Bio-related Substances In The Main - The Study Of Object Recognition, Supramolecular Chemistry, Molecular Spectroscopy And Its Analytical Applications

Host compounds have high molecular recognition ability towards guest molecules and their applications open up broad prospects for developing the specific > exclusive and highly selective methods to analyze bio-pertinent molecules. In recent years, the applications of new host compounds, such as prophyrin> crown ether > cyclodextrin(CD) and calixarence, on the recognition and analysis of bio-pertinent substances have gradually become the focal point of the present research work. Cyclodextrins have the hydrophobic cavity and hydrophilic wall. They are well known to have the property of forming inclusion complex with organic and inorganic molecules which possess suitable polarity and dimension. So, as the excellent enzyme model and molecule receptor, cyclodextrins have been widely used in a good many of fields in science and technology. The formation of supramolecular complex with P-CD can alter the photochemical and photophysical properties of the guest molecules and considerable attentions have been focused on the luminescence application of the cyclodextrins.At present, the determinations of active components in plants or animals and exoteric bioactive substances梔rugs almost entirely use organic solvents as medium under the limit of some factors in aqueous solution such as poor solubility, small fluorescence quantum yield and so on. Most of these analytical methods needed expensive instrumentation, required strictly controlled reaction conditions, involved some time-consuming and troublesome steps and what's more important, they were less sensitive. So, for routine quality control, the development of some simple, rapid, selective and sensitive spectrofluorimetric or spectrophotometric methods for the determinations of bio-pertinent molecules in aqueous phase is highly desirable. The low fluorescence quantum yield or small molar absorption coefficient of the analysed substances in aqueous solution precludes their trace amount determination. So, the remarkable enhancement of the fluorescence emission or absorbance of the bio-pertinent substances due to their complexations with (3-CD might be very useful from an analytical point of view.Based on the changes in the spectrum characters of guest molecules producedthrough inclusion complex formation with cyclodextrins, we have carried out two aspects of investigation:First, the mechanisms for the host-guest recognition reactions have been studied, such as the interactions between 3-CD and curcumin, the main constituent of the rhizomes of the plant Curcuma longa, the recognition of p-CD towards rubidate, the effective component of the Chinese traditional medicine madder, and the reactions of p-CD towards the antileprotic drug dapsone and the antiinflammatory drug nabumetone: The formation of supramolecular complex between P-CD and guest molecule has been discussed and verified in virtue of multitudinous means such asultraviolet-visible absorption, fluorescence emission, infrared spectrogram and so on. The influence of addition of linear alcohols on the supramolecular system has been studied and the reason why the noncovalent interactions in the three-component system could result in a decrease in the apparent association constant of the inclusion complex has been revealed. Inclusion complex thermodynamics has also been investigated. The changing trends of the thermodynamic parameters have been researched and the inclusion processes of (3-CD towards curcumin and rubidate have been examined from an enthalpy-entropy compensation effect point of view. The essential reason for the sensitization induced by (3-CD towards guest fluorescence has been further illuminated through fluorescence quenching experiments. All these studies provide new theories and researching methods for the supramolecular chemistry.Second, the new methods with high sensitivity for the determination ofbio-pertinent molecules in bulk aqueous solution have been established based on the significant enhancement in the absorbance or fluorescence intensi...