Xuyang Yan

Study of interaction between human serum albumin and three phenanthridine derivatives: fluorescence spectroscopy and computational approach.

Over the past decades, phenanthridine derivatives have captured the imagination of many chemists due to their wide applications. In the present work, the interaction between phenanthridine derivatives benzo [4,5]imidazo[1,2-a]thieno[2,3-c]quinoline (BTQ), benzo[4,5]imidazo[1,2-a]furo[2,3-c]quinoline (BFQ), 5,6-dimethylbenzo[4,5]imidazo[1,2-a]furo[2,3-c]quinoline (DFQ) and human serum albumin (HSA) were investigated by molecular modeling techniques and spectroscopic methods. The results of molecular modeling simulations revealed that the phenanthridine derivatives could bind on both site I in HSA. Fluorescence data revealed that the fluorescence quenching of HSA by phenanthridine derivatives were the result of the formation of phenanthridine derivatives-HSA complex, and the binding intensity between three phenanthridine derivatives and HSA was BTQ>BFQ>DFQ. Thermodynamics confirmed that the interaction were entropy driven with predominantly hydrophobic forces. The effects of some biological metal ions and toxic ions on the binding affinity between phenanthridine derivatives and HSA were further examined.

Synthesis of imidazole derivatives and the spectral characterization of the binding properties towards human serum albumin.

Small molecular drugs that can combine with target proteins specifically, and then block relative signal pathway, finally obtain the purpose of treatment. For this reason, the synthesis of novel imidazole derivatives was described and this study explored the details of imidazole derivatives binding to human serum albumin (HSA). The data of steady-state and time-resolved fluorescence showed that the conjugation of imidazole derivatives with HSA yielded quenching by a static mechanism. Meanwhile, the number of binding sites, the binding constants, and the thermodynamic parameters were also measured; the raw data indicated that imidazole derivatives could spontaneously bind with HSA through hydrophobic interactions and hydrogen bonds which agreed well with the results from the molecular modeling study. Competitive binding experiments confirmed the location of binding. Furthermore, alteration of the secondary structure of HSA in the presence of the imidazole derivatives was tested.

Evaluation of the binding of perfluorinated compound to pepsin: Spectroscopic analysis and molecular docking.

In this paper, we investigated the binding mode of perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) to pepsin using spectroscopies and molecular docking methods. Fluorescence quenching study indicated that their different ability to bind with pepsin. Meanwhile, time-resolved fluorescence measurements established that PFOA and PFNA quenched the fluorescence intensity of pepsin through the mechanism of static quenching. The thermodynamic parameters showed that hydrophobic forces were the main interactions. Furthermore, UV-vis, FTIR, three-dimensional fluorescence and molecular docking result indicated that PFCs impact the conformation of pepsin and PFOA was more toxic than PFNA. The conformational transformation of PFOA/PFNA-pepsin was confirmed through the quantitative analysis of the CD spectra. The present studies offer the theory evidence to analyze environmental safety and biosecurity of PFCs on proteases.

Interaction of human serum albumin with novel imidazole derivatives studied by spectroscopy and molecular docking

This study was a detailed characterization of the interaction of a series of imidazole derivatives with a model transport protein, human serum albumin (HSA). Fluorescence and time-resolved fluorescence results showed the existence of a static quenching mode for the HSA-imidazole derivative interaction. The binding constant at 296 K was in the order of 10(4) M(-1), showing high affinity between the imidazole derivatives and HSA. A site marker competition study combined with molecular docking revealed that the imidazole derivatives bound to subdomain IIA of HSA (Sudlows site I). Furthermore, the results of synchronous, 3D, Fourier transform infrared, circular dichroism and UV-vis spectroscopy demonstrated that the secondary structure of HSA was altered in the presence of the imidazole derivatives. The specific binding distance, r, between the donor and acceptor was obtained according to fluorescence resonance energy transfer.

Chloroacetate Promotes and Participates in the Oxidative Annulation of Pyridines/Isoquinoline by Using Oxygen as the Oxidant.

The aerobic oxidative annulation of chalcones, pyridines/isoquinoline and ethyl chloroacetate to indolizines was achieved by cascade reaction. Various functional groups on chalcones were tolerated. And different pyridines derivatives could also be suitable substrates. Ethyl chloroacetate is an essential component in participating of the oxidative annulation process. Overall, this protocol is very practical and efficient by using molecular oxygen as oxidant with high selectivity for the annulation product.

Elemental sulfur accelerated the reactivity of the 3-position of indole for the construction of chromeno[2,3-b]indoles

An intermolecular cross-cyclization between salicylaldehydes and indoles for the preparation of chromeno[2,3-b]indole derivatives was successfully developed by using elemental sulfur as the promoter and oxidant. Various chromeno[2,3-b]indoles can be prepared using indoles and salicylaldehydes bearing different functional groups. The preliminary mechanistic investigations demonstrated that elemental sulfur not only acted as an additional oxidant but also facilitated the reactivity of the 3-position of indole.