Structural analysis of interpenetrated methyl‐modified MOF‐5 and its gas‐adsorption properties

The first example of an interpenetrated methyl‐modified MOF‐5 with the formula Zn₄O(DMBDC)₃(DMF)₂, where DMBDC^2? is 2,5‐dimethylbenzene‐1,4‐dicarboxylate and DMF is N,N‐dimethylformamide (henceforth denoted as Me₂MOF‐5‐int ), namely, poly[tris(μ₄‐2,5‐dimethylbenzene‐1,4‐dicarboxylato)bis(N,N‐dimethylformamide)‐μ₄‐oxido‐tetrazinc(II)], [Zn₄(C₁₀H₈O₄)₃O(C₃H₇NO)₂]_n, has been obtained from a solvothermal synthesis of 2,5‐dimethylbenzene‐1,4‐dicarboxylic acid and Zn(NO₃)₂·6H₂O in DMF. A systematic study revealed that the choice of solvent is of critical importance for the synthesis of phase‐pure Me₂MOF‐5‐int , which was thoroughly characterized by single‐crystal and powder X‐ray diffraction (PXRD), as well as by gas‐adsorption analyses. The Brunauer–Emmett–Teller surface area of Me₂MOF‐5‐int (660 m² g^?1), determined by N₂ adsorption, is much lower than that of nonpenetrated Me₂MOF‐5 (2420 m² g^?1). However, Me₂MOF‐5‐int displays an H₂ uptake capacity of 1.26 wt% at 77 K and 1.0 bar, which is comparable to that of non‐interpenetrated Me₂MOF‐5 (1.51 wt%).     

Coumarin-4-ylmethoxycarbonyls as phototriggers for alcohols and phenols

Caged compounds can be used to regulate the spatial and temporal dynamics of signaling molecules in live cells. Photochemical properties of coumarin-4-ylmethoxy carbonates (1a-d) are investigated to construct caged compounds of hydroxy-containing molecules. All the compounds possess desired properties as phototriggers for alcohols and phenols. The 6-bromo-7-hydroxycoumarin-4-ylmethoxycarbonyl (Bhcmoc) group has the highest photochemical efficiency and is applied to make caged compounds of 1,2-dioctanoylglycerol (diC(8)), Tyr-OMe, and adenosine. [reaction: see text]     

Electron-transfer mechanism in radical-scavenging reactions by a vitamin E model in a protic medium

The scavenging reaction of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH.) or galvinoxyl radical (GO.) by a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), was significantly accelerated by the presence of Mg(ClO4)2 in de-aerated methanol (MeOH). Such an acceleration indicates that the radical-scavenging reaction of 1H in MeOH proceeds via an electron transfer from 1H to the radical, followed by a proton transfer, rather than the one-step hydrogen atom transfer which has been observed in acetonitrile (MeCN). A significant negative shift of the one-electron oxidation potential of 1H in MeOH (0.63 V vs. SCE), due to strong solvation as compared to that in MeCN (0.97 V vs. SCE), may result in change of the radical-scavenging mechanisms between protic and aprotic media.     

RNA separation by in-capillary denaturing polymer electrophoresis with 1,2,5-thiadiazole as an additive

1,2,5-Thiadiazole improved RNA separation with in-capillary denaturing polymer electrophoresis. 1,2,5-Thiadiazole was synthesized as an extraction solvent substituted for a halogenated solvent. While 1,2,5-thiadiazole was an excellent extraction solvent and an environmentally friendly solvent, we found that 1,2,5-thiadiazole was a strong hydrophobic compound for RNA and the RNA separation performance by in-capillary denaturing polymer electrophoresis was dramatically improved. We suggest "in-capillary denaturing polymer electrophoresis" as an RNA separation that realizes the denaturing and separation simultaneously. RNA separation by the method required a strong denaturant, acetic acid, to cleave the intramolecular hydrogen. The running buffer containing acetic acid was of high conductivity and low pH, in which the condition introduced Joule heating and low sensitivity. While conventional denaturants, formaldehyde and urea, maintained small electric conductivity and neutral pH, these denaturants were too weak to achieve the RNA separation by in-capillary denaturing polymer electrophoresis. 1,2,5-Thiadiazole being a neutral molecule, both conductivity and buffer pH were able to be adjusted to a desirable strength for RNA separation. In this paper, we report that RNA separation by in-capillary denaturing polymer electrophoresis in neutral pH was achieved and the sensitivity for RNA separation was higher than that for RNA separation by in-capillary denaturing polymer electrophoresis with acetic acid.     

Design and synthesis of dual inhibitors of acetylcholinesterase and serotonin transporter targeting potential agents for Alzheimer's disease

Highly efficient acetylcholinesterase (AChE) and serotonin transporter (SERT) dual inhibitors, (S)-4 and (R)-13 were designed and synthesized on the basis of the hypothetical model of AChE active site. Both compounds showed potent inhibitory activities against AChE and SERT. [structure: see text]     

Molecular dynamics simulation of an archaeal lipid bilayer with sodium chloride

We have performed molecular dynamics simulations of a bilayer formed by the synthetic archaeal lipid, diphytanyl phosphatidylcholine, in NaCl electrolyte solution at four different concentrations (0-4 M) to investigate how structural and dynamic properties of the model archaeal membrane are changed due to the ionic strength of the solution. The archaeal lipid bilayer shows minor changes in their physical properties, indicating the unusual high stability of the membrane against salt, though small reductions of molecular area and lateral diffusion of the lipid are detected at the highest electrolyte concentration of 4 M. Sodium ions penetrate to the ether-rich region, where the ions are likely bound to the ether oxygen in the sn-1 chain rather than to that in the sn-2 chain. The observed salt bridges among two or three neighboring lipids account for the small reduction in the molecular area. The bound ions together with the counter (chloride) ions give rise to a diffusive electric double layer; as a result, the membrane dipole potential is slightly increased with increasing NaCl concentration.     

Iriomoteolide-1a, a potent cytotoxic 20-membered macrolide from a benthic dinoflagellate amphidinium species

A potent cytotoxic 20-membered macrolide, iriomoteolide-1a (1), has been isolated from a benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was elucidated on the basis of detailed analyses of 2-D NMR data. The relative and absolute stereochemistries were assigned by the combination of conformational analyses using NMR data and modified Mosher's method of 1.     

Photo‐Cross‐Linked Small‐Molecule Microarrays as Chemical Genomic Tools for Dissecting Protein–Ligand Interactions

We have developed a unique photo‐cross‐linking approach for immobilizing a variety of small molecules in a functional‐group‐independent manner. Our approach depends on the reactivity of the carbene species generated from trifluoromethylaryldiazirine upon UV irradiation. It was demonstrated in model experiments that the photogenerated carbenes were able to react with every small molecule tested, and they produced multiple conjugates in most cases. It was also found in on‐array immobilization experiments that various small molecules were immobilized, and the immobilized small molecules retained their ability to interact with their binding proteins. With this approach, photo‐cross‐linked microarrays of about 2000 natural products and drugs were constructed. This photo‐cross‐linked microarray format was found to be useful not merely for ligand screening but also to study the structure–activity relationship, that is, the relationship between the structural motif (or pharmacophore) found in small molecules and its binding affinity toward a protein, by taking advantage of the nonselective nature of the photo‐cross‐linking process.     

XAFS study of the complex of an acetylacetonate-based ligand and copper ion

An X-ray absorption fine structure (XAFS) study has been conducted to reveal the local structure and chemical state of the copper in the complex of an acetylacetonate-based ligand (L1) and copper ion in acetonitrile solution. The copper ion in the complex was found to be divalent from the Cu K-edge X-ray absorption near-edge structure (XANES) spectrum. The FEFF (ab initio multiple scattering calculations of XAFS) were performed with the model compounds, whose structures were optimized by using MOPAC program with AM1 Hamiltonian. The comparative study of the experimental XAFS spectra and theoretical calculations from FEFF gave the perspectives for clarifying the coordination structure of the complex of L1 and copper ion.     

Polarographic reduction of 1-substituted 1,2,4-triazoles

The polarographic reduction of 1-substituted 1,2,4-triazoles in dimethylformamide (DMF) and acetonitrile was studied. 1-Methyl-, 1-ethyl-, and 1,2,4-triazoles are not reduced on a mercury electrode over the range of potentials accessible for polarography. 1-Phenyl-1,2,4-triazole and 1-vinyl-1,2,4-triazole are reduced in acetonitrile via a one-electron mechanism at high negative potentials. The reduction of 1-vinyl-1,2,4-triazole is accompanied by polymerization of the electrolysis products. A possible mechanism for the electrochemical reduction is discussed. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 408–410, March, 1980.