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The unfolding enthalpy of the pH 4 molten globule of apomyoglobin measured by isothermal titration calorimetry
Author(s) -
Jamin Marc,
Loh Stewart N.,
Baldwin Robert L.,
Antalik Marian,
Bolen D. Wayne,
Loh Stewart N.
Publication year - 2000
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.9.7.1340
Subject(s) - isothermal titration calorimetry , enthalpy , chemistry , molten globule , calorimetry , titration , crystallography , isothermal process , thermodynamics , circular dichroism , physics
The unfolding enthalpy of the pH 4 molten globule from sperm whale apomyoglobin has been measured by isothermal titration calorimetry, using titration to acid pH. The unfolding enthalpy is close to zero at 20 °C, in contrast both to the positive values expected for peptide helices and the negative values reported for holomyoglobin and native apomyoglobin. At 20 °C, the hydrophobic interaction should make only a small contribution to the unfolding enthalpy according to the liquid hydrocarbon model. Our result indicates that some factor present in the unfolding enthalpies of native proteins makes the unfolding enthalpy of the pH 4 molten globule less positive than expected from data for peptide helices.