13244-81-0Relevant academic research and scientific papers
A kinetic approach to characterize the electrostatic environments of thiol groups in proteins
Zhang, Hao,Le, Min,Means, Gary E.
, p. 356 - 364 (1998)
In this study, we synthesized a zwitterionic DTNB derivative, 5-(2- aminoethyl)-dithio-2-nitrobenzoate (ADNB), and characterized its reactions with several cationic, anionic, and neutral thiols. Reactions with ADNB, unlike those with DTNB, are relatively insensitive to electrostatic environments and ionic strengths. At relatively low ionic strength, rate ratios, k(ADNB)/k(DTNB), varied from 0.22 for reactions with low-molecular- weight cationic thiols to 3.0 for those with low-molecular-weight anionic thiols. A k(ADNB)/k(DTNB) ratio of ~200 for Cys-34 of BSA appears to reflect a very anionic environment. k(ADNB)/k(DTNB) ratios of ~6 and ~1, respectively, for canine and equine serum albumins, which have Glu-82 → Asp and Glu-82 → Ala substitutions suggest Glu-82 is the most important anionic residues affecting the reactivity of Cys-34 in BSA. k(ADNB)/k(DTNB) ratios appear to be useful for characterizing electrostatic environments of thiol groups in proteins.
Kinetics and Equilibria of Thiol/Disulfide Interchange Reactions of Selected Biological Thiols and Related Molecules with Oxidized Glutathione
Keire, David A.,Strauss, Erin,Guo, Wei,Noszal, Bela,Rabenstein, Dallas L.
, p. 123 - 127 (2007/10/02)
Rate constants for reaction of coenzyme A and cysteine with oxidized glutathione (GSSG) and equilibrium constants for the reaction of coenzyme A, cysteine, homocysteine, cysteamine, and related thiols with GSSG by thiol/disulfide interchange were determined over a range of pD values by NMR spectroscopy.The rate constants for reaction of the thiolate anion forms of coenzyme A and cysteine with GSSG suggest that reduction of GSSG by coenzyme A and cysteine is a mechanistically uncomplicated SN2 reaction.Equilibrium constants for the thiol/disulfide interchange reactions show a strong dependence on the Bronsted basicity of the thiolate anion.In a similar way, ΔE0', the difference between the half-cell potentials for the RSSR/RSH and GSSG/GSH redox couples, is linearly dependent on the difference between the pKA values of RSH and glutathione: ΔE0' = 64ΔpKA - 7.7 where ΔE0' is in units of mV.The reducing strength at a given pH is also determined by the fraction of the thiol present in the reactive thiolate form.At pD 7, the half-cell potentials for coenzyme A, cysteine, homocysteine, and cysteamine are close to that of glutathione, the major intracellular thiol redox system, which suggests that small changes in the intracellular redox potential can cause significant changes in the intracellular distribution of these biological thiols between their reduced and oxidized forms.
