Synthesis and characteristics of polydepsipeptide with pendant thiol groups

To obtain water-soluble oligodepsipeptide with pendant thiol groups, the alternating co-oligomer [oligo(Glc-alt-Cys)], consisting of glycolic acid (Glc) and L -cysteine (Cys) residues as α-hydroxy acid and α-amino acid residues, respectively, was prepared by means of ring-opening homo-oligomerization of cyclo[Glc-Cys(MBzl)] and subsequent deprotection of methoxybenzyl groups. Moreover, to modify the properties of poly(lactic acid) [poly(LA)] and to introduce pendant thiol groups to poly(LA), the terpolymer of LA, Glc, and Cys {poly[LA-(Glc-Cys)]} was synthesized through ring-opening and copolymerization of L -lactide with the protected cyclodepsipeptide, cyclo[Glc-Cys(MBzl)] and subsequent deprotection of methoxybenzyl groups. By changing the mol fraction of (Glc-Cys) unit, the solubility, thermal transition, degradation behavior of the modified poly(LA), and the water contact angle of its film could be varied. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1283–1290, 1998     

Analytical behaviour of hydrophilic glycolmethacrylate gels with bound thiol groups

Hydrophilic glycolmethacrylate gels with side chains containing thiol groups show high sorption selectivity for Hg, Sb, Bi, As, Ag, Cu and Pt, even in 1–3 M solutions of sulfuric or hydrochloric acid. The preparation of the sorbent Spheron Thiol and the distribution coefficients for 13 ions as a function of pH are described; within the optimal pH range the distribution coefficients exceed 10⁴. The sorption capacity of the resin reached ca. 0.5–1.0 mmol Hg g^-1 in 0.05 M HCl and equilibrium was achieved within 5 min, except for arsenic and platinum in insufficiently acidic solutions.     

Titration of thiol groups in non-aqueous solvents

Thiols are titrated in acetone or dimethylformamide with sodium methoxide, employing visual end-point detection with Thymol Blue, Victoria Blue, p-hydroxyazobenzene or Azo Violet. Aromatic thiols are titrated in the presence of aliphatic thiols in acetone, with Thymol Blue as indicator.     

Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups

A simple procedure for the preparation of amorphous silica containing thiol groups which quantitatively affords sulfonic acid groups has been developed, resulting in site densities and activity for the esterification of acetic acid with methanol greater than a commercial Nafion silica composite.     

An original synthesis of highly ordered organosilica with a high content of thiol groups

Well ordered bridged organosilica highly functionalised with disulfide groups were obtained by self-assembly of alpha,omega-bis(trimethoxysilyl)alkyldisulfide under hydrophilic conditions; the reduction of disulfide cores to SH groups gave rise to material having a high mercury ion adsorption capacity.     

Milligram amount determination of thiol groups with ferricyanide. Use of 2,6-dichlorophenolindophenol as titrant

Summary Thiols are reacted at pH 7 with an excess of ferricyanide. The excess of reagent is determined by adding a measured excess of ascorbic acid followed by back titration of ascorbic acid with 2,6-dichlorophenolindophenol. A correction can be made for ascorbic acid, if present with thiols. Tested with dilute solutions of cysteine, glutathione, mercaptoacetic acid and some other water-soluble thiols gave results which are accurate to 0.1%. Glycine, cystine, methionine, etc. do not interfere.

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Zusammenfassung Thiole reagieren bei pH 7 mit überschüssigem Cyanoferrat (III). Der Überschuß läßt sich durch Zusatz einer gemessenen Menge Ascorbinsäure und deren Rücktitration mit 2,6-Dichlorphenolindophenol bestimmen. Ist neben Thiol bereits Ascorbinsäure zugegen, so ist eine entsprechende Korrektur anzubringen. Die Anwendung auf Lösungen von Cystein, Glutathion, Mercaptoessigsäure und einigen anderen wasserlöslichen Thiolen erbrachte auf 0,1% genaue Ergebnisse. Glycin, Cystin, Methionin usw. stören nicht.

     

The determination of thiol groups in polysulfide prepolymers by infrared spectrometry

Methods for the determination of thiol groups (0.5–6% w/w) in polysulfide prepolymers and formulated polysulfide sealants by computer-assisted infrared spectrometry are discussed. The weak SH absorption near 2460 cm^?1 is inhanced by digital manipulation, and a combination band near 2650 cm^?1 can be used as an internal standard over the range 0–% thiol. Direct analysis of condensed-phase samples gives satisfactory results for pure prepolymers, but for formulated sealant prepolymers there is interference from fillers. Such formulations are first dissolved in chloroform and centrifuged to remove slids. The results are slightly affected by the prepolymer resin concentration, and the alcohol stabiliser in the chloroform may alter the internal standard band by shifting the baseline. Both these factors must therefore be controlled. The solution method is suitable for the analysis of aged uncured sealant prepolymers as well as fresh material. Computer control of the spectrophotometer provides results in about 3 min, exclusive of sample preparation time.     

Halometallates of 1-methyl-4,4-dimercapto-piperidinium. Evidence of strong hydrogen bonds with participating thiol groups

Chlorometallates of transition and B subgroup elements are readily prepared and precipitated by reaction of the corresponding metallic salts with 1-methyl-4,4-dimercaptopiperidinium chloride. These chlorometallates investigated were [ZnCl₄]^2?, [CdCl₃]^?, [CoCl₄]^2?, [CuCl₅]^3? and [FeCl₄]^2?. Strong SH … Cl interactions, but not NH … Cl, have been evidenced by IR spectroscopy in the zinc, cadmium and cobalt complexes. The SH and NH absorptions are observed at ? 2480 cm^?1 and 3060 cm^?1, respectively. Partial deuteration of the [ZnCl₄]^2? complex with d₁-methanol, shifted these IR signals to 1800 and 2260 cm^?1, clearly evidencing a X-hydrogen type of bond. The SH … Cl interaction is smaller in the [FeCl₄]^2? complex, and practically nonexistent in the [CuCl₅^3? complex.     

Practical thiol surrogates and protective groups for arylthiols for Suzuki-Miyaura conditions

We have developed practical thiol surrogates and arylthiol protective groups for the Suzuki-Miyaura reaction. 2-Ethylhexyl-3-mercaptopropionate and 4-(2'-mercaptoethyl)pyridine were shown to be not only good thiol surrogates but also good protective groups for thiol. We have demonstrated toleration of these protective groups under aqueous Suzuki-Miyaura conditions.     

Enhancement of chemical rules for predicting compound reactivity towards protein thiol groups

Non-specific chemical modification of protein thiol groups continues to be a significant source of false positive hits from high-throughput screening campaigns and can even plague certain protein targets and chemical series well into lead optimization. While experimental tools exist to assess the risk and promiscuity associated with the chemical reactivity of existing compounds, computational tools are desired that can reliably identify substructures that are associated with chemical reactivity to aid in triage of HTS hit lists, external compound purchases, and library design. Here we describe a Bayesian classification model derived from more than 8,800 compounds that have been experimentally assessed for their potential to covalently modify protein targets. The resulting model can be implemented in the large-scale assessment of compound libraries for purchase or design. In addition, the individual substructures identified as highly reactive in the model can be used as look-up tables to guide chemists during hit-to-lead and lead optimization campaigns.     

Use of p-diethylaminophenylmercuric acetate for the determination of thiol groups in biological samples

A simple titrimetric method for the determination of thiol and disulphide groups in biological samples with p-diethylaminophenylmercuric acetate as titrant, is suggested. Milligram amounts of cysteine (1-25 mg) are determined with a relative standard error not higher than 1%. The lowest detenninable amount of cysteine is 0.1 mg (relative standard deviation 3%). The accuracy and the sensitivity are the same as in amperometric titration with mercuric chloride. The method has been successfully used for the determination of thiol groups in various biological samples.     

Submicro methods for analysis of organic compounds : The determination of thiol groups

Several methods are described for the determination of thiol groups in organic samples weighing only 50 μg. Iodimetric methods were not widely applicable but the mercurimetric method of fritz and palmer in which thio-Michler's ketone serves as indicator was readily scaled down and gave excellent results (error ± 0.5% absolute) for all compounds tested. Diphenylcarbazone was also tried as the indicator; the procedure was satisfactory for most materials, but some anomalous results were obtained.     

Analytical utility of 2-halopyridinium salts—II Acidimetric determination of thiol groups

2-Chloro-1-methylpyridinium iodide reacts rapidly and quantitatively with thiol groups in the presence of excess of triethylamine to give the 2-alkyl(aryl)thio-1-methylpyridinium iodide and an equimolar amount of hydrogen chloride which is trapped by the triethylamine. The excess of triethylamine is back-titrated with hydrochloric acid, with Bromothymol Blue as indicator.     

Factors affecting the preparation and properties of electrodeposited silica thin films functionalized with amine or thiol groups

Well-adherent sol-gel-derived silica films functionalized with amine or thiol groups have been electrogenerated on gold electrodes and both the deposition process and the film properties have been studied by various physicochemical techniques. Electrodeposition was achieved by combining the formation of a self-assembled "nanoglue" on the electrode surface, the sol-gel process, and the electrochemical manipulation of pH to catalyze polycondensation of the precursors. Gold electrodes pretreated with mercaptopropyltrimethoxysilane (MPTMS) were immersed in sol solutions containing the selected precursors (tetraethoxysilane, TEOS, in mixture with (3-aminopropyl)triethoxysilane, APTES, or MPTMS) where they underwent a cathodic electrolysis to generate the hydroxyl ions that are necessary to catalyze the formation of the organosilica films on the electrode surface. Special attention was given to analyze the effects of deposition time and applied potential and to compare APTES and MPTMS films. Characterization was made using quartz crystal microbalance, scanning electron microscopy, cyclic voltammetry, and atomic force microscopy (including in situ monitoring). The electrodeposition process was found to occur at two growing rates: a first slow stage giving rise to rather homogeneous, yet rough, films with thickness in the sub-mum range (increasing continuously when increasing the deposition time), which was followed by a faster gelification step resulting in much thicker (>1 microm) and rougher macroporous deposits. These two successive situations were observed independently on the applied potential except that more cathodic values led to narrower sub-microm ranges (as expected from the larger amounts of the electrogenerated hydroxyl catalyst). Thiol-functionalized silica films were deposited more rapidly than the amine ones and, for both of them, permeability to redox probe was found to decrease when increasing the film thickness because of higher resistance to mass transport.     

A sensitive and practical colorimetric test for polymer-supported hydroxyl and thiol groups

A new sensitive and practical colorimetric test for solid-supported hydroxyl and thiol groups is described. The assay is based on the direct labeling with low amounts of commercially available NF31 in the presence of DMAP at room temperature, resulting in easily detectable red beads.     

Enhancement of lysosomal osmotic sensitivity induced by the photooxidation of membrane thiol groups

The osmotic lysis of photodamaged lysosomes is a critical event for killing tumor cells. How the photodamage increases lysosomal osmotic sensitivity is still unclear. In this work, the effect of the photooxidation of membrane thiol groups on the lysosomal osmotic sensitivity was studied by measuring the thiol groups with 5,5'-dithiobis(2-nitrobenzoic acid) and examining the lysosomal beta-hexosaminidase latency loss in a hypotonic sucrose medium. The results show that methylene blue-mediated photooxidation of lysosomes decreased their membrane thiol groups and produced cross-linkage of membrane proteins (molecular weight ranging from 75000 to 125000), which was visualized by sodium dodecyl sulfatepolyacrylamide gel electrophoresis. Simultaneously, the lysosomal osmotic sensitivity increased. These photoinduced alterations of the lysosomes could be recovered by reducing the oxidized thiol groups with dithiothreitol. It indicates that the photooxidation of membrane thiol groups can increase the lysosomal osmotic sensitivity and therefore provides a new explanation for the photoinduced lysosomal lysis.     

Synthesis of oligonucleotides carrying thiol groups using a simple reagent derived from threoninol

Oligonucleotides carrying thiol groups are useful intermediates for a remarkable number of applications involving nucleic acids. In this study, DNA oligonucleotides carrying tert-butylsulfanyl (t-BuS) protected thiol groups have been prepared. A building block derived from threoninol has been developed to introduce a thiol group at any predetemined position of an oligonucleotide. The resulting thiolated oligonucleotides have been used for the preparation of oligonucleotide conjugates and for the functionalization of gold nanoparticles using the reactivity of the thiol groups.     

Thiacalix[4] arenes with terminal thiol groups at the lower rim: synthesis and structure

Methods were developed for the synthesis of ω-mercaptoalkoxy derivatives of thiacalix[4]-arenes in the 1,3-alternate conformation containing different numbers (2–5) of methylene spacers at the lower rim. The hydrazinolysis of the corresponding thioacetates is the most efficient method for the synthesis of these compounds.