Interactions of acidic pharmaceuticals with human serum albumin: insights into the molecular toxicity of emerging pollutants

Testing for Ketoprofen Binding to HSA Coated Magnetic Nanoparticles under Normal Conditions and after Oxidative Stress

Binding and transport of ligands is one of the most important functions of human blood serum proteins. Human serum albumin is found in plasma at the highest concentration. Because of this, it is important to study protein–drug interactions for this albumin. Since there is no single model describing this interaction, it is necessary to measure it for each active substance. Drug binding should also be studied in conditions that simulate pathological conditions of the body, i.e., after oxidative stress. Due to this, it is expected that the methods for testing these interactions need to be easy and fast. In this study, albumin immobilized on magnetic nanoparticles was successfully applied in the study of protein–drug binding. Ketoprofen was selected as a model drug and interactions were tested under normal conditions and artificially induced oxidative stress. The quality of obtained results for immobilized protein was confirmed with those for free albumin and literature data. It was shown that the type of magnetic core coverage does not affect the quality of the obtained results. In summary, a new, fast, effective, and universal method for testing protein–drug interactions was proposed, which can be performed in most laboratories.

Oxidative degradation of diclofenac by thermally activated persulfate: implication for ISCO

Diclofenac (DCF), one of the typically recalcitrant pharmaceuticals, has been frequently detected in groundwater in recent years. This work investigated the performance of DCF degradation by thermally activated persulfate (PS) to further understand its application in in situ chemical oxidation (ISCO) for DCF-contaminated groundwater. The effects of various factors, including activation temperature, solution pH, PS/DCF ratio, and common constitutes, e.g., HCO3(-), Cl(-) and humic acid, and the toxicity of transformation products were evaluated. The results indicated that the oxidation of DCF was well-fitted with a pseudo-first-order kinetic model, and the rate constants increased with the elevated temperatures. The rate constants from 50-70 °C were further fitted to the Arrhenius equation, yielding an activation energy of 157.63 kJ·mol(-1). In addition, the oxidation of DCF was highly pH-dependent, with the rate constants rapidly decreased from pH 5 to 7, then slightly increased at the alkaline pH. The presence of a low dosage of Cl(-)(0-10 mM) promoted the degradation of DCF, whereas high Cl(-) addition (>10 mM) inhibited DCF degradation. HCO3(-) exhibited a negligible effect on DCF removal, while natural organic matters, e.g., humic acids, lightly inhibited DCF degradation. The rapid degradation of DCF was also confirmed in the real groundwater sample, which might be attributed to the pH drop during the reaction. Moreover, the radical quenching experiments revealed that sulfate radicals (SO4·-)) was the dominant reactive species for DCF oxidation. Finally, the acute toxicity of the DCF solution, as tested with a bioluminescent assay, was gradually decreased during the reaction, indicating that a thermally activated PS oxidation was a promising alternative approach for DCF-contaminated groundwater remediation.

Binding between Saikosaponin C and Human Serum Albumin by Fluorescence Spectroscopy and Molecular Docking

Saikosaponin C (SSC) is one of the major active constituents of dried Radix bupleuri root (Chaihu in Chinese) that has been widely used in China to treat a variety of conditions, such as liver disease, for many centuries. The binding of SSC to human serum albumin (HSA) was explored by fluorescence, circular dichroism (CD), UV-vis spectrophotometry, and molecular docking to understand both the pharmacology and the basis of the clinical use of SSC/Chaihu. SSC produced a concentration-dependent quenching effect on the intrinsic fluorescence of HSA, accompanied by a blue shift in the fluorescence spectra. The Stern-Volmer equation showed that this quenching was dominated by static quenching. The binding constant of SSC with HSA was 3.72 × 10³ and 2.99 × 10³ L·mol(-1) at 26 °C and 36 °C, respectively, with a single binding site on each SSC and HSA molecule. Site competitive experiments demonstrated that SSC bound to site I (subdomain IIA) and site II (subdomain IIIA) in HSA. Analysis of thermodynamic parameters indicated that hydrogen bonding and van der Waals forces were mostly responsible for SSC-HSA association. The energy transfer efficiency and binding distance between SSC and HSA was calculated to be 0.23 J and 2.61 nm at 26 °C, respectively. Synchronous fluorescence and CD measurements indicated that SSC affected HSA conformation in the SSC-HSA complex. Molecular docking supported the experimental findings in conformational changes, binding sites and binding forces, and revealed binding of SSC at the interface between subdomains IIA-IIB.

Interactions of 1-hydroxypyrene with bovine serum albumin: insights from multi-spectroscopy, docking and molecular dynamics simulation methods

Combining multi-spectroscopy, docking with MD simulations, the interactions of 1-hydroxypyrene with BSA and the adverse effects on BSA were investigated.

Intercalation of the daphnetin–Cu(ii) complex with calf thymus DNA

The daphnetin–Cu(ii) complex binds to the A–T bases region of ctDNA and causes cleavage of plasmid DNA.