Studies on photoyellowing of silk fibroin and alteration of its tyrosine content

The photoyellowing progress of silk fibroin and its influence factors under ultraviolet irradiation have been studied, which was conducted by combining different ultraviolet wavelengths, different ultraviolet irradiancies, and different irradiation times. The blue-ray whiteness after ultraviolet irradiation was tested to characterize the course of photoyellowing of silk fibroin. The result shows that the photoyellowing degree of silk fibroin varies significantly under ultraviolet irradiation of different wavelengths and with the increasing in ultraviolet irradiancy at 313-nm wavelength, the photoyellowing degree aggravates correspondingly, while the ultraviolet irradiancy at 340-nm wavelength has little obvious impact. Additionally, the photoyellowing degree of silk fibroin is positively correlated to ultraviolet irradiancy and irradiation time. To quantitatively analyze the alteration of tyrosine content during the photoyellowing of the silk fibroin, l-tyrosine standard curve Y = 8.14666X − 0.88951 was e...