An efficient, cost effective, sensing behaviour liquid-liquid extraction and spectrophotometric determination of copper(II) incorporated with 4-(4‧-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole: Analysis of food samples, leafy vegetables, fertilizers and environmental samples

NASA Astrophysics Data System (ADS)

Barache, Umesh B.; Shaikh, Abdul B.; Lokhande, Tukaram N.; Kamble, Ganesh S.; Anuse, Mansing A.; Gaikwad, Shashikant H.

2018-01-01

The aim of the present work is to develop an efficient, simple and selective moreover cost-effective method for the extractive spectrophotometric determination of copper(II) by using the Schiff base 4-(4‧-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole [CBIMMT]. This chromogenic reagent forms a yellow coloured complex with copper(II) in acetate buffer at pH 4.2. The copper(II) complex with ligand is instantly extracted into chloroform and shows a maximum absorbance at 414 nm which remains stable for > 48 h. The composition of extracted complex is found to be 1:2 [copper(II): reagent] which was ascertained using Job's method of continuous variation, mole ratio method and slope ratio method. Under optimal conditions, the copper(II) complex in chloroform adheres to Beer's law up to 17.5 μg mL- 1 of copper(II). The optimum concentration range obtained from Ringbom's plot is from 5 μg mL- 1 to 17.5 μg mL- 1. The molar absorptivity, Sandell's sensitivity and enrichment factor of the extracted copper(II) chelate are 0.33813 × 104 L mol- 1 cm- 1, 0.01996 μg cm- 2 and 2.49 respectively. In the extraction of copper(II), several affecting factors including the solution pH, ligand concentration, equilibrium time, effect of foreign ions are optimized. The interfering effects of various cations and anions were also studied and use of masking agents enhances the selectivity of the method. The chromogenic sulphur containing reagent, 4-(4‧-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole has been synthesized in a single step with high purity and yield. The synthesized reagent has been successfully applied first time for determination of copper(II). The reagent forms stable chelate with copper(II) in buffer medium instantly and quantitatively extracted in chloroform within a minute. The method is successfully applied for the determination of copper(II) in various synthetic mixtures, complexes, fertilizers, environmental samples such as food samples, leafy vegetables, and water samples. The results are compared with those obtained with a reference procedure. Good agreement was attained. All the obtained results are indicative of a convenient, fast method for the extraction and quantification of micro levels of copper(II) from various environmental matrices without use of sophisticated instrumentation and procedure. The method showed a relative standard deviation of 0.42%.

An efficient, cost effective, sensing behaviour liquid-liquid extraction and spectrophotometric determination of copper(II) incorporated with 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole: Analysis of food samples, leafy vegetables, fertilizers and environmental samples.

PubMed

Barache, Umesh B; Shaikh, Abdul B; Lokhande, Tukaram N; Kamble, Ganesh S; Anuse, Mansing A; Gaikwad, Shashikant H

2018-01-15

The aim of the present work is to develop an efficient, simple and selective moreover cost-effective method for the extractive spectrophotometric determination of copper(II) by using the Schiff base 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole [CBIMMT]. This chromogenic reagent forms a yellow coloured complex with copper(II) in acetate buffer at pH4.2. The copper(II) complex with ligand is instantly extracted into chloroform and shows a maximum absorbance at 414nm which remains stable for >48h. The composition of extracted complex is found to be 1:2 [copper(II): reagent] which was ascertained using Job's method of continuous variation, mole ratio method and slope ratio method. Under optimal conditions, the copper(II) complex in chloroform adheres to Beer's law up to 17.5μgmL -1 of copper(II). The optimum concentration range obtained from Ringbom's plot is from 5μgmL -1 to 17.5μgmL -1 . The molar absorptivity, Sandell's sensitivity and enrichment factor of the extracted copper(II) chelate are 0.33813×10 4 Lmol -1 cm -1 , 0.01996μgcm -2 and 2.49 respectively. In the extraction of copper(II), several affecting factors including the solution pH, ligand concentration, equilibrium time, effect of foreign ions are optimized. The interfering effects of various cations and anions were also studied and use of masking agents enhances the selectivity of the method. The chromogenic sulphur containing reagent, 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole has been synthesized in a single step with high purity and yield. The synthesized reagent has been successfully applied first time for determination of copper(II). The reagent forms stable chelate with copper(II) in buffer medium instantly and quantitatively extracted in chloroform within a minute. The method is successfully applied for the determination of copper(II) in various synthetic mixtures, complexes, fertilizers, environmental samples such as food samples, leafy vegetables, and water samples. The results are compared with those obtained with a reference procedure. Good agreement was attained. All the obtained results are indicative of a convenient, fast method for the extraction and quantification of micro levels of copper(II) from various environmental matrices without use of sophisticated instrumentation and procedure. The method showed a relative standard deviation of 0.42%. Copyright © 2017 Elsevier B.V. All rights reserved.

Complex amine-based reagents

NASA Astrophysics Data System (ADS)

Suslov, S. Yu.; Kirilina, A. V.; Sergeev, I. A.; Zezyulya, T. V.; Sokolova, E. A.; Eremina, E. V.; Timofeev, N. V.

2017-03-01

Amines for a long time have been applied to maintaining water chemistry conditions (WCC) at power plants. However, making use of complex reagents that are the mixture of neutralizing and the filmforming amines, which may also contain other organic components, causes many disputes. This is mainly due to lack of reliable information about these components. The protective properties of any amine with regard to metal surfaces depend on several factors, which are considered in this article. The results of applying complex reagents to the protection of heating surfaces in industrial conditions and estimated behavior forecasts for various reagents under maintaining WCC on heat-recovery boilers with different thermal circuits are presented. The case of a two-drum heat-recovery boiler with in-line drums was used as an example, for which we present the calculated pH values for various brands of reagents under the same conditions. Work with different reagent brands and its analysis enabled us to derive a composition best suitable for the conditions of their practical applications in heat-recovery boilers at different pressures. Testing the new amine reagent performed at a CCPP power unit shows that this reagent is an adequate base for further development of reagents based on amine compounds. An example of testing a complex reagent is shown created with the participation of the authors within the framework the program of import substitution and its possible use is demonstrated for maintaining WCC of power-generating units of combined-cycle power plants (CCPP) and TPP. The compliance of the employed reagents with the standards of water chemistry conditions and protection of heating surfaces were assessed. The application of amine-containing reagents at power-generating units of TPP makes it possible to solve complex problems aimed at ensuring the sparing cleaning of heating surfaces from deposits and the implementation of conservation and management of water chemistry condition on the TPP equipment.

Analytical studies on the charge transfer complexes of loperamide hydrochloride and trimebutine drugs. Spectroscopic and thermal characterization of CT complexes.

PubMed

Elqudaby, Hoda M; Mohamed, Gehad G; El-Din, Ghada M G

2014-08-14

Charge transfer complexes of loperamide hydrochloride (LOP.HCl) and trimebutine (TB) drugs as electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors in acetonitrile were investigated spectrophotometrically to determine the cited drugs in pure and dosage forms. The reaction gives highly coloured complex species which are measured spectrophotometrically at 460, 415 and 842nm in case of LOP.HCl and at 455, 414 and 842nm in case of TB using DDQ, TCNE and TCNQ reagents, respectively. The optimum experimental conditions have been studied carefully and optimized. Beer's law was obeyed over the concentration ranges of 47.70-381.6, 21.50-150.5 and 10.00-100.0μgmL(-1) for LOP.HCl and 37.85-264.9, 38.75-310.0 and 7.75-155.0μgmL(-1) for TB using DDQ, TCNE and TCNQ reagents, respectively. Sandell sensitivity, standard deviation, relative standard deviation, limit of detection and quantification were calculated. The obtained data refer to high accuracy and precision of the proposed method. These results are also confirmed by inter and intra-day precision with percent recovery of 99.18-101.1% and 99.32-101.4% in case of LOP.HCl and 98.00-102.0% and 97.50-101.4% in case of TB using DDQ, TCNE and TCNQ reagents for intra- and inter-day, respectively. These data were compared with those obtained using official methods for the determination of the cited drugs. The stability constants of the CT complexes were determined. The final products of the reaction were isolated and characterized using FT-IR, (1)H NMR, elemental analysis and thermogravimetric analysis (TG). The stoichiometry and apparent formation constant of the complexes formed were determined by applying the conventional spectrophotometric molar ratio method. Copyright © 2014 Elsevier B.V. All rights reserved.

A Sulfhydryl-Reactive Ruthenium (II) Complex and Its Conjugation to Protein G as a Universal Reagent for Fluorescent Immunoassays

PubMed Central

Goud, Thirumani Venkatshwar; Huang, Bor-Rong; Lin, Tzu-Chau; Biellmann, Jean-François; Chen, Chien-Sheng

2012-01-01

To develop a fluorescent ruthenium complex for biosensing, we synthesized a novel sulfhydryl-reactive compound, 4-bromophenanthroline bis-2,2′-dipyridine Ruthenium bis (hexafluorophosphate). The synthesized Ru(II) complex was crosslinked with thiol-modified protein G to form a universal reagent for fluorescent immunoassays. The resulting Ru(II)-protein G conjugates were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The emission peak wavelength of the Ru(II)-protein G conjugate was 602 nm at the excitation of 452 nm which is similar to the spectra of the Ru(II) complex, indicating that Ru(II)-protein G conjugates still remain the same fluorescence after conjugation. To test the usefulness of the conjugate for biosensing, immunoglobulin G (IgG) binding assay was conducted. The result showed that Ru(II)-protein G conjugates were capable of binding IgG and the more cross-linkers to modify protein G, the higher conjugation efficiency. To demonstrate the feasibility of Ru(II)-protein G conjugates for fluorescent immunoassays, the detection of recombinant histidine-tagged protein using the conjugates and anti-histidine antibody was developed. The results showed that the histidine-tagged protein was successfully detected with dose-response, indicating that Ru(II)-protein G conjugate is a useful universal fluorescent reagent for quantitative immunoassays. PMID:22563441

The effects of the NMR shift-reagents Dy(PPP)2, Dy(TTHA) and Tm(DOTP) on developed pressure in isolated perfused rat hearts. The role of shift-reagent calcium complexes.

PubMed

Gaszner, B; Simor, T; Hild, G; Elgavish, G A

2001-11-01

The 23Na NMR shift-reagent complexes (Dy(PPP)2, Dy(TTHA), and Tm(DOTP)) bind stoichiometric amounts of Ca2+. Thus, in perfused rat heart systems, a supplementation of Ca2+ is required to maintain the requisite extracellular free calcium concentration ([Ca(o)]f) and to approximate a physiological level of contractile function. The amount of reagent-bound Ca2+ in a heart perfusate that contains a shift-reagent depends on: (1) Ca2+ binding by excess ligand used during the preparation of the shift-reagent; and (2) the Ca2+ binding affinity of the shift-reagent. To address point 1), we introduced a 1H and 31P NMR spectroscopic titration method to quantify directly the concentration of the excess ligand. We also used this method to minimize the amount of excess ligand (L) and thus the amount of Ca*L complex. To address point (2), we determined the stepwise Kd (microm) values of the Ca complexes of the three shift-reagents.: Dy(PPP)2, Kd=0.09, Kd2=7.9; Dy(TTHA), Kd1=10.66, Kd2=10.12; and Tm(DOTP), K(d1)=0.502, Kd2=4.98. The Kd values of the Ca complexes of the phosphonate and triphosphate based shift-reagents, Tm(DOTP) and Dy(PPP)2, respectively, are lower than those of the polyaminocarboxylate-based Dy(TTHA), indicating stronger Ca binding affinities for the former two types of complexes. We have also shown a positive correlation between [Ca(o)]f and left ventricular developed pressure (LVDP) in perfused rat hearts. Dy(TTHA) has shown no effect on LVDP v[Ca(o)]f. The LVDP values in the presence of the phosphonate and triphosphate based shift-reagents, however, were significantly higher than expected from the [Ca(o)]f levels alone. Thus a positive inotropic effect, independent of [Ca(o)]f, is evident in the presence of Tm(DOTP) or Dy(PPP)2. Copyright 2001 Academic Press.

A new route for the synthesis of titanium silicalite-1

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

Vasile, Aurelia, E-mail: aurelia_vasile@yahoo.com; Busuioc-Tomoiaga, Alina Maria; Catalysis Research Department, ChemPerformance SRL, Iasi 700337

2012-01-15

Graphical abstract: Well-prepared TS-1 was synthesized by an innovative procedure using inexpensive reagents such as fumed silica and TPABr as structure-directing agent. This is the first time when highly crystalline TS-1 is obtained in basic medium, using sodium hydroxide as HO{sup -} ion source required for the crystallization process. Hydrolysis of titanium source has been prevented by titanium complexation with acetylacetone before structuring gel. Highlights: Black-Right-Pointing-Pointer TS-1 was obtained using cheap reagents as fumed silica and tetrapropylammonium bromide. Black-Right-Pointing-Pointer First time NaOH was used as source of OH{sup -} ions required for crystallization process. Black-Right-Pointing-Pointer The hydrolysis Ti alkoxides wasmore » controlled by Ti complexation with 2,4-pentanedione. -- Abstract: A new and efficient route using inexpensive reagents such as fumed silica and tetrapropylammonium bromide is proposed for the synthesis of titanium silicalite-1. High crystalline titanium silicalite-1 was obtained in alkaline medium, using sodium hydroxide as HO{sup -} ion source required for the crystallization process. Hydrolysis of titanium source with formation of insoluble oxide species was prevented by titanium complexation with before structuring gel. The final solids were fully characterized by powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared, ultraviolet-visible diffuse reflectance, Raman and atomic absorption spectroscopies, as well as nitrogen sorption analysis. It was found that a molar ratio Ti:Si of about 0.04 in the initial reaction mixture is the upper limit to which well formed titanium silicalite-1 with channels free of crystalline or amorphous material can be obtained. Above this value, solids with MFI type structure containing both Ti isomorphously substituted in the network and extralattice anatase nanoparticles inside of channels is formed.« less

Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea.

PubMed

Tontrong, Sopa; Khonyoung, Supada; Jakmunee, Jaroon

2012-05-01

A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al(3+) to form reddish complexes which had maximum absorption wavelength at 499.0nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0mgL(-1), with detection limit of 0.05mgL(-1) was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6mgL(-1) Al(3+) (n=11). Sample throughput of 35h(-1) was achieved with the consumption of 3mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method. Copyright © 2011 Elsevier Ltd. All rights reserved.

Gallium metal affinity capture tandem mass spectrometry for the selective detection of phosphopeptides in complex mixtures

PubMed Central

Blacken, Grady R.; Sadílek, Martin; Tureček, František

2008-01-01

Metal affinity capture tandem mass spectrometry (MAC-MSMS) is evaluated in a comparative study of a lysine-derived nitrilotriacetic acid (Nα, Nα-bis-(carboxymethyl)lysine, LysNTA) and an aspartic-acid-related iminodiacetic acid (N-(4-aminobutyl)aspartic acid, AspIDA) as selective phosphopeptide detection reagents. Both LysNTA and AspIDA spontaneously form ternary complexes with GaIII and phosphorylated amino acids and phosphopeptides upon mixing in solution. Collision-induced dissociation of positive complex ions produced by electrospray produces common fragments (LysNTA + H)+ or (AspIDA + H)+ at m/z 263 and 205, respectively. MSMS precursor scans using these fragments as reporter ions allow one to selectively detect multiple charge states of phosphopeptides in mixtures. It follows from this comparative study that LysNTA is superior to AspIDA in detecting phosphopeptides, possibly because of the higher coordination number and greater stability constant for GaIII – phosphopeptide complexation of the former reagent. In a continuing development of MAC-MSMS for proteomics applications, we demonstrate its utility in a post-column reaction format. Using a simple post-column-reaction ‘T’ and syringe pump to deliver our chelating reagents, α-casein tryptic phosphopeptides can be selectively analyzed from a solution containing a twofold molar excess of bovine serum albumin. The MAC-MSMS method is shown to be superior to the commonly used neutral loss scan for the common loss of phosphoric acid. PMID:18265438

Development of a highly sensitive and selective method for extractive spectrophotometric determination of aluminum(III) from environmental matrices, synthetic mixtures, and alloys using orthohydroxypropiophenoneisonicotinoylhydrazone.

PubMed

Ramachandraiah, C; Rajesh Kumar, J; Adinarayana Reddy, S; Lee, Jin-Young; Varada Reddy, A

2010-01-01

Orthohydroxypropiophenoneisonicotinoylhydrazone (OHPINH) is proposed as a new sensitive reagent for the spectrophotometric determination of aluminum(III). OHPINH formed a greenish-yellow colored complex with aluminum(III) in buffer solutions of pH 1 to 3. The color in pH 2 was stable for more than 48 h. The complex solution has given maximum absorbance at 390 nm when the reagent was chosen as blank and the absorbance of the reagent at this wavelength is negligible; the molar absorptivity and Sandell's sensitivity being 0.6371x10(4) L mol(-1) cm(-1) and 4.234x10(-3) microg cm(-2), respectively. The system obeys Beer's law in the range of 0.5-3.5 microg mL(-1) with excellent linearity in terms of the correlation coefficient value of 0.999. Most of the common metal ions generally found associated with aluminum(III) do not interfere. The repeatability of the method was checked by finding the relative standard deviation. The developed method has been successfully employed for the determination of aluminum(III) environmental matrices like medicinal and leafy samples, alloys, and synthetic mixtures.

Ion/Ion Reactions with "Onium" Reagents: An Approach for the Gas-phase Transfer of Organic Cations to Multiply-Charged Anions

NASA Astrophysics Data System (ADS)

Gilbert, Joshua D.; Prentice, Boone M.; McLuckey, Scott A.

2015-05-01

The use of ion/ion reactions to effect gas-phase alkylation is demonstrated. Commonly used fixed-charge "onium" cations are well-suited for ion/ion reactions with multiply deprotonated analytes because of their tendency to form long-lived electrostatic complexes. Activation of these complexes results in an SN2 reaction that yields an alkylated anion with the loss of a neutral remnant of the reagent. This alkylation process forms the basis of a general method for alkylation of deprotonated analytes generated via electrospray, and is demonstrated on a variety of anionic sites. SN2 reactions of this nature are demonstrated empirically and characterized using density functional theory (DFT). This method for modification in the gas phase is extended to the transfer of larger and more complex R groups that can be used in later gas-phase synthesis steps. For example, N-cyclohexyl- N'-(2-morpholinoethyl)carbodiimide (CMC) is used to transfer a carbodiimide functionality to a peptide anion containing a carboxylic acid. Subsequent activation yields a selective reaction between the transferred carbodiimide group and a carboxylic acid, suggesting the carbodiimide functionality is retained through the transfer process. Many different R groups are transferable using this method, allowing for new possibilities for charge manipulation and derivatization in the gas phase.

Characterization of the terminal stages of chlorophyll (ide) synthesis in etioplast membrane preparations.

PubMed Central

Griffiths, W T

1975-01-01

1. Chlorophyll (ide) formation from protochlorophyll (ide) that is normally inactive was demonstrated in etioplast membranes isolated from maize and barlley plants, the process being dependent on intermittent illumination and the addition of NADPH. 2. The addition of NADPH to the membranes was shown to result in the conversion of inactive protochlorophyll (ide) absorbing at about 630 nm into a form(s) with light-absorption maxima at about 640 and 652 nm, both of which disappear when chlorophyll (ide) is formed on illumination. 3. The temperature-dependence of the activation process and its response to a variety of reagents were examined. From these, the conclusion is drawn that -SH groups are involved in the activation but in the active complex these are unavailable for reaction with -SH reagents. 4. Evidence is presented for the occurrence of glucose 6-phosphate dehydrogenase activity within etioplasts and the suggestion is made that the oxidative pentose phosphate pathway can provide the NADPH required for chlorophyll biosynthesis during the early stages of greening. PMID:5998

Spectrophotometric Determination of Distigmine Bromide, Cyclopentolate HCl, Diaveridine HCl and Tetrahydrozoline HCl via Charge Transfer Complex Formation with TCNQ and TCNE Reagents.

PubMed

Mohamed, Gehad Genidy; Rizk, Mahmoud Sabry; Zaky Frag, Eman Yousry

2015-01-01

The purpose of this investigation was directed to propose sensitive, accurate and reproducible methods of analysis that can be applied to determine distigmine bromide (DTB), cyclopentolate hydrochloride (CPHC), diaveridine hydrochloride (DVHC) and tetrahydrozoline hydrochloride (THHC) drugs in pure form and pharmaceutical preparations via charge-transfer complex formation with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) reagents. Spectrophotometric method involve the addition a known excess of TCNQ or TCNE reagents to DTB, CPHC, DVHC and THHC drugs in acetonitrile, followed by the measurement of the absorbance of the CT complexes at the selected wavelength. The reaction stoichiometry is found to be 1:1 [drug]: [TCNQ or TCNE]. The absorbance is found to increase linearly with concentration of the drugs under investigation which is corroborated by the correlation coefficients of 0.9954-0.9981. The system obeys Beer's law for 6-400, 20-500, 1-180 and 60-560 µg mL(-1) and 80-600, 10-300, 1-60 and 80-640 µg mL(-1) for DTB, CPHC, DVHC and THHC drugs using TCNQ and TCNE reagents, respectively. The apparent molar absorptivity, sandell sensitivity, the limits of detection and quantification are also reported for the spectrophotometric method. Intra- and inter-day precision and accuracy of the method were evaluated as per ICH guidelines. The method was successfully applied to the assay of DTB, CPHC, DVHC and THHC drugs in formulations and the results were compared with those of a reference method by applying Student's t and F-tests. No interference was observed from common pharmaceutical excipients.

Spectrophotometric Determination of Distigmine Bromide, Cyclopentolate HCl, Diaveridine HCl and Tetrahydrozoline HCl via Charge Transfer Complex Formation with TCNQ and TCNE Reagents

PubMed Central

Mohamed, Gehad Genidy; Rizk, Mahmoud Sabry; Zaky Frag, Eman Yousry

2015-01-01

The purpose of this investigation was directed to propose sensitive, accurate and reproducible methods of analysis that can be applied to determine distigmine bromide (DTB), cyclopentolate hydrochloride (CPHC), diaveridine hydrochloride (DVHC) and tetrahydrozoline hydrochloride (THHC) drugs in pure form and pharmaceutical preparations via charge-transfer complex formation with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) reagents. Spectrophotometric method involve the addition a known excess of TCNQ or TCNE reagents to DTB, CPHC, DVHC and THHC drugs in acetonitrile, followed by the measurement of the absorbance of the CT complexes at the selected wavelength. The reaction stoichiometry is found to be 1:1 [drug]: [TCNQ or TCNE]. The absorbance is found to increase linearly with concentration of the drugs under investigation which is corroborated by the correlation coefficients of 0.9954-0.9981. The system obeys Beer’s law for 6-400, 20-500, 1-180 and 60-560 µg mL-1 and 80-600, 10-300, 1-60 and 80-640 µg mL-1 for DTB, CPHC, DVHC and THHC drugs using TCNQ and TCNE reagents, respectively. The apparent molar absorptivity, sandell sensitivity, the limits of detection and quantification are also reported for the spectrophotometric method. Intra- and inter-day precision and accuracy of the method were evaluated as per ICH guidelines. The method was successfully applied to the assay of DTB, CPHC, DVHC and THHC drugs in formulations and the results were compared with those of a reference method by applying Student’s t and F-tests. No interference was observed from common pharmaceutical excipients. PMID:26330858

Structural study of complexes formed by acidic and neutral organophosphorus reagents

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

Braatz, Alexander D.; Antonio, Mark R.; Nilsson, Mikael

The coordination of the trivalent 4f ions, Ln = La 3+, Dy 3+, and Lu 3+, with neutral and acidic organophosphorus reagents, both individually and combined, was studied by use of X-ray absorption spectroscopy. These studies provide metrical information about the interatomic interactions between these cations and the ligands tri- n-butyl phosphate (TBP) and di- n-butyl phosphoric acid (HDBP), whose behavior are of practical importance to chemical separation processes that are currently used on an industrial scale. Previous studies have suggested the existence of complexes involving a mixture of ligands, accounting for extraction synergy. Through systematic variation of the aqueousmore » phase acidity and extractant concentration and combination, we have found that complexes with Ln and TBP : HDBP at any mixture and HDBP alone involve direct Ln–O interactions involving 6 oxygen atoms and distant Ln–P interactions involving on average 3–5 phosphorus atoms per Ln ion. It was also found that Ln complexes formed by TBP alone seem to favor eight oxygen coordination, though we were unable to obtain metrical results regarding the distant Ln–P interactions due to the low signal attributed to a lower concentration of Ln ions in the organic phases. Our study does not support the existence of mixed Ln–TBP–HDBP complexes but, rather, indicates that the lanthanides are extracted as either Ln–HDBP complexes or Ln–TBP complexes and that these complexes exist in different ratios depending on the conditions of the extraction system. Furthermore, this fundamental structural information offers insight into the solvent extraction processes that are taking place and are of particular importance to issues arising from the separation and disposal of radioactive materials from used nuclear fuel.« less

Structural study of complexes formed by acidic and neutral organophosphorus reagents

DOE PAGES

Braatz, Alexander D.; Antonio, Mark R.; Nilsson, Mikael

2016-12-23

The coordination of the trivalent 4f ions, Ln = La 3+, Dy 3+, and Lu 3+, with neutral and acidic organophosphorus reagents, both individually and combined, was studied by use of X-ray absorption spectroscopy. These studies provide metrical information about the interatomic interactions between these cations and the ligands tri- n-butyl phosphate (TBP) and di- n-butyl phosphoric acid (HDBP), whose behavior are of practical importance to chemical separation processes that are currently used on an industrial scale. Previous studies have suggested the existence of complexes involving a mixture of ligands, accounting for extraction synergy. Through systematic variation of the aqueousmore » phase acidity and extractant concentration and combination, we have found that complexes with Ln and TBP : HDBP at any mixture and HDBP alone involve direct Ln–O interactions involving 6 oxygen atoms and distant Ln–P interactions involving on average 3–5 phosphorus atoms per Ln ion. It was also found that Ln complexes formed by TBP alone seem to favor eight oxygen coordination, though we were unable to obtain metrical results regarding the distant Ln–P interactions due to the low signal attributed to a lower concentration of Ln ions in the organic phases. Our study does not support the existence of mixed Ln–TBP–HDBP complexes but, rather, indicates that the lanthanides are extracted as either Ln–HDBP complexes or Ln–TBP complexes and that these complexes exist in different ratios depending on the conditions of the extraction system. Furthermore, this fundamental structural information offers insight into the solvent extraction processes that are taking place and are of particular importance to issues arising from the separation and disposal of radioactive materials from used nuclear fuel.« less

Nickel-catalyzed coupling reaction of alkyl halides with aryl Grignard reagents in the presence of 1,3-butadiene: mechanistic studies of four-component coupling and competing cross-coupling reactions† †Electronic supplementary information (ESI) available: Detailed experimental and computational results, procedures, characterization data, copies of NMR charts, and crystallographic data. CCDC 1572238. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04675h

PubMed Central

Fukuoka, Asuka; Yokoyama, Wataru; Min, Xin; Hisaki, Ichiro; Kuniyasu, Hitoshi

2018-01-01

We describe the mechanism, substituent effects, and origins of the selectivity of the nickel-catalyzed four-component coupling reactions of alkyl fluorides, aryl Grignard reagents, and two molecules of 1,3-butadiene that affords a 1,6-octadiene carbon framework bearing alkyl and aryl groups at the 3- and 8-positions, respectively, and the competing cross-coupling reaction. Both the four-component coupling reaction and the cross-coupling reaction are triggered by the formation of anionic nickel complexes, which are generated by the oxidative dimerization of two molecules of 1,3-butadiene on Ni(0) and the subsequent complexation with the aryl Grignard reagents. The C–C bond formation of the alkyl fluorides with the γ-carbon of the anionic nickel complexes leads to the four-component coupling product, whereas the cross-coupling product is yielded via nucleophilic attack of the Ni center toward the alkyl fluorides. These steps are found to be the rate-determining and selectivity-determining steps of the whole catalytic cycle, in which the C–F bond of the alkyl fluorides is activated by the Mg cation rather than a Li or Zn cation. ortho-Substituents of the aryl Grignard reagents suppressed the cross-coupling reaction leading to the selective formation of the four-component products. Such steric effects of the ortho-substituents were clearly demonstrated by crystal structure characterizations of ate complexes and DFT calculations. The electronic effects of the para-substituent of the aryl Grignard reagents on both the selectivity and reaction rates are thoroughly discussed. The present mechanistic study offers new insight into anionic complexes, which are proposed as the key intermediates in catalytic transformations even though detailed mechanisms are not established in many cases, and demonstrates their synthetic utility as promising intermediates for C–C bond forming reactions, providing useful information for developing efficient and straightforward multicomponent reactions. PMID:29719693

Reclamation with Recovery of Radionuclides and Toxic Metals from Contaminated Materials, Soils, and Wastes

NASA Technical Reports Server (NTRS)

Francis, A. J.; Dodge, C. J.

1993-01-01

A process has been developed at Brookhaven National Laboratory (BNL) for the removal of metals and radionuclides from contaminated materials, soils, and waste sites. In this process, citric acid, a naturally occurring organic complexing agent, is used to extract metals such as Ba, Cd, Cr, Ni, Zn, and radionuclides Co, Sr, Th, and U from solid wastes by formation of water soluble, metal-citrate complexes. Citric acid forms different types of complexes with the transition metals and actinides, and may involve formation of a bidentate, tridentate, binuclear, or polynuclear complex species. The extract containing radionuclide/metal complex is then subjected to microbiological degradation followed by photochemical degradation under aerobic conditions. Several metal citrate complexes are biodegraded, and the metals are recovered in a concentrated form with the bacterial biomass. Uranium forms binuclear complex with citric acid and is not biodegraded. The supernatant containing uranium citrate complex is separated and upon exposure to light, undergoes rapid degradation resulting in the formation of an insoluble, stable polymeric form of uranium. Uranium is recovered as a precipitate (polyuranate) in a concentrated form for recycling or for appropriate disposal. This treatment process, unlike others which use caustic reagents, does not create additional hazardous wastes for disposal and causes little damage to soil which can then be returned to normal use.

Kinetically Controlled Vapor-Diffusion Synthesis of Novel Nanostructured Metal Hydroxide and Phosphate Films using no Organic Reagents

DTIC Science & Technology

2005-11-01

Ga2O3 . 7 In these studies, silicatein (a catalytically active, structure-directing enzyme8) was used as a catalyst and template for the hydrolysis...and subsequent polycondensation of water stable molecular complexes of titanium and gallium to form nanocrystalline TiO2 6 and Ga2O3 , 7 respectively

Spectrophotometric determination of fenoprofen calcium drug in pure and pharmaceutical preparations. Spectroscopic characterization of the charge transfer solid complexes

NASA Astrophysics Data System (ADS)

Mohamed, Marwa E.; Frag, Eman Y. Z.; Hathoot, Abla A.; Shalaby, Essam A.

2018-01-01

Simple, accurate and robust spectrophotometric method was developed for determination of fenoprofen calcium drug (FPC). The proposed method was based on the charge transfer (CT) reaction of FPC drug (as n-electron donor) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,6-trinitrophenol (picric acid, PA) or 1,2,5,8-tetrahydroxyanthraquinone (Quinalizarin, QZ) (as π-acceptors) to give highly colored charge transfer complexes. Different variables affecting the reaction such as reagent concentration, temperature and time have been carefully optimized to achieve the highest sensitivity. Beer's law was obeyed over the concentration ranges of 2-60, 0.6-90 and 4-30 μg mL- 1 using DDQ, PA and QZ CT reagents, respectively, with correlation coefficients of 0.9986, 0.9989 and 0.997 and detection limits of 1.78, 0.48 and 2.6 μg mL- 1 for the CT reagents in the same order. Elucidation of the chemical structure of the solid CT complexes formed via reaction between the drug under study and π-acceptors was done using elemental, thermal analyses, IR, 1H NMR and mass spectrometry. X-ray diffraction was used to estimate the crystallinity of the CT complexes. Their biological activities were screened against different bacterial and fungal organisms. The method was applied successfully with satisfactory results for the determination of FPC drug in fenoprofen capsules. The method was validated with respect to linearity, limit of detection and quantification, inter- and intra-days precision and accuracy. The proposed method gave comparable results with the official method.

A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent

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

Gao, Xue-Miao; Guo, Qian; Zhao, Jiong-Peng, E-mail: horryzhao@yahoo.com

A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D frameworkmore » with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.« less

Quercetin as colorimetric reagent for determination of zirconium

USGS Publications Warehouse

Grimaldi, F.S.; White, C.E.

1953-01-01

Methods described in the literature for the determination of zirconium are generally designed for relatively large amounts of this element. A good procedure using colorimetric reagent for the determination of trace amounts is desirable. Quercetin has been found to yield a sensitive color reaction with zirconium suitable for the determination of from 0.1 to 50?? of zirconium dioxide. The procedure developed involves the separation of zirconium from interfering elements by precipitation with p-dimethylaminoazophenylarsonic acid prior to its estimation with quercetin. The quercetin reaction is carried out in 0.5N hydrochloric acid solution. Under the operating conditions it is indicated that quercetin forms a 2 to 1 complex with zirconium; however, a 2 to 1 and a 1 to 1 complex can coexist under special conditions. Approximate values for the equilibrium constants of the complexes are K1 = 0.33 ?? 10-5 and K2 = 1.3 ?? 10-9. Seven Bureau of Standards samples of glass sands and refractories were analyzed with excellent results. The method described should find considerable application in the analysis of minerals and other materials for macro as well as micro amounts of zirconium.

Spectrophotometric study of the thorium-morin mixed-color system

USGS Publications Warehouse

Fletcher, M.H.; Milkey, R.G.

1956-01-01

A spectrophotometric study was made of the thoriummorin reaction to evaluate the suitability of morin as a reagent for the determination of trace amounts of thorium. At pH 2, the equilibrium constant for the reaction is 1 ?? 106, and a single complex having a thorium-morin ratio of 1 to 2 is formed. The complex shows maximum absorbance at a wave length of 410 m??, and its absorbance obeys Beer's law. The absorbance readings are highly reproducible, and the sensitivity is relatively high, an absorbance difference of 0.001 being equivalent to 0.007 ?? of ThO2 per sq. cm. The effects of acid, alcohol, and morin concentration, time, temperature, and age of the morin reagent as well as the behavior of morin with zirconium(IV), iron(III), aluminum(III), ytterbium(III), yttrium(III), uranium(VI), praseodymium(III), lead(II), lanthanum(III), and calcium(II) ions are discussed. A method is presented for the determination of thorium in pure solutions. Appropriate separations for the isolation of thorium may extend the usefulness of the method and permit the determination of trace amounts of thorium in complex materials.

Gel-forming reagents and uses thereof for preparing microarrays

DOEpatents

Golova, Julia; Chernov, Boris; Perov, Alexander

2010-11-09

New gel-forming reagents including monomers and cross-linkers, which can be applied to gel-drop microarray manufacturing by using co-polymerization approaches are disclosed. Compositions for the preparation of co-polymerization mixtures with new gel-forming monomers and cross-linker reagents are described herein. New co-polymerization compositions and cross-linkers with variable length linker groups between unsaturated C.dbd.C bonds that participate in the formation of gel networks are disclosed.

Hemoglobin and Myoglobin as Reducing Agents in Biological Systems. Redox Reactions of Globins with Copper and Iron Salts and Complexes.

PubMed

Postnikova, G B; Shekhovtsova, E A

2016-12-01

In addition to reversible O2 binding, respiratory proteins of the globin family, hemoglobin (Hb) and myoglobin (Mb), participate in redox reactions with various metal complexes, including biologically significant ones, such as those of copper and iron. HbO 2 and MbO 2 are present in cells in large amounts and, as redox agents, can contribute to maintaining cell redox state and resisting oxidative stress. Divalent copper complexes with high redox potentials (E 0 , 200-600 mV) and high stability constants, such as [Cu(phen) 2 ] 2+ , [Cu(dmphen) 2 ] 2+ , and CuDTA oxidize ferrous heme proteins by the simple outer-sphere electron transfer mechanism through overlapping π-orbitals of the heme and the copper complex. Weaker oxidants, such as Cu2+, CuEDTA, CuNTA, CuCit, CuATP, and CuHis (E 0 ≤ 100-150 mV) react with HbO 2 and MbO 2 through preliminary binding to the protein with substitution of the metal ligands with protein groups and subsequent intramolecular electron transfer in the complex (the site-specific outer-sphere electron transfer mechanism). Oxidation of HbO 2 and MbO 2 by potassium ferricyanide and Fe(3) complexes with NTA, EDTA, CDTA, ATP, 2,3-DPG, citrate, and pyrophosphate PP i proceeds mainly through the simple outer-sphere electron transfer mechanism via the exposed heme edge. According to Marcus theory, the rate of this reaction correlates with the difference in redox potentials of the reagents and their self-exchange rates. For charged reagents, the reaction may be preceded by their nonspecific binding to the protein due to electrostatic interactions. The reactions of LbO 2 with carboxylate Fe complexes, unlike its reactions with ferricyanide, occur via the site-specific outer-sphere electron transfer mechanism, even though the same reagents oxidize structurally similar MbO 2 and cytochrome b 5 via the simple outer-sphere electron transfer mechanism. Of particular biological interest is HbO 2 and MbO 2 transformation into met-forms in the presence of small amounts of metal ions or complexes (catalysis), which, until recently, had been demonstrated only for copper compounds with intermediate redox potentials. The main contribution to the reaction rate comes from copper binding to the "inner" histidines, His97 (0.66 nm from the heme) that forms a hydrogen bond with the heme propionate COO - group, and the distal His64. The affinity of both histidines for copper is much lower than that of the surface histidines residues, and they are inaccessible for modification with chemical reagents. However, it was found recently that the high-potential Fe(3) complex, potassium ferricyanide (400 mV), at a 5 to 20% of molar protein concentration can be an efficient catalyst of MbO 2 oxidation into metMb. The catalytic process includes binding of ferrocyanide anion in the region of the His119 residue due to the presence there of a large positive local electrostatic potential and existence of a "pocket" formed by Lys16, Ala19, Asp20, and Arg118 that is sufficient to accommodate [Fe(CN) 6 ] 4- . Fast, proton-assisted reoxidation of the bound ferrocyanide by oxygen (which is required for completion of the catalytic cycle), unlike slow [Fe(CN) 6 ] 4- oxidation in solution, is provided by the optimal location of neighboring protonated His113 and His116, as it occurs in the enzyme active site.

A novel flow injection spectrophotometric method using plant extracts as green reagent for the determination of doxycycline

NASA Astrophysics Data System (ADS)

Palamy, Sysay; Ruengsitagoon, Wirat

2017-01-01

A novel flow injection spectrophotometric method was developed for the determination of doxycycline in pharmaceutical preparations using iron(III) contained in extracts from plants. The assay was based on the complex formed between doxycycline and iron(III) characterized by an absorption maximum at 435 nm. The calibration graphs obtained over the doxycycline concentration range 5-250 μg mL- 1 gave correlation coefficients of 0.9979, 0.9987 and 0.9987 with the three green reagents prepared from Senna alata (L.) Roxb. (S. alata), Polygonum hydropiper L. (P. hydropiper) or Diplazium esculentum (Retz.) Sw. (D. esculentum), respectively. The relative standard deviations of the repeatability was < 2.00%. The percentage recoveries were in the range of 98.27-101.03%. Doxycycline contents obtained by this new method and by the reference methods reported in literature were in agreement at 95% confidence level with the paired t-test. The sample throughput was 36 h- 1 for each green reagent.

Highly catalytic asymmetric addition of deactivated alkyl grignard reagents to aldehydes.

PubMed

Da, Chao-Shan; Wang, Jun-Rui; Yin, Xiao-Gang; Fan, Xin-Yuan; Liu, Yi; Yu, Sheng-Li

2009-12-17

Generally used and highly reactive RMgBr reagents were effectively deactivated by bis[2-(N,N-dimethylamino)ethyl] ether and then were employed in the highly enantioselective addition of Grignard reagents to aldehydes. The reaction was catalyzed by the complex of commercially available (S)-BINOL and Ti(O(i-)Pr)(4) under mild conditions. Compared with the other observed Grignard reagents, alkyl Grignard reagents showed higher enantioselectivity and they achieved >99% ee.

Solar photolysis of water

NASA Technical Reports Server (NTRS)

Ryason, P. R. (Inventor)

1978-01-01

A cyclic process is described for the solar photolysis of water, including a first stage in which water is reduced in the presence of a Eu(+2) photooxidizable reagent producing hydrogen and spent oxidized Eu(+3) reagent. The spent reagent Eu(+3) is reduced by means of a transition metal ligand complex reductant, RuL(+3) in a photoexcited state, such as a ruthenium pyridyl complex. Due to competing reactions between the photolysis and regeneration products, the photooxidation reaction must be separated from the regeneration in space and time by supporting the reagent and/or the reductant on solid supports and utilizing pH, wavelength and flow control to maximize hydrogen and oxygen production.

Homologation chemistry with nucleophilic α-substituted organometallic reagents: chemocontrol, new concepts and (solved) challenges.

PubMed

Castoldi, Laura; Monticelli, Serena; Senatore, Raffaele; Ielo, Laura; Pace, Vittorio

2018-05-31

The transfer of a reactive nucleophilic CH2X unit into a preformed bond enables the introduction of a fragment featuring the exact and desired degree of functionalization through a single synthetic operation. The instability of metallated α-organometallic species often poses serious questions regarding the practicability of using this conceptually intuitive and simple approach for forming C-C or C-heteroatom bonds. A deep understanding of processes regulating the formation of these nucleophiles is a precious source of inspiration not only for successfully applying theoretically feasible transformations (i.e. determining how to employ a given reagent), but also for designing new reactions which ultimately lead to the introduction of molecular complexity via short experimental sequences.

ICC-CLASS: isotopically-coded cleavable crosslinking analysis software suite

PubMed Central

2010-01-01

Background Successful application of crosslinking combined with mass spectrometry for studying proteins and protein complexes requires specifically-designed crosslinking reagents, experimental techniques, and data analysis software. Using isotopically-coded ("heavy and light") versions of the crosslinker and cleavable crosslinking reagents is analytically advantageous for mass spectrometric applications and provides a "handle" that can be used to distinguish crosslinked peptides of different types, and to increase the confidence of the identification of the crosslinks. Results Here, we describe a program suite designed for the analysis of mass spectrometric data obtained with isotopically-coded cleavable crosslinkers. The suite contains three programs called: DX, DXDX, and DXMSMS. DX searches the mass spectra for the presence of ion signal doublets resulting from the light and heavy isotopic forms of the isotopically-coded crosslinking reagent used. DXDX searches for possible mass matches between cleaved and uncleaved isotopically-coded crosslinks based on the established chemistry of the cleavage reaction for a given crosslinking reagent. DXMSMS assigns the crosslinks to the known protein sequences, based on the isotopically-coded and un-coded MS/MS fragmentation data of uncleaved and cleaved peptide crosslinks. Conclusion The combination of these three programs, which are tailored to the analytical features of the specific isotopically-coded cleavable crosslinking reagents used, represents a powerful software tool for automated high-accuracy peptide crosslink identification. See: http://www.creativemolecules.com/CM_Software.htm PMID:20109223

Surface modification of active material structures in battery electrodes

DOEpatents

Erickson, Michael; Tikhonov, Konstantin

2016-02-02

Provided herein are methods of processing electrode active material structures for use in electrochemical cells or, more specifically, methods of forming surface layers on these structures. The structures are combined with a liquid to form a mixture. The mixture includes a surface reagent that chemically reacts and forms a surface layer covalently bound to the structures. The surface reagent may be a part of the initial liquid or added to the mixture after the liquid is combined with the structures. In some embodiments, the mixture may be processed to form a powder containing the structures with the surface layer thereon. Alternatively, the mixture may be deposited onto a current collecting substrate and dried to form an electrode layer. Furthermore, the liquid may be an electrolyte containing the surface reagent and a salt. The liquid soaks the previously arranged electrodes in order to contact the structures with the surface reagent.

21 CFR 184.1245 - Beta-carotene.

Code of Federal Regulations, 2012 CFR

2012-04-01

... either reacted to form vitamin A Wittig reagent or oxidized to vitamin A aldehyde. Vitamin A Wittig reagent and vitamin A aldehyde are reacted together to form beta-carotene. (b) The ingredient meets the...

21 CFR 184.1245 - Beta-carotene.

Code of Federal Regulations, 2013 CFR

2013-04-01

... either reacted to form vitamin A Wittig reagent or oxidized to vitamin A aldehyde. Vitamin A Wittig reagent and vitamin A aldehyde are reacted together to form beta-carotene. (b) The ingredient meets the...

21 CFR 184.1245 - Beta-carotene.

Code of Federal Regulations, 2011 CFR

2011-04-01

... either reacted to form vitamin A Wittig reagent or oxidized to vitamin A aldehyde. Vitamin A Wittig reagent and vitamin A aldehyde are reacted together to form beta-carotene. (b) The ingredient meets the...

21 CFR 184.1245 - Beta-carotene.

Code of Federal Regulations, 2010 CFR

2010-04-01

... either reacted to form vitamin A Wittig reagent or oxidized to vitamin A aldehyde. Vitamin A Wittig reagent and vitamin A aldehyde are reacted together to form beta-carotene. (b) The ingredient meets the...

Spectrophotometric determination of flucloxacillin and dicloxacillin in pure and dosage forms.

PubMed

El-Dien, F A Nour; Mohamed, Gehad G; Farag, Eman Y Z A

2006-05-01

A simple, rapid and accurate spectrophotometric method for the determination of antibiotic drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure form and different pharmaceutical preparations has been developed. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) as pi-acceptors to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions for these CT reactions have been studied carefully. Beer's law is obeyed over the concentration ranges of 4-180 microg mL(-1) and 4-70 microg mL(-1) for Fluclox and Diclox drugs using TCNQ and TCNE reagents, respectively. The Sandell sensitivities (S) are found to be 0.016-0.035 microg cm(-2) and 0.011-0.016 microg cm(-2) for Fluclox and Diclox, respectively, which indicate the high sensitivity of the proposed method. The relative standard deviations (R.S.D.: 0.08-0.49 and 0.15-0.80) for the determination of Fluclox and (R.S.D.: 0.05-0.75 and 0.13-0.75) for Diclox were obtained for four to six replicates using TCNQ and TCNE reagents, respectively, refer to the high accuracy and precision of the proposed method. These results are also confirmed by the between-day precision and the percent recovery of 99.90-100.1 and 99.60-100.4 for Fluclox and 99.90-100.5 and 99.40-100.1 for Diclox using TNCQ and TCNE reagents, respectively. The results obtained for the two reagents are comparable with those obtained by the official method.

Spectrophotometric determination of fenoprofen calcium drug in pure and pharmaceutical preparations. Spectroscopic characterization of the charge transfer solid complexes.

PubMed

Mohamed, Marwa E; Frag, Eman Y Z; Hathoot, Abla A; Shalaby, Essam A

2018-01-15

Simple, accurate and robust spectrophotometric method was developed for determination of fenoprofen calcium drug (FPC). The proposed method was based on the charge transfer (CT) reaction of FPC drug (as n-electron donor) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,6-trinitrophenol (picric acid, PA) or 1,2,5,8-tetrahydroxyanthraquinone (Quinalizarin, QZ) (as π-acceptors) to give highly colored charge transfer complexes. Different variables affecting the reaction such as reagent concentration, temperature and time have been carefully optimized to achieve the highest sensitivity. Beer's law was obeyed over the concentration ranges of 2-60, 0.6-90 and 4-30μgmL -1 using DDQ, PA and QZ CT reagents, respectively, with correlation coefficients of 0.9986, 0.9989 and 0.997 and detection limits of 1.78, 0.48 and 2.6μgmL -1 for the CT reagents in the same order. Elucidation of the chemical structure of the solid CT complexes formed via reaction between the drug under study and π-acceptors was done using elemental, thermal analyses, IR, 1 H NMR and mass spectrometry. X-ray diffraction was used to estimate the crystallinity of the CT complexes. Their biological activities were screened against different bacterial and fungal organisms. The method was applied successfully with satisfactory results for the determination of FPC drug in fenoprofen capsules. The method was validated with respect to linearity, limit of detection and quantification, inter- and intra-days precision and accuracy. The proposed method gave comparable results with the official method. Copyright © 2017 Elsevier B.V. All rights reserved.

Theoretical stusy of the reaction between 2,2',4' - trihydroxyazobenzene-5-sulfonic acid and zirconium

USGS Publications Warehouse

Fletcher, Mary H.

1960-01-01

Zirconium reacts with 2,2',4'-trihydroxyazobenzene-5-sulfonic acid in acid solutions to Form two complexes in which the ratios of dye to zirconium are 1 to 1 and 2 to 1. Both complexes are true chelates, with zirconium acting as a bridge between the two orthohydroxy dye groups. Apparent equilibrium constants for the reactions to form each of the complexes are determined. The reactions are used as a basis for the determination of the active component in the dye and a graphical method for the determination of reagent purity is described. Four absorption spectra covering the wave length region from 350 to 750 mu are given, which completely define the color system associated with the reactions in solutions where the hydrochloric acid concentration ranges from 0.0064N to about 7N.

In situ formation of phosphate barriers in soil

DOEpatents

Moore, Robert C.

2002-01-01

Reactive barriers and methods for making reactive barriers in situ in soil for sequestering soil ontaminants including actinides and heavy metals. The barrier includes phosphate, and techniques are disclosed for forming specifically apatite barriers. The method includes injecting dilute reagents into soil in proximity to a contamination plume or source such as a waste drum to achieve complete or partial encapsulation of the waste. Controlled temperature and pH facilitates rapid formation of apatite, for example, where dilute aqueous calcium chloride and dilute aqueous sodium phosphate are the selected reagents. Mixing of reagents to form precipitate is mediated and enhanced through movement of reagents in soil as a result of phenomena including capillary action, movement of groundwater, soil washing and reagent injection pressure.

[Detection of nitrite and nitrosocompounds in chemical systems and biological liquids by the calorimetric method].

PubMed

Titov, V Iu; Petrenko, Iu M; Vanin, A F; Stepuro, I I

2010-01-01

The capacity of nitrite, S-nitrosothiols (RS-NO), dinitrosyl iron complexes (DNICs) with thiol-containing ligands, and nitrosoamines to inhibit catalase has been used for the selective determination of these compounds in purely chemical systems and biological liquids: cow milk and colostram. The limiting sensitivity of the method is 50 nM. A comparison of the results of the determinations of RS-NO, DNIC, and nitrite by the catalase method and the Greese method conventionally used for nitrite detection showed that, firstly, Greese reagents decompose DNIC and RS-NO to form nitrite. Therefore, the Greese method cannot be used for nitrite determination in solutions of these substances. Secondly, Greese reagents interact with complexes of mercury ions with RS-NO, inducing the release of nitrosonium ions from the complex followed by the hydrolysis of nitrosonium to nitrite. Thus, the proposition about the spontaneous decay of the complexes of mercury ions with RS-NO is incorrect. Keeping in mind a high sensitivity of the method, the use of catalase as an enzyme detector of nitrosocompounds allows one to detect these compounds in neutral medium without prior purification of the object, thereby preventing artificial effects due to noncontrolled modifications of the compounds under study.

Probing structures of large protein complexes using zero-length cross-linking.

PubMed

Rivera-Santiago, Roland F; Sriswasdi, Sira; Harper, Sandra L; Speicher, David W

2015-11-01

Structural mass spectrometry (MS) is a field with growing applicability for addressing complex biophysical questions regarding proteins and protein complexes. One of the major structural MS approaches involves the use of chemical cross-linking coupled with MS analysis (CX-MS) to identify proximal sites within macromolecules. Identified cross-linked sites can be used to probe novel protein-protein interactions or the derived distance constraints can be used to verify and refine molecular models. This review focuses on recent advances of "zero-length" cross-linking. Zero-length cross-linking reagents do not add any atoms to the cross-linked species due to the lack of a spacer arm. This provides a major advantage in the form of providing more precise distance constraints as the cross-linkable groups must be within salt bridge distances in order to react. However, identification of cross-linked peptides using these reagents presents unique challenges. We discuss recent efforts by our group to minimize these challenges by using multiple cycles of LC-MS/MS analysis and software specifically developed and optimized for identification of zero-length cross-linked peptides. Representative data utilizing our current protocol are presented and discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

A simple and low cost dual-wavelength β-correction spectrophotometric determination and speciation of mercury(II) in water using chromogenic reagent 4-(2-thiazolylazo) resorcinol

NASA Astrophysics Data System (ADS)

Al-Bagawi, A. H.; Ahmad, W.; Saigl, Z. M.; Alwael, H.; Al-Harbi, E. A.; El-Shahawi, M. S.

2017-12-01

The most common problems in spectrophotometric determination of various complex species originate from the background spectral interference. Thus, the present study aimed to overcome the spectral matrix interference for the precise analysis and speciation of mercury(II) in water by dual-wavelength β-correction spectrophotometry using 4-(2-thiazolylazo) resorcinol (TAR) as chromogenic reagent. The principle was based on measuring the correct absorbance for the formed complex of mercury(II) ions with TAR reagent at 547 nm (lambda max). Under optimized conditions, a linear dynamic range of 0.1-2.0 μg mL- 1 with correlation coefficient (R2) of 0.997 were obtained with lower limits of detection (LOD) of 0.024 μg mL- 1 and limit of quantification (LOQ) of 0.081 μg mL- 1. The values of RSD and relative error (RE) obtained for β-correction method and single wavelength spectrophotometry were 1.3, 1.32% and 4.7, 5.9%, respectively. The method was validated in tap and sea water in terms of the data obtained from inductively coupled plasma-optical emission spectrometry (ICP-OES) using student's t and F tests. The developed methodology satisfactorily overcomes the spectral interference in trace determination and speciation of mercury(II) ions in water.

Saturated fatty acid determination method using paired ion electrospray ionization mass spectrometry coupled with capillary electrophoresis.

PubMed

Lee, Ji-Hyun; Kim, Su-Jin; Lee, Sul; Rhee, Jin-Kyu; Lee, Soo Young; Na, Yun-Cheol

2017-09-01

A sensitive and selective capillary electrophoresis-mass spectrometry (CE-MS) method for determination of saturated fatty acids (FAs) was developed by using dicationic ion-pairing reagents forming singly charged complexes with anionic FAs. For negative ESI detection, 21 anionic FAs at pH 10 were separated using ammonium formate buffer containing 40% acetonitrile modifier in normal polarity mode in CE by optimizing various parameters. This method showed good separation efficiency, but the sensitivity of the method to short-chain fatty acids was quite low, causing acetic and propionic acids to be undetectable even at 100 mgL -1 in negative ESI-MS detection. Out of the four dicationic ion-pairing reagents tested, N,N'-dibutyl 1,1'-pentylenedipyrrolidium infused through a sheath-liquid ion source during CE separation was the best reagent regarding improved sensitivity and favorably complexed with anionic FAs for detection in positive ion ESI-MS. The monovalent complex showed improved ionization efficiency, providing the limits of detection (LODs) for 15 FAs ranging from 0.13 to 2.88 μg/mL and good linearity (R 2  > 0.99) up to 150 μg/mL. Compared to the negative detection results, the effect was remarkable for the detection of short- and medium-chain fatty acids. The optimized CE-paired ion electrospray (PIESI)-MS method was utilized for the determination of FAs in cheese and coffee with simple pretreatment. This method may be extended for sensitive analysis of unsaturated fatty acids. Copyright © 2017 Elsevier B.V. All rights reserved.

Spectroscopic study of the reaction mechanism of buspirone interaction with iodine and tetracyanoethylene reagents and its applications.

PubMed

Zayed, M A; El-Habeeb, Abeer A

2009-06-01

The reactions between the drug buspirone (busp) in its base form and iodine amphoteric reagent (n-donor and/or sigma-acceptor) and with tetracyanoethylene as a pi-acceptor reagent (TCNE) have been studied spectrophotometrically at different reactant concentrations, time intervals, temperatures, and with different solvents and wavelengths, with the aim of selecting the conditions that give the most suitable molar extinction coefficients. This study aims chiefly to throw light on the nature of these reactions and to select the most proper conditions for spectrophotometric application of these reagents to determine this biologically active drug used in treating different diseases. The reaction mechanism involves the formation of busp-I(2) outer and inner sphere complexes. The separated busp-I(2) solid product obtained was investigated using elemental analyses, FT-IR, thermal analyses (TA) and electron ionization mass spectrometry (EI-MS) and was found to be biologically active. The reaction mechanism of busp-TCNE involves the formation of a charge transfer (CT) complex. The analytical parameters of the proposed spectrophotometric procedures were calculated. These procedures were applied in the analysis of busp in its formulations as a drug used to treat psychiatric illnesses. The values of the Sandell sensitivity, standard deviation (SD), relative standard deviation (RSD) and recovery percentage show the high sensitivity of these procedures. This study also presents a promising new busp-I(2) drug derivative that can be used more efficiently for the same purposes as its parent. It gives a clear idea about the possible metabolites and metabolic pathways of busp and its derivative that may occur in vivo. Copyright 2009 John Wiley & Sons, Ltd.

Assay for optical determination of biogenic amines using microtiterplates

NASA Astrophysics Data System (ADS)

Nedeljko, Polona; Turel, Matejka; Lobnik, Aleksandra

2013-05-01

Direct determination of catecholamine noradreanaline (NOR) is presented using o-phthaldialdehyde (OPA) as an indicator reagent. The fluorescent assay in which OPA forms with NOR a fluorescent complex (OPA-NOR) can be monitored at neutral, physiological conditions (pH 7) and performed in microtiterplates. The determination of NOR is optimal in the concentration range from 4.0×10-7 to 1.0×10-5 M and limit of detection is 4.0×10-7 M. The OPA-NOR complex maximum intensity is reached within 5 minutes. Dopamine and adrenaline could not be determined using the same approach.

Methods for tritium labeling

DOEpatents

Andres, Hendrik; Morimoto, Hiromi; Williams, Philip G.

1993-01-01

Reagents and processes for reductively introducing deuterium or tritium into organic molecules are described. The reagents are deuterium or tritium analogs of trialkyl boranes, borane or alkali metal aluminum hydrides. The process involves forming these reagents in situ from alkali metal tritides or deuterides.

Spectrophotometric determination of flucloxacillin and dicloxacillin in pure and dosage forms

NASA Astrophysics Data System (ADS)

El-Dien, F. A. Nour; Mohamed, Gehad G.; Farag, Eman Y. Z. A.

2006-05-01

A simple, rapid and accurate spectrophotometric method for the determination of antibiotic drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure form and different pharmaceutical preparations has been developed. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) as π-acceptors to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions for these CT reactions have been studied carefully. Beer's law is obeyed over the concentration ranges of 4-180 μg mL -1 and 4-70 μg mL -1 for Fluclox and Diclox drugs using TCNQ and TCNE reagents, respectively. The Sandell sensitivities ( S) are found to be 0.016-0.035 μg cm -2 and 0.011-0.016 μg cm -2 for Fluclox and Diclox, respectively, which indicate the high sensitivity of the proposed method. The relative standard deviations (R.S.D.: 0.08-0.49 and 0.15-0.80) for the determination of Fluclox and (R.S.D.: 0.05-0.75 and 0.13-0.75) for Diclox were obtained for four to six replicates using TCNQ and TCNE reagents, respectively, refer to the high accuracy and precision of the proposed method. These results are also confirmed by the between-day precision and the percent recovery of 99.90-100.1 and 99.60-100.4 for Fluclox and 99.90-100.5 and 99.40-100.1 for Diclox using TNCQ and TCNE reagents, respectively. The results obtained for the two reagents are comparable with those obtained by the official method.

Physically absorbable reagents-collectors in elementary flotation

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

S.A. Kondrat'ev; I.G. Bochkarev

2007-09-15

Based on the reviewed researches held at the Institute of Mining, Siberian Branch, Russian Academy of Sciences, the effect of physically absorbable reagents-collectors on formation of a flotation complex and its stability in turbulent pulp flows in flotation machines of basic types is considered. The basic requirements for physically absorbable reagents-collectors at different flotation stages are established.

Application of L-proline derivatives as chiral shift reagents for enantiomeric recognition of carboxylic acids.

PubMed

Naziroglu, Hayriye Nevin; Durmaz, Mustafa; Bozkurt, Selahattin; Sirit, Abdulkadir

2011-07-01

Four proline-derived chiral receptors 5-8 were readily synthesized starting from L-proline. The enantiomeric recognition ability of chiral receptors was examined with a series of carboxylic acids by (1) H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that the hosts form 1:1 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. Among the chiral receptors used in this study, prolinamide 6 was found to be the best chiral shift reagent and is effective for the determination of the enantiomeric excess of chiral carboxylic acids. Copyright © 2011 Wiley-Liss, Inc.

Supercharging Protein Complexes from Aqueous Solution Disrupts their Native Conformations

NASA Astrophysics Data System (ADS)

Sterling, Harry J.; Kintzer, Alexander F.; Feld, Geoffrey K.; Cassou, Catherine A.; Krantz, Bryan A.; Williams, Evan R.

2012-02-01

The effects of aqueous solution supercharging on the solution- and gas-phase structures of two protein complexes were investigated using traveling-wave ion mobility-mass spectrometry (TWIMS-MS). Low initial concentrations of m-nitrobenzyl alcohol ( m-NBA) in the electrospray ionization (ESI) solution can effectively increase the charge of concanavalin A dimers and tetramers, but at higher m-NBA concentrations, the increases in charge are accompanied by solution-phase dissociation of the dimers and up to a ~22% increase in the collision cross section (CCS) of the tetramers. With just 0.8% m-NBA added to the ESI solution of a ~630 kDa anthrax toxin octamer complex, the average charge is increased by only ~4% compared with the "native" complex, but it is sufficiently destabilized so that extensive gas-phase fragmentation occurs in the relatively high pressure regions of the TWIMS device. Anthrax toxin complexes exist in either a prechannel or a transmembrane channel state. With m-NBA, the prechannel state of the complex has the same CCS/charge ratio in the gas phase as the transmembrane channel state of the same complex formed without m-NBA, yet undergoes extensive dissociation, indicating that destabilization from supercharging occurs in the ESI droplet prior to ion formation and is not a result of Coulombic destabilization in the gas phase as a result of higher charging. These results demonstrate that the supercharging of large protein complexes is the result of conformational changes induced by the reagents in the ESI droplets, where enrichment of the supercharging reagent during droplet evaporation occurs.

Tandem nucleophilic addition-Oppenauer oxidation of aromatic aldehydes to aryl ketones with triorganoaluminium reagents.

PubMed

Fu, Ying; Yang, Yanshou; Hügel, Helmut M; Du, Zhengyin; Wang, Kehu; Huang, Danfeng; Hu, Yulai

2013-07-21

In the presence of pinacolone, the in situ prepared triorganoaluminium reagents reacted with aromatic aldehydes to give ketones in moderate to high yield. We propose that the products are formed via a tandem organoaluminium reagents addition-Oppenauer oxidation sequence.

Chemical Amplification with Encapsulated Reagents

NASA Technical Reports Server (NTRS)

Chen, Jian; Koemer, Steffi; Craig, Stephen; Lin, Shirley; Rudkevich, Dmitry M.; Rebek, Julius, Jr.

2002-01-01

Autocatalysis and chemical amplification are characteristic properties of living systems, and they give rise to behaviors such as increased sensitivity, responsiveness, and self-replication. Here we report a synthetic system in which a unique form of compartmentalization leads to nonlinear, autocatalytic behavior. The compartment is a reversibly formed capsule in which a reagent is sequestered. Reaction products displace the reagent from the capsule into solution and the reaction rate is accelerated. The resulting self-regulation is sensitive to the highly selective molecular recognition properties of the capsule.

Chemiluminescence reactions with cationic, neutral, and anionic ruthenium(II) complexes containing 2,2'-bipyridine and bathophenanthroline disulfonate ligands.

PubMed

Francis, Paul S; Papettas, Dimitra; Zammit, Elizabeth M; Barnett, Neil W

2010-07-15

Ruthenium complexes containing 4,7-diphenyl-1,10-phenanthroline disulfonate (bathophenanthroline disulfonate; BPS) ligands, Ru(BPS)(3)(4-), Ru(BPS)(2)(bipy)(2-) and Ru(BPS)(bipy)(2), were compared to tris(2,2'-bipyridine)ruthenium(II) (Ru(bipy)(3)(2+)), including examination of the wavelengths of maximum absorption and corrected emission intensity, photoluminescence quantum yield, stability of their oxidised ruthenium(III) form, and relative chemiluminescence intensities and signal-to-blank ratios with cerium(IV) sulfate and six analytes (codeine, morphine cocaine, potassium oxalate, furosemide and hydrochlorothiazide) in acidic aqueous solution. The presence of BPS ligands in the complex increased the photoluminescence quantum yield, but decreased the stability of the oxidised form of the reagent. In contrast to previous evidence showing much greater electrochemiluminescence intensities using Ru(BPS)(2)(bipy)(2-) and Ru(BPS)(bipy)(2), these complexes did not provide superior chemiluminescence signals than their homoleptic analogues. Copyright 2010 Elsevier B.V. All rights reserved.

Strategies for generating peptide radical cations via ion/ion reactions.

PubMed

Gilbert, Joshua D; Fisher, Christine M; Bu, Jiexun; Prentice, Boone M; Redwine, James G; McLuckey, Scott A

2015-02-01

Several approaches for the generation of peptide radical cations using ion/ion reactions coupled with either collision induced dissociation (CID) or ultraviolet photo dissociation (UVPD) are described here. Ion/ion reactions are used to generate electrostatic or covalent complexes comprised of a peptide and a radical reagent. The radical site of the reagent can be generated multiple ways. Reagents containing a carbon-iodine (C-I) bond are subjected to UVPD with 266-nm photons, which selectively cleaves the C-I bond homolytically. Alternatively, reagents containing azo functionalities are collisionally activated to yield radical sites on either side of the azo group. Both of these methods generate an initial radical site on the reagent, which then abstracts a hydrogen from the peptide while the peptide and reagent are held together by either electrostatic interactions or a covalent linkage. These methods are demonstrated via ion/ion reactions between the model peptide RARARAA (doubly protonated) and various distonic anionic radical reagents. The radical site abstracts a hydrogen atom from the peptide, while the charge site abstracts a proton. The net result is the conversion of a doubly protonated peptide to a peptide radical cation. The peptide radical cations have been fragmented via CID and the resulting product ion mass spectra are compared to the control CID spectrum of the singly protonated, even-electron species. This work is then extended to bradykinin, a more broadly studied peptide, for comparison with other radical peptide generation methods. The work presented here provides novel methods for generating peptide radical cations in the gas phase through ion/ion reaction complexes that do not require modification of the peptide in solution or generation of non-covalent complexes in the electrospray process. Copyright © 2015 John Wiley & Sons, Ltd.

Methods and apparatuses for reagent delivery, reactive barrier formation, and pest control

DOEpatents

Gilmore, Tyler [Pasco, WA; Kaplan, Daniel I [Aiken, SC; Last, George [Richland, WA

2002-07-09

A reagent delivery method includes positioning reagent delivery tubes in contact with soil. The tubes can include a wall that is permeable to a soil-modifying reagent. The method further includes supplying the reagent in the tubes, diffusing the reagent through the permeable wall and into the soil, and chemically modifying a selected component of the soil using the reagent. The tubes can be in subsurface contact with soil, including groundwater, and can be placed with directional drilling equipment independent of groundwater well casings. The soil-modifying reagent includes a variety of gases, liquids, colloids, and adsorbents that may be reactive or non-reactive with soil components. The method may be used inter alia to form reactive barriers, control pests, and enhance soil nutrients for microbes and plants.

Peptide bond-forming reagents HOAt and HATU are not mutagenic in the bacterial reverse mutation test.

PubMed

Nicolette, John; Neft, Robin E; Vanosdol, Jessica; Murray, Joel

2016-04-01

The peptide bond-forming reagents 1-hydroxy-7-azabenzotriazole (HOAt, CAS 39968-33-7) and O-(7-Azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU, CAS 148893-10-1) either have structural alerts, unclassified features or are considered out of domain when evaluated for potential mutagenicity with in silico programs DEREK and CaseUltra. Since they are commonly used reagents in pharmaceutical drug syntheses, they may become drug substance or drug product impurities and would need to be either controlled to appropriately safe levels or tested for mutagenicity. Both reagents were tested in the bacterial reverse mutation (Ames) test at Covance, under GLP conditions, following the OECD test guideline and ICH S2(R1) recommendations and found to be negative. Our data show that HOAt and HATU-common pharmaceutical synthesis reagents-are not mutagenic, and can be treated as ordinary drug impurities. © 2016 Wiley Periodicals, Inc.

Determination of antioxidants by a novel on-line HPLC-cupric reducing antioxidant capacity (CUPRAC) assay with post-column detection.

PubMed

Celik, Saliha Esin; Ozyürek, Mustafa; Güçlü, Kubilay; Apak, Reşat

2010-07-26

A novel on-line HPLC-cupric reducing antioxidant capacity (CUPRAC) method was developed for the selective determination of polyphenols (flavonoids, simple phenolic and hydroxycinnamic acids) in complex plant matrices. The method combines chromatographic separation, constituent analysis, and post-column identification of antioxidants in plant extracts. The separation of polyphenols was performed on a C18 column using gradient elution with two different mobile phase solutions, i.e., MeOH and 0.2% o-phosphoric acid. The HPLC-separated antioxidant polyphenols in the extracts react with copper(II)-neocuproine (Cu(II)-Nc) reagent in a post-column reaction coil to form a derivative. The reagent is reduced by antioxidants to the copper(I)-neocuproine (Cu(I)-Nc) chelate having maximum absorption at 450 nm. The negative peaks of antioxidant constituents were monitored by measuring the increase in absorbance due to Cu(I)-Nc. The detection limits of polyphenols at 450 nm (in the range of 0.17-3.46 microM) after post-column derivatization were comparable to those at 280 nm UV detection without derivatization. The developed method was successfully applied to the identification of antioxidant compounds in crude extracts of Camellia sinensis, Origanum marjorana and Mentha. The method is rapid, inexpensive, versatile, non-laborious, uses stable reagents, and enables the on-line qualitative and quantitative estimation of antioxidant constituents of complex plant samples. Copyright 2010 Elsevier B.V. All rights reserved.

Features of the reaction of heterocyclic analogs of chalcone with lanthanide shift reagents

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

Turov, A.V.; Khilya, V.P.

1994-10-01

The PMR spectra of heterocyclic analogs of 2-hydroxychalcone containing thiazole, benzofuran, triazole, imidazole, benzodioxane, or pyridine rings in the presence of lanthanide shift reagents are studied. It is found that the most effective reagent for modifying the spectra of these compounds is Yb(fod)3. The broadening of the spectra of 2-hydroxy chalcones in the presence of lanthanide shift reagents is explained by the dynamic effects of complex formation. An example is given of the determination of the conformation of molecules of 2-hydroxychalcone by the simultaneous use of lanthanide shift reagents and the homonuclear Overhauser effect. 9 refs., 1 fig., 1 tab.

Chemical deposition methods using supercritical fluid solutions

DOEpatents

Sievers, Robert E.; Hansen, Brian N.

1990-01-01

A method for depositing a film of a desired material on a substrate comprises dissolving at least one reagent in a supercritical fluid comprising at least one solvent. Either the reagent is capable of reacting with or is a precursor of a compound capable of reacting with the solvent to form the desired product, or at least one additional reagent is included in the supercritical solution and is capable of reacting with or is a precursor of a compound capable of reacting with the first reagent or with a compound derived from the first reagent to form the desired material. The supercritical solution is expanded to produce a vapor or aerosol and a chemical reaction is induced in the vapor or aerosol so that a film of the desired material resulting from the chemical reaction is deposited on the substrate surface. In an alternate embodiment, the supercritical solution containing at least one reagent is expanded to produce a vapor or aerosol which is then mixed with a gas containing at least one additional reagent. A chemical reaction is induced in the resulting mixture so that a film of the desired material is deposited.

Single-Chain Fv-Based Anti-HIV Proteins: Potential and Limitations

PubMed Central

West, Anthony P.; Galimidi, Rachel P.; Gnanapragasam, Priyanthi N. P.

2012-01-01

The existence of very potent, broadly neutralizing antibodies against human immunodeficiency virus type 1 (HIV-1) offers the potential for prophylaxis against HIV-1 infection by passive immunization or gene therapy. Both routes permit the delivery of modified forms of IgGs. Smaller reagents are favored when considering ease of tissue penetration and the limited capacities of gene therapy vectors. Immunoadhesin (single-chain fragment variable [scFv]-Fc) forms of IgGs are one class of relatively small reagent that has been explored for delivery by adeno-associated virus. Here we investigated the neutralization potencies of immunoadhesins compared to those of their parent IgGs. For the antibodies VRC01, PG9, and PG16, the immunoadhesins showed modestly reduced potencies, likely reflecting reduced affinities compared to those of the parent IgG, and the VRC01 immunoadhesin formed dimers and multimers with reduced neutralization potencies. Although scFv forms of neutralizing antibodies may exhibit affinity reductions, they provide a means of building reagents with multiple activities. Attachment of the VRC01 scFv to PG16 IgG yielded a bispecific reagent whose neutralization activity combined activities from both parent antibodies. Although the neutralization activity due to each component was partially reduced, the combined reagent is attractive since fewer strains escaped neutralization. PMID:22013046

Complexation of rhodium(II) tetracarboxylates with aliphatic diamines in solution: 1H and 13C NMR and DFT investigations.

PubMed

Jaźwiński, Jarosław; Sadlej, Agnieszka

2013-10-01

The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane-1,diamine, propane-1,3-diamine and nonane-1,9-diamine) and their N,N'-dimethyl and N,N,N',N'-tetramethyl derivatives in chloroform solution has been investigated by (1) H and (13) C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH3 ) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane-1,9-diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane-1,2-diamine and their NMR parameters were explored by means of DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd.

A simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

NASA Technical Reports Server (NTRS)

Dupraw, W. A.

1972-01-01

A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.

Synthesis of Quaternary Carbon Stereogenic Centers through Enantioselective Cu-Catalyzed Allylic Substitutions with Vinylaluminum Reagents

PubMed Central

Gao, Fang; McGrath, Kevin P.; Lee, Yunmi; Hoveyda, Amir H.

2010-01-01

Catalytic enantioselective allylic substitution (EAS) reactions, which involve the use of alkyl- or aryl-substituted vinylaluminum reagents and afford 1,4-dienes containing a quaternary carbon stereogenic center at their C-3 site, are disclosed. The C–C bond forming transformations are promoted by 0.5–2.5 mol % of sulfonate bearing chiral bidentate N-heterocyclic carbene (NHC) complexes, furnishing the desired products efficiently (66–97% yield of isolated products) and in high site- (>98% SN2′) and enantioselectivity [up to 99:1 enantiomer ratio (er)]. To the best of our knowledge, the present report puts forward the first cases of allylic substitution reactions that result in the generation of all-carbon quaternary stereogenic centers through the addition of a vinyl unit. The aryl- and vinyl-substituted vinylaluminum reagents, which cannot be prepared in high efficiency through direct reaction with diisobutylaluminum hydride, are accessed through a recently introduced Ni-catalyzed reaction of the corresponding terminal alkynes with the same inexpensive metal-hydride agent. Sequential Ni-catalyzed hydrometallations and Cu-catalyzed C–C bond forming reactions allow for efficient and selective synthesis of a range of enantiomerically enriched EAS products, which cannot cannot be accessed by previously disclosed strategies (due to inefficient vinylmetal synthesis or low reactivity and/or selectivity with Si-substituted derivatives). The utility of the protocols developed is demonstrated through a concise enantioselective synthesis of natural product bakuchiol. PMID:20860365

A simple spectrophotometric method for the determination of arsenic in industrial and environmental samples using 2,4-Dihydroxy benzophenone-2-amino thiophenol.

PubMed

Deepa, K; Lingappa, Y

2014-04-24

2,4-Dihydroxy benzophenone-2-amino thiophenol (BPBT) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of arsenic. The reagent reacts with arsenic in acidic medium (pH=6.0, sodium acetate-acetic acid buffer) to form light greenish yellow colored 1:1 (M:L) complex. Maximum absorbance was obtained at 343 nm and remains constant for over 24 h. The molar absorptivity and Sandell's sensitivity of BPBT are found to be 6.01×10(4) L mol(-1)cm(-1) and 0.0016 μg cm(-2) respectively. The system obeys Beer's law in the range of 0.125-2.637 μg/ml of As (III). Since BPBT method is more sensitive, it was applied for the determination of arsenic in some environmental water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Spectrofluorometric determination of furosemide in some pharmaceutical product using acriflavine as a reagent

NASA Astrophysics Data System (ADS)

Qader, Aryan F.; Fakhre, Nabil A.

2017-09-01

Simple, inexpensive, rapid and sensitive determination of furosemide spectrofluorometrically was suggested using acriflavine as a new reagent. The method based on the quantitative quenching effect of furosemide on the native fluorescence of acriflavine in presence of Britton-Robinson buffer medium due to the reaction of furosemide with acriflavine to form an ion associated complex. The decrease of acriflavine fluorescence was observed at 505 nm after excitation at 265 nm. the florescence - concentration plot is rectilinear over the range of 2.0-10 µg/ml with correlation coefficient 0.9991 and detection limit 0.2 µg/ml. No interference was observed from the excipients that are commonly present in pharmaceutical formulations. The proposed method was determination of furosemide in some commercial tablets. The results were compared with that of HPLC method revealed with good agreements and no significant differences in the accuracy and precision.

Presidential Green Chemistry Challenge: 2007 Academic Award

EPA Pesticide Factsheets

Presidential Green Chemistry Challenge 2007 award winner, Professor Michael J. Krische, developed selective C-C bond-forming hydrogenation without organometallic reagents, eliminating hazardous reagents and hazardous waste.

Utility of eosin Y as a complexing reagent for the determination of citalopram hydrobromide in commercial dosage forms by fluorescence spectrophotometry.

PubMed

Azmi, Syed Najmul Hejaz; Al-Fazari, Ahlam; Al-Badaei, Munira; Al-Mahrazi, Ruqiya

2015-12-01

An accurate, selective and sensitive spectrofluorimetric method was developed for the determination of citalopram hydrobromide in commercial dosage forms. The method was based on the formation of a fluorescent ion-pair complex between citalopram hydrobromide and eosin Y in the presence of a disodium hydrogen phosphate/citric acid buffer solution of pH 3.4 that was extractable in dichloromethane. The extracted complex showed fluorescence intensity at λem = 554 nm after excitation at 259 nm. The calibration curve was linear over at concentrations of 2.0-26.0 µg/mL. Under optimized experimental conditions, the proposed method was validated as per ICH guidelines. The effect of common excipients used as additives was tested and the tolerance limit calculated. The limit of detection for the proposed method was 0.121 μg/mL. The proposed method was successfully applied to the determination of citalopram hydrobromide in commercial dosage forms. The results were compared with the reference RP-HPLC method. Copyright © 2015 John Wiley & Sons, Ltd.

Binuclear transition-metal complexes as new reagents for selective cross-linking of proteins. Coordination of cytochrome c to dirhodium(II). mu. -tetraacetate

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

Chen, J.; Kostic, N.M.

1988-07-27

This study introduces binuclear transition-metal complexes as reagents for selective covalent cross-linking of proteins. Incubation of horse cytochrome c (designated cyt) with Rh{sub 2}(OAc){sub 4} under mild conditions yields the diprotein complex, Rh{sub 2}(OAc){sub 4}(cyt){sub 2}, whose composition is established by size-exclusion chromatography, uv-vis spectroscopy, and {sup 1}H NMR spectroscopy. The protein molecules are coordinated to the Rh atoms via the imidazole (Im) rings of their His 33 residues, as shown by uv difference and {sup 1}H NMR spectroscopy, by the pH effect on the complex formation, and by the control experiments with tuna cytochrome c. The diprotein complex ismore » stable under ordinary conditions, and yet it can be cleaved, and the native protein recovered, by treatment with a suitable strong nucleophile. Spectroscopic and electrochemical measurements show that the structural and redox properties of cytochrome c are not perturbed significantly by cross-linking. Comparison between Rh{sub 2}(OAc){sub 4}(Im){sub 2} and Rh{sub 2}(OAc){sub 4}(cyt){sub 2} shows that the complex containing small ligands is not an entirely realistic model of the complex containing proteins. In particular, the enhanced stability of the latter toward hydrolysis may be due to steric bulk of the protein ligands and to hydrogen bonds that amino acid side chains may form with the inorganic link. Some of the findings of this study may pertain to the mechanism of antitumor action of the Rh{sub 2}(RCOO){sub 4} complexes. 86 refs., 2 tabs.« less

Some Addition and Complexation Reactions of a Silylated Amino(Methylene)Phosphine.

DTIC Science & Technology

1984-12-12

0 ., . % , ’ - - o= . *.- . ° , % , - . -° , .° ..% . . . -= •% .°• - " . = . 4 reagents to the P=C bond 3 , and possible cycloaddition reactions...example, the reaction of 1 with alkyllithium reagents occurs with both nucleophilic substitution and addition leading to trialkylphosphines or P-C-P...such °" as 1 as synthetic reagents in organophosphorus and organometallic chemistry. A secondary objective of this study was to more closely compare

Collision-induced dissociative chemical cross-linking reagents and methodology: Applications to protein structural characterization using tandem mass spectrometry analysis.

PubMed

Soderblom, Erik J; Goshe, Michael B

2006-12-01

Chemical cross-linking combined with mass spectrometry is a viable approach to study the low-resolution structure of protein and protein complexes. However, unambiguous identification of the residues involved in a cross-link remains analytically challenging. To enable a more effective analysis across various MS platforms, we have developed a novel set of collision-induced dissociative cross-linking reagents and methodology for chemical cross-linking experiments using tandem mass spectrometry (CID-CXL-MS/MS). These reagents incorporate a single gas-phase cleavable bond within their linker region that can be selectively fragmented within the in-source region of the mass spectrometer, enabling independent MS/MS analysis for each peptide. Initial design concepts were characterized using a synthesized cross-linked peptide complex. Following verification and subsequent optimization of cross-linked peptide complex dissociation, our reagents were applied to homodimeric glutathione S-transferase and monomeric bovine serum albumin. Cross-linked residues identified by our CID-CXL-MS/MS method were in agreement with published crystal structures and previous cross-linking studies using conventional approaches. Common LC/MS/MS acquisition approaches such as data-dependent acquisition experiments using ion trap mass spectrometers and product ion spectral analysis using SEQUEST were shown to be compatible with our CID-CXL-MS/MS reagents, obviating the requirement for high resolution and high mass accuracy measurements to identify both intra- and interpeptide cross-links.

Electron and Oxygen Atom Transfer Chemistry of Co(II) in a Proton Responsive, Redox Active Ligand Environment.

PubMed

Cook, Brian J; Pink, Maren; Pal, Kuntal; Caulton, Kenneth G

2018-05-21

The bis-pyrazolato pyridine complex LCo(PEt 3 ) 2 serves as a masked form of three-coordinate Co II and shows diverse reactivity in its reaction with several potential outer sphere oxidants and oxygen atom transfer reagents. N-Methylmorpholine N-oxide (NMO) oxidizes coordinated PEt 3 from LCo(PEt 3 ) 2 , but the final cobalt product is still divalent cobalt, in LCo(NMO) 2 . The thermodynamics of a variety of oxygen atom transfer reagents, including NMO, are calculated by density functional theory, to rank their oxidizing power. Oxidation of LCo(PEt 3 ) 2 with AgOTf in the presence of LiCl as a trapping nucleophile forms the unusual aggregate [LCo(PEt 3 ) 2 Cl(LiOTf) 2 ] 2 held together by Li + binding to very nucleophilic chloride on Co(III) and triflate binding to those Li + . In contrast, Cp 2 Fe + effects oxidation to trivalent cobalt, to form (HL)Co(PEt 3 ) 2 Cl + ; proton and the chloride originate from solvent in a rare example of CH 2 Cl 2 dehydrochlorination. An unexpected noncomplementary redox reaction is reported involving attack by 2e reductant PEt 3 nucleophile on carbon of the 1e oxidant radical Cp 2 Fe + , forming a P-C bond and H + ; this reaction competes in the reaction of LCo(PEt 3 ) 2 with Cp 2 Fe + .

Lithium Enolates in the Enantioselective Construction of Tetrasubstituted Carbon Centers with Chiral Lithium Amides as Noncovalent Stereodirecting Auxiliaries.

PubMed

Yu, Kai; Lu, Ping; Jackson, Jeffrey J; Nguyen, Thuy-Ai D; Alvarado, Joseph; Stivala, Craig E; Ma, Yun; Mack, Kyle A; Hayton, Trevor W; Collum, David B; Zakarian, Armen

2017-01-11

Lithium enolates derived from carboxylic acids are ubiquitous intermediates in organic synthesis. Asymmetric transformations with these intermediates, a central goal of organic synthesis, are typically carried out with covalently attached chiral auxiliaries. An alternative approach is to utilize chiral reagents that form discrete, well-defined aggregates with lithium enolates, providing a chiral environment conducive of asymmetric bond formation. These reagents effectively act as noncovalent, or traceless, chiral auxiliaries. Lithium amides are an obvious choice for such reagents as they are known to form mixed aggregates with lithium enolates. We demonstrate here that mixed aggregates can effect highly enantioselective transformations of lithium enolates in several classes of reactions, most notably in transformations forming tetrasubstituted and quaternary carbon centers. Easy recovery of the chiral reagent by aqueous extraction is another practical advantage of this one-step protocol. Crystallographic, spectroscopic, and computational studies of the central reactive aggregate, which provide insight into the origins of selectivity, are also reported.

Coupling complement regulators to immunoglobulin domains generates effective anti-complement reagents with extended half-life in vivo

PubMed Central

HARRIS, C L; WILLIAMS, A S; LINTON, S M; MORGAN, B P

2002-01-01

Complement activation and subsequent generation of inflammatory molecules and membrane attack complex contributes to the pathology of a number of inflammatory and degenerative diseases, including arthritis, glomerulonephritis and demyelination. Agents that specifically inhibit complement activation might prove beneficial in the treatment of these diseases. Soluble recombinant forms of the naturally occurring membrane complement regulatory proteins (CRP) have been exploited for this purpose. We have undertaken to design better therapeutics based on CRP. Here we describe the generation of soluble, recombinant CRP comprising rat decay accelerating factor (DAF) or rat CD59 expressed as Fc fusion proteins, antibody-like molecules comprising two CRP moieties in place of the antibody Fab arms (CRP-Ig). Reagents bearing DAF on each arm (DAF-Ig), CD59 on each arm (CD59-Ig) and a hybrid reagent containing both DAF and CD59 were generated. All three reagents inhibited C activation in vitro. Compared with soluble CRP lacking Fc domains, activity was reduced, but was fully restored by enzymatic release of the regulator from the Ig moiety, implicating steric constraints in reducing functional activity. In vivo studies showed that DAF-Ig, when compared to soluble DAF, had a much extended half-life in the circulation in rats and concomitantly caused a sustained reduction in plasma complement activity. When given intra-articularly to rats in a model of arthritis, DAF-Ig significantly reduced severity of disease. The data demonstrate the potential of CRP-Ig as reagents for sustained therapy of inflammatory disorders, including arthritis, but emphasize the need for careful design of fusion proteins to retain function. PMID:12165074

Sequential one-pot addition of excess aryl-Grignard reagents and electrophiles to O-alkyl thioformates.

PubMed

Murai, Toshiaki; Morikawa, Kenta; Maruyama, Toshifumi

2013-09-23

The sequential addition of aromatic Grignard reagents to O-alkyl thioformates proceeded to completion within 30 s to give aryl benzylic sulfanes in good yields. This reaction may begin with the nucleophilic attack of the Grignard reagent onto the carbon atom of the O-alkyl thioformates, followed by the elimination of ROMgBr to generate aromatic thioaldehydes, which then react with a second molecule of the Grignard reagent at the sulfur atom to form arylsulfanyl benzylic Grignard reagents. To confirm the generation of aromatic thioaldehydes, the reaction between O-alkyl thioformates and phenyl Grignard reagent was carried out in the presence of cyclopentadiene. As a result, hetero-Diels-Alder adducts of the thioaldehyde and the diene were formed. The treatment of a mixture of the thioformate and phenyl Grignard reagent with iodine gave 1,2-bis(phenylsulfanyl)-1,2-diphenyl ethane as a product, which indicated the formation of arylsulfanyl benzylic Grignard reagents in the reaction mixture. When electrophiles were added to the Grignard reagents that were generated in situ, four-component coupling products, that is, O-alkyl thioformates, two molecules of Grignard reagents, and electrophiles, were obtained in moderate-to-good yields. The use of silyl chloride or allylic bromides gave the adducts within 5 min, whereas the reaction with benzylic halides required more than 30 min. The addition to carbonyl compounds was complete within 1 min and the use of lithium bromide as an additive enhanced the yields of the four-component coupling products. Finally, oxiranes and imines also participated in the coupling reaction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation of V(V)-4-(2-pyridylazo)resorcinolato complex from a large excess reagent using an ODS cartridge for high-performance liquid chromatography.

PubMed

Takahashi, Toru; Kaneko, Emiko; Yotsuyanagi, Takao

2006-12-01

A selective off-line preconcentration technique for the V(V) complex with 4-(2-pyridylazo)resorcinol has been developed and successfully applied to the determination of V(V) in an air-borne sample. The target complex was separated from excess reagent using an ODS cartridge and water as the eluent. The complex was then concentrated on another ODS cartridge using tetrabutylammonium bromide and eluted with methanol; the eluate was applied to a one-drop concentration/HPLC. A detection limit as low as (6.05 +/- 0.82)x 10(-11) M (5 ppt) was achieved.

Preparation and Degradation of Polysilylenes

DTIC Science & Technology

1991-05-02

Grignard reagent formation from Mg and alkyl iodides in comparison with less reactive alkyl chlorides 2 3 . Electron transfer to the chlorides occur at...stoichiometric balance of reagents and nearly complete conversions (e.g. DPN-100 at 99% conversion in a homogeneous polycondensation with exact stoichiometric...the magnesium surface, whereas alkyl iodides accept electrons through Ŝ. larger distance and could not efficiently form organomagneslum reagents but

Enantioselective synthesis of L-(-)-4- boronophenylalanine (L-BPA)

DOEpatents

Samsel, Edward G.

1992-01-01

A method of making substantially pure L-BPA is disclosed. The method includes the steps of reacting 4-bromobenzaldehyde with ethylene glycol to form 4-bromobenzaldehyde ethylene glycol acetal, sequentially reacting 4-bromobenzaldehyde ethyleneglycol acetal with Mg to produce the Grignard reagent and thereafter reacting with tributyl borate and then converting to an acid environment to form 4-boronobenzaldehyde, reacting 4-boronobenzaldehyde with diethanol amine to form 4-boronobenzaldehyde diethanolamine ester, condensing the 4-boronobenzaldehyde diethanolamine ester with 2-phenyl-2-oxazolin-5-one to form an azlactone, reacting the azlactone with an alkali metal hydroxide to form z-.alpha.-benzoylamino-4-boronocinnamic acid, asymmetrically hydrogenating the z-.alpha.-benzoylamino-4-boronocinnamic acid in the presence of a catalyst of a cheltate complex of rhodium (I) with chiral bisphosphines to form L-(+)-N-benzoyl-4-boronophenylalanine, and thereafter acidifying the L-(+)-N-benzoyl-4-boronophenylalanine in an organic medium to produce L-BPA.

Enantioselective synthesis of L-(-)-4- boronophenylalanine (L-BPA)

DOEpatents

Samsel, E.G.

1992-10-20

A method of making substantially pure L-BPA is disclosed. The method includes the steps of reacting 4-bromobenzaldehyde with ethylene glycol to form 4-bromobenzaldehyde ethylene glycol acetal, sequentially reacting 4-bromobenzaldehyde ethyleneglycol acetal with Mg to produce the Grignard reagent and thereafter reacting with tributyl borate and then converting to an acid environment to form 4-boronobenzaldehyde, reacting 4-boronobenzaldehyde with diethanol amine to form 4-boronobenzaldehyde diethanolamine ester, condensing the 4-boronobenzaldehyde diethanolamine ester with 2-phenyl-2-oxazolin-5-one to form an azlactone, reacting the azlactone with an alkali metal hydroxide to form z-[alpha]-benzoylamino-4boronocinnamic acid, asymmetrically hydrogenating the z-[alpha]-benzoylamino-4-boronocinnamic acid in the presence of a catalyst of a cheltate complex of rhodium (I) with chiral bisphosphines to form L-(+)-N-benzoyl-4-boronophenylalanine, and thereafter acidifying the L-(+)-N-benzoyl-4-boronophenylalanine in an organic medium to produce L-BPA. 3 figs.

Situ formation of apatite for sequestering radionuclides and heavy metals

DOEpatents

Moore, Robert C.

2003-07-15

Methods for in situ formation in soil of a permeable reactive barrier or zone comprising a phosphate precipitate, such as apatite or hydroxyapatite, which is capable of selectively trapping and removing radionuclides and heavy metal contaminants from the soil, while allowing water or other compounds to pass through. A preparation of a phosphate reagent and a chelated calcium reagent is mixed aboveground and injected into the soil. Subsequently, the chelated calcium reagent biodegrades and slowly releases free calcium. The free calcium reacts with the phosphate reagent to form a phosphate precipitate. Under the proper chemical conditions, apatite or hydroxyapatite can form. Radionuclide and heavy metal contaminants, including lead, strontium, lanthanides, and uranium are then selectively sequestered by sorbing them onto the phosphate precipitate. A reducing agent can be added for reduction and selective sequestration of technetium or selenium contaminants.

Biologically-Inspired Peptide Reagents for Enhancing IMS-MS Analysis of Carbohydrates

NASA Astrophysics Data System (ADS)

Bohrer, Brian C.; Clemmer, David E.

2011-09-01

The binding properties of a peptidoglycan recognition protein are translated via combinatorial chemistry into short peptides. Non-adjacent histidine, tyrosine, and arginine residues in the protein's binding cleft that associate specifically with the glycan moiety of a peptidoglycan substrate are incorporated into linear sequences creating a library of 27 candidate tripeptide reagents (three possible residues permutated across three positions). Upon electrospraying the peptide library and carbohydrate mixtures, some noncovalent complexes are observed. The binding efficiencies of the peptides vary according to their amino acid composition as well as the disaccharide linkage and carbohydrate ring-type. In addition to providing a charge-carrier for the carbohydrate, peptide reagents can also be used to differentiate carbohydrate isomers by ion mobility spectrometry. The utility of these peptide reagents as a means of enhancing ion mobility analysis of carbohydrates is illustrated by examining four glucose-containing disaccharide isomers, including a pair that is not resolved by ion mobility alone. The specificity and stoichiometry of the peptide-carbohydrate complexes are also investigated. Trihistidine demonstrates both suitable binding efficiency and successful resolution of disaccharides isomers, suggesting it may be a useful reagent in IMS analyses of carbohydrates.

Complexity and performance of on-chip biochemical assays

NASA Astrophysics Data System (ADS)

Kopf-Sill, Anne R.; Nikiforov, Theo; Bousse, Luc J.; Nagle, Rob; Parce, J. W.

1997-03-01

The use of microchips for performing biochemical processes has the potential to reduce reagent use and thus assay costs, increase throughput, and automate complex processes. We are building a multifunctional platform that provides sensing and actuation functions for a variety of microchip- based biochemical and analytical processes. Here we describe recent experiments that include on-chip dilution, reagent mixing, reaction, separation, and detection for important classes of biochemical assays. Issues in chip design and control are discussed.

Luminescent Rhenium(I) and Iridium(III) Polypyridine Complexes as Biological Probes, Imaging Reagents, and Photocytotoxic Agents.

PubMed

Lo, Kenneth Kam-Wing

2015-12-15

Although the interactions of transition metal complexes with biological molecules have been extensively studied, the use of luminescent transition metal complexes as intracellular sensors and bioimaging reagents has not been a focus of research until recently. The main advantages of luminescent transition metal complexes are their high photostability, long-lived phosphorescence that allows time-resolved detection, and large Stokes shifts that can minimize the possible self-quenching effect. Also, by the use of transition metal complexes, the degree of cellular uptake can be readily determined using inductively coupled plasma mass spectrometry. For more than a decade, we have been interested in the development of luminescent transition metal complexes as covalent labels and noncovalent probes for biological molecules. We argue that many transition metal polypyridine complexes display triplet charge transfer ((3)CT) emission that is highly sensitive to the local environment of the complexes. Hence, the biological labeling and binding interactions can be readily reflected by changes in the photophysical properties of the complexes. In this laboratory, we have modified luminescent tricarbonylrhenium(I) and bis-cyclometalated iridium(III) polypyridine complexes of general formula [Re(bpy-R(1))(CO)3(py-R(2))](+) and [Ir(ppy-R(3))2(bpy-R(4))](+), respectively, with reactive functional groups and used them to label the amine and sulfhydryl groups of biomolecules such as oligonucleotides, amino acids, peptides, and proteins. Additionally, using a range of biological substrates such as biotin, estradiol, and indole, we have designed luminescent rhenium(I) and iridium(III) polypyridine complexes as noncovalent probes for biological receptors. The interesting results generated from these studies have prompted us to investigate the possible applications of luminescent transition metal complexes in intracellular systems. Thus, in the past few years, we have developed an interest in the cytotoxic activity, cellular uptake, and bioimaging applications of these complexes. Additionally, we and other research groups have demonstrated that many transition metal complexes have facile cellular uptake and organelle-localization properties and that their cytotoxic activity can be readily controlled. For example, complexes that can target the nucleus, nucleolus, mitochondria, lysosomes, endoplasmic reticulum, and Golgi apparatus have been identified. We anticipate that this selective localization property can be utilized in the development of intracellular sensors and bioimaging reagents. Thus, we have functionalized luminescent rhenium(I) and iridium(III) polypyridine complexes with various pendants, including molecule-binding moieties, sugar molecules, bioorthogonal functional groups, and polymeric chains such as poly(ethylene glycol) and polyethylenimine, and examined their potentials as biological reagents. This Account describes our design of luminescent rhenium(I) and iridium(III) polypyridine complexes and explains how they can serve as a new generation of biological reagents for diagnostic and therapeutic applications.

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

PubMed Central

Focken, Thilo

2014-01-01

Summary A review of the synthesis of natural products and bioactive compounds adopting phosphonamide anion technology is presented highlighting the utility of phosphonamide reagents in stereocontrolled bond-forming reactions. Methodologies utilizing phosphonamide anions in asymmetric alkylations, Michael additions, olefinations, and cyclopropanations will be summarized, as well as an overview of the synthesis of the employed phosphonamide reagents. PMID:25246946

Stereospecific Nickel-Catalyzed Cross-Coupling Reactions of Alkyl Grignard Reagents and Identification of Selective Anti-Breast Cancer Agents**

PubMed Central

Osborne, Charlotte A.; Moore, Curtis E.; Morrissette, Naomi S.; Jarvo, Elizabeth R.

2014-01-01

β-Hydrogen-containing alkyl Grignard reagents were used in a stereospecific nickel-catalyzed cross-coupling reaction to form sp3–sp3 carbon–carbon bonds. Aryl Grignard reagents were also utilized to synthesize 1,1-diarylalkanes. Several compounds synthesized by this method exhibited selective inhibition of proliferation of MCF-7 breast cancer cells. PMID:24478275

Highly versatile enantioselective conjugate addition of Grignard reagents to alpha,beta-unsaturated thioesters.

PubMed

Ruiz, Beatriz Maciá; Geurts, Koen; Fernández-Ibáñez, M Angeles; ter Horst, Bjorn; Minnaard, Adriaan J; Feringa, Ben L

2007-11-22

Herein, we report efficient catalysts for the asymmetric copper-catalyzed conjugate addition of Grignard reagents to alpha,beta-unsaturated thioesters. MeMgBr adds to aromatic alpha,beta-unsaturated thioesters with excellent enantioselectivities and moderate to good yields using Josiphos/CuBr and Tol-BINAP/CuI complexes. The use of bulky Grignard reagents leads to unprecedented enantioselectivities in the 1,4-addition to a broad range of aromatic and aliphatic alpha,beta-unsaturated thioesters using Tol-BINAP/CuI. The highest enantioselectivities reported so far for the addition of Grignard reagents to crowded beta-substituted aliphatic substrates are achieved with Tol-BINAP/CuI.

Direct arylation/alkylation/magnesiation of benzyl alcohols in the presence of Grignard reagents via Ni-, Fe-, or Co-catalyzed sp3 C-O bond activation.

PubMed

Yu, Da-Gang; Wang, Xin; Zhu, Ru-Yi; Luo, Shuang; Zhang, Xiao-Bo; Wang, Bi-Qin; Wang, Lei; Shi, Zhang-Jie

2012-09-12

Direct application of benzyl alcohols (or their magnesium salts) as electrophiles in various reactions with Grignard reagents has been developed via transition metal-catalyzed sp(3) C-O bond activation. Ni complex was found to be an efficient catalyst for the first direct cross coupling of benzyl alcohols with aryl/alkyl Grignard reagents, while Fe, Co, or Ni catalysts could promote the unprecedented conversion of benzyl alcohols to benzyl Grignard reagents in the presence of (n)hexylMgCl. These methods offer straightforward pathways to transform benzyl alcohols into a variety of functionalities.

Non-protein thiol imaging and quantification in live cells with a novel benzofurazan sulfide triphenylphosphonium fluorogenic compound.

PubMed

Yang, Yang; Guan, Xiangming

2017-05-01

Thiols (-SH) play various roles in biological systems. They are divided into protein thiols (PSH) and non-protein thiols (NPSH). Due to the significant roles thiols play in various physiological/pathological functions, numerous analytical methods have been developed for thiol assays. Most of these methods are developed for glutathione, the major form of NPSH. Majority of these methods require tissue/cell homogenization before analysis. Due to a lack of effective thiol-specific fluorescent/fluorogenic reagents, methods for imaging and quantifying thiols in live cells are limited. Determination of an analyte in live cells can reveal information that cannot be revealed by analysis of cell homogenates. Previously, we reported a thiol-specific thiol-sulfide exchange reaction. Based on this reaction, a benzofurazan sulfide thiol-specific fluorogenic reagent was developed. The reagent was able to effectively image and quantify total thiols (PSH+NPSH) in live cells through fluorescence microscopy. The reagent was later named as GUALY's reagent. Here we would like to report an extension of the work by synthesizing a novel benzofurazan sulfide triphenylphosphonium derivative [(((7,7'-thiobis(benzo[c][1,2,5]oxadiazole-4,4'-sulfonyl))bis(methylazanediyl))bis(butane-4,1-diyl))bis(triphenylphosphonium) (TBOP)]. Like GUALY's reagent, TBOP is a thiol-specific fluorogenic agent that is non-fluorescent but forms fluorescent thiol adducts in a thiol-specific fashion. Different than GUALY's reagent, TBOP reacts only with NPSH but not with PSH. TBOP was effectively used to image and quantify NPSH in live cells using fluorescence microscopy. TBOP is a complementary reagent to GUALY's reagent in determining the roles of PSH, NPSH, and total thiols in thiol-related physiological/pathological functions in live cells through fluorescence microscopy. Graphical Abstract Live cell imaging and quantification of non-protein thiols by TBOP.

Digitally programmable microfluidic automaton for multiscale combinatorial mixing and sample processing†

PubMed Central

Jensen, Erik C.; Stockton, Amanda M.; Chiesl, Thomas N.; Kim, Jungkyu; Bera, Abhisek; Mathies, Richard A.

2013-01-01

A digitally programmable microfluidic Automaton consisting of a 2-dimensional array of pneumatically actuated microvalves is programmed to perform new multiscale mixing and sample processing operations. Large (µL-scale) volume processing operations are enabled by precise metering of multiple reagents within individual nL-scale valves followed by serial repetitive transfer to programmed locations in the array. A novel process exploiting new combining valve concepts is developed for continuous rapid and complete mixing of reagents in less than 800 ms. Mixing, transfer, storage, and rinsing operations are implemented combinatorially to achieve complex assay automation protocols. The practical utility of this technology is demonstrated by performing automated serial dilution for quantitative analysis as well as the first demonstration of on-chip fluorescent derivatization of biomarker targets (carboxylic acids) for microchip capillary electrophoresis on the Mars Organic Analyzer. A language is developed to describe how unit operations are combined to form a microfluidic program. Finally, this technology is used to develop a novel microfluidic 6-sample processor for combinatorial mixing of large sets (>26 unique combinations) of reagents. The digitally programmable microfluidic Automaton is a versatile programmable sample processor for a wide range of process volumes, for multiple samples, and for different types of analyses. PMID:23172232

Spectrophotometric studies of reactions between pseudo-ephedrine with different inorganic and organic reagents and its micro-determination in pure and in pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Zayed, M. A.; El-Rasheedy, El-Gazy A.

2012-03-01

Two simple, sensitive, cheep and reliable spectrophotometric methods are suggested for micro-determination of pseudoephedrine in its pure form and in pharmaceutical preparation (Sinofree Tablets). The first one depends on the drug reaction with inorganic sensitive reagent like molybdate anion in aqueous media via formation of ion-pair mechanism. The second one depends on the drug reaction with π-acceptor reagent like DDQ in non-aqueous media via formation of charge transfer complex. These reactions were studied under various conditions and the optimum parameters were selected. Under proper conditions the suggested procedures were successfully applied for micro-determination of pseudoephedrine in pure and in Sinofree Tablets without interference from excepients. The values of SD, RSD, recovery %, LOD, LOQ and Sandell sensitivity refer to the high accuracy and precession of the applied procedures. The results obtained were compared with the data obtained by an official method, referring to confidence and agreement with DDQ procedure results; but it referred to the more accuracy of the molybdate data. Therefore, the suggested procedures are now successfully being applied in routine analysis of this drug in its pharmaceutical formulation (Sinofree) in Saudi Arabian Pharmaceutical Company (SPIMACO) in Boridah El-Qaseem, Saudi Arabia instead of imported kits had been previously used.

PHOTOMETRIC DETERMINATION OF THORIUM IN ORES WITH ARSENAZO III (in Russian)

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

Savvin, S.B.; Bagreev, V.B.

1960-01-01

Th and certain other tetravalent elements such as U and Zr form internal complexes with the reagent arsenazo III (an organic sulfocompound containing As) which are stable in strong acids, sulfates, and phosphates. Th was determined photometrically in HCl solutions ranging from 0.01 to 10 N without finding it necessary to remove the sulfates, phosphates, or oxalates. The method was especially useful for working at concentrations from 0.05 to 1 of Th in the analysis of minerals such as alaskite granite, syenite, and nordmarkite. (TTT)

In situ formation of magnetite reactive barriers in soil for waste stabilization

DOEpatents

Moore, Robert C.

2003-01-01

Reactive barriers containing magnetite and methods for making magnetite reactive barriers in situ in soil for sequestering soil contaminants including actinides and heavy metals, organic materials, iodine and technetium are disclosed. According to one embodiment, a two-step reagent introduction into soil takes place. In the first step, free oxygen is removed from the soil by separately injecting into the soil aqueous solutions of iron (II) salt, for example FeCl.sub.2, and base, for example NaOH or NH.sub.3 in about a 1:1 volume ratio. Then, in the second step, similar reagents are injected a second time (however, according to about a 1:2 volume ratio, iron to salt) to form magnetite. The magnetite formation is facilitated, in part, due to slow intrusion of oxygen into the soil from the surface. The invention techniques are suited to injection of reagents into soil in proximity to a contamination plume or source allowing in situ formation of the reactive barrier at the location of waste or hazardous material. Mixing of reagents to form. precipitate is mediated and enhanced through movement of reagents in soil as a result of phenomena including capillary action, movement of groundwater, soil washing and reagent injection pressure.

Synthetic fermentation of bioactive non-ribosomal peptides without organisms, enzymes or reagents

NASA Astrophysics Data System (ADS)

Huang, Yi-Lin; Bode, Jeffrey W.

2014-10-01

Microbial fermentation can rapidly provide potent compounds that can be easily screened for biological activity, and the active components can be isolated. Its success in drug discovery has inspired extensive efforts to modulate and control the products. In this Article, we document a ‘synthetic fermentation’ of bioactive, unnatural peptides ‘grown’ from small building blocks in water using amide-forming ligations. No organisms, enzymes or reagents are needed. The sequences, structures and compositions of the products can be modulated by adjusting the building blocks and conditions. No specialized knowledge of organic chemistry or handling of toxic material is required to produce complex organic molecules. The ‘fermentations’ can be conducted in arrays and screened for biological activity without isolation or workup. As a proof-of-concept, about 6,000 unnatural peptides were produced from just 23 building blocks, from which a hepatitis C virus NS3/4A protease inhibitor with a half-maximum inhibitory concentration of 1.0 μM was identified and characterized.

Diff-seq: A high throughput sequencing-based mismatch detection assay for DNA variant enrichment and discovery

PubMed Central

Karas, Vlad O; Sinnott-Armstrong, Nicholas A; Varghese, Vici; Shafer, Robert W; Greenleaf, William J; Sherlock, Gavin

2018-01-01

Abstract Much of the within species genetic variation is in the form of single nucleotide polymorphisms (SNPs), typically detected by whole genome sequencing (WGS) or microarray-based technologies. However, WGS produces mostly uninformative reads that perfectly match the reference, while microarrays require genome-specific reagents. We have developed Diff-seq, a sequencing-based mismatch detection assay for SNP discovery without the requirement for specialized nucleic-acid reagents. Diff-seq leverages the Surveyor endonuclease to cleave mismatched DNA molecules that are generated after cross-annealing of a complex pool of DNA fragments. Sequencing libraries enriched for Surveyor-cleaved molecules result in increased coverage at the variant sites. Diff-seq detected all mismatches present in an initial test substrate, with specific enrichment dependent on the identity and context of the variation. Application to viral sequences resulted in increased observation of variant alleles in a biologically relevant context. Diff-Seq has the potential to increase the sensitivity and efficiency of high-throughput sequencing in the detection of variation. PMID:29361139

A new paper-based platform technology for point-of-care diagnostics.

PubMed

Gerbers, Roman; Foellscher, Wilke; Chen, Hong; Anagnostopoulos, Constantine; Faghri, Mohammad

2014-10-21

Currently, the Lateral flow Immunoassays (LFIAs) are not able to perform complex multi-step immunodetection tests because of their inability to introduce multiple reagents in a controlled manner to the detection area autonomously. In this research, a point-of-care (POC) paper-based lateral flow immunosensor was developed incorporating a novel microfluidic valve technology. Layers of paper and tape were used to create a three-dimensional structure to form the fluidic network. Unlike the existing LFIAs, multiple directional valves are embedded in the test strip layers to control the order and the timing of mixing for the sample and multiple reagents. In this paper, we report a four-valve device which autonomously directs three different fluids to flow sequentially over the detection area. As proof of concept, a three-step alkaline phosphatase based Enzyme-Linked ImmunoSorbent Assay (ELISA) protocol with Rabbit IgG as the model analyte was conducted to prove the suitability of the device for immunoassays. The detection limit of about 4.8 fm was obtained.

Single Chain Antibodies as Tools to Study transforming growth factor-β-Regulated SMAD Proteins in Proximity Ligation-Based Pharmacological Screens.

PubMed

Blokzijl, Andries; Zieba, Agata; Hust, Michael; Schirrmann, Thomas; Helmsing, Saskia; Grannas, Karin; Hertz, Ellen; Moren, Anita; Chen, Lei; Söderberg, Ola; Moustakas, Aristidis; Dübel, Stefan; Landegren, Ulf

2016-06-01

The cellular heterogeneity seen in tumors, with subpopulations of cells capable of resisting different treatments, renders single-treatment regimens generally ineffective. Accordingly, there is a great need to increase the repertoire of drug treatments from which combinations may be selected to efficiently target sets of pathological processes, while suppressing the emergence of resistance mutations. In this regard, members of the TGF-β signaling pathway may furnish new, valuable therapeutic targets. In the present work, we developed in situ proximity ligation assays (isPLA) to monitor the state of the TGF-β signaling pathway. Moreover, we extended the range of suitable affinity reagents for this analysis by developing a set of in-vitro-derived human antibody fragments (single chain fragment variable, scFv) that bind SMAD2 (Mothers against decapentaplegic 2), 3, 4, and 7 using phage display. These four proteins are all intracellular mediators of TGF-β signaling. We also developed an scFv specific for SMAD3 phosphorylated in the linker domain 3 (p179 SMAD3). This phosphorylation has been shown to inactivate the tumor suppressor function of SMAD3. The single chain affinity reagents developed in the study were fused tocrystallizable antibody fragments (Fc-portions) and expressed as dimeric IgG-like molecules having Fc domains (Yumabs), and we show that they represent valuable reagents for isPLA.Using these novel assays, we demonstrate that p179 SMAD3 forms a complex with SMAD4 at increased frequency during division and that pharmacological inhibition of cyclin-dependent kinase 4 (CDK4)(1) reduces the levels of p179SMAD3 in tumor cells. We further show that the p179SMAD3-SMAD4 complex is bound for degradation by the proteasome. Finally, we developed a chemical screening strategy for compounds that reduce the levels of p179SMAD3 in tumor cells with isPLA as a read-out, using the p179SMAD3 scFv SH544-IIC4. The screen identified two kinase inhibitors, known inhibitors of the insulin receptor, which decreased levels of p179SMAD3/SMAD4 complexes, thereby demonstrating the suitability of the recombinant affinity reagents applied in isPLA in screening for inhibitors of cell signaling. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Mechanism of Electrophilic Fluorination with Pd(IV): Fluoride Capture and Subsequent Oxidative Fluoride Transfer†, ‡

PubMed Central

Brandt, Jochen R.; Lee, Eunsung; Boursalian, Gregory B.

2013-01-01

Electrophilic fluorinating reagents derived from fluoride are desirable for the synthesis of 18F-labeled molecules for positron emission tomography (PET). Here, we study the mechanism by which a Pd(IV)-complex captures fluoride and subsequently transfers it to nucleophiles. The intermediate Pd(IV)-F is formed with high rates even at the nano- to micromolar fluoride concentrations typical for radiosyntheses with 18F due to fast formation of an outer-sphere complex between fluoride and Pd(IV). The subsequent fluorine transfer from the Pd(IV)-F complex is proposed to proceed through an unusual SET/fluoride transfer/SET mechanism. The findings detailed in this manuscript provide a theoretical foundation suitable for addressing a more general approach for electrophilic fluorination with high specific activity 18F PET imaging. PMID:24376910

Cu2ZnSnS4 Nanoparticles Synthesized by a Novel Diethylenetriamine-Assisted Hydrothermal Method

NASA Astrophysics Data System (ADS)

Liang, Feng; Gao, Juan; Zou, Changwei; Shao, Lexi

2018-05-01

A diethylenetriamine (DETA)-assisted hydrothermal method was explored for the synthesis of kesterite Cu2ZnSnS4 (CZTS) nanoparticles. As complexing agent, DETA was employed to dissolve sulfur and to form complex with metal ions. By introducing DETA to the system, pure CZTS nanoparticles with bandgap of 1.54 eV could be successfully obtained and the agglomeration of samples could be restrained by increasing the concentration of DETA. From the discussion about the experimental results, the formation mechanism of CZTS nanoparticles was proposed. As the reagents used in this experiment is low-toxic and inexpensive, this method was considered as an effective and green route for the synthesis of CZTS nanoparticles.

Synthesis and Modification of Carboxylated Polyphenylenes and Phenylated Polyimides

DTIC Science & Technology

1976-03-01

corresponding grignard reagent , which was allowed to react with DMF19 to provide the benzalde- hyde 50. This aldehyde, however, failed to undergo a benzoin...bromophenylethynyl )-trimethyl- silane in 100 ml THF was refluxed 2 hr with 1.6 g (0.066 g atm) of magnesium to form the Grignard reagent . To the...toluene (Table 2). The crown other reagent , however, could not be completely removed from the resulting ionomer. Treatment of the carboxylated

Electrochemical pesticide detection with AutoDip--a portable platform for automation of crude sample analyses.

PubMed

Drechsel, Lisa; Schulz, Martin; von Stetten, Felix; Moldovan, Carmen; Zengerle, Roland; Paust, Nils

2015-02-07

Lab-on-a-chip devices hold promise for automation of complex workflows from sample to answer with minimal consumption of reagents in portable devices. However, complex, inhomogeneous samples as they occur in environmental or food analysis may block microchannels and thus often cause malfunction of the system. Here we present the novel AutoDip platform which is based on the movement of a solid phase through the reagents and sample instead of transporting a sequence of reagents through a fixed solid phase. A ball-pen mechanism operated by an external actuator automates unit operations such as incubation and washing by consecutively dipping the solid phase into the corresponding liquids. The platform is applied to electrochemical detection of organophosphorus pesticides in real food samples using an acetylcholinesterase (AChE) biosensor. Minimal sample preparation and an integrated reagent pre-storage module hold promise for easy handling of the assay. Detection of the pesticide chlorpyrifos-oxon (CPO) spiked into apple samples at concentrations of 10(-7) M has been demonstrated. This concentration is below the maximum residue level for chlorpyrifos in apples defined by the European Commission.

The cytometric future: it ain't necessarily flow!

PubMed

Shapiro, Howard M

2011-01-01

Initial approaches to cytometry for classifying and characterizing cells were based on microscopy; it was necessary to collect relatively high-resolution images of cells because only a few specific reagents usable for cell identification were available. Although flow cytometry, now the dominant cytometric technology, typically utilizes lenses similar to microscope lenses for light collection, improved, more quantitative reagents allow the necessary information to be acquired in the form of whole-cell measurements of the intensities of light transmission, scattering, and/or fluorescence.Much of the cost and complexity of both automated microscopes and flow cytometers arises from the necessity for them to measure one cell at a time. Recent developments in digital camera technology now offer an alternative in which one or more low-magnification, low-resolution images are made of a wide field containing many cells, using inexpensive light-emitting diodes (LEDs) for illumination. Minimalist widefield imaging cytometers can provide a smaller, less complex, and substantially less expensive alternative to flow cytometry, critical in systems intended for in resource-poor areas. Minimalism is, likewise, a good philosophy in developing instrumentation and methodology for both clinical and large-scale research use; it simplifies quality assurance and compliance with regulatory requirements, as well as reduces capital outlays, material costs, and personnel training requirements. Also, importantly, it yields "greener" technology.

Phosphate determination in seawater: toward an autonomous electrochemical method.

PubMed

Jońca, Justyna; León Fernández, Violeta; Thouron, Danièle; Paulmier, Aurélien; Graco, Michelle; Garçon, Véronique

2011-12-15

Initial steps to create an autonomous in situ electrochemical sensor for orthophosphate determination in seawater are presented. First, the optimal conditions to form the molybdophosphate complex in artificial seawater medium were determined by addition of sulphuric acid and sodium molybdate to the solution containing orthophosphate. Secondly, the anodic oxidation of molybdenum to form molybdate ions and protons was used to create the molybdophosphate complex without addition of any liquid reagents. The molybdophosphate complex is detectable by amperometry with an average precision of 2.2% for the concentration range found in the open ocean and the detection limit is 0.12 μM. Three solutions are proposed to address the silicate interferences issue and one of these methods is used for the natural samples collected in the coastal waters offshore Peru during the Pelagico 1011-12-BIC OLAYA cruise in November-December 2010. Results showed a good precision with an average of 2.5% and a reasonable deviation of the amperometric analysis as compared with colorimetric measurements (4.9%). Copyright © 2011 Elsevier B.V. All rights reserved.

Malachite green mediates homodimerization of antibody VL domains to form a fluorescent ternary complex with singular symmetric interfaces

PubMed Central

Szent-Gyorgyi, Chris; Stanfield, Robyn L.; Andreko, Susan; Dempsey, Alison; Ahmed, Mushtaq; Capek, Sara; Waggoner, Alan; Wilson, Ian A.; Bruchez, Marcel P.

2013-01-01

We report that a symmetric small molecule ligand mediates the assembly of antibody light chain variable domains (VLs) into a correspondent symmetric ternary complex with novel interfaces. The L5* Fluorogen Activating Protein (FAP) is a VL domain that binds malachite green dye (MG) to activate intense fluorescence. Crystallography of liganded L5* reveals a 2:1 protein:ligand complex with inclusive C2 symmetry, where MG is almost entirely encapsulated between an antiparallel arrangement of the two VL domains. Unliganded L5* VL domains crystallize as a similar antiparallel VL/VL homodimer. The complementarity determining regions (CDRs) are spatially oriented to form novel VL/VL and VL/ligand interfaces that tightly constrain a propeller conformer of MG. Binding equilibrium analysis suggests highly cooperative assembly to form a very stable VL/MG/VL complex, such that MG behaves as a strong chemical inducer of dimerization. Fusion of two VL domains into a single protein tightens MG binding over 1,000-fold to low picomolar affinity without altering the large binding enthalpy, suggesting that bonding interactions with ligand and restriction of domain movements make independent contributions to binding. Fluorescence activation of a symmetrical fluorogen provides a selection mechanism for the isolation and directed evolution of ternary complexes where unnatural symmetric binding interfaces are favored over canonical antibody interfaces. As exemplified by L5*, these self-reporting complexes may be useful as modulators of protein association or as high affinity protein tags and capture reagents. PMID:23978698

Distribution and variability of redox zones controlling spatial variability of arsenic in the Mississippi River Valley alluvial aquifer, southeastern Arkansas

USGS Publications Warehouse

Sharif, M.U.; Davis, R.K.; Steele, K.F.; Kim, B.; Hays, P.D.; Kresse, T.M.; Fazio, J.A.

2008-01-01

Twenty one of 118 irrigation water wells in the shallow (25-30??m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (< 0.5 to 77????g/L) exceeding 10????g/L. Sediment and groundwater samples were collected and analyzed from the sites of the highest, median, and lowest concentrations of As in groundwater in the alluvial aquifers located at Jefferson County, Arkansas. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO3-leachable fraction of As and other compounds in sediments. The Chao reagent (0.25??M hydroxylamine hydrochloride in 0.25??M HCl) removes amorphous Fe and Mn oxides and oxyhydroxides (present as coatings on grains and amorphous minerals) by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO3 extraction removes mostly crystalline metal oxides and all other labile forms of As. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70????g/kg) exchangeable As is only present at shallow depth (0-1??m below ground surface). Arsenic is positively correlated to Fe extracted by Chao reagent (r = 0.83) and hot HNO3 (r = 0.85). Arsenic extracted by Chao reagent decreases significantly with depth as compared to As extracted by hot HNO3. Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO3) is positively correlated (r = 0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative abundance of reducible Fe decreases noticeably with depth. The amount of reducible Fe, as well as As complexed to amorphous Fe and Mn oxides and oxyhydroxides decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from hydrous ferric oxides (HFO) by microbially-mediated reductive dissolution and aging of HFO to crystalline phases. Hydrogeochemical data suggests that the groundwater in the area falls in the mildly reducing (suboxic) to relatively highly reducing (anoxic) zone, and points to reductive dissolution of HFO as the dominant As release mechanism. Spatial variability of gypsum solubility and simultaneous SO42- reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of As in groundwater in the area. ?? 2008 Elsevier B.V. All rights reserved.

Nuclear reactor cooling system decontamination reagent regeneration. [PWR; BWR

DOEpatents

Anstine, L.D.; James, D.B.; Melaika, E.A.; Peterson, J.P. Jr.

1980-06-06

An improved method for decontaminating the coolant system of water-cooled nuclear power reactors and for regenerating the decontamination solution is described. A small amount of one or more weak-acid organic complexing agents is added to the reactor coolant, and the pH is adjusted to form a decontamination solution which is circulated throughout the coolant system to dissolve metal oxides from the interior surfaces and complex the resulting metal ions and radionuclide ions. The coolant containing the complexed metal ions and radionuclide ions is passed through a strong-base anion exchange resin bed which has been presaturated with a solution containing the complexing agents in the same ratio and having the same pH as the decontamination solution. As the decontamination solution passes through the resin bed, metal-complexed anions are exchanged for the metal-ion-free anions on the bed, while metal-ion-free anions in the solution pass through the bed, thus removing the metal ions and regenerating the decontamination solution.

Nuclear reactor cooling system decontamination reagent regeneration

DOEpatents

Anstine, Larry D.; James, Dean B.; Melaika, Edward A.; Peterson, Jr., John P.

1985-01-01

An improved method for decontaminating the coolant system of water-cooled nuclear power reactors and for regenerating the decontamination solution. A small amount of one or more weak-acid organic complexing agents is added to the reactor coolant, and the pH is adjusted to form a decontamination solution which is circulated throughout the coolant system to dissolve metal oxides from the interior surfaces and complex the resulting metal ions and radionuclide ions. The coolant containing the complexed metal ions and radionuclide ions is passed through a strong-base anion exchange resin bed which has been presaturated with a solution containing the complexing agents in the same ratio and having the same pH as the decontamination solution. As the decontamination solution passes through the resin bed, metal-complexed anions are exchanged for the metal-ion-free anions on the bed, while metal-ion-free anions in the solution pass through the bed, thus removing the metal ions and regenerating the decontamination solution.

Stereospecific nickel-catalyzed cross-coupling reactions of alkyl Grignard reagents and identification of selective anti-breast-cancer agents.

PubMed

Yonova, Ivelina M; Johnson, A George; Osborne, Charlotte A; Moore, Curtis E; Morrissette, Naomi S; Jarvo, Elizabeth R

2014-02-24

Alkyl Grignard reagents that contain β-hydrogen atoms were used in a stereospecific nickel-catalyzed cross-coupling reaction to form C(sp(3))-C(sp(3)) bonds. Aryl Grignard reagents were also utilized to synthesize 1,1-diarylalkanes. Several compounds synthesized by this method exhibited selective inhibition of proliferation of MCF-7 breast cancer cells. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Olefin Metathesis in Peptidomimetics, Dynamic Combinatorial Chemistry, and Molecular Imprinting

DTIC Science & Technology

2006-08-01

aryl iodide to the Grignard reagent . Treatment of the magnesium compound with allyl bromide and CuCN·2LiCl afforded benzoate 4-11, which was then...cyclization of a linear peptide by conventional coupling agents to form a new amide bond (Scheme 1-12)36,44 Some common reagents are...dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), and expensive reagents such as HATU or PyBroP, which are more efficient.44 Racemization of the chiral

Copper-catalyzed synthesis of phenanthridine derivatives under an oxygen atmosphere starting from biaryl-2-carbonitriles and Grignard reagents.

PubMed

Zhang, Line; Ang, Gim Yean; Chiba, Shunsuke

2010-08-20

A copper-catalyzed synthesis of phenanthridine derivatives was developed starting from biaryl-2-carbonitriles and Grignard reagents. The present transformation is carried out by a sequence of nucleophilic addition of Grignard reagents to biaryl-2-carbonitriles to form N-H imines and their Cu-catalyzed C-N bond formation on the aromatic C-H bond, where molecular oxygen is a prerequisite to achieve the catalytic process.

Highly sensitive and selective spectrophotometric method for determination of trace gold in geological samples with 5-(2-hydroxy-5-nitrophenylazo)rhodanine.

PubMed

Zaijun, Li; Jiaomai, Pan; Jian, Tang

2003-02-01

A excellent sensitive and selective method for spectrophotometric determination of trace gold has been developed, the method is based on the color reaction of gold(III) with new reagent 5-(2-hydroxy-5-nitrophenylazo)rhodanine (HNAR). Under optimal conditions, HNAR reacts with gold(III) to form a 1:5 orange complex, which has an maximum absorption peak at 480 nm. Maximum enhancement of the absorbance of the complex was obtained in the presence of the mixed surfactant of Triton X-100 and CTMAB; the reaction completed rapidly and the absorbance is stable for 5 h at least at 20 degrees C; 0-48 microg L(-1) Au(III) obeyed Beer's law. The apparent molar absorptivity of the complex, Sandell's sensitivity, the limit of quantification, the limit of detection and relative standard deviation were found to be 2.0x10(6) L mol(-1) cm(-1), 0.000,098,483 micro g cm(-2), 1.02 ng mL(-1), 0.35 ng mL(-1) and 1.09%, respectively. The effect of co-existing ions was studied seriously; most metal ions can be tolerated in considerable amounts. Its sensitivity and selectivity are remarkably superior to other reagents in the literature. The proposed method was used successfully to determine trace gold in geological samples. Moreover, the synthesis, characteristics and analytical reaction of HNAR with gold are also described in detail.

Analysis of the causes of discrepancies in troponin I concentrations as measured by ARCHITECT High-Sensitive Troponin I ST and STACIA CLEIA cTnI.

PubMed

Kondo, Takashi; Kobayashi, Daisuke; Mochizuki, Maki; Asanuma, Kouichi; Takahashi, Satoshi

2017-01-01

Background Recently developed reagents for the highly sensitive measurement of cardiac troponin I are useful for early diagnosis of acute coronary syndrome. However, differences in measured values between these new reagents and previously used reagents have not been well studied. In this study, we aimed to compare the values between ARCHITECT High-Sensitive Troponin I ST (newly developed reagents), ARCHITECT Troponin I ST and STACIA CLEIA cardiac troponin I (two previously developed reagent kits). Methods Gel filtration high-performance liquid chromatography was used to analyse the causes of differences in measured values. Results The measured values differed between ARCHITECT High-Sensitive Troponin I ST and STACIA CLEIA cardiac troponin I reagents (r = 0.82). Cross-reactivity tests using plasma with added skeletal-muscle troponin I resulted in higher reactivity (2.17-3.03%) for the STACIA CLEIA cardiac troponin I reagents compared with that for the ARCHITECT High-Sensitive Troponin I ST reagents (less than 0.014%). In addition, analysis of three representative samples using gel filtration high-performance liquid chromatography revealed reagent-specific differences in the reactivity against each cardiac troponin I complex; this could explain the differences in values observed for some of the samples. Conclusion The newly developed ARCHITECT High-Sensitive Troponin I ST reagents were not affected by the presence of skeletal-muscle troponin I in the blood and may be useful for routine examinations.

Diazo compounds in continuous-flow technology.

PubMed

Müller, Simon T R; Wirth, Thomas

2015-01-01

Diazo compounds are very versatile reagents in organic chemistry and meet the challenge of selective assembly of structurally complex molecules. Their leaving group is dinitrogen; therefore, they are very clean and atom-efficient reagents. However, diazo compounds are potentially explosive and extremely difficult to handle on an industrial scale. In this review, it is discussed how continuous flow technology can help to make these powerful reagents accessible on large scale. Microstructured devices can improve heat transfer greatly and help with the handling of dangerous reagents safely. The in situ formation and subsequent consumption of diazo compounds are discussed along with advances in handling diazomethane and ethyl diazoacetate. The potential large-scale applications of a given methodology is emphasized. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A matrix-assisted laser desorption/ionization mass spectroscopy method for the analysis of small molecules by integrating chemical labeling with the supramolecular chemistry of cucurbituril.

PubMed

Ding, Jun; Xiao, Hua-Ming; Liu, Simin; Wang, Chang; Liu, Xin; Feng, Yu-Qi

2018-10-05

Although several methods have realized the analysis of low molecular weight (LMW) compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) by overcoming the problem of interference with MS signals in the low mass region derived from conventional organic matrices, this emerging field still requires strategies to address the issue of analyzing complex samples containing LMW components in addition to the LMW compounds of interest, and solve the problem of lack of universality. The present study proposes an integrated strategy that combines chemical labeling with the supramolecular chemistry of cucurbit [n]uril (CB [n]) for the MALDI MS analysis of LMW compounds in complex samples. In this strategy, the target LMW compounds are first labeled by introducing a series of bifunctional reagents that selectively react with the target analytes and also form stable inclusion complexes with CB [n]. Then, the labeled products act as guest molecules that readily and selectively form stable inclusion complexes with CB [n]. This strategy relocates the MS signals of the LMW compounds of interest from the low mass region suffering high interference to the high mass region where interference with low mass components is absent. Experimental results demonstrate that a wide range of LMW compounds, including carboxylic acids, aldehydes, amines, thiol, and cis-diols, can be successfully detected using the proposed strategy, and the limits of detection were in the range of 0.01-1.76 nmol/mL. In addition, the high selectivity of the labeling reagents for the target analytes in conjunction with the high selectivity of the binding between the labeled products and CB [n] ensures an absence of signal interference with the non-targeted LMW components of complex samples. Finally, the feasibility of the proposed strategy for complex sample analysis is demonstrated by the accurate and rapid quantitative analysis of aldehydes in saliva and herbal medicines. As such, this work not only provides an alternative method for the detection of various LMW compounds using MALDI MS, but also can be applied to the selective and high-throughput analysis of LMW analytes in complex samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Genotoxicity assessment of membrane concentrates of landfill leachate treated with Fenton reagent and UV-Fenton reagent using human hepatoma cell line.

PubMed

Wang, Guifang; Lu, Gang; Yin, Pinghe; Zhao, Ling; Yu, Qiming Jimmy

2016-04-15

Membrane concentrates of landfill leachates contain organic and inorganic contaminants that could be highly toxic and carcinogenic. In this paper, the genotoxicity of membrane concentrates before and after Fenton and UV-Fenton reagent was assessed. The cytotoxicity and genotoxicity was determined by using the methods of methyltetrazolium (MTT), cytokinesis-block micronucleus (CBMN) and comet assay in human hepatoma cells. MTT assay showed a cytotoxicity of 75% after 24h of exposure to the highest tested concentration of untreated concentrates, and no cytotoxocity for UV-Fenton and Fenton treated concentrates. Both CBMN and comet assays showed increased levels of genotoxicity in cells exposed to untreated concentrates, compared to those occurred in cells exposed to UV-Fenton and Fenton reagent treated concentrates. There was no significant difference between negative control and UV-Fenton treated concentrates for micronucleus and comet assay parameters. UV-Fenton and Fenton treatment, especially the former, were effective methods for degradation of bisphenol A and nonylphenol in concentrates. These findings showed UV-Fenton and Fenton reaction were effective methods for treatment of such complex concentrates, UV-Fenton reagent provided toxicological safety of the treated effluent, and the genotoxicity assays were found to be feasible tools for assessment of toxicity risks of complex concentrates. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectrophotometric studies of reactions between pseudo-ephedrine with different inorganic and organic reagents and its micro-determination in pure and in pharmaceutical preparations.

PubMed

Zayed, M A; El-Rasheedy, El-Gazy A

2012-03-01

Two simple, sensitive, cheep and reliable spectrophotometric methods are suggested for micro-determination of pseudoephedrine in its pure form and in pharmaceutical preparation (Sinofree Tablets). The first one depends on the drug reaction with inorganic sensitive reagent like molybdate anion in aqueous media via formation of ion-pair mechanism. The second one depends on the drug reaction with π-acceptor reagent like DDQ in non-aqueous media via formation of charge transfer complex. These reactions were studied under various conditions and the optimum parameters were selected. Under proper conditions the suggested procedures were successfully applied for micro-determination of pseudoephedrine in pure and in Sinofree Tablets without interference from excepients. The values of SD, RSD, recovery %, LOD, LOQ and Sandell sensitivity refer to the high accuracy and precession of the applied procedures. The results obtained were compared with the data obtained by an official method, referring to confidence and agreement with DDQ procedure results; but it referred to the more accuracy of the molybdate data. Therefore, the suggested procedures are now successfully being applied in routine analysis of this drug in its pharmaceutical formulation (Sinofree) in Saudi Arabian Pharmaceutical Company (SPIMACO) in Boridah El-Qaseem, Saudi Arabia instead of imported kits had been previously used. Copyright © 2011 Elsevier B.V. All rights reserved.

Organometallic Palladium Reagents for Cysteine Bioconjugation

PubMed Central

Vinogradova, Ekaterina V.; Zhang, Chi; Spokoyny, Alexander M.; Pentelute, Bradley L.; Buchwald, Stephen L.

2015-01-01

Transition-metal based reactions have found wide use in organic synthesis and are used frequently to functionalize small molecules.1,2 However, there are very few reports of using transition-metal based reactions to modify complex biomolecules3,4, which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature, and mild pH) and the existence of multiple, reactive functional groups found in biopolymers. Here we report that palladium(II) complexes can be used for efficient and highly selective cysteine conjugation reactions. The bioconjugation reaction is rapid and robust under a range of biocompatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants, and external thiol nucleophiles. The broad utility of the new bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody-drug conjugates. These palladium complexes show potential as a new set of benchtop reagents for diverse bioconjugation applications. PMID:26511579

Synthesis and Reactivity of Backfluorinated NHC Carbene Complexes (Briefing Charts)

DTIC Science & Technology

2015-07-01

Distribution A: Approved for public release 13 Preparation of Perfluoroalkyl Grignard Reagents F(CF2CF2)nCH2CH2I Mg, Et2O ref lux F(CF2CF2)nCH2CH2MgI F...Synthetic Method #1 Grignard Addition/Reduction/Cyclization • Very general reaction pathway: suitable for all Grignard reagents • Attempts at...dialkylation unsuccessful • Slight excess of Grignard reagent ensures complete monoalkylation N N MesMes N N MesMes F2 C MgX Et2O, rt N N MesMes CF2 MgX 2

Forced-flow chromatographic determination of calcium and magnesium with continuous spectrophotometric detection

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

Arguello, M.D.

1977-12-01

Modifications to the forced-flow chromatograph include a flow-through pH monitor to continuously monitor the pH of the final effluent and an active low-pass filter to eliminate noise in the spectrophotometric detector. All separations are performed using partially sulfonated XAD-2 as the ion exchanger. Elution of calcium and magnesium is accomplished using ammonium chloride and ethylenediammonium chloride solutions. Calcium and magnesium are detected by means of Arsenazo I and PAR-ZnEDTA color-forming reagents. Other metal ions are detected by means of PAR and Chromazurol S color-forming reagents. Calcium and magnesium distribution coefficients on partially sulfonated XAD-2 as functions of ammonium chloride andmore » ethylenediammonium chloride concentration are given together with distribution coefficients of other metal ions. Methods for the selective elution of interfering metal ions prior to the elution of calcium and magnesium are described. Beryllium and aluminum are selectively eluted with sulfosalicylic acid. Those elements forming anionic chloride complexes are selectively eluted with HCl-acetone. Nickel is selectively eluted with HCl-acetone-dimethylglyoxime. Synthetic samples containing calcium and magnesium, both alone and in combination with alkali metals, strontium, barium, beryllium, aluminum, transition metals, and rare earths, are analyzed. Hard water samples are analyzed for calcium and magnesium and the results compared to those obtained by EDTA titration, atomic absorption spectroscopy, and plasma emission spectroscopy. Several clinical serum samples are analyzed for calcium and magnesium and the results compared to those obtained by atomic absorption spectroscopy.« less

New electrolyte systems for capillary zone electrophoresis of metal cations and non-ionic organic compounds

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

Shi, Youchun

Excellent separations of metal ions can be obtained very quickly by capillary electrophoresis provided a weak complexing reagent is incorporated into the electrolyte to alter the effective mobilities of the sample ions. Indirect photometric detection is possible by also adding a UV-sensitive ion to the electrolyte. Separations are described using phthalate, tartrate, lactate or hydroxyisobutyrate as the complexing reagent. A separation of twenty-seven metal ions was achieved in only 6 min using a lactate system. A mechanism for the separation of lanthanides is proposed for the hydroxyisobutyrate system.

Multifunctional Pt(II) Reagents: Covalent Modifications of Pt Complexes Enable Diverse Structural Variation and In-Cell Detection.

PubMed

White, Jonathan D; Haley, Michael M; DeRose, Victoria J

2016-01-19

To enhance the functionality of Pt-based reagents, several strategies have been developed that utilize Pt compounds modified with small, reactive handles. This Account encapsulates work done by us and other groups regarding the use of Pt(II) compounds with reactive handles for subsequent elaboration with fluorophores or other functional moieties. Described strategies include the incorporation of substituents for well-known condensation or nucleophilic displacement-type reactions and their use, for example, to tether spectroscopic handles to Pt reagents for in vivo investigation. Other chief uses of displacement-type reactions have included tethering various small molecules exhibiting pharmacological activity directly to Pt, thus adding synergistic effects. Click chemistry-based ligation techniques have also been applied, primarily with azide- and alkyne-appended Pt complexes. Orthogonally reactive click chemistry reactions have proven invaluable when more traditional nucleophilic displacement reactions induce side-reactivity with the Pt center or when systematic functionalization of a larger number of Pt complexes is desired. Additionally, a diverse assortment of Pt-fluorophore conjugates have been tethered via click chemistry conjugation. In addition to providing a convenient synthetic path for diversifying Pt compounds, the use of click-capable Pt complexes has proved a powerful strategy for postbinding covalent modification and detection with fluorescent probes. This strategy bypasses undesirable influences of the fluorophore camouflaged as reactivity due to Pt that may be present when detecting preattached Pt-fluorophore conjugates. Using postbinding strategies, Pt reagent distributions in HeLa and lung carcinoma (NCI-H460) cell cultures were observed with two different azide-modified Pt compounds, a monofunctional Pt(II)-acridine type and a difunctional Pt(II)-neutral complex. In addition, cellular distribution was observed with an alkyne-appended difunctional Pt(II)-neutral complex analogous in structure to the aforementioned difunctional azide-Pt(II) reagent. In all cases, significant accumulation of Pt in the nucleolus of cells was observed, in addition to broader localization in the nucleus and cytoplasm of the cell. Using the same strategy of postbinding click modification with fluorescent probes, Pt adducts were detected and roughly quantified on rRNA and tRNA from Pt-treated Saccharomyces cerevisiae; rRNA adducts were found to be relatively long-lived and not targeted for immediate degradation. Finally, the utility and feasibility of the alkyne-appended Pt(II) compound has been further demonstrated with a turn-on fluorophore, dansyl azide, in fluorescent detection of DNA in vitro. In all, these modifications utilizing reactive handles have allowed for the diversification of new Pt reagents, as well as providing cellular localization information on the modified Pt compounds.

The Effect of Changing Reagent upon Stereoselectivity 1a

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

Stocker, Jack H.; Sidisunthorn, Padet; Benjamin, Ben M.

1960-08-01

The stereoselectivities exhibited during several reactions in which a second, adjacent asymmetric carbon atom is formed were observed. The effect of changing the organometallic reagent from phenyllithium to phenylmagnesium iodide to pherylmagnesium bromide to phenylmagnesium chloride was also studied in the addition of these reagents to biacetyl or to phenylacetoin. It was shown that the product dl: meso ratio is greater than one when either phenyllithium or phenylmagnesium iodide is eraployed, and less than one when phenylinagnesium bromide or chloride is employed. A similar series of reactions between benzil or methylbenzoin and the corresponding methyl reagents is also reported. Allmore » results are discussed in terms of the hypothetical intermediates.« less

Method for removal and stabilization of mercury in mercury-containing gas streams

DOEpatents

Broderick, Thomas E.

2005-09-13

The present invention is directed to a process and apparatus for removing and stabilizing mercury from mercury-containing gas streams. A gas stream containing vapor phase elemental and/or speciated mercury is contacted with reagent, such as an oxygen-containing oxidant, in a liquid environment to form a mercury-containing precipitate. The mercury-containing precipitate is kept or placed in solution and reacts with one or more additional reagents to form a solid, stable mercury-containing compound.

A commercialized, continuous flow fiber optic sensor for trichloroethylene and haloforms

NASA Technical Reports Server (NTRS)

Wells, James C.; Johnson, Mark D.

1994-01-01

Purus, Inc. has commercialized a fiber optic chemical sensor using technology developed by Lawrence Livermore National Laboratory and licensed from The University of California. The basis for the sensor is the development of color within a reagent when exposed to an analyte. The sensor consists of an optrode, reagent delivery and recover system, fiber optic transmitter-receiver, controller, and display. Reagent is pumped through the optrode. Analyte diffuses across a gas permeable membrane and reacts with the reagent to form a colored product. The colored product is detected by measuring the absorbance of light from a 568 nm diode. Reagents are currently available for TCE and trihalomethanes. Initial reagent chemistry is based on the Fujiwara alkaline pyridine reaction. The optrode contacts only gas streams, but the volatility of the current analytes also allows measurements of aqueous streams, without being affected by aqueous interferents that are non-volatile. Sensitivity of the sensor has been demonstrated to 5 ppb aqueous solutions and 0.1 ppmv in flowing gas streams.

Reactive Derivatives of Nucleic Acids and Their Components as Affinity Reagents

NASA Astrophysics Data System (ADS)

Knorre, Dmitrii G.; Vlasov, Valentin V.

1985-09-01

The review is devoted to derivatives of nucleic acids and their components — nucleotides, nucleoside triphosphates, and oligonucleotides carrying reactive groups. Such derivatives are important tools for the investigation of protein-nucleic acid interactions and the functional topography of complex protein and nucleoprotein structures and can give rise to the prospect of being able to influence in a highly selective manner living organisms, including the nucleic acids and the nucleoproteins of the genetic apparatus. The review considers the principal groups of such reagents, the methods of their synthesis, and their properties which determine the possibility of their use for the selective (affinity) modification of biopolymers. The general principles of the construction of affinity reagents and their applications are analysed in relation to nucleotide affinity reagents. The bibliography includes 121 references.

Highly Sensitive Immunoassay Based on Controlled Rehydration of Patterned Reagents in a 2-Dimensional Paper Network

PubMed Central

2015-01-01

We have demonstrated a multistep 2-dimensional paper network immunoassay based on controlled rehydration of patterned, dried reagents. Previous work has shown that signal enhancement improves the limit of detection in 2-dimensional paper network assays, but until now, reagents have only been included as wet or dried in separate conjugate pads placed at the upstream end of the assay device. Wet reagents are not ideal for point-of-care because they must be refrigerated and typically limit automation and require more user steps. Conjugate pads allow drying but do not offer any control of the reagent distribution upon rehydration and can be a source of error when pads do not contact the assay membrane uniformly. Furthermore, each reagent is dried on a separate pad, increasing the fabrication complexity when implementing multistep assays that require several different reagents. Conversely, our novel method allows for consistent, controlled rehydration from patterned reagent storage depots directly within the paper membrane. In this assay demonstration, four separate reagents were patterned in different regions of the assay device: a gold-antibody conjugate used for antigen detection and three different signal enhancement components that must not be mixed until immediately before use. To show the viability of patterning and drying reagents directly onto a paper device for dry reagent storage and subsequent controlled release, we tested this device with the malaria antigen Plasmodium falciparum histidine-rich protein 2 (PfHRP2) as an example of target analyte. In this demonstration, the signal enhancement step increases the visible signal by roughly 3-fold and decreases the analytical limit of detection by 2.75-fold. PMID:24882058

Development of Ultra-Super Sensitive Immunohistochemistry and Its Application to the Etiological Study of Adult T-Cell Leukemia/Lymphoma

PubMed Central

Hasui, Kazuhisa; Wang, Jia; Tanaka, Yuetsu; Izumo, Shuji; Eizuru, Yoshito; Matsuyama, Takami

2012-01-01

Antigen retrieval (AR) and ultra-super sensitive immunohistochemistry (ultra-IHC) have been established for application to archival human pathology specimens. The original ultra-IHC was the ImmunoMax method or the catalyzed signal amplification system (ImmunoMax/CSA method), comprising the streptavidin-biotin complex (sABC) method and catalyzed reporter deposition (CARD) reaction with visualization of its deposition. By introducing procedures to diminish non-specific staining in the original ultra-IHC method, we developed the modified ImmunoMax/CSA method with AR heating sections in an AR solution (heating-AR). The heating-AR and modified ImmunoMax/CSA method visualized expression of the predominantly simple present form of HTLV-1 proviral DNA pX region p40Tax protein (Tax) in adult T-cell leukemia/lymphoma (ATLL) cells in archival pathology specimens in approximately 75% of cases. The simple present form of Tax detected exhibited a close relation with ATLL cell proliferation. We also established a new simplified CSA (nsCSA) system by replacing the sABC method with the secondary antibody- and horse radish peroxidase-labeled polymer reagent method, introducing the pretreatments blocking non-specific binding of secondary antibody reagent, and diminishing the diffusion of deposition in the CARD reaction. Combined with AR treating sections with proteinase K solution (enzymatic-AR), the nsCSA system visualized granular immunostaining of the complex present form of Tax in a small number of ATLL cells in most cases, presenting the possibility of etiological pathological diagnosis of ATLL and suggesting that the complex present form of Tax-positive ATLL cells were young cells derived from ATLL stem cells. The heating-AR and ultra-IHC detected physiological expression of the p53 protein and its probable phosphorylation by Tax in peripheral blood mononuclear cells of peripheral blood tissue specimens from HTLV-1 carriers, as well as physiological and pathological expression of the molecules involved with G1 phase progression and G1–S phase transition (E2F-1, E2F-4, DP-1, and cyclin E) in ATLL and peripheral T-cell lymphoma cells. The ultra-IHC with AR is useful for etiological pathological diagnosis of ATLL since HTLV-1 pathogenicity depends on that of Tax, and can be a useful tool for studies translating advanced molecular biology and pathology to human pathology. PMID:22685351

Catalyst activation, deactivation, and degradation in palladium-mediated Negishi cross-coupling reactions.

PubMed

Böck, Katharina; Feil, Julia E; Karaghiosoff, Konstantin; Koszinowski, Konrad

2015-03-27

Pd-mediated Negishi cross-coupling reactions were studied by a combination of kinetic measurements, electrospray-ionization (ESI) mass spectrometry, (31)P NMR and UV/Vis spectroscopy. The kinetic measurements point to a rate-determining oxidative addition. Surprisingly, this step seems to involve not only the Pd catalyst and the aryl halide substrate, but also the organozinc reagent. In this context, the ESI-mass spectrometric observation of heterobimetallic Pd-Zn complexes [L2 PdZnR](+) (L=S-PHOS, R=Bu, Ph, Bn) is particularly revealing. The inferred presence of these and related neutral complexes with a direct Pd-Zn interaction in solution explains how the organozinc reagent can modulate the reactivity of the Pd catalyst. Previous theoretical calculations by González-Pérez et al. (Organometallics- 2012, 31, 2053) suggest that the complexation by the organozinc reagent lowers the activity of the Pd catalyst. Presumably, a similar effect also causes the rate decrease observed upon addition of ZnBr2 . In contrast, added LiBr apparently counteracts the formation of Pd-Zn complexes and restores the high activity of the Pd catalyst. At longer reaction times, deactivation processes due to degradation of the S-PHOS ligand and aggregation of the Pd catalyst come into play, thus further contributing to the appreciable complexity of the title reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction of d(10) metal ions with thioether ligands: a thermodynamic and theoretical study.

PubMed

Melchior, Andrea; Peralta, Elena; Valiente, Manuel; Tavagnacco, Claudio; Endrizzi, Francesco; Tolazzi, Marilena

2013-05-07

Thermodynamic parameters of complex formation between d(10) metal ions, such as Zn(2+), Cd(2+), Hg(2+) and Ag(+), and the macrocyclic thioether 1,4,7-trithiacyclononane ([9]AneS3) or the monodentate diethylsulfide (Et(2)S), in acetonitrile (AN) at 298.15 K, were studied by a systematic methodology including potentiometry, calorimetry and polarography. [9]AneS3 is able to form complexes with all the target cations, Et(2)S only reacts with Hg(2+) and Ag(+). Mononuclear ML(j) (j = 1, 2) complexes are formed with all the metal ions investigated, where the affinity order is Hg(2+) > Ag(+) > Cd(2+) ≈ Zn(2+) when L = [9]AneS3 and Hg(2+) > Ag(+) when L = Et(2)S. Enthalpy and entropy values are generally negative, as a consequence of both metal ion interactions with neutral ligands, the reagents' loss of degrees of freedom and the release of solvating molecules. DFT calculations on the complexes formed with [9]AneS3 in vacuum and in AN are also carried out, to correlate experimental and theoretical thermodynamic values and to highlight the interplay between the direct metal-thioether interaction and the solvation effects. Trends obtained for the stability constants and enthalpies of the 1 : 1 and 1 : 2 complexes in solvent well reproduce the experimental ones for all the divalent metal ion complexes with [9]AneS3 and indicate the release of 3 AN molecules in the formation of each consecutive octahedral complex. In addition, calculated and experimental values for Ag(+) complex formation in solution suggest that in AgL(2) species [9]AneS3 ligands are not both tridentate.

Density functional theory study of the mechanism and origins of stereoselectivity in the asymmetric Simmons-Smith cyclopropanation with Charette chiral dioxaborolane ligand.

PubMed

Wang, Tao; Liang, Yong; Yu, Zhi-Xiang

2011-06-22

Asymmetric Simmons-Smith reaction using Charette chiral dioxaborolane ligand is a widely applied method for the construction of enantiomerically enriched cyclopropanes. The detailed mechanism and the origins of stereoselectivity of this important reaction were investigated using density functional theory (DFT) calculations. Our computational studies suggest that, in the traditional Simmons-Smith reaction conditions, the monomeric iodomethylzinc allyloxide generated in situ from the allylic alcohol and the zinc reagent has a strong tendency to form a dimer or a tetramer. The tetramer can easily undergo an intramolecular cyclopropanation to give the racemic cyclopropane product. However, when a stoichiometric amount of Charette chiral dioxaborolane ligand is employed, monomeric iodomethylzinc allyloxide is converted into an energetically more stable four-coordinated chiral zinc/ligand complex. The chiral complex has the zinc bonded to the CH(2)I group and coordinated by three oxygen atoms (one from the allylic alcohol and the other two oxygen atoms from the carbonyl oxygen and the ether oxygen in the dioxaborolane ligand), and it can undergo the cyclopropanation reaction easily. Three key factors influencing the enantioselectivity have been identified through examining the cyclopropanation transition states: (1) the torsional strain along the forming C-C bond, (2) the 1,3-allylic strain caused by the chain conformation, and (3) the ring strain generated in the transition states. In addition, the origin of the high anti diastereoselectivity for the substituent on the zinc reagent and the hydroxymethyl group of the allylic alcohol has been rationalized through analyzing the steric repulsion and the ring strain in the cyclopropanation transition states.

Enzymatic Reaction with Unnatural Substrates: DNA Photolyase (Escherichia coli) Recognizes and Reverses Thymine [2+2] Dimers in the DNA Strand of a DNA/PNA Hybrid Duplex

NASA Astrophysics Data System (ADS)

Ramaiah, Danaboyina; Kan, Yongzhi; Koch, Troels; Orum, Henrik; Schuster, Gary B.

1998-10-01

Peptide nucleic acids (PNA) are mimics with normal bases connected to a pseudopeptide chain that obey Watson--Crick rules to form stable duplexes with itself and natural nucleic acids. This has focused attention on PNA as therapeutic or diagnostic reagents. Duplexes formed with PNA mirror some but not all properties of DNA. One fascinating aspect of PNA biochemistry is their reaction with enzymes. Here we show an enzyme reaction that operates effectively on a PNA/DNA hybrid duplex. A DNA oligonucleotide containing a cis, syn-thymine [2+2] dimer forms a stable duplex with PNA. The hybrid duplex is recognized by photolyase, and irradiation of the complex leads to the repair of the thymine dimer. This finding provides insight into the enzyme mechanism and provides a means for the selective repair of thymine photodimers.

Solvent extraction: the coordination chemistry behind extractive metallurgy.

PubMed

Wilson, A Matthew; Bailey, Phillip J; Tasker, Peter A; Turkington, Jennifer R; Grant, Richard A; Love, Jason B

2014-01-07

The modes of action of the commercial solvent extractants used in extractive hydrometallurgy are classified according to whether the recovery process involves the transport of metal cations, M(n+), metalate anions, MXx(n-), or metal salts, MXx into a water-immiscible solvent. Well-established principles of coordination chemistry provide an explanation for the remarkable strengths and selectivities shown by most of these extractants. Reagents which achieve high selectivity when transporting metal cations or metal salts into a water-immiscible solvent usually operate in the inner coordination sphere of the metal and provide donor atom types or dispositions which favour the formation of particularly stable neutral complexes that have high solubility in the hydrocarbons commonly used in recovery processes. In the extraction of metalates, the structures of the neutral assemblies formed in the water-immiscible phase are usually not well defined and the cationic reagents can be assumed to operate in the outer coordination spheres. The formation of secondary bonds in the outer sphere using, for example, electrostatic or H-bonding interactions are favoured by the low polarity of the water-immiscible solvents.

21 CFR 184.1245 - Beta-carotene.

Code of Federal Regulations, 2014 CFR

2014-04-01

... synthesized by saponification of vitamin A acetate. The resulting alcohol is either reacted to form vitamin A Wittig reagent or oxidized to vitamin A aldehyde. Vitamin A Wittig reagent and vitamin A aldehyde are..._regulations/ibr_locations.html. (c) In accordance with § 184.1(b)(1), the ingredient is used in food with no...

Solid-water detoxifying reagents for chemical and biological agents

DOEpatents

Hoffman, Dennis M [Livermore, CA; Chiu, Ing Lap [Castro Valley, CA

2006-04-18

Formation of solid-water detoxifying reagents for chemical and biological agents. Solutions of detoxifying reagent for chemical and biological agents are coated using small quantities of hydrophobic nanoparticles by vigorous agitation or by aerosolization of the solution in the presence of the hydrophobic nanoparticles to form a solid powder. For example, when hydrophobic fumed silica particles are shaken in the presence of IN oxone solution in approximately a 95:5-weight ratio, a dry powder results. The hydrophobic silica forms a porous coating of insoluble fine particles around the solution. Since the chemical or biological agent tends to be hydrophobic on contact with the weakly encapsulated detoxifying solution, the porous coating breaks down and the detoxifying reagent is delivered directly to the chemical or biological agent for maximum concentration at the point of need. The solid-water (coated) detoxifying solutions can be blown into contaminated ventilation ducting or other difficult to reach sites for detoxification of pools of chemical or biological agent. Once the agent has been detoxified, it can be removed by flushing the area with air or other techniques.

Enantioselective small molecule synthesis by carbon dioxide fixation using a dual Brønsted acid/base organocatalyst.

PubMed

Vara, Brandon A; Struble, Thomas J; Wang, Weiwei; Dobish, Mark C; Johnston, Jeffrey N

2015-06-17

Carbon dioxide exhibits many of the qualities of an ideal reagent: it is nontoxic, plentiful, and inexpensive. Unlike other gaseous reagents, however, it has found limited use in enantioselective synthesis. Moreover, unprecedented is a tool that merges one of the simplest biological approaches to catalysis-Brønsted acid/base activation-with this abundant reagent. We describe a metal-free small molecule catalyst that achieves the three component reaction between a homoallylic alcohol, carbon dioxide, and an electrophilic source of iodine. Cyclic carbonates are formed enantioselectively.

Automated high-throughput flow-through real-time diagnostic system

DOEpatents

Regan, John Frederick

2012-10-30

An automated real-time flow-through system capable of processing multiple samples in an asynchronous, simultaneous, and parallel fashion for nucleic acid extraction and purification, followed by assay assembly, genetic amplification, multiplex detection, analysis, and decontamination. The system is able to hold and access an unlimited number of fluorescent reagents that may be used to screen samples for the presence of specific sequences. The apparatus works by associating extracted and purified sample with a series of reagent plugs that have been formed in a flow channel and delivered to a flow-through real-time amplification detector that has a multiplicity of optical windows, to which the sample-reagent plugs are placed in an operative position. The diagnostic apparatus includes sample multi-position valves, a master sample multi-position valve, a master reagent multi-position valve, reagent multi-position valves, and an optical amplification/detection system.

Application of 2-Trichloromethylbenzimidazole in Analytical Chemistry: A Highly Selective Chromogenic Reagent for Thin-Layer Chromatography and Some Other Analytical Uses

PubMed Central

Konopski, Leszek; Kiełczewska, Anna

2012-01-01

2-Trichloromethylbenzimidazole (TCMB) was used as a chromogenic reagent in organic or inorganic analysis, mainly in thin-layer chromatography (TLC). In reactions of TCMB with some heteroaromatic nitrogen containing compounds, such as azines, azoles and benzazoles, a formation of high colored products occurred. For azines, the chromogenic reaction was highly regioselective, since the both adjacent α-positions versus the nitrogen atom(s) must not be substituted. A TLC method of detection was developed. Thirty azines, azoles, and benzazoles were detected at the detection limit 10 ng to 1 μg. This method was also applied for detection of heteroaromatic pesticides, and the attempts to construct active and passive dosimeters for nicotine were made. In a prechromatographic reaction of aromatic o-diamines with methyl trichloroacetimidate, TCMB or its derivatives were formed in situ. Followed by TLC and visualization in pyridine vapors, this procedure was applied for detection of o-phenylenediamine derivatives. The reaction product of TCMB and pyridine (LI Complex) was identified and fully characterized. Two different reaction mechanisms: with electron deficient basic heteroaromatic compounds, like pyridine, and with more acidic compounds, for example, pyrrole, were discussed. In aqueous solutions, the LI Complex may be also used as a new indicator for complexometric, adsorption and acid-base titration of inorganic compounds. PMID:22567563

Quenching methods for background reduction in luminescence-based probe-target binding assays

DOEpatents

Cai, Hong [Los Alamos, NM; Goodwin, Peter M [Los Alamos, NM; Keller, Richard A [Los Alamos, NM; Nolan, Rhiannon L [Santa Fe, NM

2007-04-10

Background luminescence is reduced from a solution containing unbound luminescent probes, each having a first molecule that attaches to a target molecule and having an attached luminescent moiety, and luminescent probe/target adducts. Quenching capture reagent molecules are formed that are capable of forming an adduct with the unbound luminescent probes and having an attached quencher material effective to quench luminescence of the luminescent moiety. The quencher material of the capture reagent molecules is added to a solution of the luminescent probe/target adducts and binds in a proximity to the luminescent moiety of the unbound luminescent probes to quench luminescence from the luminescent moiety when the luminescent moiety is exposed to exciting illumination. The quencher capture reagent does not bind to probe molecules that are bound to target molecules and the probe/target adduct emission is not quenched.

Method of preparing a high heating value fuel product

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

Somerville, R.; Fan, L.T.

1989-10-24

This patent describes a method of preparing a high heating value fuel product. The method comprising the steps of: blending a high heating value waste material with a cellulosic material; mixing an organic reagent to the blended mixture of the waste material and the cellulosic material, the organic reagent being a mixture having a 4-15 weight percent of a chemical selected from the group consisting of: triethylene, glycol, diethylene glycol, and glycerin propylene glycol; introducing a pozzolanic agent to the blended mixture for controlling the rate of solidification; and forming the blended mixture into a form suitable for handling. Alsomore » described is the same method with the mixture of the organic reagent further comprising: a 20-32 weight percent calcium chloride solution. Another method of preparing a fuel product is also described.« less

Four-coordinate, 14-electron Ru(II) complexes: unusual trigonal pyramidal geometry enforced by bis(phosphino)silyl ligation.

PubMed

MacInnis, Morgan C; McDonald, Robert; Ferguson, Michael J; Tobisch, Sven; Turculet, Laura

2011-08-31

Unprecedented diamagnetic, four-coordinate, formally 14-electron (Cy-PSiP)RuX (Cy-PSiP = [κ(3)-(2-R(2)PC(6)H(4))(2)SiMe](-); X = amido, alkoxo) complexes that do not require agostic stabilization and that adopt a highly unusual trigonal pyramidal coordination geometry are reported. The tertiary silane [(2-Cy(2)PC(6)H(4))(2)SiMe]H ((Cy-PSiP)H) reacted with 0.5 [(p-cymene)RuCl(2)](2) in the presence of Et(3)N and PCy(3) to afford [(Cy-PSiP)RuCl](2) (1) in 74% yield. Treatment of 1 with KO(t)Bu led to the formation of (Cy-PSiP)RuO(t)Bu (2, 97% yield), which was crystallographically characterized and shown to adopt a trigonal pyramidal coordination geometry in the solid state. Treatment of 1 with NaN(SiMe(3))(2) led to the formation of (Cy-PSiP)RuN(SiMe(3))(2) (3, 70% yield), which was also found to adopt a trigonal pyramidal coordination geometry in the solid state. The related anilido complexes (Cy-PSiP)RuNH(2,6-R(2)C(6)H(3)) (4, R = H; 5, R = Me) were also prepared in >90% yields by treating 1 with LiNH(2,6-R(2)C(6)H(3)) (R = H, Me) reagents. The solid state structure of 5 indicates a monomeric trigonal pyramidal complex that features a C-H agostic interaction. Complexes 2 and 3 were found to react readily with 1 equiv of H(2)O to form the dimeric hydroxo-bridged complex [(Cy-PSiP)RuOH](2) (6, 94% yield), which was crystallographically characterized. Complexes 2 and 3 also reacted with 1 equiv of PhOH to form the new 18-electron η(5)-oxocyclohexadienyl complex (Cy-PSiP)Ru(η(5)-C(6)H(5)O) (7, 84% yield). Both amido and alkoxo (Cy-PSiP)RuX complexes reacted with H(3)B·NHRR' reagents to form bis(σ-B-H) complexes of the type (Cy-PSiP)RuH(η(2):η(2)-H(2)BNRR') (8, R = R' = H; 9, R = R' = Me; 10, R = H, R' = (t)Bu), which illustrates that such four-coordinate (Cy-PSiP)RuX (X = amido, alkoxo) complexes are able to undergo multiple E-H (E = main group element) bond activation steps. Computational methods were used to investigate structurally related PCP, PPP, PNP, and PSiP four-coordinate Ru complexes and confirmed the key role of the strongly σ-donating silyl group of the PSiP ligand set in enforcing the unusual trigonal pyramidal coordination geometry featured in complexes 2-5, thus substantiating a new strategy for the synthesis of low-coordinate Ru species. The mechanism of the activation of ammonia-borane by such low-coordinate (R-PSiP)RuX (X = amido, alkoxo) species was also studied computationally and was determined to proceed most likely in a stepwise fashion via intramolecular deprotonation of ammonia and subsequent borane B-H bond oxidative addition steps.

Evaluation of novel derivatisation reagents for the analysis of oxysterols

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

Crick, Peter J., E-mail: p.j.crick@swansea.ac.uk; Aponte, Jennifer; Bentley, T. William

2014-04-11

Graphical abstract: - Highlights: • New derivatisation reagents for LC–MS analysis of oxysterols. • New reagents based on Girard P give high ion-currents and informative LC–MS{sup n} spectra. • Permanent charge is vital for efficient MS{sup n} fragmentation. • New reagents offer greater scope for incorporation of isotope labels. - Abstract: Oxysterols are oxidised forms of cholesterol that are intermediates in the synthesis of bile acids and steroid hormones. They are also ligands to nuclear and G protein-coupled receptors. Analysis of oxysterols in biological systems is challenging due to their low abundance coupled with their lack of a strong chromophoremore » and poor ionisation characteristics in mass spectrometry (MS). We have previously used enzyme-assisted derivatisation for sterol analysis (EADSA) to identify and quantitate oxysterols in biological samples. This technique relies on tagging sterols with the Girard P reagent to introduce a charged quaternary ammonium group. Here, we have compared several modified Girard-like reagents and show that the permanent charge is vital for efficient MS{sup n} fragmentation. However, we find that the reagent can be extended to include sites for potential stable isotope labels without a loss of performance.« less

The radiation chemistry of nuclear reactor decontaminating reagents

NASA Astrophysics Data System (ADS)

Sellers, Robin M.

Processes involved in the radiation chemistry of some typical nuclear reactor decontaminating reagents including complexing, reducing and oxidising agents are described. It is concluded that radiation-induced decomposition is only likely to be a problem with dilute formulations, and/or with minor additives such as corrosion inhibitors which are not protected from attack by the other constituents. Addition of a "sacrificial" compound may be necessary to overcome this. The importance of considering loss of function, rather than the decomposition rate of the starting material, is emphasised. Reagents based on low oxidation state metal ions (LOMI) can be regenerated by the radiation field in the presence of formate ion.

Reduction of C Bonds Proceeds with Retention of Configuration: Stereochemical Investigation of the Heterogeneous Reduction by Dideuterium of (Homohypostrophene)Neopentyl(2-Norbornyl)Platinum(II) Complexes on Platinum Black.

DTIC Science & Technology

1991-04-23

ClIH16: C, 89.12; H, 10.88; Found: C, 88.85; H, 10.90. Synthesis of Grignard Reagents . Neopentylmagnesium chloride. Into a 500-mL round-bottomed flask... Grignard reagent several times using the following procedure. We placed 5.0 g (0.206 mol) of magnesium chips and a magnetic stir bar to a 200-mL round...Norbornylmagnesium bromide. This Grignard reagent was synthesized using a variation on established procedures. 58,60 We transferred under argon 50.0 mL (30.0 mmol

Production of high specific activity silicon-32

DOEpatents

Phillips, Dennis R.; Brzezinski, Mark A.

1994-01-01

A process for preparation of silicon-32 is provide and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution to from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidization state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.

High specific activity silicon-32

DOEpatents

Phillips, Dennis R.; Brzezinski, Mark A.

1996-01-01

A process for preparation of silicon-32 is provided and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution to from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidization state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.

High specific activity silicon-32

DOEpatents

Phillips, D.R.; Brzezinski, M.A.

1996-06-11

A process for preparation of silicon-32 is provided and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidation state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.

Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K

NASA Astrophysics Data System (ADS)

Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

2013-08-01

The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

Methods for synthesis of semiconductor nanocrystals and thermoelectric compositions

DOEpatents

Ren, Zhifeng [Newton, MA; Chen, Gang [Carlisle, MA; Poudel, Bed [Watertown, MA; Kumar, Shankar [Watertown, MA; Wang, Wenzhong [Newton, MA; Dresselhaus, Mildred [Arlington, MA

2007-08-14

The present invention provides methods for synthesis of IV VI nanostructures, and thermoelectric compositions formed of such structures. In one aspect, the method includes forming a solution of a Group IV reagent, a Group VI reagent and a surfactant. A reducing agent can be added to the solution, and the resultant solution can be maintained at an elevated temperature, e.g., in a range of about 20.degree. C. to about 360.degree. C., for a duration sufficient for generating nanoparticles as binary alloys of the IV VI elements.

Methods for synthesis of semiconductor nanocrystals and thermoelectric compositions

NASA Technical Reports Server (NTRS)

Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Dresselhaus, Mildred (Inventor); Ren, Zhifeng (Inventor); Wang, Wenzhong (Inventor)

2007-01-01

The present invention provides methods for synthesis of IV VI nanostructures, and thermoelectric compositions formed of such structures. In one aspect, the method includes forming a solution of a Group IV reagent, a Group VI reagent and a surfactant. A reducing agent can be added to the solution, and the resultant solution can be maintained at an elevated temperature, e.g., in a range of about 20.degree. C. to about 360.degree. C., for a duration sufficient for generating nanoparticles as binary alloys of the IV VI elements.

Low temperature solution synthesis of silicon, germanium and Si-Ge axial heterostructures in nanorod and nanowire form.

PubMed

Flynn, G; Stokes, K; Ryan, K M

2018-05-31

Herein, we report the formation of silicon, germanium and more complex Si-SixGe1-x and Si-Ge axial 1D heterostructures, at low temperatures in solution. These nanorods/nanowires are grown using phenylated compounds of silicon and germanium as reagents, with precursor decomposition achieved at substantially reduced temperatures (200 °C for single crystal nanostructures and 300 °C for heterostructures), through the addition of a reducing agent. This low energy route for the production of these functional nanostructures as a wet chemical in high yield is attractive to meet the processing needs for next generation photovoltaics, batteries and electronics.

Spectrophotometric determination of uric acid and some redeterminations of its solubility

USGS Publications Warehouse

Norton, D.R.; Plunkett, M.A.; Richards, F.A.

1954-01-01

The present study was initiated in order to develop a rapid and accurate method for the determination of uric acid in fresh, brackish, and sea water. It was found that the spectrophotometric determination of uric acid based upon its reaction with arsenophosphotungstic acid reagent in the presence of cyanide ion meets this objective. The absorbancy of the blue complex was measured at 890 m??. Slight variations from Beer's law were generally found. The results show the effects of pH, reaction time, concentration of reagents, and temperature upon color development and precipitate formation. Disodium dihydrogen ethylenediamine tetraacetate (Versene) was used as a buffering and complexirig agent. The results are significant in that they give the absorption spectrum of the blue complex and the effects of variables upon its absorbancy. Studies were made with the method to determine the stability of reagents and standard solutions and to determine the rate of bacterial decomposition of uric acid. Measurements of the solubility of uric acid are reported.

Evaluation of the Efficiency of the Sample Inactivation Reagent in the Abbott RealTime MTB Assay for Inactivation of Mycobacterium tuberculosis

PubMed Central

Wallis, Carole; Pahalawatta, Vihanga; Frank, Andrea; Ramdin, Neeshan; Viana, Raquel; Abravaya, Klara; Leckie, Gregor; Tang, Ning

2015-01-01

The Abbott RealTime MTB assay is a nucleic acid amplification test (NAAT) for the detection of Mycobacterium tuberculosis complex DNA. The sample inactivation procedure used in the assay, consisting of one part sample treated with 3 parts inactivation reagent for 60 min, effectively reduced viscosity and inactivated M. tuberculosis in clinical specimens. PMID:26085611

New Advanced Oxidation Technologies for Destruction of Pollutants in Water

DTIC Science & Technology

2001-09-01

biological desinfection of water from the secondary toxic substances after the plasmachemical treatment. The pulse UV treatment is applied for the...lowered pressure (10 - 30 torr), the burning of the auxiliary independent discharge above a surface of a solution did not influence on vital functions...sulfophthtalein reagent and for adsorption on the silica gel surface . But the radical fragments of surfactant molecules are complexing with the reagent and

The structure and protein binding of amyloid-specific dye reagents.

PubMed

Stopa, Barbara; Piekarska, Barbara; Konieczny, Leszek; Rybarska, Janina; Spólnik, Paweł; Zemanek, Grzegorz; Roterman, Irena; Król, Marcin

2003-01-01

The self-assembling tendency and protein complexation capability of dyes related to Congo red and also some dyes of different structure were compared to explain the mechanism of Congo red binding and the reason for its specific affinity for beta-structure. Complexation with proteins was measured directly and expressed as the number of dye molecules bound to heat-aggregated IgG and to two light chains with different structural stability. Binding of dyes to rabbit antibodies was measured indirectly as the enhancement effect of the dye on immune complex formation. Self-assembling was tested using dynamic light scattering to measure the size of the supramolecular assemblies. In general the results show that the supramolecular form of a dye is the main factor determining its complexation capability. Dyes that in their compact supramolecular organization are ribbon-shaped may adhere to polypeptides of beta-conformation due to the architectural compatibility in this unique structural form. The optimal fit in complexation seems to depend on two contradictory factors involving, on the one hand, the compactness of the non-covalently stabilized supramolecular ligand, and the dynamic character producing its plasticity on the other. As a result, the highest protein binding capability is shown by dyes with a moderate self-assembling tendency, while those arranging into either very rigid or very unstable supramolecular entities are less able to bind.

Design and implementation of bimolecular fluorescence complementation (BiFC) assays for the visualization of protein interactions in living cells.

PubMed

Kerppola, Tom K

2006-01-01

Bimolecular fluorescence complementation (BiFC) analysis enables direct visualization of protein interactions in living cells. The BiFC assay is based on the discoveries that two non-fluorescent fragments of a fluorescent protein can form a fluorescent complex and that the association of the fragments can be facilitated when they are fused to two proteins that interact with each other. BiFC must be confirmed by parallel analysis of proteins in which the interaction interface has been mutated. It is not necessary for the interaction partners to juxtapose the fragments within a specific distance of each other because they can associate when they are tethered to a complex with flexible linkers. It is also not necessary for the interaction partners to form a complex with a long half-life or a high occupancy since the fragments can associate in a transient complex and un-associated fusion proteins do not interfere with detection of the complex. Many interactions can be visualized when the fusion proteins are expressed at levels comparable to their endogenous counterparts. The BiFC assay has been used for the visualization of interactions between many types of proteins in different subcellular locations and in different cell types and organisms. It is technically straightforward and can be performed using a regular fluorescence microscope and standard molecular biology and cell culture reagents.

Nitrous Oxide-dependent Iron-catalyzed Coupling Reactions of Grignard Reagents.

PubMed

Döhlert, Peter; Weidauer, Maik; Enthaler, Stephan

2015-01-01

The formation of carbon-carbon bonds is one of the fundamental transformations in chemistry. In this regard the application of palladium-based catalysts has been extensively investigated during recent years, but nowadays research focuses on iron catalysis, due to sustainability, costs and toxicity issues; hence numerous examples for iron-catalyzed cross-coupling reactions have been established, based on the coupling of electrophiles (R(1)-X, X = halide) with nucleophiles (R(2)-MgX). Only a small number of protocols deals with the iron-catalyzed oxidative coupling of nucleophiles (R(1)-MgX + R(2)-MgX) with the aid of oxidants (1,2-dihaloethanes). However, some issues arise with these oxidants; hence more recently the potential of the industrial waste product nitrous oxide (N(2)O) was investigated, because the unproblematic side product N(2) is formed. Based on that, we demonstrate the catalytic potential of easily accessible iron complexes in the oxidative coupling of Grignard reagents. Importantly, nitrous oxide was essential to obtain yields up to >99% at mild conditions (e.g. 1 atm, ambient temperature) and low catalyst loadings (0.1 mol%) Excellent catalyst performance is realized with turnover numbers of up to 1000 and turnover frequencies of up to 12000 h(-1). Moreover, a good functional group tolerance is observed (e.g. amide, ester, nitrile, alkene, alkyne). Afterwards the reaction of different Grignard reagents revealed interesting results with respect to the selectivity of cross-coupling product formation.

Slow Off-Rate Modified Aptamer (SOMAmer) as a Novel Reagent in Immunoassay Development for Accurate Soluble Glypican-3 Quantification in Clinical Samples.

PubMed

Duo, Jia; Chiriac, Camelia; Huang, Richard Y-C; Mehl, John; Chen, Guodong; Tymiak, Adrienne; Sabbatini, Peter; Pillutla, Renuka; Zhang, Yan

2018-04-17

Accurate quantification of soluble glypican-3 in clinical samples using immunoassays is challenging, because of the lack of appropriate antibody reagents to provide a full spectrum measurement of all potential soluble glypican-3 fragments in vivo. Glypican-3 SOMAmer (slow off-rate modified aptamer) is a novel reagent that binds, with high affinity, to a far distinct epitope of glypican-3, when compared to all available antibody reagents generated in-house. This paper describes an integrated analytical approach to rational selection of key reagents based on molecular characterization by epitope mapping, with the focus on our work using a SOMAmer as a new reagent to address development challenges with traditional antibody reagents for the soluble glypican-3 immunoassay. A qualified SOMAmer-based assay was developed and used for soluble glypican-3 quantification in hepatocellular carcinoma (HCC) patient samples. The assay demonstrated good sensitivity, accuracy, and precision. Data correlated with those obtained using the traditional antibody-based assay were used to confirm the clinically relevant soluble glypican-3 forms in vivo. This result was reinforced by a liquid chromatography tandem mass spectrometry (LC-MS/MS) assay quantifying signature peptides generated from trypsin digestion. The work presented here offers an integrated strategy for qualifying aptamers as an alternative affinity platform for immunoassay reagents that can enable speedy assay development, especially when traditional antibody reagents cannot meet assay requirements.

CONTINUOUS GAS ANALYZER

DOEpatents

Katz, S.; Weber, C.W.

1960-02-16

A reagent gas and a sample gas are chemically combined on a continuous basis in a reaction zone maintained at a selected temperature. The reagent gas and the sample gas are introduced to the reaction zone at preselected. constant molar rates of flow. The reagent gas and the selected gas in the sample mixture combine in the reaction zone to form a product gas having a different number of moles from the sum of the moles of the reactants. The difference in the total molar rates of flow into and out of the reaction zone is measured and indicated to determine the concentration of the selected gas.

NMR Spectroscopy Using a Chiral Lanthanide Shift Reagent to Assess the Optical Purity of 1-Phenylethylamine

NASA Astrophysics Data System (ADS)

Viswanathan, Tito; Toland, Alan

1995-10-01

Enantiomeric forms of 1-phenylethylamine cannot be distinguished by 1H or 13C-NMR because the groups attached to the stereocenter are in an enantiopic environment. However, the chemical shifts of the protons in the groups attached to the stereocenter can be differentially altered to appear as distinct peaks in the NMR spectrum. This is accomplished by the use of a commercially available chiral lanthanide shift reagent, Yb(tfC)3. The NMR spectrum after the addition of a chiral shift reagent allows one to assess the optical purity of the sample.

Iron-catalyzed oxidative biaryl cross-couplings via mixed diaryl titanates: significant influence of the order of combining aryl Grignard reagents with titanate.

PubMed

Liu, Kun Ming; Wei, Juan; Duan, Xin Fang

2015-03-18

The mixed diaryl titanates were used for the first time to modify the reactivity of two aryl Grignard reagents. Two titanate intermediates, Ar[Ar'Ti(OR)3]MgX and Ar'[ArTi(OR)3]MgX, formed via alternating the sequence of combining Grignard reagents with ClTi(OR)3 showed a significant reactivity difference. Taking advantage of such different reactivity, two highly structurally similar aryl groups could be facilely assembled through iron-catalyzed oxidative cross-couplings using oxygen as the oxidant.

Catalytic Carbonyl Allylation, Propargylation and Vinylation from the Alcohol or Aldehyde Oxidation Level via C-C Bond Forming Hydrogenation and Transfer Hydrogenation: A Departure from Preformed Organometallic Reagents**

PubMed Central

Bower, John F.; Kim, In Su; Patman, Ryan L.; Krische, Michael J.

2009-01-01

Classical protocols for carbonyl allylation, propargylation and vinylation typically rely upon the use of preformed allyl metal, allenyl metal and vinyl metal reagents, respectively, mandating stoichiometric generation of metallic byproducts. Through transfer hydrogenative C-C coupling, carbonyl addition may be achieved from the aldehyde or alcohol oxidation level in the absence of stoichiometric organometallic reagents or metallic reductants. Here, we review transfer hydrogenative methods for carbonyl addition, which encompass the first cataltyic protocols enabling direct C–H functionalization of alcohols. PMID:19040235

Mapping of contact sites in complex formation between light-activated rhodopsin and transducin by covalent crosslinking: Use of a chemically preactivated reagent

PubMed Central

Itoh, Yoshiki; Cai, Kewen; Khorana, H. Gobind

2001-01-01

Contact sites in interaction between light-activated rhodopsin and transducin (T) have been investigated by using a chemically preactivated crosslinking reagent, N-succinimidyl 3-(2-pyridyldithio)propionate. The 3 propionyl-N-succinimidyl group in the reagent was attached by a disulfide exchange reaction to rhodopsin mutants containing single reactive cysteine groups in the cytoplasmic loops. Complex formation between the derivatized rhodopsin mutants and T was carried out by illumination at λ > 495 nm. Subsequent increase in pH (from 6 to 7.5 or higher) of the complex resulted in crosslinking of rhodopsin to the Tα subunit. Crosslinking to Tα was demonstrated for the rhodopsin mutants K141C, S240C, and K248C, and the crosslinked sites in Tα were identified for the rhodopsin mutant S240C. The peptides carrying the crosslinking moiety were isolated from the trypsin-digested peptide mixture, and their identification was carried out by matrix-assisted laser desorption ionization–time of flight mass spectrometry. The main site of crosslinking is within the peptide sequence, Leu-19–Arg-28 at the N-terminal region of Tα. The total results show that both the N and the C termini of Tα are in close vicinity to the third cytoplasmic loop of rhodopsin in the complex between rhodopsin and T. PMID:11320238

Lithium purification technique

DOEpatents

Keough, Robert F.; Meadows, George E.

1985-01-01

A method for purifying liquid lithium to remove unwanted quantities of nitrogen or aluminum. The method involves precipitation of aluminum nitride by adding a reagent to the liquid lithium. The reagent will be either nitrogen or aluminum in a quantity adequate to react with the unwanted quantity of the impurity to form insoluble aluminum nitride. The aluminum nitride can be mechanically separated from the molten liquid lithium.

Lithium purification technique

DOEpatents

Keough, R.F.; Meadows, G.E.

1984-01-10

A method for purifying liquid lithium to remove unwanted quantities of nitrogen or aluminum. The method involves precipitation of aluminum nitride by adding a reagent to the liquid lithium. The reagent will be either nitrogen or aluminum in a quantity adequate to react with the unwanted quantity of the impurity to form insoluble aluminum nitride. The aluminum nitride can be mechanically separated from the molten liquid lithium.

Kinetic Study on the Removal of Iron from Gold Mine Tailings by Citric Acid

NASA Astrophysics Data System (ADS)

Mashifana, T.; Mavimbela, N.; Sithole, N.

2018-03-01

The Gold mining generates large volumes of tailings, with consequent disposal and environmental problems. Iron tends to react with sulphur to form pyrite and pyrrhotite which then react with rain water forming acid rain. The study focuses on the removal of iron (Fe) from Gold Mine tailings; Fe was leached using citric acid as a leaching reagent. Three parameters which have an effect on the removal of Fe from the gold mine tailings, namely; temperature (25 °C and 50 °C), reagent concentration (0.25 M, 0.5 M, 0.75 M and 1 M) and solid loading ratio (20 %, 30 % and 40 %) were investigated. It was found that the recovery of Fe from gold mine tailings increased with increasing temperature and reagent concentration, but decreased with increasing solid loading ratio. The optimum conditions for the recovery of Fe from gold mine tailings was found to be at a temperature of 50 ºC, reagent concentration of 1 M and solid loading of 20 %. Three linear kinetic models were investigated and Prout-Tompkins kinetic model was the best fit yielding linear graphs with the highest R2 values.

Preparation and Use of Alkali Metals (Li and Na) in Alumina and Silica Gel as Reagents in Organic Syntheses

NASA Astrophysics Data System (ADS)

Jalloh, Fatmata

This work describes the development of alkali metals (Li and Na) encapsulated in silica and alumina gel (SG and AG), and their applications in organic syntheses. The methods elucidated involved the thermal incorporation of these metals into the pores of SG and AG, serving as solid-state reagents. The encapsulation method/approach addresses the problems associated with the high reactivity of these metals that limit their synthetic utility in research laboratories, pharmaceutical, and manufacturing industries. These problems include their sensitivity to air and moisture, pyrophoricity, difficulty in handling, non-commercial availability, and instability of some of the organoalkali metals reagents. Herein, we describe the developments to synthesize alkali metal precursor (Li-AG) in solid form that offer safer organolithium reagents. This precursor reduces or eliminates the danger associated with the traditional handling of organolithium reagents stored in flammable organic solvents. The use of Li-AG to prepare and deliver organolithium reagents from organic halides and ethers, as needed especially for those that are commercially not available is put forward. In addition, exploration of additional applications of Na-SG and Na-AG reagents in the demethoxylation of Weinreb amides to secondary amines, and Bouveault-Blanc type reduction of amides to amines are described.

Storable Arylpalladium(II) Reagents for Alkene Labeling in Aqueous Media

PubMed Central

Simmons, Rebecca L.; Yu, Robert T.; Myers, Andrew G.

2011-01-01

We show that arylpalladium(II) reagents linked to biotin and indocyanine dye residues can be prepared by decarboxylative palladation of appropriately substituted electron-rich benzoic acid derivatives. When prepared under the conditions described, these organometallic intermediates are tolerant of air and water, can be stored for several months in solution in dimethylsulfoxide, and permit biotin- and indocyanine dye-labeling of functionally complex olefinic substrates in water by Heck-type coupling reactions. PMID:21888420

[Pd(μ-Cl)Cl(IPr*)]2: a highly hindered pre-catalyst for the synthesis of tetra-ortho-substituted biaryls via Grignard reagent cross-coupling.

PubMed

Lesieur, Mathieu; Slawin, Alexandra M Z; Cazin, Catherine S J

2014-08-14

The new well-defined catalyst [Pd(μ-Cl)Cl(IPr*)]2 enables the efficient Grignard reagent cross-coupling for the synthesis of tetra-ortho-substituted biaryls. The high reactivity of the complex is associated with the important bulkiness of the IPr* ligand. The dimer represents the most efficient catalyst reported to date for this challenging transformation.

Coordination chemistry of 6-thioguanine derivatives with cobalt: toward formation of electrical conductive one-dimensional coordination polymers.

PubMed

Amo-Ochoa, Pilar; Alexandre, Simone S; Hribesh, Samira; Galindo, Miguel A; Castillo, Oscar; Gómez-García, Carlos J; Pike, Andrew R; Soler, José M; Houlton, Andrew; Zamora, Félix; Harrington, Ross W; Clegg, William

2013-05-06

In this work we have synthetized and characterized by X-ray diffraction five cobalt complexes with 6-thioguanine (6-ThioGH), 6-thioguanosine (6-ThioGuoH), or 2'-deoxy-6-thioguanosine (2'-d-6-ThioGuoH) ligands. In all cases, these ligands coordinate to cobalt via N7 and S6 forming a chelate ring. However, independently of reagents ratio, 6-ThioGH provided monodimensional cobalt(II) coordination polymers, in which the 6-ThioG(-) acts as bridging ligand. However, for 2'-d-6-ThioGuoH and 6-ThioGuoH, the structure directing effect of the sugar residue gives rise to mononuclear cobalt complexes which form extensive H-bond interactions to generate 3D supramolecular networks. Furthermore, with 2'-d-6-ThioGuoH the cobalt ion remains in the divalent state, whereas with 6-ThioGuoH oxidation occurs and Co(III) is found. The electrical and magnetic properties of the coordination polymers isolated have been studied and the results discussed with the aid of DFT calculations, in the context of molecular wires.

Modulation of neuronal and recombinant GABAA receptors by redox reagents

PubMed Central

Amato, Alessandra; Connolly, Christopher N; Moss, Stephen J; Smart, Trevor G

1999-01-01

The functional role played by the postulated disulphide bridge in γ-aminobutyric acid type A (GABAA) receptors and its susceptibility to oxidation and reduction were studied using recombinant (murine receptor subunits expressed in human embryonic kidney cells) and rat neuronal GABAA receptors in conjunction with whole-cell and single channel patch-clamp techniques. The reducing agent dithiothreitol (DTT) reversibly potentiated GABA-activated responses (IGABA) of α1β1 or α1β2 receptors while the oxidizing reagent 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB) caused inhibition. Redox modulation of IGABA was independent of GABA concentration, membrane potential and the receptor agonist and did not affect the GABA EC50 or Hill coefficient. The endogenous antioxidant reduced glutathione (GSH) also potentiated IGABA in α1β2 receptors, while both the oxidized form of DTT and glutathione (GSSG) caused small inhibitory effects. Recombinant receptors composed of α1β1γ2S or α1β2γ2S were considerably less sensitive to DTT and DTNB. For neuronal GABAA receptors, IGABA was enhanced by flurazepam and relatively unaffected by redox reagents. However, in cultured sympathetic neurones, nicotinic acetylcholine-activated responses were inhibited by DTT whilst in cerebellar granule neurones, NMDA-activated currents were potentiated by DTT and inhibited by DTNB. Single GABA-activated ion channel currents exhibited a conductance of 16 pS for α1β1 constructs. DTT did not affect the conductance or individual open time constants determined from dwell time histograms, but increased the mean open time by affecting the channel open probability without increasing the number of cell surface receptors. A kinetic model of the effects of DTT and DTNB suggested that the receptor existed in equilibrium between oxidized and reduced forms. DTT increased the rate of entry into reduced receptor forms and also into desensitized states. DTNB reversed these kinetic effects. Our results indicate that GABAA receptors formed by α and β subunits are susceptible to regulation by redox agents. Inclusion of the γ2 subunit in the receptor, or recording from some neuronal GABAA receptors, resulted in reduced sensitivity to DTT and DTNB. Given the suggested existence of αβ subunit complexes in some areas of the central nervous system together with the generation and release of endogenous redox compounds, native GABAA receptors may be subject to regulation by redox mechanisms. PMID:10226147

IgG Fab Fragments Forming Bivalent Complexes by a Conformational Mechanism That Is Reversible by Osmolytes*

PubMed Central

Nelson, Alfreda D.; Hoffmann, Michele M.; Parks, Christopher A.; Dasari, Surendra; Schrum, Adam G.; Gil, Diana

2012-01-01

Generated by proteolytic cleavage of immunoglobulin, Fab fragments possess great promise as blocking reagents, able to bind receptors or other targets without inducing cross-linking. However, aggregation of Fab preparations is a common occurrence, which generates intrinsic stimulatory capacity and thwarts signal blockade strategies. Using a panel of biochemical approaches, including size exclusion chromatography, SDS-PAGE, mass spectrometry, and cell stimulation followed by flow cytometry, we have measured the oligomerization and acquisition of stimulatory capacity that occurs in four monoclonal IgG Fabs specific for TCR/CD3. Unexpectedly, we observed that all Fabs spontaneously formed complexes that were precisely bivalent, and these bivalent complexes possessed most of the stimulatory activity of each Fab preparation. Fabs composing bivalent complexes were more susceptible to proteolysis than monovalent Fabs, indicating a difference in conformation between the Fabs involved in these two different states of valency. Because osmolytes represent a class of compounds that stabilize protein folding and conformation, we sought to determine the extent to which the amino acid osmolyte l-proline might impact bivalent Fab complexation. We found that l-proline (i) inhibited the adoption of the conformation associated with bivalent complexation, (ii) preserved Fab monovalency, (iii) reversed the conformation of preformed bivalent Fabs to that of monovalent Fabs, and (iv) separated a significant percentage of preformed bivalent complexes into monovalent species. Thus, Fab fragments can adopt a conformation that is compatible with folding or packing of a bivalent complex in a process that can be inhibited by osmolytes. PMID:23109335

Hyperbranched Polycarbosilanes via Nucleophilic Substitution Reactions

NASA Astrophysics Data System (ADS)

Interrante, L.; Shen, Q.

Nucleophilic substitution reactions involving organomagnesium (Grignard) [1] and organolithium reagents have been used extensively for many years to form Si—C bonds (see Reaction Scheme 12.1). However, their use for the construction of hyperbranched polymers whose backbone contains, as a major structural component, silicon—carbon bonds, i.e., polycarbosilanes [2] is relatively more recent. (12.1) begin{array}{l} {{R}}_3 {{SiX + MR'}} to {{R}}_3 {{SiR' + MX}} \\ left({{{R,R' = alkyl}} {{or aryl;}} {{M = Mg(X),}} {{Li,}} {{Na}};{{X = halogen, OR''}}} right) \\ This chapter focuses on the application of such nucleophilic substitution reactions toward the synthesis of hyperbranched polycarbosilanes, with particular emphasis on those preparations that have resulted in relatively well characterized products. These syntheses are organized by the type of ABn monomer unit used (see Section 1.2), where A and B refer to the (C)X and (Si)Xn, respectively, functional ends of the monomer unit and where the nature of the coupling reaction leads to entirely or primarily Si—C bond formation. In most cases, these are “one-pot” reactions that employ monomers that bear halogen or alkoxy groups on the C and Si ends of the unit. Indeed, hyperbranched polycarbosilanes have been described, in general, as “obtained in one synthetic step via a random, one-pot polymerization of multifunctional monomers of AB n type” [2]. Treatment of the ABn monomer with either elemental Mg or an organolithium reagent, ideally (but not always) forms a complexed carbanion (the nucleophile) by reaction with the C-X end of the monomer unit, resulting in an intermediate of the type, (XxM)CSiXn, where M = Mg or Li, X = halogen or alkoxy, and x = 1 (Mg) or 0 (Li). Self-coupling of this reagent via reactions of the type shown in Reaction Scheme 12.1 leads to oligomeric and polymeric products that are connected primarily through Si—C bonds and yield an inorganic MXx by-product.

Study of Highly Selective and Efficient Thiol Derivatization using Selenium Reagents by Mass Spectrometry

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

Xu, Kehua; Zhang, Yun W.; Tang, Bo

2010-08-15

Biological thiols are critical physiological components and their detection often involves derivatization. This paper reports a systemic mass spectrometry (MS) investigation of the cleavage of Se-N bond by thiol to form a new Se-S bond, the new selenium chemistry for thiol labeling. Our data shows that the reaction is highly selective, rapid, reversible and efficient. For instance, among twenty amino acids, only cysteine was found to be reactive with Se-N containing reagents and the reaction takes place in seconds. By adding dithiothreitol (DTT), the newly formed Se-S bond of peptides/proteins can be reduced back to free thiol. The high selectivitymore » and excellent reversibility of the reaction provide potential of using this chemistry for selective identification of thiol compounds or enriching and purifying thiol peptides/proteins. In addition, the derivatized thiol peptides have interesting dissociation behavior, which is tunable using different selenium reagents. For example, by introducing an adjacent nucleophilic group into the selenium reagent in the case of using ebselen, the reaction product of ebselen with glutathione (GSH) is easy to lose the selenium tag upon collision-induced dissociation (CID), which is useful to "fish out" those peptides containing free cysteine residues by precursor ion scan. By contrast, the selenium tag of N-(phenylseleno) phthalimide reagent can be stable and survive in CID process, which would be of value in pinpointing thiol location using a top-down proteomic approach. Also, the high conversion yield of the reaction allows the counting of total number of thiol in proteins. We believe that ebselen or N-(phenylseleno) phthalimide as tagging thiol-protein reagents will have important applications in both qualitative and quantitative analysis of different thiol-proteins derived from living cells by MS method.« less

Evaluation of novel derivatisation reagents for the analysis of oxysterols

PubMed Central

Crick, Peter J.; Aponte, Jennifer; Bentley, T. William; Matthews, Ian; Wang, Yuqin; Griffiths, William J.

2014-01-01

Oxysterols are oxidised forms of cholesterol that are intermediates in the synthesis of bile acids and steroid hormones. They are also ligands to nuclear and G protein-coupled receptors. Analysis of oxysterols in biological systems is challenging due to their low abundance coupled with their lack of a strong chromophore and poor ionisation characteristics in mass spectrometry (MS). We have previously used enzyme-assisted derivatisation for sterol analysis (EADSA) to identify and quantitate oxysterols in biological samples. This technique relies on tagging sterols with the Girard P reagent to introduce a charged quaternary ammonium group. Here, we have compared several modified Girard-like reagents and show that the permanent charge is vital for efficient MSn fragmentation. However, we find that the reagent can be extended to include sites for potential stable isotope labels without a loss of performance. PMID:24525124

Protein-RNA crosslinking in Escherichia coli 30S ribosomal subunits. Identification of a 16S rRNA fragment crosslinked to protein S12 by the use of the chemical crosslinking reagent 1-ethyl-3-dimethyl-aminopropylcarbodiimide.

PubMed Central

Chiaruttini, C; Expert-Bezançon, A; Hayes, D; Ehresmann, B

1982-01-01

1-ethyl-3-dimethyl aminopropylcarbodiimide (EDC) was used to cross-link 30S ribosomal proteins to 16S rRNA within the E. coli 3OS ribosomal subunit. Covalently linked complexes containing 30S proteins and 16S rRNA, isolated by sedimentation of dissociated crosslinked 30S subunits through SDS containing sucrose gradients, were digested with RNase T1, and the resulting oligonucleotide-protein complexes were fractionated on SDS containing polyacrylamide gels. Eluted complexes containing 30S proteins S9 and S12 linked to oligonucleotides were obtained in pure form. Oligonucleotide 5'terminal labelling was successful in the case of S12 containing but not of the S9 containing complex and led to identification of the S12 bound oligonucleotide as CAACUCG which is located at positions 1316-1322 in the 16S rRNA sequence. Protein S12 is crosslinked to the terminal G of this heptanucleotide. Images PMID:6760129

A flow system for the spectrophotometric determination of lead in different types of waters using ion-exchange for pre-concentration and elimination of interferences.

PubMed

Mesquita, Raquel B R; Fernandes, Sílvia M V; Rangel, António O S S

2004-02-06

A flow system for the spectrophotometric determination of lead in natural and waste waters is proposed. The determination is based on the colorimetric reaction between malachite green and iodide, followed by the formation of a ternary complex between those reagents and lead cations. The developed flow system includes a lead pre-concentration step in a column packed with a cationic resin (Chelex 100) operating in a sequential injection mode. To improve the mixture of sample and reagents, a flow injection approach was adopted for the colorimetric determination. This way a hybrid flow system, involving both sequential and flow injection concepts was designed. Another feature of the proposed system is the efficient elimination of major interferent species, such as cadmium and copper. The elimination of cadmium interference is obtained by complexing Cd(2+) with chloride and retaining the formed negatively charged complexes in an anionic resin, AG1 X-8. As for copper, with the presence of both ionic resins as well as the conditions for cadmium elimination, it no longer acts as an interferent. Different ranges of lead concentration (50-300 and 300-1000mugl(-1)) can be determined with minor changes in the controlling software, useful for application to both natural and waste waters. Therefore, a detection limit of 25mugl(-1) was achieved. Repeatability was evaluated from 10 consecutive determinations being the results better than 4%. The recoveries of lead spikes added to the samples ranged from 93 to 102%. The sampling frequency was 17 and 24 determinations per hour, for 50-300 and 300-1000mugl(-1) ranges, respectively.

Evaluation of the Efficiency of the Sample Inactivation Reagent in the Abbott RealTime MTB Assay for Inactivation of Mycobacterium tuberculosis.

PubMed

Qi, Chao; Wallis, Carole; Pahalawatta, Vihanga; Frank, Andrea; Ramdin, Neeshan; Viana, Raquel; Abravaya, Klara; Leckie, Gregor; Tang, Ning

2015-09-01

The Abbott RealTime MTB assay is a nucleic acid amplification test (NAAT) for the detection of Mycobacterium tuberculosis complex DNA. The sample inactivation procedure used in the assay, consisting of one part sample treated with 3 parts inactivation reagent for 60 min, effectively reduced viscosity and inactivated M. tuberculosis in clinical specimens. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Concerted application of LC-MS and ligand binding assays to better understand exposure of a large molecule drug.

PubMed

Xu, Weifeng; Jiang, Hao; Titsch, Craig; Gadkari, Snaehal; Batog, Alicja; Wang, Bonnie; Hippeli, Lauren; Yamamoto, Brent; Chadwick, Kristina; Wheeler, Jennifer; Thompson, Chris; Stahl, James; Willett, Scott; DeSilva, Binodh S; Myler, Heather; Dodge, Robert W; Pillutla, Renuka C

2018-06-20

A ligand-binding assay (LBA) was used to measure exposure of PRM-151, the recombinant form of human pentraxin-2 (PTX-2), a complex pentamer with multiple binding partners. However, the assay showed a lack of dose-dependent exposure in select preclinical species and it could not differentiate the infused PRM-151 from the endogenous PTX-2 in nonhuman primates. Instead of assessing interference from its multiple binding partners, which could be time consuming and laborious, a LC-MS assay avoid of these interference was implemented to measure 'total' drug without the use of immunoaffinity capture reagents. The resultant LC-MS data confirmed the original data and the lack of dose-dependent exposure is now understood to be due to the multiple and diverse targets and functions and resultant complex biodistribution rather than an assay artifact.

Luminescent lanthanide chelates and methods of use

DOEpatents

Selvin, Paul R.; Hearst, John

1997-01-01

The invention provides lanthanide chelates capable of intense luminescence. The celates comprise a lanthanide chelator covalently joined to a coumarin-like or quinolone-like sensitizer. Exemplary sensitzers include 2- or 4-quinolones, 2- or 4-coumarins, or derivatives thereof e.g. carbostyril 124 (7-amino-4-methyl-2-quinolone), coumarin 120 (7-amino-4-methyl-2-coumarin), coumarin 124 (7-amino-4-(trifluoromethyl)-2-coumarin), aminomethyltrimethylpsoralen, etc. The chelates form high affinity complexes with lanthanides, such as terbium or europium, through chelator groups, such as DTPA. The chelates may be coupled to a wide variety of compounds to create specific labels, probes, diagnostic and/or therapeutic reagents, etc. The chelates find particular use in resonance energy transfer between chelate-lanthanide complexes and another luminescent agent, often a fluorescent non-metal based resonance energy acceptor. The methods provide useful information about the structure, conformation, relative location and/or interactions of macromolecules.

A new dual-channel optical signal probe for Cu2+ detection based on morin and boric acid.

PubMed

Wang, Peng; Yuan, Bin Fang; Li, Nian Bing; Luo, Hong Qun

2014-01-01

In this work we utilized the common analytical reagent morin to develop a new a dual-channel, cost-effective, and sensitive method for determination of Cu(2+). It is found that morin is only weakly fluorescent by itself, but forms highly fluorescent complexes with boric acid. Moreover, the fluorescence of complexes of morin with boric acid is quenched linearly by Cu(2+) in a certain concentration range. Under optimum conditions, the fluorescence quenching efficiency was linearly proportional to the concentration of cupric ions in the range of 0.5-25 μM with high sensitivity, and the detection limit for Cu(2+) was 0.38 μM. The linear range was 1-25 μM determined by spectrophotometry, and the detection limit for cupric ions was 0.8 μM. Furthermore, the mechanism of sensitive fluorescence quenching response of morin to Cu(2+) is discussed.

Plant rhamnogalacturonan II complexation of heavy metal cations

DOEpatents

O`Neill, M.A.; Pellerin, P.J.M.; Warrenfeltz, D.; Vidal, S.; Darvill, A.G.; Albersheim, P.

1999-03-02

The present invention provides rhamnogalacturonan-II (RG-II) and relates to its ability to complex specific multivalent heavy metal cations. In the presence of boric acid, RG-II monomers form dimers that are cross-linked by a borate ester. The yield of such borate ester cross-linked dimers of RG-II is enhanced in the presence of specific heavy metal cations. The present invention further relates to the utility of RG-II in assays for the detection of specific heavy metal contamination; as a reagent useful in the removal of specific heavy metal cations contaminating foods and liquids, for example, fish, wines, etc.; as a pharmaceutical composition useful as an antidote in specific heavy metal cation poisoning; as a treatment for the detoxification of specific heavy metal cations from blood and/or tissues; and in a method of remediation of waters and soils contaminated with specific heavy metal cations. 15 figs.

Plant rhamnogalacturonan II complexation of heavy metal cations

DOEpatents

O'Neill, Malcolm A.; Pellerin, Patrice J. M.; Warrenfeltz, Dennis; Vidal, Stephane; Darvill, Alan G.; Albersheim, Peter

1999-01-01

The present invention provides rhamnogalacturonan-II (RG-II) and relates to its ability to complex specific multivalent heavy metal cations. In the presence of boric acid, RG-II monomers form dimers that are cross-linked by a borate ester. The yield of such borate ester cross-linked dimers of RG-II is enhanced in the presence of specific heavy metal cations. The present invention further relates to the utility of RG-II in assays for the detection of specific heavy metal contamination; as a reagent useful in the removal of specific heavy metal cations contaminating foods and liquids, for example, fish, wines, etc.; as a pharmaceutical composition useful as an antidote in specific heavy metal cation poisoning; as a treatment for the detoxification of specific heavy metal cations from blood and/or tissues; and in a method of remediation of waters and soils contaminated with specific heavy metal cations.

Development and validation of reagents and assays for EZH2 peptide and nucleosome high-throughput screens.

PubMed

Diaz, Elsie; Machutta, Carl A; Chen, Stephanie; Jiang, Yong; Nixon, Christopher; Hofmann, Glenn; Key, Danielle; Sweitzer, Sharon; Patel, Mehul; Wu, Zining; Creasy, Caretha L; Kruger, Ryan G; LaFrance, Louis; Verma, Sharad K; Pappalardi, Melissa B; Le, Baochau; Van Aller, Glenn S; McCabe, Michael T; Tummino, Peter J; Pope, Andrew J; Thrall, Sara H; Schwartz, Benjamin; Brandt, Martin

2012-12-01

Histone methyltransferases (HMT) catalyze the methylation of histone tail lysines, resulting in changes in gene transcription. Misregulation of these enzymes has been associated with various forms of cancer, making this target class a potential new area for the development of novel chemotherapeutics. EZH2 is the catalytic component of the polycomb group repressive complex (PRC2), which selectively methylates histone H3 lysine 27 (H3K27). EZH2 is overexpressed in prostate, breast, bladder, brain, and other tumor types and is recognized as a molecular marker for cancer progression and aggressiveness. Several new reagents and assays were developed to aid in the identification of EZH2 inhibitors, and these were used to execute two high-throughput screening campaigns. Activity assays using either an H3K27 peptide or nucleosomes as substrates for methylation are described. The strategy to screen EZH2 with either a surrogate peptide or a natural substrate led to the identification of the same tractable series. Compounds from this series are reversible, are [(3)H]-S-adenosyl-L-methionine competitive, and display biochemical inhibition of H3K27 methylation.

Mapping of contact sites in complex formation between transducin and light-activated rhodopsin by covalent crosslinking: Use of a photoactivatable reagent

PubMed Central

Cai, Kewen; Itoh, Yoshiki; Khorana, H. Gobind

2001-01-01

Interaction of light-activated rhodopsin with transducin (T) is the first event in visual signal transduction. We use covalent crosslinking approaches to map the contact sites in interaction between the two proteins. Here we use a photoactivatable reagent, N-[(2-pyridyldithio)-ethyl], 4-azido salicylamide. The reagent is attached to the SH group of cytoplasmic monocysteine rhodopsin mutants by a disulfide-exchange reaction with the pyridylthio group, and the derivatized rhodopsin then is complexed with T by illumination at λ >495 nm. Subsequent irradiation of the complex at λ310 nm generates covalent crosslinks between the two proteins. Crosslinking was demonstrated between T and a number of single cysteine rhodopsin mutants. However, sites of crosslinks were investigated in detail only between T and the rhodopsin mutant S240C (cytoplasmic loop V-VI). Crosslinking occurred predominantly with Tα. For identification of the sites of crosslinks in Tα, the strategy used involved: (i) derivatization of all of the free cysteines in the crosslinked proteins with N-ethylmaleimide; (ii) reduction of the disulfide bond linking the two proteins and isolation of all of the Tα species carrying the crosslinked moiety with a free SH group; (iii) adduct formation of the latter with the N-maleimide moiety of the reagent, maleimido-butyryl-biocytin, containing a biotinyl group; (iv) trypsin degradation of the resulting Tα derivatives and isolation of Tα peptides carrying maleimido-butyryl-biocytin by avidin-agarose chromatography; and (v) identification of the isolated peptides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. We found that crosslinking occurred mainly to two C-terminal peptides in Tα containing the amino acid sequences 310–313 and 342–345. PMID:11320237

Reaction-based small-molecule fluorescent probes for chemoselective bioimaging

PubMed Central

Chan, Jefferson; Dodani, Sheel C.; Chang, Christopher J.

2014-01-01

The dynamic chemical diversity of elements, ions and molecules that form the basis of life offers both a challenge and an opportunity for study. Small-molecule fluorescent probes can make use of selective, bioorthogonal chemistries to report on specific analytes in cells and in more complex biological specimens. These probes offer powerful reagents to interrogate the physiology and pathology of reactive chemical species in their native environments with minimal perturbation to living systems. This Review presents a survey of tools and tactics for using such probes to detect biologically important chemical analytes. We highlight design criteria for effective chemical tools for use in biological applications as well as gaps for future exploration. PMID:23174976

Asymmetric Radical Cyclopropanation of Alkenes with In Situ-Generated Donor-Substituted Diazo Reagents via Co(II)-Based Metalloradical Catalysis.

PubMed

Wang, Yong; Wen, Xin; Cui, Xin; Wojtas, Lukasz; Zhang, X Peter

2017-01-25

Donor-substituted diazo reagents, generated in situ from sulfonyl hydrazones in the presence of base, can serve as suitable radical precursors for Co(II)-based metalloradical catalysis (MRC). The cobalt(II) complex of D 2 -symmetric chiral porphyrin [Co(3,5-Di t Bu-Xu(2'-Naph)Phyrin)] is an efficient metalloradical catalyst that is capable of activating different N-arylsulfonyl hydrazones for asymmetric radical cyclopropanation of a broad range of alkenes, affording the corresponding cyclopropanes in high yields with effective control of both diastereo- and enantioselectivity. This Co(II)-based metalloradical system represents the first catalytic protocol that can effectively utilize donor-type diazo reagents for asymmetric olefin cyclopropanation.

Quantitation of proteins using a dye-metal-based colorimetric protein assay.

PubMed

Antharavally, Babu S; Mallia, Krishna A; Rangaraj, Priya; Haney, Paul; Bell, Peter A

2009-02-15

We describe a dye-metal (polyhydroxybenzenesulfonephthalein-type dye and a transition metal) complex-based total protein determination method. The binding of the complex to protein causes a shift in the absorption maximum of the dye-metal complex from 450 to 660 nm. The dye-metal complex has a reddish brown color that changes to green on binding to protein. The color produced from this reaction is stable and increases in a proportional manner over a broad range of protein concentrations. The new Pierce 660 nm Protein Assay is very reproducible, rapid, and more linear compared with the Coomassie dye-based Bradford assay. The assay reagent is room temperature stable, and the assay is a simple and convenient mix-and-read format. The assay has a moderate protein-to-protein variation and is compatible with most detergents, reducing agents, and other commonly used reagents. This is an added advantage for researchers needing to determine protein concentrations in samples containing both detergents and reducing agents.

The eighth fibronectin type III domain of protein tyrosine phosphatase receptor J influences the formation of protein complexes and cell localization.

PubMed

Iuliano, Rodolfo; Raso, Cinzia; Quintiero, Alfina; Pera, Ilaria Le; Pichiorri, Flavia; Palumbo, Tiziana; Palmieri, Dario; Pattarozzi, Alessandra; Florio, Tullio; Viglietto, Giuseppe; Trapasso, Francesco; Croce, Carlo Maria; Fusco, Alfredo

2009-03-01

Regulation of receptor-type phosphatases can involve the formation of higher-order structures, but the exact role played in this process by protein domains is not well understood. In this study we show the formation of different higher-order structures of the receptor-type phosphatase PTPRJ, detected in HEK293A cells transfected with different PTPRJ expression constructs. In the plasma membrane PTPRJ forms dimers detectable by treatment with the cross-linking reagent BS(3) (bis[sulfosuccinimidyl]suberate). However, other PTPRJ complexes, dependent on the formation of disulfide bonds, are detected by treatment with the oxidant agent H(2)O(2) or by a mutation Asp872Cys, located in the eighth fibronectin type III domain of PTPRJ. A deletion in the eighth fibronectin domain of PTPRJ impairs its dimerization in the plasma membrane and increases the formation of PTPRJ complexes dependent on disulfide bonds that remain trapped in the cytoplasm. The deletion mutant maintains the catalytic activity but is unable to carry out inhibition of proliferation on HeLa cells, achieved by the wild type form, since it does not reach the plasma membrane. Therefore, the intact structure of the eighth fibronectin domain of PTPRJ is critical for its localization in plasma membrane and biological function.

Methods of staining target chromosomal DNA employing high complexity nucleic acid probes

DOEpatents

Gray, Joe W.; Pinkel, Daniel; Kallioniemi, Ol'li-Pekka; Kallioniemi, Anne; Sakamoto, Masaru

2006-10-03

Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Synthesis of Actinide Fluoride Complexes Using Trimethyltin Fluoride as a Mild and Selective Fluorinating Reagent

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

Kagan, Benjamin D.; Lichtscheidl, Alejandro G.; Erickson, Karla A.

Trimethyltin fluoride (Me₃SnF) is a mild and selective reagent for the installation of actinide fluoride bonds as demonstrated by the room temperature synthesis of a variety of organometallic and inorganic thorium(IV), uranium(IV), and uranium(V) fluoride complexes ((1,2,4-tBu₃C₅H₂)₂ThF₂, (C₅Me₅)₂U(F)(O-2,6-iPr₂C₆H₃), U(F)(O-2,6-tBu₂C₆H₃)₃, U(F)[N(SiMe₃)₂]₃ (C₅Me₅)₂UF₂(L) (L = O=PMe₃, O=PPh₃, O=PCy₃), and (C₅Me₅)₂U(F)(=N-2,6-iPr₂C₆H₃)) from their corresponding chloride, bromide, and iodide analogues. From these reactions, the new (C₅Me₅)₂UF₂(L) (L = O=PPh₃, O=PCy₃) uranium fluoride complexes were isolated and characterized by NMR spectroscopy and X-ray crystallography.

Synthesis of Actinide Fluoride Complexes Using Trimethyltin Fluoride as a Mild and Selective Fluorinating Reagent

DOE PAGES

Kagan, Benjamin D.; Lichtscheidl, Alejandro G.; Erickson, Karla A.; ...

2017-11-07

Trimethyltin fluoride (Me₃SnF) is a mild and selective reagent for the installation of actinide fluoride bonds as demonstrated by the room temperature synthesis of a variety of organometallic and inorganic thorium(IV), uranium(IV), and uranium(V) fluoride complexes ((1,2,4-tBu₃C₅H₂)₂ThF₂, (C₅Me₅)₂U(F)(O-2,6-iPr₂C₆H₃), U(F)(O-2,6-tBu₂C₆H₃)₃, U(F)[N(SiMe₃)₂]₃ (C₅Me₅)₂UF₂(L) (L = O=PMe₃, O=PPh₃, O=PCy₃), and (C₅Me₅)₂U(F)(=N-2,6-iPr₂C₆H₃)) from their corresponding chloride, bromide, and iodide analogues. From these reactions, the new (C₅Me₅)₂UF₂(L) (L = O=PPh₃, O=PCy₃) uranium fluoride complexes were isolated and characterized by NMR spectroscopy and X-ray crystallography.

Use of [superscript 1]H, [superscript 13]C, and [superscript 19]F-NMR Spectroscopy and Computational Modeling to Explore Chemoselectivity in the Formation of a Grignard Reagent

ERIC Educational Resources Information Center

Hein, Sara M.; Kopitzke, Robert W.; Nalli, Thomas W.; Esselman, Brian J.; Hill, Nicholas J.

2015-01-01

A discovery-based Grignard experiment for a second-year undergraduate organic chemistry course is described. The exclusive Grignard reagent formed by the reaction of 1-bromo-4-fluorobenzene (1) with Mg is 4-fluorophenylmagnesium bromide (2), which is treated with either benzophenone or CO[subscript 2] to produce the corresponding fluorinated…

E-RNAi: a web application for the multi-species design of RNAi reagents—2010 update

PubMed Central

Horn, Thomas; Boutros, Michael

2010-01-01

The design of RNA interference (RNAi) reagents is an essential step for performing loss-of-function studies in many experimental systems. The availability of sequenced and annotated genomes greatly facilitates RNAi experiments in an increasing number of organisms that were previously not genetically tractable. The E-RNAi web-service, accessible at http://www.e-rnai.org/, provides a computational resource for the optimized design and evaluation of RNAi reagents. The 2010 update of E-RNAi now covers 12 genomes, including Drosophila, Caenorhabditis elegans, human, emerging model organisms such as Schmidtea mediterranea and Acyrthosiphon pisum, as well as the medically relevant vectors Anopheles gambiae and Aedes aegypti. The web service calculates RNAi reagents based on the input of target sequences, sequence identifiers or by visual selection of target regions through a genome browser interface. It identifies optimized RNAi target-sites by ranking sequences according to their predicted specificity, efficiency and complexity. E-RNAi also facilitates the design of secondary RNAi reagents for validation experiments, evaluation of pooled siRNA reagents and batch design. Results are presented online, as a downloadable HTML report and as tab-delimited files. PMID:20444868

Impact of the excess sludge modification with selected chemical reagents on the increase of dissolved organic substances concentration compounds transformations in activated sludge.

PubMed

Zawieja, Iwona; Lidia, Wolny; Marta, Próba

2017-07-01

Submission of excess sludge initial disintegration process significantly affects the efficiency of anaerobic stabilization process. Expression of increasing the concentration of organic matter in dissolved form is to increase sludge disintegration. As a result of chemical modification is an increase of the chemical oxygen demand and the concentration of volatile fatty acids. The aim of this study was to determine the impact of the disintegration process with selected chemical reagents to increase the concentration of organic substances in dissolved form. The process of chemical disintegration of excess sludge was treated using the following reagents: Mg(OH) 2 , Ca(OH) 2 , HCl, H 2 SO 4 , H 2 O 2 . The modification was carried out at ambient temperature for 2, 6 and 24h. During sludge disintegration it was noticed the growth of indicators values that confirmed the susceptibility of prepared sludge to biodegradation. Copyright © 2017 Elsevier Inc. All rights reserved.

Water-Soluble Phosphinothiols for Traceless Staudinger Ligation and Integration with Expressed Protein Ligation

PubMed Central

Tam, Annie; Soellner, Matthew B.; Raines, Ronald T.

2010-01-01

The traceless Staudinger ligation is an effective means to synthesize an amide bond between two groups of otherwise orthogonal reactivity: a phosphinothioester and an azide. An important application of the Staudinger ligation is in the ligation of peptides at a variety of residues. Here, we demonstrate that the traceless Staudinger ligation can be achieved in water with a water-soluble reagent. Those reagents that provide a high yield of amide product discourage protonation of the nitrogen in the key iminophosphorane intermediate. The most efficacious reagent, bis(p-dimethylaminoethylphenyl)phosphinomethanethiol, mediates the rapid ligation of equimolar substrates in water. This reagent is also able to perform a transthioesterification reaction with the thioester intermediate formed during intein-mediated protein splicing. Hence, the traceless Staudinger ligation can be integrated with expressed protein ligation, extending the reach of modern protein chemistry. PMID:17713909

Harnessing catalytic pumps for directional delivery of microparticles in microchambers

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

Das, Sambeeta; Shklyaev, Oleg E.; Altemose, Alicia

The directed transport of microparticles in microfluidic devices is vital for efficient bioassays and fabrication of complex microstructures. There remains, but, a need for methods to propel and steer microscopic cargo that do not require modifying these particles. By using theory and experiments, we show that catalytic surface reactions can be used to deliver microparticle cargo to specified regions in microchambers. Here reagents diffuse from a gel reservoir and react with the catalyst-coated surface. Fluid density gradients due to the spatially varying reagent concentration induce a convective flow, which carries the suspended particles until the reagents are consumed. Consequently, themore » cargo is deposited around a specific position on the surface. The velocity and final peak location of the cargo can be tuned independently. And by increasing the local particle concentration, highly sensitive assays can be performed efficiently and rapidly. Moreover, the process can be repeated by introducing fresh reagent into the microchamber.« less

Harnessing catalytic pumps for directional delivery of microparticles in microchambers

DOE PAGES

Das, Sambeeta; Shklyaev, Oleg E.; Altemose, Alicia; ...

2017-02-17

The directed transport of microparticles in microfluidic devices is vital for efficient bioassays and fabrication of complex microstructures. There remains, but, a need for methods to propel and steer microscopic cargo that do not require modifying these particles. By using theory and experiments, we show that catalytic surface reactions can be used to deliver microparticle cargo to specified regions in microchambers. Here reagents diffuse from a gel reservoir and react with the catalyst-coated surface. Fluid density gradients due to the spatially varying reagent concentration induce a convective flow, which carries the suspended particles until the reagents are consumed. Consequently, themore » cargo is deposited around a specific position on the surface. The velocity and final peak location of the cargo can be tuned independently. And by increasing the local particle concentration, highly sensitive assays can be performed efficiently and rapidly. Moreover, the process can be repeated by introducing fresh reagent into the microchamber.« less

Ship-in-a-bottle catalysts

DOEpatents

Haw, James F.; Song, Weiguo

2006-07-18

In accordance with the present invention there is provided a novel catalyst system in which the catalytic structure is tailormade at the nanometer scale using the invention's novel ship-in-a-bottle synthesis techniques. The invention describes modified forms of solid catalysts for use in heterogeneous catalysis that have a microporous structure defined by nanocages. Examples include zeolites, SAPOs, and analogous materials that have the controlled pore dimensions and hydrothermal stability required for many industrial processes. The invention provides for modification of these catalysts using reagents that are small enough to pass through the windows used to access the cages. The small reagents are then reacted to form larger molecules in the cages.

Dosage delivery of sensitive reagents enables glove-box-free synthesis

NASA Astrophysics Data System (ADS)

Sather, Aaron C.; Lee, Hong Geun; Colombe, James R.; Zhang, Anni; Buchwald, Stephen L.

2015-08-01

Contemporary organic chemists employ a broad range of catalytic and stoichiometric methods to construct molecules for applications in the material sciences, and as pharmaceuticals, agrochemicals, and sensors. The utility of a synthetic method may be greatly reduced if it relies on a glove box to enable the use of air- and moisture-sensitive reagents or catalysts. Furthermore, many synthetic chemistry laboratories have numerous containers of partially used reagents that have been spoiled by exposure to the ambient atmosphere. This is exceptionally wasteful from both an environmental and a cost perspective. Here we report an encapsulation method for stabilizing and storing air- and moisture-sensitive compounds. We demonstrate this approach in three contexts, by describing single-use capsules that contain all of the reagents (catalysts, ligands, and bases) necessary for the glove-box-free palladium-catalysed carbon-fluorine, carbon-nitrogen, and carbon-carbon bond-forming reactions. This strategy should reduce the number of error-prone, tedious and time-consuming weighing procedures required for such syntheses and should be applicable to a wide range of reagents, catalysts, and substrate combinations.

Apparatus and method for polymer synthesis using arrays

DOEpatents

Brennan, Thomas M.

1995-01-01

A polymer synthesis apparatus (20) for building a polymer chain including a head assembly (21) having an array of nozzles (22) with each nozzle coupled to a reservoir (23) of liquid reagent (24) , and a base assembly (25) having an array of reaction wells (26). A transport mechanism (27) aligns the reaction wells (26) and selected nozzles (22) for deposition of the liquid reagent (24) into selected reaction wells (26). A sliding seal (30) is positioned between the head assembly (21) and the base assembly (25) to form a common chamber (31) enclosing both the reaction well (26) and the nozzles (22) therein. A gas inlet (70) into the common chamber (31), upstream from the nozzles (22), and a gas outlet (71) out of the common chamber (31) , downstream from the nozzles (22) , sweeps the common chamber ( 31 ) of toxic fumes emitted by the reagents. Each reaction well (26) includes an orifice (74) extending into the well (26) which is of a size and dimension to form a capillary liquid seal to retain the reagent solution (76) in the well (26) for polymer chain growth therein. A pressure regulating device (82) is provided for controlling a pressure differential, between a first gas pressure exerted on the reaction well (26) and a second gas pressure exerted on an exit (80) of the orifice, such that upon the pressure differential exceeding a predetermined amount, the reagent solution (76) is expelled from the well (26) through the orifice (74). A method of synthesis of a polymer chain in a synthesis apparatus (20) is also included.

Apparatus and method for polymer synthesis using arrays

DOEpatents

Brennan, Thomas M.

1996-01-01

A polymer synthesis apparatus (20) for building a polymer chain including a head assembly (21) having an array of nozzles (22) with each nozzle coupled to a reservoir (23) of liquid reagent (24), and a base assembly (25) having an array of reaction wells (26). A transport mechanism (27) aligns the reaction wells (26) and selected nozzles (22) for deposition of the liquid reagent (24) into selected reaction wells (26). A sliding seal (30) is positioned between the head assembly (21) and the base assembly (25) to form a common chamber (31) enclosing both the reaction well (26) and the nozzles (22) therein. A gas inlet (70) into the common chamber (31), upstream from the nozzles (22), and a gas outlet (71) out of the common chamber (31), downstream from the nozzles (22), sweeps the common chamber (31) of toxic fumes emitted by the reagents. Each reaction well ( 26) includes an orifice (74) extending into the well (26) which is of a size and dimension to form a capillary liquid seal to retain the reagent solution (76) in the well (26) for polymer chain growth therein. A pressure regulating device (82 ) is provided for controlling a pressure differential, between a first gas pressure exerted on the reaction well (26) and a second gas pressure exerted on an exit (80) of the orifice, such that upon the pressure differential exceeding a predetermined amount, the reagent solution (76) is expelled from the well (26) through the orifice (74). A method of synthesis of a polymer chain in a synthesis apparatus (20) is also included.

Synthesis of aryl thioethers through the N-chlorosuccinimide-promoted cross-coupling reaction of thiols with Grignard reagents.

PubMed

Cheng, Jun-Hao; Ramesh, Chintakunta; Kao, Hsin-Lun; Wang, Yu-Jen; Chan, Chien-Ching; Lee, Chin-Fa

2012-11-16

A convenient one-pot approach for the synthesis of aryl sulfides through the coupling of thiols with Grignard reagents in the presence of N-chlorosuccinimide is described. The sulfenylchlorides were formed when thiols were treated with N-chlorosuccinimide, and the resulting sulfenylchlorides were then directly reacted with Grignard reagents to provide aryl sulfides in good to excellent yields under mild reaction conditions. Functional groups including ester, fluoro, and chloro are tolerated by the reaction conditions employed. It is important to note that this method has a short reaction time (30 min in total) and represents an alternative approach for the synthesis of aryl sulfides over the existing protocols.

Synthesis of Soluble Alpha-Thiophene Oligomers. Monomer to Octamer

DTIC Science & Technology

1992-04-25

by forming the Grignard reagent of 5 [Mg (1.5 3 Schemne I a... Me3Si- -SMe 3 (1 1 2 Brj3-B ----m MeSi- 4 j 3 -- X d~-e me3Si J- SiW 3 (2) 3 4, X =Br 6...1.03 equiv), C6 H6 , 0* C to 230 C, 0.5 h, 94 %] and then to the corresponding Grignard reagent [Mg (1.5 equiv), ether, 23*C to 350 C] which was...PPh3)4 (5 mol %), toluene, reflux, 14 h] afforded the pentamer 1 in 47 % yield (eq g).25 The Grignard reagent of 13 was coupled with the iodide 16

Structures of Pseudomonas aeruginosa β-ketoacyl-(acyl-carrier-protein) synthase II (FabF) and a C164Q mutant provide templates for antibacterial drug discovery and identify a buried potassium ion and a ligand-binding site that is an artefact of the crystal form

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

Baum, Bernhard; Lecker, Laura S. M.; Zoltner, Martin

Three crystal structures of recombinant P. aeruginosa FabF are reported: the apoenzyme, an active-site mutant and a complex with a fragment of a natural product inhibitor. The characterization provides reagents and new information to support antibacterial drug discovery. Bacterial infections remain a serious health concern, in particular causing life-threatening infections of hospitalized and immunocompromised patients. The situation is exacerbated by the rise in antibacterial drug resistance, and new treatments are urgently sought. In this endeavour, accurate structures of molecular targets can support early-stage drug discovery. Here, crystal structures, in three distinct forms, of recombinant Pseudomonas aeruginosa β-ketoacyl-(acyl-carrier-protein) synthase II (FabF)more » are presented. This enzyme, which is involved in fatty-acid biosynthesis, has been validated by genetic and chemical means as an antibiotic target in Gram-positive bacteria and represents a potential target in Gram-negative bacteria. The structures of apo FabF, of a C164Q mutant in which the binding site is altered to resemble the substrate-bound state and of a complex with 3-(benzoylamino)-2-hydroxybenzoic acid are reported. This compound mimics aspects of a known natural product inhibitor, platensimycin, and surprisingly was observed binding outside the active site, interacting with a symmetry-related molecule. An unusual feature is a completely buried potassium-binding site that was identified in all three structures. Comparisons suggest that this may represent a conserved structural feature of FabF relevant to fold stability. The new structures provide templates for structure-based ligand design and, together with the protocols and reagents, may underpin a target-based drug-discovery project for urgently needed antibacterials.« less

Trifunctional conjugation reagents. Reagents that contain a biotin and a radiometal chelation moiety for application to extracorporeal affinity adsorption of radiolabeled antibodies.

PubMed

Wilbur, D Scott; Chyan, Ming-Kuan; Hamlin, Donald K; Kegley, Brian B; Nilsson, Rune; Sandberg, Bengt E B; Brechbiel, Martin

2002-01-01

A method of removing radiolabeled monoclonal antibodies (mAbs) from blood using a device external to the body, termed extracorporeal affinity-adsorption (EAA), is being evaluated as a means of decreasing irradiation of noncancerous tissues in therapy protocols. The EAA device uses an avidin column to capture biotinylated-radiolabeled mAbs from circulated blood. In this investigation, three trifunctional reagents have been developed to minimize the potential deleterious effect on antigen binding brought about by the combination of radiolabeling and biotinylation of mAbs required in the EAA approach. The studies focused on radiolabeling with (111)In and (90)Y, so the chelates CHX-A' '-DTPA and DOTA, which form stable attachments to these radionuclides, were incorporated in the trifunctional reagents. The first trifunctional reagent prepared did not incorporate a group to block the biotin cleaving enzyme biotinidase, but the two subsequent reagents coupled aspartic acid to the biotin carboxylate for that purpose. All three reagents used 4,7,10-trioxa-1,13-tridecanediamine as water-soluble spacers between an aminoisophthalate core and the biotin or chelation group. The mAb conjugates were radioiodinated to evaluate cell binding as a function of substitution. Radioiodination was used so that a direct comparison with unmodified mAb could be made. Evaluation of the number of conjugates per antibody versus cell binding immunoreactivities indicated that minimizing the number of conjugates was best. Interestingly, a decrease of radioiodination yield as a function of the number of isothiocyanate containing conjugates per mAb was noted. The decreased yields were presumably due to the presence of thiourea functionality formed in the conjugation reaction. Radiolabeling with (111)In and (90)Y was facile at room temperature for conjugates containing the CHX-A' ', but elevated temperature (e.g., 45 degrees C) was required to obtain good yields with the DOTA chelate. Stability of (90)Y labeled mAb in serum, and when challenged with 10 mM EDTA, was high. However, challenging the (90)Y labeled mAb with 10 mM DTPA demonstrated high stability for the DOTA containing conjugate, but low stability for the CHX-A' ' containing conjugate. Thus, the choice between these two chelating moieties might be made on requirements for facile and gentle labeling versus very high in vivo stability. Application of the trifunctional biotinylation reagents to the blood clearance of labeled antibodies in EAA is under investigation. The new reagents may also be useful for other applications.

Conversion of Arylboronic Acids to Tetrazoles Catalyzed by ONO Pincer-Type Palladium Complex.

PubMed

Vignesh, Arumugam; Bhuvanesh, Nattamai S P; Dharmaraj, Nallasamy

2017-01-20

A convenient synthesis of a library of tetrazoles through a novel and operationally simple protocol effecting the direct conversion of arylboronic acids catalyzed by a new ONO pincer-type Pd(II) complex under mild reaction conditions using the readily available reagents is reported. The palladium complex was reused up to four cycles in an open-flask condition.

Tested Demonstrations. Color, Solubility, and Complex Ion Equilibria of Nickel (II) Species in Aqueous Solution.

ERIC Educational Resources Information Center

Gilbert, George L., Ed.; And Others

1980-01-01

Presents three different procedures in which reagents are added in a specified order to a large beaker containing an aqueous solution of nickel sulfate. Complex ions of nickel (II) are prepared by using aqueous solutions of ammonia, ethylenediamine, dimethylglyoxime, and cyanide ion. (CS)

Catalytic enantioselective addition of Grignard reagents to aromatic silyl ketimines

NASA Astrophysics Data System (ADS)

Rong, Jiawei; Collados, Juan F.; Ortiz, Pablo; Jumde, Ravindra P.; Otten, Edwin; Harutyunyan, Syuzanna R.

2016-12-01

α-Chiral amines are of significant importance in medicinal chemistry, asymmetric synthesis and material science, but methods for their efficient synthesis are scarce. In particular, the synthesis of α-chiral amines with the challenging tetrasubstituted carbon stereocentre is a long-standing problem and catalytic asymmetric additions of organometallic reagents to ketimines that would give direct access to these molecules are underdeveloped. Here we report a highly enantioselective catalytic synthesis of N-sulfonyl protected α-chiral silyl amines via the addition of inexpensive, easy to handle and readily available Grignard reagents to silyl ketimines. The key to this success was our ability to suppress any unselective background addition reactions and side reduction pathway, through the identification of an inexpensive, chiral Cu-complex as the catalytically active structure.

Complex formation of vanadium(V) with resorcylalhydrazides of carboxylic acids

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

Dudarev, V.I.; Dolgorev, V.A.; Volkov, A.N.

1986-08-01

In this work, a previous investigation of hydrazine derivatives as analytical reagents for vanadium(V) was continued. The authors studied arylalhydrazones -- derivatives of resorcylalhydrazides of anisic (RHASA), anthranilic (RHANA), and benzoic (RHBA) acids. The reagents presented differ from those studied previously by the presence of a second hydroxy group in the para-position of the benzene ring -the resorcinol fragment -- and substituents in the benzoin fragment. Such changes made it possible to increase the solubility of the reagents in aqueous medium and to estimate the change in the main spectrophotometric parameters of the analytical reaction. A rapid method was developedmore » for the determination of vanadium in steels with the resorcylalhydrazide of anthranilic acid. The minimum determinable vanadium content is 0.18 micrograms/ml.« less

Validation of methods on formalin testing in tofu and determination of 3,5-diacetyl-dihydrolutidine stability by UV-Vis spectrophotometry

NASA Astrophysics Data System (ADS)

Rohyami, Yuli; Pribadi, Rizki Maulana

2017-12-01

Formalin is a food preservative that is prohibited by the government, but the abuse of these chemicals is still widely found. The presence of formalin can be detected by using a typical reagent that can ensure the presence of formaldehyde qualitatively and quantitatively. This research was conducted to validate the method of determining formalin in tofu by using Nash reagent in UV-Vis spectrophotometry. The addition of Nash reagent will lead to the formation of diacetyldihydrolutidin complex. The study was performed by stability test of deacetyldihydrolutidine complex against time and pH. Validation of methods for formalin testing in tofu with diacetyldihydrolutidine by UV-Vis spectrophotometry. The results showed that 3,5-diacetyl-dihydrolutidine complex is stable at pH of 7 and stable in the range of 70-120 minutes. The validation shows that the method gives good precision and accuracy of 83.78%. The method has the limit of detection of 1.3681 µg/mL, limit of quantification of 4,5603 µg/mL, and the estimated uncertainty of measurement of 1.30 µg/mL. The test showed that the tofu contained formalin 3.09 ± 1.30 µg/mL. These values provide information that this method can be used as a procedure for the determination of formalin on tofu.

Organophosphazenes. 15. Reactions of Hexafluorocyclotriphosphazene with Tert- and n-Butyl Lithium Reagents

DTIC Science & Technology

1981-12-04

H ECU’ITY CLASSIFICATION OF THIS PAGE (When frl,* IFnfered) REPORT DOCUMENTATION PAGE - RE INSTRUCTIONSBEFORE COMPLETING FORM 1. REPORT NUMBER 2...GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER 10 _ _ _ _V11 * 4. TITLE (and Subtitle) S. TYPE OF REPORT I PERIOD COVERED Organoohosphazenes. 15...Reactions of Hexafluro- Technical Report cvclotriphosDhazene with Tert- and n-Butvl Lithium Reagents . PERFORMING ORG. REPORT NUMSER 7. AUTHOR•,) S

One-Step Synthesis of Aliphatic Potassium Acyltrifluoroborates (KATs) from Organocuprates.

PubMed

Liu, Sizhou M; Wu, Dino; Bode, Jeffrey W

2018-04-20

A one-step synthesis of aliphatic KATs from organocuprates is reported. Organolithium and organomagnesium reagents were readily transmetalated onto Cu(I) and coupled with a KAT-forming reagent to yield the respective aliphatic KAT. The protocol is suitable for primary, secondary and-for the first time-tertiary alkyl substrates. These protocols considerably expand the range of KATs that can be readily accessed in one step from commercially available starting materials.

Facially Selective Cu-catalyzed Carbozincation of Cyclopropenes Using Arylzinc Reagents Formed by Sequential I/Mg/Zn exchange

PubMed Central

Tarwade, Vinod; Selvaraj, Ramajeyam; Fox, Joseph M.

2012-01-01

Described is a Cu-catalyzed directed carbozincation of cyclopropenes with organozinc reagents prepared by I/Mg/Zn exchange. This protocol broadens the scope with respect to functional group tolerance and enables use of aryl iodide precursors, rather than purified diorganozinc precursors. Critical to diastereoselectivity of the carbozincation step is the removal of magnesium halide salts after transmetallation with ZnCl2. PMID:23035947

Enantioselective and regiodivergent copper-catalyzed conjugate addition of trialkylaluminium reagents to extended nitro-Michael acceptors.

PubMed

Tissot, Matthieu; Müller, Daniel; Belot, Sébastien; Alexakis, Alexandre

2010-06-18

The first highly enantioselective and regiodivergent conjugate addition of trialkylaluminium reagents to nitrodienes and nitroenynes is described. By a design of the substrate and a fine-tuning of the reaction conditions, it is possible to selectively form the 1,4- or 1,6-adduct. The same combination of catalyst, copper source, and a ferrocene-based phosphine ligand afforded enantioselectivities up to 95% and 91%, respectively.

Expanding Thorium Hydride Chemistry Through Th²⁺, Including the Synthesis of a Mixed-Valent Th⁴⁺/Th³⁺ Hydride Complex.

PubMed

Langeslay, Ryan R; Fieser, Megan E; Ziller, Joseph W; Furche, Filipp; Evans, William J

2016-03-30

The reactivity of the recently discovered Th(2+) complex [K(18-crown-6)(THF)2][Cp″3Th], 1 [Cp'' = C5H3(SiMe3)2-1,3], with hydrogen reagents has been investigated and found to provide syntheses of new classes of thorium hydride compounds. Complex 1 reacts with [Et3NH][BPh4] to form the terminal Th(4+) hydride complex Cp″3ThH, 2, a reaction that formally involves a net two-electron reduction. Complex 1 also reacts in the solid state and in solution with H2 to form a mixed-valent bimetallic product, [K(18-crown-6)(Et2O)][Cp″2ThH2]2, 3, which was analyzed by X-ray crystallography, electron paramagnetic resonance and optical spectroscopy, and density functional theory. The existence of 3, which formally contains Th(3+) and Th(4+), suggested that KC8 could reduce [(C5Me5)2ThH2]2. In the presence of 18-crown-6, this reaction forms an analogous mixed-valent product formulated as [K(18-crown-6)(THF)][(C5Me5)2ThH2]2, 4. A similar complex with (C5Me4H)(1-) ligands was not obtained, but reaction of (C5Me4H)3Th with H2 in the presence of KC8 and 2.2.2-cryptand at -45 °C produced two monometallic hydride products, namely, (C5Me4H)3ThH, 5, and [K(2.2.2-cryptand)]{(C5Me4H)2[η(1):η(5)-C5Me3H(CH2)]ThH]}, 6. Complex 6 contains a metalated tetramethylcyclopentadienyl dianion, [C5Me3H(CH2)](2-), that binds in a tuck-in mode.

Redox routes to substitution of aluminum(III): synthesis and characterization of (IP-)2AlX (IP = α-iminopyridine, X = Cl, Me, SMe, S2CNMe2, C≡CPh, N3, SPh, NHPh).

PubMed

Myers, Thomas W; Holmes, Alexandra L; Berben, Louise A

2012-08-20

Redox active ligands are shown to facilitate a variety of group transfer reactions at redox inert aluminum(III). Disulfides can be used as a two-electron group transfer reagent, and we show that (IP(-))(2)AlSR can be formed by reaction of [(THF)(6)Na][(IP(2-))(2)Al] (1c) with disulfides RSSR (where X = C(S)NMe(2), 4; SMe, 5). In a more general redox route to substitution of aluminum bis(iminopyridine) complexes, we report zinc(II) salts as a group transfer reagent. Reaction of [((R)IP(2-))(2)Al](-) (R = H, 1c; Me, 1d) with ZnX(2) affords ((R)IP(-))(2)AlX (where IP = iminopyridine, R = H, and X = Cl, 2; CCPh, 6; N(3), 7; SPh, 8; or R = Me and X = NHPh, 9). Single crystal X-ray diffraction analysis of the complexes reveal that each of the five coordinate complexes reported here has a trigonal bipyramidal geometry with τ = 0.668 - 0.858. We observed a correlation between the greatest deviations from ideal trigonal bipyramidal symmetry (lowest τ values), the bond lengths consistent with smallest degree of ligand reduction, and the least polarizable X ligand in (IP(-))(2)AlX. Complex 4 is six-coordinate and is best described as distorted octahedral. Variable temperature magnetic susceptibility measurements indicate that each of the complexes 3-9 has a biradical electronic structure similar to previously reported 2. Magnetic exchange coupling constants in the range J = -94 to -212 cm(-1) were fit to the data for 2-9 to describe the energy of antiferromagnetic interaction between ligand radicals assuming a spin Hamiltonian of the form Ĥ = -2JŜ(L(1))·Ŝ(L(2)). The strongest coupling occurs when the angle between the ligand planes is smallest, presumably to afford good overlap with the Al-X σ* orbital. Electrochemical properties of the complexes were probed using cyclic voltammetry and each of 3-9 displayed a reversible two-electron reduction and two quasi-reversible one-electron oxidation processes. The energy of the ligand based redox processes for 2-9 differ by about 150 mV over all complexes and show a correlation with the degree of IP(-) reduction observed crystallographically; more reduced IP(-) ligands require higher potentials for further reduction. Comproportionation constants that describe the equilibrium for the reaction (IP(-))(2)AlX + (IP)(2)AlX ↔ (IP(-))(IP)AlX fall in the range of K(c) = 10(5.7) to 10(7.9) for 3-9.

Comparing Amide-Forming Reactions Using Green Chemistry Metrics in an Undergraduate Organic Laboratory

ERIC Educational Resources Information Center

Fennie, Michael W.; Roth, Jessica M.

2016-01-01

In this laboratory experiment, upper-division undergraduate chemistry and biochemistry majors investigate amide-bond-forming reactions from a green chemistry perspective. Using hydrocinnamic acid and benzylamine as reactants, students perform three types of amide-forming reactions: an acid chloride derivative route; a coupling reagent promoted…

Formation of W(3)A(1) electron-transferring flavoprotein (ETF) hydroquinone in the trimethylamine dehydrogenase x ETF protein complex.

PubMed

Jang, M H; Scrutton, N S; Hille, R

2000-04-28

The electron-transferring flavoprotein (ETF) from Methylophilus methylotrophus (sp. W(3)A(1)) exhibits unusual oxidation-reduction properties and can only be reduced to the level of the semiquinone under most circumstances (including turnover with its physiological reductant, trimethylamine dehydrogenase (TMADH), or reaction with strong reducing reagents such as sodium dithionite). In the present study, we demonstrate that ETF can be reduced fully to its hydroquinone form both enzymatically and chemically when it is in complex with TMADH. Quantitative titration of the TMADH x ETF protein complex with sodium dithionite shows that a total of five electrons are taken up by the system, indicating that full reduction of ETF occurs within the complex. The results indicate that the oxidation-reduction properties of ETF are perturbed upon binding to TMADH, a conclusion further supported by the observation of a spectral change upon formation of the TMADH x ETF complex that is due to a change in the environment of the FAD of ETF. The results are discussed in the context of ETF undergoing a conformational change during formation of the TMADH x ETF electron transfer complex, which modulates the spectral and oxidation-reduction properties of ETF such that full reduction of the protein can take place.

Solid-phase extraction of some heavy metal ions on a double-walled carbon nanotube disk and determination by flame atomic absorption spectrometry.

PubMed

Karatepe, Aslihan; Soylak, Mustafa; Elçi, Latif

2011-01-01

A new preconcentration method was developed for the determination of trace amounts of Cu(II), Fe(III), Pb(II), Ni(II), and Cd(II) on a double-walled carbon nanotube disk. 4-(2-Thiazolylazo) resorcinol was used as a complexing reagent. The effects of parameters, including pH of the solutions, amounts of complexing reagent, eluent type, sample volume, flow rates of solutions, and matrix ions were examined for quantitative recoveries of the studied analyte ions. The retained metal ions were eluted by 2 M HNO3. The LOD values for the analytes were in the range of 0.7-4.4 microg/mL. Natural water samples and standard reference materials were analyzed by the presented method.

A novel differential pulse voltammetric (DPV) method for measuring the antioxidant capacity of polyphenols-reducing cupric neocuproine complex.

PubMed

Tufan, Ayşe Nur; Baki, Sefa; Güçlü, Kubilay; Özyürek, Mustafa; Apak, Reşat

2014-07-23

A novel differential pulse voltammetric (DPV) method is presented, using a chromogenic oxidizing reagent, cupric neocuproine complex (Cu(Nc)2(2+)), for the assessment of antioxidant capacity of polyphenolic compounds (i.e., flavonoids, simple phenolic acids, and hydroxycinnamic acids), ascorbic acid, and real samples for the first time. The electrochemical behavior of the Cu(Nc)2(2+) complex was studied by cyclic voltammetry at a glassy carbon (GC) electrode. The electroanalytical method was based on the reduction of Cu(Nc)2(2+) to Cu(Nc)2(+) by antioxidants and electrochemical detection of the remaining Cu(II)-Nc (unreacted complex), the difference being correlated to antioxidant capacity of the analytes. The calibration curves of individual compounds comprising polyphenolics and vitamin C were constructed, and their response sensitivities and linear concentration ranges were determined. The reagent on the GC electrode retained its reactivity toward antioxidants, and the measured trolox equivalent antioxidant capacity (TEAC) values of various antioxidants suggested that the reactivity of the Cu(II)-Nc reagent is comparable to that of the solution-based spectrophotometric cupric ion reducing antioxidant capacity (CUPRAC) assay. This electroanalytical method better tolerated sample turbidity and provided higher sensitivity (i.e., lower detection limits) in antioxidant determination than the spectrophotometric assay. The proposed method was successfully applied to the measurement of total antioxidant capacity (TAC) in some herbal tea samples such as green tea, sage, marjoram, and alchemilla. Results demonstrated that the proposed voltammetric method has precision and accuracy comparable to those of the spectrophotometric CUPRAC assay.

Rapid Fabrication of Cell-Laden Alginate Hydrogel 3D Structures by Micro Dip-Coating.

PubMed

Ghanizadeh Tabriz, Atabak; Mills, Christopher G; Mullins, John J; Davies, Jamie A; Shu, Wenmiao

2017-01-01

Development of a simple, straightforward 3D fabrication method to culture cells in 3D, without relying on any complex fabrication methods, remains a challenge. In this paper, we describe a new technique that allows fabrication of scalable 3D cell-laden hydrogel structures easily, without complex machinery: the technique can be done using only apparatus already available in a typical cell biology laboratory. The fabrication method involves micro dip-coating of cell-laden hydrogels covering the surface of a metal bar, into the cross-linking reagents calcium chloride or barium chloride to form hollow tubular structures. This method can be used to form single layers with thickness ranging from 126 to 220 µm or multilayered tubular structures. This fabrication method uses alginate hydrogel as the primary biomaterial and a secondary biomaterial can be added depending on the desired application. We demonstrate the feasibility of this method, with survival rate over 75% immediately after fabrication and normal responsiveness of cells within these tubular structures using mouse dermal embryonic fibroblast cells and human embryonic kidney 293 cells containing a tetracycline-responsive, red fluorescent protein (tHEK cells).

Novel 1:1 labeling and purification process for C-terminal thioester and single cysteine recombinant proteins using generic peptidic toolbox reagents.

PubMed

Portal, Christophe F; Seifert, Jan-Marcus; Buehler, Christof; Meisner-Kober, Nicole-Claudia; Auer, Manfred

2014-07-16

We developed a versatile set of chemical labeling reagents which allow dye ligation to the C-terminus of a protein or a single internal cysteine and target purification in a simple two-step process. This simple process results in a fully 1:1 labeled conjugate suitable for all quantitative fluorescence spectroscopy and imaging experiments. We refer to a "generic labeling toolbox" because of the flexibility to choose one of many available dyes, spacers of different lengths and compositions which increase the target solubility, a variety of affinity purification tags, and different cleavage chemistries to release the 1:1 labeled proteins. Studying protein function in vitro or in the context of live cells and organisms is of vital importance in biological research. Although label free detection technologies gain increasing interest in molecular recognition science, fluorescence spectroscopy is still the most often used detection technique for assays and screens both in academic as well as in industrial groups. For generations, fluorescence spectroscopists have labeled their proteins of interest with small fluorescent dyes by random chemical linking on the proteins' exposed lysines and cysteines. Chemical reactions with a certain excess of activated esters or maleimides of longer wavelength dyes hardly ever result in quantitative labeling of the target protein. Most of the time, more than one exposed amino acid side chain reacts. This results in a mixture of dye-protein complexes of different labeling stoichiometries and labeling sites. Only mass spectrometry allows resolving the precise chemical composition of the conjugates. In "classical" ensemble averaging fluorescent experiments, these labeled proteins are still useful, and quantification of, e.g., ligand binding experiments, is achieved via knowledge of the overall protein concentration and a fluorescent signal change which is proportional to the amount of complex formed. With the development of fluorescence fluctuation analysis techniques working at single molecule resolution, like fluorescence correlation spectroscopy (FCS), fluorescence cross correlation spectroscopy (FCCS), fluorescence intensity diffusion analysis (FIDA), etc., it became important to work with homogeneously labeled target proteins. Each molecule participating in a binding equilibrium should be detectable when it freely fluctuates through the confocal focus of a microscope. The measured photon burst for each transition contains information about the size and the stoichiometry of a protein complex. Therefore, it is important to work with reagents that contain an exact number of tracers per protein at identical positions. The ideal fluorescent tracer-protein complex stoichiometry is 1:1. While genetic tags such as fluorescent proteins (FPs) are widely used to detect proteins, FPs have several limitations compared to chemical tags. For example, FPs cannot easily compete with organic dyes in the flexibility of modification and spectral range; moreover, FPs have disadvantages in brightness and photostability and are therefore not ideal for most biochemical single molecule studies. We present the synthesis of a series of exemplaric toolbox reagents and labeling results on three target proteins which were needed for high throughput screening experiments using fluorescence fluctuation analysis at single molecule resolution. On one target, Hu-antigen R (HuR), we demonstrated the activity of the 1:1 labeled protein in ribonucleic acid (RNA) binding, and the ease of resolving the stoichiometry of an RNA-HuR complex using the same dye on protein and RNA by Fluorescence Intensity Multiple Distribution Analysis (FIMDA) detection.

New concept to remove heavy metals from liquid waste based on electrochemical pH-switchable immobilized ligands

NASA Astrophysics Data System (ADS)

Pascal, Viel; Laetitia, Dubois; Joël, Lyskawa; Marc, Sallé; Serge, Palacin

2007-01-01

Absorption on resins is often used as secondary step in the treatment of water-based effluents, in order to reach very low concentrations. The separation of the trapped effluents from the resins and the regeneration of the resins for further use create wide volumes of secondary effluents coming from the washings of the resins with chemical reagents. We propose an alternative solution based on a "surface strategy" through adsorption phenomena and electrical control of the expulsion stage. The final goal is to limit or ideally to avoid the use of chemical reagents at the expulsion (or regeneration) stage of the depolluting process. Heavy metal ions were captured on active filters composed by a conducting surface covered by poly-4-vinylpyridine (P 4VP). Due to pyridine groups those polymer films have chelating properties for copper ions. Our strategy for electrical triggering of the copper expulsion in aqueous medium is based on pH sensitive chelating groups. Applying moderate electro-oxidizing conditions generates acidic conditions in the vicinity of the electrode, i.e. "inside" the polymer film. This allows a "switch-off" of the complexing properties of the film from the basic form of pyridine to pyridinium. Interestingly, no buffer washing is necessary to restore (or "switch-on") the complexing properties of the polymer film because the pH of the external medium is left unchanged by the electrochemical effect that affects only the vicinity of the electrode. Switch-on/switch-off cycles are followed and attested by IR spectroscopy and EQCM method.

Capillary electrophoresis method to determine siRNA complexation with cationic liposomes.

PubMed

Furst, Tania; Bettonville, Virginie; Farcas, Elena; Frere, Antoine; Lechanteur, Anna; Evrard, Brigitte; Fillet, Marianne; Piel, Géraldine; Servais, Anne-Catherine

2016-10-01

Small interfering RNA (siRNA) inducing gene silencing has great potential to treat many human diseases. To ensure effective siRNA delivery, it must be complexed with an appropriate vector, generally nanoparticles. The nanoparticulate complex requires an optimal physiochemical characterization and the complexation efficiency has to be precisely determined. The methods usually used to measure complexation in gel electrophoresis and RiboGreen ® fluorescence-based assay. However, those approaches are not automated and present some drawbacks such as the low throughput and the use of carcinogenic reagents. The aim of this study is to develop a new simple and fast method to accurately quantify the complexation efficiency. In this study, capillary electrophoresis (CE) was used to determine the siRNA complexation with cationic liposomes. The short-end injection mode applied enabled siRNA detection in less than 5 min. Moreover, the CE technique offers many advantages compared with the other classical methods. It is automated, does not require sample preparation and expensive reagents. Moreover, no mutagenic risk is associated with the CE approach since no carcinogenic product is used. Finally, this methodology can also be extended for the characterization of other types of nanoparticles encapsulating siRNA, such as cationic polymeric nanoparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of the difference in color development in the dye-binding method due to the kind of buffer solution.

PubMed

Suzuki, Yuji

2006-06-01

In a dye-binding method using a pH indicator, color development has reportedly been affected by the kind of buffer solution used in the color reagent. This phenomenon was analyzed by using a calculation based on the assumption that the anion of the buffer solution also reacts with protein. Color development decreases with increases in the anion concentration of the buffer solution and in the equilibrium constant of the reaction between the anion and protein. The differences in color development due to the kind of buffer solution can be attributed to differences in the equilibrium constant of the reaction forming the anion-protein complex and to the concentration of the anion between the buffer solutions.

Uptake of Au(III) Ions by Aluminum Hydroxide and Their Spontaneous Reduction to Elemental Gold (Au(0)).

PubMed

Yokoyama; Matsukado; Uchida; Motomura; Watanabe; Izawa

2001-01-01

The behavior of AuCl(4)(-) ions during the formation of aluminum hydroxide at pH 6 was examined. With an increase in NaCl concentration, the content of gold taken up by aluminum hydroxide decreased, suggesting that chloro-hydroxy complexes of Au(III) ion were taken up due to the formation of Al-O-Au bonds. It was found unexpectedly that the Au(III) ions taken up were spontaneously reduced to elemental gold without addition of a specific reducing reagent and then colloidal gold particles were formed. The mechanisms for the uptake of Au(III) ions by aluminum hydroxide and for their spontaneous reduction are discussed. Copyright 2001 Academic Press.

Pretargeting immunotherapy: a novel treatment approach for systemic amyloidosis.

PubMed

Wall, Jonathan S; Foster, James S; Martin, Emily B; Kennel, Stephen J

2017-09-01

The amyloidoses are a complex group of disorders characterized by the deposition of proteinaceous amyloid fibrils in vital organs. The deposits are nonimmunogenic and may be composed of one of more than 35 proteins. We have developed a two-stage immunotherapeutic approach using peptides that recognize most, if not all, amyloid deposits to facilitate amyloid clearance. In the first embodiment, we have developed a bifunctional peptope to enhance and expand the utility of currently available antibodies. In the second, we have generated peptide-reactive antibodies that can be targeted to the amyloid deposits by peptides thereby providing alternative reagents for immunotherapy of amyloidosis. These technologies provide tools for treating the many forms of amyloid disease, restoring organ function and enhancing patient survival.

Synthesis of 6-alkyluridines from 6-cyanouridine via zinc(II) chloride-catalyzed nucleophilic substitution with alkyl Grignard reagents.

PubMed

Shih, Yu-Chiao; Yang, Ya-Ying; Lin, Chun-Chi; Chien, Tun-Cheng

2013-04-19

6-Cyanouracil derivatives underwent a direct nucleophilic substitution reaction with alkyl Grignard reagents in the presence of zinc(II) chloride as a catalyst to form the corresponding 6-alkyluracils. This methodology is applicable to sugar-protected 6-cyanouridine and 6-cyano-2'-deoxyuridine without the protection at the N(3)-imide and provides a facile and general access to versatile 6-alkyluracil and 6-alkyluridine derivatives.

One-Pot Multicomponent Coupling Methods for the Synthesis of Diastereo- and Enantioenriched (Z)-Trisubstituted Allylic Alcohols

PubMed Central

Kerrigan, Michael H.; Jeon, Sang-Jin; Chen, Young K.; Salvi, Luca; Carroll, Patrick J.; Walsh, Patrick J.

2009-01-01

(Z)-Trisubstituted allylic alcohols are widespread structural motifs in natural products and biologically active compounds but are difficult to directly prepare. Introduced herein is a general one-pot multicomponent coupling method for the synthesis of (Z)-α,α,β-trisubstituted allylic alcohols. (Z)-Trisubstituted vinylzinc reagents are formed in situ by initial hydroboration of 1-bromo-1-alkynes. Addition of dialkylzinc reagents induces a 1,2-metallate rearrangement that is followed by a boron-to-zinc transmetallation. The resulting vinylzinc reagents add to a variety of prochiral aldehydes to produce racemic (Z)-trisubstituted allylic alcohols. When enantioenriched aldehyde substrates are employed (Z)-trisubstituted allylic alcohols are isolated with high dr (>20:1 in many cases). For example, vinylation of enantioenriched benzyl protected α- and β-hydroxy propanal derivatives furnished the expected anti-Felkin addition products via chelation control. Surprisingly, silyl protected α-hydroxy aldehydes also afford anti-Felkin addition products. A protocol for the catalytic asymmetric addition of (Z)-trisubstituted vinylzinc reagents to prochiral aldehydes with a (−)-MIB-based catalyst has also been developed. Several additives were investigated as inhibitors of the Lewis acidic alkylzinc halide byproducts, which promote the background reaction to form the racemate. α-Ethyl and α-cyclohexyl (Z)-trisubstituted allylic alcohols can now be synthesized with excellent levels of enantioselectivity in the presence of diamine inhibitors. PMID:19476375

Enhancing struvite precipitation potential for ammonia nitrogen removal in municipal landfill leachate.

PubMed

Kim, Daekeun; Ryu, Hong-Duck; Kim, Man-Soo; Kim, Jinhyeong; Lee, Sang-Ill

2007-07-19

This study was conducted to improve struvite precipitation for NH4-N removal purpose in landfill leachate. For this purpose, we evaluated the effect of the feeding sequence of precipitating reagents (magnesium, orthophosphate, and buffering reagent) on NH4-N removal by forming struvite deposits. Struvite precipitation effectively proceeded by an addition of excess magnesium and phosphate sources followed by an addition of the buffering reagent, in which condition the local formation of inappropriate deposits or the contamination of the desired struvite was minimized. We also tested the effect of struvite addition as the seeding materials on NH4-N removal. Seed addition would increase the potential for the struvite crystal growth, which enhanced NH4-N removal performance in landfill leachate treatment.

Immune complexes formed following the binding of anti-platelet factor 4 (CXCL4) antibodies to CXCL4 stimulate human neutrophil activation and cell adhesion.

PubMed

Xiao, Zhihua; Visentin, Gian P; Dayananda, Kannayakanahalli M; Neelamegham, Sriram

2008-08-15

We tested the possibility that immune complexes formed following platelet factor 4 (PF4/CXCL4) binding to anti-PF4 antibody can stimulate neutrophil activation, similar to previous reports with platelets. Monoclonal Abs against PF4 and IgG from a heparin-induced thrombocytopenia (HIT) patient were applied. We observed that although PF4 or anti-PF4 antibody alone did not alter neutrophil function, costimulation with both reagents resulted in approximately 3-fold increase in cell surface Mac-1 expression, enhanced cell adhesion via L-selectin and CD18 integrins, and degranulation of secondary and tertiary granules. The level of Mac-1 up-regulation peaked at an intermediate PF4 dose, suggesting that functional response varies with antigen-antibody stoichiometry. PF4 binding to neutrophils was blocked by chondroitinase ABC. Cell activation was inhibited by both chondroitinase ABC and anti-CD32/FcgammaRII blocking mAb, IV.3. Confocal microscopy demonstrated that immune complexes colocalize with CD32a. Studies with HIT IgG demonstrated that neutrophils could be activated in the absence of exogenous heparin. These data, together, show that leukocyte surface chondroitin sulfates promote neutrophil activation by enhancing immune-complex binding to CD32a. Studies with recombinant PF4 suggest a role for arginine 49 in stabilizing PF4-chondroitin binding. Neutrophils activated via this mechanism may contribute to thrombosis and inflammation in patients mounting an immune response to PF4-heparin.

Method for polymer synthesis in a reaction well

DOEpatents

Brennan, Thomas M.

1998-01-01

A method of synthesis for building a polymer chain, oligonucleotides in particular, by sequentially adding monomer units to at least one solid support for growing and immobilizing a polymer chain thereon in a liquid reagent solution. The method includes the step of: A) depositing a liquid reagent in a reaction well (26) in contact with at least one solid support and at least one monomer unit of the polymer chain affixed to the solid support. The well (26) includes at least one orifice (74) extending into the well (26), and is of a size and dimension to form a capillary liquid seal to retain the reagent solution in the well (26) to enable polymer chain growth on the solid support. The method further includes the step of B) expelling the reagent solution from the well (26), while retaining the polymer chain therein. This is accomplished by applying a first gas pressure to the reaction well such that a pressure differential between the first gas pressure and a second gas pressure exerted on an exit (80) of the orifice (74) exceeds a predetermined amount sufficient to overcome the capillary liquid seal and expel the reagent solution from the well (26) through the orifice exit (80).

Method for polymer synthesis in a reaction well

DOEpatents

Brennan, T.M.

1998-09-29

A method of synthesis is described for building a polymer chain, oligonucleotides in particular, by sequentially adding monomer units to at least one solid support for growing and immobilizing a polymer chain thereon in a liquid reagent solution. The method includes the step of: (A) depositing a liquid reagent in a reaction well in contact with at least one solid support and at least one monomer unit of the polymer chain affixed to the solid support. The well includes at least one orifice extending into the well, and is of a size and dimension to form a capillary liquid seal to retain the reagent solution in the well to enable polymer chain growth on the solid support. The method further includes the step of (B) expelling the reagent solution from the well, while retaining the polymer chain therein. This is accomplished by applying a first gas pressure to the reaction well such that a pressure differential between the first gas pressure and a second gas pressure exerted on an exit of the orifice exceeds a predetermined amount sufficient to overcome the capillary liquid seal and expel the reagent solution from the well through the orifice exit. 9 figs.

Identification of cross-linked amino acids in the protein pair HmaL23-HmaL29 from the 50S ribosomal subunit of the archaebacterium Haloarcula marismortui.

PubMed

Bergmann, U; Wittmann-Liebold, B

1993-03-23

50S ribosomal subunits from the extreme halophilic archaebacterium Haloarcula marismortui were treated with the homobifunctional protein-protein cross-linking reagents diepoxybutane (4 A) and dithiobis(succinimidyl propionate) (12 A). The dominant product with both cross-linking reagents was identified on the protein level as HmaL23-HmaL29, which is homologous to the protein pair L23-L29 from Escherichia coli [Walleczek, J., Martin, T., Redl, B., Stöffler-Meilicke, M., & Stöffler, G. (1989) Biochemistry 28, 4099-4105] and from Bacillus stearothermophilus [Brockmöller, J., & Kamp, R. M. (1986) Biol. Chem. Hoppe-Seyler 367, 925-935]. To reveal the exact cross-linking site in HmaL23-HmaL29, the cross-linked complex was purified on a preparative scale by conventional and high-performance liquid chromatography. After endoproteolytic fragmentation of the protein pair, the amino acids engaged in cross-link formation were unambiguously identified by N-terminal sequence analysis and mass spectrometry of the cross-linked peptides. The cross-link is formed between lysine-57 in the C-terminal region of HmaL29 and the alpha-amino group of the N-terminal serine in protein HmaL23, irrespective of the cross-linking reagent. This result demonstrates that the N-terminal region of protein HmaL23 and the C-terminal domain of HmaL29 are highly flexible so that the distance between the two polypeptide chains can vary by at least 8 A. Comparison of our cross-linking results with those obtained with B. stearothermophilus revealed that the fine structure within this ribosomal domain is at least partially conserved.

Multifunctional silicon surfaces: reaction of dichlorocarbene generated from Seyferth reagent with hydrogen-terminated silicon (111) surfaces.

PubMed

Liu, Wenjun; Sharp, Ian D; Tilley, T Don

2014-01-14

Insertion of dichlorocarbene (:CCl2), generated by decomposition of the Seyferth reagent PhHgCCl2Br, into the Si-H bond of a tertiary silane to form a Si-CCl2H group is an efficient homogeneous, molecular transformation. A heterogeneous version of this reaction, between PhHgCCl2Br and a silicon (111) surface terminated by tertiary Si-H bonds, was studied using a combination of surface-sensitive infrared and X-ray photoelectron spectroscopies. The insertion of dichlorocarbene into surface Si-H bonds parallels the corresponding reaction of silanes in solution, to produce surface-bound dichloromethyl groups (Si-CCl2H) covering ∼25% of the silicon surface sites. A significant fraction of the remaining Si-H bonds on the surface was converted to Si-Cl/Br groups during the same reaction, with PhHgCCl2Br serving as a halogen atom source. The presence of two distinct environments for the chlorine atoms (Si-CCl2H and Si-Cl) and one type of bromine atom (Si-Br) was confirmed by Cl 2p, Br 3d, and C 1s X-ray photoelectron spectroscopy. The formation of reactive, halogen-terminated atop silicon sites was also verified by reaction with sodium azide or the Grignard reagent (CH3MgBr), to produce Si-N3 or Si-Me functionalities, respectively. Thus, reaction of a hydrogen-terminated silicon (111) surface with PhHgCCl2Br provides a facile route to multifunctional surfaces possessing both stable silicon-carbon and labile silicon-halogen sites, in a single pot synthesis. The reactive silicon-halogen groups can be utilized for subsequent transformations and, potentially, the construction of more complex organic-silicon hybrid systems.

Redox and fungicidal properties of phthalocyanine metal complexes as related to active oxygen.

PubMed

Vol'pin, M E; Novodarova, G N; Krainova NYu; Lapikova, V P; Aver'yanov, A A

2000-10-01

Some chemical and fungicidal effects of 20 phthalocyanines of Co, Fe, Cu, and Al were studied. Under dark conditions, these complexes reduced nitroblue tetrazolium in the presence of KCN, accelerated the autoxidation of ascorbate or hydroquinone and decomposed hydrogen peroxide. In the later reaction, hydroxyl radical was generated as evidenced with the deoxyribose assay. The inhibition by superoxide dismutase and catalase of catalyzed autoxidation of ascorbate suggests the participation of superoxide anion-radical and hydrogen peroxide in the reaction. Most complexes were toxic to the fungus Magnaporthe grisea which causes blast disease of rice. The toxicity was enhanced by light being diminished by antioxidant reagents sequestering active oxygen species. Some complexes (including nontoxic ones), after 1-day contact with a leaf surface of the disease-susceptible rice cultivar, induced the fungitoxicity of leaf diffusate. This toxicity was also light-activated and sensitive to antioxidant reagents. Several complexes, when added to inocula, decreased 2-3 times the frequency of the compatible symptoms of the blast. It is suggested that in planta, the dark redox activity of phthalocyanines along with their photosensitization promote the generation of active oxygen, which damages the parasite and, therefore, favors disease resistance.

Crystal structures and DFT calculations of mixed chloride-azide zinc(II) and chloride-isocyanate cadmium(II) complexes with the condensation product of 2-quinolinecarboxaldehyde and Girard's T reagent

NASA Astrophysics Data System (ADS)

Anđelković, Katarina; Pevec, Andrej; Grubišić, Sonja; Turel, Iztok; Čobeljić, Božidar; Milenković, Milica R.; Keškić, Tanja; Radanović, Dušanka

2018-06-01

The mixed chloride-azide [ZnL(N3)1.65Cl0.35] (1) and chloride-isocyanate [CdL(NCO)1.64Cl0.36] (2) complexes with the condensation product of 2-quinolinecarboxaldehyde and trimethylammonium acetohydrazide chloride (Girard's T reagent) (HLCl) have been prepared and characterized by X-ray crystallography. In complexes 1 and 2, Zn1 and Cd1 ions, respectively, are five-coordinated in a distorted square based pyramidal geometry with NNO set of donor atoms of deprotonated hydrazone ligand and two monodentate ligands N3- and/or N3- and Cl- in the case of 1 and OCN- and/or OCN- and Cl- in the case of 2. The structural parameters of 1 and 2 have been discussed in relation to those of previously reported M(II) complexes with the same hydrazone ligand. Density functional theory calculations have been employed to study the interaction between the Zn2+ and Cd2+ ions and ligands. High affinity of ligands towards the Zn2+ and Cd2+ ions are predicted for both complexes.

2-Pyridylfuran: a new fluorescent tag for the analysis of carbohydrates.

PubMed

Cai, Zhi Peng; Hagan, Andrew Kevin; Wang, Mao Mao; Flitsch, Sabine Lahja; Liu, Li; Voglmeir, Josef

2014-05-20

We herein report the use of 1,3-di(2-pyridyl)-1,3-propanedione (DPPD) as a fluorogenic labeling reagent for sugars. Reaction of DPPD with the anomeric carbon affords a fluorescent 2-pyridylfuran (2-PF) moiety that permits the sensitive HPLC-based detection of monosaccharides. 2-PF-labeled monosaccharides can be easily separated and analyzed from mixtures thereof, and the reported protocol compares favorably with established labeling reagents such as 2-aminobenzoic acid (2-AA) and 1-phenyl-3-methyl-5-pyrazolone (PMP), ultimately allowing subfemtomole detection of the galactose-derived product. Furthermore, we demonstrate the application of DPPD in the labeling of monosaccharides in complex biological matrices such as blood and milk samples. We envisage that DPPD will prove to be an excellent choice of labeling reagent in monosaccharide and carbohydrate analysis.

Two-dimensional parallel array technology as a new approach to automated combinatorial solid-phase organic synthesis

PubMed

Brennan; Biddison; Frauendorf; Schwarcz; Keen; Ecker; Davis; Tinder; Swayze

1998-01-01

An automated, 96-well parallel array synthesizer for solid-phase organic synthesis has been designed and constructed. The instrument employs a unique reagent array delivery format, in which each reagent utilized has a dedicated plumbing system. An inert atmosphere is maintained during all phases of a synthesis, and temperature can be controlled via a thermal transfer plate which holds the injection molded reaction block. The reaction plate assembly slides in the X-axis direction, while eight nozzle blocks holding the reagent lines slide in the Y-axis direction, allowing for the extremely rapid delivery of any of 64 reagents to 96 wells. In addition, there are six banks of fixed nozzle blocks, which deliver the same reagent or solvent to eight wells at once, for a total of 72 possible reagents. The instrument is controlled by software which allows the straightforward programming of the synthesis of a larger number of compounds. This is accomplished by supplying a general synthetic procedure in the form of a command file, which calls upon certain reagents to be added to specific wells via lookup in a sequence file. The bottle position, flow rate, and concentration of each reagent is stored in a separate reagent table file. To demonstrate the utility of the parallel array synthesizer, a small combinatorial library of hydroxamic acids was prepared in high throughput mode for biological screening. Approximately 1300 compounds were prepared on a 10 μmole scale (3-5 mg) in a few weeks. The resulting crude compounds were generally >80% pure, and were utilized directly for high throughput screening in antibacterial assays. Several active wells were found, and the activity was verified by solution-phase synthesis of analytically pure material, indicating that the system described herein is an efficient means for the parallel synthesis of compounds for lead discovery. Copyright 1998 John Wiley & Sons, Inc.

Photomodulation of the nucleating activity of a photocleavable crosslinked actin dimer.

PubMed

Marriott, G; Miyata, H; Kinosita, K

1992-04-01

The ability to generate substrate concentration jumps through photo-deprotection of amine, carboxyl and phosphate groups has been an important development for investigations of protein activity in complex systems. To broaden the versatility and applications of photo-deprotection techniques for the photomodulation of protein activity we describe the synthesis and characterisation of a reagent for generating free thiol from thioether groups and a related photocleavable, heterobifunctional crosslinking reagent. Chemical and spectroscopic studies of a model thiol protected derivative were used to show some features of thiol group photodeprotection. To demonstrate how the photocleavable crosslinking reagent may be used to modulate the activity of proteins we investigated the effect of light on the nucleating activity of crosslinked actin dimer; thus following near-ultraviolet irradiation of the actin dimer the crosslink was cleaved, presumeably at the thioether bond, resulting in the concomitant dissociation of dimer, loss of nucleating activity and creation of a concentration jump of polymerisable G-actin monomer. On the basis of this initial study we discuss applications and limitations of these reagents for the photomodulation of protein activity in vitro and in vivo.

[Feasibility of washing as a remediation technology for the heavy metals-polluted soils left by chemical plant].

PubMed

Liu, Lei; Hu, Shao-Ping; Chen, Ying-Xu; Li, Hang

2010-06-01

Laboratory simulation tests were conducted to examine the effects of different washing reagents (distilled water, HCl, H3PO4, oxalic acid, and CaCl2) in extracting the heavy metals from contaminated soils left by a chemical plant. The effects of reagent concentration, reaction time, and washing time on the washing efficiency were investigated, and the form variation of test heavy metals was determined before and after HCl washing. Distilled water, H3PO4, and CaCl2 could remove less than 1% of most heavy metals, and the highest removal rate was only 3.58%; while 2 mol HCl x L(-1) could obtain the highest washing efficiency under the optimal conditions, i. e., soil:liquid ratio was 1:3, reaction time was 1 hour, and the soils were washed twice by HCl solution. The removal rates of Cr, Pb, Zn, Cu, and Cd from test soils were 80.75%, 88.69%, 98.00%, 79.33%, and 95.52%, respectively. Among the washing reagents, HCl could effectively remove all forms of heavy metals.

Late-stage chemoselective functional-group manipulation of bioactive natural products with super-electrophilic silylium ions

NASA Astrophysics Data System (ADS)

Bender, Trandon A.; Payne, Philippa R.; Gagné, Michel R.

2018-01-01

The selective (and controllable) modification of complex molecules with disparate functional groups (for example, natural products) is a long-standing challenge that has been addressed using catalysts tuned to perform singular transformations (for example, C-H hydroxylation). A method whereby reactions with diverse functional groups within a single natural product are feasible depending on which catalyst or reagent is chosen would widen the possible structures one could obtain. Fluoroarylborane catalysts can heterolytically split Si-H bonds to yield an oxophilic silylium (R3Si+) equivalent along with a reducing (H-) equivalent. Together, these reactive intermediates enable the reduction of multiple functional groups. Exogenous phosphine Lewis bases further modify the catalyst speciation and attenuate aggressive silylium ions for the selective modification of complex natural products. Manipulation of the catalyst, silane reagent and the reaction conditions provides experimental control over which site is modified (and how). Applying this catalytic method to complex bioactive compounds (natural products or drugs) provides a powerful tool for studying structure-activity relationships.

Dewaterability of five sewage sludges in Guangzhou conditioned with Fenton's reagent/lime and pilot-scale experiments using ultrahigh pressure filtration system.

PubMed

Liang, Jialin; Huang, Shaosong; Dai, Yongkang; Li, Lei; Sun, Shuiyu

2015-11-01

Sludge conditioning with Fenton's reagent and lime is a valid method for sludge dewatering. This study investigated the influence of different organic matter content sludge on sludge dewatering and discussed the main mechanism of sludge conditioning by combined Fenton's reagent and lime. The results indicated that the specific resistance to filterability (SRF) of sludge was reduced efficiently by approximately 90%, when conditioned with Fenton's reagent and lime. Through single factor experiments, the optimal conditioning combinations were found. In addition, the relationship between VSS% and consumption of the reagents was detected. Furthermore, it was also demonstrated that the SRF and filtrate TOC values had a significant correlation with VSS% of sludge (including raw and conditioned). The main mechanism of sludge dewatering was also investigated. Firstly, it revealed that the dewaterability of sludge was closely correlated to extracellular polymeric substances (EPS) and bound water contents. Secondly, the results of scanning electron microscopy (SEM) stated that sludge particles were to be smaller and thinner after conditioning. And this structure could easily form outflow channels for releasing free water. Additionally, with the ultrahigh pressure filtration system, the water content of sludge cake conditioned with Fenton's reagent and lime could be reduced to below 50%. Moreover, the economic assessment shows that Fenton's reagent and lime combined with ultrahigh pressure filtration system can be an economical and viable technology for sewage sludge dewatering. Finally, three types of sludge were classified: (1) Fast to dewater; (2) Moderately fast to dewater; (3) Slow to dewater sludge. Copyright © 2015 Elsevier Ltd. All rights reserved.

New Supercharging Reagents Produce Highly Charged Protein Ions in Native Mass Spectrometry

PubMed Central

Going, Catherine C.; Xia, Zijie; Williams, Evan R.

2015-01-01

The effectiveness of two new supercharging reagents for producing highly charged ions by electrospray ionization (ESI) from aqueous solutions in which proteins have native structures and reactivities were investigated. In aqueous solution, 2-thiophenone and 4-hydroxymethyl-1,3-dioxolan-2-one (HD) at a concentration of 2% by volume can increase the average charge of cytochrome c and myoglobin by up to 163%, resulting in even higher charge states than those that are produced from water/methanol/acid solutions in which proteins are denatured. The greatest extent of supercharging occurs in pure water, but these supercharging reagents are also highly effective in aqueous solutions containing 200 mM ammonium acetate buffer commonly used in native mass spectrometry (MS). These reagents are less effective supercharging reagents than m-nitrobenzyl alcohol (m-NBA) and propylene carbonate (PC) when ions are formed from water/methanol/acid. The extent to which loss of the heme group from myoglobin occurs is related to the extent of supercharging. Results from guanidine melts of cytochrome c monitored with tryptophan fluorescence show that the supercharging reagents PC, sulfolane and HD are effective chemical denaturants in solution. These results provide additional evidence for the role of protein structural changes in the electrospray droplet as the primary mechanism for supercharging with these reagents in native MS. These results also demonstrate that for at least some proteins, the formation of highly charged ions from native MS is no longer a significant barrier for obtaining structural information using conventional tandem MS methods. PMID:26421324

The Effect of Citric Acid on the Oxidation of Organic Contaminants by Fenton's Reagent

NASA Astrophysics Data System (ADS)

Seol, Y.; Javandel, I.; Lee, G.

2003-12-01

Combined with acids and iron catalysts, hydrogen peroxide (H2O2) as Fenton's reagent is proven to be effective in oxidizing halogenated volatile organic compounds (VOCs). The Fenton's reagent, traditionally used for waste water treatment technique, has been applied to the remediation of contaminated soil systems and numerous investigators have found intrinsic iron salts are effective source of iron catalyst for the reaction. Citric acid, which is naturally occurring nutrients to microorganisms and less destructive to soil chemical properties, is selected for an acidifying agent to create acidic soil condition. However, citric acid has been considered as a reaction inhibitant because it sequesters ferric iron from Fenton's catalytic cycle by forming strong chelates with iron. This paper presents the feasibility of using citric acid as an acidifying agent of soil matrix for the Fenton-like oxidation. Series of batch tests were performed to test disappearance of VOCs in various aqueous systems with two acidifying agents (citric acid or sulfuric acid) and three iron sources (iron sulfate, water soluble soil iron, or soil matrix). Batch results show that soluble iron is essential for near complete disappearance of VOCs and that citric acid performs similarly to sulfuric acid at low H2O2 dosage (< 1 wt%). The test soil provided water-soluble soil iron but also contained scavengers of the oxidizing agents, resulting in limited removals of VOCs. Column tests confirmed the results of the batch tests, suggesting citric acid is also as effective as sulfuric acid in providing acidic environment for the Fenton-like oxidation. The batch experiments also reveal that higher doses of H2O2 lower the degree of VOC removals in citric acid systems. Potential explanations for this declining include that excessive presence of H2O2 expedites the oxidation of ferrous to ferric iron, which then forms a strong complex with citrate, leading to the sequestration of the iron from the Fenton's reaction cycle. Consequently, additional supply of ferrous iron would be required for continuing oxidation of VOCs, as well as slow injection of H2O2. Detailed mechanistic study would be needed for factual understanding.

Parallel synthesis of ureas and carbamates from amines and CO2 under mild conditions.

PubMed

Peterson, Scott L; Stucka, Sabrina M; Dinsmore, Christopher J

2010-03-19

A mild and efficient library synthesis technique has been developed for the synthesis of ureas and carbamates from carbamic acids derived from the DBU-catalyzed reaction of amines and gaseous carbon dioxide. Carbamic acids derived from primary amines reacted with Mitsunobu reagents to generate isocyanates in situ which were condensed with primary and secondary amines to afford the desired ureas. Similarly, carbamic acids from secondary amines reacted with alcohols activated with Mitsunobu reagents to form carbamates.

Diastereoselective Additions of Allylmetal Reagents to Free and Protected syn-α,β-Dihydroxyketones Enable Efficient Synthetic Routes to Methyl Trioxacarcinoside A

PubMed Central

Smaltz, Daniel J.; Švenda, Jakub

2012-01-01

Two routes to the 2,6-dideoxysugar methyl trioxacarcinoside A are described. Each was enabled by an apparent α-chelation-controlled addition of an allylmetal reagent to a ketone substrate containing a free α-hydroxyl group and a β-hydroxyl substituent, either free or protected as the corresponding di-tert-butylmethyl silyl ether. Both routes provide practical access to gram-quantities of trioxacarcinose A in a form suitable for glycosidic coupling reactions. PMID:22404560

Factors affecting nucleolytic efficiency of some ternary metal complexes with DNA binding and recognition domains. Crystal and molecular structure of Zn(phen)(edda).

PubMed

Seng, Hoi-Ling; Ong, Han-Kiat Alan; Rahman, Raja Noor Zaliha Raja Abd; Yamin, Bohari M; Tiekink, Edward R T; Tan, Kong Wai; Maah, Mohd Jamil; Caracelli, Ignez; Ng, Chew Hee

2008-11-01

The binding selectivity of the M(phen)(edda) (M=Cu, Co, Ni, Zn; phen=1,10-phenanthroline, edda=ethylenediaminediacetic acid) complexes towards ds(CG)(6), ds(AT)(6) and ds(CGCGAATTCGCG) B-form oligonucleotide duplexes were studied by CD spectroscopy and molecular modeling. The binding mode is intercalation and there is selectivity towards AT-sequence and stacking preference for A/A parallel or diagonal adjacent base steps in their intercalation. The nucleolytic properties of these complexes were investigated and the factors affecting the extent of cleavage were determined to be: concentration of complex, the nature of metal(II) ion, type of buffer, pH of buffer, incubation time, incubation temperature, and the presence of hydrogen peroxide or ascorbic acid as exogenous reagents. The fluorescence property of these complexes and its origin were also investigated. The crystal structure of the Zn(phen)(edda) complex is reported in which the zinc atom displays a distorted trans-N(4)O(2) octahedral geometry; the crystal packing features double layers of complex molecules held together by extensive hydrogen bonding that inter-digitate with adjacent double layers via pi...pi interactions between 1,10-phenanthroline residues. The structure is compared with that of the recently described copper(II) analogue and, with the latter, included in molecular modeling.

Method of detecting genetic translocations identified with chromosomal abnormalities

DOEpatents

Gray, Joe W.; Pinkel, Daniel; Tkachuk, Douglas

2001-01-01

Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML) and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Chromosome-specific staining to detect genetic rearrangements

DOEpatents

Gray, Joe W.; Pinkel, Daniel; Tkachuk, Douglas; Westbrook, Carol

2013-04-09

Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyzes. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML) and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Method of detecting genetic deletions identified with chromosomal abnormalities

DOEpatents

Gray, Joe W; Pinkel, Daniel; Tkachuk, Douglas

2013-11-26

Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyzes. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acids probes are typically of a complexity greater tha 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particlularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML) and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar ut genetically different diseases, and for many prognostic and diagnostic applications.

Effects of ancillary ligands on selectivity of protein labeling with platinum(II) chloro complexes

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

Zhou, Xia-Ying.

1990-02-01

Potassium (2,6-pyridinedicarboxylato)chloroplatinate(II) was synthesized. The molecular structure of the complex in (n-Bu){sub 4}N(Pt(dipic)Cl){center dot}0.5H{sub 2}O was determined by x-ray crystallography. The (Pt(dipic)Cl){sup {minus}} is essentially planar and contains a Pt(II) atom, a tridentate dipicolinate dianion ligand, and a unidentate Cl{sup {minus}} ligand. The bis(bidentate) complex trans-(Pt(dipic){sub 2}){sup 2{minus}} was also observed by {sup 1}H NMR. A red gel-like substance was observed when the yellow aqueous solution of K(Pt(dipic)Cl) was cooled or concentrated. The K(Pt(dipic)Cl) molecules form stacks in the solid state and gel-like substance but remain monomeric over a wide range of concentrations and temperatures. The reactivity and selectivity of(Pt(dipic)Cl){supmore » {minus}} toward cytochromes c from horse and tuna were studied. The new transition-metal reagent is specific for methionine residues. Di(2-pyridyl-{beta}-ethyl)sulfidochloroplatinum(II) chloride dihydrate was also synthesized. This complex labels histidine and methionine residues in cytochrome c. The ancillary ligands in these platinum(II) complexes clearly determine the selectivity of protein labeling. 106 refs., 10 figs., 11 tabs.« less

Peptide Fragmentation by Corona Discharge Induced Electrochemical Ionization

PubMed Central

Lloyd, John R.; Hess, Sonja

2010-01-01

Fundamental studies have greatly improved our understanding of electrospray, including the underlying electrochemical reactions. Generally regarded as disadvantageous, we have recently shown that corona discharge (CD) can be used as an effective method to create a radical cation species [M]+•, thus optimizing the electrochemical reactions that occur on the surface of the stainless steel (SS) electrospray capillary tip. This technique is known as CD initiated electrochemical ionization (CD-ECI). Here, we report on the fundamental studies using CD-ECI to induce analytically useful in-source fragmentation of a range of molecules that complex transition metals. Compounds that have been selectively fragmented using CD-ECI include enolate forming phenylglycine containing peptides, glycopeptides, nucleosides and phosphopeptides. Collision induced dissociation (CID) or other activation techniques were not necessary for CD-ECI fragmentation. A four step mechanism was proposed: 1. Complexation using either Fe in the SS capillary tip material or Cu(II) as an offline complexation reagent; 2. Electrochemical oxidation of the complexed metal and thus formation of a radical cation (e.g.; Fe - e− → Fe +•); 3. Radical fragmentation of the complexed compound. 4. Electrospray ionization of the fragmented neutrals. Fragmentation patterns resembling b- and y-type ions were observed and allowed the localization of the phosphorylation sites. PMID:20869880

Structural Characterization by Cross-linking Reveals the Detailed Architecture of a Coatomer-related Heptameric Module from the Nuclear Pore Complex*

PubMed Central

Shi, Yi; Fernandez-Martinez, Javier; Tjioe, Elina; Pellarin, Riccardo; Kim, Seung Joong; Williams, Rosemary; Schneidman-Duhovny, Dina; Sali, Andrej; Rout, Michael P.; Chait, Brian T.

2014-01-01

Most cellular processes are orchestrated by macromolecular complexes. However, structural elucidation of these endogenous complexes can be challenging because they frequently contain large numbers of proteins, are compositionally and morphologically heterogeneous, can be dynamic, and are often of low abundance in the cell. Here, we present a strategy for the structural characterization of such complexes that has at its center chemical cross-linking with mass spectrometric readout. In this strategy, we isolate the endogenous complexes using a highly optimized sample preparation protocol and generate a comprehensive, high-quality cross-linking dataset using two complementary cross-linking reagents. We then determine the structure of the complex using a refined integrative method that combines the cross-linking data with information generated from other sources, including electron microscopy, X-ray crystallography, and comparative protein structure modeling. We applied this integrative strategy to determine the structure of the native Nup84 complex, a stable hetero-heptameric assembly (∼600 kDa), 16 copies of which form the outer rings of the 50-MDa nuclear pore complex (NPC) in budding yeast. The unprecedented detail of the Nup84 complex structure reveals previously unseen features in its pentameric structural hub and provides information on the conformational flexibility of the assembly. These additional details further support and augment the protocoatomer hypothesis, which proposes an evolutionary relationship between vesicle coating complexes and the NPC, and indicates a conserved mechanism by which the NPC is anchored in the nuclear envelope. PMID:25161197

Modifying effects of carboxyl group on the interaction of recombinant S100A8/A9 complex with tyrosinase.

PubMed

NematiNiko, Fatemeh; Chegini, Koorosh Goodarzvand; Asghari, Hamideh; Amini, Abbas; Gheibi, Nematollah

2017-03-01

Tyrosinase is a determinant enzyme for modulating melanin production as its abnormal activity can result in an increased amount of melanin. Reduction of tyrosinase activity has been targeted for preventing and healing hyperpigmentation of skin, such as melanoma and age related spots. The aim of this systematic study is to investigate whether recombinant S100A8/A9 and its modified form reduce the activity of mushroom tyrosinase (MT) through changing its structure. Recombinant His-Tagged S100A8 and S100A9 are expressed in Escherichia coli BL21 (DE3) and modified using Woodward's reagent K which is a carboxyl group modifier. The structures of S100A8/A9 and its modified form are studied using fluorescence and circular dichroism spectroscopy, and the activity of MT is measured using UV-visible spectrophotometry in the presence of its substrate, L-3,4-dihydroxyphenylalanine (L-DOPA). The results show a lower stability of the modified protein when compared with its unmodified form. The interaction of S100A8/A9 with MT changes the structure and successfully reduces the activity of mushroom tyrosinase. Recombinant S100A8/A9 complex decreases MT activity which can control malignant melanoma, the most dangerous type of skin cancer. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectrophotometric Determination of Rifampicin in Bulk Drug and Pharmaceutical Formulations Based on Redox and Complexation Reactions

NASA Astrophysics Data System (ADS)

Swamy, N.; Basavaiah, K.

2017-09-01

Two spectrophotometric methods were developed and validated for the determination of rifampicin (RIF) in bulk form, formulations, and spiked human urine. The first method is based on the reduction of the Folin-Ciocalteu (FC) reagent by RIF to form a blue colored chromogen with λmax at 760 nm (the FCR method). In the second method, iron(III) is reduced by RIF in a neutral medium, and the resulting iron(II) is complexed with ferricyanide to form a Prussian blue peaking at 750 nm (the FFC method). Under optimum conditions, Beer's law enabled the determination of the drug in the concentration ranges 1-35 and 2.5-50 μg/mL with apparent molar absorptivities of 2.72 × 104 and 1.63×104 L/(mol × cm) for the FCR and FFC methods, respectively. The Sandell sensitivity, limits of detection (LOD), and quantification (LOQ) values were also reported for both methods. The precision of the methods, with % RSD of < 2%, was satisfactory, and the accuracy was higher than 2% (RE). The proposed methods were successfully applied to the determination of drug in capsules without interference from common additives and spiked human urine without interference from endogenous substances. A statistical analysis indicated that there was no significant difference between the results obtained by the developed methods and the official method.

Paper-based Platform for Urinary Creatinine Detection.

PubMed

Sittiwong, Jarinya; Unob, Fuangfa

2016-01-01

A new paper platform was developed for the colorimetric detection of creatinine. The filter paper was coated with 3-propylsulfonic acid trimethoxysilane and used as the platform. Creatinine in a cationic form was extracted onto the paper via an ion-exchange mechanism and detected through the Jaffé reaction, resulting in a yellow-orange color complex. The color change on the paper could be observed visually, and the quantitative detection of creatinine was achieved through monitoring the color intensity change. The color intensity of creatinine complexes on the paper platform as a function of the creatinine concentration provided a linear range for creatinine detection in the range of 10 - 60 mg L(-1) and a detection limit of 4.2 mg L(-1). The accuracy of the proposed paper-based method was comparable to the conventional standard Jaffé method. This paper platform could be applied for simple and rapid detection of creatinine in human urine samples with a low consumption of reagent.

Multi-electron oxygen reduction by a hybrid visible-light-photocatalyst consisting of metal-oxide semiconductor and self-assembled biomimetic complex.

PubMed

Naya, Shin-ichi; Niwa, Tadahiro; Negishi, Ryo; Kobayashi, Hisayoshi; Tada, Hiroaki

2014-12-08

Adsorption experiments and density functional theory (DFT) simulations indicated that Cu(acac)2 is chemisorbed on the monoclinic sheelite (ms)-BiVO4 surface to form an O2-bridged binuclear complex (OBBC/BiVO4) like hemocyanin. Multi-electron reduction of O2 is induced by the visible-light irradiation of the OBBC/BiVO4 in the same manner as a blue Cu enzyme. The drastic enhancement of the O2 reduction renders ms-BiVO4 to work as a good visible-light photocatalyst without any sacrificial reagents. As a model reaction, we show that this biomimetic hybrid photocatalyst exhibits a high level of activity for the aerobic oxidation of amines to aldehydes in aqueous solution and imines in THF solution at 25 °C giving selectivities above 99% under visible-light irradiation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of platinum nanowire networks using a soft template.

PubMed

Song, Yujiang; Garcia, Robert M; Dorin, Rachel M; Wang, Haorong; Qiu, Yan; Coker, Eric N; Steen, William A; Miller, James E; Shelnutt, John A

2007-12-01

Platinum nanowire networks have been synthesized by chemical reduction of a platinum complex using sodium borohydride in the presence of a soft template formed by cetyltrimethylammonium bromide in a two-phase water-chloroform system. The interconnected polycrystalline nanowires possess the highest surface area (53 +/- 1 m2/g) and electroactive surface area (32.4 +/- 3.6 m2/g) reported for unsupported platinum nanomaterials; the high surface area results from the small average diameter of the nanowires (2.2 nm) and the 2-10 nm pores determined by nitrogen adsorption measurements. Synthetic control over the network was achieved simply by varying the stirring rate and reagent concentrations, in some cases leading to other types of nanostructures including wormlike platinum nanoparticles. Similarly, substitution of a palladium complex for platinum gives palladium nanowire networks. A mechanism of formation of the metal nanowire networks is proposed based on confined metal growth within a soft template consisting of a network of swollen inverse wormlike micelles.

A review of the fundamental studies of the copper activation mechanisms for selective flotation of the sulfide minerals, sphalerite and pyrite.

PubMed

Chandra, A P; Gerson, A R

2009-01-30

A review of the considerable, but often contradictory, literature examining the specific surface reactions associated with copper adsorption onto the common metal sulfide minerals sphalerite, (Zn,Fe)S, and pyrite (FeS(2)), and the effect of the co-location of the two minerals is presented. Copper "activation", involving the surface adsorption of copper species from solution onto mineral surfaces to activate the surface for hydrophobic collector attachment, is an important step in the flotation and separation of minerals in an ore. Due to the complexity of metal sulfide mineral containing systems this activation process and the emergence of activation products on the mineral surfaces are not fully understood for most sulfide minerals even after decades of research. Factors such as copper concentration, activation time, pH, surface charge, extent of pre-oxidation, water and surface contaminants, pulp potential and galvanic interactions are important factors affecting copper activation of sphalerite and pyrite. A high pH, the correct reagent concentration and activation time and a short time delay between reagent additions is favourable for separation of sphalerite from pyrite. Sufficient oxidation potential is also needed (through O(2) conditioning) to maintain effective galvanic interactions between sphalerite and pyrite. This ensures pyrite is sufficiently depressed while sphalerite floats. Good water quality with low concentrations of contaminant ions, such as Pb(2+)and Fe(2+), is also needed to limit inadvertent activation and flotation of pyrite into zinc concentrates. Selectivity can further be increased and reagent use minimised by opting for inert grinding and by carefully choosing selective pyrite depressants such as sulfoxy or cyanide reagents. Studies that approximate plant conditions are essential for the development of better separation techniques and methodologies. Improved experimental approaches and surface sensitive techniques with high spatial resolution are needed to precisely verify surface structures formed after copper activation. Sphalerite and pyrite surfaces are characterised by varying amounts of steps and defects, and this heterogeneity suggests co-existence of more than one copper-sulfide structure after activation.

A bioluminescent caspase-1 activity assay rapidly monitors inflammasome activation in cells.

PubMed

O'Brien, Martha; Moehring, Danielle; Muñoz-Planillo, Raúl; Núñez, Gabriel; Callaway, Justin; Ting, Jenny; Scurria, Mike; Ugo, Tim; Bernad, Laurent; Cali, James; Lazar, Dan

2017-08-01

Inflammasomes are protein complexes induced by diverse inflammatory stimuli that activate caspase-1, resulting in the processing and release of cytokines, IL-1β and IL-18, and pyroptosis, an immunogenic form of cell death. To provide a homogeneous method for detecting caspase-1 activity, we developed a bioluminescent, plate-based assay that combines a substrate, Z-WEHD-aminoluciferin, with a thermostable luciferase in an optimized lytic reagent added directly to cultured cells. Assay specificity for caspase-1 is conferred by inclusion of a proteasome inhibitor in the lytic reagent and by use of a caspase-1 inhibitor to confirm activity. This approach enables a specific and rapid determination of caspase-1 activation. Caspase-1 activity is stable in the reagent thereby providing assay convenience and flexibility. Using this assay system, caspase-1 activation has been determined in THP-1 cells following treatment with α-hemolysin, LPS, nigericin, gramicidin, MSU, R848, Pam3CSK4, and flagellin. Caspase-1 activation has also been demonstrated in treated J774A.1 mouse macrophages, bone marrow-derived macrophages (BMDMs) from mice, as well as in human primary monocytes. Caspase-1 activity was not detected in treated BMDMs derived from Casp1 -/- mice, further confirming the specificity of the assay. Caspase-1 activity can be measured directly in cultured cells using the lytic reagent, or caspase-1 activity released into medium can be monitored by assay of transferred supernatant. The caspase-1 assay can be multiplexed with other assays to monitor additional parameters from the same cells, such as IL-1β release or cell death. The caspase-1 assay in combination with a sensitive real-time monitor of cell death allows one to accurately establish pyroptosis. This assay system provides a rapid, convenient, and flexible method to specifically and quantitatively monitor caspase-1 activation in cells in a plate-based format. This will allow a more efficient and effective assessment of inflammasome activation as well as enable high-throughput screening for inflammasome modulators. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Construction of a microfluidic chip, using dried-down reagents, for LATE-PCR amplification and detection of single-stranded DNA.

PubMed

Jia, Yanwei; Mak, Pui-In; Massey, Conner; Martins, Rui P; Wangh, Lawrence J

2013-12-07

LATE-PCR is an advanced form of non-symmetric PCR that efficiently generates single-stranded DNA which can readily be characterized at the end of amplification by hybridization to low-temperature fluorescent probes. We demonstrate here for the first time that monoplex and duplex LATE-PCR amplification and probe target hybridization can be carried out in double layered PDMS microfluidics chips containing dried reagents. Addition of a set of reagents during dry down overcomes the common problem of single-stranded oligonucleotide binding to PDMS. These proof-of-principle results open the way to construction of inexpensive point-of-care devices that take full advantage of the analytical power of assays built using LATE-PCR and low-temperature probes.

Magnesium, zinc, aluminium and gallium hydride complexes of the transition metals.

PubMed

Butler, Michael J; Crimmin, Mark R

2017-01-24

The preparation and applications of heterobimetallic complexes continue to occupy researchers in the fields of organometallic, main group, and coordination chemistry. This interest stems from the promise these complexes hold as precursors to materials, reagents in synthesis and as new catalysis. Here we survey and organise the state-of-the-art understanding of the TM-H-M linkage (M = Mg, Zn, Al, Ga). We discuss the structure and bonding in these complexes, their known reactivity, and their largely unrealised potential in catalysis.

Ultrasound promoted N-alkylation of pyrrole using potassium superoxide as base in crown ether.

PubMed

Yim, E S; Park, M K; Han, B H

1997-04-01

Ultrasound accelerates the N-alkylation of pyrrole by alkylating reagents using potassium superoxide as base in the presence of 18-crown-6. A much lower yield of N-alkylated pyrrole was realized in the absence of ultrasound. N-alkylating reagents employed for pyrrole are methyl iodide, ethyl bromide, benzyl bromide, as well as acrylonitrile allyl cyanide and methyl acrylate. In an extension of this work, we have found that ultrasound was not necessary for the N-alkylation of indole and alkyl amine, such as diphenyl amine and piperidine with alkyl halides using our reagents. In all cases we observed that the 18-crown-6 catalyzed N-alkylation reaction gives higher yields of N-alkylated products than that without crown ether, when potassium superoxide was used as base. These observations are probably due to the potassium-crown complex which can be released when the reaction goes to completion.

Asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with a new trifluoromethoxylation reagent

NASA Astrophysics Data System (ADS)

Guo, Shuo; Cong, Fei; Guo, Rui; Wang, Liang; Tang, Pingping

2017-06-01

Fluorinated organic compounds are becoming increasingly important in pharmaceuticals, agrochemicals and materials science. The introduction of trifluoromethoxy groups into new drugs and agrochemicals has attracted much attention due to their strongly electron-withdrawing nature and high lipophilicity. However, synthesis of trifluoromethoxylated organic molecules is difficult owing to the decomposition of trifluoromethoxide anion and β-fluoride elimination from transition-metal-trifluoromethoxide complexes, and no catalytic enantioselective trifluoromethoxylation reaction has been reported until now. Here, we present an example of an asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with trifluoromethyl arylsulfonate (TFMS) as a new trifluoromethoxylation reagent. Compared to other trifluoromethoxylation reagents, TFMS is easily prepared and thermally stable with good reactivity. In addition, this reaction is operationally simple, scalable and proceeds under mild reaction conditions. Furthermore, broad scope and good functional group compatibility has been demonstrated by application of the method to the bromotrifluoromethoxylation of double bonds in natural products and natural product derivatives.

Ultrasonic evidence of hydrophobic interactions. Effect of ultrasound on benzoin condensation and some other reactions in aqueous ethanol.

PubMed

Tuulmets, Ants; Hagu, Hannes; Salmar, Siim; Cravotto, Giancarlo; Järv, Jaak

2007-03-29

The kinetics of KCN-catalyzed benzoin condensation of benzaldehyde in water and ethanol-water binary mixtures was investigated both under ultrasound at 22 kHz and without sonication. Thermodynamic activation parameters were calculated from kinetic data obtained at 35, 50, and 65 degrees C. Evidence that ultrasound can retard reactions is reported and hence a direct proof that sonochemical processes occur in the bulk solution. Former results and literature data for ester hydrolyses and tert-butyl chloride solvolysis are involved in the discussion. A quantitative relationship between sonication effects and the hydrophobicity of reagents is presented for the first time. Ultrasound affects hydrophobic interactions with the solvent, which are not manifested in conventional kinetics. When it suppresses the stabilization of the encounter complexes between reagents, sonication hinders the reaction but accelerates it when it perturbs the hydrophobic stabilization of the ground state of a reagent.

Literally Green Chemical Synthesis of Artemisinin from Plant Extracts.

PubMed

Triemer, Susann; Gilmore, Kerry; Vu, Giang T; Seeberger, Peter H; Seidel-Morgenstern, Andreas

2018-05-04

Active pharmaceutical ingredients are either extracted from biological sources-where they are synthesized in complex, dynamic environments-or prepared in stepwise chemical syntheses by reacting pure reagents and catalysts under controlled conditions. A combination of these two approaches, where plant extracts containing reagents and catalysts are utilized in intensified chemical syntheses, creates expedient and sustainable processes. We illustrate this principle by reacting crude plant extract, oxygen, acid, and light to produce artemisinin, a key active pharmaceutical ingredient of the most powerful antimalarial drugs. The traditionally discarded extract of Artemisia annua plants contains dihydroartemisinic acid-the final biosynthetic precursor-as well as chlorophyll, which acts as a photosensitizer. Efficient irradiation with visible light in a continuous-flow setup produces artemisinin in high yield, and the artificial biosynthetic process outperforms syntheses with pure reagents. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[The efficiency of the enzyme immunoassay test system opisthorchiasis-CIC-EIA-best to detect circulating immune complexes containing opisthorchis antigens in the serum of patients with opisthorchiasis].

PubMed

Starkova, T V; Poletaeva, O G; Kovrova, E A; Krasovskaia, N N; Tkachenko, T N; Masiago, A V; Ofitserov, V I; Tereshchenko, A Iu

2011-01-01

The efficacy of a kit of Opisthorchiasis-CIC-EIA-Best reagents was evaluated using 270 sera from patients in the study and control groups. The kit showed a sufficient sensitivity (not less than 87.2%) and a high specificity (not less than 97.9%). The use of the above kit of the reagents for enzyme immunoassay in practical healthcare enables one to increase detection rates among the infested subjects on comprehensive examination of those with suspected opisthorchiasis.

How Chemical Synthesis of Ubiquitin Conjugates Helps To Understand Ubiquitin Signal Transduction.

PubMed

Hameed, Dharjath S; Sapmaz, Aysegul; Ovaa, Huib

2017-03-15

Ubiquitin (Ub) is a small post-translational modifier protein involved in a myriad of biochemical processes including DNA damage repair, proteasomal proteolysis, and cell cycle control. Ubiquitin signaling pathways have not been completely deciphered due to the complex nature of the enzymes involved in ubiquitin conjugation and deconjugation. Hence, probes and assay reagents are important to get a better understanding of this pathway. Recently, improvements have been made in synthesis procedures of Ub derivatives. In this perspective, we explain various research reagents available and how chemical synthesis has made an important contribution to Ub research.

Impedance Analysis of Thin Films of Organic-Inorganic Perovskites CH3NH3PbI3 with Control of Microstructure

NASA Astrophysics Data System (ADS)

V'yunov, Oleg; Belous, Anatolii; Kobylianska, Sofiia; Kovalenko, Leonid

2018-04-01

The effect of starting reagents (PbI2:{CH3NH3I + CH3NH3Cl}) with different ratios in raw solutions on the microstructure of films of organic-inorganic perovskites CH3NH3PbI3-xClx, as well as on the electrical properties, has been investigated. It was found that the crystallinity is increased sharply when the ratio of the starting reagents increases from 1:1 to 1:2 and is changed slightly with a further increase of ratio to 1:3. It is shown that when the ratio of starting reagents varies, the morphology of the films changes; at a ratio of 1:1, the films consist of needle-like particles, and when the ratio is increased, particles become roundish and then faceted. Additionally, the average grain size is decreased. Complex impedance curves and I-V curves have been investigated for samples with different ratios of the starting reagents. With increasing this ratio, the concentration of charge carriers remains unchanged, the mobility of charge carriers decreases, and conductivity passes through a maximum at a ratio of 1:2. The electrical properties of film are the highest at the ratio of starting reagents 1:2 due to the effect of two competing factors: the growth of crystallinity and the decrease of grain size.

Method of synthesis of anhydrous thorium(IV) complexes

DOEpatents

Kiplinger, Jaqueline L; Cantat, Thibault

2013-04-30

Method of producing anhydrous thorium(IV) tetrahalide complexes, utilizing Th(NO.sub.3).sub.4(H.sub.2O).sub.x, where x is at least 4, as a reagent; method of producing thorium-containing complexes utilizing ThCl.sub.4(DME).sub.2 as a precursor; method of producing purified ThCl.sub.4(ligand).sub.x compounds, where x is from 2 to 9; and novel compounds having the structures: ##STR00001##

Microplate-reader method for the rapid analysis of copper in natural waters with chemiluminescence detection.

PubMed

Durand, Axel; Chase, Zanna; Remenyi, Tomas; Quéroué, Fabien

2012-01-01

We have developed a method for the determination of copper in natural waters at nanomolar levels. The use of a microplate-reader minimizes sample processing time (~25 s per sample), reagent consumption (~120 μL per sample), and sample volume (~700 μL). Copper is detected by chemiluminescence. This technique is based on the formation of a complex between copper and 1,10-phenanthroline and the subsequent emission of light during the oxidation of the complex by hydrogen peroxide. Samples are acidified to pH 1.7 and then introduced directly into a 24-well plate. Reagents are added during data acquisition via two reagent injectors. When trace metal clean protocols are employed, the reproducibility is generally less than 7% on blanks and the detection limit is 0.7 nM for seawater and 0.4 nM for freshwater. More than 100 samples per hour can be analyzed with this technique, which is simple, robust, and amenable to at-sea analysis. Seawater samples from Storm Bay in Tasmania illustrate the utility of the method for environmental science. Indeed other trace metals for which optical detection methods exist (e.g., chemiluminescence, fluorescence, and absorbance) could be adapted to the microplate-reader.

2006 Bethesda International Consensus recommendations on the immunophenotypic analysis of hematolymphoid neoplasia by flow cytometry: optimal reagents and reporting for the flow cytometric diagnosis of hematopoietic neoplasia.

PubMed

Wood, Brent L; Arroz, Maria; Barnett, David; DiGiuseppe, Joseph; Greig, Bruce; Kussick, Steven J; Oldaker, Teri; Shenkin, Mark; Stone, Elizabeth; Wallace, Paul

2007-01-01

Immunophenotyping by flow cytometry has become standard practice in the evaluation and monitoring of patients with hematopoietic neoplasia. However, despite its widespread use, considerable variability continues to exist in the reagents used for evaluation and the format in which results are reported. As part of the 2006 Bethesda Consensus conference, a committee was formed to attempt to define a consensus set of reagents suitable for general use in the diagnosis and monitoring of hematopoietic neoplasms. The committee included laboratory professionals from private, public, and university hospitals as well as large reference laboratories that routinely operate clinical flow cytometry laboratories with an emphasis on lymphoma and leukemia immunophenotyping. A survey of participants successfully identified the cell lineage(s) to be evaluated for each of a variety of specific medical indications and defined a set of consensus reagents suitable for the initial evaluation of each cell lineage. Elements to be included in the reporting of clinical flow cytometric results for leukemia and lymphoma evaluation were also refined and are comprehensively listed. The 2006 Bethesda Consensus conference represents the first successful attempt to define a set of consensus reagents suitable for the initial evaluation of hematopoietic neoplasia. Copyright 2007 Clinical Cytometry Society.

Development of a high-throughput screening system for identification of novel reagents regulating DNA damage in human dermal fibroblasts.

PubMed

Bae, Seunghee; An, In-Sook; An, Sungkwan

2015-09-01

Ultraviolet (UV) radiation is a major inducer of skin aging and accumulated exposure to UV radiation increases DNA damage in skin cells, including dermal fibroblasts. In the present study, we developed a novel DNA repair regulating material discovery (DREAM) system for the high-throughput screening and identification of putative materials regulating DNA repair in skin cells. First, we established a modified lentivirus expressing the luciferase and hypoxanthine phosphoribosyl transferase (HPRT) genes. Then, human dermal fibroblast WS-1 cells were infected with the modified lentivirus and selected with puromycin to establish cells that stably expressed luciferase and HPRT (DREAM-F cells). The first step in the DREAM protocol was a 96-well-based screening procedure, involving the analysis of cell viability and luciferase activity after pretreatment of DREAM-F cells with reagents of interest and post-treatment with UVB radiation, and vice versa. In the second step, we validated certain effective reagents identified in the first step by analyzing the cell cycle, evaluating cell death, and performing HPRT-DNA sequencing in DREAM-F cells treated with these reagents and UVB. This DREAM system is scalable and forms a time-saving high-throughput screening system for identifying novel anti-photoaging reagents regulating DNA damage in dermal fibroblasts.

Numerical simulation of synthesis gas incineration

NASA Astrophysics Data System (ADS)

Kazakov, A. V.; Khaustov, S. A.; Tabakaev, R. B.; Belousova, Y. A.

2016-04-01

The authors have analysed the expediency of the suggested low-grade fuels application method. Thermal processing of solid raw materials in the gaseous fuel, called synthesis gas, is investigated. The technical challenges concerning the applicability of the existing gas equipment developed and extensively tested exclusively for natural gas were considered. For this purpose computer simulation of three-dimensional syngas-incinerating flame dynamics was performed by means of the ANSYS Multiphysics engineering software. The subjects of studying were: a three-dimensional aerodynamic flame structure, heat-release and temperature fields, a set of combustion properties: a flare range and the concentration distribution of burnout reagents. The obtained results were presented in the form of a time-averaged pathlines with color indexing. The obtained results can be used for qualitative and quantitative evaluation of complex multicomponent gas incineration singularities.

Lanthanide-halide based humidity indicators

DOEpatents

Beitz, James V [Hinsdale, IL; Williams, Clayton W [Chicago, IL

2008-01-01

The present invention discloses a lanthanide-halide based humidity indicator and method of producing such indicator. The color of the present invention indicates the humidity of an atmosphere to which it is exposed. For example, impregnating an adsorbent support such as silica gel with an aqueous solution of the europium-containing reagent solution described herein, and dehydrating the support to dryness forms a substance with a yellow color. When this substance is exposed to a humid atmosphere the water vapor from the air is adsorbed into the coating on the pore surface of the silica gel. As the water content of the coating increases, the visual color of the coated silica gel changes from yellow to white. The color change is due to the water combining with the lanthanide-halide complex on the pores of the gel.

Palladium-Catalyzed Asymmetric Alkylation in the Synthesis of Cyclopentanoid and Cycloheptanoid Core Structures Bearing All-Carbon Quaternary Stereocenters

PubMed Central

Hong, Allen Y.; Bennett, Nathan B.; Krout, Michael R.; Jensen, Thomas; Harned, Andrew. M.

2011-01-01

General catalytic asymmetric routes toward cyclopentanoid and cycloheptanoid core structures embedded in numerous natural products have been developed. The central stereoselective transformation in our divergent strategies is the enantioselective decarboxylative alkylation of seven-membered β-ketoesters to form α-quaternary vinylogous esters. Recognition of the unusual reactivity of β-hydroxyketones resulting from the addition of hydride or organometallic reagents enabled divergent access to γ-quaternary acylcyclopentenes through a ring contraction pathway or γ-quaternary cycloheptenones through a carbonyl transposition pathway. Synthetic applications of these compounds were explored through the preparation of mono-, bi-, and tricyclic derivatives that can serve as valuable intermediates for the total synthesis of complex natural products. This work complements our previous work with cyclohexanoid systems. PMID:22347731

3D bio-etching of a complex composite-like embryonic tissue.

PubMed

Hazar, Melis; Kim, Yong Tae; Song, Jiho; LeDuc, Philip R; Davidson, Lance A; Messner, William C

2015-08-21

Morphogenesis involves a complex series of cell signaling, migration and differentiation events that are coordinated as tissues self-assemble during embryonic development. Collective cell movements such as those that occur during morphogenesis have typically been studied in 2D with single layers of cultured cells adhering to rigid substrates such as glass or plastic. In vivo, the intricacies of the 3D microenvironment and complex 3D responses are pivotal in the formation of functional tissues. To study such processes as collective cell movements within 3D multilayered tissues, we developed a microfluidic technique capable of producing complex 3D laminar multicellular structures. We call this technique "3D tissue-etching" because it is analogous to techniques used in the microelectromechanics (MEMS) field where complex 3D structures are built by successively removing material from a monolithic solid through subtractive manufacturing. We use a custom-designed microfluidic control system to deliver a range of tissue etching reagents (detergents, chelators, proteases, etc.) to specific regions of multilayered tissues. These tissues were previously isolated by microsurgical excision from embryos of the African claw-toed frog, Xenopus laevis. The ability to shape the 3D form of multicellular tissues and to control 3D stimulation will have a high impact on tissue engineering and regeneration applications in bioengineering and medicine as well as provide significant improvements in the synthesis of highly complex 3D integrated multicellular biosystems.

Mechanochemical Synthesis of Pharmaceutical Cocrystal Suspensions via Hot Melt Extrusion: Feasibility Studies and Physicochemical Characterization.

PubMed

Li, Shu; Yu, Tao; Tian, Yiwei; McCoy, Colin P; Jones, David S; Andrews, Gavin P

2016-09-06

Engineered cocrystals offer an alternative solid drug form with tailored physicochemical properties. Interestingly, although cocrystals provide many new possibilities, they also present new challenges, particularly in regard to their design and large-scale manufacture. Current literature has primarily focused on the preparation and characterization of novel cocrystals typically containing only the drug and coformer, leaving the subsequent formulation less explored. In this paper we propose, for the first time, the use of hot melt extrusion for the mechanochemical synthesis of pharmaceutical cocrystals in the presence of a meltable binder. In this approach, we examine excipients that are amenable to hot melt extrusion, forming a suspension of cocrystal particulates embedded in a pharmaceutical matrix. Using ibuprofen and isonicotinamide as a model cocrystal reagent pair, formulations extruded with a small molecular matrix carrier (xylitol) were examined to be intimate mixtures wherein the newly formed cocrystal particulates were physically suspended in a matrix. With respect to formulations extruded using polymeric carriers (Soluplus and Eudragit EPO, respectively), however, there was no evidence within PXRD patterns of either crystalline ibuprofen or the cocrystal. Importantly, it was established in this study that an appropriate carrier for a cocrystal reagent pair during HME processing should satisfy certain criteria including limited interaction with parent reagents and cocrystal product, processing temperature sufficiently lower than the onset of cocrystal Tm, low melt viscosity, and rapid solidification upon cooling.

Magnetite solubility and phase stability in alkaline media at elevated temperatures

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

Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

Magnetite, Fe{sub 3}O{sub 4}, is the dominant oxide constituent of the indigenous corrosion layers that form on iron base alloys in high purity, high temperature water. The apparent simultaneous stability of two distinct oxidation states of iron in this metal oxide is responsible for its unique solubility behavior. The present work was undertaken to extend the experimental and theoretical bases for estimating solubilities of an iron corrosion product (Fe{sub 3}O{sub 4}/Fe(OH){sub 2}) over a broader temperature range and in the presence of complexing, pH-controlling reagents. These results indicate that a surface layer of ferrous hydroxide controls magnetite solubility behavior atmore » low temperatures in much the same manner as a surface layer of nickel(II) hydroxide was previously reported to control the low temperature solubility behavior of NiO. The importance of Fe(III) ion complexes implies not only that most previously-derived thermodynamic properties of the Fe(OH){sub 3}{sup {minus}} ion are incorrect, but that magnetite phase stability probably shifts to favor a sodium ferric hydroxyphosphate compound in alkaline sodium phosphate solutions at elevated temperatures. The test methodology involved pumping alkaline solutions of known composition through a bed of Fe{sub 3}O{sub 4} granules and analyzing the emerging solution for Fe. Two pH-controlling reagents were tested: sodium phosphate and ammonia. Equilibria for the following reactions were described in thermodynamic terms: (a) Fe(OH){sub 2}/Fe{sub 3}O{sub 4} dissolution and transformation, (b) Fe(II) and Fe(III) ion hydroxocomplex formation (hydrolysis), (c) Fe(II) ion amminocomplex formation, and (d) Fe(II) and Fe(III) ion phosphatocomplex formation. 36 refs.« less

Nickel-catalyzed synthesis of aryl trifluoromethyl sulfides at room temperature.

PubMed

Zhang, Cheng-Pan; Vicic, David A

2012-01-11

Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of aryl iodides and aryl bromides at room temperature using the convenient [NMe(4)][SCF(3)] reagent. © 2011 American Chemical Society

Amperometric, Bipotentiometric, and Coulometric Titration.

ERIC Educational Resources Information Center

Stock, John T.

1984-01-01

Reviews literature on amperometric, bipotentiometric, and coulometric titration methods examining: apparatus and methodology; acid-base reactions; precipitation and complexing reactions (considering methods involving silver, mercury, EDTA or analogous reagents, and other organic compounds); and oxidation-reduction reactions (considering methods…

Chromosome-specific staining to detect genetic rearrangements associated with chromosome 3 and/or chromosome 17

DOEpatents

Gray, Joe W.; Pinkel, Daniel; Kallioniemi, Olli-Pekka; Kallioniemi, Anne; Sakamoto, Masaru

2002-01-01

Methods and compositions for staining based upon nucleic acid sequence that employ nudeic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Chromosome-specific staining to detect genetic rearrangements associated with chromosome 3 and/or chromosome 17

DOEpatents

Gray, Joe W.; Pinkel, Daniel; Kallioniemi, Olli-Pekka; Kallioniemi, Anne; Sakamoto, Masaru

2008-09-09

Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Chromosome-specific staining to detect genetic rearrangements associated with chromosome 3 and/or chromosome 17

DOEpatents

Gray, Joe W [San Francisco, CA; Pinkel, Daniel [Lafayette, CA; Kallioniemi, Olli-Pekka [Turku, FI; Kallioniemi, Anne [Tampere, FI; Sakamoto, Masaru [Tokyo, JP

2009-10-06

Methods and compositions for staining based upon nucleic acid sequence that employ .[.nudeic.]. .Iadd.nucleic .Iaddend.acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Chromosome-Specific Staining To Detect Genetic Rearrangements Associated With Chromosome 3 And/Or Chromosone 17

DOEpatents

Gray; Joe W.; Pinkel; Daniel; Kallioniemi; Olli-Pekka; Kallioniemi; Anne; Sakamoto; Masaru

2002-02-05

Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Ribosomal proteins S12 and S13 function as control elements for translocation of the mRNA:tRNA complex.

PubMed

Cukras, Anthony R; Southworth, Daniel R; Brunelle, Julie L; Culver, Gloria M; Green, Rachel

2003-08-01

Translocation of the mRNA:tRNA complex through the ribosome is promoted by elongation factor G (EF-G) during the translation cycle. Previous studies established that modification of ribosomal proteins with thiol-specific reagents promotes this event in the absence of EF-G. Here we identify two small subunit interface proteins S12 and S13 that are essential for maintenance of a pretranslocation state. Omission of these proteins using in vitro reconstitution procedures yields ribosomal particles that translate in the absence of enzymatic factors. Conversely, replacement of cysteine residues in these two proteins yields ribosomal particles that are refractive to stimulation with thiol-modifying reagents. These data support a model where S12 and S13 function as control elements for the more ancient rRNA- and tRNA-driven movements of translocation.

Cyclopropanes and hypervalent iodine reagents: high energy compounds for applications in synthesis and catalysis.

PubMed

Fernández González, Davinia; De Simone, Filippo; Brand, Jonathan P; Nicolai, Stefano; Waser, Jérôme

2011-01-01

One of the major challenges faced by organic chemistry is the efficient synthesis of increasingly complex molecules. Since October 2007, the Laboratory of Catalysis and Organic Synthesis (LCSO) at EPFL has been working on the development of catalytic reactions based on the Umpolung of the innate reactivity of functional groups. Electrophilic acetylene synthons have been developed using the exceptional properties of ethynyl benziodoxolone (EBX) hypervalent iodine reagents for the alkynylation of heterocycles and olefins. The obtained acetylenes are important building blocks for organic chemistry, material sciences and chemical biology. The ring-strain energy of donor-acceptor cyclopropanes was then used in the first catalytic formal homo-Nazarov cyclization. In the case of aminocyclopropanes, the method could be applied in the synthesis of the alkaloids aspidospermidine and goniomitine. The developed methods are expected to have a broad potential for the synthesis and functionalization of complex organic molecules, including carbocycles and heterocycles.

Solar photoassisted advanced oxidation process of azo dyes.

PubMed

Prato-Garcia, D; Buitrón, G

2009-01-01

Advanced oxidation processes assisted with natural solar radiation in CPC type reactors (parabolic collector compound), was applied for the degradation of three azo dyes: acid orange (AO7), acid red 151 (AR151) and acid blue 113 (AB113). Fenton, Fenton like and ferrioxalate-type complexes showed to be effective for degrade the azo linkage and moieties in different extensions. Initially, the best dose of reagents (Fe(3 + )-H(2)O(2)) was determined through a factorial experimental design, next, using response surface methodologies, the reagent consumption was reduced up to 40%, maintaining in all cases high decolourisation percentages (>98%) after 60 min. of phototreatment. In this work, it was also studied the effect of concentration changes of the influent between 100-300 mg/L and the operation of the photocatalytic process near neutral conditions (pH 6.0-6.5) by using ferrioxalate type complex (FeOx).

Do dihydroxymagnesium carboxylates form Grignard-type reagents? A theoretical investigation on decarboxylative fragmentation.

PubMed

Ruf, Alexander; Kanawati, Basem; Schmitt-Kopplin, Philippe

2018-03-27

Dihydroxymagnesium carboxylates [(OH) 2 MgO 2 CR] were probed for decarboxylation on a theoretical level, by utilizing both Møller-Plesset perturbation theory (MP2) and density functional theory (B3LYP-DFT) computations. This study is connected to the question of whether this recently introduced, astrobiologically relevant chemical class may form Grignard-type reagent molecules. To extract trends for a broad molecular mass range, different linear alkyl chain lengths between C 4 and C 11 were computed. The forward energy barrier for decarboxylation reactions increases linearly as a function of the ligand's chain length. Decarboxylation-type fragmentations of these organomagnesium compounds seem to be improbable in non-catalytic, low energetic environments. A high forward energy barrier (E MP2  > 55 kcal mol -1 ) towards a described transition state restricts the release of CO 2 . Nevertheless, we propose the release of CO 2 on a theoretical level, as been revealed via an intramolecular nucleophilic attack mechanism. Once the challenging transition state for decarboxylation is overcome, a stable Mg-C bond is formed. These mechanistic insights were gained by help of natural bond orbital analysis. The Cα atom (first carbon atom in the ligand chain attached to the carboxyl group) is thought to prefer binding towards the electrophilic magnesium coordination center, rather than towards the electrophilic CO 2 -carbon atom. Additionally, the putatively formed Grignard-type OH-bearing product molecules possess a more polarized Mg-C bond in comparison to RMgCl species. Therefore, carbanion formation from OH-bearing Grignard-type molecules is made feasible for triggering C-C bond formation reactions. Graphical abstract This study asks whether recently introduced, astrobiologically dihydroxymagnesium carboxylates form Grignard-type reagent molecules via decarboxylative fragmentation.

Systematic Evaluation of Bioorthogonal Reactions in Live Cells with Clickable HaloTag Ligands: Implications for Intracellular Imaging

PubMed Central

2015-01-01

Bioorthogonal reactions, including the strain-promoted azide–alkyne cycloaddition (SPAAC) and inverse electron demand Diels–Alder (iEDDA) reactions, have become increasingly popular for live-cell imaging applications. However, the stability and reactivity of reagents has never been systematically explored in the context of a living cell. Here we report a universal, organelle-targetable system based on HaloTag protein technology for directly comparing bioorthogonal reagent reactivity, specificity, and stability using clickable HaloTag ligands in various subcellular compartments. This system enabled a detailed comparison of the bioorthogonal reactions in live cells and informed the selection of optimal reagents and conditions for live-cell imaging studies. We found that the reaction of sTCO with monosubstituted tetrazines is the fastest reaction in cells; however, both reagents have stability issues. To address this, we introduced a new variant of sTCO, Ag-sTCO, which has much improved stability and can be used directly in cells for rapid bioorthogonal reactions with tetrazines. Utilization of Ag complexes of conformationally strained trans-cyclooctenes should greatly expand their usefulness especially when paired with less reactive, more stable tetrazines. PMID:26270632

Systematic Evaluation of Bioorthogonal Reactions in Live Cells with Clickable HaloTag Ligands: Implications for Intracellular Imaging.

PubMed

Murrey, Heather E; Judkins, Joshua C; Am Ende, Christopher W; Ballard, T Eric; Fang, Yinzhi; Riccardi, Keith; Di, Li; Guilmette, Edward R; Schwartz, Joel W; Fox, Joseph M; Johnson, Douglas S

2015-09-09

Bioorthogonal reactions, including the strain-promoted azide-alkyne cycloaddition (SPAAC) and inverse electron demand Diels-Alder (iEDDA) reactions, have become increasingly popular for live-cell imaging applications. However, the stability and reactivity of reagents has never been systematically explored in the context of a living cell. Here we report a universal, organelle-targetable system based on HaloTag protein technology for directly comparing bioorthogonal reagent reactivity, specificity, and stability using clickable HaloTag ligands in various subcellular compartments. This system enabled a detailed comparison of the bioorthogonal reactions in live cells and informed the selection of optimal reagents and conditions for live-cell imaging studies. We found that the reaction of sTCO with monosubstituted tetrazines is the fastest reaction in cells; however, both reagents have stability issues. To address this, we introduced a new variant of sTCO, Ag-sTCO, which has much improved stability and can be used directly in cells for rapid bioorthogonal reactions with tetrazines. Utilization of Ag complexes of conformationally strained trans-cyclooctenes should greatly expand their usefulness especially when paired with less reactive, more stable tetrazines.

MicrofluIdic circuit designs for performing electrokinetic manipulations that reduce the number of voltage sources and fluid reservoirs

DOEpatents

Jacobson, Stephen C.; Ramsey, J. Michael

2000-01-01

A microfabricated device and method for proportioning and mixing electrokinetically manipulated biological or chemical materials is disclosed. The microfabricated device mixes a plurality of materials in volumetric proportions controlled by the electrical resistances of tributary reagent channels through which the materials are transported. The microchip includes two or more tributary reagent channels combining at one or more junctions to form one or more mixing channels. By varying the geometries of the channels (length, cross section, etc.), a plurality of reagent materials can be mixed at a junction such that the proportions of the reagent materials in the mixing channel depend on a ratio of the channel geometries and material properties. Such an approach facilitates voltage division on the microchip without relying on external wiring schemes and voltage division techniques external to the microchip. Microchannel designs that provide the necessary voltage division to accomplish electrokinetic valving operations using a single voltage source and a switch are also described. In addition, microchannel designs that accomplish fluidic operation utilizing a minimal number of fluidic reservoirs are disclosed.

Microfluidic circuit designs for performing fluidic manipulations that reduce the number of pumping sources and fluid reservoirs

DOEpatents

Jacobson, Stephen C [Knoxville, TN; Ramsey, J Michael [Knoxville, TN

2001-01-01

A microfabricated device and method for proportioning and mixing biological or chemical materials by pressure- or vacuum-driven flow is disclosed. The microfabricated device mixes a plurality of materials in volumetric proportions controlled by the flow resistances of tributary reagent channels through which the materials are transported. The microchip includes two or more tributary reagent channels combining at one or more junctions to form one or more mixing channels. By varying the geometries of the channels (length, cross section, etc.), a plurality of reagent materials can be mixed at a junction such that the proportions of the reagent materials in the mixing channel depend on a ratio of the channel geometries and material properties. Such an approach facilitates flow division on the microchip without relying on techniques external to the microchip. Microchannel designs that provide the necessary flow division to accomplish valving operations using a minimum of pressure or vacuum sources are also described. In addition, microchannel designs that accomplish fluidic operation utilizing a minimal number of fluidic reservoirs are disclosed.

Oxidation of benzoin catalyzed by oxovanadium(IV) schiff base complexes

PubMed Central

2013-01-01

Background The oxidative transformation of benzoin to benzil has been accomplished by the use of a wide variety of reagents or catalysts and different reaction procedures. The conventional oxidizing agents yielded mainly benzaldehyde or/and benzoic acid and only a trace amount of benzil. The limits of practical utilization of these reagents involves the use of stoichiometric amounts of corrosive acids or toxic metallic reagents, which in turn produce undesirable waste materials and required high reaction temperatures. In recent years, vanadium complexes have attracted much attention for their potential utility as catalysts for various types of reactions. Results Active and selective catalytic systems of new unsymmetrical oxovanadium(IV) Schiff base complexes for the oxidation of benzoin is reported. The Schiff base ligands are derived between 2-aminoethanol and 2-hydroxy-1-naphthaldehyde (H2L1) or 3-ethoxy salicylaldehyde (H2L3); and 2-aminophenol and 3-ethoxysalicylaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L4). The unsymmetrical Schiff bases behave as tridentate dibasic ONO donor ligands. Reaction of these Schiff base ligands with oxovanadyl sulphate afforded the mononuclear oxovanadium(IV) complexes (VIVOLx.H2O), which are characterized by various physico-chemical techniques. The catalytic oxidation activities of these complexes for benzoin were evaluated using H2O2 as an oxidant. The best reaction conditions are obtained by considering the effect of solvent, reaction time and temperature. Under the optimized reaction conditions, VOL4 catalyst showed high conversion (>99%) with excellent selectivity to benzil (~100%) in a shorter reaction time compared to the other catalysts considered. Conclusion Four tridentate ONO type Schiff base ligands were synthesized. Complexation of these ligands with vanadyl(IV) sulphate leads to the formation of new oxovanadium(IV) complexes of type VIVOL.H2O. Elemental analyses and spectral data of the free ligands and their oxovanadium(IV) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds. Oxovanadium complexes were screened for the oxidation of benzoin to benzil using H2O2 as oxidant. The effect of time, solvent and temperature were optimized to obtain maximum yield. The catalytic activity results demonstrate that these catalytic systems are both highly active and selective for the oxidation of benzoin under mild reaction conditions. PMID:23294561

Oxidation of benzoin catalyzed by oxovanadium(IV) schiff base complexes.

PubMed

Alsalim, Tahseen A; Hadi, Jabbar S; Ali, Omar N; Abbo, Hanna S; Titinchi, Salam Jj

2013-01-07

The oxidative transformation of benzoin to benzil has been accomplished by the use of a wide variety of reagents or catalysts and different reaction procedures. The conventional oxidizing agents yielded mainly benzaldehyde or/and benzoic acid and only a trace amount of benzil. The limits of practical utilization of these reagents involves the use of stoichiometric amounts of corrosive acids or toxic metallic reagents, which in turn produce undesirable waste materials and required high reaction temperatures.In recent years, vanadium complexes have attracted much attention for their potential utility as catalysts for various types of reactions. Active and selective catalytic systems of new unsymmetrical oxovanadium(IV) Schiff base complexes for the oxidation of benzoin is reported. The Schiff base ligands are derived between 2-aminoethanol and 2-hydroxy-1-naphthaldehyde (H2L1) or 3-ethoxy salicylaldehyde (H2L3); and 2-aminophenol and 3-ethoxysalicylaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L4). The unsymmetrical Schiff bases behave as tridentate dibasic ONO donor ligands. Reaction of these Schiff base ligands with oxovanadyl sulphate afforded the mononuclear oxovanadium(IV) complexes (VIVOLx.H2O), which are characterized by various physico-chemical techniques.The catalytic oxidation activities of these complexes for benzoin were evaluated using H2O2 as an oxidant. The best reaction conditions are obtained by considering the effect of solvent, reaction time and temperature. Under the optimized reaction conditions, VOL4 catalyst showed high conversion (>99%) with excellent selectivity to benzil (~100%) in a shorter reaction time compared to the other catalysts considered. Four tridentate ONO type Schiff base ligands were synthesized. Complexation of these ligands with vanadyl(IV) sulphate leads to the formation of new oxovanadium(IV) complexes of type VIVOL.H2O.Elemental analyses and spectral data of the free ligands and their oxovanadium(IV) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds.Oxovanadium complexes were screened for the oxidation of benzoin to benzil using H2O2 as oxidant. The effect of time, solvent and temperature were optimized to obtain maximum yield. The catalytic activity results demonstrate that these catalytic systems are both highly active and selective for the oxidation of benzoin under mild reaction conditions.

Direct synthesis of anti-1,3-diols through nonclassical reaction of aryl Grignard reagents with isopropenyl acetate.

PubMed

Jiao, Yinchun; Cao, Chenzhong; Zhou, Zaichun

2011-01-21

A series of symmetrical aromatic 1,3-diols were efficiently synthesized from substituted aryl Grignard reagents and isopropenyl acetate in a one-step reaction that formed anti products as the major species. Both experimental and theoretical studies suggested that the reaction involves the formation of a relatively stable intermediate E containing a six-membered ring from intermediate A. The stereoselectivity of the reactions and the molecular structure of the products were confirmed by NMR spectroscopy, X-ray diffraction, and gas chromatography.

Synthesis of the active form of loxoprofen by using allylic substitutions in two steps.

PubMed

Hyodo, Tomonori; Kiyotsuka, Yohei; Kobayashi, Yuichi

2009-03-05

High regioselectivity for allylic substitution of the cyclopentenyl picolinate 5 with benzylcopper reagent was attained with ZnBr(2), and the finding was applied to the p-BrC(6)H(4)CH(2) reagent. The cyclopentene moiety in the product was reduced to the cyclopentane, and the p-BrC(6)H(4) was converted to the "Cu"C(6)H(4) for the second allylic substitution with picolinate 8 to furnish the title compound after oxidative cleavage of the resulting olefin moiety.

Immune complexes formed following the binding of anti–platelet factor 4 (CXCL4) antibodies to CXCL4 stimulate human neutrophil activation and cell adhesion

PubMed Central

Xiao, Zhihua; Visentin, Gian P.; Dayananda, Kannayakanahalli M.

2008-01-01

We tested the possibility that immune complexes formed following platelet factor 4 (PF4/CXCL4) binding to anti-PF4 antibody can stimulate neutrophil activation, similar to previous reports with platelets. Monoclonal Abs against PF4 and IgG from a heparin-induced thrombocytopenia (HIT) patient were applied. We observed that although PF4 or anti-PF4 antibody alone did not alter neutrophil function, costimulation with both reagents resulted in approximately 3-fold increase in cell surface Mac-1 expression, enhanced cell adhesion via L-selectin and CD18 integrins, and degranulation of secondary and tertiary granules. The level of Mac-1 up-regulation peaked at an intermediate PF4 dose, suggesting that functional response varies with antigen-antibody stoichiometry. PF4 binding to neutrophils was blocked by chondroitinase ABC. Cell activation was inhibited by both chondroitinase ABC and anti-CD32/FcγRII blocking mAb, IV.3. Confocal microscopy demonstrated that immune complexes colocalize with CD32a. Studies with HIT IgG demonstrated that neutrophils could be activated in the absence of exogenous heparin. These data, together, show that leukocyte surface chondroitin sulfates promote neutrophil activation by enhancing immune-complex binding to CD32a. Studies with recombinant PF4 suggest a role for arginine 49 in stabilizing PF4-chondroitin binding. Neutrophils activated via this mechanism may contribute to thrombosis and inflammation in patients mounting an immune response to PF4-heparin. PMID:18539895

NHC→SiCl4 : an ambivalent carbene-transfer reagent.

PubMed

Böttcher, Tobias; Steinhauer, Simon; Lewis-Alleyne, Lesley C; Neumann, Beate; Stammler, Hans-Georg; Bassil, Bassem S; Röschenthaler, Gerd-Volker; Hoge, Berthold

2015-01-07

The addition of BCl3 to the carbene-transfer reagent NHC→SiCl4 (NHC=1,3-dimethylimidazolidin-2-ylidene) gave the tetra- and pentacoordinate trichlorosilicon(IV) cations [(NHC)SiCl3 ](+) and [(NHC)2 SiCl3 ](+) with tetrachloroborate as counterion. This is in contrast to previous reactions, in which NHC→SiCl4 served as a transfer reagent for the NHC ligand. The addition of BF3 ⋅OEt2 , on the other hand, gave NHC→BF3 as the product of NHC transfer. In addition, the highly Lewis acidic bis(pentafluoroethyl)silane (C2 F5 )2 SiCl2 was treated with NHC→SiCl4 . In acetonitrile, the cationic silicon(IV) complexes [(NHC)SiCl3 ](+) and [(NHC)2 SiCl3 ](+) were detected with [(C2 F5 )SiCl3 ](-) as counterion. A similar result was already reported for the reaction of NHC→SiCl4 with (C2 F5 )2 SiH2 , which gave [(NHC)2 SiCl2 H][(C2 F5 )SiCl3 ]. If the reaction medium was changed to dichloromethane, the products of carbene transfer, NHC→Si(C2 F5 )2 Cl2 and NHC→Si(C2 F5 )2 ClH, respectively, were obtained instead. The formation of the latter species is a result of chloride/hydride metathesis. These compounds may serve as valuable precursors for electron-poor silylenes. Furthermore, the reactivity of NHC→SiCl4 towards phosphines is discussed. The carbene complex NHC→PCl3 shows similar reactivity to NHC→SiCl4 , and may even serve as a carbene-transfer reagent as well. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative Peptidomics with Five-plex Reductive Methylation labels

NASA Astrophysics Data System (ADS)

Tashima, Alexandre K.; Fricker, Lloyd D.

2017-12-01

Quantitative peptidomics and proteomics often use chemical tags to covalently modify peptides with reagents that differ in the number of stable isotopes, allowing for quantitation of the relative peptide levels in the original sample based on the peak height of each isotopic form. Different chemical reagents have been used as tags for quantitative peptidomics and proteomics, and all have strengths and weaknesses. One of the simplest approaches uses formaldehyde and sodium cyanoborohydride to methylate amines, converting primary and secondary amines into tertiary amines. Up to five different isotopic forms can be generated, depending on the isotopic forms of formaldehyde and cyanoborohydride reagents, allowing for five-plex quantitation. However, the mass difference between each of these forms is only 1 Da per methyl group incorporated into the peptide, and for many peptides there is substantial overlap from the natural abundance of 13C and other isotopes. In this study, we calculated the contribution from the natural isotopes for 26 native peptides and derived equations to correct the peak intensities. These equations were applied to data from a study using human embryonic kidney HEK293T cells in which five replicates were treated with 100 nM vinblastine for 3 h and compared with five replicates of cells treated with control medium. The correction equations brought the replicates to the expected 1:1 ratios and revealed significant decreases in levels of 21 peptides upon vinblastine treatment. These equations enable accurate quantitation of small changes in peptide levels using the reductive methylation labeling approach. [Figure not available: see fulltext.

Quantitative Peptidomics with Five-plex Reductive Methylation labels

NASA Astrophysics Data System (ADS)

Tashima, Alexandre K.; Fricker, Lloyd D.

2018-05-01

Quantitative peptidomics and proteomics often use chemical tags to covalently modify peptides with reagents that differ in the number of stable isotopes, allowing for quantitation of the relative peptide levels in the original sample based on the peak height of each isotopic form. Different chemical reagents have been used as tags for quantitative peptidomics and proteomics, and all have strengths and weaknesses. One of the simplest approaches uses formaldehyde and sodium cyanoborohydride to methylate amines, converting primary and secondary amines into tertiary amines. Up to five different isotopic forms can be generated, depending on the isotopic forms of formaldehyde and cyanoborohydride reagents, allowing for five-plex quantitation. However, the mass difference between each of these forms is only 1 Da per methyl group incorporated into the peptide, and for many peptides there is substantial overlap from the natural abundance of 13C and other isotopes. In this study, we calculated the contribution from the natural isotopes for 26 native peptides and derived equations to correct the peak intensities. These equations were applied to data from a study using human embryonic kidney HEK293T cells in which five replicates were treated with 100 nM vinblastine for 3 h and compared with five replicates of cells treated with control medium. The correction equations brought the replicates to the expected 1:1 ratios and revealed significant decreases in levels of 21 peptides upon vinblastine treatment. These equations enable accurate quantitation of small changes in peptide levels using the reductive methylation labeling approach. [Figure not available: see fulltext.

Recovery of heavy metals from spent Ni-Cd batteries by a potentiostatic electrodeposition technique

NASA Astrophysics Data System (ADS)

Yang, Chun-Chen

Two heavy metals, Cd and Ni, have been separately recovered from spent AA-size Ni-Cd batteries by the potentiostatic electrodeposition and chemical precipitation methods, respectively. Various types and concentrations of HCl, H 2SO 4, and HNO 3 acids had been used as leach extractants. Experimental results indicate that the acid with the best leach capability is 4 M HCl. Three complexing reagents of NH 3, sodium acetate, sodium citrate have been chosen and tested. The most effective buffer is sodium citrate. The optimum mole ratio of metallic ion to citrate ion is 1:1. The recovery process for Cd metal is conducted by the potentiostatic electrodeposition in a leach electrolyte with a sodium citrate complex. The optimum applied potential for Cd recovery is in the range -1100 to -1120 mV (versus saturated calomel electrode (SCE)). The current efficiency for the recovery process is between 70 and 90% and depends strongly on the process parameters, e.g. liquor, concentration, applied potential, temperature, type of complex reagents, mole ratio, mass-transfer rate.

A general method for bead-enhanced quantitation by flow cytometry

PubMed Central

Montes, Martin; Jaensson, Elin A.; Orozco, Aaron F.; Lewis, Dorothy E.; Corry, David B.

2009-01-01

Flow cytometry provides accurate relative cellular quantitation (percent abundance) of cells from diverse samples, but technical limitations of most flow cytometers preclude accurate absolute quantitation. Several quantitation standards are now commercially available which, when added to samples, permit absolute quantitation of CD4+ T cells. However, these reagents are limited by their cost, technical complexity, requirement for additional software and/or limited applicability. Moreover, few studies have validated the use of such reagents in complex biological samples, especially for quantitation of non-T cells. Here we show that addition to samples of known quantities of polystyrene fluorescence standardization beads permits accurate quantitation of CD4+ T cells from complex cell samples. This procedure, here termed single bead-enhanced cytofluorimetry (SBEC), was equally capable of enumerating eosinophils as well as subcellular fragments of apoptotic cells, moieties with very different optical and fluorescent characteristics. Relative to other proprietary products, SBEC is simple, inexpensive and requires no special software, suggesting that the method is suitable for the routine quantitation of most cells and other particles by flow cytometry. PMID:17067632

Spectroscopic methods for aqueous cyclodextrin inclusion complex binding measurement for 1,4-dioxane, chlorinated co-contaminants, and ozone

NASA Astrophysics Data System (ADS)

Khan, Naima A.; Johnson, Michael D.; Carroll, Kenneth C.

2018-03-01

Recalcitrant organic contaminants, such as 1,4-dioxane, typically require advanced oxidation process (AOP) oxidants, such as ozone (O3), for their complete mineralization during water treatment. Unfortunately, the use of AOPs can be limited by these oxidants' relatively high reactivities and short half-lives. These drawbacks can be minimized by partial encapsulation of the oxidants within a cyclodextrin cavity to form inclusion complexes. We determined the inclusion complexes of O3 and three common co-contaminants (trichloroethene, 1,1,1-trichloroethane, and 1,4-dioxane) as guest compounds within hydroxypropyl-β-cyclodextrin. Both direct (ultraviolet or UV) and competitive (fluorescence changes with 6-p-toluidine-2-naphthalenesulfonic acid as the probe) methods were used, which gave comparable results for the inclusion constants of these species. Impacts of changing pH and NaCl concentrations were also assessed. Binding constants increased with pH and with ionic strength, which was attributed to variations in guest compound solubility. The results illustrate the versatility of cyclodextrins for inclusion complexation with various types of compounds, binding measurement methods are applicable to a wide range of applications, and have implications for both extraction of contaminants and delivery of reagents for treatment of contaminants in wastewater or contaminated groundwater.

Structural characterization by cross-linking reveals the detailed architecture of a coatomer-related heptameric module from the nuclear pore complex.

PubMed

Shi, Yi; Fernandez-Martinez, Javier; Tjioe, Elina; Pellarin, Riccardo; Kim, Seung Joong; Williams, Rosemary; Schneidman-Duhovny, Dina; Sali, Andrej; Rout, Michael P; Chait, Brian T

2014-11-01

Most cellular processes are orchestrated by macromolecular complexes. However, structural elucidation of these endogenous complexes can be challenging because they frequently contain large numbers of proteins, are compositionally and morphologically heterogeneous, can be dynamic, and are often of low abundance in the cell. Here, we present a strategy for the structural characterization of such complexes that has at its center chemical cross-linking with mass spectrometric readout. In this strategy, we isolate the endogenous complexes using a highly optimized sample preparation protocol and generate a comprehensive, high-quality cross-linking dataset using two complementary cross-linking reagents. We then determine the structure of the complex using a refined integrative method that combines the cross-linking data with information generated from other sources, including electron microscopy, X-ray crystallography, and comparative protein structure modeling. We applied this integrative strategy to determine the structure of the native Nup84 complex, a stable hetero-heptameric assembly (∼ 600 kDa), 16 copies of which form the outer rings of the 50-MDa nuclear pore complex (NPC) in budding yeast. The unprecedented detail of the Nup84 complex structure reveals previously unseen features in its pentameric structural hub and provides information on the conformational flexibility of the assembly. These additional details further support and augment the protocoatomer hypothesis, which proposes an evolutionary relationship between vesicle coating complexes and the NPC, and indicates a conserved mechanism by which the NPC is anchored in the nuclear envelope. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Rapid presumptive identification of Cryptococcus neoformans by staphylococcal coagglutination.

PubMed Central

Maccani, J E

1981-01-01

A coagglutination reagent was prepared by sensitizing the Cowan I strain of Staphylococcus aureus with rabbit immune globulin directed against Cryptococcus neofromans A15 and absorbed with C. laurentii. This reagent was evaluated for its usefulness in differentiating C. neoformans from other yeast colonies rapidly. Antigen-containing extracts were prepared form Sabouraud dextrose agar cultures of 48 C. neoformans, 33 other Cryptococcus species, 21 Candida, 4 Torulopsis, 3 Saccharomyces, and 2 Rhodotorula strains. This was done by suspending a 0.001-ml loopful of colony growth in 0.5 ml of phenolized saline, mixing for 30 s, and then centrifuging. Equal volumes (50 microliters) of coagglutination reagent and yeast extract were mixed within marked circles on a glass slide and then mechanically rotated at 180 rpm for 8 min. Forty-five of the 48 strains of C. neoformans produced strong (3+ to 4+) agglutination, and 3 strains of serotype C produced weak (1+ to 2+) agglutination with the reagent. Other Cryptococcus species which reacted positively were 4 C. albidus subsp. diffluens, 7 C. albidus subsp. albidus, and 2 C. terreus strains; however, false-positive errors in identification were circumvented by performing a supplemental rapid test for nitrate utilization which differentiated these yeasts from C. neoformans. None of the other yeasts tested (including 14 C. laurentii, 2 C. luteolus, and 2 C. uniguttulatus strains) produced any degree of agglutination with the reagent. A commercial cryptococcal latex agglutination reagent (Crypto-Test, Microbiological Associates, Walkersville, Md.) proved less reliable for identifying C. neoformans yeast colonies because of cross-reactions which occurred with all other species of Cryptococcus tested. PMID:7016909

Affinity proteomics to study endogenous protein complexes: Pointers, pitfalls, preferences and perspectives

PubMed Central

LaCava, John; Molloy, Kelly R.; Taylor, Martin S.; Domanski, Michal; Chait, Brian T.; Rout, Michael P.

2015-01-01

Dissecting and studying cellular systems requires the ability to specifically isolate distinct proteins along with the co-assembled constituents of their associated complexes. Affinity capture techniques leverage high affinity, high specificity reagents to target and capture proteins of interest along with specifically associated proteins from cell extracts. Affinity capture coupled to mass spectrometry (MS)-based proteomic analyses has enabled the isolation and characterization of a wide range of endogenous protein complexes. Here, we outline effective procedures for the affinity capture of protein complexes, highlighting best practices and common pitfalls. PMID:25757543

Precious Metals Recovery from Electroplating Wastewater: A Review

NASA Astrophysics Data System (ADS)

Azmi, A. A.; Jai, J.; Zamanhuri, N. A.; Yahya, A.

2018-05-01

Metal bearing electroplating wastewater posts great health and environmental concerns, but could also provide opportunities for precious and valuable metal recovery, which can make the treatment process more cost-effective and sustainable. Current conventional electroplating wastewater treatment and metal recovery methods include chemical precipitation, coagulation and flocculation, ion exchange, membrane filtration, adsorption, electrochemical treatment and photocatalysis. However, these physico-chemical methods have several disadvantages such as high initial capital cost, high operational cost due to expensive chemical reagents and electricity supply, generation of metal complexes sludge which requires further treatment, ineffective in diluted and/or concentrated wastewater, low precious metal selectivity, and slow recovery process. On the other hand, metal bio-reduction assisted by bioactive phytochemical compounds extracted from plants and plant parts is a new found technology explored by several researchers in recent years aiming to recover precious and valuable metals from secondary sources mainly industrial wastewater by utilizing low-cost and eco-friendly biomaterials as reagents. Extract of plants contains polyphenolic compounds which have great antioxidant properties and reducing capacities, able to reduce metal ions into zerovalent metal atoms and stabilize the metal particles formed. This green bio-recovery method has a value added in their end products since the metals are recovered in nano-sized particles which are more valuable and have high commercial demand in other fields ranging from electrochemistry to medicine.

Exploitation of phosphorescent labelling reagent of fullerol-fluorescein isothiocyanate and new method for the determination of trace alkaline phosphatase as well as forecast of human diseases.

PubMed

Liu, Jia-Ming; Huang, Xiao-Mei; Liu, Zhen-Bo; Lin, Shao-Qin; Li, Fei-Ming; Gao, Fei; Li, Zhi-Ming; Zeng, Li-Qing; Li, Lian-Ying; Ouyang, Ying

2009-08-26

A new phosphorescent labelling reagent consisting of fullerol, fluorescein isothiocyanate and N,N-dimethylaniline (F-ol-(FITC)(n)-DMA) was developed. The mode of action is based on the reactivity of the active -OH group in F-ol with the -COOH group of FITC to form an F-ol-(FITC)(n)-DMA complex containing several FITC molecules. F-ol-(FITC)(n)-DMA increased the number of luminescent molecules in the biological target of WGA-AP-WGA-F-ol-(FITC)(n)-DMA (WGA and AP are wheat germ agglutinin and alkaline phosphatase, respectively) which improved the sensitivity using solid substrate room temperature phosphorimetry (SSRTP) detection. The proposed method provided high sensitivity and strong specificity for WGA-AP. The limit of detection (LD) was 0.15 ag AP spot(-1) for F-ol and 0.097 ag AP spot(-1) for FITC in F-ol-(FITC)(n)-DMA, which was lower than the method using single luminescent molecules of F-ol-DMA and FITC-DMA to label WGA (0.20 ag AP spot(-1) for F-ol-DMA and 0.22 ag AP spot(-1) for FITC-DMA). Results for the determination of AP in human serum were in good agreement with those obtained by enzyme-linked immunosorbent assay. The mechanism of F-ol-(FITC)(n)-DMA labelling of WGA was discussed.

Decontamination of soil containing POPs by the combined action of solid Fenton-like reagents and microwaves.

PubMed

Cravotto, Giancarlo; Di Carlo, Stefano; Ondruschka, Bernd; Tumiatti, Vander; Roggero, Carlo Maria

2007-10-01

The effect on halogenated aromatics of solid, non-toxic oxidants such as sodium percarbonate and the urea/hydrogen peroxide complex (Fenton-like reagents) was investigated. A microwaves-assisted, solvent-free method for soil decontamination is presented. It marks a considerable advance in the search of more efficient, environment-friendly procedures for the degradative oxidation of persistent organic pollutants. Residual pollutants in treated soil samples were determined by GC/MS analysis after solvent extraction or direct thermal desorption. Results showed that 4-chloronaphthol, 2,4-dichlorophenoxyacetic acid and p-nonylphenol had been degraded completely, 2,4-dibromophenol to a large extent.

C(2) symmetric chiral NHC ligand for asymmetric quaternary carbon constructing copper-catalyzed conjugate addition of grignard reagents to 3-substituted cyclohexenones.

PubMed

Matsumoto, Yasumasa; Yamada, Ken-ichi; Tomioka, Kiyoshi

2008-06-20

The asymmetric construction of quaternary carbon centers by conjugate addition of Grignard reagents to 3-methyl- and 3-ethylcyclohexenones was realized in a maximum enantioselectivity of 80% by using a C 2 symmetric chiral N-heterocyclic carbene (NHC)-copper catalyst, generated from (4 S,5 S)-1,3-bis(2-methoxyphenyl)-4,5-diphenyl-4,5-dihydro-1 H-imidazol-3-ium tetrafluoroborate and copper(II) triflate. The stereostructures of the NHC-Au complexes were analyzed by X-ray crystallography, which rationalized the good stereocontrolling ability of N-aryl NHCs.

Steric hindrance effects in the use of heterocyclic azodyestuffs as spectrophotometric reagents.

PubMed

Geary, W J; Bottomley, F

1967-05-01

The heterocyclic azo dyestuffs 4-(n-methyl-2 -pyridylazo)-resorcinol (where n = 3', 4', 5', 6') have been prepared, and their possible use as spectrophotometric reagents investigated. The dyestuffs are shown to function analogously to the parent ligand 4-(2'-pyridylazo) resorcinol (PAR) in giving red complexes with the ions Co(2+), Ni(2+), Cu(2+), Zn(2+) and UO(2)(2+). Steric effects resulting from the position of the methyl group in the heterocyclic ring are shown to occur in relation both to the spectra of the dyestuffs themselves and to the sensitivity of their reactions with the metal ions.

On the structure of transition metals complexes with the new tridentate dye of thiazole series: Theoretical and experimental studies

NASA Astrophysics Data System (ADS)

Fizer, Maksym; Sidey, Vasyl; Tupys, Andrii; Ostapiuk, Yurii; Tymoshuk, Oleksandr; Bazel, Yaroslav

2017-12-01

The 1-[(5-Benzyl-1,3-thiazol-2-yl)diazenyl]naphthalene-2-ol (BnTAN) is a recently synthesized azo dye that can act as a tridentate ligand in complexes with transition metals. In a series of previous works, this analytical reagent was shown to be applicable for selective, reliable, express and relatively inexpensive determination of heavy metals in different objects through the spectrophotometric technique. Although the action of 1-(2-thiazolylazo)-2-naphthol (TAN) dyes as tridentate ligands has been suggested in the literature long time ago, due to the lack of experimental data, it was necessary to investigate the mechanism of formation and the structure of BnTAN complexes with the such transition metals as Cu(II), Zn(II) and Cd(II). Furthermore, the reactivity and properties of different acidity forms and conformers of BnTAN and related TAN dyes were not fully defined, so the determination of these properties by analysis of wavefunction was also necessary. Two standard spectrophotometric methods and voltammetric technique were used to determine the composition of complex of BnTAN with metals ions. All three experimental methods indicate that coordination ratio of metal:dye is equal to 1:2. Moreover, this study reports the stability and geometry of conformers of different forms (anionic/neutral/cationic) of BnTAN, along with a detailed analysis of electronic properties, reactivity and aromaticity of the most stable conformers of BnTAN forms. Each of the above forms has some difference in position of benzyl ring against the thiazole moiety, which is explained in terms of attraction and repulsion of these two fragments induced by partial atomic charges. The crucial influence of hydrogen bond and weak non-covalent interactions between naphthyl, aza- and thiazolyl fragments has been established. The quantum chemical calculations have shown that partial atomic charges of anionic, neutral and cationic forms can explain the reactivity of each BnTAN form, and have also clarified the mechanism of formation of metal complex through the connection of metal with phenol oxygen, thiazolyl nitrogen and one nitrogen of aza group - thus giving two five-membered metal-containing cycles and confirming that BnTAN acts as a tridentate ligand. The obtained results introduce novel and crucial information which can assist in understanding the mechanism of complex formation of BnTAN and display the strength and level of detail of applying quantum chemical methods to reveal the reactivity, energy properties, and electronic properties of this new dye.

A well-defined terminal vanadium(III) oxo complex.

PubMed

King, Amanda E; Nippe, Michael; Atanasov, Mihail; Chantarojsiri, Teera; Wray, Curtis A; Bill, Eckhard; Neese, Frank; Long, Jeffrey R; Chang, Christopher J

2014-11-03

The ubiquity of vanadium oxo complexes in the V+ and IV+ oxidation states has contributed to a comprehensive understanding of their electronic structure and reactivity. However, despite being predicted to be stable by ligand-field theory, the isolation and characterization of a well-defined terminal mononuclear vanadium(III) oxo complex has remained elusive. We present the synthesis and characterization of a unique terminal mononuclear vanadium(III) oxo species supported by the pentadentate polypyridyl ligand 2,6-bis[1,1-bis(2-pyridyl)ethyl]pyridine (PY5Me2). Exposure of [V(II)(NCCH3)(PY5Me2)](2+) (1) to either dioxygen or selected O-atom-transfer reagents yields [V(IV)(O)(PY5Me2)](2+) (2). The metal-centered one-electron reduction of this vanadium(IV) oxo complex furnishes a stable, diamagnetic [V(III)(O)(PY5Me2)](+) (3) species. The vanadium(III) oxo species is unreactive toward H- and O-atom transfer but readily reacts with protons to form a putative vanadium hydroxo complex. Computational results predict that further one-electron reduction of the vanadium(III) oxo species will result in ligand-based reduction, even though pyridine is generally considered to be a poor π-accepting ligand. These results have implications for future efforts toward low-valent vanadyl chemistry, particularly with regard to the isolation and study of formal vanadium(II) oxo species.

Adapter reagents for protein site specific dye labeling.

PubMed

Thompson, Darren A; Evans, Eric G B; Kasza, Tomas; Millhauser, Glenn L; Dawson, Philip E

2014-05-01

Chemoselective protein labeling remains a significant challenge in chemical biology. Although many selective labeling chemistries have been reported, the practicalities of matching the reaction with appropriately functionalized proteins and labeling reagents is often a challenge. For example, we encountered the challenge of site specifically labeling the cellular form of the murine Prion protein with a fluorescent dye. To facilitate this labeling, a protein was expressed with site specific p-acetylphenylalanine. However, the utility of this acetophenone reactive group is hampered by the severe lack of commercially available aminooxy fluorophores. Here we outline a general strategy for the efficient solid phase synthesis of adapter reagents capable of converting maleimido-labels into aminooxy or azide functional groups that can be further tuned for desired length or solubility properties. The utility of the adapter strategy is demonstrated in the context of fluorescent labeling of the murine Prion protein through an adapted aminooxy-Alexa dye. © 2014 Wiley Periodicals, Inc.

Adapter Reagents for Protein Site Specific Dye Labeling

PubMed Central

Thompson, Darren A.; Evans, Eric G. B.; Kasza, Tomas; Millhauser, Glenn L.; Dawson, Philip E.

2016-01-01

Chemoselective protein labeling remains a significant challenge in chemical biology. Although many selective labeling chemistries have been reported, the practicalities of matching the reaction with appropriately functionalized proteins and labeling reagents is often a challenge. For example, we encountered the challenge of site specifically labeling the cellular form of the murine Prion protein with a fluorescent dye. To facilitate this labeling, a protein was expressed with site specific p-acetylphenylalanine. However, the utility of this aceto-phenone reactive group is hampered by the severe lack of commercially available aminooxy fluorophores. Here we outline a general strategy for the efficient solid phase synthesis of adapter reagents capable of converting maleimido-labels into aminooxy or azide functional groups that can be further tuned for desired length or solubility properties. The utility of the adapter strategy is demonstrated in the context of fluorescent labeling of the murine Prion protein through an adapted aminooxy-Alexa dye. PMID:24599728

Characteristic constants of 2,2',4'-trihydroxyazobenzene-5-sulfonic acid, a reagent for spectrophotometric analysis

USGS Publications Warehouse

Fletcher, Mary H.

1960-01-01

The dye 2,2',4'-trihydroxyazobenzene-5-sulfonic acid, has shown promise as a reagent for the determination of zirconium. As the literature contains very little information about this dye, basic data pertinent to its use as a reagent were determined. The sulfonic acid group and all three of the hydroxy groups show acidic characteristics. Apparent dissociation constants were determined for the three more labile protons and the approximate order of magnitude for the fourth constant was estimated. Absorption spectra for the different ionization species are given. A curve is also included which shows the fraction of dye in the different ionization forms at acidities from 10.35M hydrochloric acid to pH 11.9. A sixth dye species was found in 1.0 to 8.4M potassium hydroxide solutions, but its nature is unknown.

Taming tosyl azide: the development of a scalable continuous diazo transfer process.

PubMed

Deadman, Benjamin J; O'Mahony, Rosella M; Lynch, Denis; Crowley, Daniel C; Collins, Stuart G; Maguire, Anita R

2016-04-07

Heat and shock sensitive tosyl azide was generated and used on demand in a telescoped diazo transfer process. Small quantities of tosyl azide were accessed in a 'one pot' batch procedure using shelf stable, readily available reagents. For large scale diazo transfer reactions tosyl azide was generated and used in a telescoped flow process, to mitigate the risks associated with handling potentially explosive reagents on scale. The in situ formed tosyl azide was used to rapidly perform diazo transfer to a range of acceptors, including β-ketoesters, β-ketoamides, malonate esters and β-ketosulfones. An effective in-line quench of sulfonyl azides was also developed, whereby a sacrificial acceptor molecule ensured complete consumption of any residual hazardous diazo transfer reagent. The telescoped diazo transfer process with in-line quenching was used to safely prepare over 21 g of an α-diazocarbonyl in >98% purity without any column chromatography.

Assembly and Properties of Heterobimetallic CoII/III/CaII Complexes with Aquo and Hydroxo Ligands

PubMed Central

Lacy, David C.; Park, Young Jun; Ziller, Joseph W.; Yano, Junko; Borovik, A. S.

2012-01-01

The use of water as a reagent in redox-driven reactions is advantageous because it is abundant and environmentally compatible. The conversion of water to dioxygen in photosynthesis illustrates one example, in which a redox-inactive CaII ion and four manganese ions are required for function. In this report we describe the stepwise formation of two new heterobimetallic complexes containing CoII/III and CaII ions, and either hydroxo or aquo ligands. The preparation of a 4-coordinate CoII synthon was achieved with the tripodal ligand, N,N′,N″-[2,2′,2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido, [MST]3−. Water binds to [CoIIMST]− to form the 5-coordinate [CoIIMST(OH2)]− complex that was used to prepare the CoII/CaII complex [CoIIMST(μ-OH2)CaII⊂15-crown-5(OH2)]+ ([CoII(μ-OH2)CaIIOH2]+). [CoII(μ-OH2)CaOH2]+ contained two aquo ligands, one bonded to the CaII ion and one bridging between the two metal ions and thus represents an unusual example of a heterobimetallic complex containing 2 aquo ligands spanning different metal ions. Both aquo ligands formed intramolecular hydrogen bonds with the [MST]3− ligand. [CoIIMST(OH2)]− was oxidized to form [CoIIIMST(OH2)] that was further converted to [CoIIIMST(μ-OH)CaII⊂15-crown-5]+ ([CoIII(μ-OH)CaII]+) in the presence of base and CaIIOTf2/15-crown-5. [CoIII(μ-OH)CaII]+ was also synthesized from the oxidation of [CoIIMST]− with PhIO in the presence of CaIIOTf2/15-crown-5. Allowing [CoIII(μ-OH)CaII]+ to react with diphenylhydrazine afforded [CoII(μ-OH2)CaIIOH2]+ and azobenzene. Additionally, the characterization of [CoIII(μ-OH)CaII]+ provides another formulation for the previously reported CoIV–oxo complex, [(TMG3tren)CoIV(μ-O)ScIII(OTf)3]2+ to one that instead could contain a CoIII–OH unit. PMID:22998407

Reagent and labor cost optimization through automation of fluorescence in situ hybridization (FISH) with the VP 2000: an Italian case study.

PubMed

Zanatta, Lucia; Valori, Laura; Cappelletto, Eleonora; Pozzebon, Maria Elena; Pavan, Elisabetta; Dei Tos, Angelo Paolo; Merkle, Dennis

2015-02-01

In the modern molecular diagnostic laboratory, cost considerations are of paramount importance. Automation of complex molecular assays not only allows a laboratory to accommodate higher test volumes and throughput but also has a considerable impact on the cost of testing from the perspective of reagent costs, as well as hands-on time for skilled laboratory personnel. The following study tracked the cost of labor (hands-on time) and reagents for fluorescence in situ hybridization (FISH) testing in a routine, high-volume pathology and cytogenetics laboratory in Treviso, Italy, over a 2-y period (2011-2013). The laboratory automated FISH testing with the VP 2000 Processor, a deparaffinization, pretreatment, and special staining instrument produced by Abbott Molecular, and compared hands-on time and reagent costs to manual FISH testing. The results indicated significant cost and time saving when automating FISH with VP 2000 when more than six FISH tests were run per week. At 12 FISH assays per week, an approximate total cost reduction of 55% was observed. When running 46 FISH specimens per week, the cost saving increased to 89% versus manual testing. The results demonstrate that the VP 2000 processor can significantly reduce the cost of FISH testing in diagnostic laboratories. © 2014 Society for Laboratory Automation and Screening.

Limitations of a hemolytic plaque assay for IgG-anti-IgG rheumatoid factor-producing cells.

PubMed

Venn, A J; Dresser, D W

1987-09-24

An attempt has been made to develop a hemolytic plaque assay capable of detecting homophile IgG rheumatoid factor (RF)-producing cells. Anti-immunoglobulin allotype-developing reagents were used to distinguish between target and effector IgG. The hemolytic assay has been used to demonstrate an apparently high level of homophile IgM and IgG RF-producing cells in the spleens and lymph nodes of mice stimulated by LPS. However, it appears that a large proportion of the plaques obtained in these assays are due to an artefact resulting from cross-linking of target and effector molecules by the developing reagents. In the case of IgM RF the artefact depends on the presence of a small contamination of the target IgG by IgM, allowing cross-linking of target and effector IgM by the anti-mu-specific developing reagent. With the IgG RF, cross-reactivity of the rabbit anti-Ighb allotype-developing serum for the 'wrong' (Igha) allotype, normally undetectable, becomes sufficient to be biologically relevant when the developing antibody is complexed by being bound to its target (Ighb) allotype. Nevertheless anti-allotype reagents may afford an accurate means of detecting homophile IgG RF producing cells using other assay systems.

Reverse flow injection spectrophotometric determination of ciprofloxacin in pharmaceuticals using iron from soil as a green reagent

NASA Astrophysics Data System (ADS)

Palamy, Sysay; Ruengsitagoon, Wirat

2018-02-01

A novel reverse flow injection spectrophotometric method for the determination of ciprofloxacin was successfully combined with the on-line introduction of an iron solution extracted from soil as green reagent. The assay was optimized by a univariate method to select the optimum conditions for the highest absorbance and highest stability of the complex. Beer-Lambert's law (λmax = 440 nm) is obeyed in the range 0.5-50 μg mL- 1 with a correlation coefficient (r2) of 0.9976 and 0.9996 using soil as green reagent from Khon Kaen, Thailand and Vientiane, Laos, respectively. The average percentage recoveries were in the range of 98.55-102.14% and the precision was in the range of 0.80-1.73%. The limit of detection and the limit of quantitation were 0.20 and 0.69 μg mL- 1, respectively, with a sampling rate of over 46 samples h- 1. The method was successfully applied to the determination of ciprofloxacin in commercial pharmaceutical formulations. The results were in good agreement with those obtained by the reference HPLC method using a t-test at 95% of confidence level for comparison. This method is suitable for laboratories looking for alternative analytical methods using green reagents.

An automated optofluidic biosensor platform combining interferometric sensors and injection moulded microfluidics.

PubMed

Szydzik, C; Gavela, A F; Herranz, S; Roccisano, J; Knoerzer, M; Thurgood, P; Khoshmanesh, K; Mitchell, A; Lechuga, L M

2017-08-08

A primary limitation preventing practical implementation of photonic biosensors within point-of-care platforms is their integration with fluidic automation subsystems. For most diagnostic applications, photonic biosensors require complex fluid handling protocols; this is especially prominent in the case of competitive immunoassays, commonly used for detection of low-concentration, low-molecular weight biomarkers. For this reason, complex automated microfluidic systems are needed to realise the full point-of-care potential of photonic biosensors. To fulfil this requirement, we propose an on-chip valve-based microfluidic automation module, capable of automating such complex fluid handling. This module is realised through application of a PDMS injection moulding fabrication technique, recently described in our previous work, which enables practical fabrication of normally closed pneumatically actuated elastomeric valves. In this work, these valves are configured to achieve multiplexed reagent addressing for an on-chip diaphragm pump, providing the sample and reagent processing capabilities required for automation of cyclic competitive immunoassays. Application of this technique simplifies fabrication and introduces the potential for mass production, bringing point-of-care integration of complex automated microfluidics into the realm of practicality. This module is integrated with a highly sensitive, label-free bimodal waveguide photonic biosensor, and is demonstrated in the context of a proof-of-concept biosensing assay, detecting the low-molecular weight antibiotic tetracycline.

Quality of commercially produced Shigella serogrouping and serotyping antisera.

PubMed Central

Evins, G M; Gheesling, L L; Tauxe, R V

1988-01-01

Shigella grouping antisera from five manufacturers and typing antisera from two were purchased and evaluated with homologous and heterologous Shigella strains in the slide agglutination test. Only 31 of 73 (42%) antisera were satisfactory. In many instances, the antisera gave negative, as opposed to weak, reactions when they should have given strong positive reactions. Four reagents cross-reacted with Shigella strains. Of the 19 polyvalent grouping antisera to subgroups Shigella dysenteriae serotypes 1 through 7, S. flexneri serotypes 1 through 6, S. boydii serotypes 1 through 7, and S. sonnei forms I, II, only one S. sonnei reagent and five S. flexneri reagents were satisfactory with greater than or equal to 90% of the homologous strains. The reagent of poorest quality was satisfactory with only 18% of the homologous strains. There were three polyvalent antisera to the higher types of S. dysenteriae and S. boydii, which were available from only one company, that adequately identified 80, 63, and 65% of the homologous strains. Typing antisera were available from only two companies, and 30 of 51 (59%) were satisfactory. Commercially available Shigella antisera are inadequate for the laboratory testing required for planning the development of and evaluating Shigella vaccines. PMID:3281972

Effects of redox and sulfhydryl reagents on the bioelectric properties of the giant axon of the squid.

PubMed

Huneeus-Cox, F; Fernandez, H L; Smith, B H

1966-09-01

The effects of internally and externally applied sulfhydryl reagents on the bioelectric properties of the giant axon of the squid Loligo pealeii and Dosidicus gigas were studied. Cysteine-HCl (400 mM, pH 7.3) was used to remove axoplasm from the perfusion channel. Oxidizing agents (1 to 60 mM) tended to increase the duration of the action potential and had a slow, irreversible blocking effect when perfused internally; the membrane potential was little affected. Reducing agents applied internally caused a decrease in the spike duration without affecting its height or the membrane potential, although at high concentrations there was reversible deterioration of the action potential. Both external and internal perfusion of mercaptide-forming reagents caused deterioration in the action and membrane potentials with conduction block occurring in 5 to 45 min. 2-mercaptoethanol reversed the effects. Thiol alkylating reagents, iodoacetate and iodoacetamide, were without effect. N-ethylmaleimide did, however, block. Tests with chelating agents for nonheme iron in the membrane brought about no change in the electrical parameters. The implications of the present findings with regard to the macromolecular mechanism of excitation are discussed.

Effects of Redox and Sulfhydryl Reagents on the Bioelectric Properties of the Giant Axon of the Squid

PubMed Central

Huneeus-Cox, F.; Fernandez, H. L.; Smith, B. H.

1966-01-01

The effects of internally and externally applied sulfhydryl reagents on the bioelectric properties of the giant axon of the squid Loligo pealeii and Dosidicus gigas were studied. Cysteine-HCl (400 mM, pH 7.3) was used to remove axoplasm from the perfusion channel. Oxidizing agents (1 to 60 mM) tended to increase the duration of the action potential and had a slow, irreversible blocking effect when perfused internally; the membrane potential was little affected. Reducing agents applied internally caused a decrease in the spike duration without affecting its height or the membrane potential, although at high concentrations there was reversible deterioration of the action potential. Both external and internal perfusion of mercaptide-forming reagents caused deterioration in the action and membrane potentials with conduction block occurring in 5 to 45 min. 2-mercaptoethanol reversed the effects. Thiol alkylating reagents, iodoacetate and iodoacetamide, were without effect. N-ethylmaleimide did, however, block. Tests with chelating agents for nonheme iron in the membrane brought about no change in the electrical parameters. The implications of the present findings with regard to the macromolecular mechanism of excitation are discussed. ImagesFigure 1 PMID:5970570

Determination of dasatinib in the tablet dosage form by ultra high performance liquid chromatography, capillary zone electrophoresis, and sequential injection analysis.

PubMed

Gonzalez, Aroa Garcia; Taraba, Lukáš; Hraníček, Jakub; Kozlík, Petr; Coufal, Pavel

2017-01-01

Dasatinib is a novel oral prescription drug proposed for treating adult patients with chronic myeloid leukemia. Three analytical methods, namely ultra high performance liquid chromatography, capillary zone electrophoresis, and sequential injection analysis, were developed, validated, and compared for determination of the drug in the tablet dosage form. The total analysis time of optimized ultra high performance liquid chromatography and capillary zone electrophoresis methods was 2.0 and 2.2 min, respectively. Direct ultraviolet detection with detection wavelength of 322 nm was employed in both cases. The optimized sequential injection analysis method was based on spectrophotometric detection of dasatinib after a simple colorimetric reaction with folin ciocalteau reagent forming a blue-colored complex with an absorbance maximum at 745 nm. The total analysis time was 2.5 min. The ultra high performance liquid chromatography method provided the lowest detection and quantitation limits and the most precise and accurate results. All three newly developed methods were demonstrated to be specific, linear, sensitive, precise, and accurate, providing results satisfactorily meeting the requirements of the pharmaceutical industry, and can be employed for the routine determination of the active pharmaceutical ingredient in the tablet dosage form. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploring reaction pathways in the hydrothermal growth of phase-pure bismuth ferrites

NASA Astrophysics Data System (ADS)

Goldman, Abby R.; Fredricks, Jeremy L.; Estroff, Lara A.

2017-06-01

Phase-pure bismuth ferrites (BiFeO3 and Bi2Fe4O9) are grown using hydrothermal synthesis. In addition to varying the KOH, bismuth, and iron salt concentrations to tune which crystalline phases are formed, we identified that a 48 h, pre-furnace, room temperature reaction is critical for the formation of phase-pure BiFeO3. To understand the reaction pathways leading to the different bismuth ferrite phases, we investigate the changes in composition of the intermediate products as a function of reagent concentrations and room temperature reaction times. During the syntheses that included a room temperature reaction, Bi25FeO40 is formed in the intermediate products, and BiFeO3 is the majority phase of the final products. The BiFeO3 crystals grown using this method are clusters of faceted subunits. These results indicate that forming Bi25FeO40 is a productive route to the formation of BiFeO3. Bi2Fe4O9 is formed via an alternate reaction pathway that proceeded via an amorphous precursor. This improved understanding of how hydrothermal synthesis can be used to control the phase-purity and morphology of bismuth ferrites opens doors to explore the multiferroic properties of BiFeO3 with complex morphologies.

Proteome-Wide Profiling of Targets of Cysteine reactive Small Molecules by Using Ethynyl Benziodoxolone Reagents.

PubMed

Abegg, Daniel; Frei, Reto; Cerato, Luca; Prasad Hari, Durga; Wang, Chao; Waser, Jerome; Adibekian, Alexander

2015-09-07

In this study, we present a highly efficient method for proteomic profiling of cysteine residues in complex proteomes and in living cells. Our method is based on alkynylation of cysteines in complex proteomes using a "clickable" alkynyl benziodoxolone bearing an azide group. This reaction proceeds fast, under mild physiological conditions, and with a very high degree of chemoselectivity. The formed azide-capped alkynyl-cysteine adducts are readily detectable by LC-MS/MS, and can be further functionalized with TAMRA or biotin alkyne via CuAAC. We demonstrate the utility of alkynyl benziodoxolones for chemical proteomics applications by identifying the proteomic targets of curcumin, a diarylheptanoid natural product that was and still is part of multiple human clinical trials as anticancer agent. Our results demonstrate that curcumin covalently modifies several key players of cellular signaling and metabolism, most notably the enzyme casein kinase I gamma. We anticipate that this new method for cysteine profiling will find broad application in chemical proteomics and drug discovery. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Importance of Nonclassical σ-Hole Interactions for the Reactivity of λ3-Iodane Complexes.

PubMed

Pinto de Magalhães, Halua; Togni, Antonio; Lüthi, Hans Peter

2017-11-17

Key for the observed reactivity of λ 3 -iodanes, powerful reagents for the selective transfer of functional groups to nucleophiles, are the properties of the 3-center-4-electron bond involving the iodine atom and the two linearly arranged ligands. This bond is also involved in the formation of the initial complex between the λ 3 -iodane and a nucleophile, which can be a solvent molecule or a reactant. The bonding in such complexes can be described by means of σ-hole interactions. In halogen compounds, σ-hole interaction was identified as a force in crystal packing or in the formation of supramolecular chains. More recently, σ-hole interactions were also shown to affect the reactivity of the iodine-based hypervalent reagents. Relative to their monovalent counterparts, where the σ-hole is located on the extension of the sigma-bond, in the hypervalent species our DFT calculations reveal the formation of a nonclassical σ-hole region with one or even two maxima. This observation is also made in fully relativistic calculations. The SAPT analysis shows that the σ-hole bond between the λ 3 -iodane and the nucleophile is not necessarily of purely electrostatic nature but may also contain a significant covalent component. This covalent component may facilitate chemical transformation of the compound by means of reductive elimination or other mechanisms and is therefore an indicator for its reactivity. Here, we also show that the shape, location, and strength of the σ-holes can be tuned by the choice of ligands and measures such as Brønsted activation of the iodane reagent. At the limit, the tuning transforms the nonclassical σ-hole regions into coordination sites, which allows us to control how a nucleophile will bind and react with the iodane.

Histochemical evidence for the differential surface labeling, uptake, and intracellular transport of a colloidal gold-labeled insulin complex by normal human blood cells.

PubMed

Ackerman, G A; Wolken, K W

1981-10-01

A colloidal gold-labeled insulin-bovine serum albumin (GIA) reagent has been developed for the ultrastructural visualization of insulin binding sites on the cell surface and for tracing the pathway of intracellular insulin translocation. When applied to normal human blood cells, it was demonstrated by both visual inspection and quantitative analysis that the extent of surface labeling, as well as the rate and degree of internalization of the insulin complex, was directly related to cell type. Further, the pathway of insulin (GIA) transport via round vesicles and by tubulo-vesicles and saccules and its subsequent fate in the hemic cells was also related to cell variety. Monocytes followed by neutrophils bound the greatest amount of labeled insulin. The majority of lymphocytes bound and internalized little GIA, however, between 5-10% of the lymphocytes were found to bind considerable quantities of GIA. Erythrocytes rarely bound the labeled insulin complex, while platelets were noted to sequester large quantities of the GIA within their extracellular canalicular system. GIA uptake by the various types of leukocytic cells appeared to occur primarily by micropinocytosis and by the direct opening of cytoplasmic tubulo-vesicles and saccules onto the cell surface in regions directly underlying surface-bound GIA. Control procedures, viz., competitive inhibition of GIA labeling using an excess of unlabeled insulin in the incubation medium, preincubation of the GIA reagent with an antibody directed toward porcine insulin, and the incorporation of 125I-insulin into the GIA reagent, indicated the specificity and selectivity of the GIA histochemical procedure for the localization of insulin binding sites.

Sensitivity and selectivity of switchable reagent ion soft chemical ionization mass spectrometry for the detection of picric acid.

PubMed

Agarwal, Bishu; González-Méndez, Ramón; Lanza, Matteo; Sulzer, Philipp; Märk, Tilmann D; Thomas, Neil; Mayhew, Chris A

2014-09-18

We have investigated the reactions of NO(+), H3O(+), O2(+), and Kr(+) with picric acid (2,4,6 trinitrophenol, C6H3N3O7, PiA) using a time-of-flight mass spectrometer with a switchable reagent ion source. NO(+) forms a simple adduct ion PiA·NO(+), while H3O(+) reacts with PiA via nondissociative proton transfer to form PiAH(+). In contrast, both O2(+) and Kr(+) react with PiA by nondissociative charge transfer to produce PiA(+). For Kr(+), we also observe dissociation of PiA, producing NO2(+) with a branching percentage of approximately 40%. For the reagent ions H3O(+) and O2(+) (and operating the drift tube with normal laboratory air), we find that the intensities of the PiAH(+) and PiA(+) ions both exhibit a peak at a given drift-tube voltage (which is humidity dependent). This unusual behavior implies a peak in the detection sensitivity of PiA as a function of the drift-tube voltage (and hence E/N). Aided by electronic-structure calculations and our previous studies of trinitrotoluene and trinitrobenzene, we provide a possible explanation for the observed peak in the detection sensitivity of PiA.

Determining the thickness of aliphatic alcohol monolayers covalently attached to silicon oxide surfaces using angle-resolved X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Austin W. H.; Kim, Dongho; Gates, Byron D.

2018-04-01

The thickness of alcohol based monolayers on silicon oxide surfaces were investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS). Advantages of using alcohols as building blocks for the formation of monolayers include their widespread availability, ease of handling, and stability against side reactions. Recent progress in microwave assisted reactions demonstrated the ease of forming uniform monolayers with alcohol based reagents. The studies shown herein provide a detailed investigation of the thickness of monolayers prepared from a series of aliphatic alcohols of different chain lengths. Monolayers of 1-butanol, 1-hexanol, 1-octanol, 1-decanol, and 1-dodecanol were each successfully formed through microwave assisted reactions and characterized by ARXPS techniques. The thickness of these monolayers consistently increased by ∼1.0 Å for every additional methylene (CH2) within the hydrocarbon chain of the reagents. Tilt angles of the molecules covalently attached to silicon oxide surfaces were estimated to be ∼35° for each type of reagent. These results were consistent with the observations reported for thiol based or silane based monolayers on either gold or silicon oxide surfaces, respectively. The results of this study also suggest that the alcohol based monolayers are uniform at a molecular level.

The GC-MS Observation of Intermediates in a Stepwise Grignard Addition Reaction

ERIC Educational Resources Information Center

Latimer, Devin

2007-01-01

Preparation of phenylmagnesium bromide described by Eckert, addition of three equivalents of Grignard reagent to diethyl carbonate to form triphenylmethanol and a series of GC-MS procedures that form intermediates. The analysis is consistent with a gas chromatogram and mass spectrum for each of the expected intermediates and final product of the…

Mechanism of red mud combined with Fenton's reagent in sewage sludge conditioning.

PubMed

Zhang, Hao; Yang, Jiakuan; Yu, Wenbo; Luo, Sen; Peng, Li; Shen, Xingxing; Shi, Yafei; Zhang, Shinan; Song, Jian; Ye, Nan; Li, Ye; Yang, Changzhu; Liang, Sha

2014-08-01

Red mud was evaluated as an alternative skeleton builder combined with Fenton's reagent in sewage sludge conditioning. The results show that red mud combined with Fenton's reagent showed good conditioning capability with the pH of the filtrate close to neutrality, indicating that red mud acted as a neutralizer as well as a skeleton builder when jointly used with Fenton's reagent. Through response surface methodology (RSM), the optimal dosages of Fe(2+), H2O2 and red mud were proposed as 31.9, 33.7 and 275.1 mg/g DS (dry solids), respectively. The mechanism of the composite conditioner could be illuminated as follows: (1) extracellular polymeric substances (EPS), including loosely bound EPS and tightly bound EPS, were degraded into dissolved organics, e.g., proteins and polysaccharides; (2) bound water was released and converted into free water due to the degradation of EPS; and (3) morphology of the conditioned sludge exhibited a porous structure in contrast with the compact structure of raw sludge, and the addition of red mud formed new mineral phases and a rigid lattice structure in sludge, allowing the outflow of free water. Thus, sludge dewatering performance was effectively improved. The economic assessment for a wastewater treatment plant of 370,000 equivalent inhabitants confirms that using red mud conditioning, combined with Fenton's reagent, leads to a saving of approximately 411,000 USD/y or 50.8 USD/t DS comparing with using lime and ordinary Portland cement combined with Fenton's reagent, and approximately 612,000 USD/y or 75.5 USD/t DS comparing with the traditional treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Gene gymnastics

PubMed Central

Vijayachandran, Lakshmi S; Thimiri Govinda Raj, Deepak B; Edelweiss, Evelina; Gupta, Kapil; Maier, Josef; Gordeliy, Valentin; Fitzgerald, Daniel J; Berger, Imre

2013-01-01

Most essential activities in eukaryotic cells are catalyzed by large multiprotein assemblies containing up to ten or more interlocking subunits. The vast majority of these protein complexes are not easily accessible for high resolution studies aimed at unlocking their mechanisms, due to their low cellular abundance and high heterogeneity. Recombinant overproduction can resolve this bottleneck and baculovirus expression vector systems (BEVS) have emerged as particularly powerful tools for the provision of eukaryotic multiprotein complexes in high quality and quantity. Recently, synthetic biology approaches have begun to make their mark in improving existing BEVS reagents by de novo design of streamlined transfer plasmids and by engineering the baculovirus genome. Here we present OmniBac, comprising new custom designed reagents that further facilitate the integration of heterologous genes into the baculovirus genome for multiprotein expression. Based on comparative genome analysis and data mining, we herein present a blueprint to custom design and engineer the entire baculovirus genome for optimized production properties using a bottom-up synthetic biology approach. PMID:23328086

Detergent-Specific Membrane Protein Crystallization Screens

NASA Technical Reports Server (NTRS)

Wiener, Michael

2007-01-01

A suite of reagents has been developed for three-dimensional crystallization of integral membranes present in solution as protein-detergent complexes (PDCs). The compositions of these reagents have been determined in part by proximity to the phase boundaries (lower consolute boundaries) of the detergents present in the PDCs. The acquisition of some of the requisite phase-boundary data and the preliminary design of several of the detergent- specific screens was supported by a NASA contract. At the time of expiration of the contract, a partial set of preliminary screens had been developed. This work has since been extended under non-NASA sponsorship, leading to near completion of a set of 20 to 30 different and unique detergent- specific 96-condition screens.

Multidimensional data analysis in immunophenotyping.

PubMed

Loken, M R

2001-05-01

The complexity of cell populations requires careful selection of reagents to detect cells of interest and distinguish them from other types. Additional reagents are frequently used to provide independent criteria for cell identification. Two or three monoclonal antibodies in combination with forward and right-angle light scatter generate a data set that is difficult to visualize because the data must be represented in four- or five-dimensional space. The separation between cell populations provided by the multiple characteristics is best visualized by multidimensional analysis using all parameters simultaneously to identify populations within the resulting hyperspace. Groups of cells are distinguished based on a combination of characteristics not apparent in any usual two-dimensional representation of the data.

Chiral reagents in glycosylation and modification of carbohydrates.

PubMed

Wang, Hao-Yuan; Blaszczyk, Stephanie A; Xiao, Guozhi; Tang, Weiping

2018-02-05

Carbohydrates play a significant role in numerous biological events, and the chemical synthesis of carbohydrates is vital for further studies to understand their various biological functions. Due to the structural complexity of carbohydrates, the stereoselective formation of glycosidic linkages and the site-selective modification of hydroxyl groups are very challenging and at the same time extremely important. In recent years, the rapid development of chiral reagents including both chiral auxiliaries and chiral catalysts has significantly improved the stereoselectivity for glycosylation reactions and the site-selectivity for the modification of carbohydrates. These new tools will greatly facilitate the efficient synthesis of oligosaccharides, polysaccharides, and glycoconjugates. In this tutorial review, we will summarize these advances and highlight the most recent examples.

Flow-controlled magnetic particle manipulation

DOEpatents

Grate, Jay W [West Richland, WA; Bruckner-Lea, Cynthia J [Richland, WA; Holman, David A [Las Vegas, NV

2011-02-22

Inventive methods and apparatus are useful for collecting magnetic materials in one or more magnetic fields and resuspending the particles into a dispersion medium, and optionally repeating collection/resuspension one or more times in the same or a different medium, by controlling the direction and rate of fluid flow through a fluid flow path. The methods provide for contacting derivatized particles with test samples and reagents, removal of excess reagent, washing of magnetic material, and resuspension for analysis, among other uses. The methods are applicable to a wide variety of chemical and biological materials that are susceptible to magnetic labeling, including, for example, cells, viruses, oligonucleotides, proteins, hormones, receptor-ligand complexes, environmental contaminants and the like.

Magnesium, zinc, aluminium and gallium hydride complexes of the transition metals† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6cc05702k

PubMed Central

Butler, Michael J.

2017-01-01

The preparation and applications of heterobimetallic complexes continue to occupy researchers in the fields of organometallic, main group, and coordination chemistry. This interest stems from the promise these complexes hold as precursors to materials, reagents in synthesis and as new catalysis. Here we survey and organise the state-of-the-art understanding of the TM–H–M linkage (M = Mg, Zn, Al, Ga). We discuss the structure and bonding in these complexes, their known reactivity, and their largely unrealised potential in catalysis. PMID:28070586

Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

PubMed

Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

2016-08-01

The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

Identification of Carboxylate, Phosphate, and Phenoxide Functionalities in Deprotonated Molecules Related to Drug Metabolites via Ion-Molecule Reactions with water and Diethylhydroxyborane

NASA Astrophysics Data System (ADS)

Zhu, Hanyu; Ma, Xin; Kong, John Y.; Zhang, Minli; Kenttämaa, Hilkka I.

2017-10-01

Tandem mass spectrometry based on ion-molecule reactions has emerged as a powerful tool for structural elucidation of ionized analytes. However, most currently used reagents were designed to react with protonated analytes, making them suboptimal for acidic analytes that are preferentially detected in negative ion mode. In this work we demonstrate that the phenoxide, carboxylate, and phosphate functionalities can be identified in deprotonated molecules by use of a combination of two reagents, diethylmethoxyborane (DEMB) and water. A novel reagent introduction setup that allowed DEMB and water to be separately introduced into the ion trap region of the mass spectrometer was developed to facilitate fundamental studies of this reaction. A new reagent, diethylhydroxyborane (DEHB), was generated inside the ion trap by hydrolysis of DEMB on introduction of water. Most carboxylates and phenoxides formed a DEHB adduct, followed by addition of one water molecule and subsequent ethane elimination (DEHB adduct +H2O - CH3CH3) as the major product ion. Phenoxides with a hydroxy group adjacent to the deprotonation site and phosphates formed a DEHB adduct, followed by ethane elimination (DEHB adduct - CH3CH3). Deprotonated molecules with strong intramolecular hydrogen bonds or without the aforementioned functionalities, including sulfates, were unreactive toward DEHB/H2O. Reaction mechanisms were explored via isotope labeling experiments and quantum chemical calculations. The mass spectrometry method allowed the differentiation of phenoxide-, carboxylate-, phosphate-, and sulfate-containing analytes. Finally, it was successfully coupled with high-performance liquid chromatography for the analysis of a mixture containing hymecromone, a biliary spasm drug, and its three possible metabolites. [Figure not available: see fulltext.

Replacing antibodies with modified DNA aptamers in vaccine potency assays.

PubMed

Trausch, Jeremiah J; Shank-Retzlaff, Mary; Verch, Thorsten

2017-10-04

Vaccine in vitro potency assays are vital regulatory tests that are used to confirm the presence and concentration of an antigen of interest in a form that directly or indirectly relates to protective activity in patients. Current assays come in many forms, but they almost exclusively use antibody reagents for selective detection of the target antigen. Antibodies provide specific recognition of vaccine antigens but also exhibit drawbacks such as stability limitations, cost, and lot-to-lot variation, which can make it challenging to maintain the reagent throughout the lifetime of the vaccine. We explored replacing antibodies with aptamers. Aptamers are macromolecules, such as nucleic acids, which can bind to their targets with high specificity and affinity, similar to that of antibodies. Some of the advantages of using aptamers over antibodies is that aptamers can be more stable, smaller, less expensive to produce, synthesized in vitro, and logistically easier to supply throughout the multi-decade lifespan of a commercial vaccine. We created modified DNA aptamers against the common vaccine carrier protein, CRM 197 . Several aptamers were discovered and one was chosen for further characterization. The binding kinetics of the aptamer revealed an off-rate 16-fold slower than anti-CRM 197 antibodies used for comparison. The aptamers were more sensitive than available antibodies in some assay formats and comparable in others. The aptamer epitope was mapped to the receptor-binding domain of CRM 197 , a site adjacent to a known antibody binding site. These data address some key aspects for a path forward in replacing antibodies with aptamers for use as critical reagents in vaccine assays. We further highlight the possibility of using nucleic acid reagents to develop next generation potency assays. Copyright © 2017 Elsevier Ltd. All rights reserved.

An exploratory investigation of polar organic compounds in waters from a lead–zinc mine and mill complex

USGS Publications Warehouse

Rostad, Colleen E.; Schmitt, Christopher J.; Schumacher, John G.; Leiker, Thomas J.

2011-01-01

Surface water samples were collected in 2006 from a lead mine-mill complex in Missouri to investigate possible organic compounds coming from the milling process. Water samples contained relatively high concentrations of dissolved organic carbon (DOC; greater than 20 mg/l) for surface waters but were colorless, implying a lack of naturally occurring aquatic humic or fulvic acids. Samples were extracted by three different types of solid-phase extraction and analyzed by electrospray ionization/mass spectrometry. Because large amounts of xanthate complexation reagents are used in the milling process, techniques were developed to extract and analyze for sodium isopropyl xanthate and sodium ethyl xanthate. Although these xanthate reagents were not found, trace amounts of the degradates, isopropyl xanthyl thiosulfonate and isopropyl xanthyl sulfonate, were found in most locations sampled, including the tailings pond downstream. Dioctyl sulfosuccinate, a surfactant and process filtering aid, was found at concentrations estimated at 350 μg/l at one mill outlet, but not downstream. Release of these organic compounds downstream from lead-zinc mine and milling areas has not previously been reported. A majority of the DOC remains unidentified.

Phosphate Detection through a Cost-Effective Carbon Black Nanoparticle-Modified Screen-Printed Electrode Embedded in a Continuous Flow System.

PubMed

Talarico, Daria; Cinti, Stefano; Arduini, Fabiana; Amine, Aziz; Moscone, Danila; Palleschi, Giuseppe

2015-07-07

An automatable flow system for the continuous and long-term monitoring of the phosphate level has been developed using an amperometric detection method based on the use of a miniaturized sensor. This method is based on the monitoring of an electroactive complex obtained by the reaction between phosphate and molybdate that is consequently reduced at the electrode surface. The use of a screen-printed electrode modified with carbon black nanoparticles (CBNPs) leads to the quantification of the complex at low potential, because CBNPs are capable of electrocatalitically enhancing the phosphomolybdate complex reduction at +125 mV versus Ag/AgCl without fouling problems. The developed system also incorporates reagents and waste storage and is connected to a portable potentiostat for rapid detection and quantification of phosphate. Main analytical parameters, such as working potential, reagent concentration, type of cell, and flow rate, were evaluated and optimized. This system was characterized by a low detection limit (6 μM). Interference studies were carried out. Good recovery percentages comprised between 89 and 131.5% were achieved in different water sources, highlighting its suitability for field measurements.

Stability and Unimolecular Reactivity of Palladate(II) Complexes [Ln PdR3 ]- (L=Phosphine, R=Organyl, n=0 and 1).

PubMed

Kolter, Marlene; Koszinowski, Konrad

2016-10-24

The reduction of Pd II precatalysts to catalytically active Pd 0 species is a key step in many palladium-mediated cross-coupling reactions. Besides phosphines, the stoichiometrically used organometallic reagents can afford this reduction, but do so in a poorly understood way. To elucidate the mechanism of this reaction, we have treated solutions of Pd(OAc) 2 and a phosphine ligand L in tetrahydrofuran with RMgCl (R=Ph, Bn, Bu) as well as other organometallic reagents. Analysis of these model systems by electrospray- ionization mass spectrometry found palladate(II) complexes [L n PdR 3 ] - (n=0 and 1), thus pointing to the occurrence of transmetallation reactions. Upon gas-phase fragmentation, the [L n PdR 3 ] - anions preferentially underwent a reductive elimination to yield Pd 0 species. The sequence of the transmetallation and reductive elimination, thus, constitutes a feasible mechanism for the reduction of the Pd(OAc) 2 precatalyst. Other species of interest observed include the Pd IV complex [PdBn 5 ] - , which did not fragment via a reductive elimination but lost BnH instead. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

21 CFR 866.3870 - Trypanosoma spp. serological reagents.

Code of Federal Regulations, 2010 CFR

2010-04-01

... by fever, chills, headache, and vomiting. Central nervous system involvement produces typical.... Chagas disease, an acute form of trypanosomiasis in children, most seriously affects the central nervous system and heart muscle. (b) Classification. Class I (general controls). ...

21 CFR 866.3870 - Trypanosoma spp. serological reagents.

Code of Federal Regulations, 2011 CFR

2011-04-01

... by fever, chills, headache, and vomiting. Central nervous system involvement produces typical.... Chagas disease, an acute form of trypanosomiasis in children, most seriously affects the central nervous system and heart muscle. (b) Classification. Class I (general controls). ...

21 CFR 866.3870 - Trypanosoma spp. serological reagents.

Code of Federal Regulations, 2014 CFR

2014-04-01

... by fever, chills, headache, and vomiting. Central nervous system involvement produces typical.... Chagas disease, an acute form of trypanosomiasis in children, most seriously affects the central nervous system and heart muscle. (b) Classification. Class I (general controls). ...

21 CFR 866.3870 - Trypanosoma spp. serological reagents.

Code of Federal Regulations, 2012 CFR

2012-04-01

... by fever, chills, headache, and vomiting. Central nervous system involvement produces typical.... Chagas disease, an acute form of trypanosomiasis in children, most seriously affects the central nervous system and heart muscle. (b) Classification. Class I (general controls). ...

21 CFR 866.3870 - Trypanosoma spp. serological reagents.

Code of Federal Regulations, 2013 CFR

2013-04-01

... by fever, chills, headache, and vomiting. Central nervous system involvement produces typical.... Chagas disease, an acute form of trypanosomiasis in children, most seriously affects the central nervous system and heart muscle. (b) Classification. Class I (general controls). ...

CLEAN CHEMICAL SYNTHESIS IN WATER

EPA Science Inventory

Newer green chemistry approach to accomplish chemical synthesis in water is summarized. Recent global developments pertaining to C-C bond forming reactions using metallic reagents and direct use of the renewable materials such as carbohydrates without derivatization are described...

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

NASA Technical Reports Server (NTRS)

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600?C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form? process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

NASA Technical Reports Server (NTRS)

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600 C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Use of ferrous chelates of SH-containing amino acids and peptides for the removal of NO/sub x/ and SO/sub 2/ from flue gas

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

Chang, S.G.; Littlejohn, D.; Liu, D.K.

1988-11-01

The use of ferrous complexes of SH-containing amino acids and peptides for the removal of NO and SO/sub 2/ in wet flue gas clean-up systems is reported. The ferrous chelates investigated in the present study include those of cysteine, N-acetylcysteine, penicillamine, N-acetylpenicillamine, glutathine, and cysteinylglycine. Compared to conventional chelates such as EDTA, these thioamino acids/peptides not only can stabilize ferrous ion in alkaline solutions to promote the absorption of NO but are also capable of rapidly reducing any ferric ions formed during the scrubbing process back to ferrous ions so that continual absorption of NO can be achieved. In themore » case of ferrous cysteine and ferrous penicillamine, most of the absorbed NO is reduced to N/sub 2/. The disulfide form of several of the thioamino acids/peptides produced upon oxidation can be conveniently reduced by SO/sub 2/ and H/sub 2/S to regenerate the starting materials, thus making possible the recycling of the reagents.« less

Location and ion-binding of membrane-associated valinomycin, a proton nuclear magnetic resonance study.

PubMed

Meers, P; Feigenson, G W

1988-03-03

Valinomycin, incorporated in small unilamellar vesicles of perdeuterated dimyristoylphosphatidylcholine, reveals several well-resolved 1H-NMR resonances. These resonances were used to examine the location, orientation and ion-binding of membrane-bound valinomycin. The order of affinity of membrane-bound valinomycin for cations is Rb+ greater than K+ greater than Cs+ greater than Ba2+, and binding is sensitive to surface change. The exchange between bound and free forms is fast on the NMR time scale. The intrinsic binding constants, extrapolated to zero anion concentration, are similar to those determined in aqueous solution. Rb+ and K+ show 1:1 binding to valinomycin, whereas the stoichiometry of Cs+ and Ba2+ is not certain. Paramagnetic chemical shift reagents and nitroxide spin label relaxation probes were used to study the location and orientation of valinomycin in the membrane. Despite relatively fast exchange of bound cations, the time average location of the cation-free form of valinomycin is deep within the bilayer under the conditions of these experiments. Upon complexation to K+, valinomycin moves closer to the interfacial region.

Gas phase hydrolysis of formaldehyde to form methanediol: impact of formic acid catalysis.

PubMed

Hazra, Montu K; Francisco, Joseph S; Sinha, Amitabha

2013-11-21

We find that formic acid (FA) is very effective at facilitating diol formation through its ability to reduce the barrier for the formaldehyde (HCHO) hydrolysis reaction. The rate limiting step in the mechanism involves the isomerization of a prereactive collision complex formed through either the HCHO···H2O + FA and/or HCHO + FA···H2O pathways. The present study finds that the effective barrier height, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state (TS) and the HCHO···H2O + FA and HCHO + FA···H2O starting reagents, are respectively only ∼1 and ∼4 kcal/mol. These barriers are substantially lower than the ∼17 kcal/mol barrier associated with the corresponding step in the hydrolysis of HCHO catalyzed by a single water molecule (HCHO + H2O + H2O). The significantly lower barrier heights for the formic acid catalyzed pathway reveal a new important role that organic acids play in the gas phase hydrolysis of atmospheric carbonyl compounds.

Stabilization of coacervate systems by products of abiogenic oxidation of low-molecular-weight compounds using the energy of. gamma. radiation

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

Evreinova, T.N.; Kuzin, A.M.; Kryukova, L.M.

1976-01-01

The purpose of the study was to determine the possibility of stabilization of protein-carbohydrate and protein-nucleic acid systems by products of the abiogenic oxidation of pyrocatechol, pyrogallol, and o-dianisidine using the energy of gamma radiation. The protein-nucleic acid system was produced by mixing the following reagents: histone, DNA, acetate buffer, and a solution of oxidized compounds. The protein-carbohydrate system was produced by mixing the following reagents: histone, gum arabic, acetate buffer, and a solution of oxidized compounds. Results indicated that the stabilization of coacervate systems occurs when stabilizing low-molecular-weight compounds of the type of quinones and the imino form ofmore » o-dianisidine are included in them. These compounds may be formed under the action of physical factors without the participation of enzymes. (HLW)« less

Gas Phase Reactivity of Carboxylates with N-Hydroxysuccinimide Esters

PubMed Central

Peng, Zhou; McGee, William M.; Bu, Jiexun; Barefoot, Nathan Z.; McLuckey, Scott A.

2015-01-01

N-hydroxysuccinimide (NHS) esters have been used for gas phase conjugation reactions with peptides at nucleophilic sites, such as primary amines (N-terminus, ε-amine of lysine) or guanidines, by forming amide bonds through a nucleophilic attack on the carbonyl carbon. The carboxylate has recently been found to also be a reactive nucleophile capable of initiating a similar nucleophilic attack to form a labile anhydride bond. The fragile bond is easily cleaved, resulting in an oxygen transfer from the carboxylate-containing species to the reagent, nominally observed as a water transfer. This reactivity is shown for both peptides and non-peptidic species. Reagents isotopically labeled with O18 were used to confirm reactivity. This constitutes an example of distinct differences in reactivity of carboxylates between the gas-phase, where they are shown to be reactive, and the solution-phase, where they are not regarded as reactive with NHS esters. PMID:25338221

Chemo-enzymatic Synthesis of Clickable Xylo-oligosaccharide Monomers from Hardwood 4-O-Methylglucuronoxylan.

PubMed

MacCormick, Benjamin; Vuong, Thu V; Master, Emma R

2018-02-12

A chemo-enzymatic pathway was developed to transform 4-O-methylglucuronic acid (MeGlcpA) containing xylo-oligosaccharides from beechwood into clickable monomers capable of polymerizing at room temperature and in aqueous conditions to form unique polytriazoles. While the gluco-oligosaccharide oxidase (GOOX) from Sarocladium strictum was used to oxidize C6-propargylated oligosaccharides, the acid-amine coupling reagents 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide (EDAC) and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) were employed and compared for their ability to append click functionalities to carboxylic acid groups of enzyme-treated oligosaccharides. While DMT-MM was a superior coupling reagent for this application, a triazine side product was observed during C-1 amidation. Resulting bifunctional xylo-oligosaccharide monomers were polymerized using a Cu(I) catalyst, forming a soft gel which was characterized by 1 H NMR, confirming the triazole product.

Photoluminescent silicon nanocrystals with chlorosilane surfaces - synthesis and reactivity

NASA Astrophysics Data System (ADS)

Höhlein, Ignaz M. D.; Kehrle, Julian; Purkait, Tapas K.; Veinot, Jonathan G. C.; Rieger, Bernhard

2014-12-01

We present a new efficient two-step method to covalently functionalize hydride terminated silicon nanocrystals with nucleophiles. First a reactive chlorosilane layer was formed via diazonium salt initiated hydrosilylation of chlorodimethyl(vinyl)silane which was then reacted with alcohols, silanols and organolithium reagents. With organolithium compounds a side reaction is observed in which a direct functionalization of the silicon surface takes place.We present a new efficient two-step method to covalently functionalize hydride terminated silicon nanocrystals with nucleophiles. First a reactive chlorosilane layer was formed via diazonium salt initiated hydrosilylation of chlorodimethyl(vinyl)silane which was then reacted with alcohols, silanols and organolithium reagents. With organolithium compounds a side reaction is observed in which a direct functionalization of the silicon surface takes place. Electronic supplementary information (ESI) available: Detailed experimental procedures and additional NMR, PL, EDX, DLS and TEM data. See DOI: 10.1039/C4NR05888G

Validated spectroflurimetric determination of some H1 receptor antagonist drugs in pharmaceutical preparations through charge transfer complexation.

PubMed

el-Din, Mohie K Sharaf; Ibrahim, Fawzia; Eid, Manal I; Wahba, Mary E K

2012-01-01

A validated simple, rapid, and selective spectrofluorimetric method was developed for the determination of some antihistaminic H(1) receptor antagonist drugs namely ebastine (EBS), cetirizine dihydrochloride (CTZ), and fexofenadine hydrochloride (FXD). The method is based on the reaction of the cited drugs with some Π acceptors namely p-chloranilic acid (CLA), tetracyanoethylene (TCNE), and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) to give highly fluorescent derivatives. The fluorescence intensity-concentration plots were rectilinear over the concentration ranges of 0.2-3.0, 0.2-2.5 and 0.15-2.0 μg/ml for EBS with CLA, DDQ, and TCNE respectively; 0.5-7.0, 0.5-6.0, and 0.2-4.0 μg/ml for CTZ with the previously mentioned reagents, and 0.2-3.5, 0.5-6.0, and 0.2-3.5 μg/ml for FXD. The factors affecting the formation of the reaction products were carefully studied and optimized. The method was applied for the determination of the studied drugs in their dosage forms. The results obtained were in good agreement with those obtained by the comparison methods. Reactions Stoichiometries of the complexes formed between the studied drugs and Π acceptors were defined by the Job's method of the continuous variation and found in 1:1 in all cases.

Matrix isolation infrared spectra of O2 and N2 insertion reactions with atomic uranium

NASA Astrophysics Data System (ADS)

Hunt, Rodney D.; Toth, L. Mac; Yustein, Jason T.; Andrews, Lester

1993-10-01

Laser ablation of refractory metals can be an effective source of vapor for matrix isolation IR studies. This combination of techniques was used for the first time to study the mechanisms of U vapor reactions with atmospheric components. U atoms and O2 were codeposited with excess Ar at 12 K. The dominant codeposition products were UO2 and UO3. In contrast, the UO yield was always small because UO2 is formed by an insertion mechanism. This mechanism was verified in the 16O2/18O2 experiments which failed to produce 16OU18O. The effects of UV photolysis and matrix annealings were also examined. The U atoms and O2 reaction requires little or no activation energy since UO2 was formed from cold reagents. New charge-transfer species, (UO2+2)(O2-2) and (UO+2)(O-2), and a weak complex, UO3-O2, were primarily produced under conditions which favored further O2 reactions. Similar U atom and N2 experiments produced only linear NUN which is also produced by an insertion mechanism. This U reaction represents the first time that atom was observed breaking and inserting into the triple bond of N2. Photolysis dramatically increased the NUN yield by 3-fold. Matrix annealings produced weak UN2-N2 and UN2-2N2 complexes.

ANALYTICAL METHODS AND QUALITY ASSURANCE CRITERIA FOR LC/ES/MS DETERMINATION OF PFOS IN FISH

EPA Science Inventory

PFOS, perfluorooctanesulfonate, has recently received much attention from environmental researchers. Previous analytical methods were based upon complexing with a strong ion-pairing reagent and extraction into MTBE. Detection was done on a concentrate using negative ion LC/ES/MS/...

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations.

PubMed

Hassan, Wafaa S; El-Henawee, Magda M; Gouda, Ayman A

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at lambda(max) 470nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70microgmL(-1) for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Hassan, Wafaa S.; El-Henawee, Magda M.; Gouda, Ayman A.

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at λmax 470 nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426 nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70 μg mL -1 for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

Uncovering the Roles of Oxygen in Cr(III) Photoredox Catalysis.

PubMed

Higgins, Robert F; Fatur, Steven M; Shepard, Samuel G; Stevenson, Susan M; Boston, David J; Ferreira, Eric M; Damrauer, Niels H; Rappé, Anthony K; Shores, Matthew P

2016-04-27

A combined experimental and theoretical investigation aims to elucidate the necessary roles of oxygen in photoredox catalysis of radical cation based Diels-Alder cycloadditions mediated by the first-row transition metal complex [Cr(Ph2phen)3](3+), where Ph2phen = bathophenanthroline. We employ a diverse array of techniques, including catalysis screening, electrochemistry, time-resolved spectroscopy, and computational analyses of reaction thermodynamics. Our key finding is that oxygen acts as a renewable energy and electron shuttle following photoexcitation of the Cr(III) catalyst. First, oxygen quenches the excited Cr(3+)* complex; this energy transfer process protects the catalyst from decomposition while preserving a synthetically useful 13 μs excited state and produces singlet oxygen. Second, singlet oxygen returns the reduced catalyst to the Cr(III) ground state, forming superoxide. Third, the superoxide species reduces the Diels-Alder cycloadduct radical cation to the final product and reforms oxygen. We compare the results of these studies with those from cycloadditions mediated by related Ru(II)-containing complexes and find that the distinct reaction pathways are likely part of a unified mechanistic framework where the photophysical and photochemical properties of the catalyst species lead to oxygen-mediated photocatalysis for the Cr-containing complex but radical chain initiation for the Ru congener. These results provide insight into how oxygen can participate as a sustainable reagent in photocatalysis.

Application of dual-cloud point extraction for the trace levels of copper in serum of different viral hepatitis patients by flame atomic absorption spectrometry: A multivariate study

NASA Astrophysics Data System (ADS)

Arain, Salma Aslam; Kazi, Tasneem G.; Afridi, Hassan Imran; Abbasi, Abdul Rasool; Panhwar, Abdul Haleem; Naeemullah; Shanker, Bhawani; Arain, Mohammad Balal

2014-12-01

An efficient, innovative preconcentration method, dual-cloud point extraction (d-CPE) has been developed for the extraction and preconcentration of copper (Cu2+) in serum samples of different viral hepatitis patients prior to couple with flame atomic absorption spectrometry (FAAS). The d-CPE procedure was based on forming complexes of elemental ions with complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN), and subsequent entrapping the complexes in nonionic surfactant (Triton X-114). Then the surfactant rich phase containing the metal complexes was treated with aqueous nitric acid solution, and metal ions were back extracted into the aqueous phase, as second cloud point extraction stage, and finally determined by flame atomic absorption spectrometry using conventional nebulization. The multivariate strategy was applied to estimate the optimum values of experimental variables for the recovery of Cu2+ using d-CPE. In optimum experimental conditions, the limit of detection and the enrichment factor were 0.046 μg L-1 and 78, respectively. The validity and accuracy of proposed method were checked by analysis of Cu2+ in certified sample of serum (CRM) by d-CPE and conventional CPE procedure on same CRM. The proposed method was successfully applied to the determination of Cu2+ in serum samples of different viral hepatitis patients and healthy controls.

Solid phase extraction and spectrophotometric determination of Au(III) with 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine.

PubMed

Hu, Qiufen; Chen, Xiubin; Yang, Xiangjun; Huang, Zhangjie; Chen, Jing; Yang, Guangyu

2006-04-01

A new chromogenic reagent, 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine (HNATR) was synthesized. A highly sensitive, selective and rapid method for the determination microg l(-1) level of Au(III) based on the rapid reaction of Au(III) with HNATR and the solid phase extraction of the colored complex with a reversed phase polymer-based C(18) cartridge have been developed. The HNATR reacted with Au(III) to form a red complex of a molar ratio 1:2 (Au(III) to HNATR) in the presence of 0.05 - 0.5 mol l(-1) of phosphoric acid solution and emulsifier-OP medium. This complex was enriched by the solid phase extraction with a polymer-based C(18) cartridge. The enrichment factor of 100 was achieved. The molar absorptivity of the complex is 1.37 x 10(5) l mol(-1) cm(-1) at 520 nm in the measured solution. The system obeys Beer's law in the range of 0.01 - 3 microg ml(-1). The relative standard deviation for eleven replicates sample of 0.5 microg l(-1) level is 2.18%. The detection limit, based on the three times of standard deviation is 0.02 microg l(-1) in the original sample. This method was applied to the determination of gold in water and ore with good results.

An insight into the metal coordination and spectroscopic properties of artistic Fe and Fe/Cu logwood inks

NASA Astrophysics Data System (ADS)

Bronzato, Maddalena; Zoleo, Alfonso; Biondi, Barbara; Centeno, Silvia A.

2016-01-01

Fe- and Fe/Cu-based logwood inks were synthesized following recipes in nineteenth and early twentieth century manuals and were characterized by EPR, ESI-MS, FTIR, and Raman spectroscopies. This multi-technique approach allowed us to shed light on the structures of the complexes responsible for the inks' colors and to obtain vibrational signatures that can be used to identify the different inks in works of art and in historic documents. Information on the nature and chemical properties of the complexes formed between a dye and a mordant is important as these determine, at least in part, their lightfastness. EPR permitted to determine the coordination environment of the metallic ions. The results of the ESI-MS analysis demonstrated, for the first time, the breakdown of the hematein molecule during the ink preparation, and that the colorants are formed by the complexation of the metallic ions by hematein breakdown products, mainly catechol and/or bicyclic compounds. The FTIR spectra obtained were found to be dominated by bands due to the binding medium and sulfates used as reagents. The Raman analysis showed that the characteristic features for the different inks studied depend on the historic recipe used, attesting to the challenges that their identification and characterization in works of art present. In the Raman spectra of the inks applied on paper, broadening of bands in the 750-400 cm- 1 range are observed when compared to the spectra of the inks' powders, possibly due to the interaction of the compounds with the cellulose in the substrate.

Ascorbic acid/Fe@Fe2O3: A highly efficient combined Fenton reagent to remove organic contaminants.

PubMed

Hou, Xiaojing; Huang, Xiaopeng; Ai, Zhihui; Zhao, Jincai; Zhang, Lizhi

2016-06-05

In this study, we demonstrate that the combination of ascorbic acid and Fe@Fe2O3 core-shell nanowires (AA/Fe@Fe2O3) offers a highly efficient Fenton reagent. This combined Fenton reagent exhibited extremely high activity on the decomposition of H2O2 to produce OH for the degradation of various organic contaminants, including rhodamine B, methylene blue, alachlor, atrazine, siduron, lincomycin, and chloroamphenicol. The contaminant degradation constants in the AA/Fe@Fe2O3/H2O2 Fenton systems were 38-53 times higher than those in the conventional homogeneous Fenton system (Fe(II)/H2O2) at pH 3.8. Moreover, the OH generation rate constant in the AA/Fe@Fe2O3/H2O2 Fenton system was 1-3 orders of magnitudes greater than those of heterogeneous Fenton systems developed with other iron-containing materials (α-FeOOH, α-Fe2O3, FeOCl, and so on). The high activity of AA/Fe@Fe2O3 was attributed to the effective Fe(III)/Fe(II) cycle and the iron-ascorbate complex formation to stabilize ferrous ions with desirable and steady concentrations. During the AA/Fe@Fe2O3/H2O2 Fenton process, ascorbic acid served as a reducing and complexing reagent, enabling the reuse of Fe@Fe2O3 nanowires. We systematically investigated the alachlor and ascorbic acid degradation and found that they could be effectively degraded in the AA/Fe@Fe2O3/H2O2 system, accompanying with 100% of dechlorination and 92% of denitrification. This study sheds light on the importance of Fe(III)/Fe(II) cycle for the design of high efficient Fenton system and provides an alternative pathway for the organic contaminants removal. Copyright © 2016 Elsevier B.V. All rights reserved.

Demonstration of elastic fibres with reagents for detection of magnesium.

PubMed Central

Müller, W; Firsching, R

1991-01-01

Investigation of elastic fibres in various human and animal tissues with the reagents quinalizarin, magneson II, and titan yellow for the detection of magnesium revealed striking positive results. After pretreatment of skin and ligamentum flavum with elastase the tests were negative. The results support the supposition that the amount of magnesium in elastic fibres is sufficient for histochemical detection. It is speculated that the marked chelate-forming property of magnesium, or its antagonistic function to calcium, is associated with the elastic property of the fibres. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 PMID:1711022

Diastereoselective Radical‐Type Cyclopropanation of Electron‐Deficient Alkenes Mediated by the Highly Active Cobalt(II) Tetramethyltetraaza[14]annulene Catalyst

PubMed Central

Chirila, Andrei; Gopal Das, Braja; Paul, Nanda D.

2017-01-01

Abstract A new protocol for the catalytic synthesis of cyclopropanes using electron‐deficient alkenes is presented, which is catalysed by a series of affordable, easy to synthesise and highly active substituted cobalt(II) tetraaza[14]annulenes. These catalysts are compatible with the use of sodium tosylhydrazone salts as precursors to diazo compounds in one‐pot catalytic transformations to afford the desired cyclopropanes in almost quantitative yields. The reaction takes advantage of the metalloradical character of the Co complexes to activate the diazo compounds. The reaction is practical and fast, and proceeds from readily available starting materials. It does not require the slow addition of diazo reagents or tosylhydrazone salts or heating and tolerates many solvents, which include protic ones such as MeOH. The CoII complexes derived from the tetramethyltetraaza[14]annulene ligand are easier to prepare than cobalt(II) porphyrins and present a similar catalytic carbene radical reactivity but are more active. The reaction proceeds at 20 °C in a matter of minutes and even at −78 °C in a few hours. The catalytic system is robust and can operate with either the alkene or the diazo reagent as the limiting reagent, which inhibits the dimerisation of diazo compounds totally. The protocol has been applied to synthesise a variety of substituted cyclopropanes. High yields and selectivities were achieved for various substrates with an intrinsic preference for trans cyclopropanes. PMID:28529668

Optimizing Cationic and Neutral Lipids for Efficient Gene Delivery at High Serum Content

PubMed Central

Majzoub, Ramsey N.; Hwu, Yeu-kuang; Liang, Keng S.; Leal, Cecília; Safinya, Cyrus R.

2014-01-01

Background Cationic liposome (CL)-DNA complexes are promising gene delivery vectors with potential applications in gene therapy. A key challenge in creating CL-DNA complexes for applications is that their transfection efficiency (TE) is adversely affected by serum. In particular, little is known about the effects of high serum contents on TE even though this may provide design guidelines for applications in vivo. Methods We prepared CL-DNA complexes in which we varied the neutral lipid (DOPC, glycerol-monooleate (GMO), cholesterol), the headgroup charge and chemical structure of the cationic lipid, and the ratio of neutral to cationic lipid; we then measured the TE of these complexes as a function of serum content and assessed their cytotoxicity. We tested selected formulations in two human cancer cell lines (M21/melanoma and PC-3/prostate cancer). Results In the absence of serum, all CL-DNA complexes of custom-synthesized multivalent lipids show high TE. Certain combinations of multivalent lipids and neutral lipids, such as MVL5(5+)/GMO-DNA complexes or complexes based on the dendritic-headgroup lipid TMVLG3(8+) exhibited high TE both in the absence and presence of serum. Although their TE still dropped to a small extent in the presence of serum, it reached or surpassed that of benchmark commercial transfection reagents, in particular at high serum content. Conclusions Two-component vectors (one multivalent cationic lipid and one neutral lipid) can rival or surpass benchmark reagents at low and high serum contents (up to 50%, v/v). We suggest guidelines for optimizing the serum resistance of CL-DNA complexes based on a given cationic lipid. PMID:24753287

77 FR 33165 - Pure Magnesium in Granular Form From the People's Republic of China: Final Results of Expedited...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-05

... Department is aware used to make such excluded reagents are: lime, calcium metal, calcium silicon, calcium.../mischmetal, cryolite, silica/fly ash, magnesium oxide, periclase, ferroalloys, dolomitic lime, and colemanite...

One-step displacement dispersive liquid-liquid microextraction coupled with graphite furnace atomic absorption spectrometry for the selective determination of methylmercury in environmental samples.

PubMed

Liang, Pei; Kang, Caiyan; Mo, Yajun

2016-01-01

A novel method for the selective determination of methylmercury (MeHg) was developed by one-step displacement dispersive liquid-liquid microextraction (D-DLLME) coupled with graphite furnace atomic absorption spectrometry. In the proposed method, Cu(II) reacted with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex, which was used as the chelating agent instead of DDTC for the dispersive liquid-liquid microextraction (DLLME) of MeHg. Because the stability of MeHg-DDTC is higher than that of Cu-DDTC, MeHg can displace Cu from the Cu-DDTC complex and be preconcentrated in a single DLLME procedure. MeHg could be extracted into the extraction solvent phase at pH 6 while Hg(II) remained in the sample solution. Potential interference from co-existing metal ions with lower DDTC complex stability was largely eliminated without the need of any masking reagent. Under the optimal conditions, the limit of detection of this method was 13.6ngL(-1) (as Hg), and an enhancement factor of 81 was achieved with a sample volume of 5.0mL. The proposed method was successfully applied for the determination of trace MeHg in some environmental samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

On the asymmetric autocatalysis of aldol reactions: The case of 4-nitrobenzaldehyde and acetone. A critical appraisal with a focus on theory.

PubMed

Romero-Fernández, M Pilar; Babiano, Reyes; Cintas, Pedro

2018-04-01

Under neutral conditions, spontaneous mirror symmetry breaking has been occasionally reported for aldol reactions starting from achiral reagents and conditions. Chiral induction might be interpreted in terms of autocatalysis exerted by chiral mono-aldol or bis-aldol products as source of initial enantiomeric excesses, which may account for such experimental observations. We describe here a thorough Density Functional Theory (DFT) study on this complex and otherwise difficult problem, which provides some insights into this phenomenon. The picture adds further rationale to an in-depth analysis by Moyano et al, who showed the isolation and characterization of bis-aldol adducts and their participation in a complex network of reversible steps. However, the lack of enantiodiscrimination (ees vanish rapidly in solution) suggests, according to the present results, a weak association in complexes formed by the catalysts and substrates. The latter would also be consistent with almost flat transition states having similar heights for competitive catalyst-bound transition structures (actually, we were unable to locate them at the level explored). Overall, neither autocatalysis as once conjectured nor mutual inhibition of enantiomers appears to be operating mechanisms. Asymmetric amplification in early stages harnessing unavoidable enantiomeric imbalances in reaction mixtures of chiral products represents a plausible interpretation. © 2018 Wiley Periodicals, Inc.

Tannin structural elucidation and quantitative ³¹P NMR analysis. 1. Model compounds.

PubMed

Melone, Federica; Saladino, Raffaele; Lange, Heiko; Crestini, Claudia

2013-10-02

Tannins and flavonoids are secondary metabolites of plants that display a wide array of biological activities. This peculiarity is related to the inhibition of extracellular enzymes that occurs through the complexation of peptides by tannins. Not only the nature of these interactions, but more fundamentally also the structure of these heterogeneous polyphenolic molecules are not completely clear. This first paper describes the development of a new analytical method for the structural characterization of tannins on the basis of tannin model compounds employing an in situ labeling of all labile H groups (aliphatic OH, phenolic OH, and carboxylic acids) with a phosphorus reagent. The ³¹P NMR analysis of ³¹P-labeled samples allowed the unprecedented quantitative and qualitative structural characterization of hydrolyzable tannins, proanthocyanidins, and catechin tannin model compounds, forming the foundations for the quantitative structural elucidation of a variety of actual tannin samples described in part 2 of this series.

Forging Unsupported Metal-Boryl Bonds with Icosahedral Carboranes.

PubMed

Saleh, Liban M A; Dziedzic, Rafal M; Khan, Saeed I; Spokoyny, Alexander M

2016-06-13

In contrast to the plethora of metal-catalyzed cross-coupling methods available for the installation of functional groups on aromatic hydrocarbons, a comparable variety of methods are currently not available for icosahedral carboranes, which are boron-rich three-dimensional aromatic analogues of aryl groups. Part of this is due to the limited understanding of the elementary steps for cross-coupling involving carboranes. Here, we report our efforts in isolating metal-boryl complexes to further our understanding of one of these elementary steps, oxidative addition. Structurally characterized examples of group 10 M-B bonds featuring icosahedral carboranes are completely unknown. Use of mercurocarboranes as a reagent to deliver M-B bonds saw divergent reactivity for platinum and palladium, with a Pt-B bond being isolated for the former, and a rare Pd-Hg bond being formed for the latter. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extractive-spectrophotometric determination of disopyramide and irbesartan in their pharmaceutical formulation

NASA Astrophysics Data System (ADS)

Abdellatef, Hisham E.

2007-04-01

Picric acid, bromocresol green, bromothymol blue, cobalt thiocyanate and molybdenum(V) thiocyanate have been tested as spectrophotometric reagents for the determination of disopyramide and irbesartan. Reaction conditions have been optimized to obtain coloured comoplexes of higher sensitivity and longer stability. The absorbance of ion-pair complexes formed were found to increases linearity with increases in concentrations of disopyramide and irbesartan which were corroborated by correction coefficient values. The developed methods have been successfully applied for the determination of disopyramide and irbesartan in bulk drugs and pharmaceutical formulations. The common excipients and additives did not interfere in their determination. The results obtained by the proposed methods have been statistically compared by means of student t-test and by the variance ratio F-test. The validity was assessed by applying the standard addition technique. The results were compared statistically with the official or reference methods showing a good agreement with high precision and accuracy.

Adsorption of a novel reagent scheme on scheelite and calcite causing an effective flotation separation.

PubMed

Gao, Yuesheng; Gao, Zhiyong; Sun, Wei; Yin, Zhigang; Wang, Jianjun; Hu, Yuehua

2018-02-15

The efficient separation of scheelite from calcium-bearing minerals, especially calcite, remains a challenge in practice. In this work, a novel reagent scheme incorporating a depressant of sodium hexametaphosphate (SHMP) and a collector mixture of octyl hydroxamic acid (HXMA-8) and sodium oleate (NaOl) was employed in both single and mixed binary mineral flotation, and it proved to be highly effective for the separation. Furthermore, the role of the pH value in the separation was evaluated. Additionally, the mechanism of the selective separation was investigated systemically via zeta potential measurements, fourier transform infrared (FTIR) spectroscopy analysis, X-ray photoelectron (XPS) spectroscopy analysis and crystal chemistry calculations. It turns out that the selective chemisorption of SHMP on calcite (in the form of complexation between H 2 PO 4 - /HPO 4 2- and Ca 2+ ) over scheelite is ascribed to the stronger reactivity and higher density of Ca ions on the commonly exposed surfaces of calcite minerals. The intense adsorption of HXMA-8 on scheelite over calcite due to the match of the OO distances in WO 4 2- of scheelite and CONHOH of HXMA-8 holds the key to the successful separation. We were also interested in warranting the previous claim that NaOl is readily adsorbed on both minerals via chemisorption. Our results provided valuable insights into the application of mixed collectors and an effective depressant for flotation separation. Copyright © 2017 Elsevier Inc. All rights reserved.

9-Fluorenylmethyl (Fm) Disulfides: Biomimetic Precursors for Persulfides

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

Park, Chung-Min; Johnson, Brett A.; Duan, Jicheng

Protein S-sulfhydration has been recognized as an important post-translational modification that regulates H2S signals. However, the reactivity and biological implications of the products of S-sulfhydration, i.e. persulfides, are still unclear. This is mainly due to the instability of persulfides and difficulty to access these molecules. Under physiological conditions persulfides mainly exist in anionic forms because of their low pKa values. However, current methods do not allow for the direct generation of persulfide anions under biomimetic and non-H2S conditions. Herein we report the development of a functional disulfide, FmSSPy-A (Fm =9-fluorenylmethyl; Py = pyridinyl). This reagent can effectively convert both smallmore » molecule and protein thiols (-SH) to form –S-SFm adducts under mild conditions. It allows for a H2S-free and biomimetic protocol to generate highly reactive persulfides (in their anionic forms). We also demonstrated the high nucleophilicity of persulfides toward a number of thiol-blocking reagents. This method holds promise for further understanding the chemical biology of persulfides and S-sulfhydration.« less

Polyamidoamine dendrimers as sweeping agent and stationary phase for rapid and sensitive open-tubular capillary electrophoretic determination of heavy metal ions.

PubMed

Ge, Ying; Guo, Yujun; Qin, Weidong

2014-04-01

Polyamidoamine (PAMAM) dendrimer generation 2.5 was synthesized and evaluated as sweeping agent for in-column enrichment and as stationary phase for capillary electrochromatographic separation of heavy metal ions, viz., Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), in a running buffer containing 4-(2-pyridylazo)resorcinol (PAR) as a chromogenic reagent. During experiment, a plug of aqueous PAMAM generation 2.5 solution was first introduced to the capillary, followed by electrokinetic injection of the heavy metal ions under a positive voltage. In this step, PAMAM acted as a sweeping agent, stacking the metal ions on the analyte/PAMAM boundary by forming metal ion-PAMAM complexes. The second preconcentration process occurred when PAR, a stronger ligand, moving toward the injection end under the electric field, reached and re-swept the metal ion-PAMAM zone, forming metal ion-PAR complexes. During separation, the neutral PAMAM moved toward the detector with the electroosmotic flow, dynamically coating the capillary wall, forming stationary phases that affected the separation of the metal ions. Due to the function of PAMAM, the detection sensitivity and resolution of the heavy metal ions improved significantly. Under the optimum conditions, the detection limits were 0.299, 0.184, 0.774, 0.182 and 0.047 μg/L for Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), respectively. The method was successfully applied to the determination of heavy metals in snow, tap and rain water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Biochemist's Toolbox

ERIC Educational Resources Information Center

Bakhtiar, Ray

2013-01-01

Surface plasmon resonance (SPR) spectroscopy is a powerful, label-free technique to monitor noncovalent molecular interactions in real time and in a noninvasive fashion. As a label-free assay, SPR does not require tags, dyes, or specialized reagents (e.g., enzymes-substrate complexes) to elicit a visible or a fluorescence signal. During the last…

A convenient method for determining the concentration of hydrogen in water: use of methylene blue with colloidal platinum

PubMed Central

2012-01-01

A simple titration (oxidimetry) method using a methylene blue-platinum colloid reagent is effective in determining the concentration of hydrogen gas in an aqueous solution. The method performs as effectively as the more complex and expensive electrochemical method. PMID:22273079

Preparation and reactions of enantiomerically pure α-functionalized Grignard reagents.

PubMed

Rayner, Peter J; O'Brien, Peter; Horan, Richard A J

2013-05-29

A strategy for the generation of enantiomerically pure α-functionalized chiral Grignard reagents is presented. The approach involves the synthesis of α-alkoxy and α-amino sulfoxides in ≥99:1 dr and ≥99:1 er via asymmetric deprotonation (s-BuLi/chiral diamine) and trapping with Andersen's sulfinate (menthol derived). Subsequent sulfoxide → Mg exchange (room temperature, 1 min) and electrophilic trapping delivers a range of enantiomerically pure α-alkoxy and α-amino substituted products. Using this approach, either enantiomer of products can be accessed in 99:1 er from asymmetric deprotonation protocols without the use of (-)-sparteine as the chiral ligand. Two additional discoveries are noteworthy: (i) for the deprotonation and trapping with Andersen's sulfinate, there is a lack of stereospecificity at sulfur due to attack of a lithiated intermediate onto the α-alkoxy and α-amino sulfoxides as they form, and (ii) the α-alkoxy-substituted Grignard reagent is configurationally stable at room temperature for 30 min.

Detection of DNA damage by using hairpin molecular beacon probes and graphene oxide.

PubMed

Zhou, Jie; Lu, Qian; Tong, Ying; Wei, Wei; Liu, Songqin

2012-09-15

A hairpin molecular beacon tagged with carboxyfluorescein in combination with graphene oxide as a quencher reagent was used to detect the DNA damage by chemical reagents. The fluorescence of molecular beacon was quenched sharply by graphene oxide; while in the presence of its complementary DNA the quenching efficiency decreased because their hybridization prevented the strong adsorbability of molecular beacon on graphene oxide. If the complementary DNA was damaged by a chemical reagent and could not form intact duplex structure with molecular beacon, more molecular beacon would adsorb on graphene oxide increasing the quenching efficiency. Thus, damaged DNA could be detected based on different quenching efficiencies afforded by damaged and intact complementary DNA. The damage effects of chlorpyrifos-methyl and three metabolites of styrene such as mandelieaeids, phenylglyoxylieaeids and epoxystyrene on DNA were studied as models. The method for detection of DNA damage was reliable, rapid and simple compared to the biological methods. Copyright © 2012 Elsevier B.V. All rights reserved.

The Effect of Treatment with Hydrogen Peroxide and the Mehra-Jackson Reagent on X-ray Diffraction Patterns of Clay Fractions

NASA Astrophysics Data System (ADS)

Sokolova, T. A.; Tolpeshta, I. I.; Izosimova, Yu. G.; Umnova, V. A.; Lashukov, P. V.

2017-12-01

X-ray diffraction patterns of clay fractions from the AEL and EL horizons of pale-podzolic soil before and after treatment with 10% H2O2 and the Mehra-Jackson reagent in different sequences have been examined. The successive treatment with 10% H2O2 and then with the Mehra-Jackson reagent causes dissolution of Al-hydroxy-interlayers in pedogenic chlorites and the respective increase in the content of labile minerals because of a dramatic decrease in pH upon the treatment with hydrogen peroxide. The rate of these changes depends on the degree of chloritization of pedogenic chlorites in the initial samples. The result of the reverse sequence of the treatments of clay fractions (initially with the Mehra-Jackson reagent and then with hydrogen peroxide) is opposite: the chloritization of labile minerals becomes more intensive. It is provided by pH values that do not drop below 7.5 at any treatment stage. At particular stages, pH values favors the mobilization of Al compounds and their subsequent polymerization in the interlayer space of labile structures. We suppose that hydroxyl-aluminosilicate layers may be formed in the interlayer space upon this treatment sequence.

Improved performance of collagen scaffolds crosslinked by Traut's reagent and Sulfo-SMCC.

PubMed

Li, Yiming; He, Qifen; Hu, Xiucheng; Liu, Yun; Cheng, Xiaohui; Li, Xiachen; Deng, Feilong

2017-05-01

Collagen scaffolds are frequently employed for applications in regenerative medicine. In previous studies, we affirmed that Traut's reagent (2-Iminothiolane hydrochloride) and Sulfo-SMCC (4-(N-Maleimidomethyl) cyclohexane-1-carboxylic acid 3-sulpho-N-hydroxysuccinimide ester sodium salt) could covalently bind growth factors on collagen scaffolds. We also observed that crosslinking formed within the collagen scaffolds with excess dosage of Sulfo-SMCC, which improved the biological performance of collagen scaffolds together with growth factors. In order to evaluate changes in capacity caused by crosslinking, Traut's reagent and adjusted different concentrations of Sulfo-SMCC (0.263, 1.315, 2.63 and 5.26 mM) were used to construct collagen scaffolds with differing extents of crosslinking in this study. The results demonstrated that resistance of collagen scaffolds to enzymatic digestion, cellularization and vascularization in vivo were enhanced by the crosslinking procedure. The cell culture studies indicated that the crosslinking procedure did not influence biocompatibility. Moreover, there were no statistical differences in the degradation rate, cellularization or vascularization among 1.315, 2.63 and 5.26 mM crosslinked groups. These results demonstrated that crosslinking collagen scaffolds with an appropriate amount of Traut's reagent and Sulfo-SMCC was an effective and safe method to modify naturally derived collagen scaffolds with notable potential uses in tissue regeneration.

Hydrazine and hydroxylamine as probes for O2-reduction site of mitochondrial cytochrome c oxidase.

PubMed Central

Kubota, T; Yoshikawa, S

1993-01-01

Reactions of hydrazine and hydroxylamine with bovine heart cytochrome c oxidase in the fully reduced state were investigated under anaerobic conditions following the visible-Soret spectral change. Hydrazine gave a sharp band at 575 nm with 20% decrease in the alpha band at 603 nm, and hydroxylamine induced a 2 nm blue-shift for the alpha band without any clear splitting. The Soret band at 443 nm was decreased significantly in intensity, with the concomitant appearance of a shoulder with hydrazine or a peak with hydroxylamine, both near 430 nm. The dependence on pH of the affinity of these reagents for the enzyme indicates that only the deprotonated forms of these reagents bind to the enzyme, suggesting a highly hydrophobic environment of the haem ligand-biding site. These spectral changes were largely removed by addition of cyanide or CO. However, detailed analysis of these spectral changes indicates that hydrazine perturbs the shape of the spectral change induced by cyanide and hydroxylamine perturbs that induced by CO. These results suggest that these aldehyde reagents bind to haem a3 iron as well as to a second site which is most likely to be the formyl group on the haem periphery, and that these two sites bind these reagents anti-cooperatively with each other. PMID:8389138

Schiff and pseudo-Schiff reagents: the reactions and reagents of Hugo Schiff, including a classification of various kinds of histochemical reagents used to detect aldehydes.

PubMed

Dapson, R W

2016-11-01

During the 1860's, Hugo Schiff studied many reactions between amines and aldehydes, some of which have been used in histochemistry, at times without credit to Schiff. Much controversy has surrounded the chemical structures and reaction mechanisms of the compounds involved, but modern analytical techniques have clarified the picture. I review these reactions here. I used molecular modeling software to investigate dyes that contain primary amines representing eight chemical families. All dyes were known to perform satisfactorily for detecting aldehydes in tissue sections. The models verified the correct chemical structures at various points in their reactions and also determined how decolorization occurred in those with "leuco" forms. Decolorization in the presence of sulfurous acid can occur by either adduction or reduction depending on the dye. The final condensation product with aldehyde was determined to be either a C-sulfonic acid adduct on the carbonyl carbon atom or an aminal at the same atom. Based on the various outcomes, I have placed the dyes and their reactions into five categories. Because Hugo Schiff studied the reactions between aldehydes and amines with and without various acids or alcohol, it is only proper to call each of them Schiff reactions that used various types of Schiff reagents.

Polyelectrolyte Complexes of Low Molecular Weight PEI and Citric Acid as Efficient and Nontoxic Vectors for in Vitro and in Vivo Gene Delivery.

PubMed

Giron-Gonzalez, M Dolores; Salto-Gonzalez, Rafael; Lopez-Jaramillo, F Javier; Salinas-Castillo, Alfonso; Jodar-Reyes, Ana Belen; Ortega-Muñoz, Mariano; Hernandez-Mateo, Fernando; Santoyo-Gonzalez, Francisco

2016-03-16

Gene transfection mediated by the cationic polymer polyethylenimine (PEI) is considered a standard methodology. However, while highly branched PEIs form smaller polyplexes with DNA that exhibit high transfection efficiencies, they have significant cell toxicity. Conversely, low molecular weight PEIs (LMW-PEIs) with favorable cytotoxicity profiles display minimum transfection activities as a result of inadequate DNA complexation and protection. To solve this paradox, a novel polyelectrolyte complex was prepared by the ionic cross-linking of branched 1.8 kDa PEI with citric acid (CA). This system synergistically exploits the good cytotoxicity profile exhibited by LMW-PEI with the high transfection efficiencies shown by highly branched and high molecular weight PEIs. The polyectrolyte complex (1.8 kDa-PEI@CA) was obtained by a simple synthetic protocol based on the microwave irradiation of a solution of 1.8 kDa PEI and CA. Upon complexation with DNA, intrinsic properties of the resulting particles (size and surface charge) were measured and their ability to form stable polyplexes was determined. Compared with unmodified PEIs the new complexes behave as efficient gene vectors and showed enhanced DNA binding capability associated with facilitated intracellular DNA release and enhanced DNA protection from endonuclease degradation. In addition, while transfection values for LMW-PEIs are almost null, transfection efficiencies of the new reagent range from 2.5- to 3.8-fold to those of Lipofectamine 2000 and 25 kDa PEI in several cell lines in culture such as CHO-k1, FTO2B hepatomas, L6 myoblasts, or NRK cells, simultaneously showing a negligible toxicity. Furthermore, the 1.8 kDa-PEI@CA polyelectrolyte complexes retained the capability to transfect eukaryotic cells in the presence of serum and exhibited the capability to promote in vivo transfection in mouse (as an animal model) with an enhanced efficiency compared to 25 kDa PEI. Results support the polyelectrolyte complex of LMW-PEI and CA as promising generic nonviral gene carriers.

Switching and optimizing control for coal flotation process based on a hybrid model

PubMed Central

Dong, Zhiyong; Wang, Ranfeng; Fan, Minqiang; Fu, Xiang

2017-01-01

Flotation is an important part of coal preparation, and the flotation column is widely applied as efficient flotation equipment. This process is complex and affected by many factors, with the froth depth and reagent dosage being two of the most important and frequently manipulated variables. This paper proposes a new method of switching and optimizing control for the coal flotation process. A hybrid model is built and evaluated using industrial data. First, wavelet analysis and principal component analysis (PCA) are applied for signal pre-processing. Second, a control model for optimizing the set point of the froth depth is constructed based on fuzzy control, and a control model is designed to optimize the reagent dosages based on expert system. Finally, the least squares-support vector machine (LS-SVM) is used to identify the operating conditions of the flotation process and to select one of the two models (froth depth or reagent dosage) for subsequent operation according to the condition parameters. The hybrid model is developed and evaluated on an industrial coal flotation column and exhibits satisfactory performance. PMID:29040305

Vulnerability of point-of-care test reagents and instruments to environmental stresses: implications for health professionals and developers.

PubMed

Louie, Richard F; Ferguson, William J; Curtis, Corbin M; Vy, John H; Kost, Gerald J

2014-03-01

Strategic integration of point-of-care (POC) diagnostic tools during crisis response can accelerate triage and improve management of victims. Timely differential diagnosis is essential wherever care is provided to rule out or rule in disease, expedite life-saving treatment, and improve utilization of limited resources. POC testing needs to be accurate in any environment in which it is used. Devices are exposed to potentially adverse storage and operating conditions, such as high/low temperature and humidity during emergencies and field rescues. Therefore, characterizing environmental conditions allows technology developers, operators, and responders to understand the broad operational requirements of test reagents, instruments, and equipment in order to improve the quality and delivery of care in complex emergencies, disasters, and austere environmental settings. This review aims to describe the effects of environmental stress on POC testing performance and its impact on decision-making, to describe how to study the effects, and to summarize ways to mitigate the effects of environmental stresses through good laboratory practice, development of robust reagents, and novel thermal packaging solutions.

The effect of reagents mimicking oxidative stress on fibrinogen function.

PubMed

Štikarová, Jana; Kotlín, Roman; Riedel, Tomáš; Suttnar, Jiří; Pimková, Kristýna; Chrastinová, Leona; Dyr, Jan E

2013-01-01

Fibrinogen is one of the plasma proteins most susceptible to oxidative modification. It has been suggested that modification of fibrinogen may cause thrombotic/bleeding complications associated with many pathophysiological states of organism. We exposed fibrinogen molecules to three different modification reagents-malondialdehyde, sodium hypochlorite, and peroxynitrite-that are presented to various degrees in different stages of oxidative stress. We studied the changes in fibrin network formation and platelet interactions with modified fibrinogens under flow conditions. The fastest modification of fibrinogen was caused by hypochlorite. Fibers from fibrinogen modified with either reagent were thinner in comparison with control fibers. We found that platelet dynamic adhesion was significantly lower on fibrinogen modified with malondialdehyde and significantly higher on fibrinogen modified either with hypochlorite or peroxynitrite reflecting different prothrombotic/antithrombotic properties of oxidatively modified fibrinogens. It seems that, in the complex reactions ongoing in living organisms at conditions of oxidation stress, hypochlorite modifies proteins (e.g., fibrinogen) faster and more preferentially than malondialdehyde. It suggests that the prothrombotic effects of prior fibrinogen modifications may outweigh the antithrombotic effect of malondialdehyde-modified fibrinogen in real living systems.

Synthesis of Diiron(I) Dithiolato Carbonyl Complexes.

PubMed

Li, Yulong; Rauchfuss, Thomas B

2016-06-22

Virtually all organosulfur compounds react with Fe(0) carbonyls to give the title complexes. These reactions are reviewed in light of major advances over the past few decades, spurred by interest in Fe2(μ-SR)2(CO)x centers at the active sites of the [FeFe]-hydrogenase enzymes. The most useful synthetic route to Fe2(μ-SR)2(CO)6 involves the reaction of thiols with Fe2(CO)9 and Fe3(CO)12. Such reactions can proceed via mono-, di-, and triiron intermediates. The reactivity of Fe(0) carbonyls toward thiols is highly chemoselective, and the resulting dithiolato complexes are fairly rugged. Thus, many complexes tolerate further synthetic elaboration directed at the organic substituents. A second major route involves alkylation of Fe2(μ-S2)(CO)6, Fe2(μ-SH)2(CO)6, and Li2Fe2(μ-S)2(CO)6. This approach is especially useful for azadithiolates Fe2[(μ-SCH2)2NR](CO)6. Elaborate complexes arise via addition of the FeSH group to electrophilic alkenes, alkynes, and carbonyls. Although the first example of Fe2(μ-SR)2(CO)6 was prepared from ferrous reagents, ferrous compounds are infrequently used, although the Fe(II)(SR)2 + Fe(0) condensation reaction is promising. Almost invariably low-yielding, the reaction of Fe3(CO)12, S8, and a variety of unsaturated substrates results in C-H activation, affording otherwise inaccessible derivatives. Thiones and related C═S-containing reagents are highly reactive toward Fe(0), often giving complexes derived from substituted methanedithiolates and C-H activation.

Reagent Anions for Charge Inversion of Polypeptide/Protein Cations in the Gas Phase

PubMed Central

He, Min; Emory, Joshua F.; McLuckey, Scott A.

2005-01-01

Various reagent anions capable of converting polypeptide cations to anions via ion/ion reactions have been investigated. The major charge inversion reaction channels include multiple proton transfer and adduct formation. Dianions composed of sulfonate groups as the negative charge carriers show essentially exclusive adduct formation in converting protonated peptides and proteins to anions. Dianions composed of carboxylate groups, on the other hand, show far more charge inversion via multiple proton transfer, with the degree of adduct formation dependent upon both the size of the polypeptide and the spacings between carboxylate groups in the dianion. More highly charged carboxylate-containing anions, such as those derived from carboxylate-terminated polyamidoamine half-generation dendrimers show charge inversion to give anion charges as high in magnitude as −4, with the degree of adduct formation being inversely related to dendrimer generation. All observations can be interpreted on the basis of charge inversion taking place via a long-lived chemical complex. The lifetime of this complex is related to the strengths and numbers of the interactions of the reactants in the complex. Calculations with model systems are fully consistent with sulfonate groups giving rise to more stable complexes. The kinetic stability of the complex can also be affected by the presence of electrostatic repulsion if it is multiply charged. In general, this situation destabilizes the complex and reduces the likelihood for observation of adducts. The findings highlight the characteristics of multiply charged anions that play roles in determining the nature of charge inversion products associated with protonated peptides and proteins. PMID:15889906

Technological Aspects of Waterworks Sludge Treatment

NASA Astrophysics Data System (ADS)

Belkanova, M. Yu; Nikolaenko, E. V.; Gevel, D. A.

2017-11-01

The water yielding capacity of the sludge in water-supply network treatment facilities is determined by the water quality in a water source and its treatment technology. The paper studies the sludge of water-supply network treatment facilities formed in the conditions of low turbidity and average water colour index in the water source. Such sludge has a low water yielding capacity and is subject to conditioning. The paper shows the influence of seasonal variations of turbidity, water colour index and temperature of the feed water on the specific sludge filtration resistance. It considers the specific features of sludge formation in different settling basins influencing its water yielding capacity. It is shown that the washwater return performed at one of the blocks of the facilities increases the feed water turbidity and leads to the formation of the sludge easily susceptible to conditioning. The paper studies the following methods of the reagent sludge treatment: polyacrylamide-based flocculant treatment, joint treatment with flocculant and vermiculite filler, lime treatment. The use of vermiculite allows to reduce the required flocculant dose. The author determines optimum doses of reagents allowing to direct the sludge for further mechanical dewatering after conditioning. It is shown that, when the sludge is processed with lime, the filtrate formed at dewatering can be reused as an alkalifying agent, which will allow one to cut the costs for the acquisition of reagents.

Impact of ultrasound on hydrophobic interactions in solutions: ultrasonic retardation of benzoin condensation.

PubMed

Hagu, Hannes; Salmar, Siim; Tuulmets, Ants

2007-04-01

Kinetics of the benzoin condensation of benzaldehyde in presence of KCN as the catalyst in water and in ethanol-water binary solutions were investigated without sonication and under ultrasound at 22 kHz. A statistically significant 20% decrease of the rate was observed in water. The retardation effect of ultrasound gradually decreases up to 45 wt% ethanol content. We report an evidence of ultrasonic retardation of reactions and thereby a direct evidence for sonochemical processes in the bulk solution. Ultrasound can disturb solvation of the species in the solution. If breaking down the stabilization of the encounter complexes between the reagents, sonication hinders the reaction while perturbation of the solvent-stabilization of the reagents accelerates the reaction.

Microdetermination of Sucrose in Plasma with the Anthrone Reagent.

DTIC Science & Technology

1979-11-01

polysaccharides . The initial attempts to use it for selective determinations of monosaccharides in a mixture, however, were frustrated by a mutual...disaccharides and polysaccharides are hydrolyzed to form monosaccharides . In addition, water is split off from the latter to form hydroxaldehyde...supernate were then concentrated to dryness at 80 C with a manifold evaporator after which endogenous monosaccharides were destroyed by the addition of

Rational synthesis of normal, abnormal and anionic NHC–gallium alkyl complexes: structural, stability and isomerization insights† †Dedicated to the memory of Paul von R. Schleyer. ‡ ‡Electronic supplementary information (ESI) available: CIF files giving crystallographic results, experimental details and copies of the NMR spectra. CCDC 1405459–1405464. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc02086g

PubMed Central

Uzelac, Marina; Hernán-Gómez, Alberto; Armstrong, David R.; Kennedy, Alan R.

2015-01-01

Advancing the rational design of main-group N-heterocyclic carbene complexes, this study reports the synthesis, X-ray crystallographic and NMR spectroscopic characterisation of a novel series of Ga complexes containing neutral or anionic NHC ligands using the unsaturated carbene IPr (IPr = 1,3-bis-(2,6-di-isopropylphenyl)imidazol-2-ylidene). Starting from normal adduct GaR3·IPr (1) (R = CH2SiMe3), the addition of polar LiR led to the formation of NHC-stabilised gallate species IPr·LiGaR4 (2), resulting from co-complexation of the single-metal species. Contrastingly, reversing the order of addition of these organometallic reagents, by treating unsaturated free IPr, first with LiR followed by GaR3, furnished novel heteroleptic gallate (THF)2Li[:C{[N(2,6-iPr2C6H3)]2CHCGa(CH2SiMe3)3}] (3), which contains an anionic NHC ligand acting as an unsymmetrical bridge between the two metals, coordinating through its abnormal C4 position to Ga and through its normal C2 position to Li. Electrophilic interception studies of 3 using methyl triflate (MeOTf), methanol and imidazolium salt (IMes·HCl) led to the isolation and structural elucidation of the two novel neutral abnormal NHC (aNHC) complexes [CH3C{[N(2,6-iPr2C6H3)]2CHCGa(CH2SiMe3)3}] (4) and aIPr·GaR3 (5) (aIPr = HC{[N(2,6-iPr2C6H3)]2CHC}). These studies disclose the preference of the anionic IPr ligand present in 3 to react with electrophiles via its C2 position, leaving its Ga–C4 bond intact. Abnormal complex 5 can also be accessed by a thermally induced rearrangement of its normal isomer 1. Combining NMR spectroscopic and kinetic studies with DFT calculations, new light has been shed on this intriguing transformation, which suggests that it occurs via a dissociative mechanism, highlighting the importance of the donor ability of the solvent used in these thermal isomerizations as well as the steric bulk of the substituents on the NHC and the Ga reagent. These findings intimate that relief of the steric hindrance around Ga by forming an abnormal complex is a key driving force behind these rearrangements. PMID:29910864

Protein Conformation and Supercharging with DMSO from Aqueous Solution

NASA Astrophysics Data System (ADS)

Sterling, Harry J.; Prell, James S.; Cassou, Catherine A.; Williams, Evan R.

2011-07-01

The efficacy of dimethyl sulfoxide (DMSO) as a supercharging reagent for protein ions formed by electrospray ionization from aqueous solution and the mechanism for supercharging were investigated. Addition of small amounts of DMSO to aqueous solutions containing hen egg white lysozyme or equine myoglobin results in a lowering of charge, whereas a significant increase in charge occurs at higher concentrations. Results from both near-UV circular dichroism spectroscopy and solution-phase hydrogen/deuterium exchange mass spectrometry indicate that DMSO causes a compaction of the native structure of these proteins at low concentration, but significant unfolding occurs at ~63% and ~43% DMSO for lysozyme and myoglobin, respectively. The DMSO concentrations required to denature these two proteins in bulk solution are ~3-5 times higher than the concentrations required for the onset of supercharging, consistent with a significantly increased concentration of this high boiling point supercharging reagent in the ESI droplet as preferential evaporation of water occurs. DMSO is slightly more basic than m-nitrobenzyl alcohol and sulfolane, two other supercharging reagents, based on calculated proton affinity and gas-phase basicity values both at the B3LYP and MP2 levels of theory, and all three of these supercharging reagents are significantly more basic than water. These results provide additional evidence that the origin of supercharging from aqueous solution is the result of chemical and/or thermal denaturation that occurs in the ESI droplet as the concentration of these supercharging reagents increases, and that proton transfer reactivity does not play a significant role in the charge enhancement observed.

Serodiagnosis of infectious mononucleosis with a bovine erythrocyte glycoprotein.

PubMed

Fletcher, M A; Klimas, N G; Latif, Z A; Caldwell, K E

1983-09-01

A glycoprotein from bovine erythrocyte membrane was evaluated in two immunoassays as a reagent for the serodiagnosis of infectious mononucleosis (IM). We previously reported that a partially purified preparation of this glycoprotein, when attached to latex beads, agglutinated in the presence of IM heterophile antibody. In the present study, we used a highly purified form of the glycoprotein both as an agglutinating reagent, covalently bound to latex, and in a solid-phase sandwich-type radioimmunoassay (RIA) for IM antibody detection in a larger population of patients. We tested serum samples from college students with symptoms suggestive of IM with the latex reagent (143 samples) and with the RIA (245 samples). Correlation of these two tests, both with each other and with the classical differentially absorbed, agglutination tests for Paul-Bunnell antibody in IM sera, using fresh sheep or horse cells, was excellent (greater than 97% agreement). The new tests also corresponded in most cases with a rapid, unabsorbed preserved horse erythrocyte slide test. However, in this study of 245 samples, both apparent false-positives (5 samples) and apparent false-negatives (3 samples) were observed with this slide test. In conclusion, we found that the bovine glycoprotein as a reagent can facilitate the diagnosis of IM, giving results comparable to those with erythrocyte agglutination tests on differentially absorbed sera. The advantages are ease and speed of performance (latex test), potential for automation (RIA test), stability and uniformity of the glycoprotein reagent (latex and RIA tests), and most importantly, the ability to use unabsorbed sera (latex and RIA tests).

Sensitive and selective spectrophotometric assay of piroxicam in pure form, capsule and human blood serum samples via ion-pair complex formation.

PubMed

Alizadeh, Nina; Keyhanian, Fereshteh

2014-09-15

A simple, accurate and highly sensitive spectrophotometric method has been developed for the rapid determination of piroxicam (PX) in pure and pharmaceutical formulations. The proposed method involves formation of stable yellow colored ion-pair complexes of the amino derivative (basic nitrogen) of PX with three sulphonphthalein acid dyes namely; bromocresol green (BCG), bromothymol blue (BTB), bromophenol blue (BPB) in acidic medium. The colored species exhibited absorption maxima at 438, 429 and 432 nm with molar absorptivity values of 9.400×10(3), 1.218×10(3) and 1.02×10(4) L mol(-1) cm(-1) for PX-BCG, PX-BTB and PX-BPB complexes, respectively. The effect of optimum conditions via acidity, reagent concentration, time and solvent were studied. The reactions were extremely rapid at room temperature and the absorbance values remained constant for 48h. Beer's law was obeyed with a good correlation coefficient in the concentration ranges 1-100 μg mL(-1) for BCG, BTB complexes and 1-95 μg mL(-1) for BPB complex. The composition ratio of the ion-pair complexes were found to be 1:1 in all cases as established by Job's method. No interference was observed from common additives and excipients which may be present in the pharmaceutical preparations. The proposed method was successfully applied for the determination of PX in capsule and human blood serum samples with good accuracy and precision. Copyright © 2014 Elsevier B.V. All rights reserved.

Biological and Clinical Aspects of Lanthanide Coordination Compounds

PubMed Central

Misra, Sudhindra N.; M., Indira Devi; Shukla, Ram S.

2004-01-01

The coordinating chemistry of lanthanides, relevant to the biological, biochemical and medical aspects, makes a significant contribution to understanding the basis of application of lanthanides, particularly in biological and medical systems. The importance of the applications of lanthanides, as an excellent diagnostic and prognostic probe in clinical diagnostics, and an anticancer material, is remarkably increasing. Lanthanide complexes based X-ray contrast imaging and lanthanide chelates based contrast enhancing agents for magnetic resonance imaging (MRI) are being excessively used in radiological analysis in our body systems. The most important property of the chelating agents, in lanthanide chelate complex, is its ability to alter the behaviour of lanthanide ion with which it binds in biological systems, and the chelation markedly modifies the biodistribution and excretion profile of the lanthanide ions. The chelating agents, especially aminopoly carboxylic acids, being hydrophilic, increase the proportion of their complex excreted from complexed lanthanide ion form biological systems. Lanthanide polyamino carboxylate-chelate complexes are used as contrast enhancing agents for Magnetic Resonance Imaging. Conjugation of antibodies and other tissue specific molecules to lanthanide chelates has led to a new type of specific MRI contrast agents and their conjugated MRI contrast agents with improved relaxivity, functioning in the body similar to drugs. Many specific features of contrast agent assisted MRI make it particularly effective for musculoskeletal and cerebrospinal imaging. Lanthanide-chelate contrast agents are effectively used in clinical diagnostic investigations involving cerebrospinal diseases and in evaluation of central nervous system. Chelated lanthanide complexes shift reagent aided 23Na NMR spectroscopic analysis is used in cellular, tissue and whole organ systems. PMID:18365075

Determination of successive complexation constants in an ionic liquid: complexation of UO(2)(2+) with NO(3)(-) in C(4)-mimTf(2)N studied by UV-Vis spectroscopy.

PubMed

Georg, Sylvia; Billard, Isabelle; Ouadi, Ali; Gaillard, Clotilde; Petitjean, Laetitia; Picquet, Michel; Solov'ev, Vitaly

2010-04-01

The complexation of UO(2)(2+) with NO(3)(-) has been investigated in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by UV-vis spectroscopy at T = 18.5 degrees C. The complexation is evidenced through the appearance of four peaks at 425, 438, 453, and 467 nm. EXAFS data indicate that the trinitrato complex, UO(2)(NO(3))(3)(-), is dominating the speciation for a reagent ratio of [NO(3)(-)]/[UO(2)(2+)] > 3. Assuming three successive complexation steps, the conditional stability constants are calculated, the individual absorption spectra are derived, and a speciation plot is presented.

Complex formation between the protein components of methane monooxygenase from Methylosinus trichosporium OB3b. Identification of sites of component interaction.

PubMed

Fox, B G; Liu, Y; Dege, J E; Lipscomb, J D

1991-01-05

Kinetic, spectroscopic, and chemical evidence for the formation of specific catalytically essential complexes between the three protein components of the soluble form of methane monooxygenase from Methylosinus trichosporium OB3b is reported. The effects of the concentrations of the reductase and component B on the hydroxylation activity of the reconstituted enzyme system has been numerically simulated based on a kinetic model which assumes formation of multiple high affinity complexes with the hydroxylase component during catalysis. The formation of several of these complexes has been directly demonstrated. By using EPR spectroscopy, the binding of approximately 2 mol of component B/mol of hydroxylase (subunit structure (alpha beta gamma)2) is shown to significantly change the electronic environment of the mu-(H/R)-oxo-bridged binuclear iron cluster of the hydroxylase in both the mixed valent (Fe(II).Fe(III)) and fully reduced (Fe(II).Fe(II)) states. Protein-protein complexes between the reductase and component B as well as between the reductase and hydroxylase have been shown to form by monitoring quenching of the tryptophan fluorescence spectrum of either the component B (KD approximately 0.4 microM) or hydroxylase (two binding sites, KDa approximately 10 nM, KDb approximately 8 microM). The observed KD values are in agreement with the best fit values from the kinetic simulation. Through the use of the covalent zero length cross-linking reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), the binding sites of the component B and reductase were shown to be on the hydroxylase alpha and beta subunits, respectively. The alpha and beta subunits of the hydroxylase are cross-linked by EDC suggesting that they are juxtaposed. EDC also caused the rapid loss of the ability of the monomeric component B to stimulate the hydroxylation reaction suggesting that cross-linking of reactive groups on the protein surface had occurred. This effect was inhibited by the presence of hydroxylase and was accompanied by a loss of the ability of the component B to bind to the hydroxylase. Thus, formation of a component B-hydroxylase complex is apparently required for effective catalysis linked to NADH oxidation. When present in concentrations greater than required to saturate the initial hydroxylase complex, component B inhibited both the rate of the enzymic reaction and the cross-linking of the reductase to the hydroxylase. This suggests that a second complex involving component B can form that negatively regulates catalysis by preventing formation of the reductase-hydroxylase complex.

The behavior and importance of lactic acid complexation in Talspeak extraction systems

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

Grimes, Travis S.; Nilsson, Mikael; Nash, Kenneth L.

2008-07-01

Advanced partitioning of spent nuclear fuel in the UREX +la process relies on the TALSPEAK process for separation of fission-product lanthanides from trivalent actinides. The classic TALSPEAK utilizes an aqueous medium of both lactic acid and diethylenetriaminepentaacetic acid and the extraction reagent di(2-ethylhexyl)phosphoric acid in an aromatic diluent. In this study, the specific role of lactic acid and the complexes involved in the extraction of the trivalent actinides and lanthanides have been investigated using {sup 14}C-labeled lactic acid. Our results show that lactic acid partitions between the phases in a complex fashion. (authors)

Chemical analysis kit for the presence of explosives

DOEpatents

Eckels, Joel Del [Livermore, CA; Nunes,; Peter, J [Danville, CA; Alcaraz, Armando [Livermore, CA; Whipple, Richard E [Livermore, CA

2011-05-10

A tester for testing for explosives associated with a test location comprising a first explosives detecting reagent; a first reagent holder, the first reagent holder containing the first explosives detecting reagent; a second explosives detecting reagent; a second reagent holder, the second reagent holder containing the second explosives detecting reagent; a sample collection unit for exposure to the test location, exposure to the first explosives detecting reagent, and exposure to the second explosives detecting reagent; and a body unit containing a heater for heating the sample collection unit for testing the test location for the explosives.

DNA variation of the mammalian major histocompatibility complex reflects genomic diversity and population history

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

Yuhki, Naoya; O'Brien, S.J.

1990-01-01

The major histocompatibility complex (MHC) is a multigene complex of tightly linked homologous genes that encode cell surface antigens that play a key role in immune regulation and response to foreign antigens. In most species, MHC gene products display extreme antigenic polymorphism, and their variability has been interpreted to reflect an adaptive strategy for accommodating rapidly evolving infectious agents that periodically afflict natural populations. Determination of the extent of MHC variation has been limited to populations in which skin grafting is feasible or for which serological reagents have been developed. The authors present here a quantitative analysis of restriction fragmentmore » length polymorphism of MHC class I genes in several mammalian species (cats, rodents, humans) known to have very different levels of genetic diversity based on functional MHC assays and on allozyme surveys. When homologous class I probes were employed, a notable concordance was observed between the extent of MHC restriction fragment variation and functional MHC variation detected by skin grafts or genome-wide diversity estimated by allozyme screens. These results confirm the genetically depauperate character of the African cheetah, Acinonyx jubatus, and the Asiatic lion, Panthera leo persica; further, they support the use of class I MHC molecular reagents in estimating the extent and character of genetic diversity in natural populations.« less

DNA variation of the mammalian major histocompatibility complex reflects genomic diversity and population history.

PubMed Central

Yuhki, N; O'Brien, S J

1990-01-01

The major histocompatibility complex (MHC) is a multigene complex of tightly linked homologous genes that encode cell surface antigens that play a key role in immune regulation and response to foreign antigens. In most species, MHC gene products display extreme antigenic polymorphism, and their variability has been interpreted to reflect an adaptive strategy for accommodating rapidly evolving infectious agents that periodically afflict natural populations. Determination of the extent of MHC variation has been limited to populations in which skin grafting is feasible or for which serological reagents have been developed. We present here a quantitative analysis of restriction fragment length polymorphism of MHC class I genes in several mammalian species (cats, rodents, humans) known to have very different levels of genetic diversity based on functional MHC assays and on allozyme surveys. When homologous class I probes were employed, a notable concordance was observed between the extent of MHC restriction fragment variation and functional MHC variation detected by skin grafts or genome-wide diversity estimated by allozyme screens. These results confirm the genetically depauperate character of the African cheetah, Acinonyx jubatus, and the Asiatic lion, Panthera leo persica; further, they support the use of class I MHC molecular reagents in estimating the extent and character of genetic diversity in natural populations. Images PMID:1967831

Perivascular epithelioid cell tumor (PEComa) of the liver diagnosed by contrast-enhanced ultrasonography.

PubMed

Akitake, Reiko; Kimura, Hiroyuki; Sekoguchi, Satoru; Nakamura, Hideki; Seno, Hiroshi; Chiba, Tsutomu; Fujimoto, Sotaro

2009-01-01

Perivascular epithelioid cell (PEC) is a unique cell which expresses both myogenic and melanocytic markers, and forms PEComa. A 36-year-old woman presented with a 35 mm-diameter liver tumor. MRI showed poor fat component in the tumor. Contrast-enhanced ultrasonography using the newly developed enhancing reagent, Sonazoid, clearly demonstrated early-phase enhancement of the tumor and rapid drainage of the reagent to veins, suggesting a PEComa. Lateral segmentectomy of the liver was performed. Histologically, epithelioid tumor cells around the vessels were immunostained with both HMB-45 and alpha-smooth muscle actin, confirming the diagnosis of PEComa. No recurrence has been found for 18 months following the operation.

Analysis system for characterisation of simple, low-cost microfluidic components

NASA Astrophysics Data System (ADS)

Smith, Suzanne; Naidoo, Thegaran; Nxumalo, Zandile; Land, Kevin; Davies, Emlyn; Fourie, Louis; Marais, Philip; Roux, Pieter

2014-06-01

There is an inherent trade-off between cost and operational integrity of microfluidic components, especially when intended for use in point-of-care devices. We present an analysis system developed to characterise microfluidic components for performing blood cell counting, enabling the balance between function and cost to be established quantitatively. Microfluidic components for sample and reagent introduction, mixing and dispensing of fluids were investigated. A simple inlet port plugging mechanism is used to introduce and dispense a sample of blood, while a reagent is released into the microfluidic system through compression and bursting of a blister pack. Mixing and dispensing of the sample and reagent are facilitated via air actuation. For these microfluidic components to be implemented successfully, a number of aspects need to be characterised for development of an integrated point-of-care device design. The functional components were measured using a microfluidic component analysis system established in-house. Experiments were carried out to determine: 1. the force and speed requirements for sample inlet port plugging and blister pack compression and release using two linear actuators and load cells for plugging the inlet port, compressing the blister pack, and subsequently measuring the resulting forces exerted, 2. the accuracy and repeatability of total volumes of sample and reagent dispensed, and 3. the degree of mixing and dispensing uniformity of the sample and reagent for cell counting analysis. A programmable syringe pump was used for air actuation to facilitate mixing and dispensing of the sample and reagent. Two high speed cameras formed part of the analysis system and allowed for visualisation of the fluidic operations within the microfluidic device. Additional quantitative measures such as microscopy were also used to assess mixing and dilution accuracy, as well as uniformity of fluid dispensing - all of which are important requirements towards the successful implementation of a blood cell counting system.

Identification of monoclonal antibodies cross-reactive with bottlenose dolphin orthologues of the major histocompatibility complex and leukocyte differentiation molecules

USDA-ARS?s Scientific Manuscript database

The slow progress in understanding immunotoxic effects of environmental contaminants and their influence on disease susceptibility and immunopathogenesis of the bottlenose dolphin (Tursiops truncates) and other species of cetaceans, is largely due to lack of monoclonal antibody (mAb) reagents. As re...

Contribution to the photometric determination of small amounts of boron trioxide in glasses

NASA Technical Reports Server (NTRS)

Markova, D.

1985-01-01

The photometric determination for boron trioxide is described in amounts of 0-75 micrograms B2O3 with an azomethin H reagent. The yellow colored complex which occurs in a medium held at a pH of 4.5 was measured in light of a wavelength of 415 nm.

Functional Imaging and Optogenetics in Drosophila

PubMed Central

Simpson, Julie H.; Looger, Loren L.

2018-01-01

Understanding how activity patterns in specific neural circuits coordinate an animal’s behavior remains a key area of neuroscience research. Genetic tools and a brain of tractable complexity make Drosophila a premier model organism for these studies. Here, we review the wealth of reagents available to map and manipulate neuronal activity with light. PMID:29618589

Method for genetic identification of unknown organisms

DOEpatents

Colston, Jr., Billy W.; Fitch, Joseph P.; Hindson, Benjamin J.; Carter, Chance J.; Beer, Neil Reginald

2016-08-23

A method of rapid, genome and proteome based identification of unknown pathogenic or non-pathogenic organisms in a complex sample. The entire sample is analyzed by creating millions of emulsion encapsulated microdroplets, each containing a single pathogenic or non-pathogenic organism sized particle and appropriate reagents for amplification. Following amplification, the amplified product is analyzed.

Advanced, Non-Toxic, Anti-Corrosion, Anti-Fouling and Foul-Release Coatings Based on Covalently Attached Monolayers, Multilayers and Polymers

DTIC Science & Technology

2007-08-08

McCarthy Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003 Electrophilic aromatic substitution reactions...with a fluorinated silane reagent. Reduction of the amide groups with borane-THF (BH 3-THF) complex leads to a 69% conversion of surface amides to the

Chromosome-specific staining to detect genetic rearrangements associated with chromosome 3 and/or chromosome 17

DOEpatents

Gray, Joe W.; Pinkel, Daniel; Kallioniemi, Olli-Pekka; Kallioniemi, Anne; Sakamoto, Masaru

2009-10-06

Methods and compositions for staining based upon nucleic acid sequence that employ nudeic nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

Structure-Activity Relationships for Some Diamine, Triamine and Schiff Base Derivatives and Their Copper(II) Complexes

PubMed Central

Bolos, C. A.; Nikolov, G. St.; Ekateriniadou, L.; Kortsaris, A.; Kyriakidis, D. A.

1998-01-01

Ethylenediamine (en), putrescine (pu), diethylenetriamine (dien), dipropylenetriamine (dpta), spermidine (spmd) and their CuII compounds as well as the Schiff bases with 2-furaldehyde (dienOO), 2- thiophenecarboxaldehyde (dienSS) and pyrrole-2-carboxaldehyde (dienNN) of dien and that of dpta with 2- thiophenecarboxaldehyde (dptaSS), were prepared and characterised. They were tested against Bacillus substilis, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Proteus vulgaris and Xanthomonas campestris as antibacterial reagents, the highest activity being exhibited by Cu(dptaSS)(NO3)2 complex, which acts as antibiotic. In the antiproliferative tests (vs. T47D,L929 and BHK21/c13 cell lines) the best results were obtained with Cu(dptaSS)2+ and Cu(dienSS)2+. Electronic structure calculations gave for dptaSS and dienSS the higher negative charges on the N atoms. The counter-ions (Br-, NO3- and SO42-) play an important role by modulating the reagent's selectivity versus the bacteria [Gram(+) or Gram(-)], but they have no effect on the antiproliferative activity. PMID:18475868

Structure-Activity Relationships for Some Diamine, Triamine and Schiff Base Derivatives and Their Copper(II) Complexes.

PubMed

Bolos, C A; Nikolov, G S; Ekateriniadou, L; Kortsaris, A; Kyriakidis, D A

1998-01-01

Ethylenediamine (en), putrescine (pu), diethylenetriamine (dien), dipropylenetriamine (dpta), spermidine (spmd) and their Cu(II) compounds as well as the Schiff bases with 2-furaldehyde (dienOO), 2- thiophenecarboxaldehyde (dienSS) and pyrrole-2-carboxaldehyde (dienNN) of dien and that of dpta with 2- thiophenecarboxaldehyde (dptaSS), were prepared and characterised. They were tested against Bacillus substilis, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Proteus vulgaris and Xanthomonas campestris as antibacterial reagents, the highest activity being exhibited by Cu(dptaSS)(NO(3))(2) complex, which acts as antibiotic. In the antiproliferative tests (vs. T(47)D,L(929) and BHK(21/c13) cell lines) the best results were obtained with Cu(dptaSS)(2+) and Cu(dienSS)(2+). Electronic structure calculations gave for dptaSS and dienSS the higher negative charges on the N atoms. The counter-ions (Br(-), NO(3) (-) and SO(4) (2-)) play an important role by modulating the reagent's selectivity versus the bacteria [Gram(+) or Gram(-)], but they have no effect on the antiproliferative activity.

ortho-Methoxyphenols as Convenient Oxidative Bioconjugation Reagents with Application to Site-Selective Heterobifunctional Cross-Linkers.

PubMed

ElSohly, Adel M; MacDonald, James I; Hentzen, Nina B; Aanei, Ioana L; El Muslemany, Kareem M; Francis, Matthew B

2017-03-15

The synthesis of complex protein-based bioconjugates has been facilitated greatly by recent developments in chemoselective methods for biomolecular modification. The oxidative coupling of o-aminophenols or catechols with aniline functional groups is chemoselective, mild, and rapid; however, the oxidatively sensitive nature of the electron-rich aromatics and the paucity of commercial sources pose some obstacles to the general use of these reactive strategies. Herein, we identify o-methoxyphenols as air-stable, commercially available derivatives that undergo efficient oxidative couplings with anilines in the presence of periodate as oxidant. Mechanistic considerations informed the development of a preoxidation protocol that can greatly reduce the amount of periodate necessary for effective coupling. The stability and versatility of these reagents was demonstrated through the synthesis of complex protein-protein bioconjugates using a site-selective heterobifunctional cross-linker comprising both o-methoxyphenol and 2-pyridinecarboxaldehyde moieties. This compound was used to link epidermal growth factor to genome-free MS2 viral capsids, affording nanoscale delivery vectors that can target a variety of cancer cell types.

Hemimorphite Ores: A Review of Processing Technologies for Zinc Extraction

NASA Astrophysics Data System (ADS)

Chen, Ailiang; Li, Mengchun; Qian, Zhen; Ma, Yutian; Che, Jianyong; Ma, Yalin

2016-10-01

With the gradual depletion of zinc sulfide ores, exploration of zinc oxide ores is becoming more and more important. Hemimorphite is a major zinc oxide ore, attracting much attention in the field of zinc metallurgy although it is not the major zinc mineral. This paper presents a critical review of the treatment for extraction of zinc with emphasis on flotation, pyrometallurgical and hydrometallurgical methods based on the properties of hemimorphite. The three-dimensional framework structure of hemimorphite with complex linkage of its structural units lead to difficult desilicification before extracting zinc in the many metallurgical technologies. It is found that the flotation method is generally effective in enriching zinc minerals from hemimorphite ores into a high-grade concentrate for recovery of zinc. Pure zinc can be produced from hemimorphite or/and willemite with a reducing reagent, like methane or carbon. Leaching reagents, such as acid and alkali, can break the complex structure of hemimorphite to release zinc in the leached solution without generation of silica gel in the hydrometallurgical process. For optimal zinc extraction, combing flotation with pyrometallurgical or hydrometallurgical methods may be required.

Spectrophotometric determination of substrate-borne polyacrylamide.

PubMed

Lu, Jianhang; Wu, Laosheng

2002-08-28

Polyacrylamides (PAMs) have wide application in many industries and in agriculture. Scientific research and industrial applications manifested a need for a method that can quantify substrate-borne PAM. The N-bromination method (a PAM analytical technique based on N-bromination of amide groups and spectrophotometric determination of the formed starch-triiodide complex), which was originally developed for determining PAM in aqueous solutions, was modified to quantify substrate-borne PAM. In the modified method, the quantity of substrate-borne PAM was converted to a concentration of starch-triiodide complex in aqueous solution that was then measured by spectrophotometry. The method sensitivity varied with substrates due to sorption of reagents and reaction intermediates on the substrates. Therefore, separate calibration for each substrate was required. Results from PAM samples in sand, cellulose, organic matter burnt soils, and clay minerals showed that this method had good accuracy and reproducibility. The PAM recoveries ranged from 95.8% to 103.7%, and the relative standard deviations (n = 4) were <7.5% in all cases. The optimum range of PAM in each sample is 10-80 microg. The technique can serve as an effective tool in improving PAM application and facilitating PAM-related research.

Evolution of C−H Bond Functionalization from Methane to Methodology

PubMed Central

2016-01-01

This Perspective presents the fundamental principles, the elementary reactions, the initial catalytic systems, and the contemporary catalysts that have converted C−H bond functionalization from a curiosity to a reality for synthetic chemists. Many classes of elementary reactions involving transition-metal complexes cleave C−H bonds at typically unreactive positions. These reactions, coupled with a separate or simultaneous functionalization process lead to products containing new C−C, C−N, and C−O bonds. Such reactions were initially studied for the conversion of light alkanes to liquid products, but they have been used (and commercialized in some cases) most often for the synthesis of the more complex structures of natural products, medicinally active compounds, and aromatic materials. Such a change in direction of research in C−H bond functionalization is remarkable because the reactions must occur at an unactivated C−H bond over functional groups that are more reactive than the C−H bond toward classical reagents. The scope of reactions that form C−C bonds or install functionality at an unactivated C−H bond will be presented, and the potential future utility of these reactions will be discussed. PMID:26566092

Effects of the η(5)-C5H4(i)Pr Ligand on the Properties Exhibited by Its Tungsten Nitrosyl Complexes.

PubMed

Fabulyak, Diana; Baillie, Rhett A; Patrick, Brian O; Legzdins, Peter; Rosenfeld, Devon C

2016-02-15

Reaction of Na[η(5)-C5H4(i)Pr] with W(CO)6 in refluxing THF for 4 days generates a solution of Na[(η(5)-C5H4(i)Pr)W(CO)3] that when treated with N-methyl-N-nitroso-p-toluenesulfonamide at ambient temperatures affords (η(5)-C5H4(i)Pr)W(NO)(CO)2 (1) that is isolable in good yield as an analytically pure orange oil. Treatment of 1 with an equimolar amount of I2 in Et2O at ambient temperatures affords (η(5)-C5H4(i)Pr)W(NO)I2 (2) as a dark brown solid in excellent yield. Sequential treatment at low temperatures of 2 with 0.5 equiv of Mg(CH2CMe3)2 and Mg(CH2CH═CMe2)2 in Et2O produces the alkyl allyl complex, (η(5)-C5H4(i)Pr)W(NO)(CH2CMe3)(η(3)-CH2CHCMe2) (3), as a thermally sensitive yellow liquid. Complex 3 may also be synthesized, albeit in low yield, in one vessel at low temperatures by reacting 1 first with 1 equiv of PCl5 and then with the binary magnesium reagents specified above. Interestingly, similar treatment of 1 in Et2O with PCl5 and only 0.5 equiv of Mg(CH2CH═CMe2)2 results in the formation of the unusual complex (η(5)-C5H4(i)Pr)W(NO)(PCl2CMe2CH═CH2)Cl2 (4), which probably is formed via a metathesis reaction of the binary magnesium reagent with (η(5)-C5H4(i)Pr)W(NO)(PCl3)Cl2. The C-D activation of C6D6 by complex 3 has been investigated and compared to that exhibited by its η(5)-C5Me5, η(5)-C5Me4H, and η(5)-C5Me4(n)Pr analogues. Kinetic analyses of the various activations have established that the presence of the η(5)-C5H4(i)Pr ligand significantly increases the rate of the reaction, an outcome that can be attributed to a combination of steric and electronic factors. In addition, mechanistic studies have established that in solution 3 loses neopentane under ambient conditions to generate exclusively the 16e η(2)-diene intermediate complex (η(5)-C5H4(i)Pr)W(NO)(η(2)-CH2═CMeCH═CH2), which then effects the subsequent C-D activations. This behavior contrasts with that exhibited by the η(5)-C5Me5 analogue of 3 which forms both η(2)-diene and η(2)-allene intermediates upon thermolysis. Sixteen-electron (η(5)-C5H4(i)Pr)W(NO)(η(2)-CH2═CMeCH═CH2) has been isolated as its 18e PMe3 adduct. All new organometallic complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of two of them have been established by single-crystal X-ray crystallographic analyses.

Organic Synthesis Using Microwaves and Supported Reagents

EPA Science Inventory

In the electromagnetic radiation region, microwaves (0.3GHz-300GHz) lie between radiowave (Rf) and infrared (IR) frequencies with relatively large wavelengths (1 mm-1 m). Microwaves, non-ionizing radiation incapable of breaking bonds, are a form of energy that manifest as heat t...

Supercharging with Trivalent Metal Ions in Native Mass Spectrometry

PubMed Central

Flick, Tawnya G.; Williams, Evan R.

2012-01-01

Addition of 1.0 mM LaCl3 to aqueous ammonium acetate solutions containing proteins in their folded native forms can result in a significant increase in the molecular ion charging obtained with electrospray ionization as a result of cation adduction. In combination with m-nitrobenzyl alcohol, molecular ion charge states that are greater than the number of basic sites in the protein can be produced from these native solutions, even for lysozyme, which is conformationally constrained by four intramolecular disulfide bonds. Circular dichroism spectroscopy indicates that the conformation of ubiquitin is not measurably affected with up to 1.0 M LaCl3, but ion mobility data indicate that the high charge states that are formed when 1.0 mM LaCl3 is present are more unfolded than the low charge states formed without this reagent. These and other results indicate that the increased charging is a result of La3+ preferentially adducting onto compact or more native-like conformers during ESI and the gas-phase ions subsequently unfolding as a result of increased Coulomb repulsion. Electron capture dissociation of these high charge-state ions formed from these native solutions results in comparable sequence coverage to that obtained for ions formed from denaturing solutions without supercharging reagents, making this method a potentially powerful tool for obtaining structural information in native mass spectrometry. PMID:22948901

Headspace analysis of new psychoactive substances using a Selective Reagent Ionisation-Time of Flight-Mass Spectrometer

PubMed Central

Acton, W. Joe; Lanza, Matteo; Agarwal, Bishu; Jürschik, Simone; Sulzer, Philipp; Breiev, Kostiantyn; Jordan, Alfons; Hartungen, Eugen; Hanel, Gernot; Märk, Lukas; Mayhew, Chris A.; Märk, Tilmann D.

2014-01-01

The rapid expansion in the number and use of new psychoactive substances presents a significant analytical challenge because highly sensitive instrumentation capable of detecting a broad range of chemical compounds in real-time with a low rate of false positives is required. A Selective Reagent Ionisation-Time of Flight-Mass Spectrometry (SRI-ToF-MS) instrument is capable of meeting all of these requirements. With its high mass resolution (up to m/Δm of 8000), the application of variations in reduced electric field strength (E/N) and use of different reagent ions, the ambiguity of a nominal (monoisotopic) m/z is reduced and hence the identification of chemicals in a complex chemical environment with a high level of confidence is enabled. In this study we report the use of a SRI-ToF-MS instrument to investigate the reactions of H3O+, O2+, NO+ and Kr+ with 10 readily available (at the time of purchase) new psychoactive substances, namely 4-fluoroamphetamine, methiopropamine, ethcathinone, 4-methylethcathinone, N-ethylbuphedrone, ethylphenidate, 5-MeO-DALT, dimethocaine, 5-(2-aminopropyl)benzofuran and nitracaine. In particular, the dependence of product ion branching ratios on the reduced electric field strength for all reagent ions was investigated and is reported here. The results reported represent a significant amount of new data which will be of use for the development of drug detection techniques suitable for real world scenarios. PMID:25844048

Caspase selective reagents for diagnosing apoptotic mechanisms.

PubMed

Poreba, Marcin; Groborz, Katarzyna; Navarro, Mario; Snipas, Scott J; Drag, Marcin; Salvesen, Guy S

2018-05-10

Apical caspases initiate and effector caspases execute apoptosis. Reagents that can distinguish between caspases, particularly apical caspases-8, 9, and 10 are scarce and generally nonspecific. Based upon a previously described large-scale screen of peptide-based caspase substrates termed HyCoSuL, we sought to develop reagents to distinguish between apical caspases in order to reveal their function in apoptotic cell death paradigms. To this end, we selected tetrapeptide-based sequences that deliver optimal substrate selectivity and converted them to inhibitors equipped with a detectable tag (activity-based probes-ABPs). We demonstrate a strong relationship between substrate kinetics and ABP kinetics. To evaluate the utility of selective substrates and ABPs, we examined distinct apoptosis pathways in Jurkat T lymphocyte and MDA-MB-231 breast cancer lines triggered to undergo cell death via extrinsic or intrinsic apoptosis. We report the first highly selective substrate appropriate for quantitation of caspase-8 activity during apoptosis. Converting substrates to ABPs promoted loss-of-activity and selectivity, thus we could not define a single ABP capable of detecting individual apical caspases in complex mixtures. To overcome this, we developed a panel strategy utilizing several caspase-selective ABPs to interrogate apoptosis, revealing the first chemistry-based approach to uncover the participation of caspase-8, but not caspase-9 or -10 in TRAIL-induced extrinsic apoptosis. We propose that using select panels of ABPs can provide information regarding caspase-8 apoptotic signaling more faithfully than can single, generally nonspecific reagents.

Development Of Antibody-Based Fiber-Optic Sensors

NASA Astrophysics Data System (ADS)

Tromberg, Bruce J.; Sepaniak, Michael J.; Vo-Dinh, Tuan

1988-06-01

The speed and specificity characteristic of immunochemical complex formation has encouraged the development of numerous antibody-based analytical techniques. The scope and versatility of these established methods can be enhanced by combining the principles of conventional immunoassay with laser-based fiber-optic fluorimetry. This merger of spectroscopy and immunochemistry provides the framework for the construction of highly sensitive and selective fiber-optic devices (fluoroimmuno-sensors) capable of in-situ detection of drugs, toxins, and naturally occurring biochemicals. Fluoroimmuno-sensors (FIS) employ an immobilized reagent phase at the sampling terminus of a single quartz optical fiber. Laser excitation of antibody-bound analyte produces a fluorescence signal which is either directly proportional (as in the case of natural fluorophor and "antibody sandwich" assays) or inversely proportional (as in the case of competitive-binding assays) to analyte concentration. Factors which influence analysis time, precision, linearity, and detection limits include the nature (solid or liquid) and amount of the reagent phase, the method of analyte delivery (passive diffusion, convection, etc.), and whether equilibrium or non-equilibrium assays are performed. Data will be presented for optical fibers whose sensing termini utilize: (1) covalently-bound solid antibody reagent phases, and (2) membrane-entrapped liquid antibody reagents. Assays for large-molecular weight proteins (antigens) and small-molecular weight, carcinogenic, polynuclear aromatics (haptens) will be considered. In this manner, the influence of a system's chemical characteristics and measurement requirements on sensor design, and the consequence of various sensor designs on analytical performance will be illustrated.

A Molecular Toolbox to Engineer Site-Specific DNA Replication Perturbation.

PubMed

Larsen, Nicolai B; Hickson, Ian D; Mankouri, Hocine W

2018-01-01

Site-specific arrest of DNA replication is a useful tool for analyzing cellular responses to DNA replication perturbation. The E. coli Tus-Ter replication barrier can be reconstituted in eukaryotic cells as a system to engineer an unscheduled collision between a replication fork and an "alien" impediment to DNA replication. To further develop this system as a versatile tool, we describe a set of reagents and a detailed protocol that can be used to engineer Tus-Ter barriers into any locus in the budding yeast genome. Because the Tus-Ter complex is a bipartite system with intrinsic DNA replication-blocking activity, the reagents and protocols developed and validated in yeast could also be optimized to engineer site-specific replication fork barriers into other eukaryotic cell types.

Synergy Effects in the Chemical Synthesis and Extensions of Multicomponent Reactions (MCRs)-The Low Energy Way to Ultra-Short Syntheses of Tailor-Made Molecules.

PubMed

Eckert, Heiner

2017-02-25

Several novel methods, catalysts and reagents have been developed to improve organic synthesis. Synergistic effects between reactions, reagents and catalysts can lead to minor heats of reaction and occur as an inherent result of multicomponent reactions (MCRs) and their extensions. They enable syntheses to be performed at a low energy level and the number of synthesis steps to be drastically reduced in comparison with 'classical' two-component reactions, fulfilling the rules of Green Chemistry . The very high potential for variability, diversity and complexity of MCRs additionally generates an extremely diverse range of products, thus bringing us closer to the aim of being able to produce tailor-made and extremely low-cost materials, drugs and compound libraries.

Biomimetic Modeling of Copper Complexes: A Study of Enantioselective Catalytic Oxidation on D-(+)-Catechin and L-( − )-Epicatechin with Copper Complexes

PubMed Central

Mutti, Francesco G.; Pievo, Roberta; Sgobba, Maila; Gullotti, Michele; Santagostini, Laura

2008-01-01

The biomimetic catalytic oxidations of the dinuclear and trinuclear copper(II) complexes versus two catechols, namely, D-(+)-catechin and L-( − )-epicatechin to give the corresponding quinones are reported. The unstable quinones were trapped by the nucleophilic reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH), and have been calculated the molar absorptivities of the different quinones. The catalytic efficiency is moderate, as inferred by kinetic constants, but the complexes exhibit significant enantio-differentiating ability towards the catechols, albeit for the dinuclear complexes, this enantio-differentiating ability is lower. In all cases, the preferred enantiomeric substrate is D-(+)-catechin to respect the other catechol, because of the spatial disposition of this substrate. PMID:18825268

The generation of concentration gradients using electroosmotic flow in micro reactors allowing stereoselective chemical synthesis.

PubMed

Skelton, V; Greenway, G M; Haswell, S J; Styring, P; Morgan, D O; Warrington, B H; Wong, S Y

2001-01-01

The stereoselective control of chemical reactions has been achieved by applying electrical fields in a micro reactor generating controlled concentration gradients of the reagent streams. The chemistry based upon well-established Wittig synthesis was carried out in a micro reactor device fabricated in borosilicate glass using photolithographic and wet etching techniques. The selectivity of the cis (Z) to trans (E) isomeric ratio in the product synthesised was controlled by varying the applied voltages to the reagent reservoirs within the micro reactor. This subsequently altered the relative reagent concentrations within the device resulting in Z/E ratios in the range 0.57-5.21. By comparison, a traditional batch method based on the same reaction length, concentration, solvent and stoichiometry (i.e., 1.0:1.5:1.0 reagent ratios) gave a Z/E in the range 2.8-3.0. However, when the stoichiometric ratios were varied up to ten times as much, the Z/E ratios varied in accordance to the micro reactor i.e., when the aldehyde is in excess, the Z isomer predominates whereas when the aldehyde is in low concentrations, the E isomer is the more favourable form. Thus indicating that localised concentration gradients generated by careful flow control due to the diffusion limited non-turbulent mixing regime within a micro reactor, leads to the observed stereo selectivity for the cis and trans isomers.

Palladium-catalysed electrophilic aromatic C-H fluorination

NASA Astrophysics Data System (ADS)

Yamamoto, Kumiko; Li, Jiakun; Garber, Jeffrey A. O.; Rolfes, Julian D.; Boursalian, Gregory B.; Borghs, Jannik C.; Genicot, Christophe; Jacq, Jérôme; van Gastel, Maurice; Neese, Frank; Ritter, Tobias

2018-02-01

Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.

Direct measurement of total antioxidant capacity of cereals: QUENCHER-CUPRAC method.

PubMed

Tufan, Ayşe Nur; Celik, S Esin; Ozyürek, Mustafa; Güçlü, Kubilay; Apak, Reşat

2013-04-15

Polyphenols in cereal samples are distributed as free, soluble-esterified, and insoluble-bound forms either esterified or etherified to cell wall constituents. In the evaluation of total antioxidant capacity (TAC) of cereals, rather difficult and time-consuming acid, alkaline and enzymatic treatments of residue have been applied to complete the extraction of bound phenolic compounds. Thus, this work is aimed to measure the TAC of cereals (i.e. barley, wheat, rye, oat) by the 'QUENCHER procedure' (involving forced solubilization of bound phenolics by oxidizing TAC reagents) with the direct use of copper(II)-neocuproine (Cu(II)-Nc) reagent of the CUPric Reducing Antioxidant Capacity (CUPRAC) assay. In this novel 'QUENCHER-CUPRAC' method, reaction time and solvent composition parameters were optimized, and the method was applied to cereal samples with CUPRAC reagent dissolved in 1:1 (v/v) ethanol-water mixture. The antioxidant capacities of soluble and insoluble fractions were simultaneously measured to give a hierarchic TAC order of cereals as: barley>rye>oat>wheat. The TAC values of cereals measured by QUENCHER-CUPRAC were higher than those of original QUENCHER method using ABTS(•+) and DPPH reagents. Polyphenolic mixtures in a cellulose matrix gave additive TAC values with QUENCHER-CUPRAC. The proposed method correlated linearly with QUENCHER-ABTS(•+) (r=0.956) and QUENCHER-DPPH (r=0.976). Copyright © 2013 Elsevier B.V. All rights reserved.

9,10-Phenanthrenequinone as a mass-tagging reagent for ultra-sensitive liquid chromatography-tandem mass spectrometry assay of aliphatic aldehydes in human serum.

PubMed

El-Maghrabey, Mahmoud; Kishikawa, Naoya; Kuroda, Naotaka

2016-09-02

9,10-Phenanthrenequinone (PQ) was successfully used as a new mass-tagging reagent for sensitive labeling of aliphatic aldehydes (C3-C10) prior liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). This reagent could overcome the drawbacks of previous amine or hydrazine-based reagents, such as lower sensitivity, formation of two stereoisomeric reaction products for each single analyte, need for longer derivatization time, and poor reactivity with aliphatic aldehydes. The PQ-aldehyde derivatives exhibited intense [M+H](+) and a common product ion with ESI in the positive-ion mode. The derivatives were monitored at the transition of [M+H](+)→m/z 231.9 with detection limits from 4.0 to 100 pM (signal to noise ratio=3). 3-Phenylpropanal was used as an internal standard (IS) and the separation of the eight aldehydes and IS was achieved in less than 10min employing gradient elution with methanol and ammonium formate buffer (20mM, pH 4.0). The method employed salting out liquid-liquid extraction for aliphatic aldehydes form serum for the first time with excellent recoveries (92.6-110.8%). The developed method was validated and applied for quantification of the target aldehydes in serum of healthy volunteers (n=14). Copyright © 2016 Elsevier B.V. All rights reserved.

Removal of copper and iron by polyurethane foam column in FIA system for the determination of nickel in pierced ring.

PubMed

Vongboot, Monnapat; Suesoonthon, Monrudee

2015-01-01

Polyurethane foam (PUF) mini-column was used to eliminate copper and iron for the determination of nickel in pierced rings. The PUF mini-column was connected to FIA system for on-line sorption of copper and iron in complexes form of CuSCN(+) and FeSCN(2+). For this season, the acid solution containing a mixture of Ni(II), Fe(III), Cu(II) and SCN(-) ions was firstly flew into the PUF column. Then, the percolated solution which Fe(III) and Cu(II) ions is separated from analysis was injected into FIA system to react with 4-(2-pyridylazo) resorcinol (PAR) reagent in basic condition which this method is called pH gradient technique. The Ni-PAR complexes obtained were measured theirs absorbance at 500 nm by UV visible spectrophotometer. In this study, it was found that Cu(II) and Fe(III) were completely to form complexes with 400 mmol/L KSCN and entirely to eliminate in acidic condition at pH 3.0. In the optimum condition of these experiments, the method provided the linear relationship between absorbance and the concentration of Ni(II) in the range from 5.00 to 30.00 mg/L. Linear equation is y=0.0134x+0.0033 (R(2)=0.9948). Precision, assessed in the term of the relative standard deviation, RSD, and accuracy for multiple determinations obtained in values of 0.77-1.73% and 97.4%, respectively. The level of an average amount of Ni(II) in six piercing rings was evaluated to be 14.78 mg/g. Copyright © 2014 Elsevier B.V. All rights reserved.

Nano magnetic solid phase extraction for preconcentration of lead ions in environmental samples by a newly synthesized reagent.

PubMed

Golshekan, Mostafa; Shariati, Shahab

2013-01-01

In this study, magnetite nanoparticles with particle size lower than 47 nm were synthesized and were applied for preconcentration of Pb2+ ions from aqueous solutions. To preconcentrate the Pb2+ ions, the surface of the synthesized nano particles was modified with sodium dodecyl sulfate (SDS) as an anionic surfactant. A new chelating agent (2-((E)-2-amino-4,5-dinitrophenylimino)methyl)phenol) was synthesized and used to form a very stable complex with Pb2+ ions. The lead ions formed complexes and were quantitatively extracted with SDS-coated magnetite nanoparticles. After magnetic separation of adsorbent, the adsorbent was eluted with 0.5% (v/v) HC1 in dimethyl sulfoxide (DMSO) prior to analysis by flame atomic absorption spectrometry (FAAS). Orthogonal array design (OAD) was used to study and optimize the different experimental parameters. Under the optimum conditions, enhancement factor up to 63.5 was achieved for extraction from only 10 mL of sample solution and the relative standard deviation (RSD %) of the method was lower than 2.8%. The obtained calibration curve was linear in the range of 1-300 pg L-' with reasonable linearity (r2 > 0.998). The limit of detection (LOD) based on S/N = 3 was 0.04 microg L(-1) for 10 mL sample volumes. Finally, applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of lead ions in environmental samples and satisfactory results were obtained.

Optimization of the isolation and quantitation of kahweol and cafestol in green coffee oil.

PubMed

Chartier, Agnes; Beaumesnil, Mathieu; de Oliveira, Alessandra Lopes; Elfakir, Claire; Bostyn, Stephane

2013-12-15

Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffee oil. To recover them under their free form they have to be either saponified or trans-esterified. These two compounds are well known to be sensitive to heat, and reagents, therefore experimental conditions used in the transesterification reaction are critical. In this paper, a Doehlert experimental design plan is used to optimize the transesterification conditions using some key variables such as the temperature of the reaction, the reagent base concentration and the duration of the reaction. Therefore, the optimal parameters determined from the Doehlert design are equal to 70 °C, temperature of the reaction; 1.25 mol L(-1) concentration of the reagent base; and 60 min reaction time. The contour plots show that the extracted quantity of kahweol and cafestol can depend greatly from the experimental conditions. After transesterification, the free form of the diterpernes is extracted from the lipid fraction using liquid-liquid extraction and analyzed using GC-FID without prior derivatization. The amount of kahweol and cafestol obtained from green coffee oil obtained by cold mechanical press of Catuai coffee bean is equal to 33.2±2.2 and 24.3±2.4 g kg(-1)oil, respectively. In an attempt to streamline the process, the transesterification reaction is performed in an in-flow chemistry reactor using the optimal conditions obtained with the Doehlert experimental design. The amount of kahweol and cafestol obtained from the same green coffee oil is equal to 43.5 and 30.072 g kg(-1)oil, respectively. Results are slightly higher compared to the ones obtained with the batch procedure. This can be explained by a better mixing of the coffee oil with the reagents and a faster transesterification reaction. © 2013 Elsevier B.V. All rights reserved.

Identification of the components of a glycolytic enzyme metabolon on the human red blood cell membrane.

PubMed

Puchulu-Campanella, Estela; Chu, Haiyan; Anstee, David J; Galan, Jacob A; Tao, W Andy; Low, Philip S

2013-01-11

Glycolytic enzymes (GEs) have been shown to exist in multienzyme complexes on the inner surface of the human erythrocyte membrane. Because no protein other than band 3 has been found to interact with GEs, and because several GEs do not bind band 3, we decided to identify the additional membrane proteins that serve as docking sites for GE on the membrane. For this purpose, a method known as "label transfer" that employs a photoactivatable trifunctional cross-linking reagent to deliver a biotin from a derivatized GE to its binding partner on the membrane was used. Mass spectrometry analysis of membrane proteins that were biotinylated following rebinding and photoactivation of labeled GAPDH, aldolase, lactate dehydrogenase, and pyruvate kinase revealed not only the anticipated binding partner, band 3, but also the association of GEs with specific peptides in α- and β-spectrin, ankyrin, actin, p55, and protein 4.2. More importantly, the labeled GEs were also found to transfer biotin to other GEs in the complex, demonstrating for the first time that GEs also associate with each other in their membrane complexes. Surprisingly, a new GE binding site was repeatedly identified near the junction of the membrane-spanning and cytoplasmic domains of band 3, and this binding site was confirmed by direct binding studies. These results not only identify new components of the membrane-associated GE complexes but also provide molecular details on the specific peptides that form the interfacial contacts within each interaction.

Application of dual-cloud point extraction for the trace levels of copper in serum of different viral hepatitis patients by flame atomic absorption spectrometry: a multivariate study.

PubMed

Arain, Salma Aslam; Kazi, Tasneem G; Afridi, Hassan Imran; Abbasi, Abdul Rasool; Panhwar, Abdul Haleem; Naeemullah; Shanker, Bhawani; Arain, Mohammad Balal

2014-12-10

An efficient, innovative preconcentration method, dual-cloud point extraction (d-CPE) has been developed for the extraction and preconcentration of copper (Cu(2+)) in serum samples of different viral hepatitis patients prior to couple with flame atomic absorption spectrometry (FAAS). The d-CPE procedure was based on forming complexes of elemental ions with complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN), and subsequent entrapping the complexes in nonionic surfactant (Triton X-114). Then the surfactant rich phase containing the metal complexes was treated with aqueous nitric acid solution, and metal ions were back extracted into the aqueous phase, as second cloud point extraction stage, and finally determined by flame atomic absorption spectrometry using conventional nebulization. The multivariate strategy was applied to estimate the optimum values of experimental variables for the recovery of Cu(2+) using d-CPE. In optimum experimental conditions, the limit of detection and the enrichment factor were 0.046μgL(-1) and 78, respectively. The validity and accuracy of proposed method were checked by analysis of Cu(2+) in certified sample of serum (CRM) by d-CPE and conventional CPE procedure on same CRM. The proposed method was successfully applied to the determination of Cu(2+) in serum samples of different viral hepatitis patients and healthy controls. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification of the Components of a Glycolytic Enzyme Metabolon on the Human Red Blood Cell Membrane*

PubMed Central

Puchulu-Campanella, Estela; Chu, Haiyan; Anstee, David J.; Galan, Jacob A.; Tao, W. Andy; Low, Philip S.

2013-01-01

Glycolytic enzymes (GEs) have been shown to exist in multienzyme complexes on the inner surface of the human erythrocyte membrane. Because no protein other than band 3 has been found to interact with GEs, and because several GEs do not bind band 3, we decided to identify the additional membrane proteins that serve as docking sites for GE on the membrane. For this purpose, a method known as “label transfer” that employs a photoactivatable trifunctional cross-linking reagent to deliver a biotin from a derivatized GE to its binding partner on the membrane was used. Mass spectrometry analysis of membrane proteins that were biotinylated following rebinding and photoactivation of labeled GAPDH, aldolase, lactate dehydrogenase, and pyruvate kinase revealed not only the anticipated binding partner, band 3, but also the association of GEs with specific peptides in α- and β-spectrin, ankyrin, actin, p55, and protein 4.2. More importantly, the labeled GEs were also found to transfer biotin to other GEs in the complex, demonstrating for the first time that GEs also associate with each other in their membrane complexes. Surprisingly, a new GE binding site was repeatedly identified near the junction of the membrane-spanning and cytoplasmic domains of band 3, and this binding site was confirmed by direct binding studies. These results not only identify new components of the membrane-associated GE complexes but also provide molecular details on the specific peptides that form the interfacial contacts within each interaction. PMID:23150667

Flow chemistry: intelligent processing of gas-liquid transformations using a tube-in-tube reactor.

PubMed

Brzozowski, Martin; O'Brien, Matthew; Ley, Steven V; Polyzos, Anastasios

2015-02-17

CONSPECTUS: The previous decade has witnessed the expeditious uptake of flow chemistry techniques in modern synthesis laboratories, and flow-based chemistry is poised to significantly impact our approach to chemical preparation. The advantages of moving from classical batch synthesis to flow mode, in order to address the limitations of traditional approaches, particularly within the context of organic synthesis are now well established. Flow chemistry methodology has led to measurable improvements in safety and reduced energy consumption and has enabled the expansion of available reaction conditions. Contributions from our own laboratories have focused on the establishment of flow chemistry methods to address challenges associated with the assembly of complex targets through the development of multistep methods employing supported reagents and in-line monitoring of reaction intermediates to ensure the delivery of high quality target compounds. Recently, flow chemistry approaches have addressed the challenges associated with reactions utilizing reactive gases in classical batch synthesis. The small volumes of microreactors ameliorate the hazards of high-pressure gas reactions and enable improved mixing with the liquid phase. Established strategies for gas-liquid reactions in flow have relied on plug-flow (or segmented flow) regimes in which the gas plugs are introduced to a liquid stream and dissolution of gas relies on interfacial contact of the gas bubble with the liquid phase. This approach confers limited control over gas concentration within the liquid phase and is unsuitable for multistep methods requiring heterogeneous catalysis or solid supported reagents. We have identified the use of a gas-permeable fluoropolymer, Teflon AF-2400, as a simple method of achieving efficient gas-liquid contact to afford homogeneous solutions of reactive gases in flow. The membrane permits the transport of a wide range of gases with significant control of the stoichiometry of reactive gas in a given reaction mixture. We have developed a tube-in-tube reactor device consisting of a pair of concentric capillaries in which pressurized gas permeates through an inner Teflon AF-2400 tube and reacts with dissolved substrate within a liquid phase that flows within a second gas impermeable tube. This Account examines our efforts toward the development of a simple, unified methodology for the processing of gaseous reagents in flow by way of development of a tube-in-tube reactor device and applications to key C-C, C-N, and C-O bond forming and hydrogenation reactions. We further describe the application to multistep reactions using solid-supported reagents and extend the technology to processes utilizing multiple gas reagents. A key feature of our work is the development of computer-aided imaging techniques to allow automated in-line monitoring of gas concentration and stoichiometry in real time. We anticipate that this Account will illustrate the convenience and benefits of membrane tube-in-tube reactor technology to improve and concomitantly broaden the scope of gas/liquid/solid reactions in organic synthesis.

Integration of active and passive microwave signatures for characterization of soil properties

NASA Astrophysics Data System (ADS)

Laulhe, Sebastien

The reaction between an aminooxy moiety (RONH2) and a carbonyl group of either an aldehyde or a ketone --- known as an oximation reaction --- is a versatile click chemistry coupling that generates a robust oxime ether linkage. The oximation reaction is chemoselective and can be performed under mild conditions in a large variety of solvents, including water. The attractive properties of the aminooxy group and derived oximation reactions, reviewed in Chapter 1, inspired us to use this chemistry as a key feature of our research. Specifically, we prepare functionalized aminooxy compounds so that the oximation chemistry can then serve as a prelude to new synthetic or analytical methods. For example, Chapter 2 presents an improved preparation of O-(diphenylphosphinyl)hydroxylamine (DPPH), an aminooxy-containing reagent, using the classic Schotten-Baumann conditions. We show how DPPH can then be used as a chemoselective nitrogen transfer reagent for a one-pot aldehyde-to-nitrile functional group transformation. Sixteen aldehydes were smoothly transformed to their corresponding nitriles by heating at 85 °C with DPPH in toluene. The reaction can be accomplished in the presence of alcohol, ketone, ester, or amine functionality. In another application, we use functionalized aminooxy reagents to achieve quantitative multiplexed gas chromatography-mass spectrometry (GC-MS) analysis. Specifically, we chemoselectively derivatize carbonyl (aldehyde and ketone) metabolites using the aminooxy-containing reagents. Chapter 3 presents a focused fundamental study of the propensity of oxime ethers to undergo MS-induced fragmentations, such as the McLafferty rearrangement. In particular, we studied structural factors that promoted alpha,beta-fragmentation in oximes of both ketones and aldehydes, as well as the derived silyl ethers of these adducts. We determined that 1) the propensity of the McLafferty rearrangement was greatly enhanced by oxygen at the b-position of silyl oxime ethers, 2) the McLafferty rearrangement is more prominent for E-isomers of oxime and silyl oxime ethers than for the corresponding Z-isomers, and 3) Z-isomers of silyl oxime ethers with CH2 at the b-position generate nitrilium ions to a greater extent than their corresponding E-isomers. Chapter 4 describes the 3-step synthesis of a new class of stable isotope-labeled derivatizing reagents ---- a&barbelow;minooxye&barbelow;thyl p&barbelow;ropionate reagents (AEP) ---- that enable multiplexed GC-MS analysis of small molecule carbonyl compounds. The AEP reagents contain 1) an aminooxy moiety, and 2) a propionate ester moiety that generates a reporter isotope-labeled mass spectral tag (MST) in the form of an ethyl carbenium ion via an ester a-cleavage. The AEP MSTs appear in an m/z zone of minimal interference (ZMI) in the range m/z 32-34. This is a key feature in that unobstructed observation of reporter MSTs in this zone significantly improves simultaneous quantitation of carbonyl analytes from multiple samples without recourse to MS peak deconvolution strategies. Also, and in contrast to known isotope coding reagents for GC-MS, AEP reagents are not affected by the chromatographic isotope effect. The versatility of the technology for carbonyl metabolite profiling and absolute quantification is demonstrated by an analysis of turmeric extract, serving as a representative complex biological sample. A series of analogous methyl ketones were profiled from characteristic MS fragmentations of the AEP-derived oxime ether adducts, and two members, 2-nonanone and 2-undecanone, were quantified using AEP-labeled external standards. Finally, Chapter 5 concludes with additional demonstrations of click chemistry. We used oximation to ligate linker molecules to fluorophores and gold nanoparticles (AuNPs) to generate a fluorescent nano-entity for breast cancer location and diagnosis. Five homologous linkers, each consisting of a thiol-terminated hydrophobic domain coupled to an aminooxy-terminated PEG-based domain, were prerared using a 6-step synthesis in 7-25% overall yield. The aminooxy end subsequently was reacted with an aldehyde-functionalized cypate fluorophore, and the thiol end was used for attachment to gold nanoparticles. Linker attachment to cypate in this manner was superior to previously investigated amide coupling involving linker amines and cypate carboxylic acid. Collectively, the results from these investigations demonstrates a novel strategy that employs functionalized aminooxy substrates and reagents to first exploit the high yielding and selective click coupling with carbonyl substrates to set the stage for secondary synthetic or analytical operations. Approaches developed in this multifaceted study appear to be applicable to a variety of synthetic problems ranging from those of a purely chemical nature to other impacting biological systems.

Development of a polydimethylsiloxane-thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water samples.

PubMed

Prieto-Blanco, M C; Jornet-Martínez, N; Moliner-Martínez, Y; Molins-Legua, C; Herráez-Hernández, R; Verdú Andrés, J; Campins-Falcó, P

2015-01-15

This report describes a polydimethylsiloxane (PDMS)-thymol/nitroprusside delivery composite sensor for direct monitoring of ammonium in environmental water samples. The sensor is based on a PDMS support that contains the Berthelot's reaction reagents. To prepare the PDMS-thymol/nitroprusside composite discs, thymol and nitroprusside have been encapsulated in the PDMS matrix, forming a reagent release support which significantly simplifies the analytical measurements, since it avoids the need to prepare derivatizing reagents and sample handling is reduced to the sampling step. When, the PDMS-thymol/nitroprusside composite was introduced in water samples spontaneous release of the chromophore and catalyst was produced, and the derivatization reaction took place to form the indothymol blue. Thus, qualitative analysis of NH4(+) could be carried out by visual inspection, but also, it can be quantified by measuring the absorbance at 690 nm. These portable devices provided good sensitivity (LOD<0.4 mg L(-1)) and reproducibility (RSD <10%) for the rapid detection of ammonium. The PDMS-NH4(+) sensor has been successfully applied to determine ammonium in water samples and in the aqueous extracts of particulate matter PM10 samples. Moreover, the reliability of the method for qualitative analysis has been demonstrated. Finally, the advantages of the PDMS-NH4(+) sensor have been examined by comparing some analytical and complementary characteristics with the properties of well-established ammonium determination methods. Copyright © 2014 Elsevier B.V. All rights reserved.

Production of the virus-like particles of nipah virus matrix protein in Pichia pastoris as diagnostic reagents.

PubMed

Joseph, Narcisse Ms; Ho, Kok Lian; Tey, Beng Ti; Tan, Chon Seng; Shafee, Norazizah; Tan, Wen Siang

2016-07-08

The matrix (M) protein of Nipah virus (NiV) is a peripheral protein that plays a vital role in the envelopment of nucleocapsid protein and acts as a bridge between the viral surface and the nucleocapsid proteins. The M protein is also proven to play an important role in production of virus-like particles (VLPs) and is essential for assembly and budding of NiV particles. The recombinant M protein produced in Escherichia coli assembled into VLPs in the absence of the viral surface proteins. However, the E. coli produced VLPs are smaller than the native virus particles. Therefore, the aims of this study were to produce NiV M protein in Pichia pastoris, to examine the structure of the VLPs formed, and to assess the potential of the VLPs as a diagnostic reagent. The M protein was successfully expressed in P. pastoris and was detected with anti-myc antibody using Western blotting. The VLPs formed by the recombinant M protein were purified with sucrose density gradient ultracentrifugation, high-performance liquid chromatography (HPLC), and Immobilized Metal Affinity Chromatography (IMAC). Immunogold staining and transmission electron microscopy confirmed that the M protein assembled into VLPs as large as 200 nm. ELISA revealed that the NiV M protein produced in P. pastoris reacted strongly with positive NiV sera demonstrating its potential as a diagnostic reagent. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1038-1045, 2016. © 2016 American Institute of Chemical Engineers.

Kinetics and selectivity of permanganate chemiluminescence: a study of hydroxyl and amino disubstituted benzene positional isomers.

PubMed

Slezak, Teo; Smith, Zoe M; Adcock, Jacqui L; Hindson, Christopher M; Barnett, Neil W; Nesterenko, Pavel N; Francis, Paul S

2011-11-30

Examination of the chemiluminescence reactions of dihydroxybenzenes, aminophenols and phenylenediamines with acidic potassium permanganate has provided a new understanding of the relationships between analyte structure, reaction conditions, kinetics of the light-producing pathway and emission intensity, with broad implications for this widely utilised chemiluminescence detection system. Using a permanganate reagent prepared in a polyphosphate solution and adjusted to pH 2.5, large differences in the rate of reaction with different positional isomers were observed, with the meta-substituted forms reacting far slower and therefore exhibiting much lower chemiluminescence intensities in flow analysis systems. The preliminary partial reduction of permanganate to form significant concentrations of Mn(III) increased the rate of reaction with all analytes tested, resulting in comparable or (in the case of aminophenol and phenylenediamine) even greater emission intensities for the meta-isomers, demonstrating the opportunity to tune the selectivity of the reagent towards certain classes of compound or even specific positional isomers of the same compound. Using more acidic permanganate reagents, in which polyphosphates are not required, the discrepancy between the chemiluminescence intensities was still observed, but was less prominent due to the generally faster rates of reaction. The enhancement of these chemiluminescence reactions by on-line addition of formic acid or formaldehyde can in part also be attributed to the generation of significant pools of the key Mn(III) precursor to the emitting species. Copyright © 2011 Elsevier B.V. All rights reserved.

Biological effects and epidemiological consequences of arsenic exposure, and reagents that can ameliorate arsenic damage in vivo

PubMed Central

Rao, Chinthalapally V.; Pal, Sanya; Mohammed, Altaf; Farooqui, Mudassir; Doescher, Mark P.; Asch, Adam S.; Yamada, Hiroshi Y.

2017-01-01

Through contaminated diet, water, and other forms of environmental exposure, arsenic affects human health. There are many U.S. and worldwide “hot spots” where the arsenic level in public water exceeds the maximum exposure limit. The biological effects of chronic arsenic exposure include generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage, epigenetic DNA modification, induction of genomic instability, and inflammation and immunomodulation, all of which can initiate carcinogenesis. High arsenic exposure is epidemiologically associated with skin, lung, bladder, liver, kidney and pancreatic cancer, and cardiovascular, neuronal, and other diseases. This review briefly summarizes the biological effects of arsenic exposure and epidemiological cancer studies worldwide, and provides an overview for emerging rodent-based studies of reagents that can ameliorate the effects of arsenic exposure in vivo. These reagents may be translated to human populations for disease prevention. We propose the importance of developing a biomarker-based precision prevention approach for the health issues associated with arsenic exposure that affects millions of people worldwide. PMID:28915699

Recyclable fluorescent gold nanocluster membrane for visual sensing of copper(II) ion in aqueous solution.

PubMed

Lin, Zhijin; Luo, Fenqiang; Dong, Tongqing; Zheng, Liyan; Wang, Yaxian; Chi, Yuwu; Chen, Guonan

2012-05-21

Recently, metal-selective fluorescent chemosensors have attracted intense attention for their simple and real-time tracking of metal ions in environmental samples. However, most of the existing fluorescent sensors are one-off sensors and thus suffer from large amount of reagent consumption, significant experimental cost and raising the risk of environmental pollution. In this paper, we developed a green (low reagent consumption, low-toxicity reagent use), recyclable, and visual sensor for Cu(2+) in aqueous solution by using a fluorescent gold nanoclusters membrane (FGM) as the sensing unit, basing on our findings on gold nanoclusters (Au NCs) that the bovine serum albumin (BSA)-coated Au NCs exhibit excellent membrane-forming ability under the isoelectric point of BSA, and thus enable us to obtain a new type of sensing membrane (i.e. FGM) by denaturing Au NCs; the fluorescence of FGM can be significantly quenched by Cu(2+) ion, and the quenched fluorescence can be totally recovered by histidine; the as-prepared FGM is very stable and recyclable, which makes it an ideal sensing material.

Influence of the order of reagent addition on NDMA formation during chloramination.

PubMed

Schreiber, I Marie; Mitch, William A

2005-05-15

The formation of the potent carcinogen, N-nitrosodimethylamine (NDMA), during chlorine disinfection has caused significant concern among drinking water and wastewater recycling utilities practicing intentional or unintentional chloramination. Previous research modeled NDMA formation as arising from a reaction between monochloramine and organic nitrogen precursors, such as dimethylamine, via an unsymmetrical dimethylhydrazine (UDMH) intermediate. Contrary to the importance of monochloramine indicated by previous studies, hypochlorite formed an order of magnitude more NDMA than monochloramine when applied to a secondary municipal wastewater effluent containing excess ammonia. Experiments involving variation of the order that each reagent (i.e., hypochlorite, ammonium chloride, and dimethylamine) was added to solution suggest two factors that may be more important for NDMA formation than the presence of monochloramine: (i) the chlorination state of organic nitrogen precursors and (ii) the partial formation of dichloramine. Although dichloramine formation was most influenced by the pH conditions under which inorganic chloramine formation was performed, mixing effects related to the order of reagent addition may be important at full-scale plants. Chloramination strategies are suggested that may reduce NDMA formation by nearly an order of magnitude.

Visualising substrate-fingermark interactions: Solid-state NMR spectroscopy of amino acid reagent development on cellulose substrates.

PubMed

Spindler, Xanthe; Shimmon, Ronald; Roux, Claude; Lennard, Chris

2015-05-01

Most spectroscopic studies of the reaction products formed by ninhydrin, 1,2-indanedione-zinc (Ind-Zn) and 1,8-diazafluoren-9-one (DFO) when reacted with amino acids or latent fingermarks on paper substrates are focused on visible absorption or luminescence spectroscopy. In addition, structural elucidation studies are typically limited to solution-based mass spectrometry or liquid nuclear magnetic resonance (NMR) spectroscopy, which does not provide an accurate representation of the fingermark development process on common paper substrates. The research presented in this article demonstrates that solid-state carbon-13 magic angle spinning NMR ((13)C-MAS-NMR) is a technique that can not only be utilised for structural studies of fingermark enhancement reagents, but is a promising technique for characterising the effect of paper chemistry on fingermark deposition and enhancement. The latter opens up a research area that has been under-explored to date but has the potential to improve our understanding of how fingermark secretions and enhancement reagents interact with paper substrates. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Isolation and characterization of the DNA-binding protein (DBP) of the Autographa californica multiple nucleopolyhedrovirus

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

Mikhailov, Victor S.; N. K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow 117808; Vanarsdall, Adam L.

2008-01-20

DNA-binding protein (DBP) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) was expressed as an N-terminal His{sub 6}-tag fusion using a recombinant baculovirus and purified to near homogeneity. Purified DBP formed oligomers that were crosslinked by redox reagents resulting in predominantly protein dimers and tetramers. In gel retardation assays, DBP showed a high affinity for single-stranded oligonucleotides and was able to compete with another baculovirus SSB protein, LEF-3, for binding sites. DBP binding protected ssDNA against hydrolysis by a baculovirus alkaline nuclease AN/LEF-3 complex. Partial proteolysis by trypsin revealed a domain structure of DBP that is required for interaction with DNA andmore » that can be disrupted by thermal treatment. Binding to ssDNA, but not to dsDNA, changed the pattern of proteolytic fragments of DBP indicating adjustments in protein structure upon interaction with ssDNA. DBP was capable of unwinding short DNA duplexes and also promoted the renaturation of long complementary strands of ssDNA into duplexes. The unwinding and renaturation activities of DBP, as well as the DNA binding activity, were sensitive to sulfhydryl reagents and were inhibited by oxidation of thiol groups with diamide or by alkylation with N-ethylmaleimide. A high affinity of DBP for ssDNA and its unwinding and renaturation activities confirmed identification of DBP as a member of the SSB/recombinase family. These activities and a tight association with subnuclear structures suggests that DBP is a component of the virogenic stroma that is involved in the processing of replicative intermediates.« less

Speciation and Determination of Low Concentration of Iron in Beer Samples by Cloud Point Extraction

ERIC Educational Resources Information Center

Khalafi, Lida; Doolittle, Pamela; Wright, John

2018-01-01

A laboratory experiment is described in which students determine the concentration and speciation of iron in beer samples using cloud point extraction and absorbance spectroscopy. The basis of determination is the complexation between iron and 2-(5-bromo-2- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as a colorimetric reagent in an aqueous…

Development and Evaluation of an Analytical Method for the Determination of Total Atmospheric Mercury. Final Report.

ERIC Educational Resources Information Center

Chase, D. L.; And Others

Total mercury in ambient air can be collected in iodine monochloride, but the subsequent analysis is relatively complex and tedious, and contamination from reagents and containers is a problem. A sliver wool collector, preceded by a catalytic pyrolysis furnace, gives good recovery of mercury and simplifies the analytical step. An instrumental…

Hypervalent iodine-promoted α-fluorination of acetophenone derivatives with a triethylamine·HF complex.

PubMed

Kitamura, Tsugio; Muta, Kensuke; Muta, Kazutaka

2014-06-20

The direct fluorination reaction of acetophenone using iodosylarenes and TEA·5HF was conducted under mild conditions except for use of a HF reagent. The fluorination reaction was applied to acetophenone derivatives, acetonaphthones, benzyl phenyl ketone, propiophenone, butyrophenone, 1-indanone, and phenacyl chloride, giving selectively the corresponding α-fluoroketone derivatives in good yields.

The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii.

PubMed

Chen, Hua-Wei; Ching, Wei-Mei

2016-04-18

Coxiella burnetii, the agent causing Q fever, is an obligate intracellular bacterium. PCR based diagnostic assays have been developed for detecting C. burnetii DNA in cell cultures and clinical samples. PCR requires specialized equipment and extensive end user training, and therefore, it is not suitable for routine work especially in a resource-constrained area. We have developed a loop-mediated isothermal amplification (LAMP) assay to detect the presence of C. burnetii in patient samples. This method is performed at a single temperature around 60 °C in a water bath or heating block. The sensitivity of this LAMP assay is very similar to PCR with a detection limit of about 25 copies per reaction. This report describes the preparation of the reaction using lyophilized reagents and visualization of results using hydroxynaphthol blue (HNB) or a UV lamp with fluorescent intercalating dye in the reaction. The LAMP reagents were lyophilized and stored at room temperature (RT) for one month without loss of detection sensitivity. This LAMP assay is particularly robust because the reaction mixture preparation does not involve complex steps. This method is ideal for use in resource-limited settings where Q fever is endemic.

Application of Colorimetric Solid Phase Extraction (C-SPE) to Monitoring Nickel(II) and Lead(II) in Spacecraft Water Supplies

NASA Technical Reports Server (NTRS)

Diaz, Neil C.; Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.; Rutz, Jeff; Mudgett, Paul; Schultz, John

2004-01-01

Archived water samples collected on the International Space Station (ISS) and returned to Earth for analysis have, in a few instances, contained trace levels of heavy metals. Building on our previous advances using Colorimetric Solid Phase Extraction (C-SPE) as a biocide monitoring technique, we are devising methods for the low level monitoring of nickel(II), lead(II) and other heavy metals. C-SPE is a sorption-spectrophotometric platform based on the extraction of analytes onto a membrane impregnated with a colorimetric reagent that are then quantified on the surface of the membrane using a diffuse reflectance spectrophotometer. Along these lines, we have determined nickel(II) via complexation with dimethylglyoxime (DMG) and begun to examine the analysis of lead(II) by its reaction with 2,5- dimercapto-1,3,4-thiadiazole (DMTD) and 4-(2- pyridylazo)-resorcinol (PAR). These developments are also extending a new variant of C-SPE in which immobilized reagents are being incorporated into this methodology in order to optimize sample reaction conditions and to introduce the colorimetric reagent. This paper describes the status of our development of these two new methods.

Reagent-free bacterial identification using multivariate analysis of transmission spectra

NASA Astrophysics Data System (ADS)

Smith, Jennifer M.; Huffman, Debra E.; Acosta, Dayanis; Serebrennikova, Yulia; García-Rubio, Luis; Leparc, German F.

2012-10-01

The identification of bacterial pathogens from culture is critical to the proper administration of antibiotics and patient treatment. Many of the tests currently used in the clinical microbiology laboratory for bacterial identification today can be highly sensitive and specific; however, they have the additional burdens of complexity, cost, and the need for specialized reagents. We present an innovative, reagent-free method for the identification of pathogens from culture. A clinical study has been initiated to evaluate the sensitivity and specificity of this approach. Multiwavelength transmission spectra were generated from a set of clinical isolates including Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Spectra of an initial training set of these target organisms were used to create identification models representing the spectral variability of each species using multivariate statistical techniques. Next, the spectra of the blinded isolates of targeted species were identified using the model achieving >94% sensitivity and >98% specificity, with 100% accuracy for P. aeruginosa and S. aureus. The results from this on-going clinical study indicate this approach is a powerful and exciting technique for identification of pathogens. The menu of models is being expanded to include other bacterial genera and species of clinical significance.

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

Bang, Hyunjin; Kim, Youngmee; Kim, Seri

We found new synthetic routes to obtain 1-D quaternary thiophosphate compounds and a 0-D molecular complex containing a Nb{sub 2}S{sub 4} core from a 2-D ternary thiophosphate, Nb{sub 4}P{sub 2}S{sub 21}. When Nb{sub 4}P{sub 2}S{sub 21} was reacted with alkali metal halides (ACl; A=Na, K, Rb, Cs) or TlCl at 500-700 deg. C, the -S-S-S- bridges in 2-D Nb{sub 2}PS{sub 10}-S-S{sub 10}PNb{sub 2} were excised to form a 1-D chain, and cations were inserted between the chains to form ANb{sub 2}PS{sub 10} (A=Na, K, Rb, Cs, Tl). We also found that thallium chloride (TlCl) is an excellent reagent for furthermore » excision, and it substitutes chloride ligands for the sulfur ligands of 2-D Nb{sub 4}P{sub 2}S{sub 21} to form the molecular complex Tl{sub 5}[Nb{sub 2}S{sub 4}Cl{sub 8}]Cl. Crystal data for TlNb{sub 2}PS{sub 10}: monoclinic, Pn, a=6.9452(11) A, b=7.3761(12) A, 12.873(2) A, {beta}=104.472(3){sup o}, and Z=2. Crystal data for Tl{sub 5}[Nb{sub 2}S{sub 4}Cl{sub 8}]Cl: orthorhombic, Immm, a=7.001(5) A, b=9.509(7) A, c=15.546(11) A, and Z=2. - Graphical abstract: We developed new synthetic routes to obtain 1-D quaternary thiophosphate compounds and a molecular complex containing a Nb{sub 2}S{sub 4} core from a 2-D ternary thiophosphate, Nb{sub 4}P{sub 2}S{sub 21}. When Nb{sub 4}P{sub 2}S{sub 21} was reacted with alkali metal halides or TlCl, the -S-S-S- bridges in 2-D Nb{sub 2}PS{sub 10}-S-S{sub 10}PNb{sub 2} were excised to form a 1-D chain, and cations were inserted between the chains.« less

77 FR 63787 - Pure Magnesium in Granular Form from the People's Republic of China: Continuation of Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-17

... (202) 482-0414, respectively. SUPPLEMENTARY INFORMATION: On February 1, 2012, the Department initiated... aware used to make such excluded reagents are: Lime, calcium metal, calcium silicon, calcium carbide, calcium carbonate, carbon, slag coagulants, fluorspar, nephaline syenite, feldspar, aluminum, alumina...

77 FR 46030 - Pure Magnesium in Granular Form From the People's Republic of China: Preliminary Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-02

... Street and Constitution Avenue NW., Washington, DC 20230; telephone: (202) 482-6231. SUPPLEMENTARY... Department is aware used to make such excluded reagents are: Lime, calcium metal, calcium silicon, calcium carbide, calcium carbonate, carbon, slag coagulants, fluorspar, nephaline syenite, feldspar, aluminum...

Long Range Materials Research

DTIC Science & Technology

1975-06-01

for forming Si-C bonds; the two most general are Grignard reactions (eq. 3) and hydrosilylations of olefins (eq. 4); -76- wm RMgX + R3SiY Y...October, 1973. (4) D. N. Marquardt, Ph.D. Thesis, Stanford University, May, 1974. (5) L. F. Fieser and M. Fieser, Reagents for Organic Synthesis, John

21 CFR 866.5560 - Lactic dehydrogenase immunological test system.

Code of Federal Regulations, 2011 CFR

2011-04-01

... immunological test system is a device that consists of the reagents used to measure by immunochemical techniques... found in a variety of conditions, including megaloblastic anemia (decrease in the number of mature red blood cells), myocardial infarction (heart disease), and some forms of leukemia (cancer of the blood...

21 CFR 866.5560 - Lactic dehydrogenase immunological test system.

Code of Federal Regulations, 2013 CFR

2013-04-01

... immunological test system is a device that consists of the reagents used to measure by immunochemical techniques... found in a variety of conditions, including megaloblastic anemia (decrease in the number of mature red blood cells), myocardial infarction (heart disease), and some forms of leukemia (cancer of the blood...

21 CFR 866.5560 - Lactic dehydrogenase immunological test system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... immunological test system is a device that consists of the reagents used to measure by immunochemical techniques... found in a variety of conditions, including megaloblastic anemia (decrease in the number of mature red blood cells), myocardial infarction (heart disease), and some forms of leukemia (cancer of the blood...

21 CFR 866.5560 - Lactic dehydrogenase immunological test system.

Code of Federal Regulations, 2012 CFR

2012-04-01

... immunological test system is a device that consists of the reagents used to measure by immunochemical techniques... found in a variety of conditions, including megaloblastic anemia (decrease in the number of mature red blood cells), myocardial infarction (heart disease), and some forms of leukemia (cancer of the blood...

Frataxin Accelerates [2Fe-2S] Cluster Formation on the Human Fe–S Assembly Complex

PubMed Central

Fox, Nicholas G.; Das, Deepika; Chakrabarti, Mrinmoy; Lindahl, Paul A.; Barondeau, David P.

2015-01-01

Iron–sulfur (Fe–S) clusters function as protein cofactors for a wide variety of critical cellular reactions. In human mitochondria, a core Fe–S assembly complex [called SDUF and composed of NFS1, ISD11, ISCU2, and frataxin (FXN) proteins] synthesizes Fe–S clusters from iron, cysteine sulfur, and reducing equivalents and then transfers these intact clusters to target proteins. In vitro assays have relied on reducing the complexity of this complicated Fe–S assembly process by using surrogate electron donor molecules and monitoring simplified reactions. Recent studies have concluded that FXN promotes the synthesis of [4Fe-4S] clusters on the mammalian Fe–S assembly complex. Here the kinetics of Fe–S synthesis reactions were determined using different electron donation systems and by monitoring the products with circular dichroism and absorbance spectroscopies. We discovered that common surrogate electron donor molecules intercepted Fe–S cluster intermediates and formed high-molecular weight species (HMWS). The HMWS are associated with iron, sulfide, and thiol-containing proteins and have properties of a heterogeneous solubilized mineral with spectroscopic properties remarkably reminiscent of those of [4Fe-4S] clusters. In contrast, reactions using physiological reagents revealed that FXN accelerates the formation of [2Fe-2S] clusters rather than [4Fe-4S] clusters as previously reported. In the preceding paper [Fox, N. G., et al. (2015) Biochemistry 54, DOI: 10.1021/bi5014485], [2Fe-2S] intermediates on the SDUF complex were shown to readily transfer to uncomplexed ISCU2 or apo acceptor proteins, depending on the reaction conditions. Our results indicate that FXN accelerates a rate-limiting sulfur transfer step in the synthesis of [2Fe-2S] clusters on the human Fe–S assembly complex. PMID:26016518

Frataxin Accelerates [2Fe-2S] Cluster Formation on the Human Fe-S Assembly Complex.

PubMed

Fox, Nicholas G; Das, Deepika; Chakrabarti, Mrinmoy; Lindahl, Paul A; Barondeau, David P

2015-06-30

Iron-sulfur (Fe-S) clusters function as protein cofactors for a wide variety of critical cellular reactions. In human mitochondria, a core Fe-S assembly complex [called SDUF and composed of NFS1, ISD11, ISCU2, and frataxin (FXN) proteins] synthesizes Fe-S clusters from iron, cysteine sulfur, and reducing equivalents and then transfers these intact clusters to target proteins. In vitro assays have relied on reducing the complexity of this complicated Fe-S assembly process by using surrogate electron donor molecules and monitoring simplified reactions. Recent studies have concluded that FXN promotes the synthesis of [4Fe-4S] clusters on the mammalian Fe-S assembly complex. Here the kinetics of Fe-S synthesis reactions were determined using different electron donation systems and by monitoring the products with circular dichroism and absorbance spectroscopies. We discovered that common surrogate electron donor molecules intercepted Fe-S cluster intermediates and formed high-molecular weight species (HMWS). The HMWS are associated with iron, sulfide, and thiol-containing proteins and have properties of a heterogeneous solubilized mineral with spectroscopic properties remarkably reminiscent of those of [4Fe-4S] clusters. In contrast, reactions using physiological reagents revealed that FXN accelerates the formation of [2Fe-2S] clusters rather than [4Fe-4S] clusters as previously reported. In the preceding paper [Fox, N. G., et al. (2015) Biochemistry 54, DOI: 10.1021/bi5014485], [2Fe-2S] intermediates on the SDUF complex were shown to readily transfer to uncomplexed ISCU2 or apo acceptor proteins, depending on the reaction conditions. Our results indicate that FXN accelerates a rate-limiting sulfur transfer step in the synthesis of [2Fe-2S] clusters on the human Fe-S assembly complex.

Heat shock protein-90 beta is expressed at the surface of multipotential mesenchymal precursor cells: generation of a novel monoclonal antibody, STRO-4, with specificity for mesenchymal precursor cells from human and ovine tissues.

PubMed

Gronthos, Stan; McCarty, Rosa; Mrozik, Krzysztof; Fitter, Stephen; Paton, Sharon; Menicanin, Danijela; Itescu, Silviu; Bartold, P Mark; Xian, Cory; Zannettino, Andrew C W

2009-11-01

Mesenchymal stromal cells (MSCs) and their precursor cells (MPCs) can proliferate and differentiate into multiple mesodermal and some ectodermal and endodermal tissues. Culture-expanded MSCs are currently being evaluated as a possible cell therapy to replace/repair injured or diseased tissues. While a number of mAb reagents with specificity to human MSCs, including STRO-1, STRO-3 (BLK ALP), CD71 (SH2, SH3), CD106 (VCAM-1), CD166, and CD271, have facilitated the isolation of purified populations of human MSCs from primary tissues, few if any mAb reagents have been described that can be used to isolate equivalent cells from other species. This is of particular relevance when assessing the tissue regenerative efficacy of MSCs in large immunocompetent, preclinical animal models of disease. In light of this, we sought to generate novel monoclonal antibodies (mAb) with specific reactivity against a cell surface molecule that is expressed at high levels by MSCs from different species. Using CD106 (VCAM-1)-selected ovine MSCs as an immunogen, mAb-producing hybridomas were selected for their reactivity to both human and ovine MSCs. One such hybridoma, termed STRO-4, produced an IgG mAb that reacted with <5% of human and ovine bone marrow (BM) mononuclear cells. As a single selection reagent, STRO-4 mAb was able to enrich colony-forming fibroblasts (CFU-F) in both human and ovine BM by 16- and 8-folds, respectively. Cells isolated with STRO-4 exhibited reactivity with markers commonly associated with MSCs isolated by plastic adherence including CD29, CD44, and CD166. Moreover, when placed in inductive culture conditions in vitro, STRO-4(+) MSCs exhibited multilineage differentiation potential and were capable of forming a mineralized matrix, lipid-filled adipocytes, and chondrocytes capable of forming a glycosaminoglycan-rich matrix. Biochemical analysis revealed that STRO-4 identified the beta isoform of heat shock protein-90 (Hsp90beta). In addition to identifying an antibody reagent that identifies a highly conserved epitope expressed by MSCs from different species, our study also points to a potential role for Hsp90beta in MSC biology.

Spot test kit for explosives detection

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

Pagoria, Philip F; Whipple, Richard E; Nunes, Peter J

An explosion tester system comprising a body, a lateral flow membrane swab unit adapted to be removeably connected to the body, a first explosives detecting reagent, a first reagent holder and dispenser operatively connected to the body, the first reagent holder and dispenser containing the first explosives detecting reagent and positioned to deliver the first explosives detecting reagent to the lateral flow membrane swab unit when the lateral flow membrane swab unit is connected to the body, a second explosives detecting reagent, and a second reagent holder and dispenser operatively connected to the body, the second reagent holder and dispensermore » containing the second explosives detecting reagent and positioned to deliver the second explosives detecting reagent to the lateral flow membrane swab unit when the lateral flow membrane swab unit is connected to the body.« less

Crystal Violet Lactone Salicylaldehyde Hydrazone Zn(II) Complex: a Reversible Photochromic Material both in Solution and in Solid Matrix

PubMed Central

Li, Kai; Li, Yuanyuan; Tao, Jing; Liu, Lu; Wang, Lili; Hou, Hongwei; Tong, Aijun

2015-01-01

Crystal violet lactone (CVL) is a classic halochromic dye which has been widely used as chromogenic reagent in thermochromic and piezochromic systems. In this work, a very first example of CVL-based reversible photochromic compound was developed, which showed distinct color change upon UV-visible light irradiation both in solution and in solid matrix. Moreover, metal complex of CVL salicylaldehyde hydrozone was facilely synthesized, exhibiting reversible photochromic properties with good fatigue resistance. It was served as promising solid material for photo-patterning. PMID:26412101

Di-μ-bromido-bis-[(diethyl ether-κO)(2,4,6-tri-methyl-phen-yl)magnesium]: the mesityl Grignard reagent.

PubMed

Seven, Omer; Bolte, Michael; Lerner, Hans-Wolfram

2013-01-01

The crystal structure of the title compound, [Mg2Br2(C9H11)2(C4H10O)2], features a centrosymmetric two-centre magnesium complex with half a mol-ecule in the asymmetric unit. The Mg atom is in a considerably distorted Br2CO coordination. Bond lengths and angles are comparable with already published values. The crystal packing is stabilized by C-H⋯π inter-actions linking the complexes into sheets parallel to (0-11).

Production of latex agglutination reagents for pneumococcal serotyping

PubMed Central

2013-01-01

Background The current ‘gold standard’ for serotyping pneumococci is the Quellung test. This technique is laborious and requires a certain level of training to correctly perform. Commercial pneumococcal latex agglutination serotyping reagents are available, but these are expensive. In-house production of latex agglutination reagents can be a cost-effective alternative to using commercially available reagents. This paper describes a method for the production and quality control (QC) of latex reagents, including problem solving recommendations, for pneumococcal serotyping. Results Here we describe a method for the production of latex agglutination reagents based on the passive adsorption of antibodies to latex particles. Sixty-five latex agglutination reagents were made using the PneuCarriage Project (PCP) method, of which 35 passed QC. The other 30 reagents failed QC due to auto-agglutination (n=2), no reactivity with target serotypes (n=8) or cross-reactivity with non-target serotypes (n=20). Dilution of antisera resulted in a further 27 reagents passing QC. The remaining three reagents passed QC when prepared without centrifugation and wash steps. Protein estimates indicated that latex reagents that failed QC when prepared using the PCP method passed when made with antiserum containing ≤ 500 μg/ml of protein. Sixty-one nasopharyngeal isolates were serotyped with our in-house latex agglutination reagents, with the results showing complete concordance with the Quellung reaction. Conclusions The method described here to produce latex agglutination reagents allows simple and efficient serotyping of pneumococci and may be applicable to latex agglutination reagents for typing or identification of other microorganisms. We recommend diluting antisera or removing centrifugation and wash steps for any latex reagents that fail QC. Our latex reagents are cost-effective, technically undemanding to prepare and remain stable for long periods of time, making them ideal for use in low-income countries. PMID:23379961

Chemical speciation and recovery of gold(I, III) from wastewater and silver by liquid-liquid extraction with the ion-pair reagent amiloride mono hydrochloride and AAS determination.

PubMed

El-Shahawi, M S; Bashammakh, A S; Bahaffi, S O

2007-06-15

A novel and low cost liquid-liquid extraction procedure for the separation of gold(III) at trace level from aqueous medium of pH 5-9 has been developed. The method has been based upon the formation of a yellow colored ternary complex ion associate of tetrachloro gold(III) complex anion, AuCl(4)(-) with the ion-pair reagent 1-(3,5-diamino-6-chloropyrazinecarboxyl) guanidine hydrochloride monohydrate, namely amiloride, DPG(+).Cl(-). The effect of various parameters, e.g. pH, organic solvent, shaking time, etc. on the preconcentration of gold(III) from the aqueous media by the DPG(+).Cl(-) reagent has been investigated. The colored gold species was quantitatively extracted into 4-methyl pentan-2-one. The chemical composition of the ion associate of DPG(+).Cl(-) with AuCl(4)(-) in the organic solvent has been determined by the Job's method. The molar absorptivity (2.19x10(4)Lmol(-1)cm(-1)) of the associate DPG(+).AuCl(4)(-) at 362nm enabled a convenient application of the developed extraction procedure for the separation and AAS determination of traces of aurate ions. Mono-valence gold ions after oxidation to gold(III) with bromine water in HCl (1.0molL(-1)) media have been also extracted quantitatively from the aqueous media by the developed procedure. The chemical speciation of mono- and/or tri-valence gold species spiked to fresh and industrial wastewater samples has been achieved. The method has been also applied successfully from the separation of gold(I) and gold(III) species from metallic ions and silver. The developed method has also the advantage of freedom from most diverse ions.

Photolytic AND Catalytic Destruction of Organic Waste Water Pollutants

NASA Astrophysics Data System (ADS)

Torosyan, V. F.; Torosyan, E. S.; Kryuchkova, S. O.; Gromov, V. E.

2017-01-01

The system: water supply source - potable and industrial water - wastewater - sewage treatment - water supply source is necessary for water supply and efficient utilization of water resources. Up-to-date technologies of waste water biological treatment require for special microorganisms, which are technologically complex and expensive but unable to solve all the problems. Application of photolytic and catalytically-oxidizing destruction is quite promising. However, the most reagents are strong oxidizers in catalytic oxidation of organic substances and can initiate toxic substance generation. Methodic and scientific approaches to assess bread making industry influence on the environment have been developed in this paper in order to support forecasting and taking technological decisions concerning reduction of this influence. Destructive methods have been tested: ultra violet irradiation and catalytic oxidation for extraction of organic compounds from waste water by natural reagents.

MgCl 2 : The Key Ingredient to Improve Chloride Containing Electrolytes for Rechargeable Magnesium-Ion Batteries

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

Pan, Baofei; Huang, Jinhua; Sa, Niya

The effect of MgCl2 on a series of chloride containing magnesium electrolytes was investigated. In the presence of extra MgCl2, the electrochemical properties of Grignard reagents (RMgCl, R = Ph, Et, iPr) were significantly improved, and the advance of MgCl2 was further demonstrated in Mg-Mo6S8 rechargeable batteries with improved capacities and much smaller over-potentials. MgCl2 was then further proven to be powerful reagent to improve the performance of well-established strong Lewis acid derived magnesium electrolytes including the “all-phenyl” complex (APC) and alkoxide-based magnesium electrolytes. The results suggest that MgCl2 salt is a very important species to benefit all chloride containingmore » electrolytes for rechargeable magnesium-ion batteries.« less

Visible light photocatalysis as a greener approach to photochemical synthesis.

PubMed

Yoon, Tehshik P; Ischay, Michael A; Du, Juana

2010-07-01

Light can be considered an ideal reagent for environmentally friendly, 'green' chemical synthesis; unlike many conventional reagents, light is non-toxic, generates no waste, and can be obtained from renewable sources. Nevertheless, the need for high-energy ultraviolet radiation in most organic photochemical processes has limited both the practicality and environmental benefits of photochemical synthesis on industrially relevant scales. This perspective describes recent approaches to the use of metal polypyridyl photocatalysts in synthetic organic transformations. Given the remarkable photophysical properties of these complexes, these new transformations, which use Ru(bpy)(3)(2+) and related photocatalysts, can be conducted using almost any source of visible light, including both store-bought fluorescent light bulbs and ambient sunlight. Transition metal photocatalysis thus represents a promising strategy towards the development of practical, scalable industrial processes with great environmental benefits.

Intercalated layered clay composites and their applications

NASA Astrophysics Data System (ADS)

Phukan, Anjali

Supported inorganic reagents are rapidly emerging as new and environmentally acceptable reagents and catalysts. The smectite group of layered clay minerals, such as, Montmorillonite, provides promising character for adsorption, catalytic activity, supports etc. for their large surface area, swelling behavior and ion exchange properties. Aromatic compounds intercalated in layered clays are useful in optical molecular devices. Clay is a unique material for adsorption of heavy metals and various toxic substances. Clay surfaces are known to be catalytically active due to their surface acidity. Acid activated clays possess much improved surface areas and acidities and have higher pore volumes so that can absorb large molecules in the pores. The exchangeable cations in clay minerals play a key role in controlling surface acidity and catalytic activity. Recently, optically active metal-complex-Montmorillonite composites are reported to be active in antiracemization purposes. In view of the above, a research work, relating to the preparation of different modified clay composites and their catalytic applications were carried out. The different aspects and results of the present work have been reported in four major chapters. Chapter I: This is an introductory chapter, which contains a review of the literature regarding clay-based materials. Clay minerals are phyllosilicates with layer structure. Montmorillonite, a member of smectite group of clay, is 2:1 phyllosilicate, where a layer is composed of an octahedral sheet sandwiched by two tetrahedral sheets. Such clay shows cation exchange capacity (CEC) and is expressed in milli-equivalents per 100 gm of dry clay. Clays can be modified by interaction with metal ion, metal complexes, metal cluster and organic cations for various applications. Clays are also modified by treating with acid followed by impregnation with metal salts or ions. Montmorillonite can intercalate suitable metal complexes in excess of CEC to form double or pseudo-trilayer composites. Metal ion and metal ion metal salts intercalated on Montmorillonite are efficient catalysts for Friedel-Crafts (FC) reactions, such as benzylation of benzene, synthesis of Raspberry ketone [4-(4'-hydroxyphenyl)butan-2-one] etc. Montmorillonite clay can be used as a good support for controlled release of pesticides and medicinal drugs, adsorbent for cationic dyes, toxic substances and heavy metals effective adsorbent for radioactive and toxic industrial wastes,...