Electrochemical Chiral Recognition Of Proteins And Small Molecules

Chirality is the common phenomenon in nature. Most moleculars are chiral. Two enantiomers of one compound can exhibit significant differences in pharmacological activity, metabolic processes, metabolic rate and toxicity. Many reactions are chiral recognition in living organisms, and chiral recnognition is one of the important condtions for keeping the normal of the living body. Therefore, the investigation of the synthesis and enantioselective recognition of chiral compounds have important theoretical significance and application prospects in medicinal chemistry, drug design, food technology, biomedical and diagnostics as well as materials science, and it is also one of the active areas of chemical research. Developing a simple, rapid and accurate method for the chiral analysis has become a hot spot and forward direction. Many methods have been used for the chiral recongnition, and many significant progresses have been made over the past years. Among these approaches, electrochemical methods have attracted a lot of attention owing to the advantages of low cost, high sensitivity and simplicity. The dissertation includes four chapters, which are separately introduced as following:In chapter one, chirality and the importance of chiral recognition have been reviewed. Life is a typical chiral system, and chiral interaction phenomena are ubiquitous in nature. The study on chiral recongnition have important theoretical and practical significance, just as following:(1) pharmaceutical industry and medical research; (2) food analysis;(3) the field of life sciences; (4) chiral materials research; the analytical methods used for chiral recongnition including chiral chromatography, spectroscopy, electrochemical methods and microscopy techniques; The main chiral selectors for chiral recognition (protein, macromolecular metal complexes, chiral surfactants, chiral surfaces), and the mechanism of chiral recognition have been discussed.In chapter two, Electrochemical enantioselective recognition of tryptophane (Trp) enantiomers in the presence of Cu(II) using L-cysteine (L-Cys) self-assembled gold electrode is described. The scanning electron microscope (SEM) images have been utilized to discuss the surface morphous. The influence of the pH, interaction times and mental ions on the chiral recognition of Trp was investigated by cyclic voltammetry. The chiral recognition of Trp enantiomers was investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). The structure of the Cu complexes was optimized by the hybrid density functional theory (DFT) method. The results showed that L-Cys had stronger interaction with D-Trp than L-Trp in the presence of Cu(II), and the enantioselectively recognition was caused by the selective formation of Cu complex with L-Cys and Trp enantiomers. The enantiomeric composition of L- and D-Trp was monitored by measuring the current responses of the sample. It is further expand the application of the principle of chiral ligand exchange in the amino acid substances.In chapter three, the stereoselective interaction between human serum albumin (HSA) and N-isobutyryl-cysteine (NIBC) enantiomers was investigated by CV and EIS.The electrochemical responses of the NIBC enantiomers modified surfaces were varied along with the insert time and the concentration of HSA. The results showed that HSA molecule displayed different adsorption behavior on NIBC enantiomers modified surfaces and preferred to adsorb on the L-NIBC modified surface.In chapter four, a new chiral biosensor has been fabricated by immobilizing y-globulin on gold nanoparticles modified glassy carbon electrodes, which could recognize and detect mandelic acid (MA) enantiomers. Differential pulse voltammetry (DPV), QCM, ultraviolet-visible (UV-Vis) and atomic force micrograph (AFM) were used to characterize the enantioselectivity. The results exhibited that y-globulin modified electrode could enantioselective recognize MA enantiomers, and larger response signals were obtained from R-MA.Time dependencies of the enantioselective interaction were investigated. The enantionmeric composition of R- and S-MA enantiomer mixtures could be detemined by measuring the current responses of the sample. The developed electrodes have advantages of simple preparation, good stability and rapid detection. This investigation not only provides a new method for the enantioselective recognition of MA enantiomers, but also helps us understanding the interaction between proteins and mandelic acid.