Eelectrochemistry Chiral Sensors Based On Diphenylalanine And Bovine Serum Albumin

Chiral analysis is of significant importance in life sciences and modern chemical technologies.Chiral electrochemical sensors stand out among many chiral analytical technologies because they can easily convert chiral molecular recognition events to discernible changes in electrochemical signals.In recent years,great progresses have been achieved by using natural polysaccharides for chiral electrochemical sensing.However,amino acids,peptides and proteins are seldom used in electrochemical chiral recognition.In this thesis,several electrochemical chiral sensors based on diphenylalanine(FF)and bovine serum albumin(BSA)have been prepared and applied in the chiral sensing.This thesis is divided into three sections.As an extensively studied short peptide,FF can be self-assembled into highly ordered nano-/micro-structures.In this chapter,we report the electrochemical chiral recognition with three FF-based self-assemblies induced by graphene quantum dots(GQDs),chitosan(CS)and cetyltrimethylammonium bromide(CTAB),respectively.By optimizing the structure of the FF and tryptophan(Trp)enantiomers,it is known that more amount of L-Trp is included with these induced FF self-assemblies and then oxidized than its enantiomer.The recognition efficiency differs from each other for these as-prepared chiral sensing platforms,which can be due to their different structures formed during the self-assembly process.The self-assemblies of diphenylalanine(FF)and oxalic acid(OA)were prepared as the chiral sensing device for recognition of Trp isomers.The self-assemblies composed of OA and FF with different charging states(neutral,positively charged and negatively charged)exhibited quite different morphologies,resulting in significantly different chiral recognition ability toward the Trp isomers.Among them,the most prominent one is the self-assembly of OA and positively charged FF((+)FF-OA).It exhibit highly interconnected 3D network framework,and then the temperature sensitivity and chiral selectivity of the proposed FF-OA self-assemblies were alsostudied.In addition,the density mechanism theory(DFT)is used to further explore the recognition mechanism and chiral selectivity.From a practical point of view,the FF-OA self-assemblies were finally applied for the determination of precise levels of D-Trp in the non-racemic mixture of Trp isomers.As a widely studied serum protein,BSA has attracted increasing attention because of its advantages such as high solubility,low-cost and good biocompatibility.In this chapter,a biocompatible complex(BSA-GQDs)was prepared via the amidation reaction between the carboxyl group of GQDs and the amino group of BSA,and then the obtained BSA-GQDs was successfully applied in the electrochemical chiral recognition of Trp enantiomers.The regular morphology of BSA can be destroyed by the formed amide bond,leading to the changes in the spatial configuration of the peptide chain of BSA.Therefore,the intrinsic three-dimensional heart-shaped structure of BSA is expanded and the chiral sites on the peptide chain are more easily exposed.As a result,high recognition efficiency can be achieved at the BSA-GQDs modified electrode.