Coupling of Dyes to Various Macromolecules by means of Gamma-irradiation

Abstract

DURING studies of the ability of various substances to protect serum albumin solutions against radiation damage, it was found that some of the substances used were bound to the serum albumin. A 1.0 per cent bovine serum albumin solution of pH 7.0 containing 0.5 mmoles fluorescein was irradiated with 2 × 10⁵ rad of gamma-irradiation from a ⁶⁰Co source (184 rad/s). Extensive dialysis against 0.1 M NaCl solution and water showed that, although most of the fluorescein could be removed by dialysis, there was a part left which could not be separated from the protein. Dialysis against 8 M urea was also ineffective. Determination of the visible spectrum of a sample that had been extensively dialysed against 0.02 M phosphate buffer (pH 8.0) showed that it was almost identical to that of fluorescein with the exception that the maximum was at 497 nm instead of at 491 nm.