On the Structural Stability and Solvent Denaturation of Proteins

Abstract The denaturation of sperm whale myoglobin, horse heart cytochrome c, and bovine α-chymotrypsinogen by various water-miscible amides has been investigated by spectral, difference spectral, and optical rotatory dispersion methods. As in the case of denaturants of the type of alcohols, glycols, and ureas, the effectiveness of the amides was found to increase with increasing hydrocarbon content and alkyl substitution of their functional amino groups. Branching of the hydrocarbon portion of the substituent groups of the latter compounds decreased their effectiveness as protein denaturants. Analysis of the denaturation data based on the theories of Peller and Flory, with appropriate binding constants and Setschenow parameters calculated from the solubilities of N-acetyl-l-tryptophan ethyl ester, has shown that hydrophobic interactions play an increasingly important role with increasing hydrocarbon content in the mode of action of the amides as denaturants.