Fission Yeast CENP-C (Cnp3) Plays a Role in Restricting the Site of CENP-A Accumulation

The centromere is a chromosomal locus where a microtubule attachment site, termed kinetochore, is assembled in mitosis. In most eukaryotes, with the exception of holocentric species, each chromosome contains a single distinct centromere. A chromosome with an additional centromere undergoes successive rounds of anaphase bridge formation and breakage, or triggers a cell cycle arrest imposed by DNA damage and replication checkpoints. We report here a study in Schizosaccharomyces pombe to characterize a mutant (cnp3-1) in a gene encoding a homolog of mammalian centromere-specific protein, CENP-C. At the restrictive temperature 36 degrees , the Cnp3-1 mutant protein loses its localization at the centromere. In the cnp3-1 mutant, the level of the Cnp1 (a homolog of a centromere-specific histone CENP-A) also decreases at the centromere. Interestingly, the cnp3-1 mutant is prone to promiscuous accumulation of Cnp1 at non-centromeric regions, when Cnp1 is present in excess. Unlike the wild type protein, Cnp3-1 mutant protein is found at the sites of promiscuous accumulation of Cnp1, suggesting that Cnp3-1 may stabilize or promote accumulation of Cnp1 at non-centromeric regions. From these results, we infer the role of Cnp3 in restricting the site of accumulation of Cnp1 and thus to prevent formation of de novo centromeres

Low temperature ionic conductor: Ionic liquid incorporated within a metal-organic framework

Ionic liquids (ILs) show promise as safe electrolytes for electrochemical devices. However, the conductivity of ILs decreases markedly at low temperatures because of strong interactions arising between the component ions. Metal-organic frameworks (MOFs) are appropriate microporous host materials that can control the dynamics of ILs via the nanosizing of ILs and tunable interactions of MOFs with the guest ILs. Here, for the first time, we report on the ionic conductivity of an IL incorporated within a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (Zn(MeIM)2, H(MeIM) = 2-methylimidazole) as the IL and the MOF, respectively. While the ionic conductivity of bulk EMI-TFSA showed a sharp decrease arising from freezing, the EMI-TFSA@ZIF-8 showed no marked decrease because there was no phase transition. The ionic conductivity of EMI-TFSA@ZIF-8 was higher than that of bulk EMI-TFSA below 250 K. This result points towards a novel method by which to design electrolytes for electrochemical devices such as batteries that can operate at low temperatures

A significant change in selective adsorption behaviour for ethanol by flexibility control through the type of central metals in a metal-organic framework

Closed-open structural transformations in flexible metal-organic frameworks (MOFs) are of interest for potential applications such as separation, because of their complete selectivity for the adsorption of specific guest molecules. Here, we report the control of the adsorption behaviour in a series of flexible MOFs, (H2dab)[M2(ox)3] (H2dab = 1, 4-diammoniumbutane, M = Fe, Co, Ni, Zn, or Mg), having different central metals with analogous crystal structures. We found that a significant change in the selective adsorption behaviour for EtOH over MeCHO and MeCN is caused by the type of central metals, without changes in the crystal structures of all phases (except the Ni compound). A systematic study of adsorption measurements and structural analyses of the analogous MOFs reveals for the first time that the framework flexibility around the central metals of MOFs is truly related to the selective adsorption behaviour

Structure manufacturing of proton-conducting organic–inorganic hybrid silicophosphite membranes by solventless synthesis

We have developed a new class of proton-conducting organic–inorganic hybrid silicophosphite membranes, produced by ethanol condensation of organically modified alkoxysilanes and anhydrous vinylphosphonic acid under solventless, catalyst-free, low-temperature, one-pot conditions. The membranes synthesized in this study are crack-free, large, and flexible, and they exhibit good thermal stability up to intermediate temperatures (~218 °C). Structural analyses using [29]Si and [31]P nuclear magnetic resonance spectroscopy and infrared measurements revealed that ethanol condensation produced an inorganic alternating copolymer structure, Si–O–P, with a phosphole group, and successive polymerization between vinyl and/or methacryl groups enabled these structures to connect with each other. In this way, it is possible to achieve structure manufacturing of inorganic–organic networks. The proton conductivities of the hybrids are as high as 5.2 × 10[−3] S/cm at 85 °C under 80% relative humidity

Proton Conductivity Control by Ion Substitution in a Highly Proton-Conductive Metal–Organic Framework

Proton conductivity through two-dimensional (2-D) hydrogen-bonding networks within a layered metal–organic framework (MOF) (NH₄)₂(H₂adp)­[Zn₂(ox)₃]·3H₂O (H₂adp = adipic acid; ox = oxalate) has been successfully controlled by cation substitution. We synthesized a cation-substituted MOF, K₂(H₂adp)­[Zn₂(ox)₃]·3H₂O, where the ammonium ions in a well-defined hydrogen-bonding network are substituted with non-hydrogen-bonding potassium ions, without any apparent change in the crystal structure. We successfully controlled the proton conductivity by cleavage of the hydrogen bonds in a proton-conducting pathway, showing that the 2-D hydrogen-bonding networks in the MOF truly contribute to the high proton conductivity. This is the first example of the control of proton conductivity by ion substitution in a well-defined hydrogen-bonding network within a MOF

Selective Separation of Water, Methanol, and Ethanol by a Porous Coordination Polymer Built with a Flexible Tetrahedral Ligand

A novel porous coordination polymer, Cu^II(mtpm)­Cl₂ [mtpm = tetrakis­(<i>m</i>-pyridyloxy methylene)­methane], has been synthesized, and its crystal structure has been determined. Its adsorption isotherms for water, methanol, and ethanol are totally different from each other. It adsorbs water at low humidity and shows gate-open behavior for methanol, but it does not adsorb ethanol. This compound has the capacity to separate both methanol and water from bioethanol, which is a mixture of water, methanol, and ethanol

3D Coordination Polymer of Cd(II) with an Imidazolium-Based Linker Showing Parallel Polycatenation Forming Channels with Aligned Imidazolium Groups

A novel entangled architecture formed on solvothermal reaction of a imidazolium based bent ligand with Cd­(NO₃)₂, showing 1D channels decorated with imidazolium groups, is reported. The polymer, {[Cd₂(L)₃(DMF)­(NO₃)]­(DMF)₃(H₂O)₈}_<i>n</i> (<b>1</b>) (where H₂L = 1,3-bis­(4-carboxyphenyl)­imidazolium, DMF = dimethylformamide), shows an interesting 6,3-connected polycatenated structure with channels along the crystallographic <i>b</i>-axis occupied with large number of DMF and water molecules. On removal of these solvent molecules the compound maintains its overall structure. Proton conductivity investigation affords a proton conductivity of 1.3 × 10^–5 Scm^–1 at 25 °C and 98% RH when water molecules are introduced into the empty channels