Hydrophobic interaction and folding propensity of chicken heart apocytochrome c

In contrast to horse heart apocytochrome c, the chicken one showed quite different folding propensity as titrated by NaCl at different pH. At pH 2.0, folding behaviour of both apocytochrome c are essentially similar; while at pH higher than 4.0, chicken heart apocytochrome c has much enhanced propensity to fold and aggregate, as was shown by circular dichroism spectra, intrinsic fluorescence and non-denatured polyacrylamide gel electrophoresis. Hydrophobic chromatography demonstrated much higher hydrophobicity of chicken heart apocytochrome c, thus strongly suggested that it is the hydrophobic interaction that stabilize the 'Molten Globule' like, partially-folded structure of chicken heart apocytochrome c at neutral pH.