Research On The Modification Mechanism Of Fibroin With Aromatic Primary Amine Compounds

Fibroin is a protein material wrapped in silk after degumming treatment.As a biomedical material with both biocompatibility and natural macromolecule properties,silk fibroin has become a hot research topic in the field of biomedicine in recent years.The study on the chemical modification of natural primary silk protein and its mechanism of action not only has guiding significance for the functionalization of silk protein material,but also has theoretical value for developing new protein modification methods.According to the research of the three-component Mannich reaction principle that the complex compounds containing aromatic primary amine group introduced into the chymotrypsinogen tyrosine residues.In this paper,some primary amine containing dyes have been selected as the developing reagents for fibroin chemical modification.And by means of elemental analysis,high performance liquid chromatography,mass spectrometry and other means of test characterization carried out three aspects:(1)Optimization of modified reaction conditions(temperature,time,formaldehyde Dosage,p H,and bath ratio)to explore the fixation rate of fibroin on the aromatic primary amine compounds under the action of formaldehyde.(2)A variety of active amino acids and peptides were selected as reaction simulants.Modification sites and reaction mechanism.(3)Through the charge effect study,the influence of the charging characteristics of fibroin and aromatic-primary amine dyes on the physical adsorption and chemical modification of aromatic amine dyes on silk fibroin fabrics was revealed,and the modification was controlled.The results showed that when the molar ratio of aromatic amine compounds to formaldehyde is 1:30,p H 4,reaction temperature 30 ?,time 10 hours and bath ratio 1:50,the color depth(K / S)up to 16,color depth after stripping DMF(K / S)of 9.And by elemental analysis and hydrolysis dialysis experiments,the aromatic amine compounds to silk fibroin chemical modification,measured fixation rate of 55%.A variety of active amino acids and peptides were selected as silk fibroin analogues with aromatic amine compounds to simulate the reaction.The chemical modification sites were determined by TLC,ion trap mass spectrometry,high performance liquid chromatography and liquid chromatography-mass spectrometry Amino acids,excluding the reactivity of other active amino acids.When the pH is 4,the fabric of silk fibroin is positively charged and the compound of aromatic amine is obviously electronegative.Both of them are physically adsorbed under the opposite charge attraction,so that more aromatic amine compounds are adsorbed on the silk fibroin fabric Is conducive to the occurrence of reaction modification.However,the content of fuming powder(pH?4)or promoting effect(pH?5)is different with the electrification of silk fibroin fabric,but it has little effect on the fixation rate.when the molar ratio of the aromatic amine compound to formaldehyde is 1:30,pH 4,reaction temperature is 30?.,time is 10 hours and bath ratio is 1:50,the aromatic primary amine compound can chemically modify silk fibroin with formaldehyde,The main modification site for the tryptophan residues,and can be achieved by adding sodium sulfate controllable reaction.