Structural Alterations in Horse Heart Myoglobin by Gamma Radiation

Aggregation of horse heart myoglobin was consistently observed as a function of radiation dose at a concentration of 6-8 mg/ml. At 100 krad, 19% of the aggregates was soluble in 6 M urea, while at a higher dose of 500 krad only 8% of the aggregates were soluble. Polyacrylamide gel-disc electrophoresis of the soluble portion indicated the formation of an additional band at 100 krad but there was diffusion of these bands at higher doses. The visible and ultraviolet spectra of the 6 M urea soluble aggregates revealed the presence of the protoprophyrin nucleus as well as the apoglobin moiety. Formation of the aggregates is explained on the basis of the interaction between the parent molecules and the product molecules resulting from radiation induced micro-heterogeneity.