| As a natural filament fiber,silk has a high value for taking and because of its good biocompatibility and unique mechanical properties,it is widely used in biomedicine,flexible electronic materials,biosensors and other fields.Modification of silk to obtain functionality,such as antibacterial,anti-ultraviolet,anti-yellowing properties,has been the focus of silk processing.Silk tyrosine has high biochemical reactivity,and its ratio to the total amino acid residues of silk protein molecules is large.Modified silk products based on silk tyrosine residues have the possibility of obtaining ideal results.Therefore,in this study,the tyrosine residue on the silk protein macromolecule was used as the modification site,and tyrosinase was used to oxidize it to the o-diphenol hydroxyl structure(dopa),and connected to the Branched aminophenylboronic acid,similar in structure to catechol.First,using free tyrosine as a substrate,the conditions of tyrosinase oxidation and aminophenylboronic acid grafting were studied.Then,the better process was used to modify silk fabrics to characterize the degree of tyrosine oxidation and amino acid.Graft ratio of phenylboronic acid;the light stability and antibacterial properties of the modified silk fabric were studied.Finally,the effects of modification on the basic structure and properties of silk fabrics were studied.It is hoped that this research can provide a technical reference for processing and modifying silk fabrics by similar methods in the future to obtain functional silk products.The main research contents and conclusions of this thesis are as follows:(1)Study on tyrosine enzymatic oxidation and APB A graft reactionWith free tyrosine substrate,the process conditions of tyrosinase oxidation of tyrosine were studied:the enzyme concentration was 6 U/mL,the reaction was performed at 25?,pH 6.5 for 130 min,and the tyrosinase activity was the strongest at this time.At the same time,HPLC proved that dopaquinone was not produced when ascorbic acid was present,and all products were dopa with o-diphenol hydroxyl group.By means of HPLC,ESI-MS and other detection methods,it was confirmed that aminophenylboronic acid can indeed react with dopa under certain conditions.The process conditions of the grafting reaction were studied by HPLC,and better conditions were obtained:80?,pH 8 for 240 min.(2)Study on light stability and antibacterial properties of modified silk fabricsThe silk fabric was modified by the obtained enzyme oxidation and aminophenylboronic acid grafting conditions,and the light stability and antibacterial properties of the modified silk fabric were studied.The ICP-MS test results showed that after the modification,there was 293.1 mg of boron in each kilogram of silk fabric,and almost no boron was present in the original silk,which strongly supported the occurrence of the grafting reaction.After 18 hours of light modification,the whiteness of the silk fabric decreased from 44.85 to 23.96,and the whiteness of the original fabric decreased from 57.66 to 22.58,indicating that the modification has a significant effect on improving the lightfastness and color stability of the silk fabric.After washing the modified silk fabric 20 times,the UPF value only decreased from 11.65 to 10.45,which has better UV protection performance.After the modified silk fabric was washed 20 times,the bacteriostatic rate against S.aureus and E.coli was 85.61%and 87.96%,respectively.After 12 hours of sunlight,the bacteriostatic rate against S.aureus and E.coli was 83.34%,80.65%,respectively,it has excellent antibacterial performance.(3)Effects of grafting reaction on the structure and basic wearability of silk fabricsThe effects of modification on the basic structure and basic wearability of silk fabrics were studied.The results show that the modification does not change the crystallinity of silk fibers and the thermal stability of fabrics but it will reduce its mechanical properties.After the modification,the whiteness of the fabric is reduced from 57.66 to 44.85,which indicates that the modification method has a whiteness on the fabric It has a certain effect;using different dyes to dye the fabric,it is found that the modification will increase the apparent dyeing depth of the dyed silk fabric,but the shade is basically the same,that is,it will not have a significant impact on the dyeing performance of silk fabric. |
PDF Full Text Request