Spectroscopic and Molecular Docking Studies on the Interaction of Dimetridazole With Human Serum Albumin

Abstract

Dimetridazole (DMZ) is widely used for the therapeutic treatment of farmed animals and is suspected of being human carcinogens and mutagens. The interaction between DMZ and human serum albumin (HSA) was investigated systematically by fluorescence spectroscopy, synchronous fluorescence, threedimensional fluorescence, CD spectroscopy, UV-vis absorption spectroscopy and molecular docking study. The results indicated that the probable quenching mechanism of HSA by DMZ was dynamic quenching. The corresponding thermodynamic parameters ΔH, ΔS and ΔG were calculated according to Van't Hoff equation. The results (ΔH = 65.10 kJ mol -1 and ΔS = 295.65 J mol -1 K -1 ) indicated that the driving force between DMZ and HSA was mainly typical hydrophobic interaction. The conformation changes in the interaction were studied by synchronous fluorescence, CD spectroscopy and three-dimensional fluorescence spectra. The results revealed that the microenvironment and conformation of HSA has been changed. Molecular modeling study further confirmed the binding mode obtained by experimental study.

Synthesis and Biophysical Insights into the Binding of a Potent Anti-Proliferative Non-symmetric Bis-isatin Derivative with Bovine Serum Albumin: Spectroscopic and Molecular Docking Approaches

“…Several earlier studies have utilized spectroscopic techniques, particularly fluorescence spectral determination, to explore the different aspects of protein binding to various ligands [34][35][36]. Fluorescence quenching shows decline protein intrinsic fluorescence occurring through diverse molecular interactions [37,38]. The BSA fluorescence emission spectra with and without the addition of compound 3 were monitored in the wavelength range 290-500 nm upon excitation at 280 nm.…”

“…Therefore, in order to comprehensively elaborate the BSA binding sites for the compound 3 interaction, the BSA binding to possesses different fluorescence peaks, where peak 1 (λex 224 → λem 336) is controversial as numerous previous studies have claimed that it originated from the n → π* transition of the polypeptide backbone of the serum albumin structure, correlating its intensity to the BSA or HAS (Human Albumin Serum) secondary structures [38,52]. Conversely, in a latest multi-laboratory investigation reported by Bortolotti et al [53], it was established that this observed emission peak, following the excitation at 220-230 nm, aroused from Tyr and/or Trp.…”

Insight into the fluorescence quenching of Trp214 at HSA by the Dimetridazole ligand from simulation

“…In the case of the Dmz ligand, the long wavelength absorption band was reported to fully overlap with the fluorescence band of tryptophan [19]. In the MD simulations, the Dmz ligand trapped by HSA is moving within the subdomain IIA, but never very away from the Trp214 chromophore fragment and close enough to provide MO overlap and allow for - stacking of the ligand with the chromophore (Fig 11).…”

“…Tyr and the less intense La bands of Trp mainly contribute to the spectral region between 240-280 nm [16,17]. In contrast, the fluorescence maximum is due only to UV-excited Trp [18][19][20], but varies between 307 and 370 nm and in some cases even longer wavelengths depending on the microenvironment. In particular, the single Trp214 chromophore side residue is solely responsible for the longwavelength wing of the HSA (Trp214@HSA) spectrum starting from 300 nm (Figures 2 and 3) [19,21].…”

“…It has been reported that a dimetridazole (Dmz; C5H7N3O2, 1,2-dimethyl-5-nitroimidazole) embedded in this pocket leads to a quenching of the strong HSA fluorescence in the wavelength region λem=342345 nm ( Fig. 3) due to excited-state energy transfer from the chromophore center to Dmz [19]. This complex can thus serve as a model system for studying the CT between spatially close, non-bonded fragments of a complex trapped in the tight space of HSA.…”