Interactions between polysialic acid and dopamine-lead compounds as revealed by biochemical and in silico docking simulation analyses.

Polysialic acid is an important glyco-epitope in vertebrate brains, while altered expressions of polySia and biosynthetic enzyme have been reported in brain diseases such as schizophrenia and depression. Recently, the binding between polySia and dopamine and the involvement of this in Akt signaling has been demonstrated. However, the molecular mechanism underlying the binding of polySia and dopamine remains unknown. Therefore, here, we demonstrated the interaction between dopamine and polySia using frontal affinity chromatography alongside docking simulations. In addition, we prepared dopamine-lead compounds to understand the detailed molecular basis of polySia binding by frontal affinity chromatography, enzyme-linked immunosorbent assay, and docking simulations.

Methylated (-)-epigallocatechin 3-O-gallate potentiates the effect of split vaccine accompanied with upregulation of Toll-like receptor 5.

Split-virus vaccine serves as a major countermeasure against influenza virus, but its effectiveness and protective action are not complete. We previously demonstrated the effect of Benifuuki, a green tea cultivar in Japan, on enhancing the split-virus vaccine-elicited immune response. However, little is known about the detail mechanisms. Here, we show that EGCG3"Me intake significantly potentiated the vaccine-elicited hemagglutination inhibition titer increase. Flow cytometry analysis revealed the increased Toll-like receptor 5 (TLR5) expression after EGCG3"Me treatment in lamina propria dendritic cells (LPDCs) and macrophages, which play crucial roles in the humoral immune system. TLR5 expression correlated with the level of interleukin-6 (IL-6)/C-C chemokine type receptor 5, which are important mediators of the humoral immunity. Taken together, In vivo and ex vivo studies showed that EGCG3"Me potentiated the split-virus vaccine-elicited immune response accompanied with the upregulation of TLR5 in intestine and splenocyte macrophages.

Chemical Synthesis of Residue-Selectively 13C and 2H Double-Isotope-Labeled Oligosaccharides as Chemical Probes for the NMR-Based Conformational Analysis of Oligosaccharides.

The conformational analysis of oligosaccharide is a fundamental issue in glycobiology. NMR measurements of atom-selectively 13C-labeled oligosaccharides have provided valuable information concerning their conformation, which would not be possible using nonlabeled oligosaccharides. The amount of accessible information from an atom-selectively labeled molecule, however, is limited. In this work, we report on the chemical synthesis of residue-selectively 13C- and 2H-labeled oligosaccharides and their use in conformational analysis. 1H NMR measurements of such double isotope-labeled compounds can provide a great deal of information on the dihedral angles across glycosidic linkages. We demonstrated this method in the conformational analyses of some linear and branched ß(1,3)-glucan oligosaccharides.

6-Azido-6-deoxy-l-idose as a Hetero-Bifunctional Spacer for the Synthesis of Azido-Containing Chemical Probes.

The design of 6-azido-6-deoxy-l-idose for use as a hetero-bifunctional spacer is reported. The hemiacetal at one terminus is an equivalent of an aldehyde and can react with nucleophiles, such as amino groups and electron-rich aromatics. The azido group at the other terminus bio-orthogonally undergoes a Hüisgen [3+2] cycloaddition with an acetylene. The idose derivative exhibited a higher level of reactivity towards oxime formation than a corresponding glucose derivative. The (13) C NMR spectrum of the uniformly (13) C-labeled 6-azido-idose indicated that the acyclic forms of the sugar totaled 0.3 % of all the isomers, whereas those of glucose totaled 0.01 %. The larger population of the acyclic forms of the idose derivative would result in higher reactivity towards electrophilic addition in comparison with glucose derivatives. Finally, we prepared a C-idosyl epigallocatechin gallate (EGCG) that bears an azido group through C-glycosylation of EGCG with 6-azido-idose. This glycosyl form of the C-idosyl EGCG exhibited a cytotoxicity against U266 cells that was comparable to that of EGCG. These results suggested that the EGCG derivative could be used as an effective chemical probe for the elucidation of EGCG biological functions.

Oxidative Deamination of Serum Albumins by (-)-Epigallocatechin-3-O-Gallate: A Potential Mechanism for the Formation of Innate Antigens by Antioxidants.

(-)-Epigallocatechin-3-O-gallate (EGCG), the most abundant polyphenol in green tea, mediates the oxidative modification of proteins, generating protein carbonyls. However, the underlying molecular mechanism remains unclear. Here we analyzed the EGCG-derived intermediates generated upon incubation with the human serum albumin (HSA) and established that EGCG selectively oxidized the lysine residues via its oxidative deamination activity. In addition, we characterized the EGCG-oxidized proteins and discovered that the EGCG could be an endogenous source of the electrically-transformed proteins that could be recognized by the natural antibodies. When HSA was incubated with EGCG in the phosphate-buffered saline (pH 7.4) at 37°C, the protein carbonylation was associated with the formation of EGCG-derived products, such as the protein-bound EGCG, oxidized EGCG, and aminated EGCG. The aminated EGCG was also detected in the sera from the mice treated with EGCG in vivo. EGCG selectively oxidized lysine residues at the EGCG-binding domains in HSA to generate an oxidatively deaminated product, aminoadipic semialdehyde. In addition, EGCG treatment results in the increased negative charge of the protein due to the oxidative deamination of the lysine residues. More strikingly, the formation of protein carbonyls by EGCG markedly increased its cross-reactivity with the natural IgM antibodies. These findings suggest that many of the beneficial effects of EGCG may be partly attributed to its oxidative deamination activity, generating the oxidized proteins as a target of natural antibodies.