Reduction of S-sulpho groups by tributylphosphine: an improved method for the recombination of insulin chains.

All 4 S-sulpho groups of the S-sulpho substituted insulin A-chain could be removed with 4 mol of tributylphosphine. Reduction of a 1:1 mixture of both S-sulpho insulin chains with tributylphosphine followed by air oxidation gave insulin which was isolated in pure form and high yield. Removal of excess reducing agent was not necessary, in contrast to the usual procedures employing thiols for the reduction step. This constitutes a rapid and simple method for the generation of insulin from its chains. A new method for the purification of S-sulpho-A-chain has been developed.