Open AccessCounting the number of disulfides and thiol groups in proteins and a novel approach for determining the local pK a for cysteine groups in proteins in vivo
Author(s) -
Bellacchio Emanuele,
McFarlane Karen L.,
Rompel Annette,
Robblee John H.,
Cinco Roehl M.,
Yachandra Vittal K.
Publication year - 2001
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049500017210
Subject(s) - x ray absorption spectroscopy , chemistry , sulfur , cysteine , thiol , glutathione , tripeptide , redox , molecule , oxidation state , absorption spectroscopy , combinatorial chemistry , inorganic chemistry , organic chemistry , amino acid , biochemistry , enzyme , physics , quantum mechanics , catalysis
X‐ray Absorption Spectroscopy (XAS) is a powerful tool to investigate sulfur in biological molecules. The spectral features are sensitive to the local electronic and geometric environment of the atom; thus, they constitute a fingerprint of the different chemical forms in which the sulfur is present. This allows straightforward detection of the ratio between free thiols and disulfides. Intra‐ or inter‐molecular disulfide bond formation between residues plays an important role in structural and conformational changes in proteins, and such changes can be investigated using sulfur XAS. Also, a thiolate‐disulfide equilibrium is involved in the regulation of the redox potential in the cells by means of modulating the concentrations of the reduced (thiolate) and oxidized (disulfide) form of the tripeptide glutathione. Thus, we can monitor the redox state of a cell by means of sulfur XAS. Thiols also exhibit an acid‐base equilibrium, and sulfur XAS can be used to determine the local pK a of the ‐SH group. Here we report examples of how sulfur XAS has been used for these applications.