Understanding the binding of quinoline amines with human serum albumin by spectroscopic and induced fit docking methods

Investigation of steric hindrance effect on the interactions between four alkaloids and HSA by isothermal titration calorimetry and molecular docking

The binding of four alkaloids with human serum albumin (HSA) was investigated by isothermal titration calorimetry (ITC), spectroscopy and molecular docking techniques. The findings demonstrated that theophylline or caffeine can bind to HAS, respectively. The number of binding sites and binding constants are obtained. The binding mode is a static quenching process. The effects of steric hindrance, temperature, salt concentration and buffer solution on the binding indicated that theophylline and HSA have higher binding affinity than caffeine. The fluorescence and ITC results showed that the interaction between HSA and theophylline or caffeine is an entropy-driven spontaneous exothermic process. The hydrophobic force was the primary driving factor. The experimental results were consistent with the molecular docking data. Based on the molecular structures of the four alkaloids, steric hindrance might be a major factor in the binding between HSA and these four alkaloids. This study elucidates the mechanism of interactions between four alkaloids and HSA.

Hybridized 4-Trifluoromethyl-(1,2,3-triazol-1-yl)quinoline System: Synthesis, Photophysics, Selective DNA/HSA Bio-interactions and Molecular Docking

The synthesis, structural analysis, and evaluation of the photophysical properties of twelve novel 2-aryl(heteroaryl)-6-(4-alkyl(aryl)-1H-1,2,3-triazol-1-yl)-4-(trifluoromethyl)quinolines (6-8), where aryl(heteroaryl)=Ph, 4-Me-C₆ H₄ , 4-F-C₆ H₄ and 2- furyl; 4-alkyl(aryl)=-CH₂ OH, -(CH₂ )₅ CH₃ and Ph, are reported. Hybrid scaffolds 6-8 were synthesized at 77-95 % yields by regioselective copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction of unpublished 6-azido-4-(trifluoromethyl)quinolines (2) with selected terminal alkynes (3-5). Azido intermediates 2 were obtained from the reaction of 6-amino-4-(trifluoromethyl)quinolines (1) and sodium azide at good yields (78-87 %). Compounds 6-8 were structurally fully characterized by ¹ H-, ¹³ C- and ¹⁹ F- and ¹ H-¹³ C 2D-NMR (HSQC, HMBC) spectroscopy, X-ray diffraction (SC-XRD) and HRMS analysis. Moreover, the photophysical properties, DNA- and HSA-binding experiments (bio-interactions), and molecular docking studies for compounds 6-8 were performed. These are discussed and compared with similar compounds from recent research.

Exploring the interaction between tyrphostin 9 and human serum albumin using biophysical and computational methods

Tyrphostin 9 (Tyr 9) is a potent platelet-derived growth factor receptor (PDGFR) inhibitor, which induces apoptosis in various cancer cell types. The binding of Tyr 9 to the major transport protein, human serum albumin (HSA) was investigated using several spectroscopic techniques and molecular docking method. Fluorescence quenching titration results showed progressive decrease in the protein fluorescence with increasing drug concentrations. A decreasing trend of the Stern-Volmer constant, K _sv with increasing temperature characterized the drug-induced quenching as static quenching, thus pointed towards the formation of Tyr 9-HSA complex. The binding constant of Tyr 9-HSA interaction was found to lie within the range 3.48-1.69 × 10⁵ M^-1 at three different temperatures, i.e. 15 °C, 25 °C and 35 °C, respectively and suggested intermediate binding affinity between Tyr 9 and HSA. The drug-HSA complex seems to be stabilized by hydrophobic forces, van der Waals forces and hydrogen bonds, as suggested from the thermodynamic data as well as molecular docking results. The far-UV and the near-UV CD spectral results showed slight alteration in the secondary and tertiary structures, respectively, of the protein upon Tyr 9 binding. Interaction of Tyr 9 with HSA also produced microenvironmental perturbations around protein fluorophores, as evident from the three-dimensional fluorescence spectral results but increased protein's thermal stability. Both competitive drug binding results and molecular docking analysis suggested Sudlow's Site I of HSA as the preferred Tyr 9 binding site. Communicated by Ramaswamy H. Sarma.