Deuteron inactivation of dry bovine serum albumin

Abstract

The inactivation with deuterons of bovine serum albumin, as assayed by its ability to combine specifically with its homologous rabbit antiserum, is logarithmic when the samples are dissolved in phosphate buffer, indicating that the passage through the molecule of a single deuteron is capable of inactivating it. If the irradiated samples are dissolved in distilled water, a more rapid inactivation with dose is observed, and the inactivation curve has a possible multiple-hit character. The inactivation is shown to be the result of the molecule being made insoluble by the action of the radiation. The dependence of the inactivation with deuterons of various rates of energy loss is measured. It is shown that the results are consistent with either of two assumptions: that only about one-third of the primary ionizations cause permanent damage, or that several ionizations from the same charged particle are needed to inactivate one molecule. This is in marked contrast to results reported in the literature for various other dried proteins. The inactivation is greatly reduced by cooling the sample to liquid-air temperature during irradiation.