Copolymerization kinetics of N-carboxyanhydrides of some α-amino acids: Influence of nature of amino acids

Studies on copolymerization kinetics of N-carboxyanhydride (NCA) of O-acetyl-L -tyrosine (T) with NCAs of L -valine (V) and glycine (G) were carried out in dioxane at 25°C with n-butylamine as initiator. The reactivity ratios for the VT system were found to be r_V:r_T:0.57:0.22; and for the GT system, r_G:r_T:0.26:0.42. A comparison of this data with that obtained when L -analine was used in place of L -valine or glycine showed that in the three systems, the reactivity ratio of the amino acid residue with a greater tendency to form ordered secondary structure was greater than that of its comonomer. Among the variable comonomers (glycine, L -alanine, L -valine) of O-acetyl-L -tyrosine, it is again L -alanine, whose tendency to form helical structure is very high, that has the greater reactivity ratio.