Selects and organizes material to accommodate readers of different educational and professional backgrounds, giving a concise and pragmatic review. Accounts of experimental methods are self-contained, with special emphasis given to the macromolecular properties on unfolded (denatured) proteins. Includes little unpublished material; however, submits several physicochemical aspects of protein denaturation to a critical analysis, especially the thermodynamic analysis. Indicates still unsolved problems to promote investigations into their solutions.