Synthesis and Properties of Poly(s²C), a new Poly(C) Analog

Abstract

Polymerisation of 2‐thiocytidine‐5′‐diphosphate (s 2 CDP) by polynucleotide phosphorylase from Escherichia coli leads to the formation of poly(s 2 C) which has been characterized by ultracentrifugation, enzymatic hydrolysis and phosphorolysis. The ultraviolet absorption derivative, optical rotatory dispersion and circular dichroism spectra of 2‐thiocytidine and poly(s 2 C) have been measured. Evidence for n ‐π* transitions in the absorption spectra of these compounds is derived from derivatives of ultraviolet absorption and circular dichroism spectra. The absorption‐temperature profiles of poly(s 2 C) in the acid pH range prove the existence of double‐stranded structures which are much less stable than those of poly(C). From these observations it is concluded that hydrogen bonding predominantly controls the stability of the poly(C) helix under acidic conditions.