Effect of long wave u.v. irradiation on the affinity of haemoglobin for oxygen

Changes in the slope of haemoglobin-oxygen dissociation curve and its position were studied before and after the influence of long wave u.v. irradiation. Haemoglobin showed a lower than normal affinity for oxygen when exposed to 5.45 x 10(-3) J/cm2 and to lesser extent to doses of 10.90 x 10(-3) J/cm2. The elevation in P50 (representing PO2 at which Hb is half saturated) at these doses is mainly due to the new acidic groups which, by unfolding of this globular protein, become exposed in its surface. The fall in P50 at relatively high doses was found as a result of methaemoglobin increase and the partial dissociation of Hb tetramer to dimer and monomer.