Pyridyldithio groups in analytical and applied biochemistry

The applications of PDP-group containing compounds in bioscience are expanding. These applications arise from the fact that: (a) The disulfide group readily undergoes thiol-disulfide exchange reactions with other sulfhydryl-group containing compounds. (b) The COOH can be activated to another reactive end group. In this study, therefore, the synthesis of PDP-group containing crosslinkers was undertaken. The crosslinkers which were successfully synthesized include: 2SPDP (for cost reasons), 4SPDP (for the first time and because of the higher intrinsic reactivity of the 4PDP group), benzophenone derivative containing a pyridyldithio group (a trifunctional crosslinker), and an intermediate crosslinker NH2-PEG-COOH (for crosslinking to other short crosslinkers). Secondly, DTDP was successfully used in the spectrophotometric measurement of mercaptans in organic solvent. This was possible because of the fact that: (a) DTDP has higher absorbance increase at a given thiol concentration than Ellman's reagent which is a popular spectrophotometric thiol determination reagent. (b) The intrinsic reactivity of thiolate anions is much higher for DTDP than Ellman's reagent. Using triethylamine as a base catalyst in this SN2 reaction, different types of mercaptans were successfully measured spectrophotometrically. This showed that spectrophotometric response depends solely on SH group concentration and not on the rest of the mercaptan molecule, as is required for a reliable spectrophotometric assay. (author)