Enantioselective Recognition of Chiral Tryptophan with Achiral Glycine through the Strategy of Chirality Transfer.

Glycine (Gly), an achiral amino acid, has never been reported for enantioselective recognition owing to the absence of chiral sites. Herein, a facile strategy of chirality transfer is proposed to endow Gly with chirality. Optically active CuO, L-CuO, is first prepared, which can be used for the decoration of Gly through the formation of the Cu(Gly)2 complex. Successful chirality transfer from L-CuO to Gly is confirmed by circular dichroism (CD) spectra. The formation of the Cu(Gly)2 complex is further confirmed by Fourier transform infrared spectra and X-ray photoelectron spectroscopy. Next, the resultant L-CuO-Gly is used for chiral analysis of the isomers of tryptophan (Trp). Because of the higher affinity of L-CuO-Gly toward L-Trp than its isomer, the Trp isomers exhibit significant differences in their oxidation peak currents at the L-CuO-Gly-modified glassy carbon electrode (GCE) (IL-Trp/ID-Trp = 5.24). Finally, the practicability of the developed L-CuO-Gly/GCE is assessed, and the results indicate that it could be a reliable chiral sensor for the quantitative analysis of Trp isomers in nonracemic mixtures.

Covalent Functionalization of Bovine Serum Albumin with Graphene Quantum Dots for Stereospecific Molecular Recognition.

Stereospecific molecular recognition with simple and easily available proteins is of significant importance in life science and biomaterial science. Herein, we report on a chiral sensing platform, graphene quantum dots (GQDs)-functionalized bovine serum albumin (BSA), for chiral recognition of tryptophan (Trp) isomers. Amidation reaction between BSA and GQDs was directly responsible for the introduction of GQDs to BSA, resulting in significant changes in the spatial configuration of BSA and the exposure of more chiral sites at the protein surface. The BSA-GQDs-based chiral sensor exhibited good biomolecular homochirality in the recognition of Trp isomers, and the higher affinity of BSA-GQDs toward l-Trp than its isomer, d-Trp, was also revealed by density functional theory (DFT) considering the possible hydrogen bonds between the Trp isomers and the solvent-accessible residues of BSA.

Fabrication of CuO nanoparticles-decorated 3D N-doped porous carbon as electrochemical sensing platform for the detection of Sudan I.

In this study, a sensitive and selective electrochemical sensing platform for the detection of Sudan I was developed with CuO nanoparticles-decorated 3D N-doped porous carbon (CuO/3DNPC). 3D N-doped porous carbon (3DNPC) was first prepared by calcining the precursors of 3D integrated polysaccharides, and then it was decorated with CuO nanoparticles by hydrothermal method. The CuO/3DNPC modified electrode showed high sensitivity and wide linear range for the detection of Sudan I due to the excellent electrocatalytic activity of CuO and the accelerated electron transfer by 3DNPC. In addition, the proposed CuO/3DNPC also exhibited high selectivity, high reproducibility and stability in the detection of Sudan I. Finally, the CuO/3DNPC based Sudan I sensor was applied in the detection of Sudan I in ketchup and chilli sauces, and the results demonstrated the potential of the developed CuO/3DNPC as a promising electrode material for accurate assay of Sudan I in food samples.