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Solution properties of synthetic polypeptides. XII. Enthalpy changes accompanying helix‐coil transition of polypeptide
Author(s) -
Teramoto Akio,
Norisuye Takashi
Publication year - 1972
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.1972.360110814
Subject(s) - chemistry , enthalpy , solvent , helix (gastropod) , thermodynamics , calorimetry , dilution , yield (engineering) , electromagnetic coil , transition temperature , crystallography , organic chemistry , physics , ecology , superconductivity , quantum mechanics , biology , snail
For helix‐coil transitions of polypeptide in binary mixtures consisting of helix‐forming solvent and coil solvent, the transition enthalpy Δ H ( T , x ) has been found to depend significantly on temperature ( T ) and solvent composition ( x ). For such systems, calorimetric measurements may yield some averages of Δ H ( T , x ) which are no longer amenable to direct comparison with Δ H itself. Theoretical equations relating calorimetric data to Δ H ( T , x ) are derived and tested favorably with experimental data. It is demonstrated that the transition enthaply from heat capacity measurements is approximately equal to Δ H cfm , while those from heat of dilution and heat of solution measurements are equal to Δ H c . Here Δ H c denotes the value of Δ H at the transition point and f m represents the maximum helical content attained in a thermally induced transition. The discrepancies among calorimetric data are also discussed.