Abstract:

In order to explore the regulation rules of chemical modification of tyrosine residues to realize the controlled chemical modification of silk fibroin, the effects of processing parameters including alkaline pretreatment, the dosage of diazonium salt, time and pH value on the modification of o-nitroaniline diazonium salt to tyrosine residues were analyzed, using the color depth K/S value of modified silk fibroin as the index. Meanwhile, the adsorption process adn type of adsorption isotherm of coupling modification of diazonium salt to tyrosine residues were also studied in the experiment. Results show that the Zeta potentialvalue of silk fibroin is reduced by alkali pretreatment, while the electron cloud density of the phenolic hydroxyl ortho carbon of tyrosine residues is increased, both of which promoted the adsorption of silk fibroin fibers on diazonium salt and increase the rate of coupling modification reaction. The silk fibroin fibers are modified in a bath with n (diazonium salt): n (tyrosine) = 2:3 at pH of 6.8 at 5 ℃ for 45 min, and then a higher K/S value is obtained. Moreover, the adsorption isotherm of tyrosine residue coupling reaction conforms to the Langmuir model.

Key words: silk, tyrosine residue, coupling reaction, K/S value, adsorption isotherm