Search

The viability of pathogens at interfaces can be disrupted by the presence of (cationic) charge and chelating groups. We report on the synthesis of silicone dendrimers and linear polymers based on a motif of hexadentate ligands with the ability to capture and deliver metal ions. Mono-, di- or trialkoxysilanes are converted in G1 to analogous vinylsilicones and then, iteratively using the Piers-Rubinsztajn reaction and hydrosilylation, each vinyl group is transformed into a trivinyl cluster at G2. The thiol-ene reaction with cysteamine or 3-mercaptopropionic acid and the trivinyl cluster leads to hexadentate ligands 3 × N–S or 3 × HOOC–S. The compounds were shown to effectively capture a variety of metals ions. Copper ion chelation was pursued in more detail, because of its toxicity. On average, metal ions form chelates with 2.4 of the three ligands in a cluster. Upon chelation, viscous oils are converted to (very) soft elastomers. Most of the ions could be stripped from the elastomers using aqueous EDTA solutions, demonstrating the ability of the silicones to both sequester and deliver ions. However, complete ion removal is not observed; at equilibrium, the silicones remain ionically crosslinked. [ABSTRACT FROM AUTHOR]

QDs has been deftly explored, studied, and optimized because of its unique optical and physicochemical properties. However, their high production and usage arouses the concern of accidental or unavoidable release in environment which can have toxic impact on animals. It is thus indispensable to comprehend its non-target effect. In the present study, interaction of vital digestive enzyme α-amylase was investigated with water-soluble mercaptopropionic acid (MPA)-capped CdSe QDs of five different sizes (1.9 nm, 2.3 nm, 2.5 nm, 3.3 nm, and 3.9 nm) by various spectroscopic techniques. Distinctive increase in absorption spectra and fluorescence quenching of α-amylase was observed chiefly due to α-amylase-CdSe QDs ground state complex formation. Binding constant (Kb), binding sites (n), and quenching constant (Ksv) were also determined. The results illustrated that binding of α-amylase with CdSe QDs followed 1:1 stoichiometry and induced conformational changes in dose- and size-dependent manner. Effect on α-amylase activity in complex form with size varied CdSe QDs suggested higher inhibition of enzymatic activity by smaller size QDs as compared to larger size. Molecular docking of MPA ligand with α-amylase revealed that interaction was majorly driven by hydrophobic forces. It further suggested that MPA did not interact with active site of α-amylase, thus acting as non-competitive inhibitor. The study thus involved a comprehensive analysis of the structural and functional modulation in α-amylase by interaction with hydrophilic MPA-capped CdSe QDs of different sizes. [ABSTRACT FROM AUTHOR]

Gold electrodes are often not suitable for dopamine measurements as dopamine creates a non-conducting polymer layer on the surface of the electrodes, which leads to increased amount of electrode passivity with the gradual increase in voltammograms measurement. This work presents the impedance spectroscopy and cyclic-voltammetry comparative study for dopamine detection with two modifications for the surface of Au electrodes; cysteamine and mercaptopropionic acid for thermally bonded and ultrasonically welded microfluidic chips, respectively. The effects of optimized tubing selection, bonding techniques, and cleaning methods of the devices with KOH solution played crucial role for improvements in dopamine detection, which are observed in the results. Furthermore, comparison for the modification with unmodified chips, and finding the unknown concentration of dopamine solution using flow injection techniques, is also illustrated.

Objectives: Metallo-beta lactamase (MBL) producing non fermenter Gram negative bacilli is an emerging warning and cause of worry as they have established as one of the most feared resistance mechanisms and are the foremost cause of nosocomial infections worldwide. Carbapenem, including Imipenem, Meropenem and Doripenem are often used as a last remedy for treatment of infections caused by Pseudomonas aeruginosa, Acinetobacter and other Gram-negative. The present study was designed to explore the distribution of imipenem resistant non-fermenter Gram-negative bacilli isolates in different age groups. Study Design: Cross sectional Descriptive study. Setting: Microbiology laboratory, PGMI, Lahore. Period: January 2015 to December 2015. Material & Methods: 53 imipenem resistant NFGNB that were isolated from appropriate sampling of patients suffering from several infections were analyzed by using different standard microbiological techniques like microscopy, culture methods, biochemical reactions and antibiotic susceptibility using Kirby-Bauer method. MBL recognition was performed by imipenem-2MPA double disc synergy test (DDST). Results: This study shows the frequency of imipenem resistant non-fermenter Gram-negative bacilli isolated from various clinical wards. Maximum NFGNB were recovered from surgery/surgical allied 35.84% followed by ICU 28.3%, medicine/medicine allied 20.75%, pediatrics 9.4% and gynae/obs 5.6% respectively. MBL production was identified among different imipenem resistant non-fermenter Gram-negative bacilli isolates by DDST using 2-MPA. Out of total 53 imipenem resistant non-fermenter Gram Negative Bacilli 37 Pseudomonas aeruginosa 20(54.05%) were MBL positive. Out of 13 Acinetobacter baumannii and 2 Pseudomonas luteola, 11(84.61%) Acinetobacter baumannii and 1(50%) Pseudomonas luteola were positive for MBL production. None of the Acinetobacter junii indicated MBL production. Conclusion: Double disc synergy test is operational for detection of MBL producers among NFGNB. It can be established in our routine clinical microbiology laboratories, for the MBL recognition especially in imipenem resistant isolates as of its cost efficiency. [ABSTRACT FROM AUTHOR]

• MPA capped ZnSe:Mn NCs were prepared in aqueous solution. • The mechanism for the stability of ZnSe:Mn@MPA NCs have been investigated. • Three distinguished stages appeared during storage of ZnSe:Mn@MPA NCs. • The peculiar alteration of the solution pH was also observed during storage. • The stability of ZnSe:Mn@MPA NCs is governed by the oxidization of MPA. 3-mercaptopropionic acid (MPA) capped ZnSe:Mn semiconductor nanocrystals (ZnSe:Mn@MPA NCs) were prepared in aqueous solution. It was found that the NCs appear as macroscopic precipitates after stored for 10 d. The change law of the NCs in three distinguished stages was studied. The results displayed that the optical stability of as-prepared NCs capped with MPA stabilizer is correlated with the depletion of MPA, which leads to the decomposition of ZnSe:Mn NCs under the existence of photo-induced holes. ZnS protective layer was formed on the surface of ZnSe:Mn@MPA NCs by epitaxial growth method to inhibit the photodegradation of MPA. [ABSTRACT FROM AUTHOR]

Functional metal-organic frameworks (MOFs), especially those based on sulfur and nitrogen atoms, were frequently applied for the removal of Hg(II) ions. However, a systematic study on the cooperative or competitive roles of -SH and -NH 2 functions in the presence of secondary mechanisms (proton transfer and redox) is still rare. In this work, the UiO-66 framework (Zr 6 (OH) 4 O 4 (BDC) 6 , BDC 2- = benzene-1,4-dicarboxylate) was decorated with functional monocarboxylate linkers including glycine (Gly), mercaptopropionic acid (Mer), and cysteine (Cys). Due to the molecular similarity of these functional linkers, the coordination affinity between the amine and thiol sites with Hg(II) ions can be compared, and the effect of proton transfer and redox mechanisms on the possible thiol···Hg(II) and amine···Hg(II) interactions can be investigated. The results show that the Cys@UiO-66 framework can adsorb 1288 mg g -1 of Hg(II), while Mer@UiO-66 and Gly@UiO-66 can adsorb 593 and 313 mg g -1 at pH = 7 and 500 ppm, respectively. This is due to the facts that both the amine and the thiol functions of the Cys@UiO-66 framework show synergism in Hg(II) removal, and the secondary mechanisms reduce the affinity of thiol in Mer@UiO-66 and amine in Gly@UiO-66 frameworks in the removal process of Hg(II) ions. Free -SH sites in Mer@UiO-66 undergo a redox convert to -SO 3 H groups, and free protonated -NH 2 sites in Gly@UiO-66 do not fully deprotonate during Hg(II) removal. Yet, in the case of Cys@UiO-66, free protonated -NH 2 sites are fully deprotonated, and free SH sites did not convert to -SO 3 H groups during Hg(II) removal. These observations show that the redox and proton transfer mechanisms can negatively affect the adsorption capacity of functional MOFs containing free -SH and -NH 2 groups. So, not only the functionalization but also control over secondary mechanisms in the removal process are necessary parameters to improve the affinity between functional MOFs and Hg(II) ions.

A new, label-free, highly sensitive, and selective fluorescent “quenching-recovery” model for the detection of DNA was developed through mercaptopropionic acid (MPA)- capped cadmium telluride (CT) quantum dots (QDs) aggregation. At first, imipramine hydrochloride (IMP) effectively quenched the fluorescence of MPA-CT QDs due to their aggregation, in the “quenching” mode. Then, with the addition of DNA, the binding reaction of IMP to DNA was happened and the fluorescence intensity of MPA-CT QDs was raised, in the following “recovery” mode. Several parameters affect the sensitivity of the method were optimized. Under the optimal conditions, the linear dependence of the fluorescence signal and the concentration of DNA was in the range of 23.0 pmol L −1 –10.8 nmol L −1 , with a detection limit of 7.0 pmol L −1 . This analytical fluorescent reversible “quenching-recovery” sensor offered a method for the detection of DNA with excellent sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

Poly(acrylic acid), PAA, has been mixed in solution with silver nanoparticles, obtained by chemical reduction of silver nitrate. Two different sulfur-containing organic compounds have been used as stabilizers of Ag nanoparticles: mercaptosuccinic acid (MSA) and 3-mercaptopropionic acid (MPA). The formation of Ag nanoparticles has been monitored by UV-Vis spectroscopy. The morphology and composition of obtained nanomaterials has been studied by electron microscopy techniques (SEM/EDX and HR-TEM). Nanomechanical properties of nanocomposites (adhesion and nanohardness) have been investigated by Atomic Force Microscopy (AFM). Thermal stability has been determined using thermogravimetric analysis. The exposure of specimens to UV radiation allowed to observe the changes in the nanoparticle structure and to estimate nanocomposite photostability. MSA has proved to be a better stabilizer of Ag nanoparticles immediately after the synthesis, when MPA provides better storage stability. MPA has allowed for the creation of nanoparticles using mixed reduction (chemical/photochemical) of AgNO. It has been found that the nanocomposite materials are stable for 12 months of storage in solution and in solid form. [ABSTRACT FROM AUTHOR]

Mercaptoethanol (ME), mercaptopropionic acid (MPA) and L-cysteine (L-Cys) having -SH functional groups were used as surface passivating agents for the wet chemical synthesis of ZnS nanoparticles. The effect of the thiol group on the optical and photoluminescence (PL) properties of ZnS nanoparticles was studied. L-Cysteine-capped ZnS nanoparticles showed the highest PL intensity among the studied capping agents, with a PL emission peak at 455 nm. The PL intensity was found to be dependent on the concentration of Zn2+ and S2- precursors. The effect of buffer on the PL intensity of L-Cys-capped ZnS nanoparticles was also studied. UV/Vis spectra showed blue shifting of the absorption edge. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We synthesized CdS Quantum dots (QDs) via the irradiation of a $CdCl_{2^ + } $ mercaptopropionic acid (MPA) aqueous solution with a 10 MeV electron beam. Radiolytic synthesis using electron beam irradiation processes occurs in water that results in the formation of CdS QDs through the reactions mediated by hydrated electrons, e. Photoluminescence (PL) measurements revealed that in the case of the MPA-rich condition (with an excess of MPA ions), we can reduced the emission intensity from surface defects at over 1/5 of the [CdCl]/[MPA] molar concentration. The results of transmission electron microscopy (TEM) and UV-vis absorption spectroscopy revealed small particle sizes (2.1-4.7 nm) with good monodispersity. [ABSTRACT FROM AUTHOR]

Cationic 1,2-dioleoyl trimethyl ammonium propane (DOTAP) and neutral 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) are anchored on cysteamine (cyst), mercaptopropionic acid (MPA) monolayer (thiol monolayers) modified on an individual gold transducer. DOTAP and DOPE are mixed with gold nanoparticle (AuNP) to form spherical liposome-AuNP. The electrochemical behaviors of the surface attached DOTAP-AuNP and DOPE-AuNP in presence of [Fe(CN)] depend on the method of layer formation. Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and ultraviolet (UV)-visible spectroscopic techniques are used to characterize the liposome-AuNP nanocomposite. The studies indicate stability of spherical liposome-AuNP on the gold transducer. Label-free DNA hybridization detection on these surfaces reveals different detection limits. Confocal laser scanning microscopy (CLSM) is used to confirm the cell transfection. [ABSTRACT FROM AUTHOR]

Highlights: [•] The synthesis and characterization of GNR was performed. [•] Study of the binding of MPA onto gold nanorods surface was performed. [•] FTIR study was made to decide if MPA replaces the CTAB onto the surface of GNR. [•] The conclusion: a large part of CTAB is replaced by MPA (62%). [ABSTRACT FROM AUTHOR]

Abstract: CdTe and CdTe@ZnS quantum dots (QDs) capped with 3-mercaptopropionic acid (MPA), thioglycolic acid (TGA), or glutathione (GSH) have been employed for the first time as luminescent probes for the sensitive and selective detection of peroxynitrite (ONOO−) in aqueous solution. The sensitivity of the proposed probe followed the order: MPA–TGA–CdTe@ZnS>GSH–TGA–CdTe@ZnS>MPA–CdTe QDs. The varying degree of quenching is elucidated based on the QD–thiolate bond of CdTe@ZnS being more sensitive to oxidation from ONOO− than CdTe. The selectivity of the probe in the presence of co-existing species followed the order: GSH–TGA–CdTe@ZnS>MPA–TGA–CdTe@ZnS>MPA–CdTe QDs. QDs capped with MPA showed less selectivity for ONOO− than GSH. The best limit of detection (LOD) of 12.6nM was obtained for MPA–TGA–CdTe@ZnS QDs. Time-resolved fluorescence measurements indicated that the interaction between ONOO− and the QDs is static in nature. [Copyright &y& Elsevier]

Four types of water-soluble luminescent quantum dots (QDs) whose surface was functionlaized with thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), or glutathione (GSH), were investigated for the sensitive and selective detection of hydroxyl radical (OH) in aqueous media. It was found that the type of capping agent and QD influenced the sensitivity of the probe. The order of sensitivity of the probe was: GSH-CdTe@ZnS > MPA-CdTe@ZnS > TGA-CdTe > MPA-CdTe QDs. Under the optimum conditions, a limit of detection as low as 8.5 × 10 M was obtained using GSH-CdTe@ZnS. The effects of foreign reactive oxygen species and the Fenton reactants and products as possible interferences on the proposed probe were negligible for CdTe@ZnS QDs. Besides, experimental results indicated that CdTe@ZnS QDs were more attractive for the selective recognition of OH than CdTe QDs. The mechanistic reaction pathway between the QDs and OH is proposed. [ABSTRACT FROM AUTHOR]

This review describes the reactions of β-mercaptoalkanoic acids as building blocks for the synthesis of polyfunctionalized thiazolidinones with pharmacological interest. Annelated thiazolidinones were prepared by a cyclocondensation reaction of α/β-mercaptoalkanoic acids with aldimines. This reaction takes place by a nucleophilic addition, followed by cyclization concomitant with elimination of water. The objective of this survey is to provide a comprehensive account of the synthetic utility of β-mercaptoalkanoic acids to build various heterocycles and their potential to develop better chemotherapeutic agents. [ABSTRACT FROM AUTHOR]

Abstract: We investigated a simple route for synthesizing CdS nanocrystals (NCs) via irradiation of a CdCl2 +mercaptopropionic acid (MPA) aqueous solution with a 10-MeV electron beam without using any additional sulfur precursors or stabilizers. When the concentration of the MPA was fixed to 2.5mM, the morphology and optical properties of the NCs were changed by varying the CdCl2 concentration. Based on transmission electron microscopy (TEM) imaging, a 0.4mM concentration of CdCl2 (the-MPA rich case) created only spherical quantum dots (QDs) with an average diameter of 6.6nm. When the concentration of CdCl2 was increased to 5mM (the cadmium-rich case), nanorods with an average diameter of 5.3nm and an average aspect ratio of 8.2 were formed along with QDs with diameter of 4.9nm. The crystalline structures of the NCs were verified to be hexagonal. [Copyright &y& Elsevier]

Abstract: This work reports on the synthesis of several novel water soluble metallophthalocyanines containing Zn2+, In3+, Ga3+ or Si4+ as central metal ions and tetra substituted with mercaptoacetic acid and mercaptopropionic acid. The complexes were characterized using infra red, nuclear magnetic resonance and mass spectroscopies as well as elemental analysis. All the complexes are water soluble but the majority are highly aggregated in water and organic solvents. The complex containing Zn as a central metal and mercaptopropionic acid as a substituent was not aggregated allowing for the determination of photophysical parameters. This complex had triplet state quantum yield of 0.61 in DMF and 0.88 in DMSO while the fluorescence quantum yield was 0.13 in DMSO. The determination of photophysical properties of the complex containing Zn as a central metal and mercaptopropionic acid were carried out in the presence of mercaptopropionic acid capped CdTe quantum dots. There is an increase in triplet state quantum yield from 0.88 (for the phthalocyanine alone) to 0.94 (in the presence of CdTe quantum dots) in DMSO. [Copyright &y& Elsevier]

Abstract: The photophysical properties of two newly synthesized phthalocyanines (Pcs) were studied in the presence and the absence of 3-mercaptopropionic acid (MPA) capped quantum dots (QDs). Energy transfer processes resulting from the combination of QDs and the Pcs: 4-(tetrakis-5-(trifluoromethyl)-2-mercaptopyridinephthalocyaninato)zinc(II) (TtfmMPyZnPc, 3) and 4-(tetrakis-5-(trifluoromethyl)-2-pyridyloxyphthalocyaninato) zinc(II) (TtfmPyZnPc, 4) were also studied. The photophysical properties of the Pcs in the presence of QDs were enhanced and Förster resonance energy transfer (FRET) was observed with the phthalocyanines used. The efficiency of FRET between the QDs and TtfmMPyZnPc and TtfmPyZnPc was found to be 0.31% and 0.45% in DMSO and 0.24% and 0.32% in pyridine, respectively. The triplet state quantum yields for TtfmMPyZnPc and TtfmPyZnPc were found to be 0.86 and 0.74 in DMSO and 0.83 and 0.76 in pyridine. [Copyright &y& Elsevier]

Abstract: Aryldiazepinothiophenones 4 were prepared from the reaction of o-phenylenediamines with acetone in the presence of 2-mercaptocarboxylic acids along with thiazolobenzodiazepines 6, thiazolobenzimidazoles 7 and 1,5-benzodiazepines 5, which were obtained as by-products. The benzodiazepinothiophenones 4a–d and the benzodiazepines 5a–d were also isolated from the reaction of o-phenylenediamines 1a–c with phorone. Structural assignments of the new compounds as well as complete assignment of 1H and 13C NMR signals were based on the analysis of their 1H and 13C NMR (1D and 2D), IR, MS and elemental analysis data. Compounds 4 were evaluated for aldose reductase inhibition and also as antioxidants. [Copyright &y& Elsevier]

Abstract: Förster resonance energy transfer (FRET) studies were carried out with CdTe quantum dots (QDs) synthesized in aqueous phase and various tetrasulfonated metallophthalocyanines (MPcS4, M=aluminum ((OH)AlPcS4), zinc (ZnPcS4), silicon ((OH)2SiPcS4) and germanium ((OH)2GePcS4) in a H2O:MeOH (1:1) solvent mixture. The QDs studied were capped with thioglycolic acid (TGA) or mercaptopropionic acid (MPA) with sizes ranging from 2.3 to 3.7nm. Non-radiative energy transfer from QDs emission to MPcS4 complexes was observed. Study of the photophysics of the MPcs in the presence of the QDs revealed high triplet state quantum yields (Φ T, ranging from 0.41 to 0.85 in the presence of QDs), with corresponding long triplet state lifetimes (τ T, which ranged from 140 to 610μs in the presence of QDs) to allow for photosensitized reactions to occur. The efficiency of energy transfer and the donor–acceptor distance between the MPcs and the QDs were also evaluated. [Copyright &y& Elsevier]

Abstract: Tetrapositively charged phthalocyanines and CdTe quantum dots (QDs) capped with thioglycolic acid (TGA) and mercaptopropionic acid (MPA) were synthesized. The response of the tetrapositively charged zinc phthalocyanines in the presence of quantum dots was studied. Aggregation and charge transfer were observed for [tetramethyl-2,(3)-[tetra-(2-mercaptopyridinephthalocyaninato)]zinc(II)]4+ (TmTMPyZnPc), however aggregation proved to be the more prominent process of the two. Fluorescence resonance energy transfer (FRET) was observed with [tetramethyl-2,(3)-[tetra-(2-pyridyloxyphthalocyaninato)]zinc(II)]4+ (TmTPyZnPc). In the FRET study the efficiency of FRET with TmTPyZnPc was determined to be 21% for both MPA and TGA capped CdTe QDs. For the charge transfer study the fluorescence of the quantum dots was quenched by the TmTMPyZnPc used, and from these quenching studies the quenching constants, binding constants and number of binding sites on the quantum dots were determined. [Copyright &y& Elsevier]

Abstract: Luminescent water-soluble CdTe quantum dots (QDs) capped with different thiol carboxylic acids were synthesized in aqueous medium and then cross linked to bovine serum albumin (BSA) with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Enhancement of fluorescence emission intensity occurred for QDs in the presence of bovine serum albumin (BSA, mixed or linked) signifying inhibition of non-radiative recombination of the surface vacancies. Fluorescence studies reveal a positive deviation behaviour suggesting the occurrence of static and dynamic mechanisms of quenching together which was accounted for by the modified Stern–Volmer equation. [Copyright &y& Elsevier]

A thermosensitive polymer that can either be soluble or insoluble in water was synthesized by electron beam irradiation N-isopropylacrylamide (NIPAM) and β-mercaptopropionic acid (MPA) without the presence of initiator. The polymer was then reacted with p-aminobenzamidine (PABA) using water-soluble carbodiimide (WSC) to introduce an affinity ligand. Radiation grafting of poly(NIPAM) and conjugation of ligand was successfully completed. It was found that the graft reaction could be done at higher dose and carboxyl group was introduced during irradiation of samples in air. Production and precipitate of the carboxylated poly(NIPAM) were investigated. Some results of direct radiation polymerization in this system are also given. The effect of radiation characteristics such as irradiation dose on the lower critical solution temperature (LCST) and conjugation of PABA on the prepared poly(NIPAM) has also been investigated. The precipitate of the grafted polymer has thermal sensitivity and their LCST is close to 35°C. [ABSTRACT FROM AUTHOR]

Highly monodisperse superparamagnetic iron oxide nanoparticles (SPIONs, 7.5 nm gamma- F2O3) were synthesized by thermal decomposition of iron pentacarbonyl and consecutive aeration in organic medium. By treating with a small amount of iron pentacarbonyl, Fe-rich surface has been formed on SPION. Water-dispersible SPIONs (SPION-MPA) were prepared by Fe-S covalent conjugation between Fe-rich SPION and mercaptopropionic acid (MPA) and then, transformed to SPION-MPA-dextran composite by physical adsorption of biocompatible polymer dextran. The hydrodynamic diameter of SPION-MPA-dextran was in the range of 225~237 nm in water. MR contrast and spin-spin relaxation intensity of our SPION-MPA-dextran were similar to those of the commercial products, Ferridex and Resovist. [ABSTRACT FROM PUBLISHER]

Aim: To examine the effect of sulfur-containing compounds on the growth of anaerobic rumen fungi and the fibrolytic rumen bacteria Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogenes in pure culture and within the cattle rumen . Methods and Results: The effect of two reduced sulfur compounds, 3-mercaptopropionic acid (MPA) or 3-mercapto-1-propanesulfonic acid as the sole S source on growth of pure fibroyltic fungal and bacterial cultures showed that these compounds were capable of sustaining growth. An in vivo trial was then conducted to determine the effect of sulfur supplements (MPA and sodium sulfate) on microbial population dynamics in cattle fed the roughage Dichanthium aristatum. Real-time PCR showed significant increases in fibrolytic bacterial and fungal populations when cattle were supplemented with these compounds. Sulfate supplementation leads to an increase in dry matter intake without a change in whole tract dry matter digestibility. Conclusions: Supplementation of low S-containing diets with either sodium sulfate or MPA stimulates microbial growth with an increase in rumen microbial protein supply to the animal. Significance and Impact of the Study: Through the use of real-time PCR monitoring, a better understanding of the effect of S supplementation on discrete microbial populations within the rumen is provided. [ABSTRACT FROM AUTHOR]

Abstract: A method is developed for quantitative determination of glucose using electrochemical impedance spectroscopy (EIS). The method is based on immobilized glucose oxidase (GOx) on the topside of gold mercaptopropionic acid self-assembled monolayers (Au-MPA-GOx SAMs) electrode and mediation of electron transfer by parabenzoquinone (PBQ). The PBQ is reduced to hydroquinone (H2Q), which in turn is oxidized at Au electrode in diffusion layer. An increase in the glucose concentration results in an increase in the diffusion current density of the H2Q oxidation, which corresponds to a decrease in the faradaic charge transfer resistance (R ct) obtained from the EIS measurements. Glucose is quantified from linear variation of the sensor response (1/R ct) as a function of glucose concentration in solution. The method is straightforward and nondestructive. The dynamic range for determination of glucose is extended to more than two orders of magnitude. A detection limit of 15.6μM with a sensitivity of 9.66×10−7 Ω−1 mM−1 is obtained. [Copyright &y& Elsevier]

Abstract: The comparison of assembly structure and property of mercaptopropionic acid (MPA) self-assembled monolayers (SAMs) on gold nanoparticle modified electrode (nanogold electrode) with that on planar gold electrode was studied by cyclic voltammetry (CV). The electron transfer of through the MPA SAMs and Cu underpotential deposition (UPD) on MPA-covered electrode indicated that MPA molecules assemblied on the planar gold electrode could form a very compact layer, which could surpass the electron transfer K3Fe(CN)6 greatly, whereas on the surface on the nanogold, which curvature make the compact packing loose. The reductive desorption in 0.5M KOH and oxidative desorption in phosphate buffer solution (PBS) (pH 6.8) showed that gold nanoparticles could enhance the Au–S bond and stabilize the MPA molecules. [Copyright &y& Elsevier]

Nanometer scale structures of self-assembled films consisting of 3-mercaptopropionic acid (MPA) were formed by using electric stimuli between scanning tunneling microscope (STM) Au tips and gold surfaces. The obtained structures were compared with those using bare gold surfaces and hexanethiol films on Au(1 1 1) under the same conditions. X-ray photoelectron spectroscopy measurements revealed that self-assembled ultrathin films of the corresponding thiol molecules were fabricated on Au(1 1 1) by a facile atmospheric-vapor-adsorption (AVA) method without solvent. Comparison of nano-structure formation suggested that the self-assembled thin films of 3-mercatopropionic acid molecules gave nano-dots below the height of voltage pulses where gold atom emission from Au tips and surface evaporation of Au(1 1 1) take place. It was found that 3-mercaptopropionic acid films easily produced much better nano-dots on Au(1 1 1) than hexanethiol films probably due to the formation of hydrogen bonding networks and/or the reactions of 3-mercaptopropionic acid when electric pulses were applied to the films. [Copyright &y& Elsevier]

The composition of the amino acid and amine derivatives obtained with the o-phthaldialdehyde (OPA)/3-mercaptopropionic acid (MPA) and with the OPA/N-acetyl-l-cysteine (NAC) reagents was investigated by on-line HPLC–electrospray ionization MS. The initially formed derivatives proved to be, as expected, the corresponding isoindoles while their transformed species contained one additional OPA molecule. Based on the MS spectra of all transformed OPA derivatives a reaction pathway is suggested. This reaction mechanism was supported both by the molecular ions of the endproducts and by the presence of several selective fragment ions that served as an explanation to the structure of the believed to be less stable OPA derivatives. It has been shown that more than one OPA derivative forms in all those cases when the compound to be derivatized does contain the NH2–CH2–R moiety. Thus, amino acids like e.g. glycine, histidine, β-alanine, γ-aminobutyric acid, ∊-aminocaproic acid, ornithine, and also several aliphatic mono- and diamines provide more than one OPA derivative. Analytical consequences of this experience were utilized by altering the reagent’s composition. Reagents containing mole ratios of [OPA]/[MPA] or [OPA]/[NAC]=1/50 resulted in two benefits, simultaneously: (i) in a decrease of the transformation rate of the initially formed derivative, and, (ii) in an increase of the overall stability of the total of derivatives. [Copyright &y& Elsevier]

The effects of the glutamic acid decarboxylase inhibitor 3-mercaptopropionic acid (MPA) on the concentration of GABA in the mouse brain were studied. MPA completely inhibited the postmortem increase in GABA. This effect was used in order to achieve a maximal inhibition of the GABA synthesis in vivo during 67.5 minutes before killing by giving the drug repeatedly (50 mg/kg+6×10 mg/kg i.p.) to mice pretreated with chloral hydrate (100 mg/kg i.p., 65 min before killing). Such a treatment with MPA markedly reduced the accumulation of GABA following inhibition of the GABA transaminase by aminooxyacetic acid but it did not change the endogenous concentration of GABA. This discrepancy might be due to inhibition of the impulse-evoked release of GABA following MPA. [ABSTRACT FROM AUTHOR]

The effects of several drugs and other treatments on the regional levels of Ca in the brain of mice and rats were determined with an automated assay, based on the formation of a fluorescent calcein complex in a continuous flow system. The method is linear (between 1.5 and 5 μg Ca ml), specific (no other cations present in the brain showed fluorescence) and sensitive (10-100 mg brain tissue can be analyzed). No major effects with the following drugs, given once or repeatedly to mice at high doses were found: morphine, naloxone, haloperidol, sulpiride, chlordiazepoxide, reserpine, ethanol, mercaptopropionic acid, or pentobarbital. Cold stress produced a transient increase in the regional levels of Ca in the mouse brain. Lithium sulphate produced a small increase of brain Ca 24 h after a high and toxic dose. Sleep deprivation for 24 h was ineffective in these experiments. Local application of kainic acid and tetrodotoxine to the rat striatum had no acute effects, but kainic acid produced a five to tenfold increase in the levels of striatal Ca 2 weeks after injection. The present study does not support earlier published findings, which suggested that several behaviourally active drugs produce significant decreases of brain Ca. Morever, it provides no evidence that the several therapeutic treatments that resulted in changes in body fluid Ca also alter cerebral levels of Ca. On the other hand, the present data do suggest that damage to nervous tissue substantially influences Ca metabolism. [ABSTRACT FROM AUTHOR]