained by UV-induced selective surface grafting polymerizations and coupling reactions, in virtue of the light-absorption of photoreactive materials such as the immobilized photoinitiator and spread photoinitiator solution on the surfaces exposed to UV light and the sheltering of densely arrayed immovable particles from light. Varying the monomers or macromolecules applied in photografting polymerization or coupling reaction, and choosing diverse polymeric particles of various size, bicolor and amphiphilic Janus particles could be successfully achieved. Observations by fluorescence microscope, scanning electron microscope ,and transmission electron microscope confirmed the asymmetrical morphology of the resultant Janus particles.

Anti-Arrhenius cleavage of covalent bonds in bottlebrush macromolecules on substrate

PubMed Central

Lebedeva, Natalia V.; Nese, Alper; Sun, Frank C.; Matyjaszewski, Krzysztof; Sheiko, Sergei S.

2012-01-01

Spontaneous degradation of bottlebrush macromolecules on aqueous substrates was monitored by atomic force microscopy. Scission of C─C covalent bonds in the brush backbone occurred due to steric repulsion between the adsorbed side chains, which generated bond tension on the order of several nano-Newtons. Unlike conventional chemical reactions, the rate of bond scission was shown to decrease with temperature. This apparent anti-Arrhenius behavior was caused by a decrease in the surface energy of the underlying substrate upon heating, which results in a corresponding decrease of bond tension in the adsorbed macromolecules. Even though the tension dropped minimally from 2.16 to 1.89 nN, this was sufficient to overpower the increase in the thermal energy (kBT) in the Arrhenius equation. The rate constant of the bond-scission reaction was measured as a function of temperature and surface energy. Fitting the experimental data by a perturbed Morse potential V = V0(1 - e-βx)2 - fx, we determined the depth and width of the potential to be V0 = 141 ± 19 kJ/mol and β-1 = 0.18 ± 0.03 Å, respectively. Whereas the V0 value is in reasonable agreement with the activation energy Ea = 80–220 kJ/mol of mechanical and thermal degradation of organic polymers, it is significantly lower than the dissociation energy of a C─C bond De = 350 kJ/mol. Moreover, the force constant Kx = 2β2V0 = 1.45 ± 0.36 kN/m of a strained bottlebrush along its backbone is markedly larger than the force constant of a C─C bond Kl = 0.44 kN/m, which is attributed to additional stiffness due to deformation of the side chains. PMID:22645366

The Electric Potential of a Macromolecule in a Solvent: A Fundamental Approach

NASA Astrophysics Data System (ADS)

Juffer, André H.; Botta, Eugen F. F.; van Keulen, Bert A. M.; van der Ploeg, Auke; Berendsen, Herman J. C.

1991-11-01

A general numerical method is presented to compute the electric potential for a macromolecule of arbitrary shape in a solvent with nonzero ionic strength. The model is based on a continuum description of the dielectric and screening properties of the system, which consists of a bounded internal region with discrete charges and an infinite external region. The potential obeys the Poisson equation in the internal region and the linearized Poisson-Boltzmann equation in the external region, coupled through appropriate boundary conditions. It is shown how this three-dimensional problem can be presented as a pair of coupled integral equations for the potential and the normal component of the electric field at the dielectric interface. These equations can be solved by a straightforward application of boundary element techniques. The solution involves the decomposition of a matrix that depends only on the geometry of the surface and not on the positions of the charges. With this approach the number of unknowns is reduced by an order of magnitude with respect to the usual finite difference methods. Special attention is given to the numerical inaccuracies resulting from charges which are located close to the interface; an adapted formulation is given for that case. The method is tested both for a spherical geometry, for which an exact solution is available, and for a realistic problem, for which a finite difference solution and experimental verification is available. The latter concerns the shift in acid strength (pK-values) of histidines in the copper-containing protein azurin on oxidation of the copper, for various values of the ionic strength. A general method is given to triangulate a macromolecular surface. The possibility is discussed to use the method presented here for a correct treatment of long-range electrostatic interactions in simulations of solvated macromolecules, which form an essential part of correct potentials of mean force.

Imaging of biological macromolecules on mica in humid air by scanning electrochemical microscopy

PubMed Central

Fan, Fu-Ren F.; Bard, Allen J.

1999-01-01

Imaging of DNA, keyhole limpet hemocyanin, mouse monoclonal IgG, and glucose oxidase on a mica substrate has been accomplished by scanning electrochemical microscopy with a tungsten tip. The technique requires the use of a high relative humidity to form a thin film of water on the mica surface that allows electrochemical reactions to take place at the tip and produce a faradaic current (≈1 pA) that can be used to control tip position. The effect of relative humidity and surface pretreatment with buffer solutions on the ionic conductivity of a mica surface was investigated to find appropriate conditions for imaging. Resolution of the order of 1 nm was obtained. PMID:10588687

An implicit boundary integral method for computing electric potential of macromolecules in solvent

NASA Astrophysics Data System (ADS)

Zhong, Yimin; Ren, Kui; Tsai, Richard

2018-04-01

A numerical method using implicit surface representations is proposed to solve the linearized Poisson-Boltzmann equation that arises in mathematical models for the electrostatics of molecules in solvent. The proposed method uses an implicit boundary integral formulation to derive a linear system defined on Cartesian nodes in a narrowband surrounding the closed surface that separates the molecule and the solvent. The needed implicit surface is constructed from the given atomic description of the molecules, by a sequence of standard level set algorithms. A fast multipole method is applied to accelerate the solution of the linear system. A few numerical studies involving some standard test cases are presented and compared to other existing results.

Directed aggregation of carbon nanotube on curved surfaces by polymer induced depletion attraction

NASA Astrophysics Data System (ADS)

Lee, Hsin-Chieh; Jiang, Hong-Ren

2017-12-01

In this study, we show that by chemically grafting macromolecule, polyethylene glycol (PEG), onto CNTs, PEG-CNTs become dispersible in an aqueous solution with tunable depletion interactions with each other. The aggregation of the PEG-CNTs can be controlled by adding PEG polymers into the solution. PEG-CNTs not only aggregate with each other but also tend to aggregate on curved surfaces. Due to this property, we show that PEG-CNTs can be directed to aggregate on particles and patterned surfaces. Depletion interaction induced aggregation of PEG-CNTs may provide a method to place PEG-CNTs on a specific position for different applications ranging from biomedical to industrial usages.

Polyacid macromolecule primers

DOEpatents

Sugama, Toshifumi.

1989-12-26

Hydrophilic polyacids are described, such as macromolecules of polyitaconic acid and polyacrylic acid, where such macromolecules have molecular weights >50,000 as primers between a polymeric top coating, such as polyurethane, and an oxidized aluminum or aluminum alloy. A near monolayer of primer is used in polymeric adhesive/oxidized aluminum adhered joint systems in 0.05% primer concentration to give superior results in standard peel tests. 2 figs.

Radiolysis of lignin: Prospective mechanism of high-temperature decomposition

NASA Astrophysics Data System (ADS)

Ponomarev, A. V.

2017-12-01

The range of the radiation-thermal processes resulting in conversion of lignin into monomeric phenols is considered. Statistically the most probable places of macromolecule ionization are aromatic units. Release of phenolic products from a lignin macromolecule is the multistage process beginning via fragmentation of primary cation-radicals. Reactions of electrons and small radicals with macromolecules, also as degradation of cation-radicals, result in formation of phenoxyl radicals. Macroradicals possess lower heat stability in comparison with macromolecules. Thermal decomposition of macroradicals leads to release of monohydric and dihydric phenols. The probability of benzenediols formation increases in the presence of alkanes. As noted, partial transformation of lignin into charcoal is inevitable.

Novel fluorescent core-shell nanocontainers for cell membrane transport.

PubMed

Yin, Meizhen; Kuhlmann, Christoph R W; Sorokina, Ksenia; Li, Chen; Mihov, George; Pietrowski, Eweline; Koynov, Kaloian; Klapper, Markus; Luhmann, Heiko J; Müllen, Klaus; Weil, Tanja

2008-05-01

The synthesis and characterization of novel core-shell macromolecules consisting of a fluorescent perylene-3,4,9,10-tetracarboxdiimide chromophore in the center surrounded by a hydrophobic polyphenylene shell as a first and a flexible hydrophilic polymer shell as a second layer was presented. Following this strategy, several macromolecules bearing varying polymer chain lengths, different polymer shell densities, and increasing numbers of positive and negative charges were achieved. Because all of these macromolecules reveal a good water solubility, their ability to cross cellular membranes was investigated. In this way, a qualitative relationship between the molecular architecture of these macromolecules and the biological response was established.

Structure-property relationships of a biological mesocrystal in the adult sea urchin spine

PubMed Central

Seto, Jong; Ma, Yurong; Davis, Sean A.; Meldrum, Fiona; Gourrier, Aurelien; Kim, Yi-Yeoun; Schilde, Uwe; Sztucki, Michael; Burghammer, Manfred; Maltsev, Sergey; Jäger, Christian; Cölfen, Helmut

2012-01-01

Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials. PMID:22343283

Immunoassays for pesticide monitoring

NASA Astrophysics Data System (ADS)

Wengatz, Ingrid; Szurdoki, Ferenc; Swamy, Anand R.; Evans, Lawrence, III; Patonay, Gabor; Stimmann, Eric; Delwiche, Michael; Stoutamire, Donald; Gee, Shirley J.; Hammock, Bruce D.

1995-05-01

This study compares two formats of rapid assays for the detection of pesticides (bromacil and pyrethroid based metabolites): enzyme linked immunosorbent assay (ELISA) and immunoassay with near-infrared (NIR) fluorescence detection. NIR dye immunoassay (NIRDIA) measurements were carried out by using two different instruments, both having a silicon photodiode as the detector and a laser diode for excitation. ELISA and NIRDIA were performed in a tracer format, where the specific antibody is bound to the surface of a microtiter plate well and the tracer with enzyme or fluorescent dye label competes with the analyte for the antibody binding site. It was demonstrated that the NIRDIA is at least as sensitive as the ELISA. Both assays detect pesticides in the (mu) g/L (ppb) range. Hapten- macromolecule-NIR dye-conjugates have been synthesized with various biopolymers (e.g., proteins) as carriers. The use of carrier macromolecules enables convenient purification of the cyanine dye derivatives. The mild conjugation method of the dye is based on isothiocyanate chemistry.

Electronic structure, dielectric response, and surface charge distribution of RGD (1FUV) peptide.

PubMed

Adhikari, Puja; Wen, Amy M; French, Roger H; Parsegian, V Adrian; Steinmetz, Nicole F; Podgornik, Rudolf; Ching, Wai-Yim

2014-07-08

Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.

Controlled method of reducing electrophoretic mobility of macromolecules, particles, or cells

NASA Technical Reports Server (NTRS)

Vanalstine, James M. (Inventor)

1992-01-01

A method of reducing electrophoretic mobility of macromolecules, particles, cells, and other substances is provided which comprises interacting in a conventional electrophoretic separating procedure, the substances with a polymer-linked affinity compound comprised of a hydrophilic neutral polymer such as polyethylene glycol bound to a second component such as a hydrophobic compound, an immunocompound such as an antibody or antibody active fragment, or a ligand such as a hormone, drug, antigen, or a hapten. The reduction of electrophoretic mobility achieved is directly proportional to the concentration of the polymer-linked affinity compound employed, and such reduction can comprise up to 100 percent for particular particles and cells. The present invention is advantageous in that electrophoretic separation can now be achieved for substances whose native surface charge structure had prevented them from being separated by normal electrophoretic means. Depending on the affinity component utilized, separation can be achieved on the basis of the specific/irreversible, specific/reversible, semi-specific/reversible, relatively nonspecific/reversible, or relatively nonspecific/irreversible ligand-substance interactions.

Structure-property relationships of a biological mesocrystal in the adult sea urchin spine.

PubMed

Seto, Jong; Ma, Yurong; Davis, Sean A; Meldrum, Fiona; Gourrier, Aurelien; Kim, Yi-Yeoun; Schilde, Uwe; Sztucki, Michael; Burghammer, Manfred; Maltsev, Sergey; Jäger, Christian; Cölfen, Helmut

2012-03-06

Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature's demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.

PlaMoM: a comprehensive database compiles plant mobile macromolecules.

PubMed

Guan, Daogang; Yan, Bin; Thieme, Christoph; Hua, Jingmin; Zhu, Hailong; Boheler, Kenneth R; Zhao, Zhongying; Kragler, Friedrich; Xia, Yiji; Zhang, Shoudong

2017-01-04

In plants, various phloem-mobile macromolecules including noncoding RNAs, mRNAs and proteins are suggested to act as important long-distance signals in regulating crucial physiological and morphological transition processes such as flowering, plant growth and stress responses. Given recent advances in high-throughput sequencing technologies, numerous mobile macromolecules have been identified in diverse plant species from different plant families. However, most of the identified mobile macromolecules are not annotated in current versions of species-specific databases and are only available as non-searchable datasheets. To facilitate study of the mobile signaling macromolecules, we compiled the PlaMoM (Plant Mobile Macromolecules) database, a resource that provides convenient and interactive search tools allowing users to retrieve, to analyze and also to predict mobile RNAs/proteins. Each entry in the PlaMoM contains detailed information such as nucleotide/amino acid sequences, ortholog partners, related experiments, gene functions and literature. For the model plant Arabidopsis thaliana, protein-protein interactions of mobile transcripts are presented as interactive molecular networks. Furthermore, PlaMoM provides a built-in tool to identify potential RNA mobility signals such as tRNA-like structures. The current version of PlaMoM compiles a total of 17 991 mobile macromolecules from 14 plant species/ecotypes from published data and literature. PlaMoM is available at http://www.systembioinfo.org/plamom/. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Rapid Brownian Motion Primes Ultrafast Reconstruction of Intrinsically Disordered Phe-Gly Repeats Inside the Nuclear Pore Complex

PubMed Central

Moussavi-Baygi, R.; Mofrad, M. R. K.

2016-01-01

Conformational behavior of intrinsically disordered proteins, such as Phe-Gly repeat domains, alters drastically when they are confined in, and tethered to, nan channels. This has challenged our understanding of how they serve to selectively facilitate translocation of nuclear transport receptor (NTR)-bearing macromolecules. Heterogeneous FG-repeats, tethered to the NPC interior, nonuniformly fill the channel in a diameter-dependent manner and adopt a rapid Brownian motion, thereby forming a porous and highly dynamic polymeric meshwork that percolates in radial and axial directions and features two distinguishable zones: a dense hydrophobic rod-like zone located in the center, and a peripheral low-density shell-like zone. The FG-meshwork is locally disrupted upon interacting with NTR-bearing macromolecules, but immediately reconstructs itself between 0.44 μs and 7.0 μs, depending on cargo size and shape. This confers a perpetually-sealed state to the NPC, and is solely due to rapid Brownian motion of FG-repeats, not FG-repeat hydrophobic bonds. Elongated-shaped macromolecules, both in the presence and absence of NTRs, penetrate more readily into the FG-meshwork compared to their globular counterparts of identical volume and surface chemistry, highlighting the importance of the shape effects in nucleocytoplasmic transport. These results can help our understanding of geometrical effects in, and the design of, intelligent and responsive biopolymer-based materials in nanofiltration and artificial nanopores. PMID:27470900

Synthesis, inhibition effects and quantum chemical studies of a novel coumarin derivative on the corrosion of mild steel in a hydrochloric acid solution.

PubMed

Al-Azawi, Khalida F; Al-Baghdadi, Shaimaa B; Mohamed, Ayad Z; Al-Amiery, Ahmed A; Abed, Talib K; Mohammed, Salam A; Kadhum, Abdul Amir H; Mohamad, Abu Bakar

2016-01-01

The acid corrosion inhibition process of mild steel in 1 M HCl by 4-[(2-amino-1, 3, 4-thiadiazol-5-yl)methoxy]coumarin (ATC), has been investigated using weight loss technique and scanning electron microscopy (SEM). ATC was synthesized, and its chemical structure was elucidated and confirmed using spectroscopic techniques (infrared and nuclear magnetic resonance spectroscopy). The results indicated that inhibition efficiencies were enhanced with an increase in concentration of inhibitor and decreased with a rise in temperature. The adsorption equilibrium constant (K) and standard free energy of adsorption (ΔGads) were calculated. Quantum chemical parameters such as highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy (EHOMO and ELUMO, respectively) and dipole moment (μ) were calculated and discussed. The results showed that the corrosion inhibition efficiency increased with an increase in both the EHOMO and μ values but with a decrease in the ELUMO value. Our research show that the synthesized macromolecule represents an excellent inhibitor for materials in acidic solutions. The efficiency of this macromolecule had maximum inhibition efficiency up to 96 % at 0.5 mM and diminishes with a higher temperature degree, which is revealing of chemical adsorption. An inhibitor molecule were absorbed by metal surface and follow Langmuir isotherms low and establishes an efficient macromolecule inhibitor having excellent inhibitive properties due to entity of S (sulfur) atom, N (nitrogen) atom and O (oxygen) atom.

Selective binding, uptake, and retrograde transport of tetanus toxin by nerve terminals in the rat iris. An electron microscope study using colloidal gold as a tracer

PubMed Central

1978-01-01

A series of specific macromolecules (tetanus toxin, cholera toxin, nerve growth factor [NGF], and several lectins) have been shown to be transported retrogradely with high selectivity from terminals to cell bodies in various types of neurons. Under identical experimental conditions (low protein concentrations injected), most other macromolecules, e.g. horseradish peroxidase (HRP), albumin, ferritin, are not transported in detectable amounts. In the present EM study, we demonstrate selective binding of tetanus toxin to the surface membrane of nerve terminals, followed by uptake and subsequent retorgrade axonal transport. Tetanus toxin or albumin was adsorbed to colloidal gold particles (diam 200 A). The complex was shown to be stable and well suited as an EM tracer. 1-4 h after injection into the anterior eye chamber of adult rats, tetanus toxin-gold particles were found to be selectively associated with membranes of nerve terminals and preterminal axons. Inside terminals and axons, the tracer was localized mainly in smooth endoplasmic reticulum (SER)-like membrane compartments. In contrast, association of albumin-gold complexes with nervous structures was never observed, in spite of extensive uptake into fibroblasts. Electron microscope and biochemical experiments showed selective retrograde transport of tetanus toxin-gold complexes to the superior cervical ganglion. Specific binding to membrane components at nerve terminals and subsequent internalization and retrograde transport may represent an important pathway for macromolecules carrying information from target organs to the perikarya of their innervating neurons. PMID:659508

Skin aging by glycation: lessons from the reconstructed skin model.

PubMed

Pageon, Hervé; Zucchi, Hélène; Rousset, Françoise; Monnier, Vincent M; Asselineau, Daniel

2014-01-01

Aging is the result of several mechanisms which operate simultaneously. Among them, glycation is of particular interest because it is a reaction which affects slowly renewing tissues and macromolecules with elevated half-life, like the dermis, a skin compartment highly affected by aging. Glycation produces crosslinks between macromolecules thereby providing an explanation for the increased age-related stiffness of the skin. Glycation products, also called AGEs (advanced glycation end products), accumulate primarily in extracellular matrix molecules like collagen or elastin. In order to reproduce this phenomenon in vitro we have created a model of reconstructed skin modified by glycation of the collagen used to fabricate the dermal compartment. This system allowed us to uncover biological modifications of dermal markers, and more surprisingly epidermal markers, as well as an increase of metalloproteinases responsible for degradation of the dermal matrix. Consequently, the imbalance between synthesis and degradation that results from glycation, may contribute to skin aging, as shown in this model. Moreover these modifications were shown to be prevented by the addition of aminoguanidine, a well-known inhibitor of glycation. Using this experimental approach our results taken together stress the importance and possibly central role of glycation in skin aging and the usefulness of the reconstructed skin as a model of physiological aging.

Arginine-rich proteins in spherical inclusions of human locus coeruleus neurons demonstrated by benzil modification.

PubMed

Panayotacopoulou, M T; Issidorides, M R

1984-11-01

Previous studies have shown that aminergic neurons in the normal human brain contain acidophilic cytoplasmic inclusions--called protein bodies (PBs)--that are reduced or absent in parkinsonism and disrupted in depression. The purpose of the present study was to elucidate the constitution of PBs in five formalin-fixed normal human brains using histochemical methods specific for histones, protamines, and the amino acid arginine. PBs were revealed with alkaline fast green and bromphenol blue, exhibiting a high content in histones and in protamines. They developed blue metachromasia with phosphotungstic acid-hematoxylin and green fluorescence with phenanthrenequinone, which established the presence of arginyl residues. Using benzil, which selectively modifies the guanido group of arginine, staining was blocked for each of the above two methods. The application of Mallory's trichrome procedure after benzil differentiated the PBs into an unstained core and a still fuchsinophilic rim. Since the fuchsinophilia of the rim was shown to persist after acetylation as well, we suggest that this rim probably contains acidic macromolecules that attach to the basic charges of the amphoteric acid fuchsin. We conclude that the PB are complex structures consisting of a core segregating arginine-rich proteins and a rim which probably contains macromolecules of an acidic nature.

How to tackle protein structural data from solution and solid state: An integrated approach.

PubMed

Carlon, Azzurra; Ravera, Enrico; Andrałojć, Witold; Parigi, Giacomo; Murshudov, Garib N; Luchinat, Claudio

2016-02-01

Long-range NMR restraints, such as diamagnetic residual dipolar couplings and paramagnetic data, can be used to determine 3D structures of macromolecules. They are also used to monitor, and potentially to improve, the accuracy of a macromolecular structure in solution by validating or "correcting" a crystal model. Since crystal structures suffer from crystal packing forces they may not be accurate models for the macromolecular structures in solution. However, the presence of real differences should be tested for by simultaneous refinement of the structure using both crystal and solution NMR data. To achieve this, the program REFMAC5 from CCP4 was modified to allow the simultaneous use of X-ray crystallographic and paramagnetic NMR data and/or diamagnetic residual dipolar couplings. Inconsistencies between crystal structures and solution NMR data, if any, may be due either to structural rearrangements occurring on passing from the solution to solid state, or to a greater degree of conformational heterogeneity in solution with respect to the crystal. In the case of multidomain proteins, paramagnetic restraints can provide the correct mutual orientations and positions of domains in solution, as well as information on the conformational variability experienced by the macromolecule. Copyright © 2016 Elsevier B.V. All rights reserved.

Ligand conjugation to bimodal poly(ethylene glycol) brush layers on microbubbles.

PubMed

Chen, Cherry C; Borden, Mark A

2010-08-17

Using microbubbles as model systems, we examined molecular diffusion and binding to colloidal surfaces in bimodal poly(ethylene glycol) (PEG) brush layers. A microbubble is a gaseous colloidal particle with a diameter of less than 10 mum, of which the surface comprises amphiphilic phospholipids self-assembled to form a lipid monolayer shell. Due to the compressible gas core, microbubbles provide a sensitive acoustic response and are currently used as ultrasound contrast agents. Similar to the design of long circulating liposomes, PEG chains are typically incorporated into the shell of microbubbles to form a steric barrier against coalescence and adsorption of macromolecules to the microbubble surface. We introduced a buried-ligand architecture (BLA) design where the microbubble surface was coated with a bimodal PEG brush. After microbubbles were generated, fluorescent ligands with different molecular weights were conjugated to the tethered functional groups on the shorter PEG chains, while the longer PEG chains served as a shield to protect these ligands from exposure to the surrounding environment. BLA microbubbles reduced the binding of macromolecules (>10 kDa) to the tethers due to the steric hindrance of the PEG overbrush while allowing the uninhibited attachment of small molecules (<1 kDa). Roughly 40% less fluorescein-conjugated streptavidin (SA-FITC) bound to BLA microbubbles compared to exposed-ligand architecture (ELA) microbubbles. The binding of SA-FITC to BLA microbubbles suggested a possible phase separation between the lipid species on the surface leading to populations of revealed and concealed ligands. Ligand conjugation kinetics was independent of microbubble size, regardless of ligand size or microbubble architecture. We observed, for the first time, streptavidin-induced surface structure formation for ELA microbubbles and proposed that this phenomenon may be correlated to flow cytometry scattering measurements. We therefore demonstrated the feasibility of postlabeling for small-molecule ligands to BLA microbubbles to generate stealth targeted ultrasound contrast agents.

Preparation and recognition performance of creatinine-imprinted material prepared with novel surface-imprinting technique.

PubMed

Gao, Baojiao; Li, Yanbin; Zhang, Zhenguo

2010-08-01

By adopting the novel surface molecular imprinting technique put forward by us not long ago, a creatinine molecule-imprinted material with high performance was prepared. The functional macromolecule polymethacrylic acid (PMAA) was first grafted on the surfaces of micron-sized silica gel particles in the manner of "grafting from" using 3-methacryloxypropyltrimethoxysilane (MPS) as intermedia, resulting in the grafted particles PMAA/SiO(2). Subsequently, the molecular imprinting was carried out towards the grafted macromolecule PMAA using creatinine as template and with ethylene glycol diglycidyl ether (EGGE) as crosslinker by right of the intermolecular hydrogen bonding and electrostatic interaction between the grafted PMAA and creatinine molecules. Finally, the creatinine-imprinted material MIP-PMAA/SiO(2) was obtained. The binding character of MIP-PMAA/SiO(2) for creatinine was investigated in depth with both batch and column methods and using N-hydroxysuccinimide and creatine as two contrast substances, whose chemical structures are similar to creatinine to a certain degree. The experimental results show that the surface-imprinted material MIP-PMAA/SiO(2) has excellent binding affinity and high recognition selectivity for creatinine. Before imprinting, PMAA/SiO(2) particles nearly has not recognition selectivity for creatinine, and the selectivity coefficients of PMAA/SiO(2) for creatinine relative to N-hydroxysuccinimide and creatine are only 1.23 and 1.30, respectively. However, after imprinting, the selectivity coefficients of MIP-PMAA/SiO(2) for creatinine in respect to N-hydroxysuccinimide and creatine are remarkably enhanced to 11.64 and 12.87, respectively, displaying the excellent recognition selectivity and binding affinity towards creatinine molecules. Copyright 2010 Elsevier B.V. All rights reserved.

An investigation into the role of macromolecules of different polarity as passivating agent on the physical, chemical and structural properties of fluorescent carbon nanodots

NASA Astrophysics Data System (ADS)

Alas, Melis Ozge; Genc, Rukan

2017-05-01

In this study, comparative evaluation of fluorescent carbon nanodots (C-Dots) prepared using carob molasses was reported by screening various biocompatible macromolecules as passivating agent (PA). Incorporation of PAs with different molecular weight, polarity, and chemical structure was examined, and compared with the polyethylene glycol (PEG, Mn = 10 kN) passivated and pristine C-Dots. Not only the fluorescence properties but also many other features including size, crystal structure, colloidal conductivity, resistance to photobleaching, quantum yield, and UV-modulated surface interaction of them with the reactive oxygen species (ROS) as well as ROS production were investigated. Photoluminescence (PL) capacity of C-Dots was found to be associated with the number of surface alkyl groups and polymeric hydrogen bounding present on the C-Dot surface (increased number is associated with decreased PL) while surface conductivity of C-Dots in water was proportional to the PL intensity. More importantly, C-Dots with relatively poorer fluorescent were investigated in various organic solvents (hexane, methanol, acetone, ethanol, dimethylformamide (DMF), and DMSO). As happens with the fluorescent dyes, their PL intensities were significantly enhanced (even for pristine C-Dots) depending on the solvent characteristics. All of the C-Dots synthesized were further evaluated by means of UV-induced generation of ROS and inhibition of ROS by using H2O2 as model. In contrary to other carbonaceous nanomaterials, they did not show any ROS generation, on the contrary, they showed ROS scavenging activity that can be modulated by UV-irradiation ( λ exc = 365 nm). PEG and alginate passivated C-Dots inhibited H2O2 activity at LC50 values below 10 mg/mL.

Modeling salt-mediated electrostatics of macromolecules: the discrete surface charge optimization algorithm and its application to the nucleosome.

PubMed

Beard, D A; Schlick, T

2001-01-01

Much progress has been achieved on quantitative assessment of electrostatic interactions on the all-atom level by molecular mechanics and dynamics, as well as on the macroscopic level by models of continuum solvation. Bridging of the two representations-an area of active research-is necessary for studying integrated functions of large systems of biological importance. Following perspectives of both discrete (N-body) interaction and continuum solvation, we present a new algorithm, DiSCO (Discrete Surface Charge Optimization), for economically describing the electrostatic field predicted by Poisson-Boltzmann theory using a discrete set of Debye-Hückel charges distributed on a virtual surface enclosing the macromolecule. The procedure in DiSCO relies on the linear behavior of the Poisson-Boltzmann equation in the far zone; thus contributions from a number of molecules may be superimposed, and the electrostatic potential, or equivalently the electrostatic field, may be quickly and efficiently approximated by the summation of contributions from the set of charges. The desired accuracy of this approximation is achieved by minimizing the difference between the Poisson-Boltzmann electrostatic field and that produced by the linearized Debye-Hückel approximation using our truncated Newton optimization package. DiSCO is applied here to describe the salt-dependent electrostatic environment of the nucleosome core particle in terms of several hundred surface charges. This representation forms the basis for modeling-by dynamic simulations (or Monte Carlo)-the folding of chromatin. DiSCO can be applied more generally to many macromolecular systems whose size and complexity warrant a model resolution between the all-atom and macroscopic levels. Copyright 2000 John Wiley & Sons, Inc.

Microbial Fouling and Its Effect on Power Generation.

DTIC Science & Technology

1982-09-01

Bryers, J. D. (1980) " Dynamics of Early Biof’dm Formation in a Turbulent Flow System." Ph.D. dissertation, Rice University. Trulear, M. G. (1980...studies to date have avoided addressing fundamental questions concerning fouling in fluid flow and heat transfer systems and their effect on fluid...34clean" surface exposed to turbulent flow of a tuid con- taining dispersed microorganisms, nutrient, and organic macromolecules. Adsorption of an organic

Coated substrate apparatus and method

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

Bao, Zhenan; Diao, Ying; Mannsfeld, Stefan Christian Bernhardt

A coated substrate is formed with aligned objects such as small molecules, macromolecules and nanoscale particulates, such as inorganic, organic or inorganic/organic hybrid materials. In accordance with one or more embodiments, an apparatus or method involves an applicator having at least one surface patterned with protruded or indented features, and a coated substrate including a solution-based layer of objects having features and morphology attributes arranged as a function of the protruded or indented features.

Crystallization of Macromolecules

PubMed Central

Friedmann, David; Messick, Troy; Marmorstein, Ronen

2014-01-01

X-ray crystallography has evolved into a very powerful tool to determine the three-dimensional structure of macromolecules and macromolecular complexes. The major bottleneck in structure determination by X-ray crystallography is the preparation of suitable crystalline samples. This unit outlines steps for the crystallization of a macromolecule, starting with a purified, homogeneous sample. The first protocols describe preparation of the macromolecular sample (i.e., proteins, nucleic acids, and macromolecular complexes). The preparation and assessment of crystallization trials is then described, along with a protocol for confirming whether the crystals obtained are composed of macromolecule as opposed to a crystallization reagent . Next, the optimization of crystallization conditions is presented. Finally, protocols that facilitate the growth of larger crystals through seeding are described. PMID:22045560

Microbial specificity of metallic surfaces exposed to ambient seawater

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

Zaidi, B.R.; Bard, R.F.; Tosteson, T.R.

1984-09-01

High-molecular-weight materials associated with the extracellular matrix and film found on titanium and aluminum surfaces after exposure to flowing coastal seawater were isolated. This material was purified by hydroxylapatite chromatography and subsequently employed to produce antibodies in the toad, Bufo marinus. The antibodies were immobilized on a solid support and employed to isolate adhesion-enhancing, high-molecular-weight materials from the laboratory culture media of bacterial strains recovered from the respective metallic surfaces during the course of their exposure to seawater. The adhesion-enhancing materials produced by the surface-associated bacterial strains were immunologically related to the extracellular biofouling matrix material found on the surfacesmore » from which these bacteria were isolated. The surface selectivity of these bacterial strains appeared to be based on the specificity of the interaction between adhesion-enhancing macromolecules produced by these bacteria and the surfaces in question. 30 references, 6 tables.« less

Molecular Imprinting of Macromolecules for Sensor Applications

PubMed Central

Saylan, Yeşeren; Yilmaz, Fatma; Özgür, Erdoğan; Derazshamshir, Ali; Yavuz, Handan; Denizli, Adil

2017-01-01

Molecular recognition has an important role in numerous living systems. One of the most important molecular recognition methods is molecular imprinting, which allows host compounds to recognize and detect several molecules rapidly, sensitively and selectively. Compared to natural systems, molecular imprinting methods have some important features such as low cost, robustness, high recognition ability and long term durability which allows molecularly imprinted polymers to be used in various biotechnological applications, such as chromatography, drug delivery, nanotechnology, and sensor technology. Sensors are important tools because of their ability to figure out a potentially large number of analytical difficulties in various areas with different macromolecular targets. Proteins, enzymes, nucleic acids, antibodies, viruses and cells are defined as macromolecules that have wide range of functions are very important. Thus, macromolecules detection has gained great attention in concerning the improvement in most of the studies. The applications of macromolecule imprinted sensors will have a spacious exploration according to the low cost, high specificity and stability. In this review, macromolecules for molecularly imprinted sensor applications are structured according to the definition of molecular imprinting methods, developments in macromolecular imprinting methods, macromolecular imprinted sensors, and conclusions and future perspectives. This chapter follows the latter strategies and focuses on the applications of macromolecular imprinted sensors. This allows discussion on how sensor strategy is brought to solve the macromolecules imprinting. PMID:28422082

Iontophoretic transport of charged macromolecules across human sclera.

PubMed

Chopra, Poonam; Hao, Jinsong; Li, S Kevin

2010-03-30

The mechanisms of transscleral iontophoresis have been investigated previously with small molecules in rabbit sclera. The objective of the present study was to examine transscleral iontophoretic transport of charged macromolecules across excised human sclera. Passive and 2mA iontophoretic transport experiments were conducted in side-by-side diffusion cells with human sclera. The effects of iontophoresis upon transscleral transport of model permeants bovine serum albumin (BSA) and polystyrene sulfonic acid (PSS) as well as a model drug bevacizumab (BEV) were determined. Passive and iontophoretic transport experiments of tetraethylammonium (TEA) and salicylic acid (SA) and passive transport experiments of the macromolecules served as the controls. The results of iontophoresis enhanced transport of TEA and SA across human sclera were consistent with those in a previous rabbit sclera study. For the iontophoretic transport of macromolecules BSA and BEV, higher iontophoretic fluxes were observed in anodal iontophoresis as compared to passive and cathodal iontophoresis. This suggests the importance of electroosmosis. For the polyelectrolyte PSS, higher iontophoretic flux was observed in cathodal iontophoresis compared to anodal iontophoresis. Both electroosmosis and electrophoresis affected iontophoretic fluxes of the macromolecules; the relative contributions of electroosmosis and electrophoresis were a function of molecular size and charge of the macromolecules. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Molecular Imprinting of Macromolecules for Sensor Applications.

PubMed

Saylan, Yeşeren; Yilmaz, Fatma; Özgür, Erdoğan; Derazshamshir, Ali; Yavuz, Handan; Denizli, Adil

2017-04-19

Molecular recognition has an important role in numerous living systems. One of the most important molecular recognition methods is molecular imprinting, which allows host compounds to recognize and detect several molecules rapidly, sensitively and selectively. Compared to natural systems, molecular imprinting methods have some important features such as low cost, robustness, high recognition ability and long term durability which allows molecularly imprinted polymers to be used in various biotechnological applications, such as chromatography, drug delivery, nanotechnology, and sensor technology. Sensors are important tools because of their ability to figure out a potentially large number of analytical difficulties in various areas with different macromolecular targets. Proteins, enzymes, nucleic acids, antibodies, viruses and cells are defined as macromolecules that have wide range of functions are very important. Thus, macromolecules detection has gained great attention in concerning the improvement in most of the studies. The applications of macromolecule imprinted sensors will have a spacious exploration according to the low cost, high specificity and stability. In this review, macromolecules for molecularly imprinted sensor applications are structured according to the definition of molecular imprinting methods, developments in macromolecular imprinting methods, macromolecular imprinted sensors, and conclusions and future perspectives. This chapter follows the latter strategies and focuses on the applications of macromolecular imprinted sensors. This allows discussion on how sensor strategy is brought to solve the macromolecules imprinting.

Immersion freezing of birch pollen washing water

NASA Astrophysics Data System (ADS)

Augustin, S.; Wex, H.; Niedermeier, D.; Pummer, B.; Grothe, H.; Hartmann, S.; Tomsche, L.; Clauss, T.; Voigtländer, J.; Ignatius, K.; Stratmann, F.

2013-11-01

Birch pollen grains are known to be ice nucleating active biological particles. The ice nucleating activity has previously been tracked down to biological macromolecules that can be easily extracted from the pollen grains in water. In the present study, we investigated the immersion freezing behavior of these ice nucleating active (INA) macromolecules. Therefore we measured the frozen fractions of particles generated from birch pollen washing water as a function of temperature at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). Two different birch pollen samples were considered, with one originating from Sweden and one from the Czech Republic. For the Czech and Swedish birch pollen samples, freezing was observed to start at -19 and -17 °C, respectively. The fraction of frozen droplets increased for both samples down to -24 °C. Further cooling did not increase the frozen fractions any more. Instead, a plateau formed at frozen fractions below 1. This fact could be used to determine the amount of INA macromolecules in the droplets examined here, which in turn allowed for the determination of nucleation rates for single INA macromolecules. The main differences between the Swedish birch pollen and the Czech birch pollen were obvious in the temperature range between -17 and -24 °C. In this range, a second plateau region could be seen for Swedish birch pollen. As we assume INA macromolecules to be the reason for the ice nucleation, we concluded that birch pollen is able to produce at least two different types of INA macromolecules. We were able to derive parameterizations for the heterogeneous nucleation rates for both INA macromolecule types, using two different methods: a simple exponential fit and the Soccer ball model. With these parameterization methods we were able to describe the ice nucleation behavior of single INA macromolecules from both the Czech and the Swedish birch pollen.

Effectively suppressing vanadium permeation in vanadium redox flow battery application with modified Nafion membrane with nacre-like nanoarchitectures

NASA Astrophysics Data System (ADS)

Zhang, Lesi; Ling, Ling; Xiao, Min; Han, Dongmei; Wang, Shuanjin; Meng, Yuezhong

2017-06-01

A novel self-assembled composite membrane, Nafion-[PDDA/ZrP]n with nacre-like nanostructures was successfully fabricated by a layer-by-layer (LbL) method and used as proton exchange membrane for vanadium redox flow battery applications. Poly(diallyldimethylammonium chloride) (PDDA) with positive charges and zirconium phosphate (ZrP) nanosheets with negative charges can form ultra-thin nacre-like nanostructure on the surface of Nafion membrane via the ionic crosslinking of tightly folded macromolecules. The lamellar structure of ZrP nanosheets and Donnan exclusion effect of PDDA can greatly decrease the vanadium ion permeability and improve the selectivity of proton conductivity. The fabricated Nafion-[PDDA/ZrP]4 membrane shows two orders of magnitude lower vanadium ion permeability (1.05 × 10-6 cm2 min-1) and 12 times higher ion selectivity than those of pristine Nafion membrane at room temperature. Consequently, the performance of vanadium redox flow batteries (VRFBs) assembled with Nafion-[PDDA/ZrP]3 membrane achieved a highly coulombic efficiency (CE) and energy efficiency (EE) together with a very slow self-discharge rate. When comparing with pristine Nafion VRFB, the CE and EE values of Nafion-[PDDA/ZrP]3 VRFB are 10% and 7% higher at 30 mA cm-2, respectively.

ProteinShader: illustrative rendering of macromolecules

PubMed Central

Weber, Joseph R

2009-01-01

Background Cartoon-style illustrative renderings of proteins can help clarify structural features that are obscured by space filling or balls and sticks style models, and recent advances in programmable graphics cards offer many new opportunities for improving illustrative renderings. Results The ProteinShader program, a new tool for macromolecular visualization, uses information from Protein Data Bank files to produce illustrative renderings of proteins that approximate what an artist might create by hand using pen and ink. A combination of Hermite and spherical linear interpolation is used to draw smooth, gradually rotating three-dimensional tubes and ribbons with a repeating pattern of texture coordinates, which allows the application of texture mapping, real-time halftoning, and smooth edge lines. This free platform-independent open-source program is written primarily in Java, but also makes extensive use of the OpenGL Shading Language to modify the graphics pipeline. Conclusion By programming to the graphics processor unit, ProteinShader is able to produce high quality images and illustrative rendering effects in real-time. The main feature that distinguishes ProteinShader from other free molecular visualization tools is its use of texture mapping techniques that allow two-dimensional images to be mapped onto the curved three-dimensional surfaces of ribbons and tubes with minimum distortion of the images. PMID:19331660

Anisotropic solvent model of the lipid bilayer. 1. Parameterization of long-range electrostatics and first solvation shell effects.

PubMed

Lomize, Andrei L; Pogozheva, Irina D; Mosberg, Henry I

2011-04-25

A new implicit solvation model was developed for calculating free energies of transfer of molecules from water to any solvent with defined bulk properties. The transfer energy was calculated as a sum of the first solvation shell energy and the long-range electrostatic contribution. The first term was proportional to solvent accessible surface area and solvation parameters (σ(i)) for different atom types. The electrostatic term was computed as a product of group dipole moments and dipolar solvation parameter (η) for neutral molecules or using a modified Born equation for ions. The regression coefficients in linear dependencies of solvation parameters σ(i) and η on dielectric constant, solvatochromic polarizability parameter π*, and hydrogen-bonding donor and acceptor capacities of solvents were optimized using 1269 experimental transfer energies from 19 organic solvents to water. The root-mean-square errors for neutral compounds and ions were 0.82 and 1.61 kcal/mol, respectively. Quantification of energy components demonstrates the dominant roles of hydrophobic effect for nonpolar atoms and of hydrogen-bonding for polar atoms. The estimated first solvation shell energy outweighs the long-range electrostatics for most compounds including ions. The simplicity and computational efficiency of the model allows its application for modeling of macromolecules in anisotropic environments, such as biological membranes.

Electron microscopic visualization of complementary labeled DNA with platinum-containing guanine derivative.

PubMed

Loukanov, Alexandre; Filipov, Chavdar; Mladenova, Polina; Toshev, Svetlin; Emin, Saim

2016-04-01

The object of the present report is to provide a method for a visualization of DNA in TEM by complementary labeling of cytosine with guanine derivative, which contains platinum as contrast-enhanced heavy element. The stretched single-chain DNA was obtained by modifying double-stranded DNA. The labeling method comprises the following steps: (i) stretching and adsorption of DNA on the support film of an electron microscope grid (the hydrophobic carbon film holding negative charged DNA); (ii) complementary labeling of the cytosine bases from the stretched single-stranded DNA pieces on the support film with platinum containing guanine derivative to form base-specific hydrogen bond; and (iii) producing a magnified image of the base-specific labeled DNA. Stretched single-stranded DNA on a support film is obtained by a rapid elongation of DNA pieces on the surface between air and aqueous buffer solution. The attached platinum-containing guanine derivative serves as a high-dense marker and it can be discriminated from the surrounding background of support carbon film and visualized by use of conventional TEM observation at 100 kV accelerated voltage. This method allows examination of specific nucleic macromolecules through atom-by-atom analysis and it is promising way toward future DNA-sequencing or molecular diagnostics of nucleic acids by electron microscopic observation. © 2016 Wiley Periodicals, Inc.

Measurement of Nonlinear Optical Properties of Single-Crystal Thin-Films of 3-Methyl-4-Methoxy-4'-Nitrostilbene (MMONS)

NASA Astrophysics Data System (ADS)

Tan, Shida; Bhowmik, Achintya; Thakur, Mrinal

2000-03-01

Excellent optical quality large area ( ~1 cm^2) single-crystal thin-films of MMONS were prepared by modified shear method.(M. Thakur and S. Meyler, Macromolecules 18, 2341 (1985); M. Thakur, Y. Shani, G. C. Chi, and K. O'Brien, Synth. Met. 28, D595 (1989).) This material belongs to mm2 point group.(D. Bierlein, L. K. Cheng, Y. Wang, and W. Tam, Appl. Phys. Lett. 56, 423 (1990).) Polarized optical microscopic and X-ray diffraction studies were performed to characterize the single-crystal films. The surface orientation of the films was (100). Polarized optical absorption measurements showed a large dichroism in the film as the molecules are oriented almost parallel to the film-plane. Using a mode-locked Nd:YAG laser ( ~100 ps, 82 MHz), the significant d-coefficients were determined by polarization selective SHG measurements, and the electro-optic coefficients were determined by field-induced birefringence measurements. The measured magnitudes of d- and r-coefficients are d_33=198±10 pm/V, d_32=78±5 pm/V, r_33=52±5 pm/V, and r_23=21±2 pm/V at 1064 nm. The results indicate that these films are promising for applications in guided-wave SHG and electro-optics.

Demonstration of 40 MHz thin-film electro-optic modulator using an organic molecular salt

NASA Astrophysics Data System (ADS)

Bhowmik, Achintya; Ahyi, Ayayi; Tan, Shida; Mishra, Alpana; Thakur, Mrinal

2000-03-01

Recently we reported the first demonstration of a single-pass thin-film electro-optic modulator based on a DAST single-crystal film.(M. Thakur, J. Xu, A. Bhowmik, and L. Zhou, Appl. Phys. Lett. 74, 635-637 (1999).) In this work, we report a larger modulation depth ( ~80%) and higher speed of operation. Excellent optical quality single-crystal films were prepared by a modified shear method.(M. Thakur and S. Meyler, Macromolecules 18, 2341 (1985); M. Thakur, Y. Shani, G. C. Chi, and K. O'Brien, Synth. Met. 28, D595 (1989).) Thin-film modulator was constructed by depositing electrodes across the polar axis. The beam from a Ti-Sapphire laser, tunable over 720-850 nm, was propagated perpendicular to the film surface. The modulated signal was detected using a fast photodetector, and displayed on a high bandwidth oscilloscope and a spectrum analyzer. The response was independent of the frequency of applied field over the measurement range (2 kHz - 40 MHz). A much higher speed (>100 GHz) of operation should be possible using these films. These modulators involve negligible losses compared to the waveguide structures, and have significant potential for a broad range of applications in high speed optical signal processing.

A theory for protein dynamics: Global anisotropy and a normal mode approach to local complexity

NASA Astrophysics Data System (ADS)

Copperman, Jeremy; Romano, Pablo; Guenza, Marina

2014-03-01

We propose a novel Langevin equation description for the dynamics of biological macromolecules by projecting the solvent and all atomic degrees of freedom onto a set of coarse-grained sites at the single residue level. We utilize a multi-scale approach where molecular dynamic simulations are performed to obtain equilibrium structural correlations input to a modified Rouse-Zimm description which can be solved analytically. The normal mode solution provides a minimal basis set to account for important properties of biological polymers such as the anisotropic global structure, and internal motion on a complex free-energy surface. This multi-scale modeling method predicts the dynamics of both global rotational diffusion and constrained internal motion from the picosecond to the nanosecond regime, and is quantitative when compared to both simulation trajectory and NMR relaxation times. Utilizing non-equilibrium sampling techniques and an explicit treatment of the free-energy barriers in the mode coordinates, the model is extended to include biologically important fluctuations in the microsecond regime, such as bubble and fork formation in nucleic acids, and protein domain motion. This work supported by the NSF under the Graduate STEM Fellows in K-12 Education (GK-12) program, grant DGE-0742540 and NSF grant DMR-0804145, computational support from XSEDE and ACISS.

Intramolecular Charge Transfer of Conjugated Liquid Crystal Ferrocene Macromolecules - Synthesis and Characterization

DTIC Science & Technology

2016-04-12

AFRL-AFOSR-CL-TR-2016-0012 Intramolecular Charge Transfer of Conjugated Liquid Crystal Ferrocene Macromolecules Ronald Ziolo CIQA Final Report 07/07...3. DATES COVERED (From - To)  15 Aug 2014 to 14 Jan 2016 4. TITLE AND SUBTITLE Intramolecular Charge Transfer of Conjugated Liquid Crystal Ferrocene...characterization of a new series of conjugated macromolecules bearing ferrocene as a highly efficient electron donor material coupled to 2,5-di(alcoxy) benzene

Dielectric 1/f noise of proton glass on a hydrated protein surface

NASA Astrophysics Data System (ADS)

Careri, Giorgio; Consolini, Giuseppe

2000-09-01

From nonexponentiality of dielectric relaxation detected in hydrated lysozyme powder we evaluate the power spectrum x2ω of the fluctuating dipole moment x¯2 of one macromolecule, due to the glass of protons migrating on the protein surface. Near room temperature, the contribution to the total dipole moment by the integrated strength of the 1/fα noise in the frequency range from 104 to 106 Hz, is well consistent with early Kirkwood's predictions in solution and more recent computations. The biochemical significance of the nonequilibrium region near the Vogel-Fulcher temperature T0~268 K calls for further investigations.

Fluorescent Approaches to High Throughput Crystallography

NASA Technical Reports Server (NTRS)

Minamitani, Elizabeth Forsythe; Pusey, Marc L.

2004-01-01

X-ray crystallography remains the primary method for determining the structure of macromolecules. The first requirement is to have crystals, and obtaining them is often the rate-limiting step. The numbers of crystallization trials that are set up for any one protein for structural genomics, and the rate at which they are being set up, now overwhelm the ability for strictly human analysis of the results. Automated analysis methods are now being implemented with varying degrees of success, but these typically cannot reliably extract intermediate results. By covalently modifying a subpopulation, less than or = 1%, of a macromolecule solution with a fluorescent probe, the labeled material will add to a growing crystal as a microheterogeneous growth unit. Labeling procedures can be readily incorporated into the final stages of a macromolecules purification. The covalently attached probe will concentrate in the crystal relative to the solution, and under fluorescent illumination the crystals will show up as bright objects against a dark background. As crystalline packing is more dense than amorphous precipitate, the fluorescence intensity can be used as a guide in distinguishing different types of precipitated phases, even in the absence of obvious crystalline features, widening the available potential lead conditions in the absence of clear "bits." Non-protein structures, such as salt crystals, will not incorporate the probe and will not show up under fluorescent illumination. Also, brightly fluorescent crystals are readily found against less fluorescent precipitated phases, which under white light illumination may serve to obscure the crystals. Automated image analysis to find crystals should be greatly facilitated, without having to first define crystallization drop boundaries and by having the protein or protein structures all that show up. The trace fluorescently labeled crystals will also emit with sufficient intensity to aid in the automation of crystal alignment using relatively low cost optics, further increasing throughput at synchrotrons. This presentation will focus on the methodology for fluorescent labeling, the crystallization results, and the effects of the trace labeling on the crystal quality.

Affinity Electrophoresis Using Ligands Attached To Polymers

NASA Technical Reports Server (NTRS)

Van Alstine, James M.; Snyder, Robert S.; Harris, J. M.; Brooks, D. E.

1990-01-01

In new technique, reduction of electrophoretic mobilities by addition of polyethylene glycol to ligands increases electrophoretic separabilities. In immuno-affinity electrophoresis, modification of ligands extends specificity of electrophoretic separation to particles having surface electric-charge structures otherwise making them electrophoretically inseparable. Modification of antibodies by polyethylene glycol greatly reduces ability to aggregate while enhancing ability to affect electrophoretic mobilities of cells. In hydrophobic-affinity electrophoresis, addition of polyethylene glycol reduces tendency toward aggregation of cells or macromolecules.

Organic semiconductor growth and morphology considerations for organic thin-film transistors.

PubMed

Virkar, Ajay A; Mannsfeld, Stefan; Bao, Zhenan; Stingelin, Natalie

2010-09-08

Analogous to conventional inorganic semiconductors, the performance of organic semiconductors is directly related to their molecular packing, crystallinity, growth mode, and purity. In order to achieve the best possible performance, it is critical to understand how organic semiconductors nucleate and grow. Clever use of surface and dielectric modification chemistry can allow one to control the growth and morphology, which greatly influence the electrical properties of the organic transistor. In this Review, the nucleation and growth of organic semiconductors on dielectric surfaces is addressed. The first part of the Review concentrates on small-molecule organic semiconductors. The role of deposition conditions on film formation is described. The modification of the dielectric interface using polymers or self-assembled mono-layers and their effect on organic-semiconductor growth and performance is also discussed. The goal of this Review is primarily to discuss the thin-film formation of organic semiconducting species. The patterning of single crystals is discussed, while their nucleation and growth has been described elsewhere (see the Review by Liu et. al).([¹]) The second part of the Review focuses on polymeric semiconductors. The dependence of physico-chemical properties, such as chain length (i.e., molecular weight) of the constituting macromolecule, and the influence of small molecular species on, e.g., melting temperature, as well as routes to induce order in such macromolecules, are described.

Partial ablation of stratum corneum by UV (193-nm) or IR (2.94-μm) pulsed lasers to enhance transdermal drug delivery rate

NASA Astrophysics Data System (ADS)

Fujiwara, Ai; Hinokitani, Toshihiro; Goto, Kenichi; Arai, Tsunenori

2004-07-01

To develop the noninvasive transdermal drug delivery system, pulsed lasers (argon-fluoride excimer laser (ArF laser) and erbium:yittrium aluminum garnet laser (Er:YAG laser)) were used to partially ablate the stratum corneum (SC), the upper layer of the skin. Because of the barrier function of the SC to drug permeation, the number of drugs especially macromolecules used in transdermal drug delivery system without skin irritation has been limited. Ultrastructural changes on the SC surface of ablated Yucatan micropig skin in vitro were observed with Environmental Scanning Electron Microscope. The result indicated that the structural changes varied according to each laser sources and irradiation conditions (laser fluences and numbers of pulses). Many granular structures of about 2 μm in diameter were observed in the ablated sites on ArF laser with lower fluence exposure (30 mJ/cm2, 200 pulses), and plane structures in the sites with higher fluence exposure (80 mJ/cm2, 80 pulses). In contrast, the ablation of Er:YAG laser created some pores of about 20 μm across on the surface of the SC. Under the irradiation condition of partial ablation, the skin permeability of macromolecule compound was enhanced. This partial SC ablation by pulsed laser could be possible candidate of the noninvasive transdermal drug delivery system with good physiological conditions of skin.

Synthesis and Characterization of a Chondroitin Sulfate Based Hybrid Bio/Synthetic Biomimetic Aggrecan Macromolecule

NASA Astrophysics Data System (ADS)

Sarkar, Sumona

Lower back pain resulting from intervertebral disc degeneration is one of the leading musculoskeletal disorders confronting our health system. In order to mechanically stabilize the disc early in the degenerative cascade and prevent the need for spinal fusion surgeries, we have proposed the development of a hybrid-bio/synthetic biomimetic proteoglycan macromolecule for injection into the disc in the early stages of degeneration. The goal of this thesis was to incorporate natural chondroitin sulfate (CS) chains into bottle brush polymer synthesis strategies for the fabrication of CS-macromolecules which mimic the proteoglycan structure and function while resisting enzymatic degradation. Both the "grafting-to" and "grafting-through" techniques of bottle brush synthesis were explored. CS was immobilized via a terminal primary amine onto a model polymeric backbone (polyacrylic acid) for investigation of the "grafting-to" strategy and an epoxy-amine step-growth polymerization technique was utilized for the "grafting-through" synthesis of CS-macromolecules with polyethylene glycol backbone segments. Incorporation of a synthetic polymeric backbone at the terminal amine of CS was confirmed via biochemical assays, 1H-NMR and FTIR spectroscopy, and CS-macromolecule size was demonstrated to be higher than that of natural CS via gel permeation chromatography, transmission electron microscopy and viscosity measurements. Further analysis of CS-macromolecule functionality indicated maintenance of natural CS properties such as high fixed charge density, high osmotic potential and low cytotoxicity with nucleus pulposus cells. These studies are the first attempt at the incorporation of natural CS into biomimetic bottle brush structures. CS-macromolecules synthesized via the methods developed in these studies may be utilized in the treatment and prevention of debilitating back pain as well as act as mimetics for other proteoglycans implicated in cartilage, heart valve, and nervous system tissue function.

Loss of Urinary Macromolecules in Mice Causes Interstitial and Intratubular Renal Calcification Dependent on the Underlying Conditions

NASA Astrophysics Data System (ADS)

Wu, Xue-Ru; Lieske, John C.; Evan, Andrew P.; Sommer, Andre J.; Liaw, Lucy; Mo, Lan

2008-09-01

Urinary protein macromolecules have long been thought to play a role in influencing the various phases of urolithiasis including nucleation, growth, aggregation of mineral crystals and their subsequent adhesion to the renal epithelial cells. However, compelling evidence regarding their precise role was lacking, due partly to the fact that most prior studies were done in vitro and results were highly variable depending on the experimental conditions. The advent of genetic engineering technology has made it possible to study urinary protein macromolecules within an in vivo biological system. Indeed, recent studies have begun to shed light on the net effects of loss of one or more macromolecules on the earliest steps of urolithiasis. This paper focuses on the in vivo consequences of inactivating Tamm-Horsfall protein and/or osteopontin, two major urinary glycoproteins, using the knockout approach. The renal phenotypes of both single and double knockout mice under spontaneous or hyperoxaluric conditions will be described. The functional significance of the urinary macromolecules as critical defense factors against renal calcification will also be discussed.

Amadori glycated proteins: role in production of autoantibodies in diabetes mellitus and effect of inhibitors on non-enzymatic glycation.

PubMed

Ansari, Nadeem A; Dash, Debabrata

2013-02-01

Nonenzymatic glycation of macromolecules, especially proteins leading to their oxidation is increased in diabetes mellitus due to hyperglycemia and play an important role in associated complications of the disease. The glycation primarily occurs at intrachain lysine residues of proteins and results in the formation of an early stage stable product as Amadori-lysine which undergo further irreversible chemical reactions to form advanced glycation endproducts. This review deals with the role of Amadori modified proteins in pathogenesis of diabetes. We aim to explain immunogenicity of Amadori-glycated proteins, which might be involve in production of serum autoantibodies in the diabetic patients, and effect of inhibitors on the glycation process.

Self-assembly of an amphiphilic macromolecule under spherical confinement: An efficient route to generate hollow nanospheres

NASA Astrophysics Data System (ADS)

Glagoleva, A. A.; Vasilevskaya, V. V.; Yoshikawa, K.; Khokhlov, A. R.

2013-12-01

In general, bio-macromolecules are composed of hydrophilic and hydrophobic moieties and are confined within small cavities, such as cell membranes and intracellular organelles. Here, we studied the self-organization of macromolecules having groups with different affinities to solvents under spherical nano-scale confinement by means of computer modeling. It is shown that depending on the interaction parameters of monomer units composed of side- and main-chain monomer groups along a single linear macromolecule and on cavity size, such amphiphilic polymers undergo the conformational transitions between hollow nanospheres, rod-like and folded cylindrical structures, and a necklace conformation with and without a particular ordering of beads. The diagram of the conformations in the variables the incompatibility parameter of monomer units and the cavity radius is constructed.

Production of polyimide ceria nanocomposites by development of molecular hook technology in nano-sonochemistry.

PubMed

Hatami, Mehdi

2018-06-01

Poly(amic acid), the precursor of polyimide (PI), was used for the preparation of PI/CeO 2 nanocomposites (NC)s by ultrasonic assisted technique via insertion of the surface modified CeO 2 nanoparticles (NP)s into PI matrix. In the preparation stages, in the first, the modifications of CeO 2 NPs by using hexadecyltrimethoxysilane (HDTMS) as a binder were targeted using ultrasonic waves. In the second step, newly designed PI structure was formed from the sonochemical imidization process as a molecular hook. In this step two different reactions were occurred. The acetic acid elimination reaction in the main chain of macromolecule, and the acetylation reaction in the side chains of poly(amic acid) were accomplished. By acetylation process the hook structure was created for trapping of the modified nanoparticles. In the final step the preparation of PI NCs were achieved by sonochemical process. The structural and thermal properties of pure PI and PI/CeO 2 NCs were studied by several techniques such as fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal analyses. FT-IR and 1 H NMR spectra confirmed the success in preparation of PI matrix. The FE-SEM, TEM, and AFM analyses showed the uniform distribution of CeO 2 NPs in PI matrix. The XRD patterns of NCs show the presence of crystalline CeO 2 NPs in amorphous PI matrix. The thermal analysis results reveal that, with increases in the content of CeO 2 NPs in PI matrix, the thermally stability factors of samples were improved. Copyright © 2018 Elsevier B.V. All rights reserved.

Mucin Agarose Gel Electrophoresis: Western Blotting for High-molecular-weight Glycoproteins.

PubMed

Ramsey, Kathryn A; Rushton, Zachary L; Ehre, Camille

2016-06-14

Mucins, the heavily-glycosylated proteins lining mucosal surfaces, have evolved as a key component of innate defense by protecting the epithelium against invading pathogens. The main role of these macromolecules is to facilitate particle trapping and clearance while promoting lubrication of the mucosa. During protein synthesis, mucins undergo intense O-glycosylation and multimerization, which dramatically increase the mass and size of these molecules. These post-translational modifications are critical for the viscoelastic properties of mucus. As a result of the complex biochemical and biophysical nature of these molecules, working with mucins provides many challenges that cannot be overcome by conventional protein analysis methods. For instance, their high-molecular-weight prevents electrophoretic migration via regular polyacrylamide gels and their sticky nature causes adhesion to experimental tubing. However, investigating the role of mucins in health (e.g., maintaining mucosal integrity) and disease (e.g., hyperconcentration, mucostasis, cancer) has recently gained interest and mucins are being investigated as a therapeutic target. A better understanding of the production and function of mucin macromolecules may lead to novel pharmaceutical approaches, e.g., inhibitors of mucin granule exocytosis and/or mucolytic agents. Therefore, consistent and reliable protocols to investigate mucin biology are critical for scientific advancement. Here, we describe conventional methods to separate mucin macromolecules by electrophoresis using an agarose gel, transfer protein into nitrocellulose membrane, and detect signal with mucin-specific antibodies as well as infrared fluorescent gel reader. These techniques are widely applicable to determine mucin quantitation, multimerization and to test the effects of pharmacological compounds on mucins.

Spectroscopic analysis of the powdery complex chitosan-iodine

NASA Astrophysics Data System (ADS)

Gegel, Natalia O.; Babicheva, Tatyana S.; Belyakova, Olga A.; Lugovitskaya, Tatyana N.; Shipovskaya, Anna B.

2018-04-01

A chitosan-iodine complex was obtained by modification of polymer powder in the vapor of an iodine-containing sorbate and studied by electron and IR spectroscopy, optical rotation dispersion. It was found that the electronic spectra of an aqueous solution of the modified chitosan (the source one and that stored for a year) showed intense absorption bands of triiodide and iodate ions, and also polyiodide ions, bound to the macromolecule by exciton bonding with charge transfer. Analysis of the IR spectra shows destruction of the network of intramolecular and intermolecular hydrogen bonds in the iodinated chitosan powder in comparison with the source polymer and the formation of a new chemical substance. E.g., the absorption band of deformation vibrations of the hydroxyl group disappears in the modified sample, and that of the protonated amino group shifts toward shorter wavelengths. The intensity of the stretching vibration band of the glucopyranose ring atoms significantly reduces. Heating of the modified sample at a temperature below the thermal degradation point of the polymer leads to stabilization of the chitosan-iodine complex. Based on our studies, the hydroxyl and amino groups of the aminopolysaccharide have been recognized as the centers of retention of polyiodide chains in the chitosan matrix.

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

Ortoleva, Peter J.

Illustrative embodiments of systems and methods for the deductive multiscale simulation of macromolecules are disclosed. In one illustrative embodiment, a deductive multiscale simulation method may include (i) constructing a set of order parameters that model one or more structural characteristics of a macromolecule, (ii) simulating an ensemble of atomistic configurations for the macromolecule using instantaneous values of the set of order parameters, (iii) simulating thermal-average forces and diffusivities for the ensemble of atomistic configurations, and (iv) evolving the set of order parameters via Langevin dynamics using the thermal-average forces and diffusivities.

Electronic Structure, Dielectric Response, and Surface Charge Distribution of RGD (1FUV) Peptide

PubMed Central

Adhikari, Puja; Wen, Amy M.; French, Roger H.; Parsegian, V. Adrian; Steinmetz, Nicole F.; Podgornik, Rudolf; Ching, Wai-Yim

2014-01-01

Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor. PMID:25001596

Self-assembled monolayers improve protein distribution on holey carbon cryo-EM supports

PubMed Central

Meyerson, Joel R.; Rao, Prashant; Kumar, Janesh; Chittori, Sagar; Banerjee, Soojay; Pierson, Jason; Mayer, Mark L.; Subramaniam, Sriram

2014-01-01

Poor partitioning of macromolecules into the holes of holey carbon support grids frequently limits structural determination by single particle cryo-electron microscopy (cryo-EM). Here, we present a method to deposit, on gold-coated carbon grids, a self-assembled monolayer whose surface properties can be controlled by chemical modification. We demonstrate the utility of this approach to drive partitioning of ionotropic glutamate receptors into the holes, thereby enabling 3D structural analysis using cryo-EM methods. PMID:25403871

Patterns of the adsorption of bovine serum albumin on carboxymethyl dextran and carboxymethyl cellulose films

NASA Astrophysics Data System (ADS)

Paribok, I. V.; Solomyanskii, A. E.; Zhavnerko, G. K.

2016-02-01

Patterns of the adsorption of bovine serum albumin on carboxymethyl dextran and carboxymethyl cellulose films are studied by means of microcontact printing, atomic force microscopy, and quartz crystal microbalance. It is shown that both the charge of polysaccharide macromolecules and the technique for deposition of their films onto the surface (via adsorption from a solution or covalent cross-linking) are factors that determine the degree of nonspecific adsorption of the protein on such films.

Study of structural and conformational change in cytochrome, C through molecular dynamic simulation in presence of gold nanoparticles

NASA Astrophysics Data System (ADS)

Moudgil, Lovika; Singh, Baljinder; Kaura, Aman; Singh, Gurinder; Tripathi, S. K.; Saini, G. S. S.

2017-05-01

Proteins are the most abundant organic molecules in living system having diverse structures and various functions than the other classes of macromolecules. We have done Molecular Dynamics (MD) simulation of the Cytochrome,C (Cyt,c) protein found in plants, animals and many unicellular animals in the presence of gold nanoparticles (Au NPs). MD results helped to recognize the amino acids that play important role to make the interaction possible between protein and gold surface. In the present study we have examined the structural change of protein in the presence of gold surface and its adsorption on the surface through MD simulations with the help of Gold-Protein (GolP) force field. Results were further analyzed to understand the protein interaction up to molecular level.

Motion of single wandering diblock-macromolecules directed by a PTFE nano-fence: real time SFM observations.

PubMed

Gallyamov, Marat O; Qin, Shuhui; Matyjaszewski, Krzysztof; Khokhlov, Alexei; Möller, Martin

2009-07-21

Using SFM we have observed a peculiar twisting motion of diblock macromolecules pre-collapsed in ethanol vapour during their subsequent spreading in water vapour. The intrinsic asymmetry of the diblock macromolecules has been considered to be the reason for such twisting. Further, friction-deposited PTFE nano-stripes have been employed as nano-trails with the purpose of inducing lateral directed motion of the asymmetric diblock macromolecules under cyclic impact from the changing vapour surroundings. Indeed, some of the macromolecules have demonstrated a certain tendency to orient along the PTFE stripes, and some of the oriented ones have moved occasionally in a directed manner along the trail. However, it has been difficult to reliably record such directed motion at the single molecule level due to some mobility of the PTFE nano-trails themselves in the changing vapour environment. In vapours, the PTFE stripes have demonstrated a distinct tendency towards conjunction. This tendency has manifested itself in efficient expelling of groups of the mobile brush-like molecules from the areas between two PTFE stripes joining in a zip-fastener manner. This different kind of vapour-induced cooperative macromolecular motion has been reliably observed as being directed. The PTFE nano-frame experiences some deformation when constraining the spreading macromolecules. We have estimated the possible force causing such deformation of the PTFE fence. The force has been found to be a few pN as calculated by a partial contribution from every single molecule of the constrained group.

Antimicrobial resistance challenged with metal-based antimicrobial macromolecules.

PubMed

Abd-El-Aziz, Alaa S; Agatemor, Christian; Etkin, Nola

2017-02-01

Antimicrobial resistance threatens the achievements of science and medicine, as it deactivates conventional antimicrobial therapeutics. Scientists respond to the threat by developing new antimicrobial platforms to prevent and treat infections from these resistant strains. Metal-based antimicrobial macromolecules are emerging as an alternative to conventional platforms because they combine multiple mechanisms of action into one platform due to the distinctive properties of metals. For example, metals interact with intracellular proteins and enzymes, and catalyse various intracellular processes. The macromolecular architecture offers a means to enhance antimicrobial activity since several antimicrobial moieties can be conjugated to the scaffold. Further, these macromolecules can be fabricated into antimicrobial materials for contact-killing medical implants, fabrics, and devices. As volatilization or leaching out of the antimicrobial moieties from the macromolecular scaffold is reduced, these medical implants, fabrics, and devices can retain their antimicrobial activity over an extended period. Recent advances demonstrate the potential of metal-based antimicrobial macromolecules as effective platforms that prevent and treat infections from resistant strains. In this review these advances are thoroughly discussed within the context of examples of metal-based antimicrobial macromolecules, their mechanisms of action and biocompatibility. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dermal and transdermal delivery of pharmaceutically relevant macromolecules.

PubMed

Münch, S; Wohlrab, J; Neubert, R H H

2017-10-01

The skin offers an attractive way for dermal and transdermal drug delivery that is why the drug still needs certain qualities to transcend the outermost layer of the skin, the stratum corneum. The requirements are: drugs with a maximum molecular weight of 1kDa, high lipophilicity and a certain polarity. This would restrict the use of a transdermal delivery of macromolecules, which would make the drug more effective in therapeutic administration. Various studies have shown that macromolecules without support do not penetrate the human skin. This effect can be achieved using physical and chemical methods, as well as biological peptides. The most popular physical method is the use of microneedles to create micropores in the skin and release the active agent in different sections. But also, other methods have been tested. Microjets, lasers, electroporation, sonophoresis and iontophoresis are also promising methods to successfully deliver dermal and transdermal macromolecules. Additionally, there are different penetration enhancer groups and biological peptides, which are also considered to be interesting approaches of enabling macromolecules to travel along the skin. All these methods will be described and evaluated in this review article. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantifying Nucleic Acid Ensembles with X-ray Scattering Interferometry.

PubMed

Shi, Xuesong; Bonilla, Steve; Herschlag, Daniel; Harbury, Pehr

2015-01-01

The conformational ensemble of a macromolecule is the complete description of the macromolecule's solution structures and can reveal important aspects of macromolecular folding, recognition, and function. However, most experimental approaches determine an average or predominant structure, or follow transitions between states that each can only be described by an average structure. Ensembles have been extremely difficult to experimentally characterize. We present the unique advantages and capabilities of a new biophysical technique, X-ray scattering interferometry (XSI), for probing and quantifying structural ensembles. XSI measures the interference of scattered waves from two heavy metal probes attached site specifically to a macromolecule. A Fourier transform of the interference pattern gives the fractional abundance of different probe separations directly representing the multiple conformation states populated by the macromolecule. These probe-probe distance distributions can then be used to define the structural ensemble of the macromolecule. XSI provides accurate, calibrated distance in a model-independent fashion with angstrom scale sensitivity in distances. XSI data can be compared in a straightforward manner to atomic coordinates determined experimentally or predicted by molecular dynamics simulations. We describe the conceptual framework for XSI and provide a detailed protocol for carrying out an XSI experiment. © 2015 Elsevier Inc. All rights reserved.

A Method for Decomposition of the Basic Reaction of Biological Macromolecules into Exponential Components

NASA Astrophysics Data System (ADS)

Barabash, Yu. M.; Lyamets, A. K.

2016-12-01

The structural and dynamical properties of biological macromolecules under non-equilibrium conditions determine the kinetics of their basic reaction to external stimuli. This kinetics is multiexponential in nature. This is due to the operation of various subsystems in the structure of macromolecules, as well as the effect of the basic reaction on the structure of macromolecules. The situation can be interpreted as a manifestation of the stationary states of macromolecules, which are represented by monoexponential components of the basic reaction (Monod-Wyman-Changeux model) Monod et al. (J Mol Cell Biol 12:88-118, 1965). The representation of multiexponential kinetics of the basic reaction in the form of a sum of exponential functions (A(t)={sum}_{i=1}^n{a}_i{e}^{-{k}_it}) is a multidimensional optimization problem. To solve this problem, a gradient method of optimization with software determination of the amount of exponents and reasonable calculation time is developed. This method is used to analyze the kinetics of photoinduced electron transport in the reaction centers (RC) of purple bacteria and the fluorescence induction in the granum thylakoid membranes which share a common function of converting light energy.

On Topological Indices of Certain Dendrimer Structures

NASA Astrophysics Data System (ADS)

Aslam, Adnan; Bashir, Yasir; Ahmad, Safyan; Gao, Wei

2017-05-01

A topological index can be considered as transformation of chemical structure in to real number. In QSAR/QSPR study, physicochemical properties and topological indices such as Randić, Zagreb, atom-bond connectivity ABC, and geometric-arithmetic GA index are used to predict the bioactivity of chemical compounds. Dendrimers are highly branched, star-shaped macromolecules with nanometer-scale dimensions. Dendrimers are defined by three components: a central core, an interior dendritic structure (the branches), and an exterior surface with functional surface groups. In this paper we determine generalised Randić, general Zagreb, general sum-connectivity indices of poly(propyl) ether imine, porphyrin, and zinc-Porphyrin dendrimers. We also compute ABC and GA indices of these families of dendrimers.

A new bead-spring model for simulation of semi-flexible macromolecules

NASA Astrophysics Data System (ADS)

Saadat, Amir; Khomami, Bamin

2016-11-01

A bead-spring model for semi-flexible macromolecules is developed to overcome the deficiencies of the current coarse-grained bead-spring models. Specifically, model improvements are achieved through incorporation of a bending potential. The new model is designed to accurately describe the correlation along the backbone of the chain, segmental length, and force-extension behavior of the macromolecule even at the limit of 1 Kuhn step per spring. The relaxation time of different Rouse modes is used to demonstrate the capabilities of the new model in predicting chain dynamics.

Predicting Nonspecific Ion Binding Using DelPhi

PubMed Central

Petukh, Marharyta; Zhenirovskyy, Maxim; Li, Chuan; Li, Lin; Wang, Lin; Alexov, Emil

2012-01-01

Ions are an important component of the cell and affect the corresponding biological macromolecules either via direct binding or as a screening ion cloud. Although some ion binding is highly specific and frequently associated with the function of the macromolecule, other ions bind to the protein surface nonspecifically, presumably because the electrostatic attraction is strong enough to immobilize them. Here, we test such a scenario and demonstrate that experimentally identified surface-bound ions are located at a potential that facilitates binding, which indicates that the major driving force is the electrostatics. Without taking into consideration geometrical factors and structural fluctuations, we show that ions tend to be bound onto the protein surface at positions with strong potential but with polarity opposite to that of the ion. This observation is used to develop a method that uses a DelPhi-calculated potential map in conjunction with an in-house-developed clustering algorithm to predict nonspecific ion-binding sites. Although this approach distinguishes only the polarity of the ions, and not their chemical nature, it can predict nonspecific binding of positively or negatively charged ions with acceptable accuracy. One can use the predictions in the Poisson-Boltzmann approach by placing explicit ions in the predicted positions, which in turn will reduce the magnitude of the local potential and extend the limits of the Poisson-Boltzmann equation. In addition, one can use this approach to place the desired number of ions before conducting molecular-dynamics simulations to neutralize the net charge of the protein, because it was shown to perform better than standard screened Coulomb canned routines, or to predict ion-binding sites in proteins. This latter is especially true for proteins that are involved in ion transport, because such ions are loosely bound and very difficult to detect experimentally. PMID:22735539

Crosslinking by ligands to surface immunoglobulin triggers mobilization of intracellular 45Ca2+ in B lymphocytes

PubMed Central

1979-01-01

Detailed studies of steady-state ion fluxes in murine lymphocytes were used to examine for possible ionic changes generated by surface Ig, the antigen receptor of B lymphocytes. When bound by ligands, surface Ig triggered the mobilization and release of 45Ca2+ from the cell interior by a transmembrane process requiring crosslinking of the bound receptors. This ionic event was unique for two reasons: (a) it did not occur when other common lymphocyte surface macromolecules were bound with rabbit anti-lymphocyte antibodies; and (b) it was not accompanied by a general perturbation of lymphocyte ionic properties such as a change in 42K+ fluxes nor did it depend on the presence of extracellular ions. Capping of surface Ig shares the same time sequence, dose response, requirement for crosslinking, and lack of dependence on extracellular ions. These correlations suggest that mobilization of intracellular Ca2+ may represent an early ionic signal for the contractile activation of lymphocytes that generates capping of surface Ig. PMID:315942

Surface Functionalization of Exosomes Using Click Chemistry

PubMed Central

2015-01-01

A method for conjugation of ligands to the surface of exosomes was developed using click chemistry. Copper-catalyzed azide alkyne cycloaddition (click chemistry) is ideal for biocojugation of small molecules and macromolecules to the surface of exosomes, due to fast reaction times, high specificity, and compatibility in aqueous buffers. Exosomes cross-linked with alkyne groups using carbodiimide chemistry were conjugated to a model azide, azide-fluor 545. Conjugation had no effect on the size of exosomes, nor was there any change in the extent of exosome adherence/internalization with recipient cells, suggesting the reaction conditions were mild on exosome structure and function. We further investigated the extent of exosomal protein modification with alkyne groups. Using liposomes with surface alkyne groups of a similar size and concentration to exosomes, we estimated that approximately 1.5 alkyne groups were present for every 150 kDa of exosomal protein. PMID:25220352

A simple, one-step hydrothermal approach to durable and robust superparamagnetic, superhydrophobic and electromagnetic wave-absorbing wood

NASA Astrophysics Data System (ADS)

Wang, Hanwei; Yao, Qiufang; Wang, Chao; Fan, Bitao; Sun, Qingfeng; Jin, Chunde; Xiong, Ye; Chen, Yipeng

2016-10-01

In this work, lamellar MnFe2O4 was successfully planted on a wood surface through the association of hydrogen bonds via the one-pot hydrothermal method. Simultaneously, the fluoroalkylsilane (FAS-17) on the surface of the MnFe2O4 layer formed long-chain or network macromolecules through a poly-condensation process and provided a lower surface energy on the wood surface. The MnFe2O4/wood composite (FMW) presented superior superparamagnetism, superhydrophobicity and electromagnetic wave absorption performance. The results indicated a saturation magnetization of the FMW with excellent superparamagnetism of 28.24 emu·g-1. The minimum value of reflection loss of the FMW reached -8.29 dB at 16.39 GHz with a thickness of 3 mm. Even after mechanical impact and exposure to corrosive liquids, the FMW still maintained a superior superhydrophobicity performance.

Single quantum dot tracking reveals the impact of nanoparticle surface on intracellular state.

PubMed

Zahid, Mohammad U; Ma, Liang; Lim, Sung Jun; Smith, Andrew M

2018-05-08

Inefficient delivery of macromolecules and nanoparticles to intracellular targets is a major bottleneck in drug delivery, genetic engineering, and molecular imaging. Here we apply live-cell single-quantum-dot imaging and tracking to analyze and classify nanoparticle states after intracellular delivery. By merging trajectory diffusion parameters with brightness measurements, multidimensional analysis reveals distinct and heterogeneous populations that are indistinguishable using single parameters alone. We derive new quantitative metrics of particle loading, cluster distribution, and vesicular release in single cells, and evaluate intracellular nanoparticles with diverse surfaces following osmotic delivery. Surface properties have a major impact on cell uptake, but little impact on the absolute cytoplasmic numbers. A key outcome is that stable zwitterionic surfaces yield uniform cytosolic behavior, ideal for imaging agents. We anticipate that this combination of quantum dots and single-particle tracking can be widely applied to design and optimize next-generation imaging probes, nanoparticle therapeutics, and biologics.

Intracellular uptake of macromolecules by brain lymphatic endothelial cells during zebrafish embryonic development.

PubMed

van Lessen, Max; Shibata-Germanos, Shannon; van Impel, Andreas; Hawkins, Thomas A; Rihel, Jason; Schulte-Merker, Stefan

2017-05-12

The lymphatic system controls fluid homeostasis and the clearance of macromolecules from interstitial compartments. In mammals brain lymphatics were only recently discovered, with significant implications for physiology and disease. We examined zebrafish for the presence of brain lymphatics and found loosely connected endothelial cells with lymphatic molecular signature covering parts of the brain without forming endothelial tubular structures. These brain lymphatic endothelial cells (BLECs) derive from venous endothelium, are distinct from macrophages, and are sensitive to loss of Vegfc. BLECs endocytose macromolecules in a selective manner, which can be blocked by injection of mannose receptor ligands. This first report on brain lymphatic endothelial cells in a vertebrate embryo identifies cells with unique features, including the uptake of macromolecules at a single cell level. Future studies will address whether this represents an uptake mechanism that is conserved in mammals and how these cells affect functions of the embryonic and adult brain.

Perfect mixing of immiscible macromolecules at fluid interfaces

NASA Astrophysics Data System (ADS)

Sheiko, Sergei; Matyjaszewski, Krzysztof; Tsukruk, Vladimir; Carrillo, Jan-Michael; Rubinstein, Michael; Dobrynin, Andrey; Zhou, Jing

2014-03-01

Macromolecules typically phase separate unless their shapes and chemical compositions are tailored to explicitly drive mixing. But now our research has shown that physical constraints can drive spontaneous mixing of chemically different species. We have obtained long-range 2D arrays of perfectly mixed macromolecules having a variety of molecular architectures and chemistries, including linear chains, block-copolymer stars, and bottlebrush copolymers with hydrophobic, hydrophilic, and lipophobic chemical compositions. This is achieved by entropy-driven enhancement of steric repulsion between macromolecules anchored on a substrate. By monitoring the kinetics of mixing, we have proved that molecular intercalation is an equilibrium state. The array spacing is controlled by the length of the brush side chains. This entropic templating strategy opens new ways for generating patterns on sub-100 nm length scales with potential application in lithography, directed self-assembly, and biomedical assays. Financial support from the National Science Foundation DMR-0906985, DMR-1004576, DMR-1122483, and DMR-0907515.

Scalable synthesis of sequence-defined, unimolecular macromolecules by Flow-IEG

PubMed Central

Leibfarth, Frank A.; Johnson, Jeremiah A.; Jamison, Timothy F.

2015-01-01

We report a semiautomated synthesis of sequence and architecturally defined, unimolecular macromolecules through a marriage of multistep flow synthesis and iterative exponential growth (Flow-IEG). The Flow-IEG system performs three reactions and an in-line purification in a total residence time of under 10 min, effectively doubling the molecular weight of an oligomeric species in an uninterrupted reaction sequence. Further iterations using the Flow-IEG system enable an exponential increase in molecular weight. Incorporating a variety of monomer structures and branching units provides control over polymer sequence and architecture. The synthesis of a uniform macromolecule with a molecular weight of 4,023 g/mol is demonstrated. The user-friendly nature, scalability, and modularity of Flow-IEG provide a general strategy for the automated synthesis of sequence-defined, unimolecular macromolecules. Flow-IEG is thus an enabling tool for theory validation, structure–property studies, and advanced applications in biotechnology and materials science. PMID:26269573

Genotoxic effect of N-hydroxy-4-acetylaminobiphenyl on human DNA: implications in bladder cancer.

PubMed

Shahab, Uzma; Moinuddin; Ahmad, Saheem; Dixit, Kiran; Habib, Safia; Alam, Khursheed; Ali, Asif

2013-01-01

The interaction of environmental chemicals and their metabolites with biological macromolecules can result in cytotoxic and genotoxic effects. 4-Aminobiphenyl (4-ABP) and several other related arylamines have been shown to be causally involved in the induction of human urinary bladder cancers. The genotoxic and the carcinogenic effects of 4-ABP are exhibited only when it is metabolically converted to a reactive electrophile, the aryl nitrenium ions, which subsequently binds to DNA and induce lesions. Although several studies have reported the formation of 4-ABP-DNA adducts, no extensive work has been done to investigate the immunogenicity of 4-ABP-modified DNA and its possible involvement in the generation of antibodies in bladder cancer patients. Human DNA was modified by N-hydroxy-4-acetylaminobiphenyl (N-OH-AABP), a reactive metabolite of 4-ABP. Structural perturbations in the N-OH-AABP modified DNA were assessed by ultraviolet, fluorescence, and circular dichroic spectroscopy as well as by agarose gel electrophoresis. Genotoxicity of N-OH-AABP modified DNA was ascertained by comet assay. High performance liquid chromatography (HPLC) analysis of native and modified DNA samples confirmed the formation of N-(deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-4ABP) in the N-OH-AABP damaged DNA. The experimentally induced antibodies against N-OH-AABP-modified DNA exhibited much better recognition of the DNA isolated from bladder cancer patients as compared to the DNA obtained from healthy individuals in competitive binding ELISA. This work shows epitope sharing between the DNA isolated from bladder cancer patients and the N-OH-AABP-modified DNA implicating the role of 4-ABP metabolites in the DNA damage and neo-antigenic epitope generation that could lead to the induction of antibodies in bladder cancer patients.

Dynamics of highly polydisperse colloidal suspensions as a model system for bacterial cytoplasm.

PubMed

Hwang, Jiye; Kim, Jeongmin; Sung, Bong June

2016-08-01

There are various kinds of macromolecules in bacterial cell cytoplasm. The size polydispersity of the macromolecules is so significant that the crystallization and the phase separation could be suppressed, thus stabilizing the liquid state of bacterial cytoplasm. On the other hand, recent experiments suggested that the macromolecules in bacterial cytoplasm should exhibit glassy dynamics, which should be also affected significantly by the size polydispersity of the macromolecules. In this work, we investigate the anomalous and slow dynamics of highly polydisperse colloidal suspensions, of which size distribution is chosen to mimic Escherichia coli cytoplasm. We find from our Langevin dynamics simulations that the diffusion coefficient (D_{tot}) and the displacement distribution functions (P(r,t)) averaged over all colloids of different sizes do not show anomalous and glassy dynamic behaviors until the system volume fraction ϕ is increased up to 0.82. This indicates that the intrinsic polydispersity of bacterial cytoplasm should suppress the glass transition and help maintain the liquid state of the cytoplasm. On the other hand, colloids of each kind show totally different dynamic behaviors depending on their size. The dynamics of colloids of different size becomes non-Gaussian at a different range of ϕ, which suggests that a multistep glass transition should occur. The largest colloids undergo the glass transition at ϕ=0.65, while the glass transition does not occur for smaller colloids in our simulations even at the highest value of ϕ. We also investigate the distribution (P(θ,t)) of the relative angles of displacement for macromolecules and find that macromolecules undergo directionally correlated motions in a sufficiently dense system.

Dynamics of highly polydisperse colloidal suspensions as a model system for bacterial cytoplasm

NASA Astrophysics Data System (ADS)

Hwang, Jiye; Kim, Jeongmin; Sung, Bong June

2016-08-01

There are various kinds of macromolecules in bacterial cell cytoplasm. The size polydispersity of the macromolecules is so significant that the crystallization and the phase separation could be suppressed, thus stabilizing the liquid state of bacterial cytoplasm. On the other hand, recent experiments suggested that the macromolecules in bacterial cytoplasm should exhibit glassy dynamics, which should be also affected significantly by the size polydispersity of the macromolecules. In this work, we investigate the anomalous and slow dynamics of highly polydisperse colloidal suspensions, of which size distribution is chosen to mimic Escherichia coli cytoplasm. We find from our Langevin dynamics simulations that the diffusion coefficient (Dtot) and the displacement distribution functions (P (r ,t ) ) averaged over all colloids of different sizes do not show anomalous and glassy dynamic behaviors until the system volume fraction ϕ is increased up to 0.82. This indicates that the intrinsic polydispersity of bacterial cytoplasm should suppress the glass transition and help maintain the liquid state of the cytoplasm. On the other hand, colloids of each kind show totally different dynamic behaviors depending on their size. The dynamics of colloids of different size becomes non-Gaussian at a different range of ϕ , which suggests that a multistep glass transition should occur. The largest colloids undergo the glass transition at ϕ =0.65 , while the glass transition does not occur for smaller colloids in our simulations even at the highest value of ϕ . We also investigate the distribution (P (θ ,t ) ) of the relative angles of displacement for macromolecules and find that macromolecules undergo directionally correlated motions in a sufficiently dense system.

A direct biocombinatorial strategy toward next generation, mussel-glue inspired saltwater adhesives.

PubMed

Wilke, Patrick; Helfricht, Nicolas; Mark, Andreas; Papastavrou, Georg; Faivre, Damien; Börner, Hans G

2014-09-10

Biological materials exhibit remarkable, purpose-adapted properties that provide a source of inspiration for designing new materials to meet the requirements of future applications. For instance, marine mussels are able to attach to a broad spectrum of hard surfaces under hostile conditions. Controlling wet-adhesion of synthetic macromolecules by analogue processes promises to strongly impact materials sciences by offering advanced coatings, adhesives, and glues. The de novo design of macromolecules to mimic complex aspects of mussel adhesion still constitutes a challenge. Phage display allows material scientists to design specifically interacting molecules with tailored affinity to material surfaces. Here, we report on the integration of enzymatic processing steps into phage display biopanning to expand the biocombinatorial procedure and enable the direct selection of enzymatically activable peptide adhesion domains. Adsorption isotherms and single molecule force spectroscopy show that those de novo peptides mimic complex aspects of bioadhesion, such as enzymatic activation (by tyrosinase), the switchability from weak to strong binders, and adsorption under hostile saltwater conditions. Furthermore, peptide-poly(ethylene oxide) conjugates are synthesized to generate protective coatings, which possess anti-fouling properties and suppress irreversible interactions with blood-plasma protein cocktails. The extended phage display procedure provides a generic way to non-natural peptide adhesion domains, which not only mimic nature but also improve biological sequence sections extractable from mussel-glue proteins. The de novo peptides manage to combine several tasks in a minimal 12-mer sequence and thus pave the way to overcome major challenges of technical wet glues.

Interstitial distribution of charged macromolecules in the dog lung: a kinetic model.

PubMed

Parker, J C; Miniati, M; Pitt, R; Taylor, A E

1987-01-01

A mathematic model was constructed to investigate conflicting physiologic data concerning the charge effect of continuous capillaries to macromolecules in the lung. We simulated the equilibration kinetics of lactate dehydrogenase (MR 4.2 nM) isozymes LDH 1 (pI = 5.0) and LDH 5 (pI = 7.9) between plasma and lymph using previously measured permeability coefficients, lung tissue distribution volumes (VA) and plasma concentrations (CP) in lung tissue. Our hypothesis is that the fixed anionic charges in interstitium, basement membrane, and cell surfaces determine equilibration rather than charged membrane effects at the capillary barrier, so the same capillary permeability coefficients were used for both isozymes. Capillary filtration rates and protein fluxes were calculated using conventional flux equations. Initial conditions at baseline and increased left atrial pressures (PLA) were those measured in animal studies. Simulated equilibration of isozymes over 30 h in the model at baseline capillary pressures accurately predicted the observed differences in lymph/plasma concentration ratios (CL/CP) between isotopes at 4 h and equilibration of these ratios at 24 h. Quantitative prediction of isozyme CL/CP ratios was also obtained at increased PLA. However, an additional cation selective compartment representing the surface glycocalyx was required to accurately simulate the initial higher transcapillary clearances of cationic LDH 5. Thus experimental data supporting the negative barrier, positive barrier, and no charge barrier hypotheses were accurately reproduced by the model using only the observed differences in interstitial partitioning of isozymes without differences in capillary selectivity.

Ligand Binding to Macromolecules: Allosteric and Sequential Models of Cooperativity.

ERIC Educational Resources Information Center

Hess, V. L.; Szabo, Attila

1979-01-01

A simple model is described for the binding of ligands to macromolecules. The model is applied to the cooperative binding by hemoglobin and aspartate transcarbamylase. The sequential and allosteric models of cooperative binding are considered. (BB)

Expression of the macrophage scavenger receptor, a multifunctional lipoprotein receptor, in microglia associated with senile plaques in Alzheimer's disease.

PubMed Central

Christie, R. H.; Freeman, M.; Hyman, B. T.

1996-01-01

The macrophage scavenger receptor is a multifunctional receptor whose ligands include oxidized low density lipoprotein (LDL), as well as several other polyanionic macromolecules. Although the capacity of the receptor to bind modified LDL has implicated it in the process of atherosclerosis, its physiological role remains uncertain. We have examined human brain for expression of macrophage scavenger receptor as part of ongoing studies of lipoprotein receptors in the central nervous system. The receptor is expressed on microglia, but not on astrocytes, neurons, or vessel-associated structures. In Alzheimer disease, there is strong expression of the scavenger receptor in association with senile plaques. Images Figure 2 Figure 3 Figure 4 PMID:8579103

Incorporation of antimicrobial macromolecules in acrylic denture base resins: a research composition and update.

PubMed

Sivakumar, Indumathi; Arunachalam, Kuthalingam Subbiah; Sajjan, Suresh; Ramaraju, Alluri Venkata; Rao, Bheemalingeshwara; Kamaraj, Bindu

2014-06-01

Contemporary research in acrylic denture base materials focuses on the development of a novel poly(methyl methacrylate) (PMMA) resin with antimicrobial properties. Although PMMA resin has fulfilled all the requirements of an ideal denture base material, its susceptibility to microbial colonization in the oral environment is a formidable concern to clinicians. Many mechanisms including the absence of ionic charge in the methyl methacrylate resins, hydrophobic interactions, electrostatic interactions, and mechanical attachment have been found to contribute to the formation of biofilm. The present article outlines the basic categories of potential antimicrobial polymer (polymeric biocides) formulations (modified PMMA resins) and considers their applicability, biological status, and usage potential over the coming years. © 2013 by the American College of Prosthodontists.

Amadori Glycated Proteins: Role in Production of Autoantibodies in Diabetes Mellitus and Effect of Inhibitors on Non-Enzymatic Glycation

PubMed Central

Ansari, Nadeem A.; Dash, Debabrata

2012-01-01

Nonenzymatic glycation of macromolecules, especially proteins leading to their oxidation is increased in diabetes mellitus due to hyperglycemia and play an important role in associated complications of the disease. The glycation primarily occurs at intrachain lysine residues of proteins and results in the formation of an early stage stable product as Amadori-lysine which undergo further irreversible chemical reactions to form advanced glycation endproducts. This review deals with the role of Amadori modified proteins in pathogenesis of diabetes. We aim to explain immunogenicity of Amadori-glycated proteins, which might be involve in production of serum autoantibodies in the diabetic patients, and effect of inhibitors on the glycation process. PMID:23423609

Atomic force microscopy of red-light photoreceptors using peakforce quantitative nanomechanical property mapping.

PubMed

Kroeger, Marie E; Sorenson, Blaire A; Thomas, J Santoro; Stojković, Emina A; Tsonchev, Stefan; Nicholson, Kenneth T

2014-10-24

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or "tapping mode" AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials. The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials.

Particle size, charge and colloidal stability of humic acids coprecipitated with Ferrihydrite.

PubMed

Angelico, Ruggero; Ceglie, Andrea; He, Ji-Zheng; Liu, Yu-Rong; Palumbo, Giuseppe; Colombo, Claudio

2014-03-01

Humic acids (HA) have a colloidal character whose size and negative charge are strictly dependent on surface functional groups. They are able to complex large amount of poorly ordered iron (hydr)oxides in soil as a function of pH and other environmental conditions. Accordingly, with the present study we intend to assess the colloidal properties of Fe(II) coprecipitated with humic acids (HA) and their effect on Fe hydroxide crystallinity under abiotic oxidation and order of addition of both Fe(II) and HA. TEM, XRD and DRS experiments showed that Fe-HA consisted of Ferrihydrite with important structural variations. DLS data of Fe-HA at acidic pH showed a bimodal size distribution, while at very low pH a slow aggregation process was observed. Electrophoretic zeta-potential measurements revealed a negative surface charge for Fe-HA macromolecules, providing a strong electrostatic barrier against aggregation. Under alkaline conditions HA chains swelled, which resulted in an enhanced stabilization of the colloid particles. The increasing of zeta potential and size of the Fe-HA macromolecules, reflects a linear dependence of both with pH. The increase in the size and negative charge of the Fe-HA precipitate seems to be more affected by the ionization of the phenolic acid groups, than by the carboxylic acid groups. The main cause of negative charge generation of Fe/HA is due to increased dissociation of phenolic groups in more expanded structure. The increased net negative surface potential induced by coprecipitation with Ferrihydrite and the correspondent changes in configuration of the HA could trigger the inter-particle aggregation with the formation of new negative surface. The Fe-HA coprecipitation can reduce electrosteric repulsive forces, which in turn may inhibit the aggregation process at different pH. Therefore, coprecipitation of Ferrihydrite would be expected to play an important role in the carbon stabilization and persistence not only in organic soils, but also in waters containing dissolved organic matter. Copyright © 2013 Elsevier Ltd. All rights reserved.

Development for equipment of the milk macromolecules content detection

NASA Astrophysics Data System (ADS)

Ding, Guochao; Li, Weimin; Shang, Tingyi; Xi, Yang; Gao, Yunli; Zhou, Zhen

Developed an experimental device for rapid and accurate detection of milk macromolecular content. This device developed based on laser scattered through principle, the principle use of the ingredients of the scattered light and transmitted light ratio characterization of macromolecules. Peristaltic pump to achieve automatic input and output of the milk samples, designing weak signal detection amplifier circuit for detecting the ratio with ICL7650. Real-time operating system μC / OS-II is the core design of the software part of the whole system. The experimental data prove that the device can achieve a fast real-time measurement of milk macromolecules.

The spectral properties of DNA and RNA macromolecules at low temperatures: fundamental and applied aspects

NASA Astrophysics Data System (ADS)

Yashchuk, Valeriy M.; Kudrya, Vladislav Yu

2017-03-01

This paper summarizes the results of studies of the spectral properties—optical absorption, fluorescence and phosphorescence—of DNA and RNA macromolecules and synthetic poly-, oligo- and mono-nucleotides, which have been carried out in our laboratory. The system of first excited singlet and triplet energy levels for DNA and RNA is evaluated using low-temperature (4.2 K-77 K) luminescent measurements. The traps of the singlet and triplet electronic excitations in these compounds are identified. An important self-protection mechanism against photo-damage of DNA and RNA by UV photons or penetrative radiation based on the capture of triplet electronic-energy excitations by the most photostable centers—in DNA, the complex formed by neighboring adenosine (A) and thymidine (T) links; in RNA, the adenosine links—is described. It is confirmed that despite similarities in the chemical and partly energy structures DNA is more stable than RNA. The spectral manifestation of the telomeres (the important functional system) in DNA macromolecules is examined. The results obtained on telomere fragments provide the possibility of finding the configuration peculiarities of the triplet excitations traps in DNA macromolecules. The resulting spreading length of the migrating singlet (l s) and triplet (l t) excitations for DNA and RNA macromolecules are evaluated.

Optimizing Multiple Analyte Injections in Surface Plasmon Resonance Biosensors with Analytes having Different Refractive Index Increments

PubMed Central

Mehand, Massinissa Si; Srinivasan, Bala; De Crescenzo, Gregory

2015-01-01

Surface plasmon resonance-based biosensors have been successfully applied to the study of the interactions between macromolecules and small molecular weight compounds. In an effort to increase the throughput of these SPR-based experiments, we have already proposed to inject multiple compounds simultaneously over the same surface. When specifically applied to small molecular weight compounds, such a strategy would however require prior knowledge of the refractive index increment of each compound in order to correctly interpret the recorded signal. An additional experiment is typically required to obtain this information. In this manuscript, we show that through the introduction of an additional global parameter corresponding to the ratio of the saturating signals associated with each molecule, the kinetic parameters could be identified with similar confidence intervals without any other experimentation. PMID:26515024

A new fluorescent nitrogen-doped carbon dot system modified by the fluorophore-labeled ssDNA for the analysis of 6-mercaptopurine and Hg (II).

PubMed

Li, Zhuo; Ni, Yongnian; Kokot, Serge

2015-12-15

A simple, environmentally friendly hydrothermal method was used to prepare strongly luminescent, nitrogen-doped carbon dots (NCDs) with the use of Chinese yams as a source of carbon and nitrogen. Such NCDs have an average size of 2.7±1.4 nm; they emit blue light at 420 nm and have a quantum yield of up to 9.3%. Thus, carboxyfluorescein (FAM)-DNA macro-molecules were assembled on the surfaces of the NCDs, and stabilised by strong π-π stacking; the so formed hybrid nano-sensors were found to have an ultra-sensitive response to 6-mercaptopurine (6-MP). A strong emission and enhancement of yellow radiation was observed from FAM. Furthermore, due to the specific interactions between DNA and Hg(2+), which resulted in the formation of the T-Hg(2+)-T (T: thymine base) complex - a large, conjugated system, which formed between NCDs, DNA and 6-MP, was broken up. Thus, the fluorescence from FAM was quenched. The detection limits for 6-MP and Hg(2+) were 0.67 and 1.26 nM, respectively. The proposed method was applied for the determination of 6-MP in human serum and Hg(2+) in water samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

Gating capacitive field-effect sensors by the charge of nanoparticle/molecule hybrids.

PubMed

Poghossian, Arshak; Bäcker, Matthias; Mayer, Dirk; Schöning, Michael J

2015-01-21

The semiconductor field-effect platform is a powerful tool for chemical and biological sensing with direct electrical readout. In this work, the field-effect capacitive electrolyte-insulator-semiconductor (EIS) structure - the simplest field-effect (bio-)chemical sensor - modified with citrate-capped gold nanoparticles (AuNPs) has been applied for a label-free electrostatic detection of charged molecules by their intrinsic molecular charge. The EIS sensor detects the charge changes in AuNP/molecule inorganic/organic hybrids induced by the molecular adsorption or binding events. The feasibility of the proposed detection scheme has been exemplarily demonstrated by realizing capacitive EIS sensors consisting of an Al-p-Si-SiO2-silane-AuNP structure for the label-free detection of positively charged cytochrome c and poly-d-lysine molecules as well as for monitoring the layer-by-layer formation of polyelectrolyte multilayers of poly(allylamine hydrochloride)/poly(sodium 4-styrene sulfonate), representing typical model examples of detecting small proteins and macromolecules and the consecutive adsorption of positively/negatively charged polyelectrolytes, respectively. For comparison, EIS sensors without AuNPs have been investigated, too. The adsorption of molecules on the surface of AuNPs has been verified via the X-ray photoelectron spectroscopy method. In addition, a theoretical model of the functioning of the capacitive field-effect EIS sensor functionalized with AuNP/charged-molecule hybrids has been discussed.

Free Surface Relaxations of Star-Shaped Polymer Films

DOE PAGES

Glynos, Emmanouil; Johnson, Kyle J.; Frieberg, Bradley; ...

2017-11-28

Here, the surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 degrees above the bulk glass transition temperature Tmore » $$bulk\\atop{g}$$. This behavior, exhibited by star-shaped polystyrenes (SPSs) with functionality f = 8 arms and molecular weights per arm M arm < M e (M e is the entanglement molecular weight), is shown by molecular dynamics simulations to be associated with a preferential localization of these macromolecules at the free surface. This new phenomenon is in notable contrast to that of linear chain polymer thin film systems where the surface relaxations are enhanced in relation to the bulk; this enhancement persists only for a limited temperature range above the bulk T$$bulk\\atop{g}$$. Finally, evidence of the slow surface dynamics, compared to the bulk, for temperatures well above T g and at length and time scales not associated with the glass transition has not previously been reported for polymers.« less

Imaging energy landscapes with concentrated diffusing colloidal probes

NASA Astrophysics Data System (ADS)

Bahukudumbi, Pradipkumar; Bevan, Michael A.

2007-06-01

The ability to locally interrogate interactions between particles and energetically patterned surfaces provides essential information to design, control, and optimize template directed self-assembly processes. Although numerous techniques are capable of characterizing local physicochemical surface properties, no current method resolves interactions between colloids and patterned surfaces on the order of the thermal energy kT, which is the inherent energy scale of equilibrium self-assembly processes. Here, the authors describe video microscopy measurements and an inverse Monte Carlo analysis of diffusing colloidal probes as a means to image three dimensional free energy and potential energy landscapes due to physically patterned surfaces. In addition, they also develop a consistent analysis of self-diffusion in inhomogeneous fluids of concentrated diffusing probes on energy landscapes, which is important to the temporal imaging process and to self-assembly kinetics. Extension of the concepts developed in this work suggests a general strategy to image multidimensional and multiscale physical, chemical, and biological surfaces using a variety of diffusing probes (i.e., molecules, macromolecules, nanoparticles, and colloids).

COMPUTATIONAL METHODS FOR STUDYING THE INTERACTION BETWEEN POLYCYCLIC AROMATIC HYDROCARBONS AND BIOLOGICAL MACROMOLECULES

EPA Science Inventory

Computational Methods for Studying the Interaction between Polycyclic Aromatic Hydrocarbons and Biological Macromolecules .

The mechanisms for the processes that result in significant biological activity of PAHs depend on the interaction of these molecules or their metabol...

MOLECULAR BIOLOGY OF PHARMACOLOGIC VITREOLYSIS

PubMed Central

Sebag, J

2005-01-01

Purpose Pharmacologic vitreolysis is a promising new therapy to improve vitreoretinal surgery and, ultimately, prevent disease by mitigating the contribution of vitreous to retinopathy. The mechanism of action of the agents being developed for pharmacologic vitreolysis remains unclear. The experiments in this thesis test the hypothesis that pharmacologic vitreolysis agents break down vitreous macromolecules into smaller particles. Methods Microplasmin, hyaluronidase, and collagenase were tested in solutions of hyaluronan (n = 15) and collagen (n = 15), explants of bovine vitreous (n = 15), dissected porcine vitreous (n = 9), and intact porcine eyes (n = 18). There were also 21 controls, totaling 93 specimens. Vitreous macromolecule sizes were determined with dynamic light scattering (DLS), performed at intervals from 10 minutes to 24 hours following injections. Results Studies of DLS reproducibility showed a coefficient of variance of less than 3.3% in all but one specimen. Microplasmin decreased porcine vitreous macromolecule size in a dose-dependent manner (correlation coefficient r = 0.93), with an 85% reduction after a 30-minute exposure to the maximum dose. Hyaluronidase decreased vitreous macromolecule size in hyaluronan solutions by 50% at high (1,000 IU/mL, P < .001) doses and in bovine vitreous by 20%. Collagenase decreased macromolecule size in collagen solutions by 20% at both low (1 mg/mL, P < .001) and high (10 mg/mL, P < .001) doses, but not at all in bovine vitreous. Conclusions Pharmacologic vitreolysis can induce a significant decrease in vitreous macromolecule sizes, depending upon the pharmacologic agents and the experimental model. Broad-spectrum agents were more effective than substrate-specific enzymes. Defining the molecular biology of pharmacologic vitreolysis has implications for surgical developments and may impact upon the design of clinical trials to induce prophylactic posterior vitreous detachment. PMID:17057814

Is it Possible to have the Similar Unit Cell in Crystals of Different form from the same Macromolecule? (A Case Study of Ribosome Crystals)

NASA Technical Reports Server (NTRS)

Karpova, E. A.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Three different types of ribosome crystals were grown by the vapor diffusion technique in hanging drops as described in (1,2). The ribosome is a large asymmetric RNA-protein complex (2.3 million Da), which is protein syntheses machinery of the cell. In this poster we would like to discuss the features of ribosome crystallization. Ribosomes were purified from the thermophilic bacteria Thermus thermophilus by centrifugation (3). Three types of crystals (needle, flat tetragonal and tetragonal-like pyramid) can be grown from the same solution; furthermore, in the same drop using 10-15% 2-methyl-2,4- pentanediol as a precipitant. The crystals appeared in 5-48 hours. The crystals were stable and can co-exist in solution over long period of time. The kinetics of appearance of different crystal forms was different: first the needle crystals were grown, then the tetragonal, and finally the tetragonal pyramids. Later studies of the process of ribosome crystal growth depending on supersaturation showed that low supersaturation results in the appearance of tetragonal plates or tetragonal-like pyramids. An electron microscopy study, together with computer modeling, has shown that crystals of different forms have a high probability of having the same unit cell parameters. According to these experiments the following conclusion can be dranvn: the level of supersaturation of the macromolecule in a crystallizing solution is one of the major factors for forming three-dimensional crystals convenient for X-rays diffraction analysis. From the same macromolecule solution, crystals of different forms can be grown at approximately the same conditions by varying the concentration of macromolecule in the solution. Ion-macromolecule and water-macromolecule interactions, apparently, play the main role in the formation of the unit cell of the crystals.

Identification of the prooxidant site of human ceruloplasmin: a model for oxidative damage by copper bound to protein surfaces

NASA Technical Reports Server (NTRS)

Mukhopadhyay, C. K.; Mazumder, B.; Lindley, P. F.; Fox, P. L.

1997-01-01

Free transition metal ions oxidize lipids and lipoproteins in vitro; however, recent evidence suggests that free metal ion-independent mechanisms are more likely in vivo. We have shown previously that human ceruloplasmin (Cp), a serum protein containing seven Cu atoms, induces low density lipoprotein oxidation in vitro and that the activity depends on the presence of a single, chelatable Cu atom. We here use biochemical and molecular approaches to determine the site responsible for Cp prooxidant activity. Experiments with the His-specific reagent diethylpyrocarbonate (DEPC) showed that one or more His residues was specifically required. Quantitative [14C]DEPC binding studies indicated the importance of a single His residue because only one was exposed upon removal of the prooxidant Cu. Plasmin digestion of [14C]DEPC-treated Cp (and N-terminal sequence analysis of the fragments) showed that the critical His was in a 17-kDa region containing four His residues in the second major sequence homology domain of Cp. A full length human Cp cDNA was modified by site-directed mutagenesis to give His-to-Ala substitutions at each of the four positions and was transfected into COS-7 cells, and low density lipoprotein oxidation was measured. The prooxidant site was localized to a region containing His426 because CpH426A almost completely lacked prooxidant activity whereas the other mutants expressed normal activity. These observations support the hypothesis that Cu bound at specific sites on protein surfaces can cause oxidative damage to macromolecules in their environment. Cp may serve as a model protein for understanding mechanisms of oxidant damage by copper-containing (or -binding) proteins such as Cu, Zn superoxide dismutase, and amyloid precursor protein.

Electrons, Photons, and Force: Quantitative Single-Molecule Measurements from Physics to Biology

PubMed Central

2011-01-01

Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution. PMID:21338175

Rationale for two phase polymer system microgravity separation experiments

NASA Technical Reports Server (NTRS)

Brooks, D. E.; Bamberger, S. B.; Harris, J. M.; Vanalstine, J.

1984-01-01

The two-phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) are mixed at concentrations above a few percent are discussed. They provide useful media for the partition and isolation of macromolecules and cell subpopulations. By manipulating their composition, separations based on a variety of molecular and surface properties are achieved, including membrane hydrophobic properties, cell surface charge, and membrane antigenicity. Work on the mechanism of cell partition shows there is a randomizing, nonthermal energy present which reduces separation resolution. This stochastic energy is probably associated with hydrodynamic interactions present during separation. Because such factors should be markedly reduced in microgravity, a series of shuttle experiments to indicate approaches to increasing the resolution of the procedure are planned.

Role of macromolecules in the safety of use of body wash cosmetics.

PubMed

Bujak, Tomasz; Wasilewski, Tomasz; Nizioł-Łukaszewska, Zofia

2015-11-01

One of the most challenging problems related to the use of surfactants in body wash cosmetics is their potential to cause skin irritations. Surfactants can bind with proteins, remove lipids from the epidermal surface, contribute to the disorganization of liquid crystal structures in the intercellular lipids, and interact with living skin cells. These processes can lead to skin irritations and allergic reactions, and impair the epidermal barrier function. The present study is an attempt to assess the effect of polymers and hydrolysed proteins present in the formulations of model body wash cosmetics on product properties. Special attention was given to the safety of use of this product type. The study examined three macromolecules: polyvinylpyrrolidone (PVP), hydrolysed wheat protein (HWP) and polyvinylpyrrolidone/hydrolysed wheat protein crosspolymer (PVP/HWP). The addition of the substances under study was found to improve the foaming properties of body wash cosmetics, increase their stability during storage, and contribute significantly to an improvement in the safety of product use by reducing the irritant potential. The strongest ability to reduce the skin irritation potential was determined for the formula enriched with the PVP/HWP crosspolymer. Copyright © 2015 Elsevier B.V. All rights reserved.

Polyhydroxyalkanoate from marine Bacillus megaterium using CSMCRI's Dry Sea Mix as a novel growth medium.

PubMed

Dhangdhariya, Jaykishan H; Dubey, Sonam; Trivedi, Hiral B; Pancha, Imran; Bhatt, Jwalant K; Dave, Bharti P; Mishra, Sandhya

2015-05-01

Oceans have significant potential to empower mankind and thus marine organisms are believed to be an enormous source for useful biomolecules. Polyhydroxyalkanoates (PHAs) are biological macromolecules that can be applied in nearly all fields. In the present study, Bacillus megaterium strain JK4h has been exploited for maximum PHB production using novel Dry Sea Mix (DSM) via Central Composite Design (CCD) of Response Surface Methodology (RSM) approach. The isolate was found to be producing 56.77% Cell Dry Weight (CDW) of PHAs within 24h, with optimized combinations of peptone, yeast extract and glucose. The PHB yield had been increased 2.61 fold compared to un-optimized experiments. The obtained PHA/PHB had been chemically characterized through Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The results indicate the successful optimization for maximum production of biological macromolecule and it was found to be highly pure polyhydroxybutyrate (PHB). Thus, DSM can be served as a novel and cost effective medium for PHA production offering the use of marine resources as a "green" sustainable alternative. Copyright © 2015 Elsevier B.V. All rights reserved.

Self-healing and thermoreversible rubber from supramolecular assembly.

PubMed

Cordier, Philippe; Tournilhac, François; Soulié-Ziakovic, Corinne; Leibler, Ludwik

2008-02-21

Rubbers exhibit enormous extensibility up to several hundred per cent, compared with a few per cent for ordinary solids, and have the ability to recover their original shape and dimensions on release of stress. Rubber elasticity is a property of macromolecules that are either covalently cross-linked or connected in a network by physical associations such as small glassy or crystalline domains, ionic aggregates or multiple hydrogen bonds. Covalent cross-links or strong physical associations prevent flow and creep. Here we design and synthesize molecules that associate together to form both chains and cross-links via hydrogen bonds. The system shows recoverable extensibility up to several hundred per cent and little creep under load. In striking contrast to conventional cross-linked or thermoreversible rubbers made of macromolecules, these systems, when broken or cut, can be simply repaired by bringing together fractured surfaces to self-heal at room temperature. Repaired samples recuperate their enormous extensibility. The process of breaking and healing can be repeated many times. These materials can be easily processed, re-used and recycled. Their unique self-repairing properties, the simplicity of their synthesis, their availability from renewable resources and the low cost of raw ingredients (fatty acids and urea) bode well for future applications.

Electric Birefringence: A Simple Apparatus for Determining Physical Parameters of Macromolecules and Colloids.

ERIC Educational Resources Information Center

Trimm, Harold H.; And Others

1984-01-01

Describes a birefringence apparatus that can be assembled for less than $100 and can be used to measure both the dimensions and dipole moments of many macromolecules. Details are given of the construction and manipulation of the apparatus. (JN)

A Course on Macromolecules.

ERIC Educational Resources Information Center

Horta, Arturo

1985-01-01

Describes a senior-level course that: (1) focuses on the structure and reactions of macromolecules; (2) treats industrial polymers in a unified way; and (3) uses analysis of conformation and conformational statistics as a unifying approach. Also discusses course topics, including polysaccharides, proteins, nucleic acids, and others. (JN)

Solid State Nuclear Magnetic Resonance Studies of the Murchison Organic Macromolecule

NASA Technical Reports Server (NTRS)

Cody, G. D., III; Alexander, C. M. OD.; Tera, F.

2001-01-01

We have used high speed H-1 (DEPTH) and C-13 (VACP MAS-slow spinning) solid state NMR to determine the contributions of protonated vs non-protonated carbon in the Murchison Macromolecule. Additional information is contained in the original extended abstract.

Intracellular uptake of macromolecules by brain lymphatic endothelial cells during zebrafish embryonic development

PubMed Central

van Lessen, Max; Shibata-Germanos, Shannon; van Impel, Andreas; Hawkins, Thomas A; Rihel, Jason; Schulte-Merker, Stefan

2017-01-01

The lymphatic system controls fluid homeostasis and the clearance of macromolecules from interstitial compartments. In mammals brain lymphatics were only recently discovered, with significant implications for physiology and disease. We examined zebrafish for the presence of brain lymphatics and found loosely connected endothelial cells with lymphatic molecular signature covering parts of the brain without forming endothelial tubular structures. These brain lymphatic endothelial cells (BLECs) derive from venous endothelium, are distinct from macrophages, and are sensitive to loss of Vegfc. BLECs endocytose macromolecules in a selective manner, which can be blocked by injection of mannose receptor ligands. This first report on brain lymphatic endothelial cells in a vertebrate embryo identifies cells with unique features, including the uptake of macromolecules at a single cell level. Future studies will address whether this represents an uptake mechanism that is conserved in mammals and how these cells affect functions of the embryonic and adult brain. DOI: http://dx.doi.org/10.7554/eLife.25932.001 PMID:28498105

Coding and decoding libraries of sequence-defined functional copolymers synthesized via photoligation

PubMed Central

Zydziak, Nicolas; Konrad, Waldemar; Feist, Florian; Afonin, Sergii; Weidner, Steffen; Barner-Kowollik, Christopher

2016-01-01

Designing artificial macromolecules with absolute sequence order represents a considerable challenge. Here we report an advanced light-induced avenue to monodisperse sequence-defined functional linear macromolecules up to decamers via a unique photochemical approach. The versatility of the synthetic strategy—combining sequential and modular concepts—enables the synthesis of perfect macromolecules varying in chemical constitution and topology. Specific functions are placed at arbitrary positions along the chain via the successive addition of monomer units and blocks, leading to a library of functional homopolymers, alternating copolymers and block copolymers. The in-depth characterization of each sequence-defined chain confirms the precision nature of the macromolecules. Decoding of the functional information contained in the molecular structure is achieved via tandem mass spectrometry without recourse to their synthetic history, showing that the sequence information can be read. We submit that the presented photochemical strategy is a viable and advanced concept for coding individual monomer units along a macromolecular chain. PMID:27901024

Electric field mediated loading of macromolecules in intact yeast cells is critically controlled at the wall level.

PubMed

Ganeva, V; Galutzov, B; Teissié, J

1995-12-13

The mechanism of electric field mediated macromolecule transfer inside an intact yeast cell was investigated by observing, under a microscope, the fluorescence associated to cells after pulsation in a buffer containing two different hydrophilic fluorescent dyes. In the case of a small probe such as propidium iodide, a long lived permeabilized state was induced by the field as classically observed on wall free systems. Penetration of a 70 kDa FITC dextran was obtained only by using drastic conditions and only a very limited number of yeast cells which took up macromolecules remained viable. Most dextrans were trapped in the wall. A dramatic improvement in transfer of dextrans was observed when the cells were treated by dithiothreitol before pulsation. A cytoplasmic protein leakage was detected after the electric treatment suggesting that an irreversible damage took place in the walls of many pulsed cells. Electroloading of macromolecules in intact yeast cells appears to be controlled by a field induced short lived alteration of the envelope organization.

Identifiability, reducibility, and adaptability in allosteric macromolecules.

PubMed

Bohner, Gergő; Venkataraman, Gaurav

2017-05-01

The ability of macromolecules to transduce stimulus information at one site into conformational changes at a distant site, termed "allostery," is vital for cellular signaling. Here, we propose a link between the sensitivity of allosteric macromolecules to their underlying biophysical parameters, the interrelationships between these parameters, and macromolecular adaptability. We demonstrate that the parameters of a canonical model of the mSlo large-conductance Ca 2+ -activated K + (BK) ion channel are non-identifiable with respect to the equilibrium open probability-voltage relationship, a common functional assay. We construct a reduced model with emergent parameters that are identifiable and expressed as combinations of the original mechanistic parameters. These emergent parameters indicate which coordinated changes in mechanistic parameters can leave assay output unchanged. We predict that these coordinated changes are used by allosteric macromolecules to adapt, and we demonstrate how this prediction can be tested experimentally. We show that these predicted parameter compensations are used in the first reported allosteric phenomena: the Bohr effect, by which hemoglobin adapts to varying pH. © 2017 Bohner and Venkataraman.

Identifiability, reducibility, and adaptability in allosteric macromolecules

PubMed Central

Bohner, Gergő

2017-01-01

The ability of macromolecules to transduce stimulus information at one site into conformational changes at a distant site, termed “allostery,” is vital for cellular signaling. Here, we propose a link between the sensitivity of allosteric macromolecules to their underlying biophysical parameters, the interrelationships between these parameters, and macromolecular adaptability. We demonstrate that the parameters of a canonical model of the mSlo large-conductance Ca2+-activated K+ (BK) ion channel are non-identifiable with respect to the equilibrium open probability-voltage relationship, a common functional assay. We construct a reduced model with emergent parameters that are identifiable and expressed as combinations of the original mechanistic parameters. These emergent parameters indicate which coordinated changes in mechanistic parameters can leave assay output unchanged. We predict that these coordinated changes are used by allosteric macromolecules to adapt, and we demonstrate how this prediction can be tested experimentally. We show that these predicted parameter compensations are used in the first reported allosteric phenomena: the Bohr effect, by which hemoglobin adapts to varying pH. PMID:28416647

Interphase vs confinement in starch-clay bionanocomposites.

PubMed

Coativy, Gildas; Chevigny, Chloé; Rolland-Sabaté, Agnès; Leroy, Eric; Lourdin, Denis

2015-03-06

Starch-clay bionanocomposites containing 1-10% of natural montmorillonite were elaborated by melt processing in the presence of water. A complex macromolecular dynamics behavior was observed: depending on the clay content, an increase of the glass transition temperature and/or the presence of two overlapped α relaxation peaks were detected. Thanks to a model allowing the prediction of the average interparticle distance, and its comparison with the average size of starch macromolecules, it was possible to associate these phenomena to different populations of macromolecules. In particular, it seems that for high clay content (10%), the slowdown of segmental relaxation due to confinement of the starch macromolecules between the clay tactoïds is the predominant phenomenon. While for lower clay contents (3-5%), a significant modification of chain relaxation seems to occur, due to the formation of an interphase by the starch macromolecules in the vicinity of clay nanoparticles coexisting with the bulk polymer. Copyright © 2014 Elsevier Ltd. All rights reserved.

Coding and decoding libraries of sequence-defined functional copolymers synthesized via photoligation.

PubMed

Zydziak, Nicolas; Konrad, Waldemar; Feist, Florian; Afonin, Sergii; Weidner, Steffen; Barner-Kowollik, Christopher

2016-11-30

Designing artificial macromolecules with absolute sequence order represents a considerable challenge. Here we report an advanced light-induced avenue to monodisperse sequence-defined functional linear macromolecules up to decamers via a unique photochemical approach. The versatility of the synthetic strategy-combining sequential and modular concepts-enables the synthesis of perfect macromolecules varying in chemical constitution and topology. Specific functions are placed at arbitrary positions along the chain via the successive addition of monomer units and blocks, leading to a library of functional homopolymers, alternating copolymers and block copolymers. The in-depth characterization of each sequence-defined chain confirms the precision nature of the macromolecules. Decoding of the functional information contained in the molecular structure is achieved via tandem mass spectrometry without recourse to their synthetic history, showing that the sequence information can be read. We submit that the presented photochemical strategy is a viable and advanced concept for coding individual monomer units along a macromolecular chain.

Efficient Intracellular siRNA Delivery by Ethyleneimine-Modified Amphiphilic Macromolecules

PubMed Central

Sparks, Sarah M.; Waite, Carolyn L.; Harmon, Alexander M.; Nusblat, Leora M.; Roth, Charles M.; Uhrich, Kathryn E.

2013-01-01

Summary New materials that can bind and deliver oligonucleotides such as short interfering RNA (siRNA) without toxicity are greatly needed to fulfill the promise of therapeutic gene silencing. Amphiphilic macromolecules (AMs) were functionalized with linear ethyleneimines to create cationic AMs capable of complexing with siRNA. Structurally, the parent AM is formed from a mucic acid backbone whose tetra-hydroxy groups are alkylated with 12-carbon aliphatic chains to form the hydrophobic component of the macromolecule. This alkylated mucic acid is then mono-functionalized with poly(ethylene glycol) (PEG) as a hydrophilic component. The resulting AM contains a free carboxylic acid within the hydrophobic domain. In this work, linear ethyleneimines were conjugated to the free carboxylic acid to produce an AM with one primary amine (1N) or one primary amine and four secondary amines (5N). Further, an AM with amine substitution both to the free carboxylic acid in the hydrophobic domain and also to the adjacent PEG was synthesized to produce a polymer with one primary amine and eight secondary amines (9N), four located on each side of the AM hydrophobic domain. All amine-functionalized AMs formed nanoscale micelles but only the 5N and 9N AMs had cationic zeta potentials, which increased with increasing number of amines. All AMs exhibited less inherent cytotoxicity than linear polyethyleneimine (L-PEI) at concentrations of 10 µM and above. By increasing the length of the cationic ethyleneimine chain and the total number of amines, successful siRNA complexation and cellular siRNA delivery was achieved in a malignant glioma cell line. In addition, siRNA-induced silencing of firefly luciferase was observed using complexes of siRNA with the 9N AM and comparable to L-PEI, yet showed better cell viability at higher concentrations (above 10 µM). This work highlights the promise of cationic AMs as safe and efficient synthetic vectors for siRNA delivery. Specifically, a novel polymer (9N) was identified for efficient siRNA delivery to cancer cells and will be further evaluated. PMID:21793212

Encapsulation of Nucleic Acids into Giant Unilamellar Vesicles by Freeze-Thaw: a Way Protocells May Form

NASA Astrophysics Data System (ADS)

Qiao, Hai; Hu, Na; Bai, Jin; Ren, Lili; Liu, Qing; Fang, Liaoqiong; Wang, Zhibiao

2017-12-01

Protocells are believed to consist of a lipid membrane and encapsulated nucleic acid. As the lipid membrane is impermeable to macromolecules like nucleic acids, the processes by which nucleic acids become encapsulated inside lipid membrane compartments are still unknown. In this paper, a freeze-thaw method was modified and applied to giant unilamellar vesicles (GUVs) and deoxyribonucleic acid (DNA) in mixed solution resulting in the efficient encapsulation of 6.4 kb plasmid DNA and similar length linear DNA into GUVs. The mechanism of encapsulation was followed by observing the effect of freeze-thaw temperatures on GUV morphological change, DNA encapsulation and ice crystal formation, and analyzing their correlation. Following ice crystal formation, the shape of spherical GUVs was altered and membrane integrity was damaged and this was found to be a necessary condition for encapsulation. Heating alone had no effects on DNA encapsulation, but was helpful for restoring the spherical shape and membrane integrity of GUVs damaged during freezing. These results suggested that freeze-thaw could promote the encapsulation of DNA into GUVs by a mechanism: the vesicle membrane was breached by ice crystal formation during freezing, DNA entered into damaged GUVs through these membrane gaps and was encapsulated after the membrane was resealed during the thawing process. The process described herein therefore describes a simple way for the encapsulation of nucleic acids and potentially other macromolecules into lipid vesicles, a process by which early protocells might have formed.

Spine and test skeletal matrices of the Mediterranean sea urchin Arbacia lixula--a comparative characterization of their sugar signature.

PubMed

Kanold, Julia M; Guichard, Nathalie; Immel, Françoise; Plasseraud, Laurent; Corneillat, Marion; Alcaraz, Gérard; Brümmer, Franz; Marin, Frédéric

2015-05-01

Calcified structures of sea urchins are biocomposite materials that comprise a minor fraction of organic macromolecules, such as proteins, glycoproteins and polysaccharides. These macromolecules are thought to collectively regulate mineral deposition during the process of calcification. When occluded, they modify the properties of the mineral. In the present study, the organic matrices (both soluble and insoluble in acetic acid) of spines and tests from the Mediterranean black sea urchin Arbacia lixula were extracted and characterized, in order to determine whether they exhibit similar biochemical signatures. Bulk characterizations were performed by mono-dimensional SDS/PAGE, FT-IR spectroscopy, and an in vitro crystallization assay. We concentrated our efforts on characterization of the sugar moieties. To this end, we determined the monosaccharide content of the soluble and insoluble organic matrices of A. lixula spines and tests by HPAE-PAD, together with their respective lectin-binding profiles via enzyme-linked lectin assay. Finally, we performed in situ localization of N-acetyl glucosamine-containing saccharides on spines and tests using gold-conjugated wheatgerm agglutinin. Our data show that the test and spine matrices exhibit different biochemical signatures with regard to their saccharidic fraction, suggesting that future studies should analyse the regulation of mineral deposition by the matrix in these two mineralized structures in detail. This study re-emphasizes the importance of non-protein moieties, i.e. sugars, in calcium carbonate systems, and highlights the need to clearly identify their function in the biomineralization process. © 2015 FEBS.

Effect of an alpha-blocker (Nicergoline) and of a beta-blocker (Acebutolol) on the in vitro biosynthesis of vascular extracellular matrix.

PubMed

Moczar, M; Robert, A M; Jacotot, B; Robert, L

2001-05-01

The effect of an alpha-blocking agent and of a beta-blocking agent on the biosynthesis of extracellular matrix macromolecules of the arterial wall was investigated. Rabbit aorta explants were cultured up to 48 hours with radioactive proline, lysine or glucosamine. In presence of these drugs, at concentration shown to be effective for the inhibition of platelet-endothelial cell interactions (10(-7) M), the incorporation of 14C proline in total macromolecular proline was higher than in macromolecular hydroxyproline suggesting a relatively higher rate of biosynthesis of non-collagenous proteins as compared to collagens. The alpha-blocking increased the incorporation of 14C proline in collagenous and non-collagenous proteins after 18 hours of incubation. beta-blocking also increased the incorporation of proline in macromolecular proline and hydroxyproline as compared to control cultures. Both increased the incorporation of 3H glucosamine in newly synthesised glycosaminoglycans. beta-blocking increased mainly the neosynthesis of heparan sulphate, alpha-blocking that of hyaluronan. The incorporation of 14C-lysine in crosslinked, insoluble elastin was not modified. These experiments confirm that alpha and beta-blocking agents can influence not only the tonus of aortic smooth muscle cells but also the relative rates of biosynthesis of extracellular matrix macromolecules. This effect should be taken in consideration for the evaluation of the long range effect of alpha and beta-blocking drugs on the vascular wall.

Constructing irregular surfaces to enclose macromolecular complexes for mesoscale modeling using the discrete surface charge optimization (DISCO) algorithm.

PubMed

Zhang, Qing; Beard, Daniel A; Schlick, Tamar

2003-12-01

Salt-mediated electrostatics interactions play an essential role in biomolecular structures and dynamics. Because macromolecular systems modeled at atomic resolution contain thousands of solute atoms, the electrostatic computations constitute an expensive part of the force and energy calculations. Implicit solvent models are one way to simplify the model and associated calculations, but they are generally used in combination with standard atomic models for the solute. To approximate electrostatics interactions in models on the polymer level (e.g., supercoiled DNA) that are simulated over long times (e.g., milliseconds) using Brownian dynamics, Beard and Schlick have developed the DiSCO (Discrete Surface Charge Optimization) algorithm. DiSCO represents a macromolecular complex by a few hundred discrete charges on a surface enclosing the system modeled by the Debye-Hückel (screened Coulombic) approximation to the Poisson-Boltzmann equation, and treats the salt solution as continuum solvation. DiSCO can represent the nucleosome core particle (>12,000 atoms), for example, by 353 discrete surface charges distributed on the surfaces of a large disk for the nucleosome core particle and a slender cylinder for the histone tail; the charges are optimized with respect to the Poisson-Boltzmann solution for the electric field, yielding a approximately 5.5% residual. Because regular surfaces enclosing macromolecules are not sufficiently general and may be suboptimal for certain systems, we develop a general method to construct irregular models tailored to the geometry of macromolecules. We also compare charge optimization based on both the electric field and electrostatic potential refinement. Results indicate that irregular surfaces can lead to a more accurate approximation (lower residuals), and the refinement in terms of the electric field is more robust. We also show that surface smoothing for irregular models is important, that the charge optimization (by the TNPACK minimizer) is efficient and does not depend on the initial assigned values, and that the residual is acceptable when the distance to the model surface is close to, or larger than, the Debye length. We illustrate applications of DiSCO's model-building procedure to chromatin folding and supercoiled DNA bound to Hin and Fis proteins. DiSCO is generally applicable to other interesting macromolecular systems for which mesoscale models are appropriate, to yield a resolution between the all-atom representative and the polymer level. Copyright 2003 Wiley Periodicals, Inc. J Comput Chem 24: 2063-2074, 2003

Single molecule optical measurements of orientation and rotations of biological macromolecules.

PubMed

Shroder, Deborah Y; Lippert, Lisa G; Goldman, Yale E

2016-11-22

Subdomains of macromolecules often undergo large orientation changes during their catalytic cycles that are essential for their activity. Tracking these rearrangements in real time opens a powerful window into the link between protein structure and functional output. Site-specific labeling of individual molecules with polarized optical probes and measurement of their spatial orientation can give insight into the crucial conformational changes, dynamics, and fluctuations of macromolecules. Here we describe the range of single molecule optical technologies that can extract orientation information from these probes, review the relevant types of probes and labeling techniques, and highlight the advantages and disadvantages of these technologies for addressing specific inquiries.

Multistage adsorption of diffusing macromolecules and viruses

NASA Astrophysics Data System (ADS)

Chou, Tom; D'Orsogna, Maria R.

2007-09-01

We derive the equations that describe adsorption of diffusing particles onto a surface followed by additional surface kinetic steps before being transported across the interface. Multistage surface kinetics occurs during membrane protein insertion, cell signaling, and the infection of cells by virus particles. For example, viral entry into healthy cells is possible only after a series of receptor and coreceptor binding events occurs at the cellular surface. We couple the diffusion of particles in the bulk phase with the multistage surface kinetics and derive an effective, integrodifferential boundary condition that contains a memory kernel embodying the delay induced by the surface reactions. This boundary condition takes the form of a singular perturbation problem in the limit where particle-surface interactions are short ranged. Moreover, depending on the surface kinetics, the delay kernel induces a nonmonotonic, transient replenishment of the bulk particle concentration near the interface. The approach generalizes that of Ward and Tordai [J. Chem. Phys. 14, 453 (1946)] and Diamant and Andelman [Colloids Surf. A 183-185, 259 (2001)] to include surface kinetics, giving rise to qualitatively new behaviors. Our analysis also suggests a simple scheme by which stochastic surface reactions may be coupled to deterministic bulk diffusion.

Thermodynamics of Macromolecular Association in Heterogeneous Crowding Environments: Theoretical and Simulation Studies with a Simplified Model.

PubMed

Ando, Tadashi; Yu, Isseki; Feig, Michael; Sugita, Yuji

2016-11-23

The cytoplasm of a cell is crowded with many different kinds of macromolecules. The macromolecular crowding affects the thermodynamics and kinetics of biological reactions in a living cell, such as protein folding, association, and diffusion. Theoretical and simulation studies using simplified models focus on the essential features of the crowding effects and provide a basis for analyzing experimental data. In most of the previous studies on the crowding effects, a uniform crowder size is assumed, which is in contrast to the inhomogeneous size distribution of macromolecules in a living cell. Here, we evaluate the free energy changes upon macromolecular association in a cell-like inhomogeneous crowding system via a theory of hard-sphere fluids and free energy calculations using Brownian dynamics trajectories. The inhomogeneous crowding model based on 41 different types of macromolecules represented by spheres with different radii mimics the physiological concentrations of macromolecules in the cytoplasm of Mycoplasma genitalium. The free energy changes of macromolecular association evaluated by the theory and simulations were in good agreement with each other. The crowder size distribution affects both specific and nonspecific molecular associations, suggesting that not only the volume fraction but also the size distribution of macromolecules are important factors for evaluating in vivo crowding effects. This study relates in vitro experiments on macromolecular crowding to in vivo crowding effects by using the theory of hard-sphere fluids with crowder-size heterogeneity.

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Surface modified magnesium hydroxide... Specific Chemical Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical... as surface modified magnesium hydroxide (PMN P-06-682) is subject to reporting under this section for...

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Surface modified magnesium hydroxide... Specific Chemical Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical... as surface modified magnesium hydroxide (PMN P-06-682) is subject to reporting under this section for...

Hydrophilization of Magnetic Nanoparticles with Modified Alternating Copolymers. Part 1: The Influence of the Grafting

PubMed Central

Bronstein, Lyudmila M.; Shtykova, Eleonora V.; Malyutin, Andrey; Dyke, Jason C.; Gunn, Emily; Gao, Xinfeng; Stein, Barry; Konarev, Peter V.; Dragnea, Bogdan; Svergun, Dmitri I.

2010-01-01

Iron oxide nanoparticles (NPs) with a diameter 21.6 nm were coated with poly(maleic acid-alt-1-octadecene) (PMAcOD) modified with grafted 5,000 Da poly(ethyelene glycol) (PEG) or short ethylene glycol (EG) tails. The coating procedure utilizes hydrophobic interactions of octadecene and oleic acid tails, while the hydrolysis of maleic anhydride moieties as well as the presence of hydrophilic PEG (EG) tails allows the NP hydrophilicity. The success of the NP coating was found to be independent of the degree of grafting which was varied between 20 and 80% of the –MacOD-units, but depended on the length of the grafted tail. The NP coating and hydrophilization did not occur when the modified copolymer contained 750 Da PEG tails independently of the grafting degree. To explain this phenomenon the micellization of the modified PMAcOD copolymers in water was analyzed by small angle x-ray scattering (SAXS). The PMAcOD molecules with the grafted 750 Da PEG tails form compact non-interacting disk-like micelles, whose stability apparently allows for no interactions with the NP hydrophobic shells. The PMAcOD containing the 5,000 Da PEG and EG tails form much larger aggregates capable of an efficient coating of the NPs. The coated NPs were characterized using transmission electron microscopy, dynamic light scattering, ζ-potential measurements, and thermal gravimetry analysis. The latter method demonstrated that the presence of long PEG tails in modified PMAcOD allows the attachment of fewer macromolecules (by a factor of ~20) compared to the case of non-modified or EG modified PMAcOD, emphasizing the importance of PEG tails in NP hydrophilization. The NPs coated with PMAcOD modified with 60% (towards all –MAcOD- units) of the 5,000 PEG tails bear a significant negative charge and display good stability in buffers. Such NPs can be useful as magnetic cores for virus-like particle formation. PMID:21221425

Surface modification to prevent oxide scale spallation

DOEpatents

Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A

2013-07-16

A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

Selective adsorption of oppositely charged PNIPAAM on halloysite surfaces: a route to thermo-responsive nanocarriers.

PubMed

Cavallaro, Giuseppe; Lazzara, Giuseppe; Lisuzzo, Lorenzo; Milioto, Stefana; Parisi, Filippo

2018-08-10

Halloysite nanotubes were functionalized with stimuli-responsive macromolecules to generate smart nanohybrids. Poly(N-isopropylacrylamide)-co-methacrylic acid (PNIPAAM-co-MA) was selectively adsorbed into halloysite lumen by exploiting electrostatic interactions. Amine-terminated PNIPAAM polymer was also investigated that selectively interacts with the outer surface of the nanotubes. The adsorption site has a profound effect on the thermodynamic behavior and therefore temperature responsive features of the hybrid material. The drug release kinetics was investigated by using diclofenac as a non-steroidal anti-inflammatory drug model. The release kinetics depends on the nanoarchitecture of the PNIPAAM/halloysite based material. In particular, diclofenac release was slowed down above the LCST for PNIPAAM-co-MA/halloysite. Opposite trends occurred for halloysite functionalized with PNIPAAM at the outer surface. This work represents a further step toward the opportunity to extend and control the delivery conditions of active species, which represent a key point in technological applications.

Raman structural study of melt-mixed blends of isotactic polypropylene with polyethylene of various densities

NASA Astrophysics Data System (ADS)

Prokhorov, K. A.; Nikolaeva, G. Yu; Sagitova, E. A.; Pashinin, P. P.; Guseva, M. A.; Shklyaruk, B. F.; Gerasin, V. A.

2018-04-01

We report a Raman structural study of melt-mixed blends of isotactic polypropylene with two grades of polyethylene: linear high-density and branched low-density polyethylenes. Raman methods, which had been suggested for the analysis of neat polyethylene and isotactic polypropylene, were modified in this study for quantitative analysis of polyethylene/polypropylene blends. We revealed the dependence of the degree of crystallinity and conformational composition of macromolecules in the blends on relative content of the blend components and preparation conditions (quenching or annealing). We suggested a simple Raman method for evaluation of the relative content of the components in polyethylene/polypropylene blends. The degree of crystallinity of our samples, evaluated by Raman spectroscopy, is in good agreement with the results of analysis by differential scanning calorimetry.

Investigating biomolecular recognition at the cell surface using atomic force microscopy.

PubMed

Wang, Congzhou; Yadavalli, Vamsi K

2014-05-01

Probing the interaction forces that drive biomolecular recognition on cell surfaces is essential for understanding diverse biological processes. Force spectroscopy has been a widely used dynamic analytical technique, allowing measurement of such interactions at the molecular and cellular level. The capabilities of working under near physiological environments, combined with excellent force and lateral resolution make atomic force microscopy (AFM)-based force spectroscopy a powerful approach to measure biomolecular interaction forces not only on non-biological substrates, but also on soft, dynamic cell surfaces. Over the last few years, AFM-based force spectroscopy has provided biophysical insight into how biomolecules on cell surfaces interact with each other and induce relevant biological processes. In this review, we focus on describing the technique of force spectroscopy using the AFM, specifically in the context of probing cell surfaces. We summarize recent progress in understanding the recognition and interactions between macromolecules that may be found at cell surfaces from a force spectroscopy perspective. We further discuss the challenges and future prospects of the application of this versatile technique. Copyright © 2014 Elsevier Ltd. All rights reserved.

Influence of impurities and contact scale on the lubricating properties of bovine submaxillary mucin (BSM) films on a hydrophobic surface.

PubMed

Nikogeorgos, Nikolaos; Madsen, Jan Busk; Lee, Seunghwan

2014-10-01

Lubricating properties of bovine submaxillary mucin (BSM) on a compliant, hydrophobic surface were studied as influenced by impurities, in particular bovine serum albumin (BSA), at macro and nanoscale contacts by means of pin-on-disk tribometry and friction force microscopy (FFM), respectively. At both contact scales, the purity of BSM and the presence of BSA were quantitatively discriminated. The presence of BSA was responsible for higher frictional forces observed from BSM samples containing relatively larger amount of BSA. But, the mechanisms contributing to higher friction forces by BSA were different at different contact scales. At the macroscale contact, higher friction forces were caused by faster and dominant adsorption of BSA into the contacting area under a continuous cycle of desorption and re-adsorption of the macromolecules from tribostress. Nevertheless, all BSMs lowered the interfacial friction forces due to large contact area and a large number of BSM molecules in the contact area. At the nanoscale contact, however, no significant desorption of the macromolecules is expected in tribological contacts because of too small contact area and extremely small number of BSM molecules involved in the contact area. Instead, increasingly higher friction forces with increasing amount of BSA in BSM layer are attributed to higher viscosity caused by BSA in the layer. Comparable size of AFM probes with BSM molecules allowed them to penetrate through the BSM layers and to scratch on the underlying substrates, and thus induced higher friction forces compared to the sliding contact on bare substrates. Copyright © 2014 Elsevier B.V. All rights reserved.

Surface modification of GC and HOPG with diazonium, amine, azide, and olefin derivatives.

PubMed

Tanaka, Mutsuo; Sawaguchi, Takahiro; Sato, Yukari; Yoshioka, Kyoko; Niwa, Osamu

2011-01-04

Surface modification of glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) was carried out with diazonium, amine, azide, and olefin derivatives bearing ferrocene as an electroactive moiety. Features of the modified surfaces were evaluated by surface concentrations of immobilized molecule, blocking effect of the modified surface against redox reaction, and surface observation using cyclic voltammetry and electrochemical scanning tunneling microscope (EC-STM). The measurement of surface concentrations of immobilized molecule revealed the following three aspects: (i) Diazonium and olefin derivatives could modify substrates with the dense-monolayer concentration. (ii) The surface concentration of immobilized amine derivative did not reach to the dense-monolayer concentration reflecting their low reactivity. (iii) The surface modification with the dense-monolayer concentration was also possible with azide derivative, but the modified surface contained some oligomers produced by the photoreaction of azides. Besides, the blocking effect against redox reaction was observed for GC modified with diazonium derivative and for HOPG modified with diazonium and azide derivatives, suggesting fabrication of a densely modified surface. Finally, the surface observation for HOPG modified with diazonium derivative by EC-STM showed a typical monolayer structure, in which the ferrocene moieties were packed densely at random. On the basis of those results, it was demonstrated that surface modification of carbon substrates with diazonium could afford a dense monolayer similar to the self-assembled monolayer (SAM) formation.

Surface characterization and free thyroid hormones response of chemically modified poly(ethylene terephthalate) blood collection tubes

NASA Astrophysics Data System (ADS)

Jalali Dil, Ebrahim; Kim, Samuel C.; Saffar, Amir; Ajji, Abdellah; Zare, Richard N.; Sattayapiwat, Annie; Esguerra, Vanessa; Bowen, Raffick A. R.

2018-06-01

The surface chemistry and surface energy of chemically modified polyethylene terephthalate (PET) blood collection tubes (BCTs) were studied and the results showed a significant increase in hydrophilicity and polarity of modified PET surface. The surface modification created nanometer-sized, needle-like asperities through molecular segregation at the surface. The surface dynamics of the modified PET was examined by tracking its surface properties over a 280-day period. The results showed surface rearrangement toward a surface with lower surface energy and fewer nanometer-sized asperities. Thromboelastography (TEG) was used to evaluate and compare the thrombogenicity of the inner walls of various types of BCTs. The TEG tracings and data from various types of BCTs demonstrated differences in the reactionand coagulation times but not in clot strength. The performance of the modified tubes in free triiodothyronine (FT3) and free thyroxine (FT4) hormone tests was examined, and it was found that the interference of modified PET tubes was negligible compared to that of commercially available PET BCTs.

Single molecule optical measurements of orientation and rotations of biological macromolecules

PubMed Central

Shroder, Deborah Y; Lippert, Lisa G; Goldman, Yale E

2016-01-01

The subdomains of macromolecules often undergo large orientation changes during their catalytic cycles that are essential for their activity. Tracking these rearrangements in real time opens a powerful window into the link between protein structure and functional output. Site-specific labeling of individual molecules with polarized optical probes and measuring their spatial orientation can give insight into the crucial conformational changes, dynamics, and fluctuations of macromolecules. Here we describe the range of single molecule optical technologies that can extract orientation information from these probes, we review the relevant types of probes and labeling techniques, and we highlight the advantages and disadvantages of these technologies for addressing specific inquiries. PMID:28192292

A primer in macromolecular linguistics.

PubMed

Searls, David B

2013-03-01

Polymeric macromolecules, when viewed abstractly as strings of symbols, can be treated in terms of formal language theory, providing a mathematical foundation for characterizing such strings both as collections and in terms of their individual structures. In addition this approach offers a framework for analysis of macromolecules by tools and conventions widely used in computational linguistics. This article introduces the ways that linguistics can be and has been applied to molecular biology, covering the relevant formal language theory at a relatively nontechnical level. Analogies between macromolecules and human natural language are used to provide intuitive insights into the relevance of grammars, parsing, and analysis of language complexity to biology. Copyright © 2012 Wiley Periodicals, Inc.

Microphase separation of comb copolymers with two different lengths of side chains

NASA Astrophysics Data System (ADS)

Aliev, M. A.; Kuzminyh, N. Yu.

2009-10-01

The phase behavior of the monodisperse AB comb copolymer melt contained the macromolecules of special architecture is discussed. Each macromolecule is assumed to be composed of two comb blocks which differ in numbers of side chains and numbers of monomer units in these chains. It is shown (by analysis of the structure factor of the melt) that microphase separation at two different length scales in the melt is possible. The large and small length scales correspond to separation between comb blocks and separation between monomer units in repeating fragments of blocks, respectively. The classification diagrams indicated which length scale is favored for a given parameters of chemical structure of macromolecules are constructed.

Mitochondrial transit peptide exhibits cell penetration ability and efficiently delivers macromolecules to mitochondria.

PubMed

Jain, Aastha; Chugh, Archana

2016-09-01

Mitochondrial malfunction under various circumstances can lead to a variety of disorders. Effective targeting of macromolecules (drugs) is important for restoration of mitochondrial function and treatment of related disorders. We have designed a novel cell-penetrating mitochondrial transit peptide (CpMTP) for delivery of macromolecules to mitochondria. Comparison between properties of cell-penetrating peptides (CPPs) and mitochondrial signal sequences enabled prediction of peptides with dual ability for cellular translocation and mitochondrial localization. Among the predicted peptides, CpMTP translocates across HeLa cells and shows successful delivery of noncovalently conjugated cargo molecules to mitochondria. CpMTP may have applications in transduction and transfection of mitochondria for therapeutics. © 2016 Federation of European Biochemical Societies.

High and low thermal conductivity of amorphous macromolecules

NASA Astrophysics Data System (ADS)

Xie, Xu; Yang, Kexin; Li, Dongyao; Tsai, Tsung-Han; Shin, Jungwoo; Braun, Paul V.; Cahill, David G.

2017-01-01

We measure the thermal conductivity, heat capacity and sound velocity of thin films of five polymers, nine polymer salts, and four caged molecules to advance the fundamental understanding of the lower and upper limits to heat conduction in amorphous macromolecules. The thermal conductivities vary by more than one order of magnitude, from 0.06 W m-1K-1 for [6,6]-phenyl-C71-butyric acid methyl ester to 0.67 W m-1K-1 for poly(vinylphosphonic acid calcium salt). Minimum thermal conductivity calculated from the measured sound velocity and effective atomic density is in good agreement with the thermal conductivity of macromolecules with various molecular structures and intermolecular bonding strength.

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

Glynos, Emmanouil; Johnson, Kyle J.; Frieberg, Bradley

Here, the surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 degrees above the bulk glass transition temperature Tmore » $$bulk\\atop{g}$$. This behavior, exhibited by star-shaped polystyrenes (SPSs) with functionality f = 8 arms and molecular weights per arm M arm < M e (M e is the entanglement molecular weight), is shown by molecular dynamics simulations to be associated with a preferential localization of these macromolecules at the free surface. This new phenomenon is in notable contrast to that of linear chain polymer thin film systems where the surface relaxations are enhanced in relation to the bulk; this enhancement persists only for a limited temperature range above the bulk T$$bulk\\atop{g}$$. Finally, evidence of the slow surface dynamics, compared to the bulk, for temperatures well above T g and at length and time scales not associated with the glass transition has not previously been reported for polymers.« less

Synchronized chaotic targeting and acceleration of surface chemistry in prebiotic hydrothermal microenvironments

PubMed Central

Priye, Aashish; Yu, Yuncheng; Hassan, Yassin A.; Ugaz, Victor M.

2017-01-01

Porous mineral formations near subsea alkaline hydrothermal vents embed microenvironments that make them potential hot spots for prebiotic biochemistry. But, synthesis of long-chain macromolecules needed to support higher-order functions in living systems (e.g., polypeptides, proteins, and nucleic acids) cannot occur without enrichment of chemical precursors before initiating polymerization, and identifying a suitable mechanism has become a key unanswered question in the origin of life. Here, we apply simulations and in situ experiments to show how 3D chaotic thermal convection—flows that naturally permeate hydrothermal pore networks—supplies a robust mechanism for focused accumulation at discrete targeted surface sites. This interfacial enrichment is synchronized with bulk homogenization of chemical species, yielding two distinct processes that are seemingly opposed yet synergistically combine to accelerate surface reaction kinetics by several orders of magnitude. Our results suggest that chaotic thermal convection may play a previously unappreciated role in mediating surface-catalyzed synthesis in the prebiotic milieu. PMID:28119504

Kinetic Roughening Transition and Energetics of Tetragonal Lysozyme Crystal Growth

NASA Technical Reports Server (NTRS)

Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

2004-01-01

Interpretation of lysozyme crystal growth rates using well-established physical theories enabled the discovery of a phenomenon possibly indicative of kinetic roughening. For example, lysozyme crystals grown above a critical supersaturation sigma, (where supersaturation sigma = ln c/c(sub eq), c = the protein concentration and c(sub eq) = the solubility concentration) exhibit microscopically rough surfaces due to the continuous addition of growth units anywhere on the surface of a crystal. The rate of crystal growth, V(sub c), for the continuous growth process is determined by the continuous flux of macromolecules onto a unit area of the crystal surface, a, from a distance, xi, per unit time due to diffusion, and a probability of attachment onto the crystal surface, expressed. Based upon models applied, the energetics of lysozyme crystal growth was determined. The magnitudes of the energy barriers of crystal growth for both the (110) and (101) faces of tetragonal lysozyme crystals are compared. Finally, evidence supportive of the kinetic roughening hypothesis is presented.

Polymer adsorption-driven self-assembly of nanostructures.

PubMed

Chakraborty, A K; Golumbfskie, A J

2001-01-01

Driven by prospective applications, there is much interest in developing materials that can perform specific functions in response to external conditions. One way to design such materials is to create systems which, in response to external inputs, can self-assemble to form structures that are functionally useful. This review focuses on the principles that can be employed to design macromolecules that when presented with an appropriate two-dimensional surface, will self-assemble to form nanostructures that may be functionally useful. We discuss three specific examples: (a) biomimetic recognition between polymers and patterned surfaces. (b) control and manipulation of nanomechanical motion generated by biopolymer adsorption and binding, and (c) creation of patterned nanostructuctures by exposing molten diblock copolymers to patterned surfaces. The discussion serves to illustrate how polymer sequence can be manipulated to affect self-assembly characteristics near adsorbing surfaces. The focus of this review is on theoretical and computational work aimed toward elucidating the principles underlying the phenomena pertinent to the three topics noted above. However, synergistic experiments are also described in the appropriate context.

Supramolecular Assembly of Comb-like Macromolecules Induced by Chemical Reactions that Modulate the Macromolecular Interactions In Situ.

PubMed

Xia, Hongwei; Fu, Hailin; Zhang, Yanfeng; Shih, Kuo-Chih; Ren, Yuan; Anuganti, Murali; Nieh, Mu-Ping; Cheng, Jianjun; Lin, Yao

2017-08-16

Supramolecular polymerization or assembly of proteins or large macromolecular units by a homogeneous nucleation mechanism can be quite slow and require specific solution conditions. In nature, protein assembly is often regulated by molecules that modulate the electrostatic interactions of the protein subunits for various association strengths. The key to this regulation is the coupling of the assembly process with a reversible or irreversible chemical reaction that occurs within the constituent subunits. However, realizing this complex process by the rational design of synthetic molecules or macromolecules remains a challenge. Herein, we use a synthetic polypeptide-grafted comb macromolecule to demonstrate how the in situ modulation of interactions between the charged macromolecules affects their resulting supramolecular structures. The kinetics of structural formation was studied and can be described by a generalized model of nucleated polymerization containing secondary pathways. Basic thermodynamic analysis indicated the delicate role of the electrostatic interactions between the charged subunits in the reaction-induced assembly process. This approach may be applicable for assembling a variety of ionic soft matters that are amenable to chemical reactions in situ.

Arachidonic acid with taurine enhances pulmonary absorption of macromolecules without any serious histopathological damages.

PubMed

Miyake, Masateru; Minami, Takanori; Yamazaki, Hiroyuki; Emoto, Chie; Mukai, Tadashi; Toguchi, Hajime

2017-05-01

Therapeutic peptides and protein are being used in several indications; however, their poor permeability still remains to be solved. This study focused on the pulmonary route of macromolecules. First, the effects of arachidonic acid (AA) as an absorption enhancer on drug serum concentration, after intratracheal administration, were investigated in rats. Second, the safety of AA was assessed in rats in an acute toxicity study for 7days. AA enhanced the exposure of both interferon-α (IFN-α) and fluorescein isothiocyanate 4000 (FD-4). In addition, the histopathological analysis indicated that AA caused alveolitis and bronchitis in rats. In combination with Taurine (Tau), these lung injuries were prevented through the histopathological analysis. The combined use of Tau with AA did not show any changes in the pharmacokinetics of FD-4. From these results, we suggest the combined use of AA with Tau as a novel formulation on the pulmonary route of macromolecule drugs. This formulation could improve the bioavailability of macromolecule drugs without any serious local damage to the lungs. Copyright © 2017 Elsevier B.V. All rights reserved.

Grafting molecularly imprinted poly(2-acrylamido-2-methylpropanesulfonic acid) onto the surface of carbon microspheres

NASA Astrophysics Data System (ADS)

Yang, Yongzhen; Zhang, Yan; Li, Sha; Liu, Xuguang; Xu, Bingshe

2012-06-01

Poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) was grafted on the surface of carbon microspheres (CMSs), which were modified in prior by a mixed acid (HNO3 and H2SO4) oxidation and 3-methacryloxypropyl trimethoxysilane silanization. Then, the molecularly imprinting polymerization was carried out towards the macromolecule PAMPS grafted on the surface of CMSs using dibenzothiophene (DBT) as template, ethylene dimethacrylate as cross-linking agent and (NH4)2S2O8 (APS) as initiator to prepare surface molecularly imprinted polymer (MIP-PAMPS/CMSs) for adsorbing DBT. The optimized conditions of grafting PAMPS, including AMPS dosage, APS content, reaction temperature and reaction time, were emphasized in this paper. The morphology of the samples was characterized by field emission scanning electron microscopy. The functional groups were analyzed qualitatively by Fourier transform infrared spectrometry. The grafting degree of PAMPS was investigated by thermogravimetry. The results show that the preferable AMPS dosage, APS content, reaction temperature and time were 5 g, 0.15 g, 70 °C and 12 h, respectively, for preparing PAMPS/CMSs composite on the basis of 1.0 g of silanized-CMSs. The absorbing characteristic of MIP-PAMPS/CMSs toward DBT was studied preliminarily with dynamic adsorption. In the experiment of dynamic adsorption, MIP-PAMPS/CMSs and non-imprinted polymer (NIP-PAMPS/CMSs) were compared with respect to their rapid adsorption in 1 mmol/L of DBT solution in n-hexane. When the first 1 mL of 1 mmol/L DBT solution was injected and flowed through a column packed with 0.1 g of MIP-PAMPS/CMSs, the content of DBT reduced to 0.265 mmol/L, that is, decreased significantly from 279 to 74 ppm. When 3 mL of DBT solution was flowed through the packed column, the adsorption of MIP-PAMPS/CMSs toward DBT reached saturation with the maximum adsorption amount of 1.38 × 10-2 mmol/g and the overall adsorption efficiency of 46%, while NIP-PAMPS/CMSs adsorbed only 1.66 × 10-3 mmol/g of DBT. It is suggested that the MIP-PAMPS/CMSs had much better adsorption property towards DBT than NIP-PAMPS/CMSs.

Route of steroid-activated macromolecules through nuclear pores imaged with atomic force microscopy.

PubMed

Oberleithner, H; Schäfer, C; Shahin, V; Albermann, L

2003-02-01

In eukaryotic cells, two concentric membranes, the nuclear envelope (NE), separate the nucleus from the cytoplasm. The NE is punctured by nuclear pore complexes (NPCs; molecular mass 120 MDa) that serve as regulated pathways for macromolecules entering and leaving the nuclear compartment. Transport across NPCs occurs through central channels. Such import and export of macromolecules through individual NPCs can be elicited in the Xenopus laevis oocyte by injecting the mineralocorticoid aldosterone and can be visualized with atomic force microscopy. The electrical NE resistance in intact cell nuclei can be measured in parallel. Resistance increases when macromolecules are engaged with the NPC. This article describe six observations made from these experiments and the conclusions that can be drawn from them. (i) A homogeneous population of macromolecules (approx. 100 kDa) attaches to the cytoplasmic face of the NPC 2 min after aldosterone injection. They are most likely to be aldosterone receptors. After a few minutes, they have disappeared. (ii) Large plugs (approx. molecular mass 1 MDa) appear in the central channels 20 min after hormone injection. They are most likely to be ribonucleoproteins exiting the nucleus. (iii) Electrical resistance measurements in isolated nuclei reveal transient electrical NE resistance peaks: an early (2 min) peak and a late (20 min) peak. Electrical peaks reflect macromolecule interaction with the NPC. (iv) Spironolactone blocks both the early and late peaks. This indicates that classic aldosterone receptors are involved in the pregenomic (early) and post-genomic (late) responses. (v) Actinomycin D and, independently, RNase A block the late electrical peak, confirming that plugs are genomic in nature. (vi) Intracellular calcium chelation blocks both early and late electrical peaks. Thus, the release of calcium from internal stores, which is known to be the first intracellular signal in response to aldosterone, is a prerequisite for the late genomic response.

Short communication: Evaluation of a sol-gel-based stainless steel surface modification to reduce fouling and biofilm formation during pasteurization of milk.

PubMed

Liu, Dylan Zhe; Jindal, Shivali; Amamcharla, Jayendra; Anand, Sanjeev; Metzger, Lloyd

2017-04-01

Milk fouling and biofilms are common problems in the dairy industry across many types of processing equipment. One way to reduce milk fouling and biofilms is to modify the characteristics of milk contact surfaces. This study examines the viability of using Thermolon (Porcelain Industries Inc., Dickson, TN), a sol-gel-based surface modification of stainless steel, during thermal processing of milk. We used stainless steel 316L (control) and sol-gel-modified coupons in this study to evaluate fouling behavior and bacterial adhesion. The surface roughness as measured by an optical profiler indicated that the control coupons had a slightly smoother finish. Contact angle measurements showed that the modified surface led to a higher water contact angle, suggesting a more hydrophobic surface. The modified surface also had a lower surface energy (32.4 ± 1.4 mN/m) than the control surface (41.36 ± 2.7 mN/m). We evaluated the susceptibility of control and modified stainless steel coupons to fouling in a benchtop plate heat exchanger. We observed a significant reduction in the amount of fouled layer on modified surfaces. We found an average fouling weight of 19.21 mg/cm 2 and 0.37 mg/cm 2 on the control and modified stainless steel coupons, respectively. We also examined the adhesion of Bacillus and biofilm formation, and observed that the modified stainless steel surface offered greater resistance to biofilm formation. Overall, the Thermolon-modified surface showed potential in the thermal processing of milk, offering significantly lower fouling and bacterial attachment than the control surface. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Wettability Control of Gold Surfaces Modified with Benzenethiol Derivatives: Water Contact Angle and Thermal Stability.

PubMed

Tatara, Shingo; Kuzumoto, Yasutaka; Kitamura, Masatoshi

2016-04-01

The water wettability of Au surfaces has been controlled using various benzenethiol derivatives including 4-methylbenzenethiol, pentafluorobenzenethiol, 4-flubrobenzenethiol, 4-methoxy-benzenethiol, 4-nitrobenzenethiol, and 4-hydroxybenzenethiol. The water contact angle of the Au surface modified with the benzenethiol derivative was found to vary in the wide range of 30.9° to 88.3°. The contact angle of the modified Au films annealed was also measured in order to investigate their thermal stability. The change in the contact angle indicated that the modified surface is stable at temperatures below about 400 K. Meanwhile, the activation energy of desorption from the modified surface was estimated from the change in the contact angle. The modified Au surface was also examined using X-ray photoelectron spectroscopy.

A Versatile Class of Cell Surface Directional Motors Gives Rise to Gliding Motility and Sporulation in Myxococcus xanthus

PubMed Central

Wartel, Morgane; Czerwinski, Fabian; Le Gall, Anne-Valérie; Mauriello, Emilia M. F.; Bergam, Ptissam; Brun, Yves V.; Shaevitz, Joshua; Mignot, Tâm

2013-01-01

Eukaryotic cells utilize an arsenal of processive transport systems to deliver macromolecules to specific subcellular sites. In prokaryotes, such transport mechanisms have only been shown to mediate gliding motility, a form of microbial surface translocation. Here, we show that the motility function of the Myxococcus xanthus Agl-Glt machinery results from the recent specialization of a versatile class of bacterial transporters. Specifically, we demonstrate that the Agl motility motor is modular and dissociates from the rest of the gliding machinery (the Glt complex) to bind the newly expressed Nfs complex, a close Glt paralogue, during sporulation. Following this association, the Agl system transports Nfs proteins directionally around the spore surface. Since the main spore coat polymer is secreted at discrete sites around the spore surface, its transport by Agl-Nfs ensures its distribution around the spore. Thus, the Agl-Glt/Nfs machineries may constitute a novel class of directional bacterial surface transporters that can be diversified to specific tasks depending on the cognate cargo and machinery-specific accessories. PMID:24339744

Recent advances in superhydrophobic surfaces and their relevance to biology and medicine.

PubMed

Ciasca, G; Papi, M; Businaro, L; Campi, G; Ortolani, M; Palmieri, V; Cedola, A; De Ninno, A; Gerardino, A; Maulucci, G; De Spirito, M

2016-02-04

By mimicking naturally occurring superhydrophobic surfaces, scientists can now realize artificial surfaces on which droplets of a few microliters of water are forced to assume an almost spherical shape and an extremely high contact angle. In recent decades, these surfaces have attracted much attention due to their technological applications for anti-wetting and self-cleaning materials. Very recently, researchers have shifted their interest to investigate whether superhydrophobic surfaces can be exploited to study biological systems. This research effort has stimulated the design and realization of new devices that allow us to actively organize, visualize and manipulate matter at both the microscale and nanoscale levels. Such precise control opens up wide applications in biomedicine, as it allows us to directly manipulate objects at the typical length scale of cells and macromolecules. This progress report focuses on recent biological and medical applications of superhydrophobicity. Particular regard is paid to those applications that involve the detection, manipulation and study of extremely small quantities of molecules, and to those that allow high throughput cell and biomaterial screening.

Sedimentation Coefficient, Frictional Coefficient, and Molecular Weight: A Preparative Ultracentrifuge Experiment for the Advanced Undergraduate Laboratory.

ERIC Educational Resources Information Center

Halsall, H. B.; Wermeling, J. R.

1982-01-01

Describes an experiment using a high-speed preparative centrifuge and calculator to demonstrate effects of the frictional coefficient of a macromolecule on its rate of transport in a force field and to estimate molecular weight of the macromolecule using an empirical relationship. Background information, procedures, and discussion of results are…

Tonal Interface to MacroMolecules (TIMMol): A Textual and Tonal Tool for Molecular Visualization

ERIC Educational Resources Information Center

Cordes, Timothy J.; Carlson, C. Britt; Forest, Katrina T.

2008-01-01

We developed the three-dimensional visualization software, Tonal Interface to MacroMolecules or TIMMol, for studying atomic coordinates of protein structures. Key features include audio tones indicating x, y, z location, identification of the cursor location in one-dimensional and three-dimensional space, textual output that can be easily linked…

Force spectroscopy of biomolecular folding and binding: theory meets experiment

NASA Astrophysics Data System (ADS)

Dudko, Olga

2015-03-01

Conformational transitions in biological macromolecules usually serve as the mechanism that brings biomolecules into their working shape and enables their biological function. Single-molecule force spectroscopy probes conformational transitions by applying force to individual macromolecules and recording their response, or ``mechanical fingerprints,'' in the form of force-extension curves. However, how can we decode these fingerprints so that they reveal the kinetic barriers and the associated timescales of a biological process? I will present an analytical theory of the mechanical fingerprints of macromolecules. The theory is suitable for decoding such fingerprints to extract the barriers and timescales. The application of the theory will be illustrated through recent studies on protein-DNA interactions and the receptor-ligand complexes involved in blood clot formation.

Iontophoretic transport of oligonucleotides across human epidermal membrane: a study of the Nernst-Planck model.

PubMed

Li, S K; Ghanem, A H; Teng, C L; Hardee, G E; Higuchi, W I

2001-07-01

The objective of this study was to investigate the transport behavior of a series of oligonucleotides with human epidermal membrane (HEM) and to examine the applicability of the modified NERNST-PLANCK model to transdermal iontophoresis of these macromolecules. Iontophoretic transport experiments were first carried out in a synthetic model membrane system (Nuclepore membranes) with a four-electrode potentiostat to examine the baseline modified NERNST-PLANCK model. The modified NERNST-PLANCK model derived from the Einstein relation and the Stokes-Einstein equation taken from previous work did not hold for the oligonucleotides. Results obtained in the Nuclepore studies were, however, consistent with predictions of the modified NERNST-PLANCK model using the experimentally determined electromobilities and diffusion coefficients. The electromobilities of the oligonucleotides (determined by capillary electrophoresis) were found to be more than a factor of two smaller than expected from the Einstein relation between electromobilities and diffusion coefficients (the latter determined in diffusion cell experiments). A correlation between these electromobilities and the theoretical electromobilities estimated by considering the effects of counterion binding and the effects of mobility reduction according to colloid theory was also observed. These results suggest that the modified NERNST-PLANCK model predictions are satisfactory only when the electromobilities and the effective molecular size of the oligonucleotides are known and are used directly to predict the iontophoretically enhanced transport. Results with the HEM experiments generally agreed with model predictions based on the experimental electromobilities. The oligonucleotide HEM flux data also suggest the existence of pores with effective pore radii greater than the effective radii estimated in previous studies with small molecular weight model permeants.

Computational screening of biomolecular adsorption and self-assembly on nanoscale surfaces.

PubMed

Heinz, Hendrik

2010-05-01

The quantification of binding properties of ions, surfactants, biopolymers, and other macromolecules to nanometer-scale surfaces is often difficult experimentally and a recurring challenge in molecular simulation. A simple and computationally efficient method is introduced to compute quantitatively the energy of adsorption of solute molecules on a given surface. Highly accurate summation of Coulomb energies as well as precise control of temperature and pressure is required to extract the small energy differences in complex environments characterized by a large total energy. The method involves the simulation of four systems, the surface-solute-solvent system, the solute-solvent system, the solvent system, and the surface-solvent system under consideration of equal molecular volumes of each component under NVT conditions using standard molecular dynamics or Monte Carlo algorithms. Particularly in chemically detailed systems including thousands of explicit solvent molecules and specific concentrations of ions and organic solutes, the method takes into account the effect of complex nonbond interactions and rotational isomeric states on the adsorption behavior on surfaces. As a numerical example, the adsorption of a dodecapeptide on the Au {111} and mica {001} surfaces is described in aqueous solution. Copyright 2009 Wiley Periodicals, Inc.

Ontogenetic changes in helminth membrane function.

PubMed

Arme, C

1988-01-01

During their life-cycle many parasites experience a wide range of environments including free living and those provided by a variety of intermediate and final hosts. The nutritional requirements of parasites are met by physiological processes adapted to exploit the physicochemical characteristics provided by different hosts. In helminth parasites these adaptations are frequently expressed on the tegumentary surface. As an example of adaptations within the Trematoda, the control of monosaccharide transport in Proterometra sp. is described. Environmental sodium, although not directly involved in the uptake process, nevertheless regulates the expression of transport capabilities. In the Cestoda, the uptake of monosaccharides and amino acids is described for Hymenolepis diminuta. The metacestode of this tapeworm inhabits the blood system of an arthropod, and the adult the gut of a mammal. There are quantitative and qualitative differences in the amino acids and monosaccharides in these two environments and these are reflected in the transport mechanisms exhibited by the two forms of the life-cycle. In Echinococcus granulosus the transfer of amino acids, sugars and macromolecules across the membranes of hydatid cysts and protoscoleces is described. The major difference between these two stages in the life-cycle relates to the ability of hydatid cysts to absorb macromolecules, whereas protoscoleces are impermeable to these compounds. The potential for future work is emphasized.

Bioinspired synthesis and self-assembly of hybrid organic–inorganic nanomaterials

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

Zhang, Honghu

Nature is replete with complex organic–inorganic hierarchical materials of diverse yet specific functions. These materials are intricately designed under physiological conditions through biomineralization and biological self-assembly processes. Tremendous efforts have been devoted to investigating mechanisms of such biomineralization and biological self-assembly processes as well as gaining inspiration to develop biomimetic methods for synthesis and self-assembly of functional nanomaterials. In this work, we focus on the bioinspired synthesis and self-assembly of functional inorganic nanomaterials templated by specialized macromolecules including proteins, DNA and polymers. The in vitro biomineralization process of the magnetite biomineralizing protein Mms6 has been investigated using small-angle X-ray scattering.more » Templated by Mms6, complex magnetic nanomaterials can be synthesized on surfaces and in the bulk. DNA and synthetic polymers have been exploited to construct macroscopic two- and three-dimensional (2D and 3D) superlattices of gold nanocrystals. Employing X-ray scattering and spectroscopy techniques, the self-assembled structures and the self-assembly mechanisms have been studied, and theoretical models have been developed. Our results show that specialized macromolecules including proteins, DNA and polymers act as effective templates for synthesis and self-assembly of nanomaterials. These bottom-up approaches provide promising routes to fabricate hybrid organic–inorganic nanomaterials with rationally designed hierarchical structures, targeting specific functions.« less

PDB_Hydro: incorporating dipolar solvents with variable density in the Poisson-Boltzmann treatment of macromolecule electrostatics.

PubMed

Azuara, Cyril; Lindahl, Erik; Koehl, Patrice; Orland, Henri; Delarue, Marc

2006-07-01

We describe a new way to calculate the electrostatic properties of macromolecules which eliminates the assumption of a constant dielectric value in the solvent region, resulting in a Generalized Poisson-Boltzmann-Langevin equation (GPBLE). We have implemented a web server (http://lorentz.immstr.pasteur.fr/pdb_hydro.php) that both numerically solves this equation and uses the resulting water density profiles to place water molecules at preferred sites of hydration. Surface atoms with high or low hydration preference can be easily displayed using a simple PyMol script, allowing for the tentative prediction of the dimerization interface in homodimeric proteins, or lipid binding regions in membrane proteins. The web site includes options that permit mutations in the sequence as well as reconstruction of missing side chain and/or main chain atoms. These tools are accessible independently from the electrostatics calculation, and can be used for other modeling purposes. We expect this web server to be useful to structural biologists, as the knowledge of solvent density should prove useful to get better fits at low resolution for X-ray diffraction data and to computational biologists, for whom these profiles could improve the calculation of interaction energies in water between ligands and receptors in docking simulations.

Ion Transport in Confined Geometries below the Nanoscale: Access Resistance Dominates Protein Channel Conductance in Diluted Solutions.

PubMed

Alcaraz, Antonio; López, M Lidón; Queralt-Martín, María; Aguilella, Vicente M

2017-10-24

Synthetic nanopores and mesoscopic protein channels have common traits like the importance of electrostatic interactions between the permeating ions and the nanochannel. Ion transport at the nanoscale occurs under confinement conditions so that the usual assumptions made in microfluidics are challenged, among others, by interfacial effects such as access resistance (AR). Here, we show that a sound interpretation of electrophysiological measurements in terms of channel ion selective properties requires the consideration of interfacial effects, up to the point that they dominate protein channel conductance in diluted solutions. We measure AR in a large ion channel, the bacterial porin OmpF, by means of single-channel conductance measurements in electrolyte solutions containing varying concentrations of high molecular weight PEG, sterically excluded from the pore. Comparison of experiments performed in charged and neutral planar membranes shows that lipid surface charges modify the ion distribution and determine the value of AR, indicating that lipid molecules are more than passive scaffolds even in the case of large transmembrane proteins. We also found that AR may reach up to 80% of the total channel conductance in diluted solutions, where electrophysiological recordings register essentially the AR of the system and depend marginally on the pore characteristics. These findings may have implications for several low aspect ratio biological channels that perform their physiological function in a low ionic strength and macromolecule crowded environment, just the two conditions enhancing the AR contribution.

Conducting nanowires built by controlled self-assembly of amyloid fibers and selective metal deposition.

PubMed

Scheibel, Thomas; Parthasarathy, Raghuveer; Sawicki, George; Lin, Xiao-Min; Jaeger, Heinrich; Lindquist, Susan L

2003-04-15

Recent research in the field of nanometer-scale electronics has focused on the operating principles of small-scale devices and schemes to realize useful circuits. In contrast to established "top-down" fabrication techniques, molecular self-assembly is emerging as a "bottom-up" approach for fabricating nanostructured materials. Biological macromolecules, especially proteins, provide many valuable properties, but poor physical stability and poor electrical characteristics have prevented their direct use in electrical circuits. Here we describe the use of self-assembling amyloid protein fibers to construct nanowire elements. Self-assembly of a prion determinant from Saccharomyces cerevisiae, the N-terminal and middle region (NM) of Sup35p, produced 10-nm-wide protein fibers that were stable under a wide variety of harsh physical conditions. Their lengths could be roughly controlled by assembly conditions in the range of 60 nm to several hundred micrometers. A genetically modified NM variant that presents reactive, surface-accessible cysteine residues was used to covalently link NM fibers to colloidal gold particles. These fibers were placed across gold electrodes, and additional metal was deposited by highly specific chemical enhancement of the colloidal gold by reductive deposition of metallic silver and gold from salts. The resulting silver and gold wires were approximately 100 nm wide. These biotemplated metal wires demonstrated the conductive properties of a solid metal wire, such as low resistance and ohmic behavior. With such materials it should be possible to harness the extraordinary diversity and specificity of protein functions to nanoscale electrical circuitry.

Cross-talk between estradiol receptor and EGFR/IGF-IR signaling pathways in estrogen-responsive breast cancers: focus on the role and impact of proteoglycans.

PubMed

Skandalis, Spyros S; Afratis, Nikolaos; Smirlaki, Gianna; Nikitovic, Dragana; Theocharis, Achilleas D; Tzanakakis, George N; Karamanos, Nikos K

2014-04-01

In hormone-dependent breast cancer, estrogen receptors are the principal signaling molecules that regulate several cell functions either by the genomic pathway acting directly as transcription factors in the nucleus or by the non-genomic pathway interacting with other receptors and their adjacent pathways like EGFR/IGFR. It is well established in literature that EGFR and IGFR signaling pathways promote cell proliferation and differentiation. Moreover, recent data indicate the cross-talk between ERs and EGFR/IGFR signaling pathways causing a transformation of cell functions as well as deregulation on normal expression pattern of matrix molecules. Specifically, proteoglycans, a major category of extracellular matrix (ECM) and cell surface macromolecules, are modified during malignancy and cause alterations in cancer cell signaling, affecting eventually functional cell properties such as proliferation, adhesion and migration. The on-going strategies to block only one of the above signaling effectors result cancer cells to overcome such inactivation using alternative signaling pathways. In this article, we therefore review the underlying mechanisms in respect to the role of ERs and the involvement of cross-talk between ERs, IGFR and EGFR in breast cancer cell properties and expression of extracellular secreted and cell bound proteoglycans involved in cancer progression. Understanding such signaling pathways may help to establish new potential pharmacological targets in terms of using ECM molecules to design novel anticancer therapies. © 2013. Published by Elsevier B.V. All rights reserved.

Single cell adhesion assay using computer controlled micropipette.

PubMed

Salánki, Rita; Hős, Csaba; Orgovan, Norbert; Péter, Beatrix; Sándor, Noémi; Bajtay, Zsuzsa; Erdei, Anna; Horvath, Robert; Szabó, Bálint

2014-01-01

Cell adhesion is a fundamental phenomenon vital for all multicellular organisms. Recognition of and adhesion to specific macromolecules is a crucial task of leukocytes to initiate the immune response. To gain statistically reliable information of cell adhesion, large numbers of cells should be measured. However, direct measurement of the adhesion force of single cells is still challenging and today's techniques typically have an extremely low throughput (5-10 cells per day). Here, we introduce a computer controlled micropipette mounted onto a normal inverted microscope for probing single cell interactions with specific macromolecules. We calculated the estimated hydrodynamic lifting force acting on target cells by the numerical simulation of the flow at the micropipette tip. The adhesion force of surface attached cells could be accurately probed by repeating the pick-up process with increasing vacuum applied in the pipette positioned above the cell under investigation. Using the introduced methodology hundreds of cells adhered to specific macromolecules were measured one by one in a relatively short period of time (∼30 min). We blocked nonspecific cell adhesion by the protein non-adhesive PLL-g-PEG polymer. We found that human primary monocytes are less adherent to fibrinogen than their in vitro differentiated descendants: macrophages and dendritic cells, the latter producing the highest average adhesion force. Validation of the here introduced method was achieved by the hydrostatic step-pressure micropipette manipulation technique. Additionally the result was reinforced in standard microfluidic shear stress channels. Nevertheless, automated micropipette gave higher sensitivity and less side-effect than the shear stress channel. Using our technique, the probed single cells can be easily picked up and further investigated by other techniques; a definite advantage of the computer controlled micropipette. Our experiments revealed the existence of a sub-population of strongly fibrinogen adherent cells appearing in macrophages and highly represented in dendritic cells, but not observed in monocytes.

Single Cell Adhesion Assay Using Computer Controlled Micropipette

PubMed Central

Salánki, Rita; Hős, Csaba; Orgovan, Norbert; Péter, Beatrix; Sándor, Noémi; Bajtay, Zsuzsa; Erdei, Anna; Horvath, Robert; Szabó, Bálint

2014-01-01

Cell adhesion is a fundamental phenomenon vital for all multicellular organisms. Recognition of and adhesion to specific macromolecules is a crucial task of leukocytes to initiate the immune response. To gain statistically reliable information of cell adhesion, large numbers of cells should be measured. However, direct measurement of the adhesion force of single cells is still challenging and today’s techniques typically have an extremely low throughput (5–10 cells per day). Here, we introduce a computer controlled micropipette mounted onto a normal inverted microscope for probing single cell interactions with specific macromolecules. We calculated the estimated hydrodynamic lifting force acting on target cells by the numerical simulation of the flow at the micropipette tip. The adhesion force of surface attached cells could be accurately probed by repeating the pick-up process with increasing vacuum applied in the pipette positioned above the cell under investigation. Using the introduced methodology hundreds of cells adhered to specific macromolecules were measured one by one in a relatively short period of time (∼30 min). We blocked nonspecific cell adhesion by the protein non-adhesive PLL-g-PEG polymer. We found that human primary monocytes are less adherent to fibrinogen than their in vitro differentiated descendants: macrophages and dendritic cells, the latter producing the highest average adhesion force. Validation of the here introduced method was achieved by the hydrostatic step-pressure micropipette manipulation technique. Additionally the result was reinforced in standard microfluidic shear stress channels. Nevertheless, automated micropipette gave higher sensitivity and less side-effect than the shear stress channel. Using our technique, the probed single cells can be easily picked up and further investigated by other techniques; a definite advantage of the computer controlled micropipette. Our experiments revealed the existence of a sub-population of strongly fibrinogen adherent cells appearing in macrophages and highly represented in dendritic cells, but not observed in monocytes. PMID:25343359

Surface-modified bacterial nanofibrillar PHB scaffolds for bladder tissue repair.

PubMed

Karahaliloğlu, Zeynep; Demirbilek, Murat; Şam, Mesut; Sağlam, Necdet; Mızrak, Alpay Koray; Denkbaş, Emir Baki

2016-01-01

The aim of the study is in vitro investigation of the feasibility of surface-modified bacterial nanofibrous poly [(R)-3-hydroxybutyrate] (PHB) graft for bladder reconstruction. In this study, the surface of electrospun bacterial PHB was modified with PEG- or EDA via radio frequency glow discharge method. After plasma modification, contact angle of EDA-modified PHB scaffolds decreased from 110 ± 1.50 to 23 ± 0.5 degree. Interestingly, less calcium oxalate stone deposition was observed on modified PHB scaffolds compared to that of non-modified group. Results of this study show that surface-modified scaffolds not only inhibited calcium oxalate growth but also enhanced the uroepithelial cell viability and proliferation.

Genetic mouse models of brain ageing and Alzheimer's disease.

PubMed

Bilkei-Gorzo, Andras

2014-05-01

Progression of brain ageing is influenced by a complex interaction of genetic and environmental factors. Analysis of genetically modified animals with uniform genetic backgrounds in a standardised, controlled environment enables the dissection of critical determinants of brain ageing on a molecular level. Human and animal studies suggest that increased load of damaged macromolecules, efficacy of DNA maintenance, mitochondrial activity, and cellular stress defences are critical determinants of brain ageing. Surprisingly, mouse lines with genetic impairment of anti-oxidative capacity generally did not show enhanced cognitive ageing but rather an increased sensitivity to oxidative challenge. Mouse lines with impaired mitochondrial activity had critically short life spans or severe and rapidly progressing neurodegeneration. Strains with impaired clearance in damaged macromolecules or defects in the regulation of cellular stress defences showed alterations in the onset and progression of cognitive decline. Importantly, reduced insulin/insulin-like growth factor signalling generally increased life span but impaired cognitive functions revealing a complex interaction between ageing of the brain and of the body. Brain ageing is accompanied by an increased risk of developing Alzheimer's disease. Transgenic mouse models expressing high levels of mutant human amyloid precursor protein showed a number of symptoms and pathophysiological processes typical for early phase of Alzheimer's disease. Generally, therapeutic strategies effective against Alzheimer's disease in humans were also active in the Tg2576, APP23, APP/PS1 and 5xFAD lines, but a large number of false positive findings were also reported. The 3xtg AD model likely has the highest face and construct validity but further studies are needed. Copyright © 2013 Elsevier Inc. All rights reserved.

GABA editing with macromolecule suppression using an improved MEGA-SPECIAL sequence.

PubMed

Gu, Meng; Hurd, Ralph; Noeske, Ralph; Baltusis, Laima; Hancock, Roeland; Sacchet, Matthew D; Gotlib, Ian H; Chin, Frederick T; Spielman, Daniel M

2018-01-01

The most common γ-aminobutyric-acid (GABA) editing approach, MEGA-PRESS, uses J-editing to measure GABA distinct from larger overlapping metabolites, but suffers contamination from coedited macromolecules (MMs) comprising 40 to 60% of the observed signal. MEGA-SPECIAL is an alternative method with better MM suppression, but is not widely used primarily because of its relatively poor spatial localization. Our goal was to develop an improved MM-suppressed GABA editing sequence at 3 Tesla. We modified a single-voxel MEGA-SPECIAL sequence with an oscillating readout gradient for improved spatial localization, and used very selective 30-ms editing pulses for improved suppression of coedited MMs. Simulation and in vivo experiments confirmed excellent MM suppression, insensitive to the range of B 0 frequency drifts typically encountered in vivo. Both intersubject and intrasubject studies showed that MMs, when suppressed by the improved MEGA-SPECIAL method, contributed approximately 40% to the corresponding MEGA-PRESS measurements. From the intersubject study, the coefficient of variation for GABA+/Cre (MEGA-PRESS) was 11.2% versus 7% for GABA/Cre (improved MEGA-SPECIAL), demonstrating significantly reduced variance (P = 0.005), likely coming from coedited MMs. This improved MEGA-SPECIAL sequence provides unbiased GABA measurements with reduced variance as compared with conventional MEGA-PRESS. This approach is also relatively insensitive to the range of B 0 drifts typically observed in in vivo human studies. Magn Reson Med 79:41-47, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Diffusion in Brain Extracellular Space

PubMed Central

Syková, Eva; Nicholson, Charles

2009-01-01

Diffusion in the extracellular space (ECS) of the brain is constrained by the volume fraction and the tortuosity and a modified diffusion equation represents the transport behavior of many molecules in the brain. Deviations from the equation reveal loss of molecules across the blood-brain barrier, through cellular uptake, binding or other mechanisms. Early diffusion measurements used radiolabeled sucrose and other tracers. Presently, the real-time iontophoresis (RTI) method is employed for small ions and the integrative optical imaging (IOI) method for fluorescent macromolecules, including dextrans or proteins. Theoretical models and simulations of the ECS have explored the influence of ECS geometry, effects of dead-space microdomains, extracellular matrix and interaction of macromolecules with ECS channels. Extensive experimental studies with the RTI method employing the cation tetramethylammonium (TMA) in normal brain tissue show that the volume fraction of the ECS typically is about 20% and the tortuosity about 1.6 (i.e. free diffusion coefficient of TMA is reduced by 2.6), although there are regional variations. These parameters change during development and aging. Diffusion properties have been characterized in several interventions, including brain stimulation, osmotic challenge and knockout of extracellular matrix components. Measurements have also been made during ischemia, in models of Alzheimer's and Parkinson's diseases and in human gliomas. Overall, these studies improve our conception of ECS structure and the roles of glia and extracellular matrix in modulating the ECS microenvironment. Knowledge of ECS diffusion properties are valuable in contexts ranging from understanding extrasynaptic volume transmission to the development of paradigms for drug delivery to the brain. PMID:18923183

Preferential adsorption of fluorescing fulvic and humic acid components on activated carbon using flow field-flow fractionation analysis.

PubMed

Schmit, Kathryn H; Wells, Martha J M

2002-02-01

Activated carbon treatment of drinking water is used to remove natural organic matter (NOM) precursors that lead to the formation of disinfection byproducts. The innate hydrophobic nature and macromolecular size of NOM render it amenable to sorption by activated carbon. Batch equilibrium and minicolumn breakthrough adsorption studies were performed using granular activated carbon to treat NOM-contaminated water. Ultraviolet (UV) absorption spectroscopy and flow field-flow fractionation analysis using tandem diode-array and fluorescence detectors were used to monitor the activated carbon sorption of NOM. Using these techniques, it was possible to study activated carbon adsorption properties of UV absorbing, fluorescing and nonfluorescing, polyelectrolytic macromolecules fractionated from the total macromolecular and nonmacromolecular composition of NOM. Adsorption isotherms were constructed at pH 6 and pH 9. Data were described by the traditional and modified Freundlich models. Activated carbon capacity and adsorbability were compared among fractionated molecular subsets of fulvic and humic acids. Preferential adsorption (or adsorptive fractionation) of polyelectrolytic, fluorescing fulvic and humic macromolecules on activated carbon was observed. The significance of observing preferential adsorption on activated carbon of fluorescing macromolecular components relative to nonfluorescing components is that this phenomenon changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the composition that existed in the aqueous phase prior to adsorption. Likewise, it changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the adsorbed phase. This research increases our understanding of NOM interactions with activated carbon which may lead to improved methods of potable water production.

tRNA-modifying MiaE protein from Salmonella typhimurium is a nonheme diiron monooxygenase

PubMed Central

Mathevon, Carole; Pierrel, Fabien; Oddou, Jean-Louis; Garcia-Serres, Ricardo; Blondin, Geneviève; Latour, Jean-Marc; Ménage, Stéphane; Gambarelli, Serge; Fontecave, Marc; Atta, Mohamed

2007-01-01

MiaE catalyzes the posttranscriptional allylic hydroxylation of 2-methylthio-N-6-isopentenyl adenosine in tRNAs. The Salmonella typhimurium enzyme was heterologously expressed in Escherichia coli. The purified enzyme is a monomer with two iron atoms and displays activity in in vitro assays. The type and properties of the iron center were investigated by using a combination of UV-visible absorption, EPR, HYSCORE, and Mössbauer spectroscopies which demonstrated that the MiaE enzyme contains a nonheme dinuclear iron cluster, similar to that found in the hydroxylase component of methane monooxygenase. This is the first example of an enzyme from this important class of diiron monooxygenases to be involved in the hydroxylation of a biological macromolecule and the second example of a redox metalloenzyme participating in tRNA modification. PMID:17679698

The application of polysaccharide-based nanogels in peptides/proteins and anticancer drugs delivery.

PubMed

Zhang, Lin; Pan, Jifei; Dong, Shibo; Li, Zhaoming

2017-09-01

Finding adequate carriers for proteins/peptides and anticancer drugs delivery has become an urgent need, owing to the growing number of therapeutic macromolecules and the increasing amount of cancer incidence. Polysaccharide-based nanogels have attracted interest as carriers for proteins/peptides and anticancer drugs because of their characteristic properties like biodegradability, biocompatibility, stimuli-responsive behaviour, softness and swelling to help achieve a controlled, triggered response at the target site. In addition, the groups of the polysaccharide backbone are able to be modified to develop functional nanogels. Some polysaccharides have the intrinsic ability to recognise specific cell types, allowing the design of targeted drug delivery systems through receptor-mediated endocytosis. This review is aimed at describing and exploring the potential of polysaccharides that are used in nanogels which can help to deliver proteins/peptides and anticancer drugs.

Comparison of gold nanoparticle mediated photoporation: vapor nanobubbles outperform direct heating for delivering macromolecules in live cells.

PubMed

Xiong, Ranhua; Raemdonck, Koen; Peynshaert, Karen; Lentacker, Ine; De Cock, Ine; Demeester, Jo; De Smedt, Stefaan C; Skirtach, Andre G; Braeckmans, Kevin

2014-06-24

There is a great interest in delivering macromolecular agents into living cells for therapeutic purposes, such as siRNA for gene silencing. Although substantial effort has gone into designing nonviral nanocarriers for delivering macromolecules into cells, translocation of the therapeutic molecules from the endosomes after endocytosis into the cytoplasm remains a major bottleneck. Laser-induced photoporation, especially in combination with gold nanoparticles, is an alternative physical method that is receiving increasing attention for delivering macromolecules in cells. By allowing gold nanoparticles to bind to the cell membrane, nanosized membrane pores can be created upon pulsed laser illumination. Depending on the laser energy, pores are created through either direct heating of the AuNPs or by vapor nanobubbles (VNBs) that can emerge around the AuNPs. Macromolecules in the surrounding cell medium can then diffuse through the pores directly into the cytoplasm. Here we present a systematic evaluation of both photoporation mechanisms in terms of cytotoxicity, cell loading, and siRNA transfection efficiency. We find that the delivery of macromolecules under conditions of VNBs is much more efficient than direct photothermal disturbance of the plasma membrane without any noticeable cytotoxic effect. Interestingly, by tuning the laser energy, the pore size could be changed, allowing control of the amount and size of molecules that are delivered in the cytoplasm. As only a single nanosecond laser pulse is required, we conclude that VNBs are an interesting photoporation mechanism that may prove very useful for efficient high-throughput macromolecular delivery in live cells.

Macromolecular Competition Titration Method: Accessing Thermodynamics of the Unmodified Macromolecule–Ligand Interactions Through Spectroscopic Titrations of Fluorescent Analogs

PubMed Central

Bujalowski, Wlodzimierz; Jezewska, Maria J.

2011-01-01

Analysis of thermodynamically rigorous binding isotherms provides fundamental information about the energetics of the ligand–macromolecule interactions and often an invaluable insight about the structure of the formed complexes. The Macromolecular Competition Titration (MCT) method enables one to quantitatively obtain interaction parameters of protein–nucleic acid interactions, which may not be available by other methods, particularly for the unmodified long polymer lattices and specific nucleic acid substrates, if the binding is not accompanied by adequate spectroscopic signal changes. The method can be applied using different fluorescent nucleic acids or fluorophores, although the etheno-derivatives of nucleic acid are especially suitable as they are relatively easy to prepare, have significant blue fluorescence, their excitation band lies far from the protein absorption spectrum, and the modification eliminates the possibility of base pairing with other nucleic acids. The MCT method is not limited to the specific size of the reference nucleic acid. Particularly, a simple analysis of the competition titration experiments is described in which the fluorescent, short fragment of nucleic acid, spanning the exact site-size of the protein–nucleic acid complex, and binding with only a 1:1 stoichiometry to the protein, is used as a reference macromolecule. Although the MCT method is predominantly discussed as applied to studying protein–nucleic acid interactions, it can generally be applied to any ligand–macromolecule system by monitoring the association reaction using the spectroscopic signal originating from the reference macromolecule in the presence of the competing macromolecule, whose interaction parameters with the ligand are to be determined. PMID:21195223

Nanoparticles modified with multiple organic acids

NASA Technical Reports Server (NTRS)

Luebben, Silvia DeVito (Inventor); Cook, Ronald Lee (Inventor); Wilson, Carolina (Inventor); Meiser, Manfred (Inventor); Myers, Andrew William (Inventor); Smith, Bryan Matthew (Inventor); Elliott, Brian John (Inventor); Kreutzer, Cory (Inventor)

2007-01-01

Surface-modified nanoparticles of boehmite, and methods for preparing the same. Aluminum oxyhydroxide nanoparticles are surface modified by reaction with selected amounts of organic acids. In particular, the nanoparticle surface is modified by reactions with two or more different carboxylic acids, at least one of which is an organic carboxylic acid. The product is a surface modified boehmite nanoparticle that has an inorganic aluminum oxyhydroxide core, or part aluminum oxyhydroxide core and a surface-bonded organic shell. Organic carboxylic acids of this invention contain at least one carboxylic acid group and one carbon-hydrogen bond. One embodiment of this invention provides boehmite nanoparticles that have been surface modified with two or more acids one of which additional carries at least one reactive functional group. Another embodiment of this invention provides boehmite nanoparticles that have been surface modified with multiple acids one of which has molecular weight or average molecular weight greater than or equal to 500 Daltons. Yet, another embodiment of this invention provides boehmite nanoparticles that are surface modified with two or more acids one of which is hydrophobic in nature and has solubility in water of less than 15 by weight. The products of the methods of this invention have specific useful properties when used in mixture with liquids, as filler in solids, or as stand-alone entities.

Nanoparticles modified with multiple organic acids

DOEpatents

Cook, Ronald Lee [Lakewood, CO; Luebben, Silvia DeVito [Golden, CO; Myers, Andrew William [Arvada, CO; Smith, Bryan Matthew [Boulder, CO; Elliott, Brian John [Superior, CO; Kreutzer, Cory [Brighton, CO; Wilson, Carolina [Arvada, CO; Meiser, Manfred [Aurora, CO

2007-07-17

Surface-modified nanoparticles of boehmite, and methods for preparing the same. Aluminum oxyhydroxide nanoparticles are surface modified by reaction with selected amounts of organic acids. In particular, the nanoparticle surface is modified by reactions with two or more different carboxylic acids, at least one of which is an organic carboxylic acid. The product is a surface modified boehmite nanoparticle that has an inorganic aluminum oxyhydroxide core, or part aluminum oxyhydroxide core and a surface-bonded organic shell. Organic carboxylic acids of this invention contain at least one carboxylic acid group and one carbon-hydrogen bond. One embodiment of this invention provides boehmite nanoparticles that have been surface modified with two or more acids one of which additional carries at least one reactive functional group. Another embodiment of this invention provides boehmite nanoparticles that have been surface modified with multiple acids one of which has molecular weight or average molecular weight greater than or equal to 500 Daltons. Yet, another embodiment of this invention provides boehmite nanoparticles that are surface modified with two or more acids one of which is hydrophobic in nature and has solubility in water of less than 15 by weight. The products of the methods of this invention have specific useful properties when used in mixture with liquids, as filler in solids, or as stand-alone entities.

Antibacterial effect of silver nanofilm modified stainless steel surface

NASA Astrophysics Data System (ADS)

Fang, F.; Kennedy, J.; Dhillon, M.; Flint, S.

2015-03-01

Bacteria can attach to stainless steel surfaces, resulting in the colonization of the surface known as biofilms. The release of bacteria from biofilms can cause contamination of food such as dairy products in manufacturing plants. This study aimed to modify stainless steel surfaces with silver nanofilms and to examine the antibacterial effectiveness of the modified surface. Ion implantation was applied to produce silver nanofilms on stainless steel surfaces. 35 keV Ag ions were implanted with various fluences of 1 × 1015 to 1 × 1017 ions•cm-2 at room temperature. Representative atomic force microscopy characterizations of the modified stainless steel are presented. Rutherford backscattering spectrometry spectra revealed the implanted atoms were located in the near-surface region. Both unmodified and modified stainless steel coupons were then exposed to two types of bacteria, Pseudomonas fluorescens and Streptococcus thermophilus, to determine the effect of the surface modification on bacterial attachment and biofilm development. The silver modified coupon surface fluoresced red over most of the surface area implying that most bacteria on coupon surface were dead. This study indicates that the silver nanofilm fabricated by the ion implantation method is a promising way of reducing the attachment of bacteria and delay biofilm formation.

[Dynamics of biomacromolecules in coherent electromagnetic radiation field].

PubMed

Leshcheniuk, N S; Apanasevich, E E; Tereshenkov, V I

2014-01-01

It is shown that induced oscillations and periodic displacements of the equilibrium positions occur in biomacromolecules in the absence of electromagnetic radiation absorption, due to modulation of interaction potential between atoms and groups of atoms forming the non-valence bonds in macromolecules by the external electromagnetic field. Such "hyperoscillation" state causes inevitably the changes in biochemical properties of macromolecules and conformational transformation times.

Solid-State 15N NMR of 15N-Labeled Nylon 6 and Nylon 11

DTIC Science & Technology

1990-05-22

S. Veeman, E. M. Menger, W. Ritchey, and E. de Boer, Macromolecules, 1979, 12, 924. 2. A. N. Garroway , W. M. Ritchey and W. B. Moniz, Macromolecules...S. Veeman and E. M. Menger, Bull. Magn. Reson., 1980, 2, 77. 26. D. L. VanderHart and A. N. Garroway , J. Chem. Phys., 1979, 71, 2773. 27. M. D

Formation and characterization of calcium orthophosphates in the presence of two different acidic macromolecules

NASA Astrophysics Data System (ADS)

Pelin, Irina M.; Maier, Vasilica; Suflet, Dana M.; Popescu, Irina; Darie-Nita, Raluca N.; Aflori, Magdalena; Butnaru, Maria

2017-10-01

The synthetic nanocrystalline calcium orthophosphates have a notable bioactivity due to the chemical similarity with biological apatite from calcified tissues. In mineralized tissues, the highly ordered structures come from organized assemblies of biomacromolecules and inorganic nanoparticles. One of the purposes of this work was to study the effect of two types of acidic macromolecules: atelocollagen and phosphorylated curdlan onto calcium orthophosphates formation after 30 days of maturation at 2 ± 2 °C. The resulted samples after a long aging time, either calcium orthophosphates or composites, were first investigated by FT-IR spectroscopy and X-ray diffractometry and the results indicated that precipitated hydroxyapatite with low crystallinity was obtained when the synthesis was performed in the presence of phosphorylated curdlan. The macromolecules influenced the morphology of the particles as shown by scanning and transmission electron microscopy. The presence of macromolecules as demonstrated by thermal investigation also influenced the rheological properties of the samples. The second purpose of the work was to evaluate the cytotoxicity of the samples using the MTT assay, and the results revealed very good cells viability. The preliminary results are encouraging regarding the use of these materials for further tests in order to develop injectable bone substitutes.

A Strontium-Modified Titanium Surface Produced by a New Method and Its Biocompatibility In Vitro

PubMed Central

Liu, Chundong; Zhang, Yanli; Wang, Lichao; Zhang, Xinhua; Chen, Qiuyue; Wu, Buling

2015-01-01

Objective To present a new and effective method of producing titanium surfaces modified with strontium and to investigate the surface characteristics and in vitro biocompatibility of titanium (Ti) surfaces modified with strontium (Sr) for bone implant applications. Materials and Methods Sr-modified Ti surfaces were produced by sequential treatments with NaOH, strontium acetate, heat and water. The surface characteristics and the concentration of the Sr ions released from the samples were examined. Cell adhesion, morphology and growth were investigated using osteoblasts isolated from the calvaria of neonatal Sprague-Dawley rats. Expression of osteogenesis-related genes and proteins was examined to assess the effect of the Sr-modified Ti surfaces on osteoblasts. Results The modified titanium surface had a mesh structure with significantly greater porosity, and approximately5.37±0.35at.% of Sr was incorporated into the surface. The hydrophilicity was enhanced by the incorporation of Sr ions and water treatment. The average amounts of Sr released from the Sr-modified plates subjected to water treatment were slight higher than the plates without water treatment. Sr promoted cellular adhesion, spreading and growth compared with untreated Ti surfaces. The Sr-modified Ti plates also promoted expression of osteogenesis-related genes,and expression of OPN and COL-І by osteoblasts. Ti plates heat treated at 700°C showed increased bioactivity in comparison with those treated at 600°C. Water treatment upregulated the expression of osteogenesis-related genes. Conclusions These results show that Sr-modification of Ti surfaces may improve bioactivity in vitro. Water treatment has enhanced the response of osteoblasts. The Sr-modified Ti heat-treated at 700°C exhibited better bioactivity compared with that heated at 600°C. PMID:26529234

A Strontium-Modified Titanium Surface Produced by a New Method and Its Biocompatibility In Vitro.

PubMed

Liu, Chundong; Zhang, Yanli; Wang, Lichao; Zhang, Xinhua; Chen, Qiuyue; Wu, Buling

2015-01-01

To present a new and effective method of producing titanium surfaces modified with strontium and to investigate the surface characteristics and in vitro biocompatibility of titanium (Ti) surfaces modified with strontium (Sr) for bone implant applications. Sr-modified Ti surfaces were produced by sequential treatments with NaOH, strontium acetate, heat and water. The surface characteristics and the concentration of the Sr ions released from the samples were examined. Cell adhesion, morphology and growth were investigated using osteoblasts isolated from the calvaria of neonatal Sprague-Dawley rats. Expression of osteogenesis-related genes and proteins was examined to assess the effect of the Sr-modified Ti surfaces on osteoblasts. The modified titanium surface had a mesh structure with significantly greater porosity, and approximately5.37±0.35at.% of Sr was incorporated into the surface. The hydrophilicity was enhanced by the incorporation of Sr ions and water treatment. The average amounts of Sr released from the Sr-modified plates subjected to water treatment were slight higher than the plates without water treatment. Sr promoted cellular adhesion, spreading and growth compared with untreated Ti surfaces. The Sr-modified Ti plates also promoted expression of osteogenesis-related genes,and expression of OPN and COL-І by osteoblasts. Ti plates heat treated at 700°C showed increased bioactivity in comparison with those treated at 600°C. Water treatment upregulated the expression of osteogenesis-related genes. These results show that Sr-modification of Ti surfaces may improve bioactivity in vitro. Water treatment has enhanced the response of osteoblasts. The Sr-modified Ti heat-treated at 700°C exhibited better bioactivity compared with that heated at 600°C.

Multilayer Choline Phosphate Molecule Modified Surface with Enhanced Cell Adhesion but Resistance to Protein Adsorption.

PubMed

Chen, Xingyu; Yang, Ming; Liu, Botao; Li, Zhiqiang; Tan, Hong; Li, Jianshu

2017-08-22

Choline phosphate (CP), which is a new zwitterionic molecule, and has the reverse order of phosphate choline (PC) and could bind to the cell membrane though the unique CP-PC interaction. Here we modified a glass surface with multilayer CP molecules using surface-initiated atom-transfer radical polymerization (SI-ATRP) and the ring-opening method. Polymeric brushes of (dimethylamino)ethyl methacrylate (DMAEMA) were synthesized by SI-ATRP from the glass surface. Then the grafted PDMAEMA brushes were used to introduce CP groups to fabricate the multilayer CP molecule modified surface. The protein adsorption experiment and cell culture test were used to evaluate the biocompatibility of the modified surfaces by using human umbilical veinendothelial cells (HUVECs). The protein adsorption results demonstrated that the multilayer CP molecule decorated surface could prevent the adsorption of fibrinogen and serum protein. The adhesion and proliferation of cells were improved significantly on the multilayer CP molecule modified surface. Therefore, the biocompatibility of the material surface could be improved by the modified multilayer CP molecule, which exhibits great potential for biomedical applications, e.g., scaffolds in tissue engineering.

Modified Surface Having Low Adhesion Properties to Mitigate Insect Residue Adhesion

NASA Technical Reports Server (NTRS)

Wohl, Christopher J., Jr. (Inventor); Smith, Joseph G., Jr. (Inventor); Siochi, Emilie J. (Inventor); Penner, Ronald K. (Inventor)

2016-01-01

A process to modify a surface to provide reduced adhesion surface properties to mitigate insect residue adhesion. The surface may include the surface of an article including an aircraft, an automobile, a marine vessel, all-terrain vehicle, wind turbine, helmet, etc. The process includes topographically and chemically modifying the surface by applying a coating comprising a particulate matter, or by applying a coating and also topographically modifying the surface by various methods, including but not limited to, lithographic patterning, laser ablation and chemical etching, physical vapor phase deposition, chemical vapor phase deposition, crystal growth, electrochemical deposition, spin casting, and film casting.

Study on Surface Roughness of Modified Silicon Carbide Mirrors polished by Magnetorheological Finishing

NASA Astrophysics Data System (ADS)

Du, Hang; Song, Ci; Li, Shengyi

2018-01-01

In order to obtain high precision and high surface quality silicon carbide mirrors, the silicon carbide mirror substrate is subjected to surface modification treatment. In this paper, the problem of Silicon Carbide (SiC) mirror surface roughness deterioration by MRF is studied. The reasons of surface flaws of “Comet tail” are analyzed. Influence principle of MRF polishing depth and the surface roughness of modified SiC mirrors is obtained by experiments. On this basis, the united process of modified SiC mirrors is proposed which is combined MRF with the small grinding head CCOS. The united process makes improvement in the surface accuracy and surface roughness of modified SiC mirrors.

Investigation of Water Dissociation and Surface Hydroxyl Stability on Pure and Ni-Modified CoOOH by Ambient Pressure Photoelectron Spectroscopy

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

Chen, Zhu; Kronawitter, Coleman X.; Waluyo, Iradwikanari

Water adsorption and reaction on pure and Ni-modified CoOOH nanowires were investigated using ambient pressure photoemission spectroscopy (APPES). The unique capabilities of APPES enable us to observe water dissociation and monitor formation of surface species on pure and Ni-modified CoOOH under elevated pressures and temperatures for the first time. Over a large range of pressures (UHV to 1 Torr), water dissociates readily on the pure and Ni-modified CoOOH surfaces at 27 °C. With an increase in H 2O pressure, a greater degree of surface hydroxylation was observed for all samples. At 1 Torr H 2O, ratios of different oxygen speciesmore » indicate a transformation of CoOOH to CoO xH y in pure and Ni-modified CoOOH. In temperature dependent studies, desorption of weakly bound water and surface dehydroxylation were observed with increasing temperature. In conclusion, larger percentages of surface hydroxyl groups at higher temperatures were observed on Ni-modified CoOOH compared to pure CoOOH, which indicates an increased stability of surface hydroxyl groups on these Ni-modified surfaces.« less

Investigation of Water Dissociation and Surface Hydroxyl Stability on Pure and Ni-Modified CoOOH by Ambient Pressure Photoelectron Spectroscopy

DOE PAGES

Chen, Zhu; Kronawitter, Coleman X.; Waluyo, Iradwikanari; ...

2017-09-07

Water adsorption and reaction on pure and Ni-modified CoOOH nanowires were investigated using ambient pressure photoemission spectroscopy (APPES). The unique capabilities of APPES enable us to observe water dissociation and monitor formation of surface species on pure and Ni-modified CoOOH under elevated pressures and temperatures for the first time. Over a large range of pressures (UHV to 1 Torr), water dissociates readily on the pure and Ni-modified CoOOH surfaces at 27 °C. With an increase in H 2O pressure, a greater degree of surface hydroxylation was observed for all samples. At 1 Torr H 2O, ratios of different oxygen speciesmore » indicate a transformation of CoOOH to CoO xH y in pure and Ni-modified CoOOH. In temperature dependent studies, desorption of weakly bound water and surface dehydroxylation were observed with increasing temperature. In conclusion, larger percentages of surface hydroxyl groups at higher temperatures were observed on Ni-modified CoOOH compared to pure CoOOH, which indicates an increased stability of surface hydroxyl groups on these Ni-modified surfaces.« less

Recent advances in jointed quantum mechanics and molecular mechanics calculations of biological macromolecules: schemes and applications coupled to ab initio calculations.

PubMed

Hagiwara, Yohsuke; Tateno, Masaru

2010-10-20

We review the recent research on the functional mechanisms of biological macromolecules using theoretical methodologies coupled to ab initio quantum mechanical (QM) treatments of reaction centers in proteins and nucleic acids. Since in most cases such biological molecules are large, the computational costs of performing ab initio calculations for the entire structures are prohibitive. Instead, simulations that are jointed with molecular mechanics (MM) calculations are crucial to evaluate the long-range electrostatic interactions, which significantly affect the electronic structures of biological macromolecules. Thus, we focus our attention on the methodologies/schemes and applications of jointed QM/MM calculations, and discuss the critical issues to be elucidated in biological macromolecular systems. © 2010 IOP Publishing Ltd

Materials based on cellulose fabric and PVC with porous structures formed by jointed aza- and oxa-aza-crown macromolecules

NASA Astrophysics Data System (ADS)

Fridman, A. Ya.; Tsivadze, A. Yu.; Morozova, E. M.; Sokolova, N. P.; Shiryaev, A. A.; Petukhova, G. A.; Voloshchuk, A. M.; Bardyshev, I. I.; Gorbunov, A. M.; Polyakova, I. Ya.; Novikov, A. K.; Titova, V. N.; Yavich, A. A.; Petrova, N. V.

2016-12-01

A material with porous structures formed by jointed aza- and oxa-aza-crowns with peripheral OHgroups is synthesized on the basis of cellulose fabric and PVC transformed into hydroxyethylcyclam. Mesopores are mainly observed on the fiber surface. The specific surface of the material is 6 m2/g; the volume of free space is 0.112 cm3/g. Assuming the internal pores have a disk-like shape, their width is estimated at 2 nm. The material sorbs vapors of aliphatic and aromatic hydrocarbons, alcohols, aldehydes, ketones, amines, amides, nitriles, and sulfoxides. It also swells to a limited degree in organic solvents. When sulfuric acid or sodium hydroxide is sorbed in the pores, compounds of them with H+- and OH--conducting systems of hydrogen bonds are formed.

Monitoring the degrafting of polyelectrolyte brushes by using surface gradients

NASA Astrophysics Data System (ADS)

Ko, Yeongun; Genzer, Jan

Polymer brushes comprise densely grafted polymer chains on surfaces, which possess high stability and high concentration of reactive centers per unit area compared to physisorbed polymer film. Polymer brushes are employed in many applications, including anti-fouling surfaces, cell adhesive surfaces, responsive surfaces, low-friction surfaces, etc. Recently, researchers reported that charged (or chargeable) polymer brushes can be degrafted from substrate while incubated in buffer solutions. Based on previous experiments conducted in our group and by others, we assume that chain degrafting results from the hydrolysis of Si-O groups in head-group of the initiator and/or the ester groups in main body of the initiator. The kinetic of hydrolysis is affected by mechanical forces acting on the initiator. Those forces depend on the molecular weight and the grafting density of the brush, and the concentration and distribution of charges along the macromolecule (tuned by pH - for weak electrolytes - and concentration of external salt). In this work, we study the stability of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) brushes in two solvents (ethanol and water) at various pH values in water and under different levels of external salt concentration. National Science Foundation.

Estimation of Nanodiamond Surface Charge Density from Zeta Potential and Molecular Dynamics Simulations.

PubMed

Ge, Zhenpeng; Wang, Yi

2017-04-20

Molecular dynamics simulations of nanoparticles (NPs) are increasingly used to study their interactions with various biological macromolecules. Such simulations generally require detailed knowledge of the surface composition of the NP under investigation. Even for some well-characterized nanoparticles, however, this knowledge is not always available. An example is nanodiamond, a nanoscale diamond particle with surface dominated by oxygen-containing functional groups. In this work, we explore using the harmonic restraint method developed by Venable et al., to estimate the surface charge density (σ) of nanodiamonds. Based on the Gouy-Chapman theory, we convert the experimentally determined zeta potential of a nanodiamond to an effective charge density (σ eff ), and then use the latter to estimate σ via molecular dynamics simulations. Through scanning a series of nanodiamond models, we show that the above method provides a straightforward protocol to determine the surface charge density of relatively large (> ∼100 nm) NPs. Overall, our results suggest that despite certain limitation, the above protocol can be readily employed to guide the model construction for MD simulations, which is particularly useful when only limited experimental information on the NP surface composition is available to a modeler.

Investigation of the antibiofilm capacity of peptide-modified stainless steel

PubMed Central

Cao, Pan; Li, Wen-Wu; Morris, Andrew R.; Horrocks, Paul D.; Yuan, Cheng-Qing

2018-01-01

Biofilm formation on surfaces is an important research topic in ship tribology and medical implants. In this study, dopamine and two types of synthetic peptides were designed and attached to 304 stainless steel surfaces, aiming to inhibit the formation of biofilms. A combinatory surface modification procedure was applied in which dopamine was used as a coupling agent, allowing a strong binding ability with the two peptides. X-ray photoelectron spectroscopy (XPS), elemental analysis, contact angle measurement and surface roughness test were used to evaluate the efficiency of the peptide modification. An antibiofilm assay against Staphylococcus aureus was conducted to validate the antibiofilm capacity of the peptide-modified stainless steel samples. XPS analysis confirmed that the optimal dopamine concentration was 40 µg ml−1 in the coupling reaction. Element analysis showed that dopamine and the peptides had bound to the steel surfaces. The robustness assay of the modified surface demonstrated that most peptide molecules had bound on the surface of the stainless steel firmly. The contact angle of the modified surfaces was significantly changed. Modified steel samples exhibited improved antibiofilm properties in comparison to untreated and dopamine-only counterpart, with the peptide 1 modification displaying the best antibiofilm effect. The modified surfaces showed antibacterial capacity. The antibiofilm capacity of the modified surfaces was also surface topography sensitive. The steel sample surfaces polished with 600# sandpaper exhibited stronger antibiofilm capacity than those polished with other types of sandpapers after peptide modification. These findings present valuable information for future antifouling material research. PMID:29657809

Investigation of the antibiofilm capacity of peptide-modified stainless steel.

PubMed

Cao, Pan; Li, Wen-Wu; Morris, Andrew R; Horrocks, Paul D; Yuan, Cheng-Qing; Yang, Ying

2018-03-01

Biofilm formation on surfaces is an important research topic in ship tribology and medical implants. In this study, dopamine and two types of synthetic peptides were designed and attached to 304 stainless steel surfaces, aiming to inhibit the formation of biofilms. A combinatory surface modification procedure was applied in which dopamine was used as a coupling agent, allowing a strong binding ability with the two peptides. X-ray photoelectron spectroscopy (XPS), elemental analysis, contact angle measurement and surface roughness test were used to evaluate the efficiency of the peptide modification. An antibiofilm assay against Staphylococcus aureus was conducted to validate the antibiofilm capacity of the peptide-modified stainless steel samples. XPS analysis confirmed that the optimal dopamine concentration was 40 µg ml -1 in the coupling reaction. Element analysis showed that dopamine and the peptides had bound to the steel surfaces. The robustness assay of the modified surface demonstrated that most peptide molecules had bound on the surface of the stainless steel firmly. The contact angle of the modified surfaces was significantly changed. Modified steel samples exhibited improved antibiofilm properties in comparison to untreated and dopamine-only counterpart, with the peptide 1 modification displaying the best antibiofilm effect. The modified surfaces showed antibacterial capacity. The antibiofilm capacity of the modified surfaces was also surface topography sensitive. The steel sample surfaces polished with 600# sandpaper exhibited stronger antibiofilm capacity than those polished with other types of sandpapers after peptide modification. These findings present valuable information for future antifouling material research.

Surface chemistry of a hydrogenated mesoporous p-type silicon

NASA Astrophysics Data System (ADS)

Media, El-Mahdi; Outemzabet, Ratiba

2017-02-01

The finality of this work is devoted to the grafting of organic molecules on hydrogen passivated mesoporous silicon surfaces. The study would aid in the development for the formation of organic monolayers on silicon surface to be exploited for different applications such as the realisation of biosensors and medical devices. The basic material is silicon which has been first investigated by FTIR at atomistic plane during the anodic forward and backward polarization (i.e. "go" and "return"). For this study, we applied a numerical program based on least squares method to infrared absorbance spectra obtained by an in situ attenuated total reflection on p-type silicon in diluted HF electrolyte. Our numerical treatment is based on the fitting of the different bands of IR absorbance into Gaussians corresponding to the different modes of vibration of molecular groups such as siloxanes and hydrides. An adjustment of these absorbance bands is done systematically. The areas under the fitted bands permit one to follow the intensity of the different modes of vibration that exist during the anodic forward and backward polarization in order to compare the reversibility of the phenomenon of the anodic dissolution of silicon. It permits also to follow the evolution between the hydrogen silicon termination at forward and backward scanning applied potential. Finally a comparison between the states of the initial and final surface was carried out. We confirm the presence of clearly four and three distinct vibration modes of siloxanes/hydroxide, SiOx, and hydrides, SiHx, respectively. The results show clearly that the adsorbed species found in the final stage after an electrochemical treatment consist of surface hydrogen and they show also that the surface morphology is different compared to the starting one, which is considered as reference. It is clear that the H-terminated of porous silicon surface is hydrophobic in nature. The hydrophobic character of this surface makes difficult the grafting of a probe which serves to get other molecules; where from the necessity of the presence of a hydrophilic surface on the porous silicon surface. This will facilitate the penetration and the grafting of the molecules probes. So to improve the penetration and the grafting of the organic molecules or the immobilization of the probes on the hydrogenated mesoporous silicon surfaces under wet chemical conditions an intermediate step is required. In this second study, we use the following procedure. After the porosification of the silicon by electrochemical anodisation, the porous SiH layer returns a hydrophobic surface. This stage is a starting point of multistep scheme for the surface modification. The next step is the thermal hydrosilylation in order to have an acidic surface. The acidic surface was then modified by the chains of Poly(ethylene glycol) (PEG) which is a highly investigated polymer for the covalent modification of biological macromolecules and surfaces. The grafting of PEG returns a hydrophilic surface confirmed by the IR results.

Method for detecting and diagnosing disease caused by pathological protein aggregation

DOEpatents

Stevens, Fred J.; Myatt, Elizabeth A.; Solomon, Alan

2000-01-01

A method is provided for detecting pathological macromolecules in a patient, comprising obtaining body fluid from the patient, pretreating the body fluid, subjecting the pretreated body fluid to size-exclusion chromatography to create an excluded fluid, and analyzing the excluded fluid to detect macromolecules having a predetermined molecular weight. The method also allows for comparing elution spectra with reference spectra of suspect pathologic proteins.

A Versatile Technique for the In Vivo Imaging of Human Tumor Xenografts Using Near-Infrared Fluorochrome-Conjugated Macromolecule Probes

PubMed Central

Suemizu, Hiroshi; Kawai, Kenji; Higuchi, Yuichiro; Hashimoto, Haruo; Ogura, Tomoyuki; Itoh, Toshio; Sasaki, Erika; Nakamura, Masato

2013-01-01

Here, we present a versatile method for detecting human tumor xenografts in vivo, based on the enhanced permeability and retention (EPR) effect, using near-infrared (NIR) fluorochrome-conjugated macromolecule probes. Bovine serum albumin (BSA) and two immunoglobulins—an anti-human leukocyte antigen (HLA) monoclonal antibody and isotype control IgG2a—were labeled with XenoLight CF770 fluorochrome and used as NIR-conjugated macromolecule probes to study whole-body imaging in a variety of xenotransplantation mouse models. NIR fluorescent signals were observed in subcutaneously transplanted BxPC-3 (human pancreatic cancer) cells and HCT 116 (colorectal cancer) cells within 24 h of NIR-macromolecule probe injection, but the signal from the fluorochrome itself or from the NIR-conjugated small molecule (glycine) injection was not observed. The accuracy of tumor targeting was confirmed by the localization of the NIR-conjugated immunoglobulin within the T-HCT 116 xenograft (in which the orange-red fluorescent protein tdTomato was stably expressed by HCT 116 cells) in the subcutaneous transplantation model. However, there was no significant difference in the NIR signal intensity of the region of interest between the anti-HLA antibody group and the isotype control group in the subcutaneous transplantation model. Therefore, the antibody accumulation within the tumor in vivo is based on the EPR effect. The liver metastasis generated by an intrasplenic injection of T-HCT 116 cells was clearly visualized by the NIR-conjugated anti-HLA probe but not by the orange-red fluorescent signal derived from the tdTomato reporter. This result demonstrated the superiority of the NIR probes over the tdTomato reporter protein at enhancing tissue penetration. In another xenograft model, patient-derived xenografts (PDX) of LC11-JCK (human non-small cell lung cancer) were successfully visualized using the NIR-conjugated macromolecule probe without any genetic modification. These results suggested that NIR-conjugated macromolecule, preferably, anti-HLA antibody probe is a valuable tool for the detection of human tumors in experimental metastasis models using whole-body imaging. PMID:24358218

A Robust Biomarker

NASA Technical Reports Server (NTRS)

Westall, F.; Steele, A.; Toporski, J.; Walsh, M. M.; Allen, C. C.; Guidry, S.; McKay, D. S.; Gibson, E. K.; Chafetz, H. S.

2000-01-01

Polymers of bacterial origin, either through cell secretion or the degraded product of cell lysis, form isolated mucoidal strands as well as well-developed biofilms on interfaces. Biofilms are structurally and compositionally complex and are readily distinguishable from abiogenic films. These structures range in size from micrometers to decimeters, the latter occurring as the well-known, mineralised biofilms called stromatolites. Compositionally bacterial polymers are greater than 90 % water, with while the majority of the macromolecules forming the framework of the polymers consisting of polysaccharides (with and some nucteic acids and proteins). These macromolecules contain a vaste amount of functional groups, such as carboxyls, hydroxyls, and phosphoryls which are implicated in cation-binding. It is the elevated metal- binding capacity which provides the bacterial polymer with structural support and also helps to preserves it for up to 3.5 b.y. in the terrestrial rock record. The macromolecules, thus, can become rapidly mineralised and trapped in a mineral matrix. Through early and late diagenesis (bacterial degradation, burial, heat, pressure and time) they break down, losing the functional groups and, gradually, their hydrogen atoms. The degraded product is known as "kerogen". With further diagenesis and metamorphism, all the hydrogen atoms are lost and the carbonaceous matter becomes graphite. until the remnant carbonaceous material become graphitised. This last sentence reads a bit as if ALL these macromolecules break down and end up as graphite., but since we find 441 this is not true for all of the macromolecules. We have traced fossilised polymer and biofilms in rocks from throughout Earth's history, to rocks as old as the oldest being 3.5 b.y.-old. Furthermore, Time of Flight Secondary Ion Mass Spectrometry has been able to identify individual macromolecules of bacterial origin, the identities of which are still being investigated, in all the samples containing fossil biofilm, including the 3.5 b.y..-old carbonaceous cherts from South Africa and Australia. As a result of the unique compositional, structural and "mineralisable" properties of bacterial polymer and biofilms, we conclude that bacterial polymers and biofilms constitute a robust and reliable biomarker for life on Earth and could be a potential biomarker for extraterrestrial life.

Ice nucleation rates of single protein complexes and single macromolecules

NASA Astrophysics Data System (ADS)

Stratmann, F.; Wex, H.; Niedermeier, D.; Hartmann, S.; Augustin, S.; Clauss, T.; Voigtlaender, J.; Pummer, B.; Grothe, H.

2012-12-01

With our flow-tube LACIS (Leipzig Aerosol cloud Interaction Simulator), we measured immersion freezing of droplets containing biological ice nucleating (IN) agents. From our measurements, we were able to deduce ice nucleation rates for single IN protein complexes (for Snomax) and for IN macromolecules (in the case of Birch pollen). For the measurements, aerosol particles were produced from solutions/suspensions of either Snomax (deadened and partly fractionalized pseudomonas syringae bacteria) or of Birch pollen washing water (BW in the following). All particles were dried and size selected before entering LACIS. In LACIS, particles were activated to droplets, and we measured the fraction of all droplets that froze (F(ice)) as function of temperature. For Snomax, a strong increase in F(ice) was observed around -7 to -10°C, for BW around -19 to -25°C, respectively. After this initial steep increase, F(ice) stayed constant for both examined substances down to -35°C. We found that the values of F(ice) in the plateau region depended on the dry particle size. The initial solution used to generate the particles contained parts of bacteria with ice active protein complexes on them in the case of Snomax, or IN macromolecules in the case of BW (Pummer et al., 2011). We show that the distribution of the IN proteins or IN molecules in the aerosol particles follows the Poisson distribution. With this knowledge, derivation of the ice nucleation rates for single IN protein complexes or for single IN macromolecules is possible. Combining the Poisson distribution with a stochastic model and using the derived nucleation rates, we can reproduce not only our measurements for both examined substances, but also past measurements done for Snomax and even pseudomonas syringae bacteria. As an additional peculiarity, we seem to observe two different macromolecules being ice active for Birch trees growing in Central Europe or Northern Europe, with the latter initiating freezing at slightly warmer temperatures. Pummer, B. G. et al. (2012), Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Aerosol Chem. Phys., 12, 2541-2550.

Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry.

PubMed

Otsuka, Makoto; Ishii, Mika; Matsuda, Yoshihisa

2003-01-01

The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surface-modified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60 degrees C via the adsorption of n-butanol, and powder x-ray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surface-modified CBZ anhydrate at 97% relative humidity (RH) and 40 +/-C 1 degrees C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37 +/-C 0.5 degrees C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified sample's at each temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102 +/-C 0.008 mg(1/3) x min(-1) and 0.1442 +/-C 0.0482 mg(1/3) x min(-1). The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.

25th anniversary article: CVD polymers: a new paradigm for surface modification and device fabrication.

PubMed

Coclite, Anna Maria; Howden, Rachel M; Borrelli, David C; Petruczok, Christy D; Yang, Rong; Yagüe, Jose Luis; Ugur, Asli; Chen, Nan; Lee, Sunghwan; Jo, Won Jun; Liu, Andong; Wang, Xiaoxue; Gleason, Karen K

2013-10-11

Well-adhered, conformal, thin (<100 nm) coatings can easily be obtained by chemical vapor deposition (CVD) for a variety of technological applications. Room temperature modification with functional polymers can be achieved on virtually any substrate: organic, inorganic, rigid, flexible, planar, three-dimensional, dense, or porous. In CVD polymerization, the monomer(s) are delivered to the surface through the vapor phase and then undergo simultaneous polymerization and thin film formation. By eliminating the need to dissolve macromolecules, CVD enables insoluble polymers to be coated and prevents solvent damage to the substrate. CVD film growth proceeds from the substrate up, allowing for interfacial engineering, real-time monitoring, and thickness control. Initiated-CVD shows successful results in terms of rationally designed micro- and nanoengineered materials to control molecular interactions at material surfaces. The success of oxidative-CVD is mainly demonstrated for the deposition of organic conducting and semiconducting polymers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-ray photoelectron spectroscopic analysis of rice kernels and flours: Measurement of surface chemical composition.

PubMed

Nawaz, Malik A; Gaiani, Claire; Fukai, Shu; Bhandari, Bhesh

2016-12-01

The objectives of this study were to evaluate the ability of X-ray photoelectron spectroscopy (XPS) to differentiate rice macromolecules and to calculate the surface composition of rice kernels and flours. The uncooked kernels and flours surface composition of the two selected rice varieties, Thadokkham-11 (TDK11) and Doongara (DG) demonstrated an over-expression of lipids and proteins and an under-expression of starch compared to the bulk composition. The results of the study showed that XPS was able to differentiate rice polysaccharides (mainly starch), proteins and lipids in uncooked rice kernels and flours. Nevertheless, it was unable to distinguish components in cooked rice samples possibly due to complex interactions between gelatinized starch, denatured proteins and lipids. High resolution imaging methods (Scanning Electron Microscopy and Confocal Laser Scanning Microscopy) were employed to obtain complementary information about the properties and location of starch, proteins and lipids in rice kernels and flours. Copyright © 2016. Published by Elsevier Ltd.

Modeling Pressure-Driven Transport of Proteins through a Nanochannel

PubMed Central

Carr, Rogan; Comer, Jeffrey; Ginsberg, Mark D.; Aksimentiev, Aleksei

2012-01-01

Reducing the size of a nanofluidic channel not only creates new opportunities for high-precision manipulation of biological macromolecules, but also makes the performance of the entire nanofluidic system more susceptible to undesirable interactions between the transported biomolecules and the walls of the channel. In this manuscript, we report molecular dynamics simulations of a pressure-driven flow through a silica nanochannel that characterized, with atomic resolution, adsorption of a model protein to its surface. Although the simulated adsorption of the proteins was found to be nonspecific, it had a dramatic effect on the rate of the protein transport. To determine the relative strength of the protein–silica interactions in different adsorbed states, we simulated flow-induced desorption of the proteins from the silica surface. Our analysis of the protein conformations in the adsorbed states did not reveal any simple dependence of the adsorption strength on the size and composition of the protein–silica contact, suggesting that the heterogeneity of the silica surface may be a important factor. PMID:22611338

Adsorption and self-assembly of M13 phage into directionally organized structures on C and SiO2 films.

PubMed

Moghimian, Pouya; Srot, Vesna; Rothenstein, Dirk; Facey, Sandra J; Harnau, Ludger; Hauer, Bernhard; Bill, Joachim; van Aken, Peter A

2014-09-30

A versatile method for the directional assembly of M13 phage using amorphous carbon and SiO2 thin films was demonstrated. A high affinity of the M13 phage macromolecules for incorporation into aligned structures on an amorphous carbon surface was observed at the concentration range, in which the viral nanofibers tend to disorder. In contrast, the viral particles showed less freedom to adopt an aligned orientation on SiO2 films when deposited in close vicinity. Here an interpretation of the role of the carbon surface in significant enhancement of adsorption and generation of viral arrays with a high orientational order was proposed in terms of surface chemistry and competitive electrostatic interactions. This study suggests the use of amorphous carbon substrates as a template for directional organization of a closely-packed and two-dimensional M13 viral film, which can be a promising route to mineralize a variety of smooth and homogeneous inorganic nanostructure layers.

High-Frequency Electron Paramagnetic Resonance Spectroscopy of Nitroxide-Functionalized Nanodiamonds in Aqueous Solution.

PubMed

Akiel, R D; Stepanov, V; Takahashi, S

2017-06-01

Nanodiamond (ND) is an attractive class of nanomaterial for fluorescent labeling, magnetic sensing of biological molecules, and targeted drug delivery. Many of those applications require tethering of target biological molecules on the ND surface. Even though many approaches have been developed to attach macromolecules to the ND surface, it remains challenging to characterize dynamics of tethered molecule. Here, we show high-frequency electron paramagnetic resonance (HF EPR) spectroscopy of nitroxide-functionalized NDs. Nitroxide radical is a commonly used spin label to investigate dynamics of biological molecules. In the investigation, we developed a sample holder to overcome water absorption of HF microwave. Then, we demonstrated HF EPR spectroscopy of nitroxide-functionalized NDs in aqueous solution and showed clear spectral distinction of ND and nitroxide EPR signals. Moreover, through EPR spectral analysis, we investigate dynamics of nitroxide radicals on the ND surface. The demonstration sheds light on the use of HF EPR spectroscopy to investigate biological molecule-functionalized nanoparticles.

Outcome of the First wwPDB/CCDC/D3R Ligand Validation Workshop

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

Adams, Paul  D.; Aertgeerts, Kathleen; Bauer, Cary

Crystallographic studies of ligands bound to biological macromolecules (proteins and nucleic acids) represent an important source of information concerning drug-target interactions, providing atomic level insights into the physical chemistry of complex formation between macromolecules and ligands. Of the more than 115,000 entries extant in the Protein Data Bank archive, ~75% include at least one non-polymeric ligand. Ligand geometrical and stereochemical quality, the suitability of ligand models for in silico drug discovery/design, and the goodness-of-fit of ligand models to electron density maps vary widely across the archive. We describe the proceedings and conclusions from the first Worldwide Protein Data Bank/Cambridge Crystallographicmore » Data Centre/Drug Design Data Resource (wwPDB/CCDC/D3R) Ligand Validation Workshop held at the Research Collaboratory for Structural Bioinformatics at Rutgers University on July 30-31, 2015. Experts in protein crystallography from academe and industry came together with non-profit and for-profit software providers for crystallography and with experts in computational chemistry and data archiving to discuss and make recommendations on best practices, as framed by a series of questions central to structural studies of macromolecule-ligand complexes. What data concerning bound ligands should be archived in the Protein Data Bank? How should the ligands be best represented? How should structural models of macromolecule-ligand complexes be validated? What supplementary information should accompany publications of structural studies of biological macromolecules? Consensus recommendations on best practices developed in response to each of these questions are provided, together with some details regarding implementation. Important issues addressed but not resolved at the workshop are also enumerated.« less

Outcome of the First wwPDB/CCDC/D3R Ligand Validation Workshop

DOE PAGES

Adams, Paul  D.; Aertgeerts, Kathleen; Bauer, Cary; ...

2016-04-05

Crystallographic studies of ligands bound to biological macromolecules (proteins and nucleic acids) represent an important source of information concerning drug-target interactions, providing atomic level insights into the physical chemistry of complex formation between macromolecules and ligands. Of the more than 115,000 entries extant in the Protein Data Bank archive, ~75% include at least one non-polymeric ligand. Ligand geometrical and stereochemical quality, the suitability of ligand models for in silico drug discovery/design, and the goodness-of-fit of ligand models to electron density maps vary widely across the archive. We describe the proceedings and conclusions from the first Worldwide Protein Data Bank/Cambridge Crystallographicmore » Data Centre/Drug Design Data Resource (wwPDB/CCDC/D3R) Ligand Validation Workshop held at the Research Collaboratory for Structural Bioinformatics at Rutgers University on July 30-31, 2015. Experts in protein crystallography from academe and industry came together with non-profit and for-profit software providers for crystallography and with experts in computational chemistry and data archiving to discuss and make recommendations on best practices, as framed by a series of questions central to structural studies of macromolecule-ligand complexes. What data concerning bound ligands should be archived in the Protein Data Bank? How should the ligands be best represented? How should structural models of macromolecule-ligand complexes be validated? What supplementary information should accompany publications of structural studies of biological macromolecules? Consensus recommendations on best practices developed in response to each of these questions are provided, together with some details regarding implementation. Important issues addressed but not resolved at the workshop are also enumerated.« less

Outcome of the First wwPDB/CCDC/D3R Ligand Validation Workshop.

PubMed

Adams, Paul D; Aertgeerts, Kathleen; Bauer, Cary; Bell, Jeffrey A; Berman, Helen M; Bhat, Talapady N; Blaney, Jeff M; Bolton, Evan; Bricogne, Gerard; Brown, David; Burley, Stephen K; Case, David A; Clark, Kirk L; Darden, Tom; Emsley, Paul; Feher, Victoria A; Feng, Zukang; Groom, Colin R; Harris, Seth F; Hendle, Jorg; Holder, Thomas; Joachimiak, Andrzej; Kleywegt, Gerard J; Krojer, Tobias; Marcotrigiano, Joseph; Mark, Alan E; Markley, John L; Miller, Matthew; Minor, Wladek; Montelione, Gaetano T; Murshudov, Garib; Nakagawa, Atsushi; Nakamura, Haruki; Nicholls, Anthony; Nicklaus, Marc; Nolte, Robert T; Padyana, Anil K; Peishoff, Catherine E; Pieniazek, Susan; Read, Randy J; Shao, Chenghua; Sheriff, Steven; Smart, Oliver; Soisson, Stephen; Spurlino, John; Stouch, Terry; Svobodova, Radka; Tempel, Wolfram; Terwilliger, Thomas C; Tronrud, Dale; Velankar, Sameer; Ward, Suzanna C; Warren, Gregory L; Westbrook, John D; Williams, Pamela; Yang, Huanwang; Young, Jasmine

2016-04-05

Crystallographic studies of ligands bound to biological macromolecules (proteins and nucleic acids) represent an important source of information concerning drug-target interactions, providing atomic level insights into the physical chemistry of complex formation between macromolecules and ligands. Of the more than 115,000 entries extant in the Protein Data Bank (PDB) archive, ∼75% include at least one non-polymeric ligand. Ligand geometrical and stereochemical quality, the suitability of ligand models for in silico drug discovery and design, and the goodness-of-fit of ligand models to electron-density maps vary widely across the archive. We describe the proceedings and conclusions from the first Worldwide PDB/Cambridge Crystallographic Data Center/Drug Design Data Resource (wwPDB/CCDC/D3R) Ligand Validation Workshop held at the Research Collaboratory for Structural Bioinformatics at Rutgers University on July 30-31, 2015. Experts in protein crystallography from academe and industry came together with non-profit and for-profit software providers for crystallography and with experts in computational chemistry and data archiving to discuss and make recommendations on best practices, as framed by a series of questions central to structural studies of macromolecule-ligand complexes. What data concerning bound ligands should be archived in the PDB? How should the ligands be best represented? How should structural models of macromolecule-ligand complexes be validated? What supplementary information should accompany publications of structural studies of biological macromolecules? Consensus recommendations on best practices developed in response to each of these questions are provided, together with some details regarding implementation. Important issues addressed but not resolved at the workshop are also enumerated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Outcome of the first wwPDB/CCDC/D3R Ligand Validation Workshop

PubMed Central

Adams, Paul D.; Aertgeerts, Kathleen; Bauer, Cary; Bell, Jeffrey A.; Berman, Helen M.; Bhat, Talapady N.; Blaney, Jeff; Bolton, Evan; Bricogne, Gerard; Brown, David; Burley, Stephen K.; Case, David A.; Clark, Kirk L.; Darden, Tom; Emsley, Paul; Feher, Victoria A.; Feng, Zukang; Groom, Colin R.; Harris, Seth F.; Hendle, Jorg; Holder, Thomas; Joachimiak, Andrzej; Kleywegt, Gerard J.; Krojer, Tobias; Marcotrigiano, Joseph; Mark, Alan E.; Markley, John L.; Miller, Matthew; Minor, Wladek; Montelione, Gaetano T.; Murshudov, Garib; Nakagawa, Atsushi; Nakamura, Haruki; Nicholls, Anthony; Nicklaus, Marc; Nolte, Robert T.; Padyana, Anil K.; Peishoff, Catherine E.; Pieniazek, Susan; Read, Randy J.; Shao, Chenghua; Sheriff, Steven; Smart, Oliver; Soisson, Stephen; Spurlino, John; Stouch, Terry; Svobodova, Radka; Tempel, Wolfram; Terwilliger, Thomas C.; Tronrud, Dale; Velankar, Sameer; Ward, Suzanna; Warren, Gregory L.; Westbrook, John D.; Williams, Pamela; Yang, Huanwang; Young, Jasmine

2016-01-01

Summary Crystallographic studies of ligands bound to biological macromolecules (proteins and nucleic acids) represent an important source of information concerning drug-target interactions, providing atomic level insights into the physical chemistry of complex formation between macromolecules and ligands. Of the more than 115,000 entries extant in the Protein Data Bank archive, ~75% include at least one non-polymeric ligand. Ligand geometrical and stereochemical quality, the suitability of ligand models for in silico drug discovery/design, and the goodness-of-fit of ligand models to electron density maps vary widely across the archive. We describe the proceedings and conclusions from the first Worldwide Protein Data Bank/Cambridge Crystallographic Data Centre/Drug Design Data Resource (wwPDB/CCDC/D3R) Ligand Validation Workshop held at the Research Collaboratory for Structural Bioinformatics at Rutgers University on July 30–31, 2015. Experts in protein crystallography from academe and industry came together with non-profit and for-profit software providers for crystallography and with experts in computational chemistry and data archiving to discuss and make recommendations on best practices, as framed by a series of questions central to structural studies of macromolecule-ligand complexes. What data concerning bound ligands should be archived in the Protein Data Bank? How should the ligands be best represented? How should structural models of macromolecule-ligand complexes be validated? What supplementary information should accompany publications of structural studies of biological macromolecules? Consensus recommendations on best practices developed in response to each of these questions are provided, together with some details regarding implementation. Important issues addressed but not resolved at the workshop are also enumerated. PMID:27050687

Laser surface modification of 316 L stainless steel with bioactive hydroxyapatite.

PubMed

Balla, Vamsi Krishna; Das, Mitun; Bose, Sreyashree; Ram, G D Janaki; Manna, Indranil

2013-12-01

Laser-engineered net shaping (LENS™), a commercial additive manufacturing process, was used to modify the surfaces of 316 L stainless steel with bioactive hydroxyapatite (HAP). The modified surfaces were characterized in terms of their microstructure, hardness and apatite forming ability. The results showed that with increase in laser energy input from 32 J/mm(2) to 59 J/mm(2) the thickness of the modified surface increased from 222±12 μm to 355±6 μm, while the average surface hardness decreased marginally from 403±18 HV0.3 to 372±8 HV0.3. Microstructural studies showed that the modified surface consisted of austenite dendrites with HAP and some reaction products primarily occurring in the inter-dendritic regions. Finally, the surface-modified 316 L samples immersed in simulated body fluids showed significantly higher apatite precipitation compared to unmodified 316 L samples. © 2013.

Mapping Protein Surface Accessibility via an Electron Transfer Dissociation Selectively Cleavable Hydrazone Probe*

PubMed Central

Vasicek, Lisa; O'Brien, John P.; Browning, Karen S.; Tao, Zhihua; Liu, Hung-Wen; Brodbelt, Jennifer S.

2012-01-01

A protein's surface influences its role in protein-protein interactions and protein-ligand binding. Mass spectrometry can be used to give low resolution structural information about protein surfaces and conformations when used in combination with derivatization methods that target surface accessible amino acid residues. However, pinpointing the resulting modified peptides upon enzymatic digestion of the surface-modified protein is challenging because of the complexity of the peptide mixture and low abundance of modified peptides. Here a novel hydrazone reagent (NN) is presented that allows facile identification of all modified surface residues through a preferential cleavage upon activation by electron transfer dissociation coupled with a collision activation scan to pinpoint the modified residue in the peptide sequence. Using this approach, the correlation between percent reactivity and surface accessibility is demonstrated for two biologically active proteins, wheat eIF4E and PARP-1 Domain C. PMID:22393264

Charge effects on the hindered transport of macromolecules across the endothelial surface glycocalyx layer.

PubMed

Sugihara-Seki, Masako; Akinaga, Takeshi; O-Tani, Hideyuki

2012-01-01

A fluid mechanical and electrostatic model for the transport of solute molecules across the vascular endothelial surface glycocalyx layer (EGL) was developed to study the charge effect on the diffusive and convective transport of the solutes. The solute was assumed to be a spherical particle with a constant surface charge density, and the EGL was represented as an array of periodically arranged circular cylinders of like charge, with a constant surface charge density. By combining the fluid mechanical analyses for the flow around a solute suspended in an electrolyte solution and the electrostatic analyses for the free energy of the interaction between the solute and cylinders based on a mean field theory, we estimated the transport coefficients of the solute across the EGL. Both of diffusive and convective transports are reduced compared to those for an uncharged system, due to the stronger exclusion of the solute that results from the repulsive electrostatic interaction. The model prediction for the reflection coefficient for serum albumin agreed well with experimental observations if the charge density in the EGL is ranged from approximately -10 to -30 mEq/l.

The First Cell Membranes

NASA Technical Reports Server (NTRS)

Deamer, David; Dworkin, Jason P.; Sandford, Scott A.; Bernstein, Max P.; Allamandola, Louis J.

2004-01-01

Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous organic mixtures. Some of these compounds are amphiphilic, having polar and non-polar groups on the same molecule. Amphiphilic compounds spontaneously self-assembly into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to be available on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. A goal of future investigations is to fabricate artificial cells as models of the origin of life.

Interaction between shock wave and single inertial bubbles near an elastic boundary.

PubMed

Sankin, G N; Zhong, P

2006-10-01

The interaction of laser-generated single inertial bubbles (collapse time = 121 mus) near a silicon rubber membrane with a shock wave (55 MPa in peak pressure and 1.7 mus in compressive pulse duration) is investigated. The interaction leads to directional, forced asymmetric collapse of the bubble with microjet formation toward the surface. Maximum jet penetration into the membrane is produced during the bubble collapse phase with optimal shock wave arrival time and stand-off distance. Such interaction may provide a unique acoustic means for in vivo microinjection, applicable to targeted delivery of macromolecules and gene vectors to biological tissues.

Life on Mars? 1: The chemical environment

NASA Technical Reports Server (NTRS)

Banin, A.; Mancinelli, R. L.

1995-01-01

The origin of life at its abiotic evolutionary stage, requires a combination of constituents and environmental conditions that enable the synthesis of complex replicating macromolecules from simpler monomeric molecules. It is very likely that the early stages of this evolutionary process have been spontaneous, rapid and widespread on the surface of the primitive Earth, resulting in the formation of quite sophisticated living organisms within less than a billion years. To what extend did such conditions prevail on Mars? Two companion-papers will review and discuss the available information related to the chemical, physical and environmental conditions on Mars and assess it from the perspective of potential exobiological evolution.

Stability of biogenic metal(loid) nanomaterials related to the colloidal stabilization theory of chemical nanostructures.

PubMed

Piacenza, Elena; Presentato, Alessandro; Turner, Raymond J

2018-02-25

In the last 15 years, the exploitation of biological systems (i.e. plants, bacteria, mycelial fungi, yeasts, and algae) to produce metal(loid) (Me)-based nanomaterials has been evaluated as eco-friendly and a cost-effective alternative to the chemical synthesis processes. Although the biological mechanisms of biogenic Me-nanomaterial (Bio-Me-nanomaterials) production are not yet completely elucidated, a key advantage of such bio-nanostructures over those chemically synthesized is related to their natural thermodynamic stability, with several studies ascribed to the presence of an organic layer surrounding these Bio-Me-nanostructures. Different macromolecules (e.g. proteins, peptides, lipids, DNA, and polysaccharides) or secondary metabolites (e.g. flavonoids, terpenoids, glycosides, organic acids, and alkaloids) naturally produced by organisms have been indicated as main contributors to the stabilization of Bio-Me-nanostructures. Nevertheless, the chemical-physical mechanisms behind the ability of these molecules in providing stability to Bio-Me-nanomaterials are unknown. In this context, transposing the stabilization theory of chemically synthesized Me-nanomaterials (Ch-Me-nanomaterials) to biogenic materials can be used towards a better comprehension of macromolecules and secondary metabolites role as stabilizing agents of Bio-Me-nanomaterials. According to this theory, nanomaterials are generally featured by high thermodynamic instability in suspension, due to their high surface area and surface energy. This feature leads to the necessity to stabilize chemical nanostructures, even during or directly after their synthesis, through the development of (i) electrostatic, (ii) steric, or (iii) electrosteric interactions occurring between molecules and nanomaterials in suspension. Based on these three mechanisms, this review is focused on parallels between the stabilization of biogenic or chemical nanomaterials, suggesting which chemical-physical mechanisms may be involved in the natural stability of Bio-Me-nanomaterials. As a result, macromolecules such as DNA, polyphosphates and proteins may electrostatically interact with Bio-Me-nanomaterials in suspension through their charged moieties, showing the same properties of counterions in Ch-Me-nanostructure suspensions. Since several biomolecules (e.g. neutral lipids, nonionic biosurfactants, polysaccharides, and secondary metabolites) produced by metal(loid)-grown organisms can develop similar steric hindrance as compared to nonionic amphiphilic surfactants and block co-polymers generally used to sterically stabilize Ch-Me-nanomaterials. These biomolecules, most likely, are involved in the development of steric stabilization, because of their bulky structures. Finally, charged lipids and polysaccharides, ionic biosurfactants or proteins with amphiphilic properties can exert a dual effect (i.e. electrostatic and steric repulsion interactions) in the contest of Bio-Me-nanomaterials, leading to the high degree of stability observed.

Rate measurements of the hydrolysis of complex organic macromolecules in cold aqueous solutions: implications for prebiotic chemistry on the early Earth and Titan.

PubMed

Neish, C D; Somogyi, A; Imanaka, H; Lunine, J I; Smith, M A

2008-04-01

Organic macromolecules ("complex tholins") were synthesized from a 0.95 N(2)/0.05 CH(4) atmosphere in a high-voltage AC flow discharge reactor. When placed in liquid water, specific water soluble compounds in the macromolecules demonstrated Arrhenius type first order kinetics between 273 and 313 K and produced oxygenated organic species with activation energies in the range of approximately 60+/-10 kJ mol(-1). These reactions displayed half lives between 0.3 and 17 days at 273 K. Oxygen incorporation into such materials--a necessary step toward the formation of biological molecules--is therefore fast compared to processes that occur on geologic timescales, which include the freezing of impact melt pools and possible cryovolcanic sites on Saturn's organic-rich moon Titan.

Rate Measurements of the Hydrolysis of Complex Organic Macromolecules in Cold Aqueous Solutions: Implications for Prebiotic Chemistry on the Early Earth and Titan

NASA Astrophysics Data System (ADS)

Neish, C. D.; Somogyi, Á.; Imanaka, H .; Lunine, J. I.; Smith, M. A.

2008-04-01

Organic macromolecules (``complex tholins'') were synthesized from a 0.95 N2 / 0.05 CH4 atmosphere in a high-voltage AC flow discharge reactor. When placed in liquid water, specific water soluble compounds in the macromolecules demonstrated Arrhenius type first order kinetics between 273 and 313 K and produced oxygenated organic species with activation energies in the range of ~60 +/- 10 kJ mol-1. These reactions displayed half lives between 0.3 and 17 days at 273 K. Oxygen incorporation into such materials-a necessary step toward the formation of biological molecules-is therefore fast compared to processes that occur on geologic timescales, which include the freezing of impact melt pools and possible cryovolcanic sites on Saturn's organic-rich moon Titan.

Reality of Dental Implant Surface Modification: A Short Literature Review

PubMed Central

Yeo, In-Sung

2014-01-01

Screw-shaped endosseous implants that have a turned surface of commercially pure titanium have a disadvantage of requiring a long time for osseointegration while those implants have shown long-term clinical success in single and multiple restorations. Titanium implant surfaces have been modified in various ways to improve biocompatibility and accelerate osseointegration, which results in a shorter edentulous period for a patient. This article reviewed some important modified titanium surfaces, exploring the in vitro, in vivo and clinical results that numerous comparison studies reported. Several methods are widely used to modify the topography or chemistry of titanium surface, including blasting, acid etching, anodic oxidation, fluoride treatment, and calcium phosphate coating. Such modified surfaces demonstrate faster and stronger osseointegration than the turned commercially pure titanium surface. However, there have been many studies finding no significant differences in in vivo bone responses among the modified surfaces. Considering those in vivo results, physical properties like roughening by sandblasting and acid etching may be major contributors to favorable bone response in biological environments over chemical properties obtained from various modifications including fluoride treatment and calcium phosphate application. Recently, hydrophilic properties added to the roughened surfaces or some osteogenic peptides coated on the surfaces have shown higher biocompatibility and have induced faster osseointegration, compared to the existing modified surfaces. However, the long-term clinical studies about those innovative surfaces are still lacking. PMID:25400716

Toxic properties of specific radiation determinant molecules, derived from radiated species

NASA Astrophysics Data System (ADS)

Popov, Dmitri; Maliev, Vecheslav; Kedar, Prasad; Casey, Rachael; Jones, Jeffrey

Introduction: High doses of radiation induce the formation of radiation toxins in the organs of irradiated mammals. After whole body irradiation, cellular macromolecules and cell walls are damaged as a result of long-lived radiation-induced free radicals, reactive oxygen species, and fast, charged particles of radiation. High doses of radiation induce breaks in the chemical bonds of macromolecules and cross-linking reactions via chemically active processes. These processes result in the creation of novel modified macromolecules that possess specific toxic and antigenic properties defined by the type and dose of irradiation by which they are generated. Radiation toxins isolated from the lymph of irradiated animals are classified as hematotoxic, neurotoxic, and enteric non-bacterial (GI) radiation toxins, and they play an important role in the development of hematopoietic, cerebrovascular, and gastrointestinal acute radiation syndromes (ARS). Seven distinct toxins derived from post-irradiated animals have been designated as Specific Radiation Determinants (SRD): SRD-1 (neurotoxic radiation toxin generated by the cerebrovascular form of ARS), SRD-3 (enteric non-bacterial radiation toxins generated by the gastrointestinal form of ARS), and SRD-4 (hematotoxic radiation toxins generated by the hematological, bone marrow form of ARS). SRD-4 is further subdivided into four groups depending on the severity of the ARS induced: SRD-4/1, mild ARS; SRD-4/2, moderate ARS; SRD-4/3, severe ARS; and SRD-4/4, extremely severe ARS. The seventh SRD, SRD-2 is a toxic extract derived from animals suffering from a fourth form of ARS, as described in European literature and produces toxicity primarily in the autonimic nervous system. These radiation toxins have been shown to be responsible for the induction of important pathophysiological, immunological, and biochemical reactions in ARS. Materials and Methods: These studies incorporated the use of statistically significant numbers of a variety of animals. Lymphatic fluid was collected from the thoracic ducts of bovine species exposed to lethal doses of gamma radiation, and the SRDs were separated by size exclusion gel filtration and high-performance liquid chromatography. We compared the toxicity of isolated radiation toxins in a variety of animals. The clinical characteristics of ARS induced by intravenous or intra-muscular injections of radiation toxins were observed. Results: In radiation-na¨ animals (rats, rabbits, and sheep), toxicity was defined ıve by observing the timing and rate of lethality following injections with extracted radiation toxins (SRDs). Preparations of SRD-1 were injected intra-muscularly in doses of 5 or 10 mg/kg body weight. We observed the development of cerebrovascular ARS with 100% lethality at 10-30 minutes after injection. Analysis of the toxicity of different forms of radiation toxins showed that cerebrovascular neurotoxins possess the highest toxicity compared with other forms of radiation toxins. The other SRD's were also injected into radiation-naive animals and observed for subsequent toxicity/lethality, with the other SRDs producing less virulent forms of ARS. However, both the SRD-2- and SRD-3-injected animals also suffered lethality between 2 and 30 days post-injection. Conclusions: We have observed that radiation toxins are transported from the cells and tissues of irradiated organisms to the interstitial blood and lymphatic fluids, and that this migration of radiation toxins occurs hours after irradiation. Upon analysis of the results of our research and literature sources, we postulate that radiation toxins arise from the radiation-induced chemical modification of macromolecules resident in cell membranes and other cellular structures. Furthermore, we postulate that these altered macromolecules are not processed by antigen processing cells, but instead bind to class II MHC molecules and TCR-beta chains. This causes nonspecific activation of T cells, pro-inflammatory agents such as cytokines and isozymes of phospholipase A2 and phospholipase C, and platelet-activating factor. Longer-term effects induced by the altered macromolecules include the activation of cytotoxic T cells, which induces cytolysis in radiation-damaged cells. Activated CD8+ T cells produce tumor necrosis factor-B and additional cytokines. By these mechanisms, we postulate that radiation toxins generate the pathophysiological reactions associated with acute radiation syndromes.

Lost in Transit: Long-Distance Trafficking and Phloem Unloading of Protein Signals in Arabidopsis Homografts[OPEN

PubMed Central

Gustin, Marie-Paule; Molnar, Attila; Oparka, Karl J.

2016-01-01

In addition to moving sugars and nutrients, the phloem transports many macromolecules. While grafting and aphid stylectomy experiments have identified many macromolecules that move in the phloem, the functional significance of phloem transport of these remains unclear. To gain insight into protein trafficking, we micrografted Arabidopsis thaliana scions expressing GFP-tagged chloroplast transit peptides under the 35S promoter onto nontransgenic rootstocks. We found that plastids in the root tip became fluorescent 10 d after grafting. We obtained identical results with the companion cell-specific promoter SUC2 and with signals that target proteins to peroxisomes, actin, and the nucleus. We were unable to detect the respective mRNAs in the rootstock, indicating extensive movement of proteins in the phloem. Outward movement from the root protophloem was restricted to the pericycle-endodermis boundary, identifying plasmodesmata at this interface as control points in the exchange of macromolecules between stele and cortex. Intriguingly, signals directing proteins to the endoplasmic reticulum and Golgi apparatus from membrane-bound ribosomes were not translocated to the root. It appears that many organelle-targeting sequences are insufficient to prevent the loss of their proteins into the translocation stream. Thus, nonspecific loss of proteins from companion cells to sieve elements may explain the plethora of macromolecules identified in phloem sap. PMID:27600534

Using a water-confined carbon nanotube to probe the electricity of sequential charged segments of macromolecules

NASA Astrophysics Data System (ADS)

Wang, Yu; Zhao, Yan-Jiao; Huang, Ji-Ping

2012-07-01

The detection of macromolecular conformation is particularly important in many physical and biological applications. Here we theoretically explore a method for achieving this detection by probing the electricity of sequential charged segments of macromolecules. Our analysis is based on molecular dynamics simulations, and we investigate a single file of water molecules confined in a half-capped single-walled carbon nanotube (SWCNT) with an external electric charge of +e or -e (e is the elementary charge). The charge is located in the vicinity of the cap of the SWCNT and along the centerline of the SWCNT. We reveal the picosecond timescale for the re-orientation (namely, from one unidirectional direction to the other) of the water molecules in response to a switch in the charge signal, -e → +e or +e → -e. Our results are well understood by taking into account the electrical interactions between the water molecules and between the water molecules and the external charge. Because such signals of re-orientation can be magnified and transported according to Tu et al. [2009 Proc. Natl. Acad. Sci. USA 106 18120], it becomes possible to record fingerprints of electric signals arising from sequential charged segments of a macromolecule, which are expected to be useful for recognizing the conformations of some particular macromolecules.

Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

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

Carrillo, Jan-Michael; Brown, W Michael; Dobrynin, Andrey

2012-01-01

We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. In our simulations the solvent molecules were treated explicitly. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbonemore » deformation. This deformation mode manifests itself in the backbone deformation ratio, , and shear viscosity, , to be universal functions of the Weissenberg number W. The value of the friction coefficient, , and viscosity, , are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, , and friction coefficient, , approaching corresponding values obtained for neutral brush systems.« less

Heterogeneous Nucleation of Dicalcium Phosphate Dihydrate on Modified Silica Surfaces

PubMed Central

Miller, Carrie; Komunjer, Ljepša; Hlady, Vladimir

2012-01-01

Heterogeneous nucleation of dicalcium phosphate dihydrate, CaHPO4•2H2O (DCPD) was studied on untreated planar fused silica and on three modified silica surfaces: octadecylsilyl (OTS) modified silica, human serum albumin treated OTS silica, and UV-oxidized 3-mercaptopropyltriethoxysilyl (MTS) modified silica. The supersaturation ratio of calcium and phosphate solution with respect to DCPD was kept below ~10. The nucleated crystals were observed 24 hours and one week after initial contact between supersaturated solutions and substrate surfaces using bright field and reflectance interference contrast microscopy. No DCPD crystals nucleated on albumin-treated OTS-silica. Majority of the DCDP crystals formed on the other modified silica surfaces appeared to be morphologically similar irrespective of the nature of nucleating substrate. Reflectance interference contrast microscopy provided a proof that the majority of the crystals on these substrates do not develop an extended contact with the substrate surface. The images showed that the most extended contact planes were between the DCPD crystals and MTS modified silica surface. The crystals nucleated on OTS-treated and untreated silica surfaces showed only few or none well-developed contact planes. PMID:25264399

Atomic diffusion in laser surface modified AISI H13 steel

NASA Astrophysics Data System (ADS)

Aqida, S. N.; Brabazon, D.; Naher, S.

2013-07-01

This paper presents a laser surface modification process of AISI H13 steel using 0.09 and 0.4 mm of laser spot sizes with an aim to increase surface hardness and investigate elements diffusion in laser modified surface. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, pulse repetition frequency (PRF), and overlap percentage. The hardness properties were tested at 981 mN force. Metallographic study and energy dispersive X-ray spectroscopy (EDXS) were performed to observe presence of elements and their distribution in the sample surface. Maximum hardness achieved in the modified surface was 1017 HV0.1. Change of elements composition in the modified layer region was detected in the laser modified samples. Diffusion possibly occurred for C, Cr, Cu, Ni, and S elements. The potential found for increase in surface hardness represents an important method to sustain tooling life. The EDXS findings signify understanding of processing parameters effect on the modified surface composition.

Surface Coating of Gypsum-Based Molds for Maxillofacial Prosthetic Silicone Elastomeric Material: The Surface Topography.

PubMed

Khalaf, Salah; Ariffin, Zaihan; Husein, Adam; Reza, Fazal

2015-07-01

This study aimed to compare the surface roughness of maxillofacial silicone elastomers fabricated in noncoated and coated gypsum materials. This study was also conducted to characterize the silicone elastomer specimens after surfaces were modified. A gypsum mold was coated with clear acrylic spray. The coated mold was then used to produce modified silicone experimental specimens (n = 35). The surface roughness of the modified silicone elastomers was compared with that of the control specimens, which were prepared by conventional flasking methods (n = 35). An atomic force microscope (AFM) was used for surface roughness measurement of silicone elastomer (unmodified and modified), and a scanning electron microscope (SEM) was used to evaluate the topographic conditions of coated and noncoated gypsum and silicone elastomer specimens (unmodified and modified) groups. After the gypsum molds were characterized, the fabricated silicone elastomers molded on noncoated and coated gypsum materials were evaluated further. Energy-dispersive X-ray spectroscopy (EDX) analysis of gypsum materials (noncoated and coated) and silicone elastomer specimens (unmodified and modified) was performed to evaluate the elemental changes after coating was conducted. Independent t test was used to analyze the differences in the surface roughness of unmodified and modified silicone at a significance level of p < 0.05. Roughness was significantly reduced in the silicone elastomers processed against coated gypsum materials (p < 0.001). The AFM and SEM analysis results showed evident differences in surface smoothness. EDX data further revealed the presence of the desired chemical components on the surface layer of unmodified and modified silicone elastomers. Silicone elastomers with lower surface roughness of maxillofacial prostheses can be obtained simply by coating a gypsum mold. © 2014 by the American College of Prosthodontists.

Functional Nanofibers via Electospinning: New Materials and Processes

NASA Astrophysics Data System (ADS)

Manasco, Joshua Lee

Cyclodextrins are fascinating, amphiphilic molecules that are of considerable interest due to their ability to be used in a variety of applications ranging from pharmaceuticals and cosmetics to foods and agriculture. These are ring-shaped sugar molecules possess a hydrophobic cavity and a hydrophilic exterior which imparts them water solubility. There are three main types of naturally occurring cyclodextrins namely alpha-, beta- and gamma- CD which have 6, 7 and 8 member rings, respectively. Owing to their hydrophobic interior, cyclodextrin molecules encapsulate hydrophobic guest molecules (from small to macromolecules) to form host-guest supermolecular structures. Chemically modified CDs are often preferred to the natural forms, particularly methylated (MbetaCD) and hydroxypropylated (HPbetaCD) cyclodextrins, for their enhanced solubility and chemical stability. Electrostatic spinning (electrospinning) of nanofibers has drawn significant research attention in recent decades. This technique involves the stretching of a polymer solution or melt in a high electric field to produce fibers on the nanoscale. These 1-Dimensional nanostructures possess extraordinary surface-to-weight ratio and find applications that vary from filtration membranes and tissue scaffolding materials to drug delivery and many others. The scope of this research attempts to leverage the unique features of CDs with the high aspect ratio of nanofibers to create functional nanomaterials. The present study can be divided into three sections. In the first part, we establish that CDs can be electrospun without the need for a "carrier" polymer. This discovery may serve to extend the horizon of what is currently considered "electrospinnable" from macromolecules now to small molecules. The ability to electrospin CDs led to their incorporation of other polymers to create bicomponent fibers with poly (vinyl alcohol) (PVA) and polyacrylonitrile (PAN). In the case of PVA we demonstrate the ability to not only to control the fiber properties based on PVA/CD ratio, but also crosslink these fibers to create water resistant fiber mats. Furthermore, the use of these fibers as rapid dissolving membranes for drug delivery is explored. Additionally, CDs are investigated for use as a porogen for PAN and carbon fibers. We find that CDs are particularly good candidates for us as porogens due to their amorphous nature and versatility to be dissolved in various solvent system. By nature, solution electrospinning is a low-throughput, solvent intensive process. In the last part we attempt to alleviate this issue by designing an extrusion based melt electrospinning device. We show that submicron fibers of polycaprolactone are possible through this technique without the use of organic solvents.

Mucopolysaccharides in aqueous solutions: effect of ionic strength on titration curves.

PubMed

Rueda, C; Arias, C; Galera, P; López-Cabarcos, E; Yagüe, A

2001-01-01

We study the changes taking place in hyaluronic acid, chondroitin 4-sulfate (C4-S) and condroitin 6-sulfate (C6-S), at ionic strengths of 0.10, 0.15, and 0.20 in NaCl, in a neutralization process in aqueous solution. We apply the equation of Henderson Hasselbalch modified for polyelectrolytes and evaluate the changes in the electrostatic free energy starting from the pK curves as a function of the dissociation degree. For a dissociation degree next to 0.4 corresponding to the -COOH group of the hyaluronic acid, we observed a change in the conformation of the three glycosaminoglycans studied. This conformational change takes place as a consequence of the break of intramolecular links and the beginning of the ionization process. The macromolecules in solution show a structure of random coil sufficiently expanded so that the interaction among the close ionizable groups is negligible.

Analyte-Triggered DNA-Probe Release from a Triplex Molecular Beacon for Nanopore Sensing.

PubMed

Guo, Bingyuan; Sheng, Yingying; Zhou, Ke; Liu, Quansheng; Liu, Lei; Wu, Hai-Chen

2018-03-26

A new nanopore sensing strategy based on triplex molecular beacon was developed for the detection of specific DNA or multivalent proteins. The sensor is composed of a triplex-forming molecular beacon and a stem-forming DNA component that is modified with a host-guest complex. Upon target DNA hybridizing with the molecular beacon loop or multivalent proteins binding to the recognition elements on the stem, the DNA probe is released and produces highly characteristic current signals when translocated through α-hemolysin. The frequency of current signatures can be used to quantify the concentrations of the target molecules. This sensing approach provides a simple, quick, and modular tool for the detection of specific macromolecules with high sensitivity and excellent selectivity. It may find useful applications in point-of-care diagnostics with a portable nanopore kit in the future. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid determination of molar mass in modified Archibald experiments using direct fitting of the Lamm equation.

PubMed

Schuck, P; Millar, D B

1998-05-15

A new method is described that allows measurement of the molar mass of the solute within 15 to 30 min after start of a conventional long-column sedimentation equilibrium experiment. A series of scans of the concentration distribution in close vicinity of the meniscus, taken in rapid succession after the start of the centrifuge run, is analyzed by direct fitting using the Lamm equation and the Svedberg equation. In case of a single solute, this analysis of the initial depletion at the meniscus reveals its buoyant molar mass and sedimentation coefficient with an accuracy of approximately 10% and provides gross information about sample heterogeneity. This method can be used to study macromolecules that do not possess the prolonged stability needed in conventional sedimentation equilibrium experiments and it can increase the efficiency of sedimentation equilibrium experiments of previously uncharacterized samples.

Speeding up biomolecular interactions by molecular sledding

DOE PAGES

Turkin, Alexander; Zhang, Lei; Marcozzi, Alessio; ...

2015-10-07

In numerous biological processes associations involve a protein with its binding partner, an event that is preceded by a diffusion-mediated search bringing the two partners together. Often hindered by crowding in biologically relevant environments, three-dimensional diffusion can be slow and result in long bimolecular association times. Moreover, the initial association step between two binding partners often represents a rate-limiting step in biotechnologically relevant reactions. We also demonstrate the practical use of an 11-a.a. DNA-interacting peptide derived from adenovirus to reduce the dimensionality of diffusional search processes and speed up associations between biological macromolecules. We functionalize binding partners with the peptidemore » and demonstrate that the ability of the peptide to one-dimensionally diffuse along DNA results in a 20-fold reduction in reaction time. We also show that modifying PCR primers with the peptide sled enables significant acceleration of standard PCR reactions.« less

Effect of dynamic high pressure on technological properties of cashew tree gum (Anacardium occidentale L.).

PubMed

Porto, Bruna Castro; Augusto, Pedro E D; Terekhov, Anton; Hamaker, Bruce R; Cristianini, Marcelo

2015-09-20

Dynamic high pressure (DHP) appears to be an alternative approach to physical modification of polysaccharides aimed improving their technological properties. Therefore, its effect on the functional properties of polysaccharides (i.e., oil absorption capacity, emulsifier, and rheology) needs to be investigated. Cashew tree gum (CG) is a biological macromolecule that has been proposed to be used as an emulsifier in beverage emulsions. To the best of our knowledge, none of the articles in the literature investigates the effect of DHP on the CG properties. This work presents a study on the evaluation of the effects of DHP on functional characteristics of CG, including rheological properties, molecular weight, glycosyl-linkage analysis, solubility, swelling and oil absorption capacity (OAC). The results suggest that DHP is able to modify the technological properties of cashew tree gum (increasing solubility and decreasing apparent viscosity). Copyright © 2015 Elsevier Ltd. All rights reserved.

[Preparation of poly(methyl acrylate) microfluidic chips surface-modified by hyperbranched polyamide ester and their application in the separation of biomolecules].

PubMed

Liu, Bing; Lin, Donge; Xu, Lin; Lei, Yanhui; Bo, Qianglong; Shou, Chongqi

2012-05-01

The surface of poly (methyl acrylate) (PMMA) microfluidic chips were modified using hyperbranched polyamide ester via chemical bonding. The contact angles of the modified chips were measured. The surface morphology was observed by scanning electron microscope (SEM) and stereo microscope. The results showed that the surface of the modified chips was coated by a dense, uniform, continuous, hydrophilic layer of hyperbranched polyamide ester. The hydrophilic of the chip surface was markedly improved. The contact angle of the chips modified decreased from 89.9 degrees to 29.5 degrees. The electro osmotic flow (EOF) in the modified microchannel was lower than that in the unmodified microchannel. Adenosine and L-lysine were detected and separated via the modified PMMA microfluidic chips. Compared with unmodified chips, the modified chips successfully separated the two biomolecules. The detection peaks were clear and sharp. The separation efficiencies of adenosine and L-lysine were 8.44 x 10(4) plates/m and 9.82 x 10(4) plates/m respectively, and the resolutions (Rs) was 5.31. The column efficiencies and resolutions of the modified chips were much higher than those of the unmodified chips. It was also observed that the modified chips possessed good reproducibility of migration time. This research may provide a new and effective method to improve the hydrophilicity of the PMMA surface and the application of PMMA microfluidic chips in the determination of trace biomolecules.

Characterization of ion beam modified ceramic wear surfaces using Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Wei, W.; Lankford, J.

1987-01-01

An investigation of the surface chemistry and morphology of the wear surfaces of ceramic material surfaces modified by ion beam mixing has been conducted using Auger electron spectroscopy and secondary electron microscopy. Studies have been conducted on ceramic/ceramic friction and wear couples made up of TiC and NiMo-bonded TiC cermet pins run against Si3N4 and partially stabilized zirconia disc surfaces modified by the ion beam mixing of titanium and nickel, as well as ummodified ceramic/ceramic couples in order to determine the types of surface changes leading to the improved friction and wear behavior of the surface modified ceramics in simulated diesel environments. The results of the surface analyses indicate that the formation of a lubricating oxide layer of titanium and nickel, is responsible for the improvement in ceramic friction and wear behavior. The beneficial effect of this oxide layer depends on several factors, including the adherence of the surface modified layer or subsequently formed oxide layer to the disc substrate, the substrate materials, the conditions of ion beam mixing, and the environmental conditions.

Rubber-Modified Epoxy and Glass Laminates for Application to Naval Ship Structures.

DTIC Science & Technology

1983-09-01

more information. Two generic carboxy terminated butadiene acrylonitrile ( CTBN )-modified epoxy/glass cloth material systems have been characterized...versus Normal Impact Energy of 7781-Z6040/Fl55 .......... .................... 8 4 - Front Surface of CTBN -Modified Epoxy GRP Panel After 60 Impacts at...15 6 - Back Surface of CTBN -Modified Epoxy GRP Panel After 60 Impacts at 206 Foot-Pounds ..... .................. ... 16 7 - Back Surface of

X-ray crystallography and its impact on understanding bacterial cell wall remodeling processes.

PubMed

Büttner, Felix Michael; Renner-Schneck, Michaela; Stehle, Thilo

2015-02-01

The molecular structure of matter defines its properties and function. This is especially true for biological macromolecules such as proteins, which participate in virtually all biochemical processes. A three dimensional structural model of a protein is thus essential for the detailed understanding of its physiological function and the characterization of essential properties such as ligand binding and reaction mechanism. X-ray crystallography is a well-established technique that has been used for many years, but it is still by far the most widely used method for structure determination. A particular strength of this technique is the elucidation of atomic details of molecular interactions, thus providing an invaluable tool for a multitude of scientific projects ranging from the structural classification of macromolecules over the validation of enzymatic mechanisms or the understanding of host-pathogen interactions to structure-guided drug design. In the first part of this review, we describe essential methodological and practical aspects of X-ray crystallography. We provide some pointers that should allow researchers without a background in structural biology to assess the overall quality and reliability of a crystal structure. To highlight its potential, we then survey the impact X-ray crystallography has had on advancing an understanding of a class of enzymes that modify the bacterial cell wall. A substantial number of different bacterial amidase structures have been solved, mostly by X-ray crystallography. Comparison of these structures highlights conserved as well as divergent features. In combination with functional analyses, structural information on these enzymes has therefore proven to be a valuable template not only for understanding their mechanism of catalysis, but also for targeted interference with substrate binding. Copyright © 2015 Elsevier GmbH. All rights reserved.

Diffuse Reflectance FT-IR Of Surface Modified Kevlar

NASA Astrophysics Data System (ADS)

Benrashid, R.; Tesoro, G.; McKenzie, M. T., Jr.

1989-12-01

Diffuse reflectance FT-IR (DRIFT) has been applied to the characterization of surface modified Kevlar 29 and 49 fibers. The surface modifications include amination and sulfonation. The standard DRIFT experiment has been modified in the manner first described by Koenig et.al. 1 who used a KBR overlayer to enhance surface functional IR bands. The results from the DRIFT experiment have been correlated with those from a standard dye test. The results for degree of modification are in reasonable agreement between the two measurement approaches. However, the dye experiment is time-consuming and inconvenient. DRIFT has been shown to be useful in characterizing modified Kevlar surfaces in as-used conditions.

Fabrication and Characterization of Conductive Conjugated Polymer-Coated Antheraea mylitta Silk Fibroin Fibers for Biomedical Applications.

PubMed

Gh, Darshan; Kong, Dexu; Gautrot, Julien; Vootla, Shyam Kumar

2017-07-01

Conductive polymers are interesting materials for a number of biological and medical applications requiring electrical stimulation of cells or tissues. Highly conductive polymers (polypyrrole and polyaniline)/Antheraea mylitta silk fibroin coated fibers are fabricated successfully by in situ polymerization without any modification of the native silk fibroin. Coated fibers characterized by scanning electron microscopy confirm the silk fiber surface is covered by conductive polymers. Thermogravimetric analysis reveals preserved thermal stability of silk fiber after coating process. X-ray diffraction of degummed fiber diffraction peaks at around 2θ = 20.4 and 16.5 confirms the preservation of the β-sheet structure typical of degummed silk II fibers. This phenomenon implies that both polypyrrole and polyaniline chains form interactions with peptide linkages in degummed fiber macromolecules, without significantly disrupting protein assembly. Fourier transform infrared spectroscopy of coated fibers indicates hydrogen bonding and electrostatic interactions exist between silk fibroin macromolecules and conductive polymers. Resulting fibers display good conductive properties compared to corresponding conjugated polymers. In vitro analysis (live/dead assay) of the behavior of human immortalized keratinocytes (HaCaTs) on coated fibers demonstrates improved cell-adhesive properties and viability after polymers coating. Hence, polypyrrole- and polyaniline-coated A. mylitta silk fibers are suitable for application in cell culture and for tissue engineering, where electrical conduction properties are required. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous-Flow Electrophoresis of DNA and Proteins in a Two-Dimensional Capillary-Well Sieve.

PubMed

Duan, Lian; Cao, Zhen; Yobas, Levent

2017-09-19

Continuous-flow electrophoresis of macromolecules is demonstrated using an integrated capillary-well sieve arranged into a two-dimensional anisotropic array on silicon. The periodic array features thousands of entropic barriers, each resulting from an abrupt interface between a 2 μm deep well (channel) and a 70 nm capillary. These entropic barriers owing to two-dimensional confinement within the capillaries are vastly steep in relation to those arising from slits featuring one-dimensional confinement. Thus, the sieving mechanisms can sustain relatively large electric field strengths over a relatively small array area. The sieve rapidly sorts anionic macromolecules, including DNA chains and proteins in native or denatured states, into distinct trajectories according to size or charge under electric field vectors orthogonally applied. The baseline separation is achieved in less than 1 min within a horizontal migration length of ∼1.5 mm. The capillaries are self-enclosed conduits in cylindrical profile featuring a uniform diameter and realized through an approach that avoids advanced patterning techniques. The approach exploits a thermal reflow of a layer of doped glass for shape transformation into cylindrical capillaries and for controllably shrinking the capillary diameter. Lastly, atomic layer deposition of alumina is introduced for the first time to fine-tune the capillary diameter as well as to neutralize the surface charge, thereby suppressing undesired electroosmotic flows.

Development and characterisation of chitosan films impregnated with insulin loaded PEG-b-PLA nanoparticles (NPs): a potential approach for buccal delivery of macromolecules.

PubMed

Giovino, Concetta; Ayensu, Isaac; Tetteh, John; Boateng, Joshua S

2012-05-30

Mucoadhesive chitosan based films, incorporated with insulin loaded nanoparticles (NPs) made of poly(ethylene glycol)methyl ether-block-polylactide (PEG-b-PLA) have been developed and characterised. Blank-NPs were prepared by double emulsion solvent evaporation technique with varying concentrations of the copolymer (5 and 10%, w/v). The optimised formulation was loaded with insulin (model protein) at initial loadings of 2, 5 and 10% with respect to copolymer weight. The developed NPs were analysed for size, size distribution, surface charge, morphology, encapsulation efficiency and drug release. NPs showing negative (ζ)-potential (<-6 mV) with average diameter> 300 nm and a polydispersity index (P.I.) of ≈ 0.2, irrespective of formulation process, were achieved. Insulin encapsulation efficiencies of 70% and 30% for NPs-Insulin-2 and NPs-Insulin-5 were obtained, respectively. The in vitro release behaviour of both formulations showed a classic biphasic sustained release of protein over 5 weeks which was influenced by pH of the release medium. Optimised chitosan films embedded with 3mg of insulin loaded NPs were produced by solvent casting with homogeneous distribution of NPs in the mucoadhesive matrix, which displayed excellent physico-mechanical properties. The drug delivery system has been designed as a novel platform for potential buccal delivery of macromolecules. Copyright © 2012 Elsevier B.V. All rights reserved.

Improved data visualization techniques for analyzing macromolecule structural changes.

PubMed

Kim, Jae Hyun; Iyer, Vidyashankara; Joshi, Sangeeta B; Volkin, David B; Middaugh, C Russell

2012-10-01

The empirical phase diagram (EPD) is a colored representation of overall structural integrity and conformational stability of macromolecules in response to various environmental perturbations. Numerous proteins and macromolecular complexes have been analyzed by EPDs to summarize results from large data sets from multiple biophysical techniques. The current EPD method suffers from a number of deficiencies including lack of a meaningful relationship between color and actual molecular features, difficulties in identifying contributions from individual techniques, and a limited ability to be interpreted by color-blind individuals. In this work, three improved data visualization approaches are proposed as techniques complementary to the EPD. The secondary, tertiary, and quaternary structural changes of multiple proteins as a function of environmental stress were first measured using circular dichroism, intrinsic fluorescence spectroscopy, and static light scattering, respectively. Data sets were then visualized as (1) RGB colors using three-index EPDs, (2) equiangular polygons using radar charts, and (3) human facial features using Chernoff face diagrams. Data as a function of temperature and pH for bovine serum albumin, aldolase, and chymotrypsin as well as candidate protein vaccine antigens including a serine threonine kinase protein (SP1732) and surface antigen A (SP1650) from S. pneumoniae and hemagglutinin from an H1N1 influenza virus are used to illustrate the advantages and disadvantages of each type of data visualization technique. Copyright © 2012 The Protein Society.

Improved data visualization techniques for analyzing macromolecule structural changes

PubMed Central

Kim, Jae Hyun; Iyer, Vidyashankara; Joshi, Sangeeta B; Volkin, David B; Middaugh, C Russell

2012-01-01

The empirical phase diagram (EPD) is a colored representation of overall structural integrity and conformational stability of macromolecules in response to various environmental perturbations. Numerous proteins and macromolecular complexes have been analyzed by EPDs to summarize results from large data sets from multiple biophysical techniques. The current EPD method suffers from a number of deficiencies including lack of a meaningful relationship between color and actual molecular features, difficulties in identifying contributions from individual techniques, and a limited ability to be interpreted by color-blind individuals. In this work, three improved data visualization approaches are proposed as techniques complementary to the EPD. The secondary, tertiary, and quaternary structural changes of multiple proteins as a function of environmental stress were first measured using circular dichroism, intrinsic fluorescence spectroscopy, and static light scattering, respectively. Data sets were then visualized as (1) RGB colors using three-index EPDs, (2) equiangular polygons using radar charts, and (3) human facial features using Chernoff face diagrams. Data as a function of temperature and pH for bovine serum albumin, aldolase, and chymotrypsin as well as candidate protein vaccine antigens including a serine threonine kinase protein (SP1732) and surface antigen A (SP1650) from S. pneumoniae and hemagglutinin from an H1N1 influenza virus are used to illustrate the advantages and disadvantages of each type of data visualization technique. PMID:22898970

Structural adaptation of extreme halophilic proteins through decrease of conserved hydrophobic contact surface

PubMed Central

2011-01-01

Background Halophiles are extremophilic microorganisms growing optimally at high salt concentrations. There are two strategies used by halophiles to maintain proper osmotic pressure in their cytoplasm: accumulation of molar concentrations of potassium and chloride with extensive adaptation of the intracellular macromolecules ("salt-in" strategy) or biosynthesis and/or accumulation of organic osmotic solutes ("osmolyte" strategy). Our work was aimed at contributing to the understanding of the shared molecular mechanisms of protein haloadaptation through a detailed and systematic comparison of a sample of several three-dimensional structures of halophilic and non-halophilic proteins. Structural differences observed between the "salt-in" and the mesophilic homologous proteins were contrasted to those observed between the "osmolyte" and mesophilic pairs. Results The results suggest that haloadaptation strategy in the presence of molar salt concentration, but not of osmolytes, necessitates a weakening of the hydrophobic interactions, in particular at the level of conserved hydrophobic contacts. Weakening of these interactions counterbalances their strengthening by the presence of salts in solution and may help the structure preventing aggregation and/or loss of function in hypersaline environments. Conclusions Considering the significant increase of biotechnology applications of halophiles, the understanding of halophilicity can provide the theoretical basis for the engineering of proteins of great interest because stable at concentrations of salts that cause the denaturation or aggregation of the majority of macromolecules. PMID:22192175

Microfiberoptic fluorescence photobleaching reveals size-dependent macromolecule diffusion in extracellular space deep in brain.

PubMed

Zador, Zsolt; Magzoub, Mazin; Jin, Songwan; Manley, Geoffrey T; Papadopoulos, Marios C; Verkman, A S

2008-03-01

Diffusion in brain extracellular space (ECS) is important for nonsynaptic intercellular communication, extracellular ionic buffering, and delivery of drugs and metabolites. We measured macromolecular diffusion in normally light-inaccessible regions of mouse brain by microfiberoptic epifluorescence photobleaching, in which a fiberoptic with a micron-size tip is introduced deep in brain tissue. In brain cortex, the diffusion of a noninteracting molecule [fluorescein isothiocyanate (FITC)-dextran, 70 kDa] was slowed 4.5 +/- 0.5-fold compared with its diffusion in water (D(o)/D), and was depth-independent down to 800 microm from the brain surface. Diffusion was significantly accelerated (D(o)/D of 2.9+/-0.3) in mice lacking the glial water channel aquaporin-4. FITC-dextran diffusion varied greatly in different regions of brain, with D(o)/D of 3.5 +/- 0.3 in hippocampus and 7.4 +/- 0.3 in thalamus. Remarkably, D(o)/D in deep brain was strongly dependent on solute size, whereas diffusion in cortex changed little with solute size. Mathematical modeling of ECS diffusion required nonuniform ECS dimensions in deep brain, which we call "heterometricity," to account for the size-dependent diffusion. Our results provide the first data on molecular diffusion in ECS deep in brain in vivo and demonstrate previously unrecognized hindrance and heterometricity for diffusion of large macromolecules in deep brain.

Astrobiological Effects of Stellar Radiation in Circumstellar Environments

NASA Astrophysics Data System (ADS)

Cuntz, Manfred; Gurdemir, Levent; Guinan, Edward F.; Kurucz, Robert L.

2006-10-01

The centerpiece of all life on Earth is carbon-based biochemistry. Previous scientific research has suggested that biochemistry based on carbon may also play a decisive role in extraterrestrial life forms, i.e., alien life outside of Earth, if existent. In the following, we explore if carbon-based macromolecules (such as DNA) in the environments of stars other than the Sun are able to survive the effects of energetic stellar radiation, such as UV-C in the wavelength band between 200 and 290 nm. We focus on main-sequence stars akin to the Sun, but of hotter (F-type stars) and cooler (K- and M-type stars) surface temperature. Emphasis is placed on investigating the radiative environment in stellar habitable zones (HZs). Stellar habitable zones have an important relevance in astrobiology because they constitute circumstellar regions in which a planet of suitable size can have surface temperatures for water to exist in liquid form.

Osmolyte depletion viewed in terms of the dividing membrane and its work of expansion against osmotic pressure.

PubMed

Shimizu, Seishi; Matubayasi, Nobuyuki

2017-12-01

How osmolytes enhance the folding, binding, and self-assembly of biological macromolecules at a microscopic scale has long been a matter of debate. Ambiguities persist on the key interpretive concepts, such as the "effective membrane" (which marks the boundary of the volume from which osmolytes are excluded) and the "free energy of exclusion" of osmolytes from biomolecular surfaces. In this paper, we formulate these elusive concepts based upon chemical thermodynamics and rigorous statistical thermodynamics (the Kirkwood-Buff theory). Positioning of the membrane at the osmotic dividing surface is crucial in order not to affect the thermodynamics of solvation. The notion of the free energy (work) of excluding osmolytes is refined to the expansion work against the osmotic pressure, which indeed describes the change of solvation free energy at dilute osmolyte concentrations. Copyright © 2017 Elsevier B.V. All rights reserved.

Applications of nanodiamonds in drug delivery and catalysis.

PubMed

Moosa, Basem; Fhayli, Karim; Li, Song; Julfakyan, Khatchatur; Ezzeddine, Alaa; Khashab, Niveen M

2014-01-01

The interest of researchers in utilizing nanomaterials as carriers for a wide spectrum of molecules has exploded in the last two decades. Nanodiamonds are one class of carbon-based nanomaterials that have emerged as promising drug delivery vehicles and imaging probes. Their ease of functionalization also led to the generation of stimuli-responsive nanodiamonds that deliver drugs on demand in a controlled manner. The ample surface area of NDs allowed for a higher loading of not only small molecules but also macromolecules like genes and proteins. Recently, the unique surface of NDs has attracted more attention as catalyst support in a huge range of organic modification and C-C bond formation reactions. Herein, recent advances in the utilization of nanodiamonds as a drug delivery vehicle and catalytical support are highlighted and summarized to illustrate the potential and versatility of this cheap and commercially available nanomaterial.

Adsorption of polyethyleneimine and polymethacrylic acid onto synthesized hematite.

PubMed

Chibowski, S; Patkowski, J; Grzadka, E

2009-01-01

An influence of different functional groups of polymer, its molecular weight, polydispersity ratio (M(w)/M(n)) and presence of impurities on its adsorption in different pH values (3, 6 and 9) onto synthesized hematite (Fe(2)O(3)) was measured. A structure of adsorbed macromolecules of PMA and PEI was obtained according to S-F theory. Two polymers were used: polymethacrylic acid (PMA) of 6500 and 75,100 molecular weight as well as polyethyleneimine (PEI) 25,000 commercial and fractionated. Electrokinetic properties of the interface oxide-polymer solution (surface charge density and zeta potential) were also measured as well as adsorption layer thicknesses (with use of viscosimetric measurements). Obtained data show, that all above-mentioned factors do influence not only the adsorption process itself but also a surface charge, zeta potential and structure of adsorbed polymer layers on polymer/hematite interface.

Dynamic patterns in a supported lipid bilayer driven by standing surface acoustic waves.

PubMed

Hennig, Martin; Neumann, Jürgen; Wixforth, Achim; Rädler, Joachim O; Schneider, Matthias F

2009-11-07

In the past decades supported lipid bilayers (SLBs) have been an important tool in order to study the physical properties of biological membranes and cells. So far, controlled manipulation of SLBs is very limited. Here we present a new technology to create lateral patterns in lipid membranes controllable in both space and time. Surface acoustic waves (SAWs) are used to generate lateral standing waves on a piezoelectric substrate which create local "traps" in the lipid bilayer and lead to a lateral modulation in lipid concentration. We demonstrate that pattern formation is reversible and does not affect the integrity of the lipid bilayer as shown by extracting the diffusion constant of fluid membranes. The described method could possibly be used to design switchable interfaces for the lateral transport and organization of membrane bound macromolecules to create dynamic bioarrays and control biofilm formation.

Liquid in a tube oscillating along its axis

NASA Astrophysics Data System (ADS)

Zhdanov, Vladimir P.; Kasemo, Bengt

2015-06-01

The Quartz Crystal Microbalance with Dissipation (QCM-D) sensing technique has become widely used to study various supported thin films and adsorption of biological macromolecules, nanoparticles, aggregates, and cells. Such sensing, based on tracking shear oscillations of a piezoelectric crystal, can be employed in situations which are far beyond conventional ones. For example, one can deposit tubes on the surface of a sensor, orient them along the direction of the sensor surface oscillations, and study liquid oscillations inside the oscillating tubes. Herein, we illustrate and classify theoretically the regimes of liquid oscillations in this case. In particular, we identify and scrutinize the transition from the regime with appreciable gradients along the radial coordinate, which are qualitatively similar to those near the oscillating flat interface, to the regime where the liquid oscillates nearly coherently in the whole tube. The results are not only of relevance for the specific case of nanotubes but also for studies of certain mesoporous samples.

The mucosal immune system in health and disease, with an emphasis on parasitic infection

PubMed Central

Allardyce, R. A.; Bienenstock, J.

1984-01-01

This article briefly describes the network of immunity involving selected humoral and cellular elements shared between mucosal surfaces that are both exposed to and remote from antigen challenge. The mechanisms promoting the production, concentration, and secretion of specific antibody isotypes, as well as the migration and localization of various lymphoid cell populations, have been discussed with regard to host mucosal protection against pathogenic agents and other potentially harmful macromolecules. Although certain aspects of the mucosal immune system may be viewed as separate from the systemic immune system, they are not exclusively so. We have drawn attention to their interactions with systemic immune reactants and other, nonimmunological, cellular and humoral constituents of mucosal surfaces and tissues such as the liver. At another level of interaction we have considered the teleological translation of host defence and immunoregulation from one generation to the next through the medium of colostrum and breast milk. The manipulation of the mucosal immune system in order to enhance host resistance, modulate autoimmune and allergic systemic reactivity, or even modify fertility holds great promise. Achievement of these goals depends on gaining further insight into the mechanisms that contribute to mucosal immunity and their interactions with the systemic immune system. Much of our current knowledge is based upon experimental animal models or human populations living in relative prosperity. However, the results of oral vaccination, for example, are known to differ considerably in populations that suffer from parasitic infestations, lack adequate nutrition, and are very old or very young. We have chosen to focus attention on these groups because they constitute a large proportion of the world's population and because mucosal infections are a common cause of illness and death among them. Lastly, the recent discovery that immune deficiencies due to insufficient dietary zinc may extend to subsequent generations of optimally nourished offspring calls for a re-evaluation of immunization protocols in malnourished populations, and of our current understanding of disease inheritance and susceptibility. PMID:6424959

High-resolution NMR spectroscopy of encapsulated proteins dissolved in low-viscosity fluids

PubMed Central

Nucci, Nathaniel V.; Valentine, Kathleen G.; Wand, A. Joshua

2014-01-01

High-resolution multi-dimensional solution NMR is unique as a biophysical and biochemical tool in its ability to examine both the structure and dynamics of macromolecules at atomic resolution. Conventional solution NMR approaches, however, are largely limited to examinations of relatively small (< 25 kDa) molecules, mostly due to the spectroscopic consequences of slow rotational diffusion. Encapsulation of macromolecules within the protective nanoscale aqueous interior of reverse micelles dissolved in low viscosity fluids has been developed as a means through which the ‘slow tumbling problem’ can be overcome. This approach has been successfully applied to diverse proteins and nucleic acids ranging up to 100 kDa, considerably widening the range of biological macromolecules to which conventional solution NMR methodologies may be applied. Recent advances in methodology have significantly broadened the utility of this approach in structural biology and molecular biophysics. PMID:24656086

Isothermal titration calorimetry for measuring macromolecule-ligand affinity.

PubMed

Duff, Michael R; Grubbs, Jordan; Howell, Elizabeth E

2011-09-07

Isothermal titration calorimetry (ITC) is a useful tool for understanding the complete thermodynamic picture of a binding reaction. In biological sciences, macromolecular interactions are essential in understanding the machinery of the cell. Experimental conditions, such as buffer and temperature, can be tailored to the particular binding system being studied. However, careful planning is needed since certain ligand and macromolecule concentration ranges are necessary to obtain useful data. Concentrations of the macromolecule and ligand need to be accurately determined for reliable results. Care also needs to be taken when preparing the samples as impurities can significantly affect the experiment. When ITC experiments, along with controls, are performed properly, useful binding information, such as the stoichiometry, affinity and enthalpy, are obtained. By running additional experiments under different buffer or temperature conditions, more detailed information can be obtained about the system. A protocol for the basic setup of an ITC experiment is given.

Isothermal Titration Calorimetry for Measuring Macromolecule-Ligand Affinity

PubMed Central

Duff,, Michael R.; Grubbs, Jordan; Howell, Elizabeth E.

2011-01-01

Isothermal titration calorimetry (ITC) is a useful tool for understanding the complete thermodynamic picture of a binding reaction. In biological sciences, macromolecular interactions are essential in understanding the machinery of the cell. Experimental conditions, such as buffer and temperature, can be tailored to the particular binding system being studied. However, careful planning is needed since certain ligand and macromolecule concentration ranges are necessary to obtain useful data. Concentrations of the macromolecule and ligand need to be accurately determined for reliable results. Care also needs to be taken when preparing the samples as impurities can significantly affect the experiment. When ITC experiments, along with controls, are performed properly, useful binding information, such as the stoichiometry, affinity and enthalpy, are obtained. By running additional experiments under different buffer or temperature conditions, more detailed information can be obtained about the system. A protocol for the basic setup of an ITC experiment is given. PMID:21931288

Analysis of the conductivity of plasmodesmata by microinjection.

PubMed

Kragler, Friedrich

2015-01-01

Pressure microinjection can be used to introduce fluorescent dyes and labeled macromolecules into single cells. The method allows measuring transport activity of macromolecules such as proteins and RNA molecules within and between cells. Routinely, plant mesophyll cells are injected with fluorescent dextran molecules of specific sizes to measure an increase of the size exclusion limit of plasmodesmata in the presence of a co-injected or expressed protein. The mobility of a macromolecule can also be addressed directly by injecting a recombinant protein that itself is labeled with fluorescent dye and following its transport to neighboring cells. This chapter describes a pressure microinjection protocol successfully applied to Nicotiana leaves. This protocol requires basic skills and experience in handling a microscope equipped with an imaging system, a micromanipulator, and a microinjection system attached to an upright microscope. Using this equipment, a trained person can inject approximately 10-20 mesophyll cells per hour.

Sparsity of the normal matrix in the refinement of macromolecules at atomic and subatomic resolution.

PubMed

Jelsch, C

2001-09-01

The normal matrix in the least-squares refinement of macromolecules is very sparse when the resolution reaches atomic and subatomic levels. The elements of the normal matrix, related to coordinates, thermal motion and charge-density parameters, have a global tendency to decrease rapidly with the interatomic distance between the atoms concerned. For instance, in the case of the protein crambin at 0.54 A resolution, the elements are reduced by two orders of magnitude for distances above 1.5 A. The neglect a priori of most of the normal-matrix elements according to a distance criterion represents an approximation in the refinement of macromolecules, which is particularly valid at very high resolution. The analytical expressions of the normal-matrix elements, which have been derived for the coordinates and the thermal parameters, show that the degree of matrix sparsity increases with the diffraction resolution and the size of the asymmetric unit.

An Overview of Biological Macromolecule Crystallization

PubMed Central

Krauss, Irene Russo; Merlino, Antonello; Vergara, Alessandro; Sica, Filomena

2013-01-01

The elucidation of the three dimensional structure of biological macromolecules has provided an important contribution to our current understanding of many basic mechanisms involved in life processes. This enormous impact largely results from the ability of X-ray crystallography to provide accurate structural details at atomic resolution that are a prerequisite for a deeper insight on the way in which bio-macromolecules interact with each other to build up supramolecular nano-machines capable of performing specialized biological functions. With the advent of high-energy synchrotron sources and the development of sophisticated software to solve X-ray and neutron crystal structures of large molecules, the crystallization step has become even more the bottleneck of a successful structure determination. This review introduces the general aspects of protein crystallization, summarizes conventional and innovative crystallization methods and focuses on the new strategies utilized to improve the success rate of experiments and increase crystal diffraction quality. PMID:23727935

Interspecies scaling and prediction of human clearance: comparison of small- and macro-molecule drugs

PubMed Central

Huh, Yeamin; Smith, David E.; Feng, Meihau Rose

2014-01-01

Human clearance prediction for small- and macro-molecule drugs was evaluated and compared using various scaling methods and statistical analysis.Human clearance is generally well predicted using single or multiple species simple allometry for macro- and small-molecule drugs excreted renally.The prediction error is higher for hepatically eliminated small-molecules using single or multiple species simple allometry scaling, and it appears that the prediction error is mainly associated with drugs with low hepatic extraction ratio (Eh). The error in human clearance prediction for hepatically eliminated small-molecules was reduced using scaling methods with a correction of maximum life span (MLP) or brain weight (BRW).Human clearance of both small- and macro-molecule drugs is well predicted using the monkey liver blood flow method. Predictions using liver blood flow from other species did not work as well, especially for the small-molecule drugs. PMID:21892879

Regulation of calcite crystal morphology by intracrystalline acidic proteins and glycoproteins.

PubMed

Albeck, S; Addadi, I; Weiner, S

1996-01-01

Many biologically formed calcite crystals contain intracrystalline macromolecules. The ways in which they interact with growing calcite crystals were evaluated by monitoring changes in the morphology of calcite crystals grown in vitro in their presence. Macromolecules were extracted from within isolated prisms from the prismatic layer of the shell of the mollusk Atrina rigida and from spines of the sea urchin Paracentrotus lividus. Two modes of interaction were identified; the interaction of highly acidic proteins with calcite planes perpendicular to the c crystallographic axis and the interaction of glycoproteins with planes roughly parallel to the c axis. By different preparative procedures we demonstrated that the polysaccharide moieties of the sea urchin spine glycoproteins are directly involved in the latter mode of interactions. We suggest that organisms utilize the abilities of these macromolecules to interact in different ways with calcite crystals, and in so doing fine-tune aspects of the control of crystal growth in vivo.

Macromolecule Crystal Quality Improvement in Microgravity: The Role of Impurities

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Snell, Edward H.; Pusey, Marc L.; Sportiello, Michael G.; Todd, Paul; Bellamy, Henry; Borgstahl, Gloria E.; Pokros, Matt; Cassanto, John M.

2000-01-01

While macromolecule impurities may affect crystal size and morphology the over-riding question is; "How do macromolecule impurities effect crystal X-ray quality and diffraction resolution?" In the case of chicken egg white lysozyme, crystals can be grown in the presence of a number of impurities without affecting diffraction resolution. One impurity however, the lysozyme dimer, does negatively impact the X-ray crystal properties. Crystal quality improvement as a result of better partitioning of this impurity during crystallization in microgravity has been reported'. In our recent experimental work dimer partitioning was found to be not significantly different between the two environments. Mosaicity analysis of pure crystals showed a reduced mosaicity and increased signal to noise for the microgravity grown crystals. Dimer incorporation however, did greatly reduce the resolution limit in both ground and microgravity grown crystals. These results indicate that impurity effects in microgravity are complex and may rely on the conditions or techniques employed.

Sequence-controlled methacrylic multiblock copolymers via sulfur-free RAFT emulsion polymerization

NASA Astrophysics Data System (ADS)

Engelis, Nikolaos G.; Anastasaki, Athina; Nurumbetov, Gabit; Truong, Nghia P.; Nikolaou, Vasiliki; Shegiwal, Ataulla; Whittaker, Michael R.; Davis, Thomas P.; Haddleton, David M.

2017-02-01

Translating the precise monomer sequence control achieved in nature over macromolecular structure (for example, DNA) to whole synthetic systems has been limited due to the lack of efficient synthetic methodologies. So far, chemists have only been able to synthesize monomer sequence-controlled macromolecules by means of complex, time-consuming and iterative chemical strategies such as solid-state Merrifield-type approaches or molecularly dissolved solution-phase systems. Here, we report a rapid and quantitative synthesis of sequence-controlled multiblock polymers in discrete stable nanoscale compartments via an emulsion polymerization approach in which a vinyl-terminated macromolecule is used as an efficient chain-transfer agent. This approach is environmentally friendly, fully translatable to industry and thus represents a significant advance in the development of complex macromolecule synthesis, where a high level of molecular precision or monomer sequence control confers potential for molecular targeting, recognition and biocatalysis, as well as molecular information storage.

Delta L: An Apparatus for Measuring Macromolecule Crystal Growth Rates in Microgravity

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Strongly diffracting high quality macromolecule crystals of suitable volume are keenly sought for X-ray diffraction analysis so that high-resolution molecular structure data can be obtained. Such data is of tremendous value to medical research, agriculture and commercial biotechnology. In previous studies by many investigators microgravity has been reported in some instances to improve biological macromolecule X-ray crystal quality while little or no improvement was observed in other cases. A better understanding of processes effecting crystal quality improvement in microgravity will therefore be of great benefit in optimizing crystallization success in microgravity. In ground based research with the protein lysozyme we have previously shown that a population of crystals grown under the same solution conditions, exhibit a variation in X-ray diffraction properties (Judge et al., 1999). We have also observed that under the same solution conditions, individual crystals will grow at slightly different growth rates. This phenomenon is called growth rate dispersion. For small molecule materials growth rate dispersion has been directly related to crystal quality (Cunningham et al., 1991; Ristic et al., 1991). We therefore postulate that microgravity may act to improve crystal quality by reducing growth rate dispersion. If this is the case then as different, Materials exhibit different degrees of growth rate dispersion on the ground then growth rate dispersion could be used to screen which materials may benefit the most from microgravity crystallization. In order to assess this theory the Delta L hardware is being developed so that macromolecule crystal growth rates can be measured in microgravity. Crystal growth rate is defined as the change or delta in crystal size (defined as a characteristic length, L) over time; hence the name of the hardware. Delta L will consist of an optics, a fluids, and a data acquisition sub-assemblies. The optics assembly will consist of a video microscope camera mounted on three axis computer controlled translation stages. The fluids assembly consists of macromolecule and precipitant reservoirs, a temperature controlled growth cell and waste container, The data acquisition is achieved by using a frame-gabber, with images being stored on a hard drive. In operation, macromolecule and precipitant solution will be injected into the temperature controlled growth cell. As macromolecule crystals grow, the video microscope camera controlled by the translation stages, will be used to locate and record images of individual crystals, returning to the same crystals at specific time intervals. The images will be stored on the hard drive and used to calculate the crystal growth rate. To prevent vibrations interfering in the crystal growth rate measurements (Snell et al., 1997) Delta L will be used in connection with the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) inside the Microgravity Science Glovebox (MSG), onboard the International Space Station (ISS).

Rapid surface-biostructure interaction analysis using strong metal-based nanomagnets.

PubMed

Rotzetter, Aline C C; Schumacher, Christoph M; Zako, Tamotsu; Stark, Wendelin J; Maeda, Mizuo

2013-11-19

Nanomaterials are increasingly suggested for the selective adsorption and extraction of complex compounds in biomedicine. Binding of the latter requires specific surface modifications of the nanostructures. However, even complicated macromolecules such as proteins can afford affinities toward basic surface characteristics such as hydrophobicity, topology, and electrostatic charge. In this study, we address these more basic physical interactions. In a model system, the interaction of bovine serum albumin and amyloid β 42 fibrillar aggregates with carbon-coated cobalt nanoparticles, functionalized with various polymers differing in character, was studied. The possibility of rapid magnetic separation upon binding to the surface represents a valuable tool for studying surface interactions and selectivities. We find that the surface interaction of Aβ 42 fibrillar aggregates is mostly hydrophobic in nature. Because bovine serum albumin (BSA) is conformationally adaptive, it is known to bind surfaces with widely differing properties (charge, topology, and hydrophobicity). However, the rate of tight binding (no desorption upon washing) can vary largely depending on the extent of necessary conformational changes for a specific surface. We found that BSA can only bind slowly to polyethylenimine-coated nanomagnets. Under competitive conditions (high excess BSA compared to that for β 42 fibrillar aggregates), this effect is beneficial for targeting the fibrillar species. These findings highlight the possibility of selective extractions from complex media when advantageous basic physical surface properties are chosen.

Novel materials to enhance corneal epithelial cell migration on keratoprosthesis.

PubMed

Karkhaneh, Akbar; Mirzadeh, Hamid; Ghaffariyeh, Alireza; Ebrahimi, Abdolali; Honarpisheh, Nazafarin; Hosseinzadeh, Masud; Heidari, Mohammad Hossein

2011-03-01

To introduce a new modification for silicone optical core Keratoprosthesis. Using mixtures of 2-hydroxyethyl methacrylate and acrylic acid polydimethylsiloxane (PDMS) films were modified with two-step oxygen plasma treatment, and then type I collagen was immobilised onto this modified surfaces. Both the biocompatibility of the modified films and cell behaviour on the surface of these films were investigated by in vitro tests, and formation of epithelial cell layer was evaluated by implantation of the modified films in the corneas of 10 rabbits. In vitro studies indicated that the number of attached and proliferated cells onto modified PDMS in comparison with the unmodified PDMS significantly increased. Histological studies showed that corneal epithelial cells migrated on the anterior surface of the modified films after 1week. The corneal epithelial cell formed an incomplete monolayer cellular sheet after 10days. A complete epithelialisation on the modified surface was formed after 21days. The epithelial layer persisted on the anterior surface of implant after 1-month and 3-month follow-up. This method may have potential use in silicone optical core Keratoprosthesis.

A directional entrapment modification on the polyethylene surface by the amphiphilic modifier of stearyl-alcohol poly(ethylene oxide) ether

NASA Astrophysics Data System (ADS)

Lu, Qiang; Chen, Yi; Huang, Juexin; Huang, Jian; Wang, Xiaolin; Yao, Jiaying

2018-05-01

A novel entrapment modification method involving directional implantation of the amphiphilic modifier of stearyl-alcohol poly(ethylene oxide) ether (AEO) into the high-density polyethylene (HDPE) surface is proposed. This modification technique allows the AEO modifier to be able to spontaneously attain and subsequently penetrate into the swollen HDPE surface with its hydrophobic stearyl segment, while its hydrophilic poly(ethylene oxide) (PEO) segment spontaneously points to water. The AEO modifier with a HLB number below 8.7 was proved appropriate for the directional entrapment, Nevertheless, AEOs with larger HLB numbers were also effective modifiers in the presence of salt additives. In addition, a larger and hydrophobic micelle, induced respectively by the AEO concentration above 1.3 × 10-2 mol/L and the entrapping temperature above the cloud point of AEO, could lead to a sharp contact angle decline of the modified surface. Finally, a hydrophilic HDPE surface with the modifier coverage of 38.9% was reached by the directional entrapment method, which is far larger than that of 19.2% by the traditional entrapment method.

Subunit assembly of hemoglobin: an important determinant of hematologic phenotype.

PubMed

Bunn, H F

1987-01-01

Hemoglobin's physiologic properties depend on the orderly assembly of its subunits in erythropoietic cells. The biosynthesis of alpha- and beta-globin polypeptide chains is normally balanced. Heme rapidly binds to the globin subunit, either during translation or shortly thereafter. The formation of the alpha beta-dimer is facilitated by electrostatic attraction of a positively charged alpha-subunit to a negatively charged beta-subunit. The alpha beta-dimer dissociates extremely slowly. The difference between the rate of dissociation of alpha beta- and alpha gamma-dimers with increasing pH explains the well-known alkaline resistance of Hb F. Two dimers combine to form the functioning alpha 2 beta 2-tetramer. This model of hemoglobin assembly explains the different levels of positively charged and negatively charged mutant hemoglobins that are encountered in heterozygotes and the effect of alpha-thalassemia and heme deficiency states in modifying the level of the variant hemoglobin as well as Hb A2. Electrostatic interactions also affect the binding of hemoglobin to the cytoplasmic surface of the red cell membrane and may underlie the formation of target cells. Enhanced binding of positively charged variants such as S and C trigger a normally dormant pathway for potassium and water loss. Thus, the positive charge on beta c is responsible for the two major contributors to the pathogenesis of Hb SC disease: increased proportion of Hb S and increased intracellular hemoglobin concentration. It is likely that electrostatic interactions play an important role in the assembly of a number of other multisubunit macromolecules, including membrane receptors, cytoskeletal proteins, and DNA binding proteins.

Deformation sensor based on polymer-supported discontinuous graphene multi-layer coatings

NASA Astrophysics Data System (ADS)

Carotenuto, G.; Schiavo, L.; Romeo, V.; Nicolais, L.

2014-05-01

Graphene can be conveniently used in the modification of polymer surfaces. Graphene macromolecules are perfectly transparent to the visible light and electrically conductive, consequently these two properties can be simultaneously provided to polymeric substrates by surface coating with thin graphene layers. In addition, such coating process provides the substrates of: water-repellence, higher surface hardness, low-friction, self-lubrication, gas-barrier properties, and many other functionalities. Polyolefins have a non-polar nature and therefore graphene strongly sticks on their surface. Nano-crystalline graphite can be used as graphene precursor in some chemical processes (e.g., graphite oxide synthesis by the Hummer method), in addition it can be directly applied to the surface of a polyolefin substrate (e.g., polyethylene) to cover it by a thin graphene multilayer. In particular, the nano-crystalline graphite perfectly exfoliate under the application of a combination of shear and friction forces and the produced graphene single-layers perfectly spread and adhere on the polyethylene substrate surface. Such polymeric materials can be used as ITO (indium-tin oxide) substitute and in the fabrication of different electronic devices. Here the fabrication of transparent resistive deformation sensors based on low-density polyethylene films coated by graphene multilayers is described. Such devices are very sensible and show a high reversible and reproducible behavior.

Interaction of fullerene (C60) nanoparticles with humic acid and alginate coated silica surfaces: measurements, mechanisms, and environmental implications.

PubMed

Chen, Kai Loon; Elimelech, Menachem

2008-10-15

The deposition kinetics of fullerene (C60) nanoparticles onto bare silica surfaces and surfaces precoated with humic acid and alginate are investigated over a range of monovalent (NaCI) and divalent (CaCl2) salt concentrations using a quartz crystal microbalance. Because simultaneous aggregation of the fullerene nanoparticles occurs, especially at higher electrolyte concentrations, we normalize the observed deposition rates by the corresponding favorable (transport-limited) deposition rates to obtain the attachment efficiencies, alpha. The deposition kinetics of fullerene nanoparticles onto bare silica surfaces are shown to be controlled by electrostatic interactions and van der Waals attraction, consistent with the classical particle deposition behavior where both favorable and unfavorable deposition regimes are observed. The presence of dissolved humic acid and alginate in solution leads to significantly slower deposition kinetics due to steric repulsion. Precoating the silica surfaces with humic acid and alginate exerts similar steric stabilization in the presence of NaCl. In the presence of CaCl2, the deposition kinetics of fullerene nanoparticles onto both humic acid- and alginate-coated surfaces are relatively high, even at relatively low (0.3 mM) calcium concentration. This behavior is attributed to the macromolecules undergoing complex formation with calcium ions, which reduces the charge and steric influences of the adsorbed macromolecular layers.

Strongly Phase-Segregating Block Copolymers with Sub-20 nm Features

DTIC Science & Technology

2013-07-19

PERSON 19b. TELEPHONE NUMBER Francis Doyle Kristian Kempe, Kato L. Killops, Justin E. Poelma, Hyunjung Jung, Joona Bang, Richard Hoogenboom , Helen...Hyunjung Jung,# Joona Bang,# Richard Hoogenboom ,▽ Helen Tran,○ Craig J. Hawker,*,∥,¶ Ulrich S. Schubert,*,†,‡,◆ and Luis M. Campos*,○ †Laboratory of Organic...Macromolecules 2011, 44, 5825. (30) Wiesbrock, F.; Hoogenboom , R.; Leenen, M. A. M.; Meier, M. A. R.; Schubert, U. S. Macromolecules 2005, 38, 5025

Thermally Cross-Linked Anion Exchange Membranes from Solvent Processable Isoprene Containing Ionomers

DTIC Science & Technology

2015-01-15

isoprene determined by 1H NMR of each copolymer. Hydration Macromolecules Article DOI: 10.1021/ma502362a Macromolecules XXXX, XXX, XXX−XXX B number (λ) is...C. This is attributed to the decomposition of the TMA groups. Slight weight loss at lower temperatures is presumably due to the loss of trapped water...that at sufficiently high hydration levels the diffusion coefficient of ions approach their dilute solution diffusivity limits.30 Since conductivity is

Surface-modified Ba(Zr0.3Ti0.7)O3 nanofibers by polyvinylpyrrolidone filler for poly(vinylidene fluoride) composites with enhanced dielectric constant and energy storage density.

PubMed

Liu, Shaohui; Xue, Shuangxi; Xiu, Shaomei; Shen, Bo; Zhai, Jiwei

2016-05-17

Ferroelectric-relaxor behavior of Ba(Zr0.3Ti0.7)O3 nanofibers (BZT NF) with a large aspect ratio were prepared via electrospinning and surface modified by PVP as dielectric fillers. The nanocomposite flexible films based on surface modified BZT NF and polyvinylidene fluoride (PVDF) were fabricated via a solution casting. The results show that the surface-modified BZT NF fillers are highly dispersed and well integrated in the PVDF nanocomposites. The nanocomposites exhibit enhanced dielectric constant and reduced loss tangents at a low volume fraction of surface-modified BZT NF. The polymer nanocomposites maintain a relatively high breakdown strength, which is favorable for enhancing energy storage density in the nanocomposites. The nanocomposite containing of 2.5 vol. % of PVP modified BZT NF exhibits energy density as high as 6.3 J/cm(3) at 3800 kV/cm, which is more than doubled that of the pure PVDF of 2.8 J/cm(3) at 4000 kV/cm. Such significant enhancement could be attributed to the combined effects of the surface modification and large aspect ratio of the BZT NF. This work may provide a route for using the surface modified ferroelectric-relaxor behavior of ceramic nanofibers to enhance the dielectric energy density in ceramic-polymer nanocomposites.

Higher modulus compositions incorporating particulate rubber

DOEpatents

Bauman, Bernard D.; Williams, Mark A.

1999-01-01

A plastic article having a number of surfaces with at least one surface being modified by contacting that surface with a reactive gas atmosphere containing F.sub.2, Cl.sub.2, O.sub.2, Ozone, SO.sub.3, oxidative acids, or mixtures thereof, at a temperature and gas partial pressure sufficient to increase the surface energy of the at least one surface being modified to at least 40 dynes/cm at a temperature of 20.degree. C., to enhance bonding of non-slip polymer coatings to the modified surface, to which coatings elastomeric or rigid particles may be admixed for imparting a surface profile and increasing the coefficient of friction between the coated surface and the counter-surface.

Membrane-active macromolecules kill antibiotic-tolerant bacteria and potentiate antibiotics towards Gram-negative bacteria

PubMed Central

Uppu, Divakara S. S. M.; Konai, Mohini M.; Sarkar, Paramita; Samaddar, Sandip; Fensterseifer, Isabel C. M.; Farias-Junior, Celio; Krishnamoorthy, Paramanandam; Shome, Bibek R.; Franco, Octávio L.

2017-01-01

Chronic bacterial biofilms place a massive burden on healthcare due to the presence of antibiotic-tolerant dormant bacteria. Some of the conventional antibiotics such as erythromycin, vancomycin, linezolid, rifampicin etc. are inherently ineffective against Gram-negative bacteria, particularly in their biofilms. Here, we report membrane-active macromolecules that kill slow dividing stationary-phase and antibiotic tolerant cells of Gram-negative bacteria. More importantly, these molecules potentiate antibiotics (erythromycin and rifampicin) to biofilms of Gram-negative bacteria. These molecules eliminate planktonic bacteria that are liberated after dispersion of biofilms (dispersed cells). The membrane-active mechanism of these molecules forms the key for potentiating the established antibiotics. Further, we demonstrate that the combination of macromolecules and antibiotics significantly reduces bacterial burden in mouse burn and surgical wound infection models caused by Acinetobacter baumannii and Carbapenemase producing Klebsiella pneumoniae (KPC) clinical isolate respectively. Colistin, a well-known antibiotic targeting the lipopolysaccharide (LPS) of Gram-negative bacteria fails to kill antibiotic tolerant cells and dispersed cells (from biofilms) and bacteria develop resistance to it. On the contrary, these macromolecules prevent or delay the development of bacterial resistance to known antibiotics. Our findings emphasize the potential of targeting the bacterial membrane in antibiotic potentiation for disruption of biofilms and suggest a promising strategy towards developing therapies for topical treatment of Gram-negative infections. PMID:28837596

A natural and readily available crowding agent: NMR studies of proteins in hen egg white.

PubMed

Martorell, Gabriel; Adrover, Miquel; Kelly, Geoff; Temussi, Piero Andrea; Pastore, Annalisa

2011-05-01

In vitro studies of biological macromolecules are usually performed in dilute, buffered solutions containing one or just a few different biological macromolecules. Under these conditions, the interactions among molecules are diffusion limited. On the contrary, in living systems, macromolecules of a given type are surrounded by many others, at very high total concentrations. In the last few years, there has been an increasing effort to study biological macromolecules directly in natural crowded environments, as in intact bacterial cells or by mimicking natural crowding by adding proteins, polysaccharides, or even synthetic polymers. Here, we propose the use of hen egg white (HEW) as a simple natural medium, with all features of the media of crowded cells, that could be used by any researcher without difficulty and inexpensively. We present a study of the stability and dynamics behavior of model proteins in HEW, chosen as a prototypical, readily accessible natural medium that can mimic cytosol. We show that two typical globular proteins, dissolved in HEW, give NMR spectra very similar to those obtained in dilute buffers, although dynamic parameters are clearly affected by the crowded medium. The thermal stability of one of these proteins, measured in a range comprising both heat and cold denaturation, is also similar to that in buffer. Our data open new possibilities to the study of proteins in natural crowded media. Copyright © 2010 Wiley-Liss, Inc.

Sorption of nonpolar aromatic contaminants by chlorosilane surface modified natural minerals.

PubMed

Huttenloch, P; Roehl, K E; Czurda, K

2001-11-01

The efficacy of the surface modification of natural diatomite and zeolite material by chlorosilanes is demonstrated. Chlorosilanes used were trimethylchlorosilane (TMSCI), tert-butyldimethylchlorosilane (TBDMSCI), dimethyloctadecylchlorosilane (DMODSCI), and diphenyldichlorosilane (DPDSCI) possessing different headgroups and chemical properties. Silanol groups of the diatomite and zeolite were modified by chemical reaction with the chlorosilanes resulting in a stable covalent attachment of the organosilanes to the mineral surface. The alteration of surface properties of the modified material was proved by measurements of water adsorption capacity, total organic carbon (TOC) content, and thermoanalytical data. The surface modified material showed great stability even when exposed to extremes in ionic strength, pH, and to pure organic solvents. Sorption of toluene, o-xylene, and naphthalene from water was greatly enhanced by the surface modification compared to the untreated materials which showed no measurable sorption of these compounds. The enhanced sorption was dependent on the organic carbon content as well as on chemical characteristics of the chlorosilanes used. Batch sorption experiments showed that the phenyl headgroups of DPDSCI have the best affinity for aromatic compounds. Removal from an aqueous solution of 10 mg/L of naphthalene, o-xylene, and toluene was 71%, 60%, and 30% for surface modified diatomite and 51%, 30%, and 16% for modified clinoptilolite, respectively. Sorption data were well described by the Freundlich isotherm equation, which indicated physical adsorption onto the lipophilic surface rather than partitioning into the surface organic phase. The chlorosilane modified materials have an apparent potential for application in environmental technologies such as permeable reactive barriers (PRB) or wastewater treatment.

A single-step aerosol process for in-situ surface modification of nanoparticles: Preparation of stable aqueous nanoparticle suspensions.

PubMed

Sapra, Mahak; Pawar, Amol Ashok; Venkataraman, Chandra

2016-02-15

Surface modification of nanoparticles during aerosol or gas-phase synthesis, followed by direct transfer into liquid media can be used to produce stable water-dispersed nanoparticle suspensions. This work investigates a single-step, aerosol process for in-situ surface-modification of nanoparticles. Previous studies have used a two-step sublimation-condensation mechanism following droplet drying, for surface modification, while the present process uses a liquid precursor containing two solutes, a matrix lipid and a surface modifying agent. A precursor solution in chloroform, of stearic acid lipid, with 4 %w/w of surface-active, physiological molecules [1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol)-sodium salt (DPPG) or 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol) 2000]-ammonium salt (DPPE-PEG)] was processed in an aerosol reactor at a low gas temperatures. The surface modified nanoparticles were characterized for morphology, surface composition and suspension properties. Spherical, surface-modified lipid nanoparticles with median mobility diameters in the range of 105-150nm and unimodal size distributions were obtained. Fourier transform infra-red spectroscopy (FTIR) measurements confirmed the presence of surface-active molecules on external surfaces of modified lipid nanoparticles. Surface modified nanoparticles exhibited improved suspension stability, compared to that of pure lipid nanoparticles for a period of 30days. Lowest aggregation was observed in DPPE-PEG modified nanoparticles from combined electrostatic and steric effects. The study provides a single-step aerosol method for in-situ surface modification of nanoparticles, using minimal amounts of surface active agents, to make stable, aqueous nanoparticle suspensions. Copyright © 2015 Elsevier Inc. All rights reserved.

Fabrication of a novel biosensor for macromolecules detection through molecular imprinting technique

NASA Astrophysics Data System (ADS)

Yu, Yingjie

There is an increasing need for precise molecular detection as a diagnostic tool for early identification of diseases, pathogens, and abnormal protein levels in the body. Typical chemical analytical methods are generally costly, unstable, and time-consuming. Molecular imprinting (MI) technique, based on the "lock and key model", could be a simple method to overcome those shortcomings. In this study, a self-assembled monolayer (SAM) was employed as a platform to fabricate MI biosensor for detection of macromolecules. I demonstrated that, when the monolayer was formed on a rough surface, this method was in fact templating molecules in three dimensions, and hence was not limited by the height of the monolayer, but rather by the height of the roughness. This hypothesis was tested on biomolecules of multiple length scales. The SAM is assembled on the walls of the niche, forming a 3D pattern of the analyte uniquely molded to its contour. The surfaces with multi-scale roughness were prepared by evaporation of gold onto electropolished (smooth) and unpolished (rough) Si wafers, where the native roughness was found to have a normal distribution centered around 5 and 90 nm respectively. Our studies, using molecules, such as proteins, i.e., hemoglobin, ranging from a few nanometers, to viruses (i.e. polio, adenovirus), ranging from several tens of nanometers, and protein complexes ranging from several hundred nanometers, showed that when the size of the analyte matched the roughness of the gold surface, this method was very effective and could detect even small changes in the configuration, such as those induced by changes in the pH of the system. The detection method was further quantified by applying it to the detection of CEA in pancreatic cyst fluid obtained from 18 patients under IRB 95867-6. The results of the MI biosensor were directly compared with those obtained using ELISA in the hospital pathology laboratory with excellent agreement, except that the MI biosensor used only 1% of the volume of the ELISA test and produced results in less than 5 minutes, as compared to at least 10 hours.

One-pot reaction for the preparation of biofunctionalized self-assembled monolayers on gold surfaces

NASA Astrophysics Data System (ADS)

Raigoza, Annette F.; Fies, Whitney; Lim, Amber; Onyirioha, Kristeen; Webb, Lauren J.

2017-02-01

The Huisgen cycloaddition reaction (;click; chemistry) has been used extensively to functionalize surfaces with macromolecules in a straightforward manner. We have previously developed a procedure using the copper(I)-catalyzed click reaction to tether synthetic α-helical peptides carrying two alkyne groups to a well-ordered azide-terminated alkanethiol self-assembled monolayer (SAM) on a Au(111) surface. While convenient, click-based strategies potentially pose significant problems from reagents, solvents, and reaction temperatures that may irreversibly damage some molecules or substrates. Tuning click chemistry conditions would allow individual optimization of reaction conditions for a wide variety of biomolecules and substrate materials. Here, we explore the utility of simultaneous SAM formation and peptide-attachment chemistry in a one-pot reaction. We demonstrate that a formerly multistep reaction can be successfully carried out concurrently by mixing azide-terminated alkanethiols, CuCl, and a propargylglycine-containing peptide over a bare gold surface in ethanol and reacting at 70 °C. X-ray photoelectron spectroscopy (XPS), surface infrared spectroscopy, surface circular dichroic (CD) spectroscopy, and scanning tunneling microscopy (STM) were used to determine that this one-pot reaction strategy resulted in a high density of surface-bound α-helices without aggregation. This work demonstrates the simplicity and versatility of a SAM-plus-click chemistry strategy for functionalizing Au surfaces with structured biomolecules.

Protecting the surface of a light absorber in a photoanode

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

Hu, Shu; Lewis, Nathan S.

A photoanode includes a passivation layer on a light absorber. The passivation layer is more resistant to corrosion than the light absorber. The photoanode includes a surface modifying layer that is location on the passivation layer such that the passivation layer is between the light absorber and the surface modifying layer. The surface modifying layer reduces a resistance of the passivation layer to conduction of holes out of the passivation layer.

PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes.

PubMed

Nady, Norhan

2016-04-18

A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled "green surface modification". This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers-ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)-is presented.

Sustained release and permeation of timolol from surface-modified solid lipid nanoparticles through bioengineered human cornea.

PubMed

Attama, A A; Reichl, S; Müller-Goymann, C C

2009-08-01

The aim of the study was to formulate and evaluate surface-modified solid lipid nanoparticles sustained delivery system of timolol hydrogen maleate, a prototype ocular drug using a human cornea construct. Surface-modified solid lipid nanoparticles containing timolol with and without phospholipid were formulated by melt emulsification with high-pressure homogenization and characterized by particle size, wide-angle X-ray diffraction, encapsulation efficiency, and in vitro drug release. Drug transport studies through cornea bioengineered from human donor cornea cells were carried out using a modified Franz diffusion cell and drug concentration analyzed by high-performance liquid chromatography. Results show that surface-modified solid lipid nanoparticles possessed very small particles (42.9 +/- 0.3 nm, 47.2 +/- 0.3 nm, 42.7 +/- 0.7 nm, and 37.7 +/- 0.3 nm, respectively for SM-SLN 1, SM-SLN 2, SM-SLN 3, and SM-SLN 4) with low polydispersity indices, increased encapsulation efficiency (> 44%), and sustained in vitro release compared with unmodified lipid nanoparticles whose particles were greater than 160 nm. Permeation of timolol hydrogen maleate from the surface-modified lipid nanoparticles across the cornea construct was sustained compared with timolol hydrogen maleate solution in distilled water. Surface-modified solid lipid nanoparticles could provide an efficient way of improving ocular bioavailability of timolol hydrogen maleate.

Interactions of Nitroxide-Conjugated and Non-Conjugated Glycodendrimers with Normal and Cancer Cells and Biocompatibility Studies.

PubMed

Andreozzi, Elisa; Antonelli, Antonella; Cangiotti, Michela; Canonico, Barbara; Sfara, Carla; Pianetti, Anna; Bruscolini, Francesca; Sahre, Karin; Appelhans, Dietmar; Papa, Stefano; Ottaviani, Maria Francesca

2017-02-15

Poly(propyleneimine) glycodendrimers fully modified with maltose units were administered to different cancer cell lines and their effect on cell viability was evaluated by using MTS assay and flow cytometry. The mechanism of dendrimer-cell interactions was investigated by the electron paramagnetic resonance (EPR) technique by using a new nitroxide-conjugated glycodendrimer. The nitroxide groups did not modify both the biological properties (cell viability and apoptosis degree) of the dendrimers in the presence of the cells and the dendrimer-cell interactions. Since this class of dendrimers is already known to be biocompatible for human healthy cells, noncancer cells such as human peripheral blood mononuclear cells (PBMCs) and macrophages were also treated with the glycodendrimer, and EPR spectra of the nitroxide-conjugated glycodendrimer were compared for cancer and noncancer cells. It was found that this dendrimer selectively affects the cell viability of tumor cells, while, surprisingly, PBMC proliferation is induced. Moreover, H-bond-active glycodendrimer-cell interactions were different for the different cancer cell lines and noncancer cells. The nitroxide-conjugated glycodendrimer was able to interact with the cell membrane and eventually cross it, getting in contact with cytosol antioxidants. This study helps to clarify the potential anticancer effect of this class of dendrimers opening to future applications of these macromolecules as new antitumor agents.

Smectite flocculation structure modified by Al13 macro-molecules--as revealed by the transmission X-ray microscopy (TXM).

PubMed

Zbik, Marek S; Martens, Wayde N; Frost, Ray L; Song, Yen-Fang; Chen, Yi-Ming; Chen, Jian-Hua

2010-05-01

The aggregate structure which occurs in aqueous smectitic suspensions is responsible for poor water clarification, difficulties in sludge dewatering and the unusual rheological behaviour of smectite rich soils. These macroscopic properties are dictated by the 3D structural arrangement of smectite finest fraction within flocculated aggregates. Here, we report results from a relatively new technique, transmission X-ray microscopy (TXM), which makes it possible to investigate the internal structure and 3D tomographic reconstruction of the smectite clay aggregates modified by Al(13) Keggin macro-molecule [Al(13)(O)(4)(OH)(24)(H(2)O)(12)](7+). Three different treatment methods were shown resulted in three different micro-structural environments of the resulting flocculation. In case of smectite sample prepared in Methods 1 and 3 particles fall into the primary minimum where Van der Waals forces act between FF oriented smectite flakes and aggregates become approach irreversible flocculation. In case of sample prepared using Method 2, particles contacting by edges (EE) and edge to face (EF) orientation fell into secondary minimum and weak flocculation resulted in severe gelation and formation of the micelle-like texture in fringe superstructure, which was first time observed in smectite based gel. Copyright 2010 Elsevier Inc. All rights reserved.

Combining Graphical and Analytical Methods with Molecular Simulations To Analyze Time-Resolved FRET Measurements of Labeled Macromolecules Accurately

PubMed Central

2017-01-01

Förster resonance energy transfer (FRET) measurements from a donor, D, to an acceptor, A, fluorophore are frequently used in vitro and in live cells to reveal information on the structure and dynamics of DA labeled macromolecules. Accurate descriptions of FRET measurements by molecular models are complicated because the fluorophores are usually coupled to the macromolecule via flexible long linkers allowing for diffusional exchange between multiple states with different fluorescence properties caused by distinct environmental quenching, dye mobilities, and variable DA distances. It is often assumed for the analysis of fluorescence intensity decays that DA distances and D quenching are uncorrelated (homogeneous quenching by FRET) and that the exchange between distinct fluorophore states is slow (quasistatic). This allows us to introduce the FRET-induced donor decay, εD(t), a function solely depending on the species fraction distribution of the rate constants of energy transfer by FRET, for a convenient joint analysis of fluorescence decays of FRET and reference samples by integrated graphical and analytical procedures. Additionally, we developed a simulation toolkit to model dye diffusion, fluorescence quenching by the protein surface, and FRET. A benchmark study with simulated fluorescence decays of 500 protein structures demonstrates that the quasistatic homogeneous model works very well and recovers for single conformations the average DA distances with an accuracy of < 2%. For more complex cases, where proteins adopt multiple conformations with significantly different dye environments (heterogeneous case), we introduce a general analysis framework and evaluate its power in resolving heterogeneities in DA distances. The developed fast simulation methods, relying on Brownian dynamics of a coarse-grained dye in its sterically accessible volume, allow us to incorporate structural information in the decay analysis for heterogeneous cases by relating dye states with protein conformations to pave the way for fluorescence and FRET-based dynamic structural biology. Finally, we present theories and simulations to assess the accuracy and precision of steady-state and time-resolved FRET measurements in resolving DA distances on the single-molecule and ensemble level and provide a rigorous framework for estimating approximation, systematic, and statistical errors. PMID:28709377

REGULATION OF COAL POLYMER DEGRADATION BY FUNGI

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

John A. Bumpus

1998-11-30

A variety of lignin degrading fungi mediate solubilization and subsequent biodegradation of coal macromolecules (a.k.a. coal polymer) from highly oxidized low rank coals such as leonardites. It appears that oxalate or possibly other metal chelators (i.e., certain Krebs Cycle intermediates) mediate solubilization of low rank coals while extracellular oxidases have a role in subsequent oxidation of solubilized coal macromolecule. These processes are under nutritional control. For example, in the case of P. chrysosporium, solubilization of leonardite occurred when the fungi were cultured on most but not all nutrient agars tested and subsequent biodegradation occurred only in nutrient nitrogen limited cultures.more » Lignin peroxidases mediate oxidation of coal macromolecule in a reaction that is dependent on the presence of veratryl alcohol and hydrogen peroxide. Kinetic evidence suggests that veratryl alcohol is oxidized to the veratryl alcohol cation radical which then mediates oxidation of the coal macromolecule. Results by others suggest that Mn peroxidases mediate formation of reactive Mn{sup 3+} complexes which also mediate oxidation of coal macromolecule. A biomimetic approach was used to study solubilization of a North Dakota leonardite. It was found that a concentration {approximately}75 mM sodium oxalate was optimal for solubilization of this low rank coal. This is important because this is well above the concentration of oxalate produced by fungi in liquid culture. Higher local concentrations probably occur in solid agar cultures and thus may account for the observation that greater solubilization occurs in agar media relative to liquid media. The characteristics of biomimetically solubilized leonardite were similar to those of biologically solubilized leonardite. Perhaps our most interesting observation was that in addition to oxalate, other common Lewis bases (phosphate/hydrogen phosphate/dihydrogen phosphate and bicarbonate/carbonate ions) are able to mediate substantial solubilization of leonardite at physiological pH values. Lastly, we present evidence that some fungi appear to possess coal solubilization ability in which the initial events of solubilization is not mediated by oxalate ion.« less

Method of making gold thiolate and photochemically functionalized microcantilevers

DOEpatents

Boiadjiev, Vassil I [Knoxville, TN; Brown, Gilbert M [Knoxville, TN; Pinnaduwage, Lal A [Knoxville, TN; Thundat, Thomas G [Knoxville, TN; Bonnesen, Peter V [Knoxville, TN; Goretzki, Gudrun [Nottingham, GB

2009-08-25

Highly sensitive sensor platforms for the detection of specific reagents, such as chromate, gasoline and biological species, using microcantilevers and other microelectromechanical systems (MEMS) whose surfaces have been modified with photochemically attached organic monolayers, such as self-assembled monolayers (SAM), or gold-thiol surface linkage are taught. The microcantilever sensors use photochemical hydrosilylation to modify silicon surfaces and gold-thiol chemistry to modify metallic surfaces thereby enabling individual microcantilevers in multicantilever array chips to be modified separately. Terminal vinyl substituted hydrocarbons with a variety of molecular recognition sites can be attached to the surface of silicon via the photochemical hydrosilylation process. By focusing the activating UV light sequentially on selected silicon or silicon nitride hydrogen terminated surfaces and soaking or spotting selected metallic surfaces with organic thiols, sulfides, or disulfides, the microcantilevers are functionalized. The device and photochemical method are intended to be integrated into systems for detecting specific agents including chromate groundwater contamination, gasoline, and biological species.

Fiber Surface Modification Technology for Fiber-Optic Localized Surface Plasmon Resonance Biosensors

PubMed Central

Zhang, Qiang; Xue, Chenyang; Yuan, Yanling; Lee, Junyang; Sun, Dong; Xiong, Jijun

2012-01-01

Considerable studies have been performed on the development of optical fiber sensors modified by gold nanoparticles based on the localized surface plasmon resonance (LSPR) technique. The current paper presents a new approach in fiber surface modification technology for biosensors. Star-shaped gold nanoparticles obtained through the seed-mediated solution growth method were found to self-assemble on the surface of tapered optical fibers via amino- and mercapto-silane coupling agents. Transmitted power spectra of 3-aminopropyltrimethoxy silane (APTMS)-modified fiber were obtained, which can verify that the silane coupling agent surface modification method is successful. Transmission spectra are characterized in different concentrations of ethanol and gentian violet solutions to validate the sensitivity of the modified fiber. Assembly using star-shaped gold nanoparticles and amino/mercapto silane coupling agent are analyzed and compared. The transmission spectra of the gold nanoparticles show that the nanoparticles are sensitive to the dielectric properties of the surrounding medium. After the fibers are treated in t-dodecylmercaptan to obtain their transmission spectra, APTMS-modified fiber becomes less sensitive to different media, except that modified by 3-mercaptopropyltrimethoxy silane (MPTMS). Experimental results of the transmission spectra show that the surface modified by the gold nanoparticles using MPTMS is firmer compared to that obtained using APTMS. PMID:22736974

Method of generating a surface mesh

DOEpatents

Shepherd, Jason F [Albuquerque, NM; Benzley, Steven [Provo, UT; Grover, Benjamin T [Tracy, CA

2008-03-04

A method and machine-readable medium provide a technique to generate and modify a quadrilateral finite element surface mesh using dual creation and modification. After generating a dual of a surface (mesh), a predetermined algorithm may be followed to generate and modify a surface mesh of quadrilateral elements. The predetermined algorithm may include the steps of generating two-dimensional cell regions in dual space, determining existing nodes in primal space, generating new nodes in the dual space, and connecting nodes to form the quadrilateral elements (faces) for the generated and modifiable surface mesh.

Digital X-ray camera for quality evaluation three-dimensional topographic reconstruction of single crystals of biological macromolecules

NASA Technical Reports Server (NTRS)

Borgstahl, Gloria (Inventor); Lovelace, Jeff (Inventor); Snell, Edward Holmes (Inventor); Bellamy, Henry (Inventor)

2008-01-01

The present invention provides a digital topography imaging system for determining the crystalline structure of a biological macromolecule, wherein the system employs a charge coupled device (CCD) camera with antiblooming circuitry to directly convert x-ray signals to electrical signals without the use of phosphor and measures reflection profiles from the x-ray emitting source after x-rays are passed through a sample. Methods for using said system are also provided.

Basal-body-associated macromolecules: a continuing debate.

PubMed

Pierre Mignot, J; Brugerolle, G; Didier, P; Bornens, M

1993-07-01

Controversy over the possibility that centrioles/basal bodies contain nucleic acids has overshadowed results demonstrating other macromolecules in the lumen of these organelles. Glycogen particles, which are known to be present within the lumen of the centriole/basal body of sperm cells, have now been found in basal bodies of protists belonging to three different groups. Here, we extend the debate on a role for RNA in basal body/centriole function and speculate on the origin and the function of centriolar glycogen.

Growing Hyperbranched Polymers Using Natural Sunlight

PubMed Central

Yan, Jun-Jie; Sun, Jiao-Tong; You, Ye-Zi; Wu, De-Cheng; Hong, Chun-Yan

2013-01-01

In nature, a sapling can grow into a big tree under irradiation of sunlight. In chemistry, a similar concept that a small molecule only exposing to sunlight grows into a hyperbranched macromolecule has not been realized by now. The achievement of the concept will be fascinating and valuable for polymer synthesis wherein sunlight is inexpensive, abundant, renewable, and nonpolluting. Herein, we report a new strategy in which small monomers can directly grow into big hyperbranched macromolecule under irradiation of sunlight without any catalyst. PMID:24100948

Investigation of follicular and non-follicular pathways for polyarginine and oleic acid modified nanoparticles

PubMed Central

Hayden, Patrick; Singh, Mandip

2013-01-01

Purpose The aim of the current study was to investigate the percutaneous permeation pathways of cell penetrating peptide modified lipid nanoparticles and oleic acid modified polymeric nanoparticles. Methods Confocal microscopy was performed on skin cultures (EpiDermFT™) for modified and un-modified nanoparticles. Differential stripping was performed following in vitro skin permeation of Ibuprofen (Ibu) encapsulated nanoparticles to estimate Ibu levels in different skin layers and receiver compartment. The hair follicles (HF) were blocked and in vitro skin permeation of nanoparticles was then compared with unblocked HF. The surface modified nanoparticles were investigated for response on allergic contact dermatitis (ACD). Results Surface modified nanoparticles showed a significant higher (p < 0.05) in fluorescence in EpiDermFT™ cultures compared to controls. The HF play less than 5% role in total nanoparticle permeation into the skin. The Ibu levels were significantly high (p<0.05) for surface modified nanoparticles compared to controls. The Ibu levels in skin and receiver compartment were not significantly different when HF were open or closed. Modified nanoparticles showed significant improvement in treatment of ACD compared to solution. Conclusions Our studies demonstrate that increased skin permeation of surface modified nanoparticles is not only dependent on a follicular pathway but also occur through non-follicular pathway(s). PMID:23187866

On thermophysical effects on the surface of functional nanostructured materials obtained with the application of femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Babenko, D. D.; Dmitriev, A. S.; Makarov, P. G.; Mikhailova, I. A.

2017-11-01

In recent years, a great scientific and practical interest is caused by functional energy surfaces, modified for certain technological problems. The urgency of the work is to develop promising technologies for thermal and nuclear power engineering, methods for converting solar energy, cooling low-current and high-current electronics devices, energy storage and transport systems on the basis of studying and developing new ways of creating and modifying the functional surfaces of heat exchange and other devices. Modified functional surfaces must have a number of new mechanical and thermophysical properties, including mechanical strength, a new surface morphology for controlling the processes of wetting and spreading working fluids on them, and have high efficiency from the viewpoint of thermohydrodynamic processes of flow and heat and mass transfer of working fluids to them. Among the various ways of modifying surfaces, recently, the method of surface exposure to femtosecond laser pulses (FLI) has become widespread. The technology of femtosecond laser surface treatment (FLPO) of solid materials has shown high efficiency, reliability, high productivity and a huge variety of modification methods. The paper presents new results on the study of thermophysical phenomena - the wetting and spreading of drops of various liquids, the study of the hysteresis of the contact angle, the study of evaporation and boiling processes on functional energy surfaces modified by femtosecond laser pulses. It is shown that in the majority of cases the presence of regular or stochastic nanostructures on the surface leads to a very strong change in the basic properties of the surface, which makes it possible to use such a technology to quickly and efficiently modify and obtain functional energy surfaces for certain predetermined purposes.

Designing Pulse Laser Surface Modification of H13 Steel Using Response Surface Method

NASA Astrophysics Data System (ADS)

Aqida, S. N.; Brabazon, D.; Naher, S.

2011-01-01

This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 μm and 150 μm. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 μm. The maximum hardness achieved was between 728 and 905 HV0.1. These findings are significant to modern development of hard coatings for wear resistant applications.

Chitosan: A macromolecule as green corrosion inhibitor for mild steel in sulfamic acid useful for sugar industry.

PubMed

Gupta, Neeraj Kumar; Joshi, P G; Srivastava, Vandana; Quraishi, M A

2018-01-01

The present investigation aims at investigation of low cost nontoxic carbohydrate biopolymer chitosan as corrosion inhibitor alone and in combination with KI for mild steel in 1M sulfamic acid medium using gravimetric, electrochemical and surface analysis techniques. It is found that chitosan alone exhibits inhibition efficiency of 73.8% at 200ppm concentration. However, in combination with KI (5ppm), it gave more than 90% inhibition efficiency. The significant increase in the inhibition performance of chitosan has been explained by the synergistic mechanism. The results of Potentiodynamic polarization study shows that chitosan and its blend with KI decreases both anodic and cathodic reactions occurring at mild steel surface in 1M sulfamic acid medium by blocking active sites of the metal and acts as mixed type inhibitor. EIS study reveals that the polarization resistance increases with increase in the concentration of inhibitors which increases charge transfer resistance across the metal/solution interface. The adsorption of chitosan followed the Langmuir adsorption isotherm. The formation of inhibitor film on metal surface was supported by scanning electron microscopy (SEM) and atomic force microscopy (AFM) surface studies. Copyright © 2017 Elsevier B.V. All rights reserved.

A bio-recognition device developed onto nano-crystals of carbonate apatite for cell-targeted gene delivery.

PubMed

Chowdhury, E H; Akaike, Toshihiro

2005-05-20

The DNA delivery to mammalian cells is an essential tool for analyzing gene structure, regulation, and function. The approach holds great promise for the further development of gene therapy techniques and DNA vaccination strategies to treat and control diseases. Here, we report on the establishment of a cell-specific gene delivery and expression system by physical adsorption of a cell-recognition molecule on the nano-crystal surface of carbonate apatite. As a model, DNA/nano-particles were successfully coated with asialofetuin to facilitate uptake by hepatocyte-derived cell lines through the asialoglycoprotein receptor (ASGPr) and albumin to prevent non-specific interactions of the particles with cell-surface. The resulting composite particles with dual surface properties could accelerate DNA uptake and enhance expression to a notable extent. Nano-particles coated with transferrin in the same manner dramatically enhanced transgene expression in the corresponding receptor-bearing cells and thus our newly developed strategy represents a universal phenomenon for anchoring a bio-recognition macromolecule on the apatite crystal surface for targeted gene delivery, having immediate applications in basic research laboratories and great promise for gene therapy. (c) 2005 Wiley Periodicals, Inc.

Chelating ligands for nanocrystals' surface functionalization.

PubMed

Querner, Claudia; Reiss, Peter; Bleuse, Joël; Pron, Adam

2004-09-22

A new family of ligands for the surface functionalization of CdSe nanocrystals is proposed, namely alkyl or aryl derivatives of carbodithioic acids (R-C(S)SH). The main advantages of these new ligands are as follows: they nearly quantitatively exchange the initial surface ligands (TOPO) in very mild conditions; they significantly improve the resistance of nanocrystals against photooxidation because of their ability of strong chelate-type binding to metal atoms; their relatively simple preparation via Grignard intermediates facilitates the development of new bifunctional ligands containing, in addition to the anchoring carbodithioate group, a second function, which enables the grafting of molecules or macromolecules of interest on the nanocrystal surface. To give an example of this approach, we report, for the first time, the grafting of an electroactive oligomer from the polyaniline family-aniline tetramer-on CdSe nanocrystals after their functionalization with 4-formyldithiobenzoic acid. The grafting proceeds via a condensation reaction between the aldehyde group of the ligand and the terminal primary amine group of the tetramer. The resulting organic/inorganic hybrid exhibits complete extinction of the fluorescence of its constituents, indicating efficient charge or energy transfer between the organic and the inorganic semiconductors.

Revealing molecular-level surface structure of amyloid fibrils in liquid by means of frequency modulation atomic force microscopy

NASA Astrophysics Data System (ADS)

Fukuma, Takeshi; Mostaert, Anika S.; Serpell, Louise C.; Jarvis, Suzanne P.

2008-09-01

We have investigated the surface structure of islet amyloid polypeptide (IAPP) fibrils and α-synuclein protofibrils in liquid by means of frequency modulation atomic force microscopy (FM-AFM). Ångström-resolution FM-AFM imaging of isolated macromolecules in liquid is demonstrated for the first time. Individual β-strands aligned perpendicular to the fibril axis with a spacing of 0.5 nm are resolved in FM-AFM images, which confirms cross-β structure of IAPP fibrils in real space. FM-AFM images also reveal the existence of 4 nm periodic domains along the axis of IAPP fibrils. Stripe features with 0.5 nm spacing are also found in images of α-synuclein protofibrils. However, in contrast to the case for IAPP fibrils, the stripes are oriented 30° from the axis, suggesting the possibility of β-strand alignment in protofibrils different from that in mature fibrils or the regular arrangement of thioflavin T molecules present during the fibril preparation aligned at the surface of the protofibrils.

Degradation of nonmodified and rhodium modified aluminide coating deposited on CMSX 4 superalloy.

PubMed

Zagula-Yavorska, Maryana; Wierzbińska, Małgorzata; Gancarczyk, Kamil; Sieniawski, Jan

2016-07-01

The Ni-base superalloy CMSX 4 used in the turbine blades of aircraft engines was coated with rhodium layer (0.5-μm thick). Next coated CMSX 4 superalloy was aluminized by the CVD method. The rhodium modified aluminide coating and nonmodified aluminide coating were oxidized at 1100°C at the air atmosphere. The rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one. The spallation equal 62% of the total area was observed on the surface of the nonmodified coating whereas only 36% spallation area was observed on the surface of the rhodium modified aluminide coating after the oxidation test. The oxide layer formed on the surface of the nonmodified coating was composed of nonprotective (Ni,Cr)Al2 O4 and (Ni,Cr)O phases. Aluminium in the coating reacts with oxygen, forming a protective α-Al2 O3 oxide on the surface of the rhodium modified aluminide coating. When the oxide cracks and spalls due to oxidation, additional aluminium from the coating diffuses to the surface to form the oxide. The presence of protective Al2 O3 oxide on the surface of the rhodium modified aluminide coating slows coating degradation. Therefore, rhodium modified aluminide coating has better oxidation resistance than the nonmodified one. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Smooth deuterated cellulose films for the visualisation of adsorbed bio-macromolecules

PubMed Central

Su, Jielong; Raghuwanshi, Vikram S.; Raverty, Warwick; Garvey, Christopher J.; Holden, Peter J.; Gillon, Marie; Holt, Stephen A.; Tabor, Rico; Batchelor, Warren; Garnier, Gil

2016-01-01

Novel thin and smooth deuterated cellulose films were synthesised to visualize adsorbed bio-macromolecules using contrast variation neutron reflectivity (NR) measurements. Incorporation of varying degrees of deuteration into cellulose was achieved by growing Gluconacetobacter xylinus in deuterated glycerol as carbon source dissolved in growth media containing D2O. The derivative of deuterated cellulose was prepared by trimethylsilylation(TMS) in ionic liquid(1-butyl-3-methylimidazolium chloride). The TMS derivative was dissolved in toluene for thin film preparation by spin-coating. The resulting film was regenerated into deuterated cellulose by exposure to acidic vapour. A common enzyme, horseradish peroxidase (HRP), was adsorbed from solution onto the deuterated cellulose films and visualized by NR. The scattering length density contrast of the deuterated cellulose enabled accurate visualization and quantification of the adsorbed HRP, which would have been impossible to achieve with non-deuterated cellulose. The procedure described enables preparing deuterated cellulose films that allows differentiation of cellulose and non-deuterated bio-macromolecules using NR. PMID:27796332

Bacterial Translocation Ratchets: Shared Physical Principles with Different Molecular Implementations: How bacterial secretion systems bias Brownian motion for efficient translocation of macromolecules.

PubMed

Hepp, Christof; Maier, Berenike

2017-10-01

Secretion systems enable bacteria to import and secrete large macromolecules including DNA and proteins. While most components of these systems have been identified, the molecular mechanisms of macromolecular transport remain poorly understood. Recent findings suggest that various bacterial secretion systems make use of the translocation ratchet mechanism for transporting polymers across the cell envelope. Translocation ratchets are powered by chemical potential differences generated by concentration gradients of ions or molecules that are specific to the respective secretion systems. Bacteria employ these potential differences for biasing Brownian motion of the macromolecules within the conduits of the secretion systems. Candidates for this mechanism include DNA import by the type II secretion/type IV pilus system, DNA export by the type IV secretion system, and protein export by the type I secretion system. Here, we propose that these three secretion systems employ different molecular implementations of the translocation ratchet mechanism. © 2017 The Authors. BioEssays Published by WILEY Periodicals, Inc.

Principles and Overview of Sampling Methods for Modeling Macromolecular Structure and Dynamics

PubMed Central

Moffatt, Ryan; Ma, Buyong; Nussinov, Ruth

2016-01-01

Investigation of macromolecular structure and dynamics is fundamental to understanding how macromolecules carry out their functions in the cell. Significant advances have been made toward this end in silico, with a growing number of computational methods proposed yearly to study and simulate various aspects of macromolecular structure and dynamics. This review aims to provide an overview of recent advances, focusing primarily on methods proposed for exploring the structure space of macromolecules in isolation and in assemblies for the purpose of characterizing equilibrium structure and dynamics. In addition to surveying recent applications that showcase current capabilities of computational methods, this review highlights state-of-the-art algorithmic techniques proposed to overcome challenges posed in silico by the disparate spatial and time scales accessed by dynamic macromolecules. This review is not meant to be exhaustive, as such an endeavor is impossible, but rather aims to balance breadth and depth of strategies for modeling macromolecular structure and dynamics for a broad audience of novices and experts. PMID:27124275

AquaSAXS: a web server for computation and fitting of SAXS profiles with non-uniformally hydrated atomic models.

PubMed

Poitevin, Frédéric; Orland, Henri; Doniach, Sebastian; Koehl, Patrice; Delarue, Marc

2011-07-01

Small Angle X-ray Scattering (SAXS) techniques are becoming more and more useful for structural biologists and biochemists, thanks to better access to dedicated synchrotron beamlines, better detectors and the relative easiness of sample preparation. The ability to compute the theoretical SAXS profile of a given structural model, and to compare this profile with the measured scattering intensity, yields crucial structural informations about the macromolecule under study and/or its complexes in solution. An important contribution to the profile, besides the macromolecule itself and its solvent-excluded volume, is the excess density due to the hydration layer. AquaSAXS takes advantage of recently developed methods, such as AquaSol, that give the equilibrium solvent density map around macromolecules, to compute an accurate SAXS/WAXS profile of a given structure and to compare it to the experimental one. Here, we describe the interface architecture and capabilities of the AquaSAXS web server (http://lorentz.dynstr.pasteur.fr/aquasaxs.php).

Thermochemolysis: A New Sample Preparation Approach for the Detection of Organic Components of Complex Macromolecules in Mars Rocks via Gas Chromatography Mass Spectrometry in SAM on MSL

NASA Technical Reports Server (NTRS)

Eugenbrode, J.; Glavin, D.; Dworkin, J.; Conrad, P.; Mahaffy, P.

2011-01-01

Organic chemicals, when present in extraterrestrial samples, afford precious insight into past and modern conditions elsewhere in the Solar System . No single technology identifies all molecular components because naturally occurring molecules have different chemistries (e.g., polar vs. non-polar, low to high molecular weight) and interface with the ambient sample chemistry in a variety of modes (i.e., organics may be bonded, absorbed or trapped by minerals, liquids, gases, or other organics). More than 90% of organic matter in most natural samples on Earth and in meteorites is composed of complex macromolecules (e.g. biopolymers, complex biomolecules, humic substances, kerogen) because the processes that tend to break down organic molecules also tend towards complexation of the more recalcitrant components. Thus, methodologies that tap the molecular information contained within macromolecules may be critical to detecting extraterrestrial organic matter and assessing the sources and processes influencing its nature.

Principles and Overview of Sampling Methods for Modeling Macromolecular Structure and Dynamics.

PubMed

Maximova, Tatiana; Moffatt, Ryan; Ma, Buyong; Nussinov, Ruth; Shehu, Amarda

2016-04-01

Investigation of macromolecular structure and dynamics is fundamental to understanding how macromolecules carry out their functions in the cell. Significant advances have been made toward this end in silico, with a growing number of computational methods proposed yearly to study and simulate various aspects of macromolecular structure and dynamics. This review aims to provide an overview of recent advances, focusing primarily on methods proposed for exploring the structure space of macromolecules in isolation and in assemblies for the purpose of characterizing equilibrium structure and dynamics. In addition to surveying recent applications that showcase current capabilities of computational methods, this review highlights state-of-the-art algorithmic techniques proposed to overcome challenges posed in silico by the disparate spatial and time scales accessed by dynamic macromolecules. This review is not meant to be exhaustive, as such an endeavor is impossible, but rather aims to balance breadth and depth of strategies for modeling macromolecular structure and dynamics for a broad audience of novices and experts.

Determining the bacterial cell biology of Planctomycetes.

PubMed

Boedeker, Christian; Schüler, Margarete; Reintjes, Greta; Jeske, Olga; van Teeseling, Muriel C F; Jogler, Mareike; Rast, Patrick; Borchert, Daniela; Devos, Damien P; Kucklick, Martin; Schaffer, Miroslava; Kolter, Roberto; van Niftrik, Laura; Engelmann, Susanne; Amann, Rudolf; Rohde, Manfred; Engelhardt, Harald; Jogler, Christian

2017-04-10

Bacteria of the phylum Planctomycetes have been previously reported to possess several features that are typical of eukaryotes, such as cytosolic compartmentalization and endocytosis-like macromolecule uptake. However, recent evidence points towards a Gram-negative cell plan for Planctomycetes, although in-depth experimental analysis has been hampered by insufficient genetic tools. Here we develop methods for expression of fluorescent proteins and for gene deletion in a model planctomycete, Planctopirus limnophila, to analyse its cell organization in detail. Super-resolution light microscopy of mutants, cryo-electron tomography, bioinformatic predictions and proteomic analyses support an altered Gram-negative cell plan for Planctomycetes, including a defined outer membrane, a periplasmic space that can be greatly enlarged and convoluted, and an energized cytoplasmic membrane. These conclusions are further supported by experiments performed with two other Planctomycetes, Gemmata obscuriglobus and Rhodopirellula baltica. We also provide experimental evidence that is inconsistent with endocytosis-like macromolecule uptake; instead, extracellular macromolecules can be taken up and accumulate in the periplasmic space through unclear mechanisms.

Function of Platelet-Induced Epithelial Attachment at Titanium Surfaces Inhibits Microbial Colonization.

PubMed

Maeno, M; Lee, C; Kim, D M; Da Silva, J; Nagai, S; Sugawara, S; Nara, Y; Kihara, H; Nagai, M

2017-06-01

The aim of this study was to evaluate the barrier function of platelet-induced epithelial sheets on titanium surfaces. The lack of functional peri-implant epithelial sealing with basal lamina (BL) attachment at the interface of the implant and the adjacent epithelium allows for bacterial invasion, which may lead to peri-implantitis. Although various approaches have been reported to combat bacterial infection by surface modifications to titanium, none of these have been successful in a clinical application. In our previous study, surface modification with protease-activated receptor 4-activating peptide (PAR4-AP), which induced platelet activation and aggregation, was successful in demonstrating epithelial attachment via BL and epithelial sheet formation on the titanium surface. We hypothesized that the platelet-induced epithelial sheet on PAR4-AP-modified titanium surfaces would reduce bacterial attachment, penetration, and invasion. Titanium surface was modified with PAR4-AP and incubated with platelet-rich plasma (PRP). The aggregated platelets released collagen IV, a critical BL component, onto the PAR4-AP-modified titanium surface. Then, human gingival epithelial cells were seeded on the modified titanium surface and formed epithelial sheets. Green fluorescent protein (GFP)-expressing Escherichia coli was cultured onto PAR4-AP-modified titanium with and without epithelial sheet formation. While Escherichia coli accumulated densely onto the PAR4-AP titanium lacking epithelial sheet, few Escherichia coli were observed on the epithelial sheet on the PAR4-AP surface. No bacterial invasion into the interface of the epithelial sheet and the titanium surface was observed. These in vitro results indicate the efficacy of a platelet-induced epithelial barrier that functions to prevent bacterial attachment, penetration, and invasion on PAR4-AP-modified titanium.

Study of the adhesion of neurodegenerative proteins on plasma-modified and coated polypropylene surfaces.

PubMed

Poncin-Epaillard, F; Mille, C; Debarnot, D; Zorzi, W; El Moualij, B; Coudreuse, A; Legeay, G; Quadrio, I; Perret-Liaudet, A

2012-01-01

The inner polymeric surface of an ELISA titration well is plasma-modified and coated with different surfactant molecules. The titration of neurodegenerative proteins markers (prion, Tau and β-synuclein), previously demonstrated as more efficient with such modified tubes, is related to the adhesion behaviour of these proteins and their corresponding capture antibodies. The adhesion process is studied in terms of anchoring and specific mechanisms. The proteins and antibodies binding onto such modified surfaces is related to the substrate hydrophilic character calculated from the angle contact measure, to the polymer surface charge measured through the streaming potential determination at different pH and the inner surface roughness determined from AFM images. Furthermore, the influence of the blocking agent used during the ELISA titration is also studied.

Steady-State Linear and Non-linear Optical Spectroscopy of Organic Chromophores and Bio-macromolecules

NASA Astrophysics Data System (ADS)

Marazzi, Marco; Gattuso, Hugo; Monari, Antonio; Assfeld, Xavier

2018-04-01

Bio-macromolecules as DNA, lipid membranes and (poly)peptides are essential compounds at the core of biological systems. The development of techniques and methodologies for their characterization is therefore necessary and of utmost interest, even though difficulties can be experienced due to their intrinsic complex nature. Among these methods, spectroscopies, relying on optical properties are especially important to determine their macromolecular structures and behaviors, as well as the possible interactions and reactivity with external dyes – often drugs or pollutants – that can (photo)sensitize the bio-macromolecule leading to eventual chemical modifications, thus damages. In this review, we will focus on the theoretical simulation of electronic spectroscopies of bio-macromolecules, considering their secondary structure and including their interaction with different kind of (photo)sensitizers. Namely, absorption, emission and electronic circular dichroism (CD) spectra are calculated and compared with the available experimental data. Non-linear properties will be also taken into account by two-photon absorption, a highly promising technique (i) to enhance absorption in the red and infra-red windows and (ii) to enhance spatial resolution. Methodologically, the implications of using implicit and explicit solvent, coupled to quantum and thermal samplings of the phase space, will be addressed. Especially, hybrid quantum mechanics/ molecular mechanics (QM/MM) methods are explored for a comparison with solely QM methods, in order to address the necessity to consider an accurate description of environmental effects on spectroscopic properties of biological systems.

Diffusion profile of macromolecules within and between human skin layers for (trans)dermal drug delivery.

PubMed

Römgens, Anne M; Bader, Dan L; Bouwstra, Joke A; Baaijens, Frank P T; Oomens, Cees W J

2015-10-01

Delivering a drug into and through the skin is of interest as the skin can act as an alternative drug administration route for oral delivery. The development of new delivery methods, such as microneedles, makes it possible to not only deliver small molecules into the skin, which are able to pass the outer layer of the skin in therapeutic amounts, but also macromolecules. To provide insight into the administration of these molecules into the skin, the aim of this study was to assess the transport of macromolecules within and between its various layers. The diffusion coefficients in the epidermis and several locations in the papillary and reticular dermis were determined for fluorescein dextran of 40 and 500 kDa using a combination of fluorescent recovery after photobleaching experiments and finite element analysis. The diffusion coefficient was significantly higher for 40 kDa than 500 kDa dextran, with median values of 23 and 9 µm(2)/s in the dermis, respectively. The values only marginally varied within and between papillary and reticular dermis. For the 40 kDa dextran, the diffusion coefficient in the epidermis was twice as low as in the dermis layers. The adopted method may be used for other macromolecules, which are of interest for dermal and transdermal drug delivery. The knowledge about diffusion in the skin is useful to optimize (trans)dermal drug delivery systems to target specific layers or cells in the human skin. Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface modification of hydroxyapatite nanoparticles by poly( L-phenylalanine) via ROP of L-phenylalanine N-carboxyanhydride (Pha-NCA)

NASA Astrophysics Data System (ADS)

Dai, Yanfeng; Xu, Min; Wei, Junchao; Zhang, Haobin; Chen, Yiwang

2012-01-01

The surface of hydroxyapatite nanoparticles was modified by poly(L-phenylalanine) via the ring opening polymerization (ROP) of L-phenylalanine N-carboxyanhydride. The preparation procedure was monitored by Fourier transform infrared spectroscopy (FTIR), and the modified hydroxyapatite was characterized by thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). The results showed that the surface grafting amounts of poly(L-phenylalanine) on HA ranging from 20.26% to 38.92% can be achieved by tuning the reaction condition. The XRD patterns demonstrated that the crystalline structure of the modified hydroxyapatite was nearly the same with that of HA, implying that the ROP was an efficient surface modification method. The MTT assay proved that the biocompatibility of modified HA was very good, which showed the potential application of modified HA in bone tissue engineering.

Interactions between cells and ionized dendritic biomaterials: Flow cytometry and fluorescence spectroscopic studies

NASA Astrophysics Data System (ADS)

Kannan, R. M.; Kolhe, Parag; Khandare, Jayant; Kannan, Sujatha; Lieh-Lai, Mary

2004-03-01

Dendrimers and hyperbranched polymers are a new class of macromolecules characterized by large density of "tunable" peripheral functional groups. Therefore dendrimers can serve as a model macromolecular system to study the influence of molecular geometry and charge density on transport across biological barriers, especially cellular interfaces. The effect of size, end-functionality, surface charge (pH), and the nature of the cell surface are expected to play an important role in transport, and are investigated using flow cytometry, fluorescene microscopy and UV/Vis spectroscopy. Our results suggest that at physiological pH, cationic polyamidoamine (PAMAM) dendrimers can enter the A549 cancer lung epithelial cells within 5 minutes, perhaps due to the favorable interaction between anionic surface receptors of cells and cationic PAMAM dendrimer, through adsorptive endocytosis. On the other hand, hyperbranched polyol, which is a neutral polymer at physiological pH, enters cells at a much slower rate. The entry of hyperbranched polyol may be because of fluid-phase pinocytosis. Our results also indicate that the dendritic polymers enter the cell surface much more rapidly than linear polymers, and some small drugs, suggesting that the high density of functional groups plays a key role in the interaction with the cell surface, and the subsequent transport inside.

Oriented and covalent immobilization of target molecules to solid supports: synthesis and application of a light-activatable and thiol-reactive cross-linking reagent.

PubMed

Collioud, A; Clémence, J F; Sänger, M; Sigrist, H

1993-01-01

Light-dependent oriented and covalent immobilization of target molecules has been achieved by combining two modification procedures: light-dependent coupling of target molecules to inert surfaces and thiol-selective reactions occurring at macromolecule or substrate surfaces. For immobilization purposes the heterobifunctional reagent N-[m-[3-(trifluoromethyl)diazirin-3-yl]phenyl]-4-maleimidobutyr amide was synthesized and chemically characterized. The photosensitivity of the carbene-generating reagent and its reactivity toward thiols were ascertained. Light-induced cross-linking properties of the reagent were documented (i) by reacting first the maleimide function with a thiolated surface, followed by carbene insertion into applied target molecules, (ii) by photochemical coupling of the reagent to an inert support followed by thermochemical reactions with thiol functions, and (iii) by thermochemical modification of target molecules prior to carbene-mediated insertion into surface materials. Procedures mentioned led to light-dependent covalent immobilization of target molecules including amino acids, a synthetic peptide, and antibody-derived F(ab') fragments. Topically selective, light-dependent immobilization was attained with the bifunctional reagent by irradiation of coated surfaces through patterned masks. Glass and polystyrene served as substrates. Molecular orientation is asserted by inherently available or selectively introduced terminal thiol functions in F(ab') fragments and synthetic polypeptides, respectively.

Improving dissolution and oral bioavailability of pranlukast hemihydrate by particle surface modification with surfactants and homogenization

PubMed Central

Ha, Eun-Sol; Baek, In-hwan; Yoo, Jin-Wook; Jung, Yunjin; Kim, Min-Soo

2015-01-01

The present study was carried out to develop an oral formulation of pranlukast hemihydrate with improved dissolution and oral bioavailability using a surface-modified microparticle. Based on solubility measurements, surface-modified pranlukast hemihydrate microparticles were manufactured using the spray-drying method with hydroxypropylmethyl cellulose, sucrose laurate, and water and without the use of an organic solvent. The hydrophilicity of the surface-modified pranlukast hemihydrate microparticle increased, leading to enhanced dissolution and oral bioavailability of pranlukast hemihydrate without a change in crystallinity. The surface-modified microparticles with an hydroxypropylmethyl cellulose/sucrose laurate ratio of 1:2 showed rapid dissolution of up to 85% within 30 minutes in dissolution medium (pH 6.8) and oral bioavailability higher than that of the commercial product, with approximately 2.5-fold and 3.9-fold increases in area under the curve (AUC0→12 h) and peak plasma concentration, respectively. Therefore, the surface-modified microparticle is an effective oral drug delivery system for the poorly water-soluble therapeutic pranlukast hemihydrate. PMID:26150699

Surface-and bulk-properties of EPDM rubber modified by electron beam irradiation

NASA Astrophysics Data System (ADS)

Majumder, Papiya Sen; Bhowmick, Anil K.

1999-01-01

Electron beam initiated grafting of trimethylol propane triacrylate (TMPTA) onto ethylene propylene diene monomer (EPDM) has been carried out over a wide range of irradiation doses (0-200 kGy) using a fixed concentration (10%) of TMPTA. The samples have been both surface and bulk modified. Infrared (IR) studies indicate increased peak absorbances at 1730, 1260, 1120 and 1019 cm -1 upto 50 kGy and hence increased CO and C-O-C concentrations. The results are further supported by X-ray photoelectron spectroscopy (XPS) studies. The surface energy of EPDM increases from 46.5 to 60.7 mJ/m 2 on irradiation of the surface modified samples to 50 kGy dose, due to increased contribution of γSAB and γS(-). The results have been explained with the help of IR and XPS data. The values of tensile strength of the surface modified samples have not changed very significantly, while the moduli values have increased at the cost of the elongation at break. DMTA studies have shown changes in Tg and tan δmax on modification of the surface. The surface morphology of the modified and irradiated samples reveals acrylate flow marks at high magnification.

Turbulent Boundary Layer Flow over Superhydrophobic Surfaces

DTIC Science & Technology

2013-05-10

DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Turbulent Boundary Layer Flow over Superhydrophobic ...modified surfaces. This study encompassed the testing of four different surfaces: 1) Teflon SLIP, 2) Aluminum SLIP, 3) Honeycomb Superhydrophobic and 4...Polydimethylsiloxane elastomer (PDMSe) Superhydrophobic . Each of these surfaces uses specific geometrical surface features to modify the original

Heparanase confers a growth advantage to differentiating murine embryonic stem cells, and enhances oligodendrocyte formation.

PubMed

Xiong, Anqi; Kundu, Soumi; Forsberg, Maud; Xiong, Yuyuan; Bergström, Tobias; Paavilainen, Tanja; Kjellén, Lena; Li, Jin-Ping; Forsberg-Nilsson, Karin

2017-10-01

Heparan sulfate proteoglycans (HSPGs), ubiquitous components of mammalian cells, play important roles in development and homeostasis. These molecules are located primarily on the cell surface and in the pericellular matrix, where they interact with a multitude of macromolecules, including many growth factors. Manipulation of the enzymes involved in biosynthesis and modification of HSPG structures alters the properties of stem cells. Here, we focus on the involvement of heparanase (HPSE), the sole endo-glucuronidase capable of cleaving of HS, in differentiation of embryonic stem cells into the cells of the neural lineage. Embryonic stem (ES) cells overexpressing HPSE (Hpse-Tg) proliferated more rapidly than WT ES cells in culture and formed larger teratomas in vivo. In addition, differentiating Hpse-Tg ES cells also had a higher growth rate, and overexpression of HPSE in NSPCs enhanced Erk and Akt phosphorylation. Employing a two-step, monolayer differentiation, we observed an increase in HPSE as wild-type (WT) ES cells differentiated into neural stem and progenitor cells followed by down-regulation of HPSE as these NSPCs differentiated into mature cells of the neural lineage. Furthermore, NSPCs overexpressing HPSE gave rise to more oligodendrocytes than WT cultures, with a concomitant reduction in the number of neurons. Our present findings emphasize the importance of HS, in neural differentiation and suggest that by regulating the availability of growth factors and, or other macromolecules, HPSE promotes differentiation into oligodendrocytes. Copyright © 2016 Elsevier B.V. All rights reserved.

Peptides Enhance Mg Content of Calcite: Toward a Process-Based Understanding of Proxy Models

NASA Astrophysics Data System (ADS)

Dove, P.; Stephenson, A.; Wu, L.; Wu, K.; de Yoreo, J.; Hoyer, J.

2008-12-01

Investigations of modern organisms relating magnesium content of calcified skeletons to temperature often exhibit unexplained deviations from the signature expected for inorganically precipitated calcite. These 'vital effects' are believed to have kinetic and taxonomic origins but the mechanistic basis for measured offsets remains unclear. A complicating factor is that mineralization is isolated from the external environment within an organic-rich matrix whose roles in mineralization are implicated but not well understood. Here we show that a simple hydrophilic peptide, sharing the same acidic character as macromolecules isolated from sites of calcification, increases the magnesium content of calcite up to 3 mol%. Using in situ AFM, we demonstrate that (Asp3Gly)6Asp3 also enhances growth rate and step edge energy of calcite compared to inorganic controls. Kinetic and thermodynamic measurements indicate that biomolecules interact with calcite surfaces to lower the energy barrier to desolvating the more strongly hydrated magnesium ion, thereby increasing the probability of its incorporation relative to calcium. Comparisons to previous studies that correlate Mg content of carbonate minerals with temperature show this peptide-induced Mg- enhancement is equivalent to offsets of several degrees Centigrade. The findings suggest local macromolecule chemistry influences Mg signatures- a plausible origin of vital effects. Further, studies of nonskeletal carbonates have long-asked whether the natural marine humic and protein substances found in sedimentary environments may influence mineralization. These insights provide a physical basis for anecdotal evidence that organic chemistry modulates the mineralization of inorganic carbonates.

Comparison of Zirconium Phosphonate-Modified Surfaces for Immobilizing Phosphopeptides and Phosphate-Tagged Proteins.

PubMed

Forato, Florian; Liu, Hao; Benoit, Roland; Fayon, Franck; Charlier, Cathy; Fateh, Amina; Defontaine, Alain; Tellier, Charles; Talham, Daniel R; Queffélec, Clémence; Bujoli, Bruno

2016-06-07

Different routes for preparing zirconium phosphonate-modified surfaces for immobilizing biomolecular probes are compared. Two chemical-modification approaches were explored to form self-assembled monolayers on commercially available primary amine-functionalized slides, and the resulting surfaces were compared to well-characterized zirconium phosphonate monolayer-modified supports prepared using Langmuir-Blodgett methods. When using POCl3 as the amine phosphorylating agent followed by treatment with zirconyl chloride, the result was not a zirconium-phosphonate monolayer, as commonly assumed in the literature, but rather the process gives adsorbed zirconium oxide/hydroxide species and to a lower extent adsorbed zirconium phosphate and/or phosphonate. Reactions giving rise to these products were modeled in homogeneous-phase studies. Nevertheless, each of the three modified surfaces effectively immobilized phosphopeptides and phosphopeptide tags fused to an affinity protein. Unexpectedly, the zirconium oxide/hydroxide modified surface, formed by treating the amine-coated slides with POCl3/Zr(4+), afforded better immobilization of the peptides and proteins and efficient capture of their targets.

Permeable reactive barrier of surface hydrophobic granular activated carbon coupled with elemental iron for the removal of 2,4-dichlorophenol in water.

PubMed

Yang, Ji; Cao, Limei; Guo, Rui; Jia, Jinping

2010-12-15

Granular activated carbon was modified with dimethyl dichlorosilane to improve its surface hydrophobicity, and therefore to improve the performance of permeable reactive barrier constructed with the modified granular activated carbon and elemental iron. X-ray photoelectron spectroscopy shows that the surface silicon concentration of the modified granular activated carbon is higher than that of the original one, leading to the increased surface hydrophobicity. Although the specific surface area decreased from 895 to 835 m(2)g(-1), the modified granular activated carbon could adsorb 20% more 2,4-dichlorophenol than the original one did in water. It is also proven that the permeable reactive barrier with the modified granular activated carbon is more efficient at 2,4-dichlorophenol dechlorination, in which process 2,4-dichlorophenol is transformed to 2-chlorophenol or 4-chlorophenol then to phenol, or to phenol directly. Copyright © 2010 Elsevier B.V. All rights reserved.

Tuning the Band Bending and Controlling the Surface Reactivity at Polar and Nonpolar Surfaces of ZnO through Phosphonic Acid Binding.

PubMed

McNeill, Alexandra R; Hyndman, Adam R; Reeves, Roger J; Downard, Alison J; Allen, Martin W

2016-11-16

ZnO is a prime candidate for future use in transparent electronics; however, development of practical materials requires attention to factors including control of its unusual surface band bending and surface reactivity. In this work, we have modified the O-polar (0001̅), Zn-polar (0001), and m-plane (101̅0) surfaces of ZnO with phosphonic acid (PA) derivatives and measured the effect on the surface band bending and surface sensitivity to atmospheric oxygen. Core level and valence band synchrotron X-ray photoemission spectroscopy was used to measure the surface band bending introduced by PA modifiers with substituents of opposite polarity dipole moment: octadecylphosphonic acid (ODPA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctylphosphonic acid (F 13 OPA). Both PAs act as surface electron donors, increasing the downward band bending and the strength of the two-dimensional surface electron accumulation layer on all of the ZnO surfaces investigated. On the O-polar (0001̅) and m-plane (101̅0) surfaces, the ODPA modifier produced the largest increase in downward band bending relative to the hydroxyl-terminated unmodified surface of 0.55 and 0.35 eV, respectively. On the Zn-polar (0001) face, the F 13 OPA modifier gave the largest increase (by 0.50 eV) producing a total downward band bending of 1.00 eV, representing ∼30% of the ZnO band gap. Ultraviolet (UV) photoinduced surface wettability and photoconductivity measurements demonstrated that the PA modifiers are effective at decreasing the sensitivity of the surface toward atmospheric oxygen. Modification with PA derivatives produced a large increase in the persistence of UV-induced photoconductivity and a large reduction in UV-induced changes in surface wettability.

Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

DOE PAGES

Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

2015-03-27

Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to producemore » carbon monoxide and methane. In addition, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.« less

Nanophosphor composite scintillators comprising a polymer matrix

DOEpatents

Muenchausen, Ross Edward; Mckigney, Edward Allen; Gilbertson, Robert David

2010-11-16

An improved nanophosphor composite comprises surface modified nanophosphor particles in a solid matrix. The nanophosphor particle surface is modified with an organic ligand, or by covalently bonding a polymeric or polymeric precursor material. The surface modified nanophosphor particle is essentially charge neutral, thereby preventing agglomeration of the nanophosphor particles during formation of the composite material. The improved nanophosphor composite may be used in any conventional scintillator application, including in a radiation detector.

Development and characterization of ferrihydrite-modified diatomite as a phosphorus adsorbent.

PubMed

Xiong, Wenhui; Peng, Jian

2008-12-01

A novel phosphorus adsorbent, ferrihydrite-modified diatomite was developed and characterized in this study. The ferrihydrite-modified diatomite was made through surface modification treatments including NaOH treatment and ferrihydrite deposition on raw diatomite. In the NaOH treatment, surface SiO(2) of diatomite was partially dissolved in the NaOH solution. The dissolved Si contributed to form the stable 2-line ferrihydrite which deposited into the macropores and mesopores of diatomite. Blocking macropores and larger mesopores of diatomite with 0.24g Fe/g of 2-line ferrihydrite resulted in a specific surface area of 211.1m(2)/g for the ferrihydrite-modified diatomite, which is 8.5-fold increase than the raw diatomite (24.77m(2)/g). The surface modification also increased the point of zero charge (pH(PZC)) values to 10 for the ferrihydrite-modified diatomite from 5.8 for the raw diatomite. Because of the increased surface area and surface charge, the maximum adsorption capacity of ferrihydrite-modified diatomite at pH 4 and pH 8.5 was increased from 10.2mgP/g and 1.7mgP/g of raw diatomite to 37.3mgP/g and 13.6mgP/g, respectively.

PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes

PubMed Central

Nady, Norhan

2016-01-01

A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled “green surface modification”. This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers—ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)—is presented. PMID:27096873

New mechanisms of macroion-induced disintegration of charged droplets

NASA Astrophysics Data System (ADS)

Consta, Styliani; Oh, Myong In; Malevanets, Anatoly

2016-10-01

Molecular modeling has revealed that the presence of charged macromolecules (macroions) in liquid droplets dramatically changes the pathways of droplet fission. These mechanisms are not captured by the traditional theories such as ion-evaporation and charge-residue models. We review the general mechanisms by which macroions emerge from droplets and the factors that determine the droplet fission. These mechanisms include counter-intuitive ;star; droplet formations and extrusion of linear macroions from droplets. These findings may play a direct role in determining macromolecule charge states in electrospray mass spectrometry experiments.

Neural control of muscle

NASA Technical Reports Server (NTRS)

Max, S. R.; Markelonis, G. J.

1983-01-01

Cholinergic innervation regulates the physiological and biochemical properties of skeletal muscle. The mechanisms that appear to be involved in this regulation include soluble, neurally-derived polypeptides, transmitter-evoked muscle activity and the neurotransmitter, acetylcholine, itself. Despite extensive research, the interacting neural mechanisms that control such macromolecules as acetylcholinesterase, the acetylcholine receptor and glucose 6-phosphate dehydrogenase remain unclear. It may be that more simplified in vitro model systems coupled with recent dramatic advances in the molecular biology of neurally-regulated proteins will begin to allow researchers to unravel the mechanisms controlling the expression and maintenance of these macromolecules.

Peptide-directed self-assembly of hydrogels

PubMed Central

Kopeček, Jindřich; Yang, Jiyuan

2009-01-01

This review focuses on the self-assembly of macromolecules mediated by the biorecognition of peptide/protein domains. Structures forming α-helices and β-sheets have been used to mediate self-assembly into hydrogels of peptides, reactive copolymers and peptide motifs, block copolymers, and graft copolymers. Structural factors governing the self-assembly of these molecules into precisely defined three-dimensional structures (hydrogels) are reviewed. The incorporation of peptide motifs into hybrid systems, composed of synthetic and natural macromolecules, enhances design opportunities for new biomaterials when compared to individual components. PMID:18952513

Microstructure evolution and tribological properties of acrylonitrile-butadiene rubber surface modified by atmospheric plasma treatment

NASA Astrophysics Data System (ADS)

Shen, Ming-xue; Zhang, Zhao-xiang; Peng, Xu-dong; Lin, Xiu-zhou

2017-09-01

For the purpose of prolonging the service life for rubber sealing elements, the frictional behavior of acrylonitrile-butadiene rubber (NBR) surface by dielectric barrier discharge plasma treatments was investigated in this paper. Surface microstructure and chemical composition were measured by atomic force microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. Water contact angles of the modified rubber surface were also measured to evaluate the correlation between surface wettability and tribological properties. The results show that plasma treatments can improve the properties of the NBR against friction and wear effectively, the surface microstructure and roughness of plasma-modified NBR surface had an important influence on the surface tribological behavior, and the wear depth first decreased and then increased along with the change of plasma treatment time. It was found that the wettability of the modified surface was gradually improved, which was mainly due to the change of the chemical composition after the treatment. This study suggests that the plasma treatment could effectively improve the tribological properties of the NBR surface, and also provides information for developing wear-resistant NBR for industrial applications.

Tissue response to intraperitoneal implants of polyethylene oxide-modified polyethylene terephthalate.

PubMed

Desai, N P; Hubbell, J A

1992-01-01

Polyethylene terephthalate films surface modified with polyethylene oxide of mol wt 18,500 g/mol (18.5 k) by a previously described technique, were implanted in the peritoneal cavity of mice, along with their respective untreated controls, for periods of 1-28 d. The implants were retrieved and examined for tissue reactivity and cellular adherence. The control polyethylene terephthalate surfaces showed an initial inflammatory reaction followed by an extensive fibrotic response with a mean thickness of 60 microns at 28 d. By contrast, polyethylene oxide-modified polyethylene terephthalate showed only a mild inflammatory response and no fibrotic encapsulation throughout the implantation period: at 28 d a cellular monolayer was observed. Apparently either the polyethylene oxide-modified surface was stimulating less inflammation, which was in turn stimulating less fibroblastic overgrowth, or the cellular adhesion to the polyethylene oxide-modified surface was too weak to support cellular multilayers.

Surface nucleation and independent growth of Ce(OH)4 within confinement space on modified carbon black surface to prepare nano-CeO2 without agglomeration

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Xia, Chunhui; Li, Kaitao; Lin, Yanjun

2018-06-01

Highly dispersed negative carboxyl groups can be formed on carbon black (CB) surface modified with strong nitric acid. Therefore positive cations can be uniformly absorbed by carboxyl groups and precipitated within a confinement space on modified CB surface to prepare highly dispersed nanomaterials. In this paper, the formation and dispersion status of surface negative carboxyl groups, adsorption status of Ce3+, surface confinement nucleation, crystallization and calcination process were studied by EDS, SEM, and laser particle size analysis. The results show that the carboxyl groups formed on modified CB surface are highly dispersed, and Ce3+ cations can be uniformly anchored by carboxyl groups. Therefore, highly dispersed Ce3+ can react with OH- within a confinement surface region to form positive nano-Ce(OH)4 nuclei which also can be adsorbed by electrostatic attraction. After independent growth of Ce(OH)4 without agglomeration, highly dispersed CeO2 nanoparticles without agglomeration can be prepared together with the help of effectively isolates by CO2 released in the combustion of CB.

Surface Modification of SiO2 Microchannels with Biocompatible Polymer Using Supercritical Carbon Dioxide

NASA Astrophysics Data System (ADS)

Saito, Tatsuro; Momose, Takeshi; Hoshi, Toru; Takai, Madoka; Ishihara, Kazuhiko; Shimogaki, Yukihiro

2010-11-01

The surface of 500-mm-long microchannels in SiO2 microchips was modified using supercritical CO2 (scCO2) and a biocompatible polymer was coated on it to confer biocompatibility to the SiO2 surface. In this method, the SiO2 surface of a microchannel was coated with poly(ethylene glycol monomethacrylate) (PEGMA) as the biocompatible polymer using allyltriethoxysilane (ATES) as the anchor material in scCO2 as the reactive medium. Results were compared with those using the conventional wet method. The surface of a microchannel could not be modified by the wet method owing to the surface tension and viscosity of the liquid, but it was modified uniformly by the scCO2 method probably owing to the near-zero surface tension, low viscosity, and high diffusivity of scCO2. The effect of the surface modification by the scCO2 method to prevent the adsorption of protein was as high as that of the modification by the wet method. Modified microchips can be used in biochemical and medical analyses.

Surface nucleation and independent growth of Ce(OH)4 within confinement space on modified carbon black surface to prepare nano-CeO2 without agglomeration

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Xia, Chunhui; Li, Kaitao; Lin, Yanjun

2018-04-01

Highly dispersed negative carboxyl groups can be formed on carbon black (CB) surface modified with strong nitric acid. Therefore positive cations can be uniformly absorbed by carboxyl groups and precipitated within a confinement space on modified CB surface to prepare highly dispersed nanomaterials. In this paper, the formation and dispersion status of surface negative carboxyl groups, adsorption status of Ce3+, surface confinement nucleation, crystallization and calcination process were studied by EDS, SEM, and laser particle size analysis. The results show that the carboxyl groups formed on modified CB surface are highly dispersed, and Ce3+ cations can be uniformly anchored by carboxyl groups. Therefore, highly dispersed Ce3+ can react with OH- within a confinement surface region to form positive nano-Ce(OH)4 nuclei which also can be adsorbed by electrostatic attraction. After independent growth of Ce(OH)4 without agglomeration, highly dispersed CeO2 nanoparticles without agglomeration can be prepared together with the help of effectively isolates by CO2 released in the combustion of CB.

Covalent attachment of phospholipid analogous polymers to modify a polymeric membrane surface: a novel approach.

PubMed

Xu, Zhi-Kang; Dai, Qing-Wen; Wu, Jian; Huang, Xiao-Jun; Yang, Qian

2004-02-17

A novel method for the surface modification of a microporous polypropylene membrane by tethering phospholipid analogous polymers (PAPs) is given, which includes the photoinduced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and the ring-opening reaction of grafted poly-(DMAEMA) with 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes. Five 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes, containing octyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy, and octadecyloxy groups in the molecular structure, were used to fabricate the PAP-modified polypropylene membranes. The attenuated total reflectance FT-IR spectra of the original, poly(DMAEMA)-grafted, and PAP-modified membranes confirmed the chemical changes on the membrane surface. Scanning electron microscope pictures showed that, compared with the original membrane, the surface porosities ofpoly(DMAEMA)-grafted and PAP-modified membranes were somewhat reduced. Water contact angles measured by the sessile drop method on PAP-modified membranes were slightly lower than that on the original polypropylene membrane, but higher than those on poly(DMAEMA)-grafted membranes with the exception of octyloxy-containing PAP-modified membranes. However, BSA adsorption experiments indicated that the five PAP-modified membranes had a much better protein-resistant property than the original polypropylene membrane and the poly(DMAEMA)-grafted membranes. For hexadecyloxy- and octadecyloxy-containing PAP-modified membranes, almost no protein adsorption was observed when the grafting degree was above 6 wt %. It was also found that the platelet adhesion was remarkably suppressed on the PAP-modified membranes. All these results demonstrate that the described approach is an effective way to improve the surface biocompatibility for polymeric membranes.

Prospects of using titanium nickelide implants with modified surface in dental implantology.

PubMed

Razdorsky, V V

2008-06-01

Corrosion resistance and biocompatibility of 60 specimens of titanium nickelide with modified surfaces implanted into spongy bone were studied in rabbit experiments. Specimens modified by molybdenum ions exhibited high inertness and favorable tissue reaction. No accumulation of nickel and titanium ions in animal organs was detected.

Effect of Surfaces on Amyloid Fibril Formation

PubMed Central

Moores, Bradley; Drolle, Elizabeth; Attwood, Simon J.; Simons, Janet; Leonenko, Zoya

2011-01-01

Using atomic force microscopy (AFM) we investigated the interaction of amyloid beta (Aβ) (1–42) peptide with chemically modified surfaces in order to better understand the mechanism of amyloid toxicity, which involves interaction of amyloid with cell membrane surfaces. We compared the structure and density of Aβ fibrils on positively and negatively charged as well as hydrophobic chemically-modified surfaces at physiologically relevant conditions. We report that due to the complex distribution of charge and hydrophobicity amyloid oligomers bind to all types of surfaces investigated (CH3, COOH, and NH2) although the charge and hydrophobicity of surfaces affected the structure and size of amyloid deposits as well as surface coverage. Hydrophobic surfaces promote formation of spherical amorphous clusters, while charged surfaces promote protofibril formation. We used the nonlinear Poisson-Boltzmann equation (PBE) approach to analyze the electrostatic interactions of amyloid monomers and oligomers with modified surfaces to complement our AFM data. PMID:22016789

Catalytic Micromotors Moving Near Polyelectrolyte-Modified Substrates: The Roles of Surface Charges, Morphology, and Released Ions.

PubMed

Wei, Mengshi; Zhou, Chao; Tang, Jinyao; Wang, Wei

2018-01-24

Synthetic microswimmers, or micromotors, are finding potential uses in a wide range of applications, most of which involve boundaries. However, subtle yet important effects beyond physical confinement on the motor dynamics remain less understood. In this letter, glass substrates were functionalized with positively and negatively charged polyelectrolytes, and the dynamics of micromotors moving close to the modified surfaces was examined. Using acoustic levitation and numerical simulation, we reveal how the speed of a chemically propelled micromotor slows down significantly near a polyelectrolyte-modified surface by the combined effects of surface charges, surface morphology, and ions released from the films.

Observation of Single-Protein and DNA Macromolecule Collisions on Ultramicroelectrodes.

PubMed

Dick, Jeffrey E; Renault, Christophe; Bard, Allen J

2015-07-08

Single-molecule detection is the ultimate sensitivity in analytical chemistry and has been largely unavailable in electrochemical analysis. Here, we demonstrate the feasibility of detecting electrochemically inactive single biomacromolecules, such as enzymes, antibodies, and DNA, by blocking a solution redox reaction when molecules adsorb and block electrode sites. By oxidizing a large concentration of potassium ferrocyanide on an ultramicroelectrode (UME, radius ≤150 nm), time-resolved, discrete adsorption events of antibodies, enzymes, DNA, and polystyrene nanospheres can be differentiated from the background by their "footprint". Further, by assuming that the mass transport of proteins to the electrode surface is controlled mainly by diffusion, a size estimate using the Stokes-Einstein relationship shows good agreement of electrochemical data with known protein sizes.

A differential equation for the Generalized Born radii.

PubMed

Fogolari, Federico; Corazza, Alessandra; Esposito, Gennaro

2013-06-28

The Generalized Born (GB) model offers a convenient way of representing electrostatics in complex macromolecules like proteins or nucleic acids. The computation of atomic GB radii is currently performed by different non-local approaches involving volume or surface integrals. Here we obtain a non-linear second-order partial differential equation for the Generalized Born radius, which may be solved using local iterative algorithms. The equation is derived under the assumption that the usual GB approximation to the reaction field obeys Laplace's equation. The equation admits as particular solutions the correct GB radii for the sphere and the plane. The tests performed on a set of 55 different proteins show an overall agreement with other reference GB models and "perfect" Poisson-Boltzmann based values.

Functionalized gold nanoparticles for the binding, stabilization, and delivery of therapeutic DNA, RNA, and other biological macromolecules

PubMed Central

DeLong, Robert K; Reynolds, Christopher M; Malcolm, Yaneika; Schaeffer, Ashley; Severs, Tiffany; Wanekaya, Adam

2010-01-01

Nanotechnology has virtually exploded in the last few years with seemingly limitless opportunity across all segments of our society. If gene and RNA therapy are to ever realize their full potential, there is a great need for nanomaterials that can bind, stabilize, and deliver these macromolecular nucleic acids into human cells and tissues. Many researchers have turned to gold nanomaterials, as gold is thought to be relatively well tolerated in humans and provides an inert material upon which nucleic acids can attach. Here, we review the various strategies for associating macromolecular nucleic acids to the surface of gold nanoparticles (GNPs), the characterization chemistries involved, and the potential advantages of GNPs in terms of stabilization and delivery. PMID:24198471

Poly (amidoamine) (PAMAM) dendrimer mediated delivery of drug and pDNA/siRNA for cancer therapy.

PubMed

Li, Jun; Liang, Huamin; Liu, Jing; Wang, Ziyuan

2018-07-30

Poly (amidoamine) (PAMAM) dendrimers are well-defined, highly branched macromolecules with numerous active amine groups on the surface. Because of their unique properties, PAMAM dendrimers have steadily grown in popularity in drug delivery, gene therapy, medical imaging and diagnostic application. This review focuses on the recent developments on the application in PAMAM dendrimers as effective carriers for drug and gene (pDNA, siRNA) delivery in cancer therapy, including: a) PAMAM for anticancer drug delivery; b) PAMAM and gene therapy; c) PAMAM used in overcoming tumor multidrug resistance; d) PAMAM used for hybrid nanoparticles; and e) PAMAM linked or loaded in other nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

Development of cadmium-free quantum dot for intracellular labelling through electroporation or lipid-calcium-phosphate

NASA Astrophysics Data System (ADS)

Liu, Ying-Feng; Hung, Wei-Ling; Hou, Tzh-Yin; Huang, Hsiu-Ying; Lin, Cheng-An J.

2016-04-01

Traditional fluorescent labelling techniques has severe photo-bleaching problem such as organic dyes and fluorescent protein. Quantum dots made up of traditional semiconductor (CdSe/ZnS) material has sort of biological toxicity. This research has developed novel Cd-free quantum dots divided into semiconductor (Indium phosphide, InP) and noble metal (Gold). Former has lower toxicity compared to traditional quantum dots. Latter consisting of gold (III) chloride (AuCl3) and toluene utilizes sonochemical preparation and different stimulus to regulate fluorescent wavelength. Amphoteric macromolecule surface technology and ligand Exchange in self-Assembled are involved to develop hydrophilic nanomaterials which can regulate the number of grafts per molecule of surface functional groups. Calcium phosphate (CaP) nanoparticle (NP) with an asymmetric lipid bilayer coating technology developed for intracellular delivery and labelling has synthesized Cd-free quantum dots possessing high brightness and multi-fluorescence successfully. Then, polymer coating and ligand exchange transfer to water-soluble materials to produce liposome nanomaterials as fluorescent probes and enhancing medical applications of nanotechnology.

Illumination of growth, division and secretion by metabolic labeling of the bacterial cell surface

PubMed Central

Siegrist, M. Sloan; Swarts, Benjamin M.; Fox, Douglas M.; Lim, Shion An; Bertozzi, Carolyn R.

2015-01-01

The cell surface is the essential interface between a bacterium and its surroundings. Composed primarily of molecules that are not directly genetically encoded, this highly dynamic structure accommodates the basic cellular processes of growth and division as well as the transport of molecules between the cytoplasm and the extracellular milieu. In this review, we describe aspects of bacterial growth, division and secretion that have recently been uncovered by metabolic labeling of the cell envelope. Metabolite derivatives can be used to label a variety of macromolecules, from proteins to non-genetically-encoded glycans and lipids. The embedded metabolite enables precise tracking in time and space, and the versatility of newer chemoselective detection methods offers the ability to execute multiple experiments concurrently. In addition to reviewing the discoveries enabled by metabolic labeling of the bacterial cell envelope, we also discuss the potential of these techniques for translational applications. Finally, we offer some guidelines for implementing this emerging technology. PMID:25725012

Reactive pathways of hydrogen and carbon removal from organosilicate glass low- κ films by F atoms

NASA Astrophysics Data System (ADS)

Voronina, Ekaterina N.; Mankelevich, Yuri A.; Rakhimova, Tatyana V.

2017-07-01

Direct molecular dynamic simulation on the base of the density functional theory (DFT) method is used to study some critical reactions of F atoms with organosilicate glass (OSG) low-κ films. Here static and dynamic DFT-based approaches are applied for a variety of reactive pathways of hydrogen and carbon removal in the form of volatile products (HF, CF2 and CF3 molecules) from initial SiCH3 surface groups. These reactions constitute an important part of the proposed multi-step mechanism of OSG films damage and etching by thermal F atoms. Two models (POSS and TMCTS macromolecules and their modifications) are used to illustrate the peculiarities and dynamics of the successive reactions of F atoms with the initial SiCH3 and appeared SiCHxFy (x + y ≤ 3) surface groups. Contribution to the Topical Issue "Dynamics of Molecular Systems (MOLEC 2016)", edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

Biocompatibility of cluster-assembled nanostructured TiO2 with primary and cancer cells.

PubMed

Carbone, Roberta; Marangi, Ida; Zanardi, Andrea; Giorgetti, Luca; Chierici, Elisabetta; Berlanda, Giuseppe; Podestà, Alessandro; Fiorentini, Francesca; Bongiorno, Gero; Piseri, Paolo; Pelicci, Pier Giuseppe; Milani, Paolo

2006-06-01

We have characterized the biocompatibility of nanostructured TiO2 films produced by the deposition of a supersonic beam of TiOx clusters. Physical analysis shows that these films possess, at the nanoscale, a granularity and porosity mimicking those of typical extracellular matrix structures and adsorption properties that could allow surface functionalization with different macromolecules such as DNA, proteins, and peptides. To explore the biocompatibility of this novel nanostructured surface, different cancer and primary cells were analyzed in terms of morphological appearance (by bright field microscopy and immunofluorescence) and growth properties, with the aim to evaluate cluster-assembled TiO2 films as substrates for cell-based and tissue-based applications. Our results strongly suggest that this new biomaterial supports normal growth and adhesion of primary and cancer cells with no need for coating with ECM proteins; we thus propose this new material as an optimal substrate for different applications in cell-based assays, biosensors or microfabricated medical devices.