Collection: SPDP PEG

SPDP PEG is a PEG reagent featuring a pyridyldithiol group at the end of the PEG chain. This particular group is capable of forming disulfide bonds with reduced cysteines and other sulfhydryl groups, resulting in a stable yet reversible linkage. Beyond proteins, SPDP PEG can be applied to modify or crosslink molecules possessing sulfhydryl groups. The inclusion of the PEG chain serves to enhance the solubility of the reagent and its conjugates when compared to hydrocarbon spacers.

Optimal conditions for the reaction between the pyridyldithiol group and sulfhydryl groups are achieved at pH 7-8 in a thiol-free buffer, with the subsequent release of pyridine-2-thione, quantifiable by its absorbance at 343 nm. The resultant disulfide-containing conjugates can be effectively reduced and cleaved by agents such as dithiothreitol (DTT), THPP, or TCEP. In most instances, a 25mM DTT solution at pH 4.5 proves sufficient to break the crosslinks without impacting the natural protein disulfides.