Synthesis And Computational Chemistry Research Of Oxidized Polymerized Tyrosine For Copper Ion Detection

Small molecules can completely self-assemble into nanomaterials with unique structures,which are widely used in metal ion detection,drug delivery,signal transduction and other fields.Amino acid is one of the basic compound of living organisms to maintain physical activity choice,therefore the nanometer materials synthesized with amino acid as raw material present some natural advantages,such as low toxicity and high biocompatibility,which has been an important research direction in the field of nano biomedical material.And the amino acid nanomaterials based on nanomaterials autofluorescence as fluorescent indicator show wide development prospect in the field of material analysis.Nowadays,the selection of fluorescent indicators is not limited to fluorescent chemical dyes,and the preparation of fluorescent dyes by selecting amino acids as chromophores is also gradually rising.Most chromophores of fluorescent peptides contain aromatic amino acids,and the unique physicochemical properties of tyrosine(such as optics,oxidation-reduction and metal chelation)have become a hot research topic.However,there are few studies on self-assembly and polymerization of single tyrosine molecules.Hence,previous researches are besed on the self-assemble of peptides with tyrosine.In this work,we prepared tyrosine nanomaterials,and the research is divided into three parts for experiments.Firstly,tyrosine nanoparticles with fluorescence after oxidation polymerization were prepared by one-pot method,and sensors were designed based on their fluorescence characteristics to detect the copper ion,and the biological toxicity of the oxidation polymerized tyrosine nanoparticles were investigated.Secondly,The density functional theory with CAM-B3LYP method and appropriate basis set were used to calculate quantum chemistry of the simplified molecular structure to investigate the electron transfer of the molecule so as to achieve the purpose of understanding the mechanism that the photoluminescence of the oxidative polymerization tyrosine and the copper ion has the capability of the fluorescence quenching.Thirdly,by means of molecular dynamics simulation,the non-covalent bond interaction between copper ion and oxidative polymerization of tyrosine was investigated.And the main results are as follow:(1)The results indicate that tyrosine residues can be oxidized to benzoquinone groups under alkaline conditions,then polymerized and further self-assemble into nanoparticles with a size of about 5 nm.Under the ultraviolet light with a wavelength of 365 nm,the nanoparticles showed photofluorescence at 463 nm and showed specificity to copper ions.The two can spontaneously bind and quench fluorescence,and the quenching type is static quenching.(2)A fast and sensitive nano sensor for copper ion detection is developed.Copper ion concentration in the range of 40μM～1 m M,the standard curve for the copper ion is y=-2.1×10~5x+8.7×10~5,R~2=0.9916,and the detection limit is 37.26μM.The nanoparticles show low toxicity and excellent biocompatibility when co-cultured with A549 cells.(3)Quantum chemical calculation results show that oxidized polymerized tyrosine nanoparticles can produce fluorescence.The electron excitation analysis of the molecule shows that the lone pair electrons of the two oxygen atoms on the o-quinone jump to theπ*orbital of the benzene ring during the electron excitation,and it belongs to the local characteristic excitation of n->π*.In the presence of copper ions,electrons are excited to jump to the orbit of copper ions,which changes the electron density distribution and causes fluorescence quenching.(4)The molecular dynamics simulation results show that each copper ion can bond with at most two tyrosine oxide monomers in the simplified model under the interaction of van der Waals forces.