Fluorescence and Circular Dichroism Dual-Mode Probe for Chiral Recognition of Tyrosine and Its Applications in Bioimaging.

Chiral amino acids (AAs) are essential in metabolism and understanding physiological processes, and they could be used as biomarkers for the diagnosis of different diseases. In this study, chiral Cdots@Van were prepared by postmodifying an achiral Cdots core with vancomycin for recognizing and determining the enantiomeric excess (ee) of tyrosine (Tyr) enantiomers. The fluorescence response of Cdots@Van is based on an "on-off" strategy, with different quenching percentages for d- and l-tyrosine. Interestingly, the circular dichroism (CD) spectrum of Cdots@Van responded to only one form of Tyr enantiomer, specifically d-Tyr, and remained nearly unchanged upon the addition of l-Tyr. Quantum mechanical (QM) calculations were in excellent agreement with the experimental results, confirming the stronger binding affinity of Cdots@Van for d-Tyr compared to l-Tyr. We further investigated the chiral recognition ability of the interconnected vancomycin particles, which was synthesized using the EDC/NHS coupling reaction between vancomycin molecules without a Cdots core. Surprisingly, unlike free vancomycin molecules, interconnected vancomycin displayed an enantiomeric recognition ability by CD spectroscopy, similar to what was observed for Cdots@Van. Crucially, this chiral probe has been successfully utilized for cell imaging applications.

A novel ratiometric fluorescence probe based on calix[4]arene functionalized polymer dots for bisphenol A detection in real water samples.

Bisphenol A (BPA) is one of key raw materials used in the production of epoxy resins and plastics, which has toxicological effects on humans by disrupting cell functions through a variety of cell signaling pathways. Therefore, it is of great significance to develop a simple, rapid, and accurate BPA detection method in real water samples. In this study, a ratiometric fluorescence method based on yellow-emitting surface-functionalized polymer dots (PFBT@L Pdots) and blue-emitting carbon dots (Cdots) was described for the detection of BPA. Pdots as the detecting part were synthesized by using highly fluorescent hydrophobic Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-(2,1',3)-thiadiazole)] (PFBT) polymer and (R)-5,11,17,23-Tetra-tert-butyl-25,27-bis[(diphenylphosphinoyl)methoxy]-26-(3-oxabutyloxy)-28-[(1-phenylethyl)- carbamoylmethoxy]calix [4]arene (L) functionalizing ligand, and Cdots as internal reference were prepared by hydrothermal treatment of citric acid and urea. In the presence of BPA, chemical binding of the phosphorus atoms of nearby PFBT@L Pdots with BPA hydroxyl functional groups led to the aggregation of the PFBT@L Pdots aggregation and quenching their yellow emission, but the blue emission of Cdots, on the other hand, remained stable. The proposed PFBT@L Pdots probe was successfully applied for the detection of BPA in real water samples, and the results were in good agreement with those obtained by HPLC-FLD. To the best of our knowledge, this is the first report that the calixarene has been utilized to modify Pdots.

Study on the interaction of antiviral drug 'Tenofovir' with human serum albumin by spectral and molecular modeling methods.

This study was designed to examine the interaction of Tenofovir (Ten) with human serum albumin (HSA) under physiological conditions. The binding of drugs with human serum albumin is a crucial factor influencing the distribution and bioactivity of drugs in the body. To understand the action mechanisms between Ten and HSA, the binding of Ten with HSA was investigated by a combined experimental and computational approach. UV-vis results confirmed that Ten interacted with HSA to form a ground-state complex and values of the Stern-Volmer quenching constant indicate the presence of a static component in the quenching mechanism. As indicated by the thermodynamic parameters (positive ΔH and ΔS values), hydrophobic interaction plays a major role in the Ten-HSA complex. Through the site marker competitive experiment, Ten was confirmed to be located in site I of HSA. Furthermore, UV-vis absorption spectra, synchronous fluorescence spectrum and CD data were used to investigate the structural change of HSA molecules with addition of Ten, the results indicate that the secondary structure of HSA molecules was changed in the presence of Ten. The experimental results were in agreement with the results obtained via molecular docking study.