Mercapto Functional Groups Research Articles

Design, synthesis, and anti-melanogenic efficacy of 2-mercaptobenzoxazoles with nanomolar tyrosinase activity inhibition

Tyrosinase is a metalloenzyme that contains copper(II) ions. We designed and synthesized eight known low-molecular-weight 2-mercaptobenzoxazole (2-MBO) analogs as tyrosinase inhibitors. Our focus was on the mercapto functional group, which interacts with copper ions. Analogs 1–3 exhibited mushroom tyrosinase inhibitory activity at the nanomolar level and demonstrated strong potency with extremely low half-maximal inhibitory concentration (IC50) values of 80–90 nM for l-dopa and 100–240 nM for l-tyrosine. Analogs 2, 4, and 5 showed the most potent anti-melanogenic effects in B16F10 cells, and their mode of action was demonstrated by kinetic analysis. Their anti-melanogenic effects were similar to the tyrosinase inhibition results, suggesting that their anti-melanogenic effects could be attributed to their tyrosinase inhibitory ability. Experiments using copper-chelating activity assays and changes in tyrosinase inhibitory activity with and without CuSO4 demonstrated that 2-MBO analogs inhibit tyrosinase activity by chelating the copper ions of tyrosinase. In conclusion, the 2-MBO analogs show potential as anti-melanogenic agents with potent tyrosinase inhibitory activity.

Highly Transparent, Robust Hydrophobic, and Amphiphilic Organic-Inorganic Hybrid Coatings for Antifogging and Antibacterial Applications.

The control of surface wettability through a combination of surface roughness, chemical composition, and structural modification has attracted significant attention for antifogging and antibacterial applications. Herein, a two-step spin-coating method for amphiphilic organic-inorganic hybrid materials with incorporated transition metal ions is presented. The coating solution was prepared via photochemical thiol-ene click reaction between the mercapto functional group in trimethylolpropane tris(3-mercaptopropionate) and the vinyl functionalized silica precursor 3-(trimethoxysilyl)propyl methacrylate. In the first step of coating, a glass substrate was coated using a solution of metal nitrate hydrates and subsequently showed hydrophobic properties. As the second step, the spin-coated glass substrate was further coated with silica nanoparticles (SiO2 NPs) and polycaprolactone triol (PCT) suspension, where the contents of SiO2 NPs were fixed at 0.1 wt %, unless otherwise noted. The coated substrate exhibited hydrophilic properties. For comparison, the coating was also formulated with the SiO2 NPs/PCT suspension without SiO2 NPs and with 0.5 wt % SiO2 NPs as well as by adjusting different coating layer thicknesses. The surface morphology and chemical compositions of the obtained coating materials were analyzed by field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The transparency and static contact angle of coated samples were measured by UV-visible spectrophotometry and drop shape analysis, respectively. It was concluded that our novel hybrid coating materials exhibited excellent antibacterial and antifogging properties with extremely high scratch resistance and transparency.

Multi-modification of Na-Y zeolite with ZnO nanoparticles, amine, and mercapto functional groups for single and simultaneous heavy metal adsorption from water system

A multi-functionalized Na-Y/ZnO/NH2/SH composite adsorbent was synthesized for Pb2+ and Ni2+ removal from single and binary aqueous systems. The prepared composites were characterized by FTIR, FESEM, XRD, BET, and N2 adsorption–desorption techniques. The effect of ZnO nanoparticles, amine, and thiol functional groups on the adsorption performance was studied in a batch system. The adsorption behavior of Pb2+ and Ni2+ ions was evaluated as a function of initial metal concentration, contact time, pH, and temperature. The adsorption process of both Pb2+ and Ni2+ ions followed the double-exponential kinetics model. Also, the investigation of isotherm models exhibited a monolayer adsorption onto the synthesized composite. The maximum adsorption capacity of Na-Y/ZnO/NH2/SH composite was found to be 177.9 mg/g for Ni2+ ions and 295.4 mg/g for Pb2+ ions. The synthesized Na-Y/ZnO/NH2/SH composite was regenerated multiple times showing a promising adsorbent with high regeneration efficiency. In a binary system, the inhibitory influence of Pb2+ ions on the Ni2+ adsorption was greater than the inhibitory influence of Ni2+ ions on the Pb2+ adsorption.

Liquid chromatography-diode array-mass spectrometric analysis of amino and mercapto compounds coupled with chloroimino derivatization reagent

A new derivatization reagent, N-(naphthalen-1-yl)-2-oxopropanehydrazonoyl chloride (UOSA54), was prepared and coupled with four drugs, bearing primary amino, secondary amino or mercapto functional groups. Glucosamine sulfate (GLU), cysteine (CYS), captopril (CAP), and vildagliptin (VIL), were used as representative reactive analytes. The prepared reagent was successfully coupled with the targeted analytes in the presence of triethylamine (TEA) as hydrochloride acceptor and acetonitrile as solvent. The resulting reaction products were separated by high-performance liquid chromatography and monitored simultaneously by diode array and triple quad mass spectrometry detectors. Enhanced DAD and electrospray ionization-MS (ESI-MS) responses were observed for the derivatized products. Complete derivatization of VIL was achieved after heating at 65 ± 3 °C for 4 min, while other analytes were derivatized instantaneously at room temperature. Both, the ESI-ionization suppression, due to the excess reagent, and matrix effect, due to co-eluted biogenic plasma constituents, were negligible. The derivatized GLU, CYS, CAP, and VIL showed a maximum absorption wavelength at 376, 417, 340, and 376 nm, with MS-limit of quantification value of 250.0, 2.0, 2.5, and 3.0 pg/μL, respectively. The relative ESI-MS response of UOSA54 derivatization products was within the range of 0.6–4.1 compared with dansylated products. The method was optimized and validated for optimal reaction product stability, sensitivity, linearity, range, precision, and accuracy. The percentage recovery was exceeding 97.2%, with an RSD value of less than 4.0%. The limit of quantification of targeted analytes was ranged from 80.0 to 0.7 pg/μL.

Functionalization of the magnetite nanoparticles with polysilsesquioxane-bearing N- and S-complexing groups to create solid-phase adsorbents

Sol–gel method based on the reaction of hydrolytic co-polycondensation of alkoxysilanes was applied to obtain composites of magnetite and silica with amino and mercapto functional groups of core–shell structure. Magnetite core ensures easy removal of materials from solutions in a quick and effective way with a help of a magnet. Using 1,2-bis(triethoxysilyl)ethane as a structure-forming agent (instead of traditional tetraethoxysilane) allowed synthesis of mesoporous samples with well-developed porous structure (specific surface area values of 400–800 m2/g). In combination with high content of available functional groups, introduced to the process of one-pot synthesis using 3-aminopropyltriethoxysilane and 3-mercaptopropyltriethoxysilane as functionalyzing agents, it endowed the synthesized composites with high sorption capacities to silver(I), copper(II), and lead(II) ions. Meanwhile, the affinity to the molecules of dyes (Acid Red 88 and Methylene Blue) was shown to be in direct correlation with the composites’ surface charges and uptake can reach 118 mg/g and 88 mg/g, respectively. These results indicate the possibility of magnetite nanoparticles’ one-step functionalization with mesoporous silica layers and simultaneous introduction of different functional groups. Such properties make them very attractive for application in adsorption technologies as effective adsorbents of metal ions as well as organic pollutants.

Buchwald–Hartwig C–N cross coupling reactions catalyzed by palladium nanoparticles immobilized on thio modified-multi walled carbon nanotubes as heterogeneous and recyclable nanocatalyst

In current research, the multi walled carbon nanotubes was functionalized with mercapto-melamine groups by covalent grafting of f-CNT with ethylenediamine, cyanuric chloride and 2-mercaptoethanol for introducing mercapto functional groups on the surface of nanotube. Consequently, the thiolated MWCNTs were applied to deposing Pd nanoparticles. The results of FTIR, Raman spectroscopy, powder XRD, energy dispersive spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX) and CHN analysis showed the successful synthesis of nanocatalyst. The scanning and transmission electron microscopes (SEM and TEM) were used to study the morphologies of the nanocatalyst. Moreover, the (MWCNTs/CC-SH/Pd) nanocatalyst was effectively applied in Buchwald–Hartwig C–N cross coupling reaction with wide variety of functionalized substrates. A variety of aryl amines were prepared through reaction of aryl halides (chloride, bromide and iodide) and amines in high yields. Remarkably, the new catalyst could be reused for six recycles without change in its catalytic activity.

Optimized mercapto-modified resorcinol formaldehyde xerogel for adsorption of lead and copper ions from aqueous solutions

Resorcinol formaldehyde (RF) xerogel was modified by mercapto functional groups for removal of Pb(II) and Cu(II) ions from aqueous solutions. The chemical structure of the mercapto-modified resorcinol formaldehyde xerogel (MRFX) was compared with the RF xerogel via Fourier transform infrared spectra (FTIR), X-ray photoelectric spectroscopy (XPS), and energy dispersive X-ray (EDX) mapping to characterize the functional groups and their dispersion in the xerogel. The results showed that the MRFX included not only thiol groups, but also sulfonic groups with higher adsorption affinity sites. The functional groups were fully dispersed in the xerogel and made a homogeneous composition. X-ray diffraction (XRD) patterns were also employed to show the effect of modifier on the phase structure of the xerogels. Moreover, the morphologies of the xerogels were observed by scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. According to the TEM micrographs, the MRFX included more nanopores than the unmodified xerogel. The MRFX was studied for adsorption tests. According to the results, the optimal pH to adsorb maximum Pb(II) and Cu(II) ions was 6. Adsorption kinetics study revealed that the adsorption process followed the pseudo-second-order kinetic equations and the adsorption equilibrium agreed much more with Langmuir rather than Freundlich model.

Simultaneous determination of cadmium, lead and mercury ions at trace level by magnetic solid phase extraction with Fe@Ag@Dimercaptobenzene coupled to high performance liquid chromatography

Pollution resulted from heavy metal ions have absorbed much attention, and it is of great importance to develop sensitive and simultaneous determination method for them with common technologies without highly sensitive instruments. We prepared a new and functional core-shell magnetic nano-material, Fe@Ag@dimercaptobenzene (Fe@Ag@DMB), by a one-step method with sodium borohydride as the reducing agent and transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) were used for characterisation. The mercapto functional groups on the newly synthesised magnetic nanoparticles could interact with Cd2+, Pb2+, and Hg2+ ions in water samples and then efficient extraction for Cd2+, Pb2+, and Hg2+ ions was achieved. DDTC-Na solution was a good elutent for elution of these ions from Fe@Ag@DMB nanoparticles. Based on these, a sensitive method was developed for simultaneous preconcentration and determination of the aforementioned ions using magnetic Fe@Ag@DMB nanoparticles as the magnetic solid phase extraction adsorbent prior to high performance liquid chromatography coupled with variable wavelength detection. Under the optimal conditions, the detection limits of the three metal ions were in the range of 0.011–0.031μgL−1, and precisions were below 2.37% (n=6). The proposed method was evaluated with real water samples, and excellent spiked recoveries achieved indicated that the developed method would be a promising tool for monitoring these heavy metal ions in water samples.

Progress in Platinum Catalysts Supported by Inorganic Carriers for Hydrosilylation

Hydrosilylation catalyzed by transition metals or their complexes is one of the most important ways to synthesize organosilicones, and platinum catalysts are widely used. Inorganic carriers supported platinum catalysts not only can avoid the disadvantages of homogeneous catalysts, such as corroding reactor, pain platinum recovery and low reaction selectivity, but also can be available for sequential reactions due to the good mechanical strength and stability in reaction medium. A lot of literatures relating to platinum catalysts supported by inorganic carriers for hydrosilylation have been published. The platinum compounds have been supported by carbon carriers, silica, metallic oxide, molecular sieve or other inorganic carriers via direct load method or complexation between platinum and vinyl, phosphino, amino, arsino or mercapto functional group modified on the surface of the carriers. The research progresses in preparation, structure and properties of inorganic carriers supported platinum catalysts for hydrosilylation during recent 15 years are summarized with the description of their development trend.

Resorcinol formaldehyde xerogels modified with mercapto functional groups as mercury adsorbent

ABSTRACTResorcinol formaldehyde xerogels are modified by mercaptopropyl‐trimethoxysilane during the sol–gel process used to produce the xerogel. The chemical modification is confirmed by Fourier‐transform infrared spectroscopy. The xerogel is then used to adsorb mercury ions from aqueous solutions. The effects of the molar ratios of the precursors as well as the catalyst and the modifier are studied on the textural properties of the xerogel and the adsorption efficiency. It is shown that the chemical modification of the resorcinol formaldehyde xerogels creates the chemical sites on the structure of the xerogel to adsorb more mercury ions and increase the adsorption efficiency. At the same time, chemical modification decreases the xerogel surface area which results in a reduction of the mercury adsorption. Therefore, there exists an optimum value for the chemical modification of the xerogel to achieve the highest adsorption efficiency. Adsorption kinetics as well as equilibrium isotherm of xerogels were examined using pseudo‐first‐ and second‐order kinetic equations, and Freundlich and Langmuir isotherm models. The adsorption kinetics was found to follow the pseudo‐second‐order kinetic equations. The experimental data was also fitted into the Longmuir model more precisely comparing the Freundlich model. Finally, a series of mercury adsorption–desorption tests proved that the optimized mercapto‐modified resorcinol formaldehyde xerogel was an efficient reusable adsorbent for mercury ions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42543.

GW24-e3722 Ebselen protected myocardium from overtraining-induced oxidative damage in rats

ObjectivesGeneration of large amount of ROS is considered to be a causative factor of structure damage or apoptotic in the myocardium and to be involved in the progress of exercise...

Mechanistic study of diclofenac and carbamazepine adsorption on functionalized silica-based porous materials

Adsorption of diclofenac and carbamazepine by hexagonal mesoporous silicate (HMS), and the amine- and mercapto-functionalized HMS derivatives (A-HMS and M-HMS, respectively), were evaluated in comparison to that for the mesoporous silicates SBA-15 and MCM-41 plus powdered activated carbon, so as to evaluate the adsorption mechanism, effects of surface functional groups, pH and temperature on the adsorption capacity of these adsorbents. The adsorption of diclofenac and carbamazepine onto all adsorbents was found to decrease rapidly in the first 30min and reach equilibrium within 4h. The adsorption kinetics and isotherm data obtained were best described by a pseudo-second-order kinetic rate model and linear isotherm model, respectively. Comparison of the adsorption capacities of HMS, A-HMS and M-HMS suggested that the addition of a mercapto functional group to HMS, increased its adsorption capacity, most likely through increased hydrogen bonding and hydrophobic interactions. The adsorption capacities of these adsorbents were dependent on the pH, being highest at pH 5 due to the optimal electrostatic interactions and hydrogen bonding at this pH. Thermodynamic analysis indicated that the adsorption process was endothermic for all adsorbents. The adsorption capacity of the adsorbent for each solute might be related to the molecular size of the adsorbate.

Mechanical properties of silane‐treated silica particle‐filled polyisoprene composites: Influence of the alkoxy group mixing ratio in silane coupling agent containing mercapto group

AbstractSpherical silica particles were treated with a mixture of silane coupling agents with mercapto functional groups and dialkoxy or trialkoxy groups. The surface coverage, which indicates the number of layers covering the silica surface, was in the range from 1.6 to 6.0. The molecular mobility of the treated layer was analyzed with 1H‐NMR spectroscopy. The silane chain became more flexible with increasing dialkoxy structures in the mixture and with increasing surface coverage. The stress–strain behavior was measured for a composite consisting of the treated silica and vulcanized polyisoprene rubber (PIR). There was no influence of the dialkoxy and trialkoxy mixing ratio for near monolayer coverage. In the case of the pure dialkoxy and low trialkoxy contents, a higher stress was observed at the same strain for surface coverages of 2.4–3.8. However, a longer length flexible silane chain, that is, with a surface coverage of 6.0, was disadvantageous for the reinforcement effect. The results of pulse NMR analysis of the unextracted PIR on the particle surface and swelling test indicate that the reinforcement effect was strongly affected both by entanglement and the crosslinking reaction between the silane chain and PIR at the interfacial region. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Silica aerogels modified with mercapto functional groups used for Cu(II) and Hg(II) removal from aqueous solutions

A new adsorbent, silica aerogel modified with mercapto (-HS) functional group, was synthesized by standard sol–gel synthesis. Excellent properties of aerogels, obtained with the sol–gel synthesis, were preserved with supercritical drying with CO2. The adsorbent was characterized by Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC) and thermal gravimetry (TG) measurements, nitrogen physisorption and scanning electron microscope (SEM). The ability of modified silica aerogel with mercapto group to remove Cu(II) and Hg(II) from aqueous solutions was assessed using batch adsorption technique under equilibrium conditions. Adsorbent exhibits very high adsorption potential for both heavy metal ions and more than 99.0% removal was achieved in the pH range 4–6. The equilibrium data were fitted well by the Freundlich and Langmuir isotherm model (R2>0.9).

Large pore diameter MCM-41 and its application for lead removal from aqueous media

A room temperature method to create large pore size and pore volume ordered mesoporous silica (MCM-41) is demonstrated. Template removal was achieved with a microwave digestion procedure using a solution of nitric acid and hydrogen peroxide. The silica product exhibited an ordered hexagonal mesostructure, large pore volume (up to 0.99 cm 3/g), and large pore size (up to 6.74 nm) indicating its potential as a high capacity adsorbent. Surface modification, to enhance the ability of the material to extract potentially toxic metals (PTMs) from water was performed using different amino- and mercapto-functional groups. This paper reports on the extraction of lead ions from aqueous solution to demonstrate the material's significant improvement in adsorption capacity (up to 1000 μmol g −1 for lead). Moreover, methods have been developed to regenerate the sorbent allowing 100% recovery of Pb and reuse of the sorbent material in subsequent extractions. The performance of the material was also demonstrated for environmental samples containing relatively high concentrations (ppmv) of mixed metal ions reducing them to lower values (<100 ppbv) indicating that the sorbent may have applicability for environmental remediation of polluted water.

Thioacetate- and mercapto-functionalized hydrogenated natural rubber

Due to the differences in unsaturation levels of constituent rubbers, thioacetate and mercapto functional groups were introduced into hydrogenated natural rubber (HNR) to increase the compatibility of natural rubber (NR)/HNR blends. The effect of thioacetic acid and initiator concentrations including reaction time on the thioacetate content in HNR was investigated. Methanolysis of thioacetate-modified HNR (HNRTA) yielded mercapto-modified HNR (HNRSH). The addition of HNRTA or HNRSH into NR/HNR blends (50/50 wt ratio) increased the tensile strength. The improved mechanical properties of the compatibilized blends were confirmed by scanning electron microscopy, indicating a co-continuous morphology. Furthermore, the susceptibility of the vulcanizates to changes in temperature and ozone were also reported.

Synthesis of tritium labelled thiorphan, an enkephalinase inhibitor

AbstractTritium labelling of the enkephalinase inhibitor, thiorphan, is complicated by the presence of mercapto functional group. Reactions often used in aromatic tritiation, such as halogination and catalytic halogen/tritium displacement, are adversely affected by the presence of the divalent sulfur moeity. By protecting the SH group with t‐butyl group, the tritiation reaction proceeded smoothly without catalyst poisoning. The mercapto functionality was re‐generated with great ease and efficiency using 2‐nitrobenzenesulfenyl chloride and dithiothreitol (DTT). [3H]‐Thiorphan, thus, obtained had a radiochemical purity of &gt;99% by AN‐HPLC and a specific activity of 18.42 Ci/mmol. [3H]‐Thiorphan showed good stability when stored at 4°C in an aqueous solution containing 10% methanol and 0.2% DTT in the dark. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Preconcentration of germanium on mercapto-modified silica gel

A simple method for the determination of ultra-trace amounts of germanium in natural waters has been developed. Germanium was preconcentrated using silica having mercapto functional groups, namely mercapto silica and determined by hydride generation flame atomic absorption spectrometry (HGAAS). Utilising mercapto silica, satisfactory recovery values (>95%) were obtained at natural pH, for germanate concentrations as low as 50 ng l −1. Considering the highest preconcentration factor (400-fold) obtained, the sensitivity and 3s-detection limit of mercapto silica-HGAAS system can be expressed as 3.65 ng l −1/0.0044 AU and 0.813 ng l −1, respectively. Interference effects of diverse ions were investigated for HGAAS and mercapto silica-HGAAS systems.

Chemical modification of enzymes III. Cross-linked α-chymotrypsin

The two-step intramolecular cross-linking method (Reiner et al., J. Mol. Catal., 1 (1975) 3 - 11) was applied to α-chymotrypsin and met (O) chymotrypsin. Reaction of the enzyme with N-acetylhomocystein thiolactone led to 9.6 – 10.2 mercapto functional groups which were cross-linked with bis-iodoacetamides of different length, dichloroacetone, and by oxidation. The cross-linked derivatives showed a small increase in K M, an increased stability against denaturation by guanidine hydrochloride and a considerably longer shelf life when stored in solution.

Plastisol Sealants for Automotive Applications

Plastisol sealants are widely used in the automotive industry both as structural adhesives and as water-proofing compounds. Over the years, a variety of materials have been used to promote adhesion in formulated plastisol sealants. This paper covers experimental work with a series of plastisol sealants using silane coupling agents as integral blend adhesion promoters. Silanes with cyclic epoxy, mer capto, amino, and diamino functional groups have been studied. The influence of silane structure on adhesion, viscosity, viscosity stabil ity, flow properties, and sag resistance has been examined. After detailed study of formulating variables, it has been found that silane coupling agents will contribute significantly to the improvement of a number of essential sealant characteristics.