Cover Picture: Theoretical Study on the Halogen–Zinc Exchange Reaction by Using Organozincate Compounds (Chem. Eur. J. 23/2009)

Density functional theory and fragment‐energy analysis have been used to probe the mechanism of the halogen–zinc exchange reaction. In their Full Paper on page 5686 ff. , M. Uchiyama, S. Nakamura et al. discuss three important factors in this reaction: The effect of the halogen species, the effect of the alkyl ligand on zinc, and the effect of the substrate nature.

     

Halorhodopsin from natronomonas pharaonis forms a trimer even in the presence of a detergent, dodecyl-beta-D-maltoside

Halorhodopsin (HR) is a transmembrane seven-helix retinal protein, and acts as an inward light-driven Cl⁻ pump. HR from Natronomonas pharaonis (NpHR) can be expressed in Escherichia coli inner membrane in large quantities. Here, we showed that NpHR forms the trimer structure even in the presence of 0.1% (2 m m ) to 1% (20 m m ) dodecyl-β- d -maltoside (DDM), whose concentrations are much higher than the critical micelle concentration (0.17 m m ). This conclusion was drawn from the following observations. (1) NpHR in the DDM solution showed an exciton-coupling circular dichroism (CD) spectrum. (2) From the elution volume of gel filtration, the molecular mass of the NpHR–DDM complex was estimated. After evaluation of the mass of the bound DDM molecules, the mass of NpHR calculated was approximately equal to that of the trimer. (3) The cross-linked NpHR by glutaraldehyde gave the SDS-PAGE corresponding to the trimer. Mass spectra of these samples also support the notion of the trimer. Using the membrane fractions expressing NpHR ( Escherichia coli and Halobacterium salinarum ), CD spectra showed exciton-coupling, which suggests strongly the trimer structure in the cell membrane.     

Improvement of Ni/SDC anode by alkaline earth metal oxide addition for direct methane–solid oxide fuel cells

The anodic performances of Ni/CeO₂–Sm₂O₃(Ni/SDC) modified by the addition of alkaline earth metal oxides (MgO, CaO, and SrO) were investigated for direct oxidation of CH₄ in solid oxide fuel cells (SOFCs). Although the initial power density of cell with Ni/SDC anode modified by the addition of CaO was slightly lower than that of cell with Ni/SDC, the former anode exhibited an excellent stability compared to the latter one. Such a high stability of Ni–CaO/SDC anode may come from the inhibition of carbon deposition in addition to the retained ionic conductivity of anode.     

Synthesis of collagen-like sequential polypeptides containing O-phospho-L-hydroxyproline and preparation of electrospun composite fibers for possible dental application

A synthetic route is described for collagen-like polypeptides constructed from O-phospho-L-hydroxyproline [Hyp(PO(3)H(2))] residues. Using the synthetic polypeptides and a natural protein, gelatin, fine fibers and their network structures (ESNWs) were prepared via electrospinning. The composite ESNWs can induce the mineralization of calcium phosphate. The phosphoryl groups of the Hyp(PO(3)H(2)) residues affect both the crystalline phase and amount of the calcium phosphate, depending on the chemical structure in the repeating sequence. The composite ESNWs can be developed as a biocompatible replacement of the extracellular matrix of hard tissues, and thus can be applied as dental materials for restoration of dental cavities or as a sealant for pits and fissures.     

Complementary structural information of positive- and negative-ion MSn spectra of glycopeptides with neutral and sialylated N-glycans

Positive- and negative-ion MSn spectra of chicken egg yolk glycopeptides binding a neutral and a sialylated N-glycan were acquired by using electrospray ionization linear ion trap time-of-flight mass spectrometry (ESI-LIT-TOFMS) and collision-induced dissociation (CID) with helium as collision gas. Several characteristic differences were observed between the positive- and negative-ion CID MSn (n = 2, 3) spectra. In the positive-ion MS2 spectra, the peptide moiety was presumably stable, but the neutral N-glycan moiety caused several B-type fragmentations and the sialylated N-glycan almost lost sialic acid(s). In contrast, in the negative-ion MS2 spectra, the peptide moiety caused several side-chain and N-glycan residue (e.g., N-acetylglucosamine (GlcNAc) residue) fragmentations in addition to backbone cleavages, but the N-glycan moieties were relatively stable. The positive-ion MS3 spectra derived from the protonated peptide ion containing a GlcNAc residue (203.1 Da) provided enough information to determine the peptide amino-acid sequence including the glycosylation site, while the negative-ion MS3 spectra derived from the deprotonated peptide containing a 0,2X1-type cross-ring cleavage (83.1 Da) complicated the peptide sequence analysis due to side-chain and 0,2X1 residue related fragmentations. However, for the structural information of the N-glycan moiety of the glycopeptides, the negative-ion CID MS3 spectra derived from the deprotonated 2,4A6-type cross-ring cleavage ion (neutral N-glycan) or the doubly deprotonated B6-type fragment ion (sialylated N-glycan) are more informative than are those of the corresponding positive-ion CID MS3 spectra. Thus, the positive-ion mode of CID is useful for the analyses of peptide amino-acid sequences including the glycosylation site. The negative-ion mode of CID is especially useful for sialylated N-glycan structural analysis. Therefore, in the structural analysis of N-glycopeptides, their roles are complementary.     

Structural analysis of aggregates formed by a thermoresponsive homopolymer in dilute aqueous solutions

The aqueous solution of a thermoresponsive polymer, poly[2‐(2‐ethoxy) ethoxyethyl vinyl ether] poly(EOEOVE), contains a tiny amount of large polymer aggregates at low polymer concentrations far below the lower critical solution temperature (～40 °C). The molar mass M_w,slow, radius of gyration 〈S²〉, and hydrodynamic radius R_H,slow of the aggregating component of poly(EOEOVE) were obtained by simultaneous static and dynamic light scattering as functions of the polymer concentration and temperature, while the weight fraction w_slow of the component was estimated by size‐exclusion chromatography. The M_w,slow dependencies of 〈S²〉 and R_H,slow, as well as the ratio 〈S²〉/R_H,slow, indicated that the poly(EOEOVE) aggregate takes a sparsely branched polymer‐like conformation. We have analyzed the structure of the aggregate, using the branched polymer model of random type. The M_w,slow dependence of 〈S²〉 obtained was favorably compared with this model with reasonable structural parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1179–1187, 2006     

Effect of formulated ingredients on rapidly disintegrating oral tablets prepared by the crystalline transition method

The aim of this article was to determine the optimal ingredients for the rapidly disintegrating oral tablets prepared by the crystalline transition method (CT method). The effect of ingredients (diluent, active drug substance and amorphous sugar) on the characteristics of the tablets was investigated. The ingredients were compressed and the resultant tablets were stored under various conditions. The oral disintegration time of the tablet significantly depended on diluents, due to differences in the penetration of a small amount of water in the mouth and the viscous area formed inside the tablet. The oral disintegration time was 10-30 s for tablets with a tensile strength of approximately 1 MPa, when erythritol, mannitol or xylitol was used as the diluent. The increase in the tensile strength of tablets containing highly water-soluble active drug substances during storage was as large as that of tablets without active drug substances, while the increase in the tensile strength of tablets containing low water-soluble active drug substances was small. It was therefore found that highly water-soluble active drug substances were more suitable for the formulation prepared by the CT method than low water-soluble active drug substances. Irrespective of the type of amorphous sugar (amorphous sucrose, lactose or maltose) used, the porosity of tablets with 1 MPa of tensile strength was 30-40%, and their oral disintegration time was 10-20 s. The optimal ingredients for rapidly disintegrating oral tablets with reasonable tensile strength and disintegration time were therefore determined from these results.     

Dicarboxylic degradation products of nonylphenol polyethoxylates. Determination and structural elucidation in water samples by solid-phase extraction and gas chromatography-mass spectrometry after methylation

A reliable method combining solid-phase extraction, derivatization and gas chromatography-chemical ionization mass spectrometry (GC-CI-MS) was developed for the measurement, in river and sewage effluent water, of four select model compounds of dicarboxylic metabolites (dm-CA(5-8)P1EC) and other dicarboxylic metabolites (CA(5-8)P1ECs) of nonylphenol polyethoxylates. These selected isomers were referred as dm-CA(5-8)P1ECs because they have an alpha,alpha-dimethyl configuration (expressed as "dm"), five to eight C atoms and a carboxyl group in the alkyl chain, and an ethoxy acetic acid group. The derivatization of terminal carboxyl groups was successful with (trimethylsilyl)diazomethane. The best extraction conditions were obtained using an Oasis HLB cartridge as a sorbent bed and 4 ml of MTBE/methanol (9:1, v/v) elution mixture. The method detection limits of 0.03-0.07 microg/l for dm-CA(5-8)P1ECs were attained in 500 ml pure water. The recovery was then evaluated for pure water, river and sewage effluent water samples. The high recoveries of typically >89% for each isomer indicated the high performance of the method. Although dm-CA(5-8)P1ECs were not detected in the collected water samples, 21 isomers of CA(5-8)P1ECs were identified by CI-MS and the tentative structures of six out of them were elucidated, mainly limited to the branch at alpha-C atom, by studying the EI-mass spectra. The relative concentrations of individual CA(5-8)P1EC metabolites were calculated based on dm-CA(5-8)P1ECs. The results showed that the main degradation on the nonyl chain occurred via the elimination of two carbon-units and the concentrations in Japan were much lower than those in Taiwan and Italy.     

Two significantly different conformations in crystal: formation of a molecular dimer governed by cation-π interactions

Two significantly different conformations were observed in crystal of 1, which form an unsymmetrical molecular dimer governed by cation-π interactions between a pyridinium cation and a phenyl ring, whereas compound 2 forms a head-to-tail type of dimer.     

Coaxial holographic data storage without recording the dc components

A technique of recovering the data pages from Fourier holograms recorded without the dc components is demonstrated theoretically and experimentally by use of a coaxial holographic storage system. A reconstructed image is obtained by adding a phase-modulated dc component of the signal beam on reading. The bit error rate of the reconstructed image is comparable with that for the hologram recorded with the dc component as well. Since high intensities of the dc components are not recorded in this technique, the dynamic range of the recording media can be saved, which potentially contributes to increasing the number of multiplexed holograms.