Qiao Chen

Electrochemical enantioselective recognition of tryptophane enantiomers based on chiral ligand exchange

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 chiral recognition of Trp enantiomers was investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). Time dependencies of the enantioselective interaction for the L-Cys modified electrodes with Trp enantiomers solutions in the presence of Cu(II) were also studied. The results showed that L-Cys had stronger interaction with D-Trp than L-Trp in the presence of Cu(II), and the discrimination was caused by the selective formation of Cu complexes with L-Cys and Trp enantiomers relying on the principle of chiral ligand exchange. The structure of the Cu complexes was optimized by the hybrid density functional theory (DFT) method. And the enantiomeric composition of L- and D-Trp was monitored by measuring the current responses of the sample.

Enantioselective recognition of mandelic acid based on γ-globulin modified glassy carbon electrode.

A new chiral biosensor has been fabricated by immobilizing γ-globulin on gold nanoparticles modified glassy carbon electrodes, which could recognize and detect mandelic acid (MA) enantiomers. Differential pulse voltammetry, quartz crystal microbalance, ultraviolet-visible spectroscopy, and atomic force microscopy were used to characterize the enantioselectivity. The results exhibited that γ-globulin modified electrode could enantioselectively recognize MA enantiomers, and larger response signals were obtained from R-MA. The factors influencing the performance of the resulting biosensor were investigated. The enantiomeric composition of R- and S-MA enantiomer mixtures could be determined by measuring the current responses of the sample. The developed electrodes have the advantages of simple preparation, good stability, and rapid detection.

A new chiral electrochemical sensor for the enantioselective recognition of penicillamine enantiomers

A new chiral electrochemical sensor has been successfully prepared through chemical linking l-methotrexate (l-Mtx) onto the gold electrode surface. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the enantioselective interaction between l-Mtx and Pen enantiomers. The results showed that the l-Mtx-modified gold electrode can selectively recognize penicillamine (Pen) enantiomers using Zn(II) as central ion, and larger response signal was observed from d-Pen owing to the selective formation of Zn complexes. The interaction time between the modified electrode and Pen enantiomers containing Zn(II) was considered. And the electrochemical response of the modified electrode to a series of different concentration of Pen in the presence of Zn(II) was also monitored. In addition, the enantiomeric composition of d- and l-Pen enantiomer mixtures was monitored by measuring the current responses of the sample.

The application of chiral arginine and multi-walled carbon nanotubes as matrices to monitor hydrogen peroxide

The enantioselective interaction between horseradish peroxidase (HRP) and arginine enantiomers was investigated by electrochemical methods through studying the electrocatalytic activity of H2O2 biosensor, which was obtained through l-arginine or d-arginine functionalized multi-walled carbon nanotubes (d-Arg-MWCNTs or l-Arg-MWCNTs) immobilizing horseradish peroxidase (HRP) on glassy carbon electrode. Cyclic voltammetric and chronoamperometry were used to characterize the properties of the biosensor. Under the optimal conditions, LAM-CS@HRP/dpAu/GCE biosensor showed better electrocatalytic activity to H2O2 compared to DAM-CS@HRP/dpAu/GCE and MWCNTs-CS@HRP/dpAu/GCE, implying that the different configurations of nanocomposites have different interactions with HRP. The currents of LAM-CS@HRP/dpAu/GCE biosensor had a linear relationship with the concentration of H2O2 in the range of 2.5×10(-6) to 2.9×10(-3)M with a detection limit of 8.3×10(-7)M (S/N=3). For MWCNTs-CS-HRP/dpAu/GCE electrode, the calibration range of H2O2 was from 6.4×10(-4) to 2.9×10(-2)M and a detection limit of 2×10(-5)M (S/N=3). For the case of DAM-CS@HRP/dpAu/GCE, there has a linear relationship with the concentration of H2O2 from 1.8×10(-5) to 2.6×10(-3)M and the detection limit is 6×10(-5)M (S/N=3).

Chiral Discrimination of Tryptophan Enantiomers via (1R, 2R)-2-Amino-1, 2-Diphenyl Ethanol Modified Interface

The paper reported that a simple chiral selective interface constructed by (1R, 2R)-2-amino-1, 2-diphenyl ethanol had been developed to discriminate tryptophan enantiomers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the characteristic analysis of the electrode. The results indicated that the interface showed stable and sensitive property to determine the tryptophan enantiomers. Moreover, it exhibited the better stereoselectivity for L-tryptophan than that for D-tryptophan. The discrimination characteristics of the chiral selective interface for discriminating tryptophan enantiomers, including the response time, the effect of tryptophan enantiomers concentration, and the stability, were investigated in detail. In addition, the chiral selective interface was used to determine the enantiomeric composition of L- and D-tryptophan enantiomer mixtures by measuring the relative change of the peak current as well as in pure enantiomeric solutions. These results suggested that the chiral selective interface has the potential for enantiomeric discrimination of tryptophan enantiomers.

Stereospecific redox reaction of ascorbic acid and isoascorbic acid based on chiral electropolymerized films

A simple and fast strategy for stereospecific redox reaction is proposed using glutamic acid enantiomer electropolymerized films. The mechanism of enantioselectivity on the electropolymerized films has been explored.