Construction Of Tyrosine-Peptide Enzyme Mimics And Their Application

In this thesis,tyrosine-rich peptide YYHYY was used as research object to construct two kinds of enzyme mimics by covalent co-assembly and induced coassembly.The morphologies,structures and catalytic activities of these enzyme mimics were characterized and analysed by various methods.And they were applied to colorimetric and SERS detection.The main conclusions are as follows:(1)A robust peptide-based HRP mimic(CCA-YH)was developed through the covalent co-assembly strategy.Based on the co-assembly of tyrosine peptide YYHYY and hemin(CA-YH),a stable mimic enzyme(CCA-YH)was constructed by means of ruthenium-mediated tyrosine photo-crosslinking to generate the covalent bond of linked distyrosine.It was proved that it has histidine-hemin axial coordination similar to the catalytic active center of natural horseradish peroxidase(HRP).The results showed that CCA-YH had stronger peroxidase activity than CA-YH and the stability of CCA-YH was much higher than that of CA-YH and natural HRP under different p H,temperature,ion strength and organic medium conditions.In addition,CCA-YH displayed excellent reusability.Based on the favorable HRP-like catalytic activity of CCA-YH,a convenient colorimetric platform was established for the detection of glutathione,uric acid and sarcosine,which exhibited favorable specificity,wider linear range and lower LOD.(2)A nitroreductase mimic Y@Au was constructed by induced co-assembly strategy.Making use of the reductivity of tyrosine on the side chain of the peptide,the gold nanoparticles were generated by the in-situ reduction of chloroauric acid during the assembly.Finally,the Y@Au clusters loaded with a large number of uniform Au NPs were obtained.It was proved that Y@Au displayed favorable nitro reductase activity and excellent reusability.At the same time,Y@Au showed an excellent LSPR effect due to the cluster structure of gold nanoparticles.Raman spectroscopy was used to monitor the Y@Au catalyzed nitro reduction process of 4-NTP.The reaction kinetics was consistent with the pseudo-first-order kinetics,and the result was verified in agreement with the result obtained by UV-Vis spectroscopy.