Determination of fluoroquinolones in chicken muscle by molecularly imprinted graphitic carbon nitride-based solid-phase extraction and ultra-performance liquid chromatography.

A graphitic carbon nitride was synthesised and nalidixic acid (NA) based molecularly imprinted microspheres (MIMs) were polymerised on its surface to create a composite material. After characterisation and evaluation of its absorption ability, the composite was used to prepare a solid-phase extraction (SPE) cartridge for purification of fluoroquinolones in chicken muscle, analysed by ultra-performance liquid chromatography. The cartridge showed high absorption capacities (378-559 µg) and high recoveries (92.1-99.4%) for eight fluoroquinolones, and could be reused at least 20 times. The limits of detection for the 8 drugs were 0.2-0.8 ng g-1, and recoveries from standard fortified blank chicken muscle samples were 71.9-96.8%. This is the first study reporting the use of molecularly imprinted graphitic carbon nitride composite to determine the residue of veterinary drug in foods of animal origin.

[Spectroscopic study on the interaction between resveratrol and human serum albumin].

The interaction between resveratrol and human serum albumin (HSA) was studied by using fluorescence quenching spectra, synchronous fluorescence spectra and ultra-violet spectra. The Stern-Volmer curve of the fluorescence quenching of HSA by resveratrol indicated that the quenching mechanism between resveratrol and HSA was mainly static quenching, with nonradiation energy transfer occurring within single molecule. The binding constants (KA) were 2.39 x 10(5) (25 degrees C), 1.25 x 10(5) (35 degrees C) and 1.10 x 10(5) (45 degrees C), respectively. According to the Forster theory of nonradiation energy transfer, the binding distances (r) were 3.02 nm (25 degrees C), 3.46 nm (35 degrees C) and 3.79 nm (45 degrees C), respectively. The thermodynamic parameters showed that the interaction between resveratrol and HSA was mainly driven by hydrophobic force. Synchronous spectrum was used to investigate the conformational change of HSA.

Interaction of tetrandrine with human serum albumin: a fluorescence quenching study.

The interaction of tetrandrine with human serum albumin (HSA) was studied by measuring fluorescence quenching spectra, synchronous fluorescence spectra and ultra-violet spectra. The fluorescence quenching spectra of HSA in the presence of tetrandrine showed that tetrandrine quenched the fluorescence of HSA. The quenching constants of tetrandrine on HSA were determined using the Stern-Volmer equation. Static quenching and non-radiation energy transfer were the two main reasons leading to the fluorescence quenching of HSA by tetrandrine. According to the Förster theory of non-radiation energy transfer, the binding distances (r) and the binding constants (K(A)) were obtained. The thermodynamic parameters obtained in this study revealed that the interaction between tetrandrine and HSA was mainly driven by a hydrophobic force. The conformational changes of HSA were investigated by synchronous spectrum studies.

[Study on the interaction between fangchinoline and bovine serum albumin].

The binding reaction of fangchinoline with bovine serum albumin was studied at different temperatures by fluorescence quenching spectra, synchronous fluorescence spectra and ultra-violet spectra. It was shown that fangchinoline has a strong ability of quenching the fluorescence of BSA. The Stern-Volmer curve of the fluorescence quenching of BSA by fangchinoline indicated that the quenching mechanism of fangchinoline to BSA was a static quenching. According to the Förster theory of non-radiation energy transfer, the binding distances (r) at different temperature were 2.51 nm (27 degrees C), 2.72 nm (37 degrees C) and 2.89 nm (47 degrees C), respectively, while the binding constants (KA) were 1.05 x 10(5) L x mol(-1) (27 degrees C), 3.31x 10(5) L x mol(-1) (37 degrees C), and 7.24 x 10(5) L x mol(-1) (47 degrees C), respectively. The thermodynamic parameters showed that the interaction of fangchinoline and BSA was mainly driven by hydrophobic force. Synchronous spectrum was used to investigate the conformational changes of BSA.