Molecular Modeling and Spectroscopic Studies on the Interaction between Phentolamine Mesylate and Myoglobin

The molecular interaction mechanism of phentolamine mesylate (PM) with myoglobin (Mb) was investigated by UV absorption and fluorescence spectra in combination with molecular modeling under the simulated physiological conditions. The results revealed that the binding site number and apparent binding constant were 1 and 5.27 x 10(4) L.mol(-1) respectively. Furthermore, molecular modeling results indicated that PM could bind to the site 1 of Mb. Hydrophobic interaction, hydrophilic interaction, hydrogen bond formation and electrostatic interaction could account for the binding of PM. The hydrophobic interactions between the PM and Trp, Tyr, Phe of Mb lead to decrease of UV absorption and fluorescence quenching. Negative value of Delta G(Theta) shows that the binding reaction is thermodynamically favorable.