Jifeng Liu

Probing the structure–activity relationship of a novel artificial cellobiose hydrolase

The remarkable catalytic properties of enzymes contribute to their unique 3D structures and arrangement of amino acid residues, which provide a blueprint for the design of artificial enzymes. Here, a series of peptide catalysts (PCs) that mimic the unique orientation and function of β-glycosyl hydrolases were designed. Transmission electron microscopy (TEM), fluorescence analysis, circular dichroism spectroscopy, X-ray diffraction and computational modeling were used to investigate and compare the relationship of the fibrinous structure of PCs with its glycoside hydrolysis activity. These results indicated that the catalytic activity of PCs was not only related to their amyloid-like structures, but it can also be influenced by the site, species, molecular arrangement and steric hindrance of the amino acid sequence. Whats more, this is the first report on peptide-inspired catalysts that mimic the natural cellobiose hydrolases. All this provided insights into the potential use of peptide nanoenzymes in the generation of efficient artificial enzymes.

Highly Bright Self-Assembled Copper Nanoclusters: A Novel Photoluminescent Probe for Sensitive Detection of Histamine

In this work, highly photoluminescent (PL) self-assembled copper nanoclusters (Cu NCs) capable of rapid, sensitive, and selective detection of histamine were developed. Cu NCs were synthesized in facile conditions by using 2,3,5,6-tetrafluorothiophenol (TFTP) as both the reducing agent and the protecting ligand, which exhibited intense saffron yellow (590 nm) PL via self-assembled induced emission (SAIE), and the absolute quantum yield (QY) of assembly was as high as 43.0%. The size, electronic states, and morphologies of the assembled nanoribbons were characterized, and the geometric structure and spectral properties of the Cu NCs were investigated by theoretical study. Furthermore, the mechanism of the excellent sensing performance of Cu NCs toward histamine was demonstrated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray analysis (EDX). With this sensing system, the amount of histamine in fish, shrimp, and red wine were analyzed, and experiment results verified the application of the sensor. Importantly, the luminescent test strips based on Cu NCs were fabricated for colorimetric detection of histamine in foods. This proposed technique may provide an alternative to traditional methods for histamine detection.

Study of Efficiency of Coupling Peptides with Gold Nanoparticles

Abstract Fluorescence spectroscopy was used to investigate the efficiency of coupling peptides to gold nanoparticles via 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride-N-hydroxysuccinimide (EDC-NHS). In this study, the effects of experiment conditions including the buffer solution (PBS, HEPES, Tris-HCl, and borate buffer solution), pH (6.5–9.0) and concentrations of buffer solution (10, 25, 40 and 50 mM), concentrations of NHS and EDC (from 0.2 M NHS-0.01 M EDC to 1.0 M NHS-0.5 M EDC), ratios of NHS to EDC (0, 0.5, 1.0, 2.0 and 2.5), and the coupling reaction time (4, 8, 12, 24 and 36 h) on the coupling efficiency were investigated and the optimized conditions were developed. These results indicated that the optimal experimental conditions were: pH 7.0 and 25 mM of the HEPES buffer solution, the concentrations ratios of NHS to EDC of 2:1 (0.4 M NHS-0.2 M EDC), and coupling reaction time of 24 h.

Antioxidant Assay Based on Quenching of Photocatalytically Generated Reactive Oxygen Species

Abstract A method based on photogeneration of OH radicals in water from TiO 2 nanoparticles was developed to study the kinetics of oxidation of organic molecules which were used as biological antioxidants. The kinetics of oxidation of terephthalic acid as a reference probe was monitored by fluorescence measurements of the concentration of its oxidized form, 2-hydroterephthalic acid ( λ ex =315 nm, λ em = 425 nm). The kinetics of oxidation of other antioxidant molecules was then deduced from the radical scavenging competition. The antioxidant properties of normal antioxidants were compared based on this kinetic model. And the antioxidant kinetic decreased in the order: lipoic acid, gallic acid, glutathione, uric acid, vitamin C, vitamin E, trolox and bilirubin.