Notizen: Quantification and Localisation of SH-Groups in Human Blood Serum Proteins

The thiol groups of human blood serum proteins were determined after 24 hours interaction with dithionitrobenzoicacid (DTNB) to an average of 538 ± 60 µmol/l serum. After treatment of the serum with [35S]DTNB , autoradiograms of the protein elpherograms revealed two main peaks: The first with 63% of total activity, in the albumin region, corresponding to 0.60 SH/mol, the second with 23% of total activity, in the 7-globulin range, corresponding to 2.2 SH/mol. After 30 minutes incubation with D TNB , or with p-chloromercuribenzoate (CMB), in freshly prepared pools of IgG only 0.2 SH/mol were found which is the expected value already known from the literature.Autoradiograms taken from serum protein elpherograms after interaction with [UC] CMB only show the main SH-peak in the albumin range. Thus ist is concluded that the SH-peak in the γ-globulin region after 24 hours incubation with [35S]DTNB is due to one highly labile S-S-bond which easily undergoes a disulfide exchange with DTNB .