Solution properties of synthetic polypeptides. XII. Enthalpy changes accompanying helix-coil transition of polypeptide

✍ Scribed by Akio Teramoto; Takashi Norisuye

• Publisher: Wiley (John Wiley & Sons)
• Year: 1972
• Tongue: English
• Weight: 482 KB
• Volume: 11
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1972.360110814

✦ Synopsis

Abstract

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.