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The thermal induced helix—β transition of poly( N ε ‐methyl‐ L ‐lysine) and poly( N δ ‐ethyl‐ L ‐ornithine) in aqueous solution
Author(s) -
Yamamoto Hiroyuki,
Yang Jen Tsi
Publication year - 1974
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.1974.360130604
Subject(s) - chemistry , intramolecular force , aqueous solution , lysine , helix (gastropod) , intermolecular force , stereochemistry , ornithine , polymer chemistry , crystallography , medicinal chemistry , amino acid , organic chemistry , molecule , biochemistry , arginine , snail , biology , ecology
Abstract Uncharged poly( N ε ‐methyl‐ L ‐lysine) (PMLL) and its isomer, poly( N δ ‐ethyl‐ L ‐ornithine) (PELO), in alkaline solution (pH ca. 12) undergo a helix‐to‐β transition upon mild heating at 50°C or higher in a manner similar to that of poly( L ‐lysine) (PLL). The rate of conversion follows the order: PMLL < PELO < PLL. The helix can be regenerated upon cooling near zero degrees, for instance, after more than 12 hr at 2°C. At concentrations less than 0.02% the β form is intramolecular, but at higher concentrations both intra‐ and intermolecular β forms are generated. Poly( N δ ‐methyl‐ L ‐ornithine) (PMLO), an isomer of PLL, behaves like poly( L ‐ornithine); uncharged PMLO in alkaline solution is partially helical and becomes disordered at elevated temperatures.