On the X-Ray Inactivation at Various Temperatures of Trypsin in Dry State and Aqueous Solution

Abstract

The X-ray sensitivity of trypsin has been studied both in dry state and in dilute solution (0.1 mg/ml) of 10^-3 N HCl, as a function of the sample temperature during irradiation. Oxygen present during irradiation acts as a sensitizer when the exposure is carried out in frozen aqueous solution as well as in dry state, but it acts as a protector when the enzyme solution is exposed at room temperature. There is a considerable indirect effect when trypsin is exposed in frozen aqueous solution, above 200 °K, and even at 77 °K a small indirect effect is apparent. When trypsin is exposed in 10^-3 N HCl at room temperature about 85 per cent of the indirect effect is eliminated when the solution is saturated with O₂ , (known as an effective scavenger for e ^⊖ _aq and H) and most of the remaining indirect effect is eliminated if the enzyme solution also contains 100 mM C₂H₃OH (known as an effective OH scavenger).