Isothermal Denaturation of Cytochrome-C by Urea at Different Ph Values

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Horse heart cytochrome c(cty-c) denaturation with urea at different pH values and 25 °C was observed spectrophotometrically in the visible range. The result shows that the decrease in pH favours urea denaturation of cyt-c. The pl (isoelectric point) value of cyt-c is 10.6. The of positive charge increases as the pH is decreased from 6.0. Hence elctrostatic repulsion will destabilize the protein. As expected the Cm (concentration at the mid-point of transition) shifts towards lower urea concentration with the decrease in pH, showing that pH also contributes free energy to unfolding besides urea.

Cytochrome C; urea, pH; isothermal denaturation