Abstract
The reaction mechanism of rhodamine B (RHB) with bovine serum albumin (BSA) was investigated using fluorescence spectroscopy and synchronous fluorescence spectroscopy at different temperatures (298 K, 310 K and 318 K). The results showed that electrostatic force played a major role on the conjugation reaction between BSA and RHB, and the type of quenching was static quenching. Primary binding site for RHB was sub-hydrophobic domain IIA, and the number of binding sites was 1. The order of magnitude of binding constants ( K a ) was 10 4 . The value of Hill’s coefficients ( n H ) was approximately equal to 1, which suggested no cooperativity in BSA-RHB system. The donor-to-acceptor distance r < 7 nm indicated that the static fluorescence quenching of BSA by RHB was also a non-radiation energy transfer process. The results of two methods were consistent that showed the synchronous fluorescence spectroscopy could be used to study the reaction mechanism between drug and protein, and was a useful supplement to the conventional fluorescence quenching method.
Highlights
rhodamine B (RHB) is a strong fluorescence of synthetic dyes, and is used widely in biotechnology [1], printing [2], indicator of trace detection [3], etc
The results suggest that the interaction between RHB and bovine serum albumin (BSA) resulted in the formation of a new complex, and the content of α- helix was changed resulting in conformational changes of BSA
The intensity of the absorption peak at 275 nm was reduced, illustrating that the interaction between RHB and BSA happened in the ground-state molecules
Summary
RHB is a strong fluorescence of synthetic dyes, and is used widely in biotechnology [1], printing [2], indicator of trace detection [3], etc. Because of the bright color, strong stability and low price etc., RHB was added to food as food additives by some illegal businessmen, such as pepper products, bean products, condiment, etc. The research between small molecules and serum albumin can make us know their properties of forces and interaction mechanism at molecular level. Synchronous fluorescence spectroscopy was excitation and emission monochromators are scanned simultaneously to study the reaction mechanism between bovine serum albumin and substances. Chundan Wang et al.: Comparative Studies on the Interaction of Rhodamine B with Bovine Serum Albumin. Fluorescence quenching method is a commonly used method for studying the reaction mechanism of substances with bovine serum albumin, but the research by synchronous fluorescence method is less reported. Under the simulated physiological conditions, the interaction between RHB and BSA has been studied by fluorescence quenching spectroscopy and synchronous fluorescence spectroscopy. The research provides the help for understanding the toxicity of RHB, and urging people to improve the consciousness of food safety and ensure food safety
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