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Kato, Yoshinori,Onishi, Hiraku,Machida, Yoshiharu The Polymer Society of Korea 2003 Macromolecular Research Vol.11 No.5
Reductive amination of N-succinyl-chitosan (1) and lactose using sodium cyanoborohydride in 1/15 M phosphate buffer (pH 6.0) for 6 d was suitable for the preparation of lactosaminated N-succinyl-chitosan (2). At 8, 24 and 48 h after i.v. administration of fluorescently labeled 1 (1') or 2 (2'), Peyer's patch, mesenteric lymph nodes, testes, prostate, preputial grand, intestine (small intestine plus cecum), femoral muscle, backbone and peritoneum were taken. Peyer's patch and mesenteric lymph nodes were put together as lymph nodes. Over 10% of dose/g tissue was distributed to the prostate and lymph nodes at 48 h post-administration in both l' and 2'.2' was easily distributed into not only the liver but also prostate, intestine, preputial gland and lymph nodes. Although galactose receptors are known to exist not only on the liver parenchymal cells but also on prostate and testes, the selective distribution of 2' into the prostate and the testes were not observed clearly. This study suggested that 1 and 2 should have possibilities for both the prevention and cure of lymph node metastasis as drug carriers.
Paramagnetic-assisted NMR Analyses of Conformational Dynamics of Gangliosides
Ying Zhang,Takumi Yamaguchi,Sayoko Yamamoto,Yoshinori Uekusa,Koichi Kato 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
For better understanding the molecular basis of the mechanism underlying oligosaccharides functions, it is quite desirable to gain detail information on their conformational dynamics in solution. However, the conformational analysis of oligosaccharides is still a remaining challenge, because of their branched covalent structures and dynamic conformational multiplicities, which hinder conventional analytical methods. For conformational characterization of flexible oligosaccharides, their structures should not be dealt with as a single well-defined global free energy minimum but as an ensemble of low energy conformers. Hence, we have been developing a methodology for evaluating a dynamic ensemble of oligosaccharide conformations by employing paramagnetic-assisted NMR methods based on paramagnetic effects such as pseudocontact shift (PCS) and paramagnetic relaxation enhancement (PRE) in conjunction with molecular dynamics (MD) simulations [1,2]. We applied this approach to the conformational dynamics analyses of branched GM2 tetrasaccharide, βGalNAc-(1-4)-[αNeu5Ac-(2-3)]-βGal-(1-4)-βGlc, which share the common core structure of gangliosides forming an integral part of cellular membranes. We synthesized the GM2 tetrasaccharide covalently attached to a lanthanide chelating-tag (Fig. 1). Upon complexation with paramagnetic lanthanide ions, the tagged sugar exhibited NMR spectral changes due to PCSs. The observed PCS values were in excellent agreement with those back-calculated from the 3D ensemble models derived from the MD calculations. In addition, we have developed spin-labeling method of gangliosides for their NMR analyses in amphipathic environments. These methodologies open a new prospect for conformational analyses of dynamic structures of gangliosides toward decoding glycocodes from the 3D structural aspects.