Heat-induced Conformational Changes in Proteins Studied by Electrospray Ionization Mass Spectrometry

A simple and effective device for investigating heat-induced denaturation of proteins by electrospray ionization mass spectrometry is described. Results are presented for the denaturation as a function of temperature and solution pH of bovine ubiquitin and bovine cytochrome c. These results are in concert with and extend the earlier results of LeBlanc et al. (Org. Mass Spectrom. 1991, 26, 831). The cooperative effects of pH and temperature on the denaturation of ubiquitin and cytochrome c were investigated. Electrospray ionization mass spectrometry is also shown to be a useful probe of the reversibility of heat-induced denaturation of proteins. Finally, it is demonstrated that heat-induced denaturation can be used to improve the mass spectrometric response of proteins that do not normally yield useful spectra when the solubilized protein is electrosprayed at ambient temperatures.