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The S−H bond in thiols is weak compared to the O−H bond in alcohols. For CH 3 X−H, the bond enthalpies are 365.07 ± 2.1 kcal/mol for X = S and 440.2 ± 3.0 kcal/mol for X = O. [ 21 ] Hydrogen-atom abstraction from a thiol gives a thiyl radical with the formula RS • , where R = alkyl or aryl.
Thiol–disulfide exchange is the principal reaction by which disulfide bonds are formed and rearranged in a protein. The rearrangement of disulfide bonds within a protein generally occurs via intra-protein thiol–disulfide exchange reactions; a thiolate group of a cysteine residue attacks one of the protein's own disulfide bonds.
Typically, the hydroxyl group of a serine (rarely, threonine) or the thiol group of a cysteine residue will attack the carbonyl carbon of the preceding peptide bond, forming a tetrahedrally bonded intermediate [classified as a hydroxyoxazolidine (Ser/Thr) or hydroxythiazolidine (Cys) intermediate].
The thiol-ene functionalization of surface has been widely investigated in material science and biotechnology. The attachment of a molecule with a sterically accessible alkene or thiol group to a solid surface enables the construction of polymers on the surface through subsequent thiol-ene reactions. [2]
Thioesters can be prepared by condensation of thiols and carboxylic acids in the presence of dehydrating agents: [2] [3] RSH + R'CO 2 H → RSC(O)R' + H 2 O. A typical dehydration agent is DCC. [4] Efforts to improve the sustainability of thioester synthesis have also been reported utilising safer coupling reagent T3P and greener solvent ...
Alternatively, sulfides can be synthesized by the addition of a thiol to an alkene in the thiol-ene reaction: R-CH=CH 2 + H-SR' → R-CH 2-CH 2-S-R' This reaction is often catalysed by free radicals produced from a photoinitiator. [6] Sulfides can also be prepared by many other methods, such as the Pummerer rearrangement. Trialkysulfonium salts ...
Conversion of simple disulfides to thiosulfinates results in a considerable weakening of the S–S bond from about 47.8 to 28.0 kcal mol −1 for the S-S bond in PhS(O)SPh and from about 63.2 to 39.3 kcal mol −1 for the S-S bond in MeS(O)SMe, [14] with the consequence that most thiosulfinates are both unstable and quite reactive.
Bifurcated H-bond systems are common in alpha-helical transmembrane proteins between the backbone amide C=O of residue i as the H-bond acceptor and two H-bond donors from residue i + 4: the backbone amide N−H and a side-chain hydroxyl or thiol H +. The energy preference of the bifurcated H-bond hydroxyl or thiol system is -3.4 kcal/mol or -2. ...