Investigation the interaction of Daphnin with human serum albumin using optical spectroscopy and molecular modeling methods

Structural and biological characterization of anticancer nickel(II) bis(benzimidazole) complex

In the present study, nickel(II) complex with 2-[2-[2-(1H-benzimidazol-2-yl)ethylsulfanyl]ethyl]-1H-benzimidazole (tebb) of formula [Ni(tebb)₂](ClO₄)₂ has been prepared and its structure was proved by X-ray crystallography. The central nickel atom is in deformed octahedral vicinity. Four nitrogen atoms of two ligands form plane of octahedral and sulfur atoms are in apical positions. Perchlorate anions are outside the coordination sphere. The coordination compound was tested for its biological activities in an array of in vitro assays. It was found that the synthesized complex possesses interesting biological activity, which is most likely related to its cell-type related uptake kinetics. The synthesized complex is readily uptaken by malignant MDA-MB-231 and CACO-2 cells with the lowest uptake by healthy Hs27 fibroblasts. The lowest IC₅₀ values were obtained for MDA-MB-231 cells (5.2-12.7 μM), highlighting exceptional differential cytotoxicity (IC₅₀ values for healthy fibroblasts were 38.6-51.5 μM). Furthermore, it was found the complex is capable to cause hydrolytic DNA cleavage, promotes an efficient DNA fragmentation and to trigger an extensive formation of intracellular reactive oxygen species. Overall, current work presents a synthesis of Ni(II) coordination compound with interesting biological behavior and with a promising potential to be further tested in pre-clinical models.

Investigation of the interaction of 2,4-dimethoxy-6,7-dihydroxyphenanthrene with α-glucosidase using inhibition kinetics, CD, FT-IR and molecular docking methods

Applying enzyme kinetics, spectroscopic, and molecular docking methods, the interaction properties of 2,4-dimethoxy-6,7-dihydroxyphenanthrene with α-glucosidase were systematically investigated. The α-glucosidase inhibitory activities (IC₅₀ = 0.40 mM) were significantly higher than that of acarbose (as control) and the spectrometric results revealed that 2,4-dimethoxy-6,7-dihydroxyphenanthrene inhibited α-glucosidase in a reversible and noncompetitive manner, which is that the inhibitor bind to the inactive region of α-glucosidase and could be separated from the bind sites. Hydrogen bond was the key interaction force obtained from the results of the molecular docking study, and the binding energy was -27.754 kJ/mol. The CD studies showed that the content of α-helix in α-glucosidase increased from 17.2% to 17.8% with the concentration varying of 2,4-dimethoxy-6,7-dihydroxyphenanthrene. The α-helix increasing trend (19.70% - 21.43%) of α-glucosidase secondary structure was further proved by Fourier transform infrared spectra (FT-IR) results and the FT-IR spectra of α-glucosidase resulted in obvious red shift with the addition of 2,4-dimethoxy-6,7-dihydroxyphenanthrene. All the measurements proved the interaction of 2,4-dimethoxy-6,7-dihydroxyphenanthrene with α-glucosidase and revealed the conformational change of α-glucosidase secondary structure.

Novel half-sandwich iridium(iii) imino-pyridyl complexes showing remarkable in vitro anticancer activity

Seven novel half-sandwich Ir^III cyclopentadienyl complexes, [(η⁵-Cp^x)Ir(N^N)Cl]PF₆, have been prepared and characterized, where Cp^x is Cp* or the biphenyl derivative Cp^xbiph (C₅Me₄C₆H₄C₆H₅), and the N^N-chelating ligands are imino-pyridyl Schiff-bases. The X-ray crystal structures of complexes 2A, 2B, and 3A have been determined. Excitingly, most of the complexes show potent antiproliferative activity towards A549 and HeLa cancer cells, except for Cp* complex 1A towards HeLa cells. Cp^xbiph complex 2B displayed the highest potency, about 19 and 6 times more active than the clinically used drug cisplatin toward A549 and HeLa cells, respectively. These complexes undergo hydrolysis, and the kinetics data have been calculated. DNA binding has been studied by interaction with nucleobases 9-ethylguanine and 9-methyladenine, cleavage of plasmid DNA, and interaction with ctDNA. Interaction with DNA does not appear to be the major mechanism of action. Protein binding (bovine serum albumin, BSA) has been established by UV-Vis, fluorescence and synchronous spectroscopic studies. The stability of complex 2B in the presence of GSH was evaluated. The complexes catalytically convert coenzyme NADH to NAD⁺via hydride transfer. Cp^xbiph complexes 2B and 4B induce cell apoptosis and arrest cell cycles at the S and G₂/M phases towards A549 cancer cells and increase the reactive oxygen species dramatically, which appear to contribute to the remarkable anticancer activity.

Lysosome targeted drugs: rhodamine B modified N^N-chelating ligands for half-sandwich iridium(iii) anticancer complexes

We designed and synthesized four rhodamine-modified half-sandwich iridium complexes ([(η⁵-Cp^x)Ir(N^N)Cl]PF₆).

Probing the binding properties of dicyandiamide with pepsin by spectroscopy and docking methods

Dicyandiamide (DCD), considered to be a nitrification inhibitor, poses threat to human's health with exposure from milk, infant formula and other food products. In this work, DCD was investigated for its binding reaction with pepsin using spectroscopy and docking methods. Fluorescence experiments indicated DCD quenched the fluorescence of pepsin through a static process. Thermodynamic analysis of the binding data (ΔH⁰ = -21.72 kJ mol^-1 and ΔS⁰ = 17.61 J mol^-1 K^-1) suggested the involvement of hydrophobic and hydrogen bonding in the complex formation. The pepsin interacted with DCD at a hydrophobic cavity, leading to a conformational changes in the pepsin, as revealed from UV-vis absorption, Fourier transform infrared, the time-resolved fluorescence, three-dimensional fluorescence and circular dichroism spectral results.

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.

Investigation of the interaction of batatasin derivatives with human serum albumin using voltammetric and spectroscopic methods

The binding properties of batatasin derivatives with HSA were estimated by voltammetric, spectroscopic, and molecular docking methods. There were non-electroactive complexes formed between them. And the α-helix structure in HSA was reduced.

Interaction mechanisms between organic UV filters and bovine serum albumin as determined by comprehensive spectroscopy exploration and molecular docking

Organic UV filters are a group of emerging PPCP (pharmaceuticals and personal care products) contaminants. Current information is insufficient to understand the in vivo processes and health risks of organic UV filters in humans. The interaction mechanism of UV filters with serum albumin provides critical information for the health risk assessment of these active ingredients in sunscreen products. This study investigates the interaction mechanisms of five commonly used UV filters (2-hydroxy-4-methoxybenzophenone, BP-3; 2-ethylhexyl 4-methoxycinnamate, EHMC; 4-methylbenzylidene camphor, 4-MBC; methoxydibenzoylmethane, BDM; homosalate, HMS) with bovine serum albumin (BSA) by spectroscopic measurements of fluorescence, circular dichroism (CD), competitive binding experiments and molecular docking. Our results indicated that the fluorescence of BSA was quenched by these UV filters through a static quenching mechanism. The values of the binding constant (Ka) ranged from (0.78±0.02)×10(3) to (1.29±0.01)×10(5) L mol(-1). Further exploration by synchronous fluorescence and CD showed that the conformation of BSA was demonstrably changed in the presence of these organic UV filters. It was confirmed that the UV filters can disrupt the α-helical stability of BSA. Moreover, the results of molecular docking revealed that the UV filter molecule is located in site II (sub-domain IIIA) of BSA, which was further confirmed by the results of competitive binding experiments. In addition, binding occurred mainly through hydrogen bonding and hydrophobic interaction. This study raises critical concerns regarding the transportation, distribution and toxicity effects of organic UV filters in human body.

Spectroscopic and molecular modeling studies on the interactions of N-Methylformamide with superoxide dismutase

N-Methylformamide, a polar solvent has a wide industrial applications and it is well-known for hepatotoxicity. The interaction between NMF with superoxide dismutase, an antioxidant defense enzyme has been studied for the first time using spectroscopic methods including Fourier transform infrared (FT-IR) spectroscopy, Circular dichroism (CD) spectroscopy and UV-visible spectroscopy under simulative physiological conditions and also by molecular modelling. Fourier Transform Infra Red analysis showed that the change in peak positions and shapes revealed that the secondary structure of SOD had been changed by the interaction with NMF. The data of CD spectra also confirmed that NMF decreased the degree of secondary structure of SOD, which directly resulted in destabilization of enzyme. We studied the inhibitory effect of NMF on enzyme kinetics by pyrogallol autoxidation revealed that protein-ligand complex caused structural unfolding which resulted in enzymatic inhibition. Thus the spectral behaviour of superoxide dismutase provides data concerning its conformational changes in the presence of NMF. Furthermore, molecular docking was applied to explore the binding mode between the protein-ligand complex. This suggested that Asn54 and Val302 residues of dimeric protein were predicted to interact with NMF. The present study provides direct evidence at a molecular level to show that exposure to NMF cause perturbation in its structure and function.