Study On The Noncovalent Complexes Of Hosts And Guests By Electrospray Ionization Mass Spectrometry

Molecule or atom can be ionized with external energy and transformed totally or partially into ions. These ions are arranged according to the ratio of mass to charge to form the graph which is mass spectrum. Mass spectrum can provide information of the chemical structure, accurate molecular weight and the content of analyte. Due to many advantages over other techniques, such as high accuracy, sensitivity and rapid speed, mass spectrometry has become one of the most widely used analytical techniques. In this thesis, the generation and development of the technique, mass spectrometer and electrospray ionization technology are described. The noncovalent interaction and the application of electrospray ionization mass spectrometry in this field are introduced. In this thesis, by using electrospray ionization mass spectrometry, the noncovalent complexes between hosts and guests were studied. A simple and fast method of calculating the dissociation constants of noncovalent complexes was presented.The noncovalent complexes of hosts,α- andβ-CD, and four kinds of sulphonated azo dyes were studied by electrospray ionization mass spectrometry. The results showed that the complexes of CD and dyes can be observed. According to the method proposed in this thesis, the dissociation constants were obtained for one guest system and two guests system. The results are in accord with those obtained by curve-fitting. The stability of the complexes was discussed based on the molecular structure. The calculated dissociation constants show the increasing trend with the guest concentration. The reason may be that the inadequate ionization. The aggregation of the guests and the non-specificity binding may occur when the concentration of the guest is too high.The noncovalent complexes of hosts,α- andβ-CD, and four kinds of guests, fenbufen, aspirin, tetracycline hydrochloride and norfloxacin were studied. The stoichiometric relation can be observed from the mass spectra and the dissociation constants of complexes were obtained. By electrospray ionization mass spectrometry, the dissociation constant of 1:1 noncovalent complex ofβ-CD and osthole was also obtained, which is consistent with the result obtained by fluorescence spectrometry.The noncovalent complexes of cytochrome C and seven kinds of ginsenosides were studied by electrospray ionization mass spectrometry. Ginsenosides are bound to cytochrome C to form several kinds of complexes with different stoichiometric ratio. The dissociation constants are obtained according to the intensities of cytochrome C and complexes when the initial concentrations of cytochrome C and ginsenoside have been known. Competition experiment was performed to validate the results. The KD values obtained with different reaction systems were consistent with each other.The noncovalent complexes of ginsenoside-amino acid were studied by electrospray ionization mass spectrometry. The results indicate that eleven kinds of those amino acids can interact with six kinds of ginsenosides to form the 1:1 non-covalent complexes in both positive ion mode and negative mode. The eleven kinds of amino acids can form 1:1 and 1:2 noncovalent complexes with ginsenoside Rc. The tandem mass spectrometric analysis was performed and the fragment ions were amino acids or ginsenosides. The dissociation constants of complexes between ginsenosides and amino acids are obtained according to the intensities of ginsenosides and complexes in mass spectra and the total concentrations of ginsenosides and amino acids.