Charge Transport Through Supramolecular Interaction In Peptides Based On Molecular Scale Electrical Measurements

Peptide supramolecular interaction is the prerequisite for maintaining the secondary structure of biological macromolecules and enzyme-substrate recognition.Exploring the charge transport process of peptide supramolecular interaction at the molecular scale can not only deeply understand the complex information transfer process in vivo,but also be used to guide the research and development of biomedical products,which has the important value of reference for the design of highly bioactive polypeptide molecules and the fabrication of peptide-based molecular devices.However,there are still many controversies about the charge transport mechanism in peptides,which are mainly reflected in the differences between theoretical calculation results and single-molecule electrical measurements.In addition,it is difficult to reach a unified conclusion on the study of electrical characteristics based on the selfassembled monolayers electrical measurements and single-molecule break junction measurements.Therefore,the study of the complex supramolecular interactions between peptide chains is expected to be an important breakthrough to address these problems.This thesis focused on the the charge transport investigation through peptides exploring self-assembled monolayer and a peptide hydrogen-bonded dimers based on eutectic of gallium and indium technique(EGaln)and mechanically controllable break junction(MCBJ).In addition,the odd-even effect in peptide self-assembled monolayers was also observed for the first time.The importance of hydrogen-bond interaction between peptide chains on their electrical properties was also verified.The differences in charge transport mechanisms of van der Waals interactions,hydrogen bonds and ?-?stacking were further explored.The research contents and relevant conclusions of this thesis are shown as follows:1.EGaIn technique was used to explore the charge-transport characteristics of ferrocene-terminated Fc-(Gly)n-Cys peptide self-assembled monolayers.The roomtemperature construction of EGaIn//SAMs/Au(Ag)"sandwich" structure was realized with gold and silver as the bottom electrodes respectively,and the odd-even alternations of electrical parameters such as rectifier ratio,circuit density and junction rate were observed,which proved that the difference of hydrogen bonds between the peptide chains was the source of its odd-even effect.2.EGaIn technique was employed to further investigate the influence of different types of supramolecular interactions between peptide chains on their electrical transport process.Taking Fc-(Gly)n-Cys,Fc-(Pro)n-Cys and Fc-(Phe)n-Cys as the research systems,the charge transport characteristics of van der Waals force,hydrogen bonds and ?-? stacking between the peptide chains were studied.It was found that the charge transport mechanism was determined by the degree of assembly,supramolecular interactions and molecular orbital arrangement of peptides.3.Using the MCBJ technique,the difference of a single hydrogen bond on the charge transport was investigated from the scale of a peptide hydrogen-bonded dimer.Taking Cys-(Gly)n-Cys as the research system,gold/peptide...peptide/gold supramolecular junctions were constructed steadily at room temperature.The experimental results indicated that the conductance of the peptides showed a significant odd-even effect with the increase of the number of glycines.By combining the density functional theory,it was proved that the odd-even effect was caused by the steric hindrance effect of the carboxylic acid group and the difference of a single hydrogen bond.