Estudo espectroscópico da interação entre derivados de 1,2-naftoquinonas e albumina sérica humana (ASH)

Abstract

The interaction between human serum albumin and derivatives 1,2-naphtoquinones in buffered solution was studied by UV - Visible, circular dichroism spectroscopy, fluorescence emission spectroscopy and fluorescence emission spectroscopy with temporal resolution. The results obtained for the rate constants of fluorescence quenching of HSA [Kq = 1012 L . (mol.s)-1] and fluorescence lifetime τ2 (≈ 6.6 ns ) suggest a static mechanism for the quenching process . Thermodynamic values for Gibbs energy free found for the interaction between 1,2-naphtoquinones and ASH (≈ -24 to -29 kJ . mol-1) suggest the occurrence of a spontaneous process via reversible mechanism. Already positive and negative values of ∆Ho and ∆So found in all cases (-6.60 to -21.82 kJ/mol and a +64.61 to 10.79 J/mol.K), respectively , indicating that the interaction occurs by formation of a hydrogen bond at room hydrophobic . Studies about distances of the rays of Foster, r, between donor and acceptor (≈ 2-3 nm), indicates a strong interaction between 1,2-naphthoquinone and ASH, which is independent of temperature. The decrease in the percentage of α-helix verified in studies of circular dichroism (53 to 60%) indicating the interaction between HSA with 1,2-naphthoquinonas which may reflect the conformational change of the protein to better accommodate the compounds in the hydrophobic cavity serum albumin near the tryptophan residue.