Synchrotron radiation circular dichroism spectroscopy: vacuum ultraviolet irradiation does not damage protein integrity.

Synchrotron radiation circular dichroism (SRCD) spectroscopy is an emerging technique for sensitive determination of protein secondary structures and for monitoring of conformational changes. An important issue for its adoption as a useful technique is whether the high-intensity low-wavelength vacuum ultraviolet radiation in the SRCD chemically damages proteins. In this paper, using horse myoglobin as a test sample, it is shown that extensive irradiation in the SRCD does not produce any change in the chemical nature of the protein as detected by either SDS gel electrophoresis or mass spectrometry. In addition, no changes in the protein secondary structure are detectable from the SRCD spectra after extensive exposure to the SRCD beam.