Microscopic approach to the antiproton-nucleus optical potential

By using the self-energy of an antiproton evaluated in nuclear matter, the antiproton effective interaction with a bound nucleon is derived and is found to have a drastic density dependence. The p?-nucleus optical potential constructed by folding the effective interaction well reproduces experimental data on the p?-nucleus absorption cross section as well as on the complex level shift of p?-atoms. In addition, it is pointed out that the strong spin-orbit interaction spreads each doublet and considerably affects the lower complex level shift.     

Preorganised effects of a tetramesogenic supermolecule on supramolecular assembly in the liquid crystalline phases

After preparing a homologous series of tetrameric mesogenic compounds in which two U-shaped molecules were connected via a rigid benzene derivative or a flexible alkyl chain, we investigated their phase transition behaviour using optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The compounds possessing an alkyl spacer as the central group exhibited nematic and smectic A phases just as the corresponding U-shaped molecule did. The compound possessing a 1,2-benzene unit as the connecting group showed nematic and smectic A phases, although the compound possessing a 1,3-benzene unit exhibited only an anticlinic smectic C phase. Structure–property relations of the liquid crystalline tetramers are interpreted in terms of preorganised effects of the four mesogenic units.     

Diastereoselective synthesis of highly functionalized fluoroalkene dipeptide isosteres and its application to Fmoc-based solid-phase synthesis of a cyclic pentapeptide mimetic

A diastereoselective and divergent method for synthesis of a highly functionalized (Z)-fluoroalkene dipeptide isosteres has been developed. The key feature of this synthetic method is an efficient one-pot reaction involving reduction/asymmetric alkylation via transmetalation, which produces trans-amide type (Z)-fluoroalkenes flanking two stereogenic centers in high yields, with excellent (Z)-selectivity and diastereoselectivity. Practical Fmoc-based solid-phase synthesis of a specific CXCR4 antagonistic pseudopeptide 25 containing (Z)-fluoroalkene isostere is also described.     

Photoinduced electron‐transfer reactions of tris(2,2′‐bipyridine)ruthenium(II)‐based carbonic anhydrase inhibitors tethering plural binding sites

Tris(2,2′‐bipyridine)ruthenium(II) complex‐based carbonic anhydrase (CA) inhibitors, [Ru(bpy)₂(bpydbs)]²⁺ {bpy = 2,2′‐bipyridine and bpydbs = 2,2′‐bipyridinyl‐4,4′‐dicarboxilic acid bis[(2‐{2‐[2‐(4‐sulfamoylbenzoylamino)ethoxy]ethoxy}ethyl)amide]} and [Ru(bpydbs)₃]²⁺, tethering plural benzenesulfonamide groups have been prepared. The CA catalytic activity was effectively suppressed by these synthetic [Ru(bpy)₂(bpydbs)]²⁺ and [Ru(bpydbs)₃]²⁺ inhibitors, and their dissociation constants at pH = 7.2 and at 25°C were determined to be K_I = 0.93 ± 0.02 μM and K_I = 0.24 ± 0.03 μM, respectively. Next, 2 photoinduced electron‐transfer (ET) systems comprising a Ru²⁺‐CA complex and an electron acceptor, such as chloropentaamminecobalt(III) ([CoCl(NH₃)₅]²⁺) or methylviologen (MV²⁺) were studied. In the presence of CA and a sacrificial electron acceptor, such as pentaamminechlorocobalt(III) complex, the photoexcited triplet state of ³([Ru(II)]²⁺)* was quenched through an intermolecular photoinduced ET mechanism. In case of the [Ru(bpydbs)₃]²⁺‐CA‐MV²⁺ system, the photoexcited triplet state of ³([Ru(bpydbs)₃]²⁺)* was quenched by sacrificial quencher through an intermolecular photoinduced ET mechanism, giving the oxidized [Ru(bpydbs)₃]³⁺. Then the following intramolecular ET from the amino acid residue, Tyr6, near the active site of CA proceeded. We observed a transient absorption around at 410 nm, arising from the formation of a Tyr^?+ in the [Ru(bpydbs)₃]²⁺‐CA‐MV²⁺ system. These artificial Ru(II)‐CA systems may clearly demonstrate both intermolecular and intramolecular photoinduced ET reactions of protein and could be one of the interesting models of the ET proteins. Their photophysical properties and the detailed ET mechanisms are discussed in order to clarify the multistep ET reactions.     

Synthesis of maltopentaose‐conjugated surface‐active styrenic monomers and their micellar homopolymerization in water

Maltopentaose (Mal₅)‐conjugated surface‐active styrenic monomers 1a , 1b , and 1c are described, which contain hydrophobic spacers, such as C1, C5, and C7 alkylene chains, respectively. The glycomonomers 1a‐c were synthesized by the direct β‐N‐glycosyl reaction of styrene derivatives with aminoalkyl groups 4a‐c onto Mal₅ in dry methanol, followed by the N‐acetylation with acetic anhydride. The self‐assembling properties for the aqueous solutions of 1a‐c were characterized by surface tension measurements and light scattering experiments, providing the physicochemical parameters for the formed 1a‐c micelles including the critical micelle concentration, apparent hydrodynamic radius (R_h,app), and weight average aggregation number (N_agg). The transmission electron microscope observations revealed the most important result in this study that 1a produced loose spherical micelles with the number average diameter (d_n) of 26 nm, while both 1b and 1c formed worm‐like micelles with the polymerizable core and the Mal₅ shell, whose number average contour lengths (l_ns) were 130 nm and 68 nm, respectively. The radical homopolymerizations of 1a‐c in water provided a substantial result in this study that 1b and 1c , that is, the glycomonomers forming the worm‐like micelles, showed a very high homopolymerizability in water. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1671–1679     

Synthesis of Hyperbranched Polysaccharide by Thermally Induced Cationic Polymerization of 1,6-Anhydrohexopyranose

The thermally induced cationic polymerizations of 1,6-anhydro-β-D -glucopyranose ( 1a ), 1,6-anhydro-β-D -mannopyranose ( 1b ) and 1,6-anhydro-β-D -galactopyranose ( 1c ) as a latent cyclic AB₄-type monomer were carried out using (S-2-butenyl)tetramethylenesulfonium hexafluoroantimonate ( 2 ) as an initiator. The solution polymerization in propylene carbonate proceeded without gelation to produce the water-soluble hyperbranched polysaccharides ( 3a-c ) with controlled molecular weights and narrow polydispersities. The degree of branching (DB), estimated by the methylation analysis of 3a-c , was in the range of 0.38 – 0.49. The thermally induced cationic polymerization of 1a-c using 2 is a facile method leading to a hyperbranched polysaccharide with a high DB value.