Study of the interaction between 8-azaguanine and bovine serum albumin using optical spectroscopy and molecular modeling methods

J Mol Model. 2012 Feb;18(2):493-500. doi: 10.1007/s00894-011-1069-5. Epub 2011 May 4.


The interaction between 8-azaguanine (8-Azan) and bovine serum albumin (BSA) in Tris-HCl buffer solutions at pH 7.4 was investigated by means of fluorescence and ultraviolet-visible (UV-Vis) spectroscopy. At 298 K and 310 K, at a wavelength of excitation (λ (ex)) of 282 nm, the fluorescence intensity decreased significantly with increasing concentrations of 8-Azan. Fluorescence static quenching was observed for BSA, which was attributed to the formation of a complex between 8-Azan and BSA during the binding reaction. This was illuminated further by the UV-Vis absorption spectra and the decomposition of the fluorescence spectra. The thermodynamic parameters ∆G, ∆H, ∆S were calculated. The results showed that the forces acting between 8-Azan and BSA were typical hydrophobic forces, and that the interaction process was spontaneous. The interaction distance r between 8-Azan and BSA, evaluated according to fluorescence resonance energy transfer theory, suggested that there is a high possibility of energy transfer from BSA to 8-Azan. Theoretical investigations based on homology modeling and molecular docking suggested that binding between 8-Azan and BSA is dominated by hydrophilic forces and hydrogen bonding. The theoretical investigations provided a good structural basis to explain the phenomenon of fluorescence quenching between 8-Azan and BSA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Azaguanine / chemistry*
  • Azaguanine / metabolism
  • Binding Sites
  • Cattle
  • Fluorescence Resonance Energy Transfer / methods
  • Humans
  • Models, Molecular*
  • Protein Binding
  • Protein Structure, Secondary
  • Serum Albumin, Bovine / chemistry*
  • Serum Albumin, Bovine / metabolism
  • Spectrometry, Fluorescence / methods
  • Spectrum Analysis / methods
  • Thermodynamics


  • Serum Albumin, Bovine
  • Azaguanine