RESUMO
Crotoxin, the major neurotoxin of the South American rattlesnake venom (2 mg protein/ml in 0.85% NaCl) was irradiated with a Co-60 gamma source at a dose rate of 1100 Gy/h and at doses of 250, 500, 1000, 1500 and 2000 Gy. Irradiated crotoxin was analyzed for free SH-groups, protein concentration, electrophoretic profile (SDS-PAGE), 50% lethal dose (LD50) in mice, and antigenicity against crotalic antiserum by diffusion immunoassay. Irradiation led to the formation of protein aggregates and solubility was reduced at doses of 1000 Gy or higher. The LD50 increased about 2-fold for 1000 Gy and 3-5-fold for 1500 Gy. However, the antigenic response was not changed as judged by the capacity of irradiated protein receiving up to 1000 Gy to react with anti-Crotalus durissus terrificus venom horse serum. The dose of 1000 Gy cleaved 0.95 disulfide bridges/mol and 1500 Gy cleaved 1.42 bridges/mol, indicating the importance of disulfide bond integrity for toxicity