A reusable sensing strategy employing magnetic nanoparticles and thymine-containing aptamers was developed to detect Hg(2+) in real water samples based on "turn-on" resonance light scattering. The LOD was as low as 500 fM (S/N = 3), and the present sensor can be repeatedly used for at least seven cycles.
In the present work, gold nanocluster (GNC) induced by bovine serum albumin (BSA) was synthesized as a novel fluorescence probe to detect nitrite (NO2(-)) sensitively and selectively. The fluorescence of GNC was found to be quenched effectively by NO2(-). Under the optimum conditions, it was found that the change of fluorescence intensity was proportional with the concentration of NO2(-) in the linear range of 0.1-50 μM (R = 0.9990), with a detection limit (S/N = 3) of 30 nM. The absorption spectroscopy, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS) studies were employed to discuss the quenching mechanism. In addition, the present approach was successfully applied in real water samples.
The mechanism of the interaction between bovine serum albumin (BSA) and ceftriaxone with and without zinc (II) (Zn2+) was studied employing fluorescence, ultraviolet (UV) absorption, circular dichroism (CD), and synchronous fluorescence spectral methods. The intrinsic fluorescence of BSA was quenched by ceftriaxone in a static quenching mode, which was authenticated by Stern-Volmer calculations. The binding constant, the number of binding sites, and the thermodynamic parameters were obtained, which indicated a spontaneous and hydrophobic interaction between BSA and ceftriaxone regardless of Zn2+. Changes in UV absorption, CD, and synchronous fluorescence spectral data are due to the microenvironment of amide moieties in BSA molecules. In the BSA-ceftriaxone-Zn2+ system, Zn2+ must first interact with ceftriaxone forming a complex, which inhibits BSA binding to ceftriaxone. The present work uses spectroscopy to elucidate the mechanism behind the interaction between BSA and ceftriaxone in the presence and absence of Zn2+. The BSA and ceftriaxone complex provides a model for studying drug-protein interactions and thus may further facilitate the study of drug metabolism and transportation.
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