Pyridine-2-thione absorptivity

A soln of 1.5 mM DTDP in 0.5 M Nad/0.05M pH 7.5 phosphate buffer, containing 6M Gdn-HCl (to enhance exposure and reactivity of SH groups) and 1 mM EDTA (to bind metal ions and thereby prevent air oxidation of SH groups during the assay) was prepared. A sample of the protein soln (100 pi) was added to 0.05 M pH 7.5 phosphate buffer (0.8 mL) with the DTDP soln prepared above (0.1 mL). The reagent blank consisted of 0.05 M pH 7.5 phosphate buffer (0.8 mL), the DTDP soln prepared above (0.1 mL), and the buffer used to dissolve the protein (0.1 mL). From the amount of pyridine-2-thione (molar absorptivity 8.08 x 103 at 343 nm) released, the SH groups can be quantitated.1951... 

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