Supramolecular Self-assembly Of Citrullus Ring With Amino Acids, Dipeptides And Peptides

Supramolecular chemistry is the study of two or more molecules that form self-assemblies through a variety of weak interactions,including hydrogen bonding,coordination bonding,van der Waals forces,and other weak interactions.Cucurbituril?Q[n]?is a new class of macrocyclic compounds and is a new member of the macrocyclic family after both crown ethers,cyclodextrins and calixarenes.Its structural features are highly symmetrical,with hydrophobic cavities and polar carbonyl oxygen-modified ports.Because of this feature,cucurbiturils can encapsulate organic molecules of suitable structure and size to form a unique chelating urea host-guest chemistry.As an important component of human body,amino acid,dipeptide and polypeptide molecules are important components of proteins in human body.The hydrophobic cavity of cucurbituril can encapsulate the amino acid dipeptide and the proper position of the polypeptide molecules to form host-guest chemistry.In addition,cucurbiturils can also form fluorescent probes with other molecules,and has been used to detect amino acids,dipeptides,and polypeptides.Based on the above background,this thesis studies the essential amino acid molecules of the human body,as well as the host-guest chemistry of dipeptides,peptide molecules and cucurbit[6]uril,tetramethylcucurbit[6]uril,cucurbit[7]uril and cucurbit[8]uril.And the specific recognition function of amino acids based on the fluorescent probe system constructed by cucurbit[7]uril and palmatine.The properties of the self-installed system were studied by single crystal X-ray diffraction,nuclear magnetic resonance?NMR?,isothermal thermal titration?ITC?,UV absorption spectroscopy,fluorescence spectroscopy and mass spectrometry?MS?.The results show that:?1?Fluorescent probes composed of cucurbituril and guest molecules have certain value for the recognition of amino acids.Here we have studied the recognition of amino acids by the fluorescent probe system constructed by cucurbit[7]uril and palmatine.The results showed that the constructed fluorescent probe could specifically recognize phenylalanine when the ratio of the main quaternary cucurbituril to the guest scutellaria was 1:1,which provided a certain reference value for the detection of amino acids.?2?When glycine?Gly?is selected as the guest,Q[6]can react with glycine to form a host-guest complex with a ratio of1:2,and a part of the group containing one end of the carboxyl group enters the interior of the Q[6]cavity.Further,after the addition of the metal Cd²⁺to the Q[6]-Gly system,the Q[6]-Gly-metal ion can be obtained to form a supramolecular self-assembly.Similarly,when glycine?Gly?is selected as a guest,TMeQ[6]can react with glycine to form a host-guest complex with a ratio of 1:1,and a part of the group containing one end of the carboxyl group enters the interior of the TMEQ[6]cavity.Further,after the addition of the metal Ca²⁺to the TMeQ[6]-Gly system,a supramolecular self-assembly in which the action ratio of TMeQ[6]-Gly-metal ions is1:1:1 can be obtained.?3?Several common dipeptides and tripeptides were selected at the same time to study their mode of action with cucurbituril.Studies on the molecular recognition properties of cucurbituril and dipeptides and tripeptides show that for tetramethylcucurbit[6]uril with smaller cavities,the dipeptides all act on the ports of the cucurbituril to form self-assemblies;Both the cucurbit[7]uril and the inverted cucurbit[7]uril can encapsulate the guest molecules,but there is a certain difference,because the cavity of the cucurbit[7]uril is slightly larger than the cavity of the inverted cucurbit[7]uril,so much so that when the cucurbit[7]uril is wrapped in the object,the binding site is different;for the cucurbit[8]uril,the object is also partially encapsulated.?4?In order to compare,the paper also studied the interaction characteristics of amino acids with inverted cucurbit[6]uril as the main body.When leucine or serine is selected as the guest,metal ions are added as an inducer,and leucine or serine and the inverted cucurbit[6]uril can form a supramolecular self-assembly having a ratio of 1:1.