Determination of dissociation constants of cyclodextrin-ligand inclusion complexes by electrospray ionization mass spectrometry.
The inclusion complexes of four ligands binding to cyclodextrins (CDs) were studied by electrospray ionization mass spectrometry (ESI-MS) and the dissociation constants of the complexes were obtained. The 1:1 stoichiometric inclusion complex was found in the system of CD and fenbufen or aspirin. The obtained KD values of the inclusion complexes of fenbufen binding to alpha-CD and to beta-CD are 4.38x10(-4) mol L(-1) and 2.12x10(-4) mol L(-1), respectively. The KD values of the inclusion complexes of alpha-CD-aspirin and beta-CD-aspirin are 3.33x10(-4) mol L(-1) and 1.83x10(-4) mol L(-1), respectively. A non-linear least squares regression method was applied to validate the results which were consistent with each other. For the system of tetracycline hydrochloride and CD, the 1:1 and 1:2 stoichiometric inclusion complexes were found in the mass spectra. The KD,1 and KD,2 values of the 1:1 and 1:2 stoichiometric inclusion complexes of alpha-CD and tetracycline hydrochloride are 4.47x10(-4) mol L(-1) and 6.51x10(-4) mol L(-1), respectively, and those of beta-CD and tetracycline hydrochloride are 2.26x10(-4) mol L(-1) and 8.57x10(-4) mol L(-1), respectively. For the system of norfloxacin and CD, besides the 1:1 and 1:2 inclusion complexes, the 1:3 stoichiometric inclusion complex was also found. The KD,1, KD,2 and KD,3 of alpha-CD and norfloxacin inclusion complexes are 4.61x10(-4) mol L(-1), 6.05x10(-4) mol L(-1) and 1.45x10(-3) mol L(-1), respectively. The three KD values of beta-CD and norfloxacin are 1.96x10(-4) mol L(-1), 4.93x10(-4) mol L(-1) and 1.15x10(-3) mol L(-1), respectively.
Zhang
Huarong
H
College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China.
Zhang
Hanqi
H
Jin
Weiqun
W
Ding
Lan
L
D001241:Aspirin / Q000737:chemistry; D001665:Binding Sites; D003505:Cyclodextrins / Q000737:chemistry*; D008024:Ligands; D009643:Norfloxacin / Q000737:chemistry; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D010654:Phenylbutyrates / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013752:Tetracycline / Q000737:chemistry; D013816:Thermodynamics
D003505:Cyclodextrins; D008024:Ligands; D004364:Pharmaceutical Preparations; D010654:Phenylbutyrates; C010725:fenbufen; D013752:Tetracycline; D009643:Norfloxacin; D001241:Aspirin