Sythesis Of Peptides Sequences And The Discrimination Properties Research For Mono-saccharides

As one of the three substances in living organisms,carbohydrates participates lots of biological processes including information transfer,cell interaction in the immune as well as tumor metastasis.Desipite the important roles that carbohydrates play in a wide range of recognition processes in living organisms,the molecular details of the recognition events and the driving force for carbohydrates binding is still not well understand.So far,artificial carbohydrates receptors provide valuable model systems to study the underlying mechanism and principles of carbohydrates molecular recognition processes.The current study for artificial carbohydrates receptors is involved in organic media and aqueous media.Even if artifical carbohydrates receptors in organic media has achieved significant progress with the association constant order of 105M-1 magnitudes,the recognition of carbohydrates in aqueous media,in which solvent molecules compete for binding sites of the receptor,is still a large challenge in artificial receptor chemistry.Due to the carbohydrate-based recognition processes in nature conducted in aqueous media, the well designed artifical carbohydrates in aqueous media may serve as a basis for the development of biological chemistry,medical diagnosis or therapeutics intervened in biologically important carbohydrates recognitions.Lectin is a class of proteins found in bacteria,plants,fungi and animals that are known for the properties of binding specific oligoasccharide moieties.Inspired by lectins,our strategy is to mimick the binding motifs of lectin-carbohydrate complexes.We extracted the core sequences in various lectins to design the effective and seletive artificial carbohydrates receptors.The main results are as follows:1.Solid-phase synthesis principle was introduced to synthesize peptide sequences Tyr-Tyr,Ala-Ala,Trp-Trp,Arg-Arg,Asp-Gly,Asp-Asn,Pro-Ala,Asp-Pro,Pro-Asn, Tyr-Asp, Tyr-Gly, Tyr-Asn and lectins core sequences-DPAD and FVVD.And the products were purified by high performance liquid chromatograph(HPLC),and then characterized MS,and the results proved that target products were successsfully obtained,providing the raw materials for the follow-up work.2. Fluorescent groups- fluorescein isothiocyanate was successfully grafted to pepitide sequences-DPAD and FVVD. The samples were purified by HPLC and characterized by MS,demonstrating that the samples are what we expected.And the preparations for studying the binding perfomance of DPAD and FVVD are well made.3.Fluorescence titration was applied to preliminary investigate the binding performance of receptor DPAD and FVVD with six various monosaccharides which isD-glucose,D-NAcetyl-glucose,D-galactose,D-Nacetyl-galactose,D-mannose,D-fuco se.The results shows that DPAD exhibits great discrimination performance for D-glucose and could discriminate D-glucose from other five monosaccharides.And the result shows that with the addition of D-mannose into FVVD,the fluorescence intensity is gradully going down,reflecting well discimination ability for D-mannose.The association constant table shows us that the K value for the DPAD?monosaccharides are all higher than K values for the FVVD? monosaccharides,displaying DPAD bound the six monosaccharides better than the FVVD.The K value for the DPAD?monosaccharides is the highest in all of other monosaccharides and exhibits the secondary constant,indicating that receptor DPAD tending towards the formation of strong 2:1 receptor-D-glucose complex.In conclusion,DPAD and FVVD display a promising perfomance to discrimate D-glucose and D-mannose respectively in aqueous media and could be futher exploited as a kind of material to identify D-glucose and D-mannose.