Studies On The Interaction Of Melatonin With Some Supramolecular Subjects

Supramolecular chemistry is a new branch of chemistry developed from the late 1960 s and early 1970 s, in which the supramolecular involving the metal cation ligand developed in the earliest time. The study of supramolecular with a cavity structure was developed broadly until the synthesis of the cryptands in the late 1960 s. One of the hotspots is to build cavity structure subjects,such as crown ether, cyclodextrins, cucurbituril and calixarenes.The introduction of numerous functional groups of these host molecules may be conducive to improve some of their characteristics and form new functional supramolecular structures,and further be mainly used in the fields of molecular recognition,self-assembly, molecular interactions and sensors areas. This papar studies on the interactions of several different supramolecular host and Melatonin molecules, basing on the supramolecular chemistry, instrumental analysis and thermal chemical kinetics, such as the use of fluorescen spectrophotometry,nuclear magnetic resonance spectroscopy and molecular modeling for the horizontal and longitudinal comparatively study of melatonin in medicine, to explore the method of preparation of fluorescent probes in the supramolecular sensor as the host. The methodscombine nuclear magnetic resonance spectroscopy with molecular modeling provide determination methods and theoretical basis for the application of melatonin in the molecule drug science. This thesis focuses on following parts:1.Introduction to the history of the development of supramolecular chemistry, and then the second, third and fourth generation development together with synthesis of supramolecular and its derivatives are described. An overview of the molecular recognition, self-assembly and sensor application these compounds has been represented. According to the main similarities and differences of these supramolecular structure, we present the main research content of this paper.2.We determined the interactions of between p-sulfonated calix[n]arenes(SCn As, n=4, 6, 8) the hosts and the guest molecule melatonin by spectroscopic methods. The reaction conditions are discussed from the view of p H and temperature for the appropriate host-guest molecular interactions, which confirmed the main leading factors such as electrostatic interactions, hydrogen bonding and cavity matching effect. Experimental results show that the binding constants of the host-guest molecule are different at different p H of buffer solution and different temperatures upon the addition of SCn A(n=4, 6, 8), the binding constants are different,when the value of n in the p-sulfonated calix[n]arenes(SCn As, n=4,6, 8) is different, and the binding constants increase with the increasing of the value of n, that is SC8A> SC6A> SC4 A. This provides a methods comparison of horizontal and longitudina for the interactions between supramolecular and drug molecules, whichproved the effects of the host molecule on the melatonin molecular matching effect in the body cavity. The result is that the interaction will be stronger when the size of the cavity is larger. In addition, we discussed the molecular selective recognition sites of action in terms of the host molecular cavity and melatonin molecular structure with the1 H NMR and density functional theory(DFT) in verification the mechanism of the host-guest interaction.3.This part studies different interaction for different types of subject supramolecule and object melatonin molecule and similar cavity sizes using spectrofluorimetry and1 H NMR spectroscopy methods and compared the action mechanism in horizontal level.First, the optimum p H value and temperature, as well as the optimal inclusion scale value of several object supramolecules and object melatonin molecule to form inclusion complexes was found by fluorescence titration. The experiment shows that the binding constant of three different types of body supramolecule such as p-sulfonated calix[6]arene(SC6A), cucurbit[7]uril(CB[7]), β-cyclodextrin(β-CD) and guest molecules is maximized with a p H of 7.4 and the temperature of 298 K. Although the cavity sizes of body molecular are similar, the binding constants are different, and the binding constant size accord with relationship: SC6A> β-CD> CB[7].The interaction mechanism was validated by the analysis of1 HNMR and density functional theory calculations proved that the interaction between melatonin and SC6 A is because the steric hindrance of the sulfonic acid group and hydrogen bonding. The interaction between the host molecule and the guest molecules exists only in the external cavity of SC6 A, and the hydrogen bond isformed; The melatonin get into the hydrophobic cavity of β-CD, and formed the MLT-β-CD inclusion complex with a package ratio of 1:1due to the hydrogen bonds and the electrostatic effect with the hydrophobic interactions inside the cavity, and established a molecular model of host-guest inclusion complexes. Fluorescence quenching phenomenon did not occur between supramolecular CB[7]and MLT, indicating that there is no interaction between them.4.We established novel fluorescent sensors which set the supramolecular as the subject, according to the applications of supramolecular in molecular recognition. We explored the research of chitosan film and PVC film modified to the main host molecules CB[6]. The specific conditions of thin film sensors prepared were studied, comparing the film sensor film laying method use different physical, which are applied to the fluorescence determination of Palmatine. The results show that the use of chitosan as a substrate for film laying is better than that of PVC, and the production process of making thin film sensors is simple, which provided a research foundation for the supramolecular sensor of the cucurbituril.