Optimization of aflatoxin B1 removal efficiency of DNA by resonance light scattering spectroscopy.

In this paper, firstly, the resonance light scattering spectra of aflatoxin B1 (AFB1) and DNA were measured by resonance light scattering spectroscopy (RLS), and the DNA binding saturation value (DBSV) of AFB1 was calculated from their spectral results. Then the interaction intensity between DNA and AFB1 and the effects of some external factors on the interaction between DNA and AFB1 were evaluated by corresponding DBSVs, so as to establish and optimize a way for removing AFB1 by DNA. DBSV of AFB1 was 2.04 at 30℃ and pH 7.40. However, after adding sodium ion, calcium ion, vitamin E, vitamin C and D-glucose, DBSV of AFB1 was changed to 2.72, 3.17, 2.67, 1.68 and 1.33 respectively. Correspondingly, the removal efficiency of AFB1 by DNA was changed from 90.05% to 93.25%, 95.48%, 93.08%, 82.36% and 78.90% respectively. These results indicated that the external factors had a significant impact on the interaction between DNA and AFB1. Among them, some factors enhanced the interaction between DNA and AFB1, while some factors weakened the interaction between DNA and AFB1. The change of these external factors led to the corresponding changes in DBSV and the removal efficiency of AFB1. DBSV of AFB1 could really be used as an index to evaluate the intensity of the interaction between DNA and AFB1, and to optimize the removal efficiency of AFB1 by DNA. The experimental data also showed that the adsorption of AFB1 to DNA was consistent with the pseudo-second-order kinetic model and the Freundlich isothermal model, was an exothermic and spontaneous process. All these results will give good references for establishing and optimizing a way of AFB1 removal via DNA intercalation.

Using resonance light scattering and UV/vis absorption spectroscopy to study the interaction between gliclazide and bovine serum albumin.

At different temperatures (298, 310 and 318 K), the interaction between gliclazide and bovine serum albumin (BSA) was investigated using fluorescence quenching spectroscopy, resonance light scattering spectroscopy and UV/vis absorption spectroscopy. The first method studied changes in the fluorescence of BSA on addition of gliclazide, and the latter two methods studied the spectral change in gliclazide while BSA was being added. The results indicated that the quenching mechanism between BSA and gliclazide was static. The binding constant (Ka ), number of binding sites (n), thermodynamic parameters, binding forces and Hill's coefficient were calculated at three temperatures. Values for the binding constant obtained using resonance light scattering and UV/vis absorption spectroscopy were much greater than those obtained from fluorescence quenching spectroscopy, indicating that methods monitoring gliclazide were more accurate and reasonable. In addition, the results suggest that other residues are involved in the reaction and the mode 'point to surface' existed in the interaction between BSA and gliclazide. Copyright © 2015 John Wiley & Sons, Ltd.

Comprehensive studies on the interaction of copper nanoparticles with bovine serum albumin using various spectroscopies.

Copper nanoparticles (NPs) of average size of ~7.5nm were synthesized by chemical reduction method. Fluorescence spectroscopy in synchronous and polarization modes were used to examine the nature of interaction between Cu NPs and bovine serum albumin (BSA) at different temperatures. Fluorescence quenching results suggest that Cu NPs interact with BSA molecule through static mechanism, as inferred from the quenching of BSA fluorophore. The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) hint that the binding process occurs spontaneously by involving hydrophobic forces. Synchronous fluorescence spectra reveal that the interaction of Cu NPs with BSA mostly changes the microenvironment of tryptophan and not of tyrosine residues. The formation of BSA-Cu NPs ground state complex was also confirmed from the resonant light scattering and fluorescence polarization spectra. Circular dichroism and Raman spectra indicate that α-helicity of the BSA decreases due to the interaction with Cu NPs. It was also found that Cu NPs are located in the close proximity of BSA molecule, which transfer energy efficiently from the excited state of BSA fluorophore to the Cu NPs.