Development of a human serum albumin structure-based fluorescent probe for bioimaging in living cells

Assessment of the binding mechanism of ergothioneine to human serum albumin: Multi-spectroscopy, molecular docking and molecular dynamic simulation

Ergothioneine (EGT) has attracted great attention due to its extremely potent antioxidant properties, universally acknowledged as 'longevity vitamin'. In order to comprehensive understanding of its pharmacodynamics and pharmacokinetics, the binding mechanism of EGT with human serum albumin (HSA) was clarified by cutting-edged multi-spectroscopic approaches and in silico molecular docking coupled with molecular dynamic simulation. Our fluorescence quenching results revealed that the binding of EGT to HSA was in a static quenching mode validated by the descending Stern-Volmer constant (Ksv) values (2.82, 2.36, 1.48 × 104 L mol-1) and biomolecular quenching rate constant (Kq) values (2.82, 2.36, 1.48 × 1012 L mol-1) at 298 K, 305 K, and 310 K, respectively. van't Hoff criterion revealed the combination of EGT with HSA was a spontaneous exothermic process (ΔG = -24.16 kJ mol-1) via hydrogen bonding and van der Waals force interactions (ΔH = -60.25 kJ mol-1, ΔS = -129.44 J mol-1 K-1) at 310 K. The analysis of UV-vis absorption spectrum, synchronous fluorescence spectrum, three-dimensional fluorescence spectrum and circular dichroism indicated the addition of EGT affected the microenvironment of Trp214 and rearranged the structure of HSA. The binding replacement assay interpreted their binding site was near the subdomain IIA of HSA (Sudlow's site I), which was intuitively exhibited by molecular docking. In addition of obvious van der Wall forces, attractive charge and Pi-alkyl interactions, the chiral betaine group (N+(CH3+)3) in the side chain of EGT was inclined to form hydrogen bonds with Lys199, Ser287 and Arg257 in the hydrophobic cavity of albumin. Moreover, the dynamic simulation reinforced the equilibrium and stability of formed docking complex by four indicators (RMSD, RMSF, Rg, SASA) within 100 ns.

Enantioselective effects of chiral profenofos on the conformation for human serum albumin

Profenofos, as a typical chiral organophosphorus pesticide, can cause various environmental problems and even endanger human health when used in excess. The toxicity of chiral profenofos was investigated through multispectral analysis, molecular docking, and density functional theory (DFT), employing human serum albumin (HSA) as the model protein. Fluorescence titration and lifetime measurements demonstrated that the interaction between chiral profenofos and HSA involves static quenching. Chiral profenofos forms a 1:1 complex with HSA at site II (subdomain IIIA), primarily driven by hydrophobic interactions and hydrogen bonds. Notably, the binding efficacy diminishes as temperature increases. Spectroscopic analyses confirm that chiral profenofos alters the microenvironment and structure of HSA, with the R-enantiomer exerting a greater impact than the S-enantiomer. Consequently, the toxicological implications of the R-profenofos is significantly more pronounced. Investigating the molecular-level toxic effects of chiral pesticides enhances the thoroughness of pesticide assessments, aids in understanding their distribution, metabolism, and associated risks, and facilitates the development of mitigation strategies.

A novel FA1-targeting fluorescent probe for specific discrimination and identification of human serum albumin from bovine serum albumin

A novel probe C1 combining benzothiazole with a spiropyran section was developed for the specific detection of human serum albumin (HSA). The molecular docking suggested that the sulphonic acid group modification allowed C1 to form specific hydrogen bonds with lysine (Lys137) at fatty acid site 1 (FA1) of HSA, thus enabling fluorescence differentiation between HSA and BSA.

A novel fluorescence probe for the detection of water content in organic solvents and the distinction between deuterated and nondeuterated reagents

A novel D-π-A type fluorescent probe (probe 1) was developed for water content detection in organic solvents. By analyzing the relationship between fluorescence and water content, the probe was successfully applied to determine trace water content in tetrahydrofuran, ethyl acetate, 2-butanone, acetone, dimethylformamide, and acetonitrile. High water content in THF and ethyl acetate was associated with a gradual colour change from yellowish green to earthy yellow. The red/green value had a linear relationship with the water content in THF and ethyl acetate. There was a linear relationship between the red/blue value and water content in 2-butanone and acetone. Furthermore, probe 1 could be used for human serum albumin detection. Unexpectedly, probe 1 had a different colour response in deuterated and nondeuterated solvents, and had different fluorescence intensity and fluorescence emission wavelength. Probe 1 is rare tool that can distinguish between deuterated and nondeuterated reagents.

A near-infrared dicyanoisophorone-based fluorescent probe for discriminating HSA from BSA

Despite the rapid development of fluorescent probe techniques for the detection of human serum albumin (HSA), a probe that discriminates between HSA and bovine serum albumin (BSA) is still a challenging task, since their similar chemical structures. As a continuation of our work, herein, a dicyanoisophorone-based fluorescent probe DCO2 is systematically studied for discrimination of HSA from BSA. The photophysical and sensing performances of DCO2, including basic spectroscopic properties, sensing sensitivity, and selectivity, exhibits that DCO2 could selectively bind with HSA and display remarkable fluorescence enhancement (∼254-fold) at 685 nm. The gap of the fluorescent response of DCO2 between HSA and BSA is an obvious increase from 21% to 73% compared to the previous probe DCO1. The sensing mechanism was elucidated by Job's plot, displacement experiment, and molecular docking, suggesting that the specific response to HSA originated from the rigid donor structure and steric hindrance. DCO2 could be buried in the DS1 pocket of HSA, and only partly wedged into the DS1 pocket of BSA with exposing twisted N,N-diethylamino group outside. Application studies indicated that DCO2 has well detective behavior for HSA in the biological fluids. This work could provide a new approach to design HSA-specific near-infrared fluorescence probes.