Effect of gamma irradiation on the structural and physiological properties of silk fibroin

Abstract

This study was conducted to examine the changes in the molecular structure and physiological activities of silkfibroin by gamma irradiation. The results of gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gelelectrophoresis showed that the molecular weight of fibroin was increased depending upon the irradiation dose. Secondarystructure of fibroin determined by using circular dichroism revealed that the ratio of α-helix was increased up to 10 kGy andthen decreased depending upon the irradiation dose. Whereas, the ratio of β-sheet, β-turn, and random coil were decreased andthen increased with an alteration in the α-helix secondary conformation. The 2.2-diphenyl-1-picryl-hydrazil (DPPH) radicalscavenging activity of fibroin was increased by gamma irradiation at 5 kGy, but was decreased above 10 kGy depending uponthe irradiation dose. Also, the inhibition activities of tyrosinase and melanin synthesis of fibroin were increased by gammairradiation. These results indicated that gamma irradiation could be used as an efficient method to make fibroin more suitablefor the development of functional foods and cosmetics.