The unfolding enthalpy of the pH 4 molten globule of apomyoglobin measured by isothermal titration calorimetry.
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 degrees C, in contrast both to the positive values expected for peptide helices and the negative values reported for holomyoglobin and native apomyoglobin. At 20 degrees 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.
Department of Biochemistry, Beckman Center, Stanford University School of Medicine, California 94305-5307, USA.
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Jamin
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Antalik
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Loh
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Bolen
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Baldwin
D001059:Apoproteins / Q000737:chemistry*; D002151:Calorimetry / Q000379:methods*; D002942:Circular Dichroism; D005453:Fluorescence; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009211:Myoglobin / Q000737:chemistry*; D011199:Potentiometry / Q000379:methods; D017510:Protein Folding; D017186:Titrimetry
D001059:Apoproteins; D009211:Myoglobin; C010857:apomyoglobin