Characterization Of Thiol Research Articles

Asymmetrical Flow Field-Flow Fractionation Methods for Quantitative Determination and Size Characterization of Thiols and for Mercury Size Speciation Analysis in Organic Matter-Rich Natural Waters.

Asymmetrical flow field-flow fractionation (AF4) efficiently separates various macromolecules and nano-components of natural waters according to their hydrodynamic sizes. The online coupling of AF4 with fluorescence (Fluo) and UV absorbance (UV) detectors (FluoD and UVD, respectively) and inductively coupled plasma–mass spectrometry (ICP-MS) provides multidimensional information. This makes it a powerful tool to characterize and quantify the size distributions of organic and inorganic nano-sized components and their interaction with trace metals. In this study, we developed a method combining thiol labeling by monobromo(trimethylammonio)bimane bromide (qBBr) with AF4–FluoD to determine the size distribution and the quantities of thiols in the macromolecular dissolved organic matter (DOM) present in highly colored DOM-rich water sampled from Shuya River and Lake Onego, Russia. We found that the qBBr-labeled components of DOM (qB-DOM) were of humic type, characterized by a low hydrodynamic size (d h < 2 nm), and have concentrations <0.3 μM. After enrichment with mercury, the complexes formed between the nano-sized components and Hg were analyzed using AF4–ICP-MS. The elution profile of Hg followed the distribution of the UV-absorbing components of DOM, characterized by slightly higher sizes than qB-DOM. Only a small proportion of Hg was associated with the larger-sized components containing Fe and Mn, probably inorganic oxides that were identified in most of the samples from river to lake. The size distribution of the Hg–DOM complexes was enlarged when the concentration of added Hg increased (from 10 to 100 nM). This was explained by the presence of small iron oxides, overlapping the size distribution of Hg–DOM, on which Hg bound to a small proportion. In addition, to provide information on the dispersion of macromolecular thiols in colored DOM-rich natural water, our study also illustrated the potential of AF4–FluoD–UVD–ICP-MS to trace or quantify dynamic changes while Hg binds to the natural nano-colloidal components of surface water.

Design and development of thiolated graphene oxide nanosheets for brain tumor targeting

The present investigation emphasizes on synthesis and characterization of thiol functionalized reduced graphene oxide (TrGO) as a novel platform for loading of anticancer drug methotrexate (TrGO-MTX), through amide bonding. Thiolation of graphene oxide (GO) was achieved by transesterification process. The introduction of sulfur containing chemical groups and the partial reduction of GO to TrGO were proven by analytical techniques. Thiol content was found to be 6.98 mM by Ellman’s method in a quantitative manner. Furthermore, antineoplastic action of TrGO-MTX against human glioblastoma astrocytom U-373 MG cell line was studied, wherein TrGO-MTX demonstrated significant inhibition rate as compared with pure MTX.

Preparation and characterization of thiol- and amino-functionalized polysilsesquioxane coated poly(p-phenylenetherephthal amide) fibers and their adsorption properties towards Hg(II)

Two types of fibrous adsorbents, thiol- and amino- functionalized polysilsesquioxane coated poly(p-phenylenetherephthal amide) (PPTA) fibers (PPTA-PAPSQ and PPTA-PMPSQ), were prepared via the in situ condensations with aminopropyltriethoxysilane (APTES) and mercaptopropyltriethoxysilane (MPTES) on the surface of PPTA fibers, respectively. Their structures were characterized by FTIR, FE-SEM, XPS, XRD, TG, Elemental analysis, and pore structure analysis. The effect of the ratio of reactants on the structures of these two modified fibers was investigated. The results of nitrogen adsorption-desorption isotherms revealed that the polysilsesquioxane coating on the surface of PPTA-PMPSQ samples exhibited open meso- or macroporous features, while those on the surface of PPTA-PAPSQ samples formed dense gel structures. Moreover, Hg (II) was chosen as a representative to evaluate the adsorption properties of PPTA-PAPSQ and PPTA-PMPSQ samples. The results showed that the adsorption processes of Hg(II) followed well pseudo-second-order model onto the two series adsorbents. The Langmuir was the better-fit model to predict the experimental data. The theoretical saturation adsorption capacities of polysilsesquioxanes coated on the PPTA-PAPSQ and PPTA-PMPSQ adsorbents can reach 3.52–10.64mmolg−1 and 7.43–10.22, mmolg−1, respectively. The result showed that PPTA-PAPSQ and PPTA-PMPSQ adsorbents can selectively adsorb Hg(II) from binary component metal ion systems.

Synthesis and Characterization of Thiol- and Carboxyl-Functionalized Mesoporous Silica Nanoparticles

The purpose of this article is to synthesize the thiol-and carboxyl-bifunctionalized mesoporous silica nanoparticles (CMS-SH-COOH). CMS-SH-COOH was successfully synthesized by co-condensation and post-grafting methods. Moreover, the particle size and structural properties of CMS-SH-COOH were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR). The obtained results indicated that the CMS-SH-COOH presented a uniform spherical shape with a wormhole arrangement of the mesopores and a relatively narrow paticle distribition. Therefore, the CMS-SH-COOH might be a great potential carrier for the drug delivery system in the future.

Characterization of Thiol Peroxidase‐Glutaredoxin Fusion from Anabaena sp. (PCC7120) Acting as a Hydrogen Peroxide Peroxidase

Recently, novel hybrid thiol peroxidase (TPx or Prx: Peroxiredoxin) fused with a glutaredoxin (Grx) (TPx-Grx fusion) was found from some pathogenic bacteria. The hybrid protein reduces peroxides with the use of GSH as the proton donor to the Grx domain. A sequence coding for a hybrid thiol peroxidase was isolated from Anabaena sp. (PCC7120) genome and subsequently inserted into an expression plasmid. The recombinant protein was produced in Escherichia coli cells and purified to homogeneity. It was shown that the protein is dimeric and possesses two conserved cysteines (Cys) in the TPx domain and two Cys (CxxC) in the Grx domain. The hybrid protein can reduce various hydroperoxides, but with a much better efficiency for hydrogen peroxide than t-butyl hydroperoxide, cumene hydroperoxide, and linoleic acid hydroperoxide (hydrogen peroxide > t-butyl hydroperoxide >> cumene hydroperoxide > linoleic acid hydroperoxide) in the presence of GSH as the unique exogenous proton donor. The protein expression level of the hybrid protein in the cyanobacteria upon oxidative stress was assayed using an immunoblot. The protein is very highly expressed in response to oxidative and heat-shock stresses. Based on this finding, we propose that Anabaena TPx-Grx fusion, which represents a GSH-supported hydrogen peroxide peroxidase, plays a vital role in the defense of cyanobacteria against oxidative damage.

Synthesis and Characterization of Thiol Containing Furoxan Derivatives as Coligands for the Preparation of Potential Bioreductive Radiopharmaceuticals

The synthesis and characterization of thiol-containing 1,2,5-oxadiazole N-oxide (TONO) derivatives and their use as monodentate coligands for the preparation of (99m)Tc complexes is presented. 3-Mercaptomethyl-4-phenyl-1,2,5-oxadiazol N(2)-oxide and 3-(4-mercaptophenylmethylidenhydrazinocarbonyloxymethyl)-4-phenyl-1,2,5-oxadiazol N(2)-oxide were successfully synthesized and combined with the tridentate ligand N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA) to prepare "3+1 mixed ligand" technetium complexes. The( 99m)Tc complexes were obtained in high yield and radiochemical purity using low concentration of ligand and coligand. An alternative procedure using a xantate and a disulphide precursor of 3-mercaptomethyl-4-phenyl-1,2,5-oxadiazol N(2)-oxide yielded the same complex. Biological evaluation of the potentiality of the( 99m)Tc complexes as bioreductive radiopharmaceuticals was performed in normal CD1 mice and in mice bearing induced sarcoma. Tumour uptake was moderate but tumour/soft tissue ratio was favourable. Although these results are encouraging, further development is still necessary in order to achieve higher tumour uptake and lower gastrointestinal activity.

Purification and characterization of thiols in an arsenic hyperaccumulator under arsenic exposure.

Pteris vittata (Chinese brake fern) is the first reported arsenic hyperaccumulator. To investigate the arsenic tolerance mechanism in this plant, reversed-phase HPLC with postcolumn derivatization was used to analyze the thiols induced under arsenic exposure. A major thiol in the plant leaflets was found to be responsive to arsenic exposure. The arsenic-induced compound was purified on a large scale by combining covalent chromatography and preparative reversed-phase HPLC. About 2 mg of this compound was isolated from 1 kg of fresh leaflets. The purified arsenic-induced compound was characterized using electrospray ionization mass spectrometry. A molecular ion (M + 1) of 540 and fragments were obtained, which indicated that the arsenic-induced thiol was a phytochelatin with two subunits (PC(2)). Compared to the classical methods for purification of phytochelatins, this new method is more specific, simple, and rapid and is suitable for purification of PCs in a large scale as well as sample preparation for mass spectrometry analysis.

Characterization of thiol-, aspartyl-, and thiol-metallo-peptidase activities in Madin-Darby canine kidney cells

We combined fluorogenic substrates or internally quenched fluorescent peptides with specific inhibitors in the pH profile of proteolytic activity experiments in order to detect proteolytic activities in lysates of MDCK cells. Hydrolytic activities related to cathepsin B, L, and D were observed. Serine-proteinase was not detected; however, we clearly demonstrated the presence of a thiol-metallo-endo-oligopeptidase, also called thimet-oligopeptidase (TOP). This peptidase from MDCK cells has substrate and inhibitor specificities as well as an activation profile with mercaptoethanol that are indistinguishable from the recombinant rat testis TOP (EC 3.4.24.15). In addition, polyclonal purified antibodies to this enzyme depleted the TOP activity of MDCK cells in whole homogenate. Although we present only preliminary data, TOP is secreted by MDCK cells. The presence of TOP in a phenotype polarized MDCK cells can have special significance in the cytoplasmic selection, transport, or clearance of short peptides due to restriction of the enzyme to sequences from 6 to 17 amino acids. Therefore, the MDCK cell could be a very useful cellular model with which to study some of the suggested TOP biological functions as processing of biological active peptides and antigen presentation. J. Cell. Biochem. 76:478–488, 2000. © 2000 Wiley-Liss, Inc.

Characterization of thiol-, aspartyl-, and thiol-metallo-peptidase activities in Madin-Darby canine kidney cells

We combined fluorogenic substrates or internally quenched fluorescent peptides with specific inhibitors in the pH profile of proteolytic activity experiments in order to detect proteolytic activities in lysates of MDCK cells. Hydrolytic activities related to cathepsin B, L, and D were observed. Serine-proteinase was not detected; however, we clearly demonstrated the presence of a thiol-metallo-endo-oligopeptidase, also called thimet-oligopeptidase (TOP). This peptidase from MDCK cells has substrate and inhibitor specificities as well as an activation profile with mercaptoethanol that are indistinguishable from the recombinant rat testis TOP (EC 3. 4.24.15). In addition, polyclonal purified antibodies to this enzyme depleted the TOP activity of MDCK cells in whole homogenate. Although we present only preliminary data, TOP is secreted by MDCK cells. The presence of TOP in a phenotype polarized MDCK cells can have special significance in the cytoplasmic selection, transport, or clearance of short peptides due to restriction of the enzyme to sequences from 6 to 17 amino acids. Therefore, the MDCK cell could be a very useful cellular model with which to study some of the suggested TOP biological functions as processing of biological active peptides and antigen presentation.

Paper electrophoretic characterization of thiols, sulphides and disulphides as sulphonium salts

Separation et identification des thiols, sulfures et disulfures organiques par electrophorese des derives obtenus par alkylation avec la fluorosulfonate de methyle («methyl magique»)