Glycosylation is one of the most important post- or cotranslational modifications of proteins, which affects the biological activities of the parent proteins by influencing the higherorder structure. This modification has been classified into two subtypes: namely N-linked type and O-linked type. Recently, a highly novel variant of glycoproteins that incorporate a C-glycosylated amino acid was identified in various proteins. The total synthesis of one such C-glycosyl amino acid, namely, C2-α-D-C-mannosylpyranosyl-L-tryptophan and related peptides was successfully achieved. The mannose and tryptophan moieties were connected via a ring opening of benzyl-protected 1, 2-anhydro-mannose by a lithiated indole derivative. After the functional group conversion and deprotection steps, the glyco-amino acid was synthesized in a concise and stereoselective manner, in high overall yields. Furthermore, intermediate azide acid can serve as a useful building block for peptide elongation. The stereoisomer, C2-α-D-C-glucosylpyranosyl-L-tryptophan was synthesized in a similar way. We describe here the synthesis of C-Man-Trp including by other groups and the possibility of application to clinical methods.
This review describes several NMR (Nuclear Magnetic Resonance) methods for analyzing the structure of oligosaccharides in addition to technical points such as assignment of all 1H NMR signals, NOE experiments, and modification of pulse programs.
Although Nuclear Magnetic Resonance (NMR) is one of the most powerful methods for determining molecular conformations, it was hard to apply it to protein-carbohydrate interaction conformational studies due to weak binding affinities. This problem has been solved by three dimensional NOESY-HSQC NMR techniques using synthesized 13C-labelled carbohydrate ligands. In addition, the liquid crystalline phase NMR, which is a new and revolutionary NMR method for the analysis of proteins, has been successfully applied to protein-carbohydrate interaction research field and has been able to give more highly sensitive results.
Since the 2-D/3-D HPLC mapping technique was proposed for structural analyses of N-glycans, approximately 500 different structures have been elucidated. Based on the accumulated data, we developed a web application, GALAXY (Glycoanalysis by the three axes of MS and chromatography), to utilize the 2-D/3-D maps more effectively. This application will facilitate search of candidate structures satisfying 2-D/3-D HPLC and/or mass spectrometric data and enable us to predict coordinates of putative PA-glycans and to trace the effects of glycosidase treatments in a graphical manner.