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Statistics of branching and hairpin helices for the dAT copolymer
Author(s) -
de Gennes P.G.
Publication year - 1968
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1968.360060508
Subject(s) - radius of gyration , chemistry , branching (polymer chemistry) , gyration , propagator , copolymer , thermodynamics , melting point , helix (gastropod) , polymer , intrinsic viscosity , crystallography , physics , mathematical physics , geometry , organic chemistry , biology , ecology , mathematics , snail
Abstract At low temperatures a single strand of dAT copolymer tends to form a double helix with a loop at one end (hairpin). At slightly higher temperatures a branched structure (consisting of many hairpins connected by coiled regions) appears. The equilibrium properties of this branched structure are studied here by a propagator method. In particular the radius of gyration R G is calculated; under typical conditions, R G is expected to show a minimum at a temperature slightly below melting, in agreement with viscosity measurements. The present calculation is restricted to rather sharp transitions, for which the size of each helical region is large, even at the melting point. Then, in a rather broad range of molecular weights, M , R G is proportional to M 1/4 (as in the Zimm‐Stockmayer theory of simple branched polymers).