Counter-ion-specific helix formation of poly(gamma-methyl L-glutamate) derivatives containing sulfonate group in aqueous alcohols

Charged polypeptides containing sulfonate groups were prepared by transeste rification of poly(gamma -methyl L-glutamate) with isethionic acid. The coi l-helix transition of the sulfonated polypeptides was investigated in aqueo us alcohols. Marked counter-ion specificity was observed for helix formatio n: Li+ < Na+ < Cs+ <less than or equal to> Rb+ less than or equal to K+; th is was different to that for poly(L-glutamate) (PLG): Cs+ < K+ < Li+ < Na+. Specific helix stabilization by counter-ion mixing, which has been found f or the PLG system, was not observed for the sulfonated polypeptides. The co unter-ion- and solvent-specific helix formation is discussed and compared w ith that in PLG. <(c)> 2001 Society of Chemical Industry.