Resynthesis of insulin from its A and B chains in the presence of denaturants.

Reoxidation of the reduced insulin A and B chains in 8 M urea leads to a recovery of native insulin of 2-7% whereas in 6 M guanidine or 0.5 mM dodecylsulfate very little, if any, resynthesis of insulin could be detected. Considering all the possibilities of different oligomeric forms containing one or both of the chains, the yield in 8 M urea is well over the yield as calculated from random joining of the chains and the yield in guanidine or dodecylsulfate is to be expected. It is concluded that some interaction and pairing of the chains occur even in the presence of 8 M urea.