Tokyo University of Science

About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Catalysis & Thin film. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.

Sugar-Installed Polymer Micelles: Synthesis and Micellization of Poly(ethylene glycol)−Poly(d,l-lactide) Block Copolymers Having Sugar Groups at the PEG Chain End

Abstract: A poly(ethylene glycol)−poly(d,l-lactide) block copolymer (PEG−PLA) having a site specifically protected-sugar group at the PEG chain end was synthesized through a successive ring-opening polymerization of ethylene oxide and d,l-lactide using a metalated protected sugar as an initiator. Removal of protective groups from the sugar residue in the block copolymer was quantitatively carried out using 80% trifluoroacetic acid at room temperature, yielding a block copolymer having a glucose or galactose residue at the chain end in a regioselective manner. Polymer micelles having sugar residues on the surface were then prepared by dialyzing an N,N-dimethylacetamide solution of the sugar-bearing PEG−PLA block copolymer against water. Dynamic light-scattering measurement of the polymer micelle solution revealed that the scaled characteristics line width had essentially no angular dependence, consistent with the spherical geometry of the polymer micelle. The diameter and polydispersity index of the polymer micelle,...

Organocatalyzed Michael Addition of Aldehydes to Nitro Alkenes – Generally Accepted Mechanism Revisited and Revised

Abstract: The amine-catalyzed enantioselective Michael addition of aldehydes to nitro alkenes (Scheme 1) is known to be acid-catalyzed (Fig. 1). A mechanistic investigation of this reaction, catalyzed by diphenylprolinol trimethylsilyl ether is described. Of the 13 acids tested, 4-NO2C6H4OH turned out to be the most effective additive, with which the amount of catalyst could be reduced to 1 mol-% (Tables 2–5). Fast formation of an amino-nitro-cyclobutane 12 was discovered by in situ NMR analysis of a reaction mixture. Enamines, preformed from the prolinol ether and aldehydes (benzene/molecular sieves), and nitroolefins underwent a stoichiometric reaction to give single all-trans-isomers of cyclobutanes (Fig. 3) in a [2+2] cycloaddition. This reaction was shown, in one case, to be acid-catalyzed (Fig. 4) and, in another case, to be thermally reversible (Fig. 5). Treatment of benzene solutions of the isolated amino-nitro-cyclobutanes with H2O led to mixtures of 4-nitro aldehydes (the products 7 of overall Michael addition) and enamines 13 derived thereof (Figs. 6–9). From the results obtained with specific examples, the following tentative, general conclusions are drawn for the mechanism of the reaction (Schemes 2 and 3): enamine and cyclobutane formation are fast, as compared to product formation; the zwitterionic primary product 5 of C,C-bond formation is in equilibrium with the product of its collapse (the cyclobutane) and with its precursors (enamine and nitro alkene); when protonated at its nitronate anion moiety the zwitterion gives rise to an iminium ion 6, which is hydrolyzed to the desired nitro aldehyde 7 or deprotonated to an enamine 13. While the enantioselectivity of the reaction is generally very high (>97% ee), the diastereoselectivity depends upon the conditions, under which the reaction is carried out (Fig. 10 and Tables 1–5). Various acid-catalyzed steps have been identified. The cyclobutanes 12 may be considered an off-cycle ‘reservoir’ of catalyst, and the zwitterions 5 the ‘key players’ of the process (bottom part of Scheme 2 and Scheme 3).

Perivascular leukocyte clusters are essential for efficient activation of effector T cells in the skin

Abstract: It remains largely unclear how antigen-presenting cells (APCs) encounter effector or memory T cells efficiently in the periphery. Here we used a mouse contact hypersensitivity (CHS) model to show that upon epicutaneous antigen challenge, dendritic cells (DCs) formed clusters with effector T cells in dermal perivascular areas to promote in situ proliferation and activation of skin T cells in a manner dependent on antigen and the integrin LFA-1. We found that DCs accumulated in perivascular areas and that DC clustering was abrogated by depletion of macrophages. Treatment with interleukin 1α (IL-1α) induced production of the chemokine CXCL2 by dermal macrophages, and DC clustering was suppressed by blockade of either the receptor for IL-1 (IL-1R) or the receptor for CXCL2 (CXCR2). Our findings suggest that the dermal leukocyte cluster is an essential structure for elicitating acquired cutaneous immunity.