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Research has been conducted on the soluble and functional fragment of the membrane-bound cytochrome c (sub)522 from Paracoccus denitrificans. The expressing and (super)13 C/ (super)15 N-labeling of this cytochrome has been carried out and the structure of this protein has been investigated and described.

The domains of a DNA-binding protein from phage lambda, the Cro repressor were determined using calorimetric studies. A mutant Cro repressor was created by substituting cysteine for valine at position 55. Results showed that disulfide bonds occurring at this point conferred structural stability which behaved as a single cooperativee domain upon denaturation. Bonds at the C-terminal domain exhibited stability although the N-terminal produced a cooperative block in a disulfide bond linked dimer. This was shown to melt at a higher teemprature than proteins devoid of cross links.

The mechanisms underlying the thermal unfolding of the wild-type Cro repressor and its disulfide-bridged mutant Cro-V55C, along with a CNBr-fragment of Cro-V55C, were investigated using dynamic light scattering and Fourier transform infrared spectroscopy. It was found that thermal denaturation of Cro-WT and Cro-V55C occurs in two steps through equilibrium unfolding intermediates. The unfolding became more complex at higher protein concentrations and involved the formation of tetramers at intermediate temperature ranges.