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Temperature‐dependent optical rotatory dispersion properties of helical muscle proteins and homopolymers
Author(s) -
Hvidt Søren,
Rodgers Michael E.,
Harrington William F.
Publication year - 1985
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.360240902
Subject(s) - optical rotatory dispersion , chemistry , random coil , helicity , optical rotation , temperature jump , crystallography , helix (gastropod) , myoglobin , myosin , nuclear magnetic resonance , circular dichroism , organic chemistry , physics , biochemistry , ecology , particle physics , snail , biology
Abstract Thermally induced helix–coil transitions of myosin rod, light meromyosin, and tropomyosin were studied by optical rotatory dispersion (ORD). Fractional helicity was calculated from both the Moffitt‐Yang parameter, b 0 , and the corrected mean residue rotation [ m ′] at 231.4 nm. Between 3 and 30°C, [ m ′] increases linearly with a slope of 59/°C, whereas b 0 is virtually constant, indicating apparently different thermal melting behavior. Poly( L ‐lysine) and poly( L ‐glutamic acid) in their helical forms and myoglobin also show a nearly linear temperature dependence of [ m ′] 231.4 . Muscle proteins in 6 M guanidine hydrochloride and the random‐coil forms of the homopolymers exhibit temperature‐dependent values of [ m ′] 231.4 and b 0 . We conclude from these observations that ORD properties of both α‐helices and random‐coil polypeptides have significant intrinsic temperature dependencies. A new method of estimating fractional helicity as a function of temperature is proposed.