Interaction of the nitrosyl ruthenium complex [Ru^II (NH.NHq‐R)(tpy)NO]³⁺ with human serum albumin: a spectroscopic and computational investigation

Abstract

The interaction between two nitrosyl ruthenium complexes [Ru (NH.NHq–COOH)(tpy)NO](PF6)3 (RuBDQ) and [Ru (NH.NHq–H)(tpy)NO](PF6)3 (RuBD) and human serum albumin (HSA) was investigated using spectroscopic and computational methods. From fluorescence experiments, a dynamic quenching mechanism and binding constants at a single site demonstrated the higher stability of the RuBDQ–HSA system at 308 K compared with RuBD–HSA. Thermodynamic parameters indicated that binding of RuBDQ and RuBD to HSA was mainly driven by hydrophobic interaction and hydrogen bonding, respectively. Synchronous fluorescence and FT‐IR results suggested that interactions between both nitrosyl ruthenium complexes and HSA affected protein conformation. Competition experiments revealed that RuBDQ and RuBD bound to Sudlow sites I and II, respectively. Molecular docking results showed that RuBDQ interacted with Ser‐192 and Ala‐291 residues via hydrogen bonding and polar contact, respectively, whereas RuBD associated with Asn‐391 via a polar interaction. Noncovalent interaction results suggested that van der Waals interactions were the main binding forces for both systems, i.e. RuBDQ associated with Trp‐214 via van der Waals interaction and with Ty‐150 via dipole–dipole bonding, whereas RuBD associated with Tyr‐452 via van der Waals forces. The Asp‐391 residue interacted with the nitrosyl ligand via polar contact and the terpyridine ligand via van der Waals interaction.

Spectroscopic and Molecular Docking Study of the Interaction between Neutral Re(I) Tetrazolate Complexes and Bovine Serum Albumin

“…If a pure static quenching mechanism was occurring, then an increase in temperature would lead to a decrease in stability of the complex [29,39] . In contrast, for a dynamic effect, faster diffusion rates occur at higher temperature, which results in the increase in k q [40] . Analysis of k q for 2 shows that at temperatures between 297–310 K there is no difference in calculated k q values.…”

Structural and Photodynamic Studies on Nitrosylruthenium-Complexed Serum Albumin as a Delivery System for Controlled Nitric Oxide Release

“…The intrinsic fluorescence intensity of HSA can be applied in the fluorescence quenching method to study protein–ligand interaction. − Figure shows the fluorescence spectra of HSA in the presence of various concentrations of the [RuCl 3 (5cqn)­(NO)] − complex (0–50 μM). Static quenching with increasing concentration of the Ru-NO complex was clearly observed.…”

“…Static quenching with increasing concentration of the Ru-NO complex was clearly observed. The binding constant ( K b ) for the static quenching was calculated by using the modified Stern–Volmer equation. − The calculated binding constant ( K b ) for the formation of an adduct between the [RuCl 3 (5cqn)­(NO)] − complex and HSA is 2.3 × 10 4 M –1 , and the binding number ( n ) is 1.02. The value is similar to the reported values for the other nitrosylruthenium complexes and HSA adduct, K b is in the range of 10 3 –10 5 M –1 , and the binding number ( n ) is close to 1. , …”

Biophysicochemical studies of a ruthenium (II) nitrosyl thioether‐thiolate complex binding to BSA: Mechanistic information, molecular docking, and relationship to antibacterial and cytotoxic activities

“…[ 16 ] The primary and secondary structures of albumin have been studied previously. [ 17 ] BSA is one of the most researched proteins, having activities that are critical for the disposition and transportation of a wide range of substances inside the body, including metal ions, medicines, hormones, steroids, and fatty acids. [ 18 ] The structure of bovine serum albumin (BSA) is comparable with that of human serum albumin (HSA), with a 78% similarity in structure, medical care, binding characteristics, ease of availability, and cheap cost.…”