Fluorescence quenching and ligand binding: A critical discussion of a popular methodology

Interaction of malachite green with bovine serum albumin: determination of the binding mechanism and binding site by spectroscopic methods.

China has relatively abundant rare earth elements (REEs) reserves and will continue to be one of the major producers of REEs for the world market in the foreseeable future. However, due to the large scale of mining and refining activities, large amounts of REEs have been released to the surrounding environment and caused harmful effects on local residents. This paper summarizes the data about the contents and translocation of REEs in soils, waters, atmosphere, and plants in REE mining areas of China and discusses the characteristics of their forms, distribution, fractionation, and influencing factors. Obviously high concentrations of REEs with active and bioavailable forms are observed in all environmental media. The mobility and bioavailability of REEs are enhanced. The distribution patterns of REEs in soils and water bodies are all in line with their parent rocks. Significant fractionation phenomenon among individual members of REEs was found in soil-plant systems. However, limited knowledge was available for REEs in atmosphere. More studies focusing on the behavior of REEs in ambient air of REE mining areas in China are highly suggested. In addition, systematic study on the translocation and circulation of REEs in various media in REEs mining areas and their health risk assessment should be carried out. Standard analytical methods of REEs in environments need to be established, and more specific guideline values of REEs in foods should also be developed.

State of rare earth elements in different environmental components in mining areas of China.

Flavones correspond to a flavonoid subgroup that is widely distributed in the plants, and which can be synthesized by different pathways, depending on whether they contain C- or O-glycosylation and hydroxylated B-ring. Flavones are emerging as very important specialized metabolites involved in plant signaling and defense, as well as key ingredients of the human diet, with significant health benefits. Here, we appraise flavone formation in plants, emphasizing the emerging theme that biosynthesis pathway determines flavone chemistry. Additionally, we briefly review the biological activities of flavones, both from the perspective of the functions that they play in biotic and abiotic plant interactions, as well as their roles as nutraceutical components of the human and animal diet.

Flavones: From Biosynthesis to Health Benefits

This study was designed to examine the interaction of dexamethasone (DEX) with bovine serum albumin (BSA) and human serum albumin (HSA) under physiological conditions with drug concentrations in the range of 2.5-20 microM and BSA/HSA was fixed at 5.0 microM. Spectroscopic analysis of the emission quenching at different temperatures revealed that the quenching mechanism of serum albumin by dexamethasone is static quenching mechanism. The binding sites number, n and binding constant, K were obtained at various temperatures. The distance r between dexamethasone and the protein was evaluated according to the theory of Foster energy transfer. The result of fluorescence spectra UV-vis absorption spectra and FT-IR spectra showed that the conformation of bovine serum albumin and human serum albumin has been changed in the presence of dexamethasone. The thermodynamic parameters, free energy change (DeltaG(0)), enthalpy change (DeltaH(0)) and entropy change (DeltaS(0)) for BSA-DEX and HSA-DEX were calculated according to van't Hoff equation and discussed.

Interaction between a potent corticosteroid drug – Dexamethasone with bovine serum albumin and human serum albumin: A fluorescence quenching and fourier transformation infrared spectroscopy study

Study of the interaction between icariin and human serum albumin by fluorescence spectroscopy

Spectroscopic investigation of the interaction between chrysin and bovine serum albumin

Interaction of the irisflorentin with bovine serum albumin: A fluorescence quenching study

Spectroscopic studies on the interaction of morin–Eu(III) complex with calf thymus DNA

The interaction of hesperidin (HES) or icariin (ICA) and lysozyme (LYS) was studied by fluorescence spectroscopy in physiological buffer solution. It was observed that there was a strong fluorescence quenching effect of hesperidin or icariin on lysozyme. The quenching constants of the drugs with lysozyme were measured at different temperatures, and the quenching mechanism was suggested as dynamic quenching for HES-LYS system and both static and dynamic quenching for ICA-LYS system. The thermodynamic parameters of the interaction of hesperidin or icariin and lysozyme were measured according to the Van's Hoff equation: the enthalpy change (DeltaH) and the entropy change (DeltaS) of HES-LYS system and ICA-LYS system were calculated to be 20.29 kJ x mol(-1) and 146.28 J x mol(-1) x K(-1), and -3.47 kJ x mol(-1) and 81.16 J x mol(-1) x K(-1), respectively, which indicated that the interaction of hesperidin and lysozyme was driven mainly by hydrophobic force, whereas the interaction of icariin and lysozyme was driven mainly by electrostatic force. It was showed that the reaCtion processes of the two systems occurred spontaneously since Gibbs free energy change (DeltaG) values were negative. The binding distances of hesperidin and icariin from the lysozyme tryptophan residue were calculated to be 1.34 nm and 1.24 nm, respectively, based on the Forster's theory of non-radiation energy transfer. The results of synchronous fluorescence spectra showed that the binding of hesperidin or icariin to lysozyme induced conformational changes in lysozyme.

Guowen Zhang

Papers

Study of the interaction between icariin and human serum albumin by fluorescence spectroscopy

Spectroscopic investigation of the interaction between chrysin and bovine serum albumin

Interaction of the irisflorentin with bovine serum albumin: A fluorescence quenching study

Spectroscopic studies on the interaction of morin–Eu(III) complex with calf thymus DNA

Study on the interaction of hesperidin or icariin with lysozyme by fluorescence spectroscopy