Abstract: In this paper,the noncovalent interactions between α₁-acid glycoprotein(AAG) and the drugs,such as ketoprofen(KP) and anisodine hydrobromide(AN) were studied by using electrospray ion trap mass spectrometry method.The results show that both of the drugs had a strong coalescent interaction with AAG,the(dissociation) constants(K_d) and the apparent stoichiometric ratio of noncovalent complexes AN-AAG were(1.75×10^-3 mol/L) and 1∶7,and those for KP-AAG complex were 4.95×10^-4 mol/L and 1∶4,respectively.According to the thermodynamic parameters of the noncoralent complexes,the main sorts of binding force were static-electricity gravitation for KP-AAG and Van der Waals force for AN-AAG,respectively. The experiment proves that ESI-MS technology as a new method for studying the drug-protein noncoralent binding can offer some advantages in sensitivity,speed,accuracy and directness particularly in the determination of the stoichiormetry of the complex compared to other well-established methods such as circular dichroism and fluorescence spectroscopy,etc.

Key words: Electrospray ion trap mass spectrometry(ESI-MS), α1-Acid glycoprotein, Ketoprofen, Anisodine hydrobromide