Photoabsorption and Photoelectron Spectra of Enzymes in the Vacuum-uv Region

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Abstract
The photoabsorption spectra and photoelectron yield spectra for the enzymes trypsin, RNase and lysozyme were measured in the vacuum-UV region between 1050 and 2400 .ANG.. The energy distribution curves of photoelectrons were also measured. The samples were in the form of thin films on substrates (lithium fluoride plates for photoabsorption measurements and cover glasses coated with gold for photoelectron measurements). The first ionization potentials for these enzymes were determined from the energy distribution curves of photoelectrons. The integral oscillator strengths for wavelengths ranging from 1050 to 2400 .ANG. were derived from the adsorption spectra: 168 for trypsin, 100 for RNase and 126 for lysozyme. Apparently, a considerable part of the absorption spectra for the wavelength region between the first ionization potential and 1050 .ANG. in these enzymes may be attributed to the excitations of highly excited states of peptide linkages.