Promotion of cyclization of linear pentapeptides and heptapeptide by different univalent metal ions

Abstract

Univalent metal ions such as Na⁺, K⁺ and Cs⁺ can enhance not only the cyclization yields of some linear pentapeptides and heptapeptide but also their cyclization rates while some bivalent and trivalent metal ions such as Mg²⁺, Ca²⁺, Zn²⁺, Fe²⁺, Ni²⁺ and Cr³⁺ elevate neither the cyclization yields nor the cyclization rates and some of them prevent the cyclization.