Helix–coil transition of poly‐N⁵‐(3‐hydroxypropyl)‐L‐glutamine: Thermodynamic and statistical analysis

The thermally induced conformational changes of poly‐ N 5 ‐(3‐hydroxypropyl)‐ L ‐glutamine in water and in methanol–water (3:7 v/v) have been analyzed in terms of the Lifson‐Roig theory. The transitions in both solvents can be described by using v = 0.017. The thermodynamic parameters for the random coil‐to‐helix transition of one amino acid residue at room temperature were found to be: in water, Δ H = − 130 cal/mole and Δ S = − 0.45 e.u.; in methanol–water (3:7 v/v), Δ H = − 170 cal mole and Δ S = − 0.45 e.u. The size distribution of helical segments is broad, and the results of numerical calculations are presented for three degrees of polymerization (DP = 100, 300, and 750).