Doubly activated supramolecular reaction: transesterification of acyclic oligoether esters with metal alkoxides

Transesterification reactions of acyclic oligoether esters E3-E10 with metal alkoxides were accelerated upon noncovalent complexation of the esters with metal ions. In the reaction of monovalent alkaline metal alkoxides, CH(3)ONa and CH(3)OK, plots of the observed rate constants k(obs) with respect to the chain length of E3-E10 showed selective acceleration of the transesterification. Compared with the shortest E3, which can hardly bind metal ion, 4.3- and 6.6-fold accelerations in the maxima were achieved in the combinations of E5/CH(3)ONa and E6/CH(3)OK, respectively. Supramolecular intermediate complex could be spectrometrically visualized by ESI-FT-ICR-MS in the course of reaction. Kinetic experiments, together with structural analyses by means of NMR, mass spectrometry, and DFT calculations of the intermediate complexes, indicate that a size-fit complex of host substitute with alkali metal ion allows strong electron withdrawing due to the close contact of the carbonyl oxygen to the metal ion, resulting in the selective rate enhancement of the reaction, while in the reaction of E3-E10 with a divalent alkaline earth metal alkoxide, (CH(3)CH(2)O)(2)Ba, the k(obs) values increased stepwise with elongation of the side arm to attain an dramatic large acceleration. In comparison with the k(obs) of E3, 4610-fold acceleration was achieved in the reaction of E10. The double activation of the host substrate and guest counter nucleophile at once brings about this extraordinary rate acceleration. The strong wrapping complexation of long oligoether ester with barium ethoxide allows for the effective electron withdrawal from the ester carbonyl group (host activation) as well as separation of the accompanying guest alkoxide anions (guest activation).     

Molecular dynamics study on the ligand recognition by tandem SH3 domains of p47phox, regulating NADPH oxidase activity

The phagocyte NADPH oxidase complex plays a crucial role in host defense against microbial infection through the production of superoxides. Chronic granulomatous disease (CGD) is an inherited immune deficiency caused by the absence of certain components of the NADPH oxidase. Key to the activation of the NADPH oxidase is the cytoplasmic subunit p47phox, which includes the tandem SH3 domains (N-SH3 and C-SH3). In active phagocytes, p47phox forms a stable complex with the cytoplasmic region of membrane subunit p22phox that forms a left-handed polyproline type-II (PPII) helix conformation. In this report, we have analyzed the conformational changes of p47phox-p22phox complexes of wild-type and three mutants, which have been detected in CGD patients, using molecular dynamics simulations. We have found that in the wild-type, two basal planes of PPII prism in cytoplasmic region of p22phox interacted with N-SH3 and C-SH3. In contrast, in the modeled mutants, the residue at the ape of PPII helix, which interacts simultaneously with both of the tandem SH3 domains in the wild-type, moved toward C-SH3. Furthermore, interaction energies of the cytoplasmic region of p22phox with C-SH3 tend to decrease in these mutants. All these findings led us to conclude that interactions between N-SH3 of p47phox and PPII helix, which is formed by cytoplasmic region of p22phox, may play a significant role in the activation of the NADPH oxidase.     

Membrane potential across anion-exchange membranes in acidic solution system

The membrane potential across anion-exchange membranes in H2SO4 and Na2SO4 solutions was measured, and the experimental results were fitted to the theory in the 2-1 electrolyte system based on the Donnan equilibrium and the Nernst-Planck flux equations. For the Na2SO4 solution, the Donnan potential makes a significant contribution to the membrane potential, but for the H2SO4 solution, the diffusion potential significantly contributes to the membrane potential. The diffusion potential has a greater contribution to the membrane potential across AEM-2 with a high water content than that across AEM-1. These results suggest that a proton with a high mobility can move without substantial influence of electrostatic interaction in a positively charged membrane.     

Nanometer-scale ordering in cast films of columnar metallomesogen as revealed by STM observations

STM observations were performed on a cast film of a columnar metallomesogen ([Cr(5C8)3]; 5C8 = 1-(3,4,5-trioctyloxyphenyl)-3-(3,4-dioctyloxyphenyl)propane-1,3-dionate anion) on a graphite surface, revealing the nanometer-scale surface ordering into an oblique lattice (a = 10.5 nm, b = 11.5 nm, alpha = 55 degrees) possibly due to the DeltaLambda-chiral interactions.     

Highly selective double chalcogenation of isocyanides with disulfide-diselenide mixed systems

A highly selective method for introducing thio and seleno groups into a variety of isocyanides has been developed based on the elucidation of the relative reactivities of organic dichalcogenides and chalcogen-centered free radicals. When the reactions of aromatic isocyanides (ArNC) with organic disulfides (R'SSR') and diselenides (R'SeSeR') are conducted upon irradiation with a tungsten lamp through Pyrex (hnu>300 nm), simultaneous introduction of both thio and seleno groups into the isocyanides takes place to provide the corresponding thioselenation products (R'S-C(=NAr)-SeR') in good yields with excellent selectivity. In the cases of aliphatic isocyanides (RCN), a novel diselenide-assisted bisthiolation of RNC with diaryl disulfides (Ar'SSAr') proceeds successfully to give the corresponding bisthiolation products (Ar'S-C(=NR)-SAr'), although the same photoirradiated reaction of RNC with diaryl disulfides does not occur in the absence of diselenide. These double chalcogenation reactions are assumed to proceed via the formation of imidoyl radical intermediates by the reaction of isocyanides with relatively reactive thio radicals (compared with seleno radicals). The obtained thioselenation products can be employed as useful precursors for the construction of beta-lactam framework by the formal [2+2] cyclization with ketene equivalents.     

Weighted Hardy spaces on an interval and Poisson integrals associated with ultraspherical series

We prove that certain maximal functions defined through the Poisson integrals associated with ultraspherical series characterize some weighted Hardy spaces on the finite interval.     

Expanding the additive reduct of a model of Peano arithmetic

Let M be a model of first order Peano arithmetic ( PA ) and I an initial segment of M that is closed under multiplication. LetM₀ be the {0, 1,+}‐reduct ofM. We show that there is another model N of PA that is also an expansion of M₀ such that a · ^M a = a · ^N a if and only if a ∈ I for all a ∈ M.     

Simultaneous analysis of highly polar pharmaceutical adulterants in slimming products by hydrophilic interaction liquid chromatography

A chromatographic method utilizing hydrophilic interaction liquid chromatography was developed for the estimation of highly polar pharmaceutical adulterants in commercial slimming products. Five adulterants, phenylpropanolamine, salbutamol, phenformin, buformin, and metformin, were successfully separated on an XBridge^? amide column (3.5 µm, 4.6?×?250 mm) using a mobile phase composed of acetonitrile/26.5 mM ammonium formate containing 0.1% formic acid (85:15) flowing at the rate of 0.8?mL/min. Wavelengths for monitoring the elution of these compounds were determined based on the wavelength of their absorption maxima (λ_max?=?208, 226, and 236 nm). The developed method was validated for specificity, linearity, accuracy, precision, and robustness. Interassay comparison showed that the performance of the hydrophilic interaction liquid chromatography-based method was superior to that of the traditional reversed-phase liquid chromatography-based method. Therefore, the proposed method is useful to analyze highly polar pharmaceutical adulterants in slimming products.