Study On Chiral Recognitions Of Amino Acid, Hemoglobin By Electrochemistry

Chiral molecules are very important kinds of molecules in nature and livingthings, and widely studied in many areas in sciences. Electrochemical methodsgenerally are simple, fast and suitable for the on-site measurements. In this thesis,chiral electrodes were prepared by chemical modification of chiral molecules, and therecognition and interactions between chiral molecules and biological macromoleculeswith chiral electrodes were studied by several electrochemical methods such as cyclicvoltammetry，differential pulse, ac electrochemical impedance and open-circuitvoltage. The main results obtained are as follows:The carbon paste electrode with silicone oil as the binder was modified withβ-cyclodextrin, and used to recognize chirality of tyrosine enantiomer by cyclicvoltammetry and differential pulse. The experimental conditions were optimized suchas the mixing ratio (0.25%) of graphite powder andβ-CD, pH value (7.8), interactiontime (70 s). When concentration of chiral tyrosine enantiomers is 0.004mmol/L, onlyL–tyrosine was recognized and gives out electronic response. The modified electrodecan distinguish L–tyrosine from the D-tyrosine.A chiral carbon fiber cluster electrode was prepared firstly by electrochemicallydeposition of gold thin layer film and then chemically modified by self assemblying ofL-cysteine on the surface of gold layer. The recognitions of L-tyrosine with the chiralelectrode were studied by ac electrochemical impedance spectrometry. The resultsshow that interaction between L-cysteine modified electrodes and L-tyrosine isstronger than D-tyrosine, and result in the great changes of film resistance.This resultoffers a new way for the study of recognition of chiral enantiomers.The interactions between bovine hemoglobin with the L-cysteine self assemblymembrane were studied by ac electrochemical impedance spectrometry. The resultsshow that interaction of bovine hemoglobin with the chrical electrode is stronger atpH= 6.5 mainly through the electrostatic forces between the positive and negativecharges of protein and L-cysteine molecules. This method may be used in thedetection of bovine hemoglobin solution quantitatively.The chirality recognition of tyrosine enantiomers were also studied byopen-circuit voltage method with L-cysteine self assembly membrane modifiedelectrode. The interaction of L-tyrosine with the chrical electrode shows an obviousphase transition process, but not for D-tyrosine, which gives out an exponential decaycurve. The potential differences in the open circuit potential curves at given time areproportional to the concentrations of tyrosine, which may be used in the detection of the chiral molecules.