Pseudomonas aeruginosa cytochrome c denaturation by five systematic urea derivatives that differ in the alkyl chain length.

Reversible denaturation of Pseudomonas aeruginosa cytochrome c (PAc) could be followed using five systematic urea derivatives that differ in the alkyl chain length, i.e. urea, N-methylurea (MU), N-ethylurea (EU), N-propylurea (PU), and N-butylurea (BU). The BU concentration was the lowest required for the PAc denaturation, those of PU, EU, MU, and urea being gradually higher. Furthermore, the accessible surface area difference upon PAc denaturation caused by BU was found to be the highest, those by PU, EU, MU, and urea being gradually lower. These findings indicate that urea derivatives with longer alkyl chains are stronger denaturants. In this study, as many as five systematic urea derivatives could be applied for the reversible denaturation of a single protein, PAc, for the first time, and the effects of the alkyl chain length on protein denaturation were systematically verified by means of thermodynamic parameters.