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 | JOURNAL OF SYNCHROTRON RADIATION |
Counting the number of disulfides and thiol groups in proteins and a novel approach for determining the local pKa for cysteine groups in proteins in vivo
aMelvin Calvin Laboratory, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720-5230, USA, and bDepartment of Chemistry, University of California, Berkeley, CA 94720-5230, USA
*Correspondence e-mail: VKYachandra@lbl.gov
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 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 Also, a thiolate-disulfide equilibrium is involved in the regulation of the 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 also exhibit an acid-base equilibrium, and sulfur can be used to determine the local pKa of the -SH group. Here we report examples of how sulfur has been used for these applications.
