Microcalorimetric studies of the interactions between cytochromes and and of their interactions with phospholipids |
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Authors: | Chang-An Yu Joy R Steidl Linda Yu |
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Institution: | Department of Biochemistry, Oklahoma State University, Stillwater, OK 74078 U.S.A. |
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Abstract: | Thermotropic properties of purified cytochrome and cytochrome have been studied by differential scanning calorimetry under various conditions. Both cytochromes exhibit a single endothermodenaturation peak in the differential scanning calorimetric thermogram. Thermodenaturation temperatures are ionic strength, pH, and redox state dependent. The ferrocytochromes are more stable toward thermodenaturation than the ferricytochromes. The enthalpy changes of thermodenaturation of ferro- and ferricytochrome are markedly dependent on the ionic strength of the solution. The effect of the ionic strength of solution on the enthalpy change of thermodenaturation of cytochrome is rather insignificant. The formation of a complex between cytochromes and at lower ionic strength causes a significant destabilization of the former and a slight stabilization of the latter. The destabilization of cytochrome upon mixing with cytochrome was also observed at high ionic strength, under which conditions no stable complex was detected by physical separation. This suggests formation of a transient complex between these two cytochromes. When cytochrome was complexed with phospholipids, no change in the thermodenaturation temperature was observed, but a great increase in the enthalpy change of thermodenaturation resulted. |
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Keywords: | Thermodenaturation Differential scanning calorimetry Phospholipid |
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