Thermoluminescence (TL) glow curves have been obtained for trypsin, trypsinogen, ribonuclease, and tryptophan irradiated with x-rays at 77°K in the form of dry films as well as in <tex-math>$\text{ethylene-glycol}/{\rm H}_{2}{\rm O}$</tex-math> glass. Except for ribonuclease and dry tryptophan which exhibited relatively weak TL, the spectra of the TL were recorded and compared to those observed during irradiation. It was found that the spectra of the TL of trypsin and trypsinogen both in the dry state and in glassy solution closely resembled the tryptophan-like part of their phosphorescence spectra, while no TL within the fluorescence band could be observed. There appeared to be no contribution to the TL from residues other than tryptophan. A comparison of the results obtained with trypsin and trypsinogen as well as with trypsin denatured by heat treatment indicated that the TL of these proteins was not critically dependent upon their tertiary or secondary structure.

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