The Characteristics Of Noncovalent Bonds Formed By Bioactive Containing Disulfide Or Aromatic Ring

Noncovalent bond plays an important role in biochemistry.Using experimental method to analyze the formation of noncovalent interaction is meaningful for understanding their stabilization in protein,and also for revealing ligand bound to acceptor protein.There are many kinds of noncovalent bonds in nature with complicated behaviors.Therefore,many noncovalent bonds have not been unambiguously understood and summarized,and even some noncovalent bonds have never been verified by experiments.In this paper,three kinds of bioactive molecules containing thioethers,fluorinated aromatic rings and 2,3-benzofuran were studied by Fourier transform microwave spectroscopy combined with quantum chemistry calculation.The main studied contents are as follows:The first chapter introduces history of noncovalent bond from ambiguous understanding to definition various noncovalent bonds.Physiological processes are driven by various supramolecules that their structure are determined by noncovalent bonds.The second chapter introduces principle of rotational spectroscopy for determining molecular structure.Then,the measured method is also introduced.Disulfide bond is a significant unit of proteins response for protein folding and stability.However,the spectroscopy experimental study of noncovalent interaction involved disulfide bond is still blank.The conformers of methyl allyl disulfide and diethyl disulfide complexes are studied by Fourier transform microwave spectroscopy(3th chapter).The geometries of two observed conformers indicate that there are intramolecular noncovalent interactions involving the intramolecular CH···? and S···?interactions.The noncovalent interactions of methyl allyl disulfide···water 1:1 cluster and diethyl disulfide···water/formaldehyde/formamide 1:1 cluster are also determined.The results show that the interaction of disulfide bonds with these molecules bound by XH···S(X=O,C,N)hydrogen bonds in gas phase.The experimental rotational constants of diethyl disulfide···water,formaldehyde and formamide clusters also are of the benchmark to evaluate the performance of different theoretical calculations level.Many drug molecules introduce fluorine atoms to increase the affinity and molecular recognition for acceptor proteins,which are dominated by noncovalent interaction.2-trifluoromethylpyridine···water and 1,2,3,4-tetrafluorobenzene···water 1:1 clusters are studied by rotational spectroscopy,respectively.The structures of noncovalent bond of the global minimum isomer is determined(4th chapter).Compared with other fluorinated aromatics···water clusters which have been published in journal,the fluorination impact on pyridine and benzene is summarized.Benzofuran rings is a basic structural unit of many biologically active natural medicines and synthetic chemical raw materials showing broad band of biological activities,they could form various noncovalent interaction with acceptor proteins.The noncovalent interactions in 2,3-benzofuran···water/formaldehyde 1:1 clusters were studied by Fourier transform spectroscopy(5th chapter).Theoretical calculations show that the energies of many isomers of the 2,3-benzofuran···formaldehyde clusters are very close with a variety of noncovalent interaction.However,only the global minimum isomer is observed in 2,3-benzofuran···formaldehyde cluster results of conformational relaxation.The minimum's accurate molecular structure is obtained.On the other hand,two isomers of 2,3-benzofuran···water are observed.Although the two subunits are all bound by hydrogen bond in two isomers,these hydrogen bonds are diverse.