Binding of caffeine, theophylline, and theobromine with human serum albumin: A spectroscopic study

The interaction between three purine alkaloids (caffeine. theophylline, and theobromine) and human serum albumin (HSA) was investigated using UV/vis absorption, circular dichroism (CD), fluorescence, synchronous fluorescence. and three-dimensional fluorescence spectra techniques The results revealed that three alkaloids caused the fluorescence quenching of HSA by the formation of alkaloid-HSA complex The binding site number it and apparent binding constant K-A, corresponding thermodynamic parameters the free energy change (Delta G). enthalpy change (Delta H), and entropy change (Delta S) at different temperatures were calculated. The hydrophobic interaction plays a major role in stabilizing the complex The distance r between donor (HSA) and acceptor (alkaloids) was obtained according to fluorescence resonance energy transfer. The effect of alkaloids on the conformation of HSA was analyzed using circular dichroism (CD), UV/vis absorption. synchronous fluorescence and three-dimensional fluorescence spectra techniques (C) 2009 Elsevier B V. All rights reserved