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The comprehensive acid–base characterization of glutathione

“…log k N NGG = log K GSSG dimethyl ester 1 + log 2 (13) log k N GG EE = log K GSSG tetramethyl ester 1 − log 2 (14) log k N NGG EE = log K GSSG tetramethyl ester 1 + log 2 (15) Equations with the form of (12)-(15) can be derived for symmetric dibasic molecules [6]. While this is certainly true for GSSG tetramethyl ester (Eqs.…”

“…Therefore, macroscopic physico-chemical parameters will not characterize the thiolate moiety specifically. For an exact/detailed elaboration, the site-specific, so-called microscopic parameters, are needed [6,7].…”

Glutathione and N-acetylcysteinylglycine: Protonation and Zn2+ complexation

“…The first two processes dominate at low pH values, while the latter two are mainly involved at pH > 6, with H 2 G À as the major species in a quite wide pH range. Thus, these dissociation processes can be split into two couple of processes of AB symmetry [37,38], one involving carboxylates and one involving thiol and amino groups, as reported in Scheme 3. It can be shown that for the first couple of microequilibria involving carboxylic functions on the glutamyl-(Glu) and glycine-(Gly) residues, the molar fraction of the species protonated on the glycine residue and dissociated on the glutamyl-carboxylate [H 3 G Glu ] is given by (Eq.…”

Protolytic properties of polyamine wasp toxin analogues studied by 13C NMR spectroscopy

“…21,23,24 In smaller systems in symmetrical cases, or in cases where the sites can be subdivided into noninteracting subsets, NMR titration curves can be used to derive ratios of microspecies contributing to the macrospecies, as well as all microequilibrium constants. 21,29 The four-site acid-base systems without symmetry such as 1-8 contain 16 microspecies and 32 unknown microscopic pK a values. Even assuming that eight of the microconstants that involve deprotonation of the phenol group are identical and equal to the pK a value derived from the titration curves of the carbon atoms of the aromatic ring (Fig.…”