Title
Investigation of interaction between human plasmatic albumin and potential fluorinated anti-trypanosomal drugs
Author
Otávio Augusto Chaves, Cosme Henrique Coêlho dos Santos de Oliveira, Romulo Correia Ferreira, Robson Pacheco Pereira, Jorge Luiz R. de Melos, Cláudio E. Rodrigues-Santos, Aurea Echevarria, Dari Cesarin-Sobrinho
Year
2017
Journal
Journal of Fluorine Chemistry
Abstract
In the present work, the interaction between HSA with three potential anti-trypanosomal drugs – (E)-2-benzylidene-hydrazine-carbothioamide (UTS); (E)-2-(3,4-difluoro-benzylidene)-hydrazine-carbothioamide (DFTS) and (E)-2-(2,3,4-trifluoro-benzylidene)-hydrazine-carbothioamide (TFTS) - was studied under physiological conditions by spectroscopic techniques (UV-vis, circular dichroism, steady state, time resolved and synchronous fluorescence) at 296K, 303K and 310K, and theoretical calculations (molecular docking). The bimolecular quenching constant values (kq) were higher than 5.00x109 M−1s−1, suggesting a ground state association between albumin and the ligands (static quenching mechanism). Time-resolved fluorescence measurements confirmed the static quenching mechanism, despite the high probability of Förster resonance energy transfer (FRET) (r ≈ 4.00 nm for TFTS and r ≈ 3.00 nm for UTS and DFTS). Modified Stern-Volmer binding constant values (Ka = 104 M−1), CD results and synchronous fluorescence (Δλ = 15 and 60 nm) indicated moderate association between HSA:UTS, HSA:DFTS and HSA:TFTS, with weak perturbation on the secondary structure of albumin, without perturbation on the microenvironment of the Trp and Tyr residues. The calculated thermodynamic parameters (ΔH°, ΔS° and ΔG°) are in agreement with a spontaneous binding process, both entropically and enthalpically driven with hydrogen bonding and hydrophobic interactions as the main binding forces. Competitive binding experiments indicated site I as the main binding site of the protein for all studied compounds and molecular docking results suggested the same intermolecular interactions indicated by the thermodynamic parameters.© 2017 Elsevier B.V. All rights reserved
Instrument
J-815
Keywords
Circular dichroism, Secondary structure, Ligand binding, Biochemistry, Pharmaceutical