Tuning microcavities in thermally rearranged polymer membranes for CO2 capture

Microporous materials have a great importance in catalysis, delivery, storage and separation in terms of their performance and efficiency. Most microporous materials are comprised of inorganic frameworks, while thermally rearranged (TR) polymers are a microporous organic polymer which is tuned to optimize the cavity sizes and distribution for difficult separation applications. The sub-nano sized microcavities are controlled by in situ thermal treatment conditions which have been investigated by positron annihilation lifetime spectroscopy (PALS). The size and relative number of cavities increased from room temperature to 230 °C resulting in improvements in both permeabilities and selectivities for H(2)/CO(2) separation due to the significant increase of gas diffusion and decrease of CO(2) solubility. The highest performance of the well-tuned TR-polymer membrane was 206 Barrer for H(2) permeability and 6.2 of H(2)/CO(2) selectivity, exceeding the polymeric upper bound for gas separation membranes.     

Effect of the rutile content on the photovoltaic performance of the dye-sensitized solar cells composed of mixed-phase TiO2 photoelectrodes

The effect of the rutile content on the photovoltaic performance of dye-sensitized solar cells (DSSCs) composed of mixed-phase TiO(2) photoelectrode has been investigated. The mixed-phase TiO(2) particles with varied amounts of rutile, relative to anatase phase, are synthesized by an in situ method where the concentration of sulfate ion is used as a phase-controlling parameter in the formation of TiO(2) using TiCl(4) hydrolysis. The surface area (S(BET)) varies from 33 (pure rutile) to 165 (pure anatase) m(2) g(-1). Generally, both the current density (J(sc)) and photo-conversion efficiency (η) decrease as the rutile content increases. The incorporation of rod-shaped rutile particles causes low uptake of dye due to the reduced surface area, as well as slow electron transport in less efficiently-stacked structure. However, maximum J(sc) (14.63 mA cm(-2)) and η (8.69%) appear when relatively low rutile content (16%) is employed. The reported synergistic effect by the efficient interparticle electron transport from rutile to anatase seems to overbalance the decrease of surface area when small amount of rutile particles is incorporated.     

Synthesis, X-ray structures, and controlled ring opening polymerization behavior of l-lactide using titanium complexes chelated by tetradentate diamine-diethanolate ligand

The synthesis and characterization of LTi(O-i-Pr)(2) (1) and LTiCl(2) (2) complexes containing a new [ONNO]-type tetradentate diamine-diethanolate ligand such as (HOCMe(2)CH(2)NMeCH(2)CH(2)NMeCH(2)CMe(2)OH) (LH(2)) was achieved. Single-crystal X-ray analyses revealed that monomeric complexes 1 and 2 had pseudo-C(2) and pseudo-C(1) symmetric distorted octahedral geometry, respectively. Interestingly, complex 1 has fac-fac geometry for tetradentate L around a Ti centre in both solid and solution, whereas complex 2 has different geometry in solid (mer-fac, C(1)) and solution (fac-fac, C(2)). They are effective catalysts for the controlled ring opening polymerization of l-lactide, as shown by the linearity of the number average of the molecular weight of polylactides versus conversion, as well as narrow PDI values.     

Tyrosine nitration affects thymidylate synthase properties

Highly purified preparations of thymidylate synthase, isolated from calf thymus, and L1210 parental and FdUrd-resistant cells, were found to be nitrated, as indicated by a specific reaction with anti-nitro-tyrosine antibodies, suggesting this modification to appear endogenously in normal and tumor tissues. Each human, mouse and Ceanorhabditis elegans recombinant TS preparation, incubated in vitro in the presence of NaHCO(3), NaNO(2) and H(2)O(2) at pH 7.5, underwent tyrosine nitration, leading to a V(max)(app) 2-fold lower following nitration of 1 (with human or C. elegans TS) or 2 (with mouse TS) tyrosine residues per monomer. Enzyme interactions with dUMP, meTHF or 5-fluoro-dUMP were not distinctly influenced. Nitration under the same conditions of model tripeptides of a general formula H(2)N-Gly-X-Gly-COOH (X = Phe, Tyr, Trp, Lys, Arg, His, Ser, Thr, Cys, Gly), monitored by NMR spectroscopy, showed formation of nitro-species only for H-Gly-Tyr-Gly-OH and H-Gly-Phe-Gly-OH peptides, the chemical shifts for nitrated H-Gly-Tyr-Gly-OH peptide being in a very good agreement with the strongest peak found in (15)N-(1)H HMBC spectrum of nitrated protein. MS analysis of nitrated human and C. elegans proteins revealed several thymidylate synthase-derived peptides containing nitro-tyrosine (at positions 33, 65, 135, 213, 230, 258 and 301 in the human enzyme) and oxidized cysteine (human protein Cys(210), with catalytically critical Cys(195) remaining apparently unmodified) residues.     

Kinetically controlled one-pot formation of DEFGH-rings of type B physalins through domino-type transformations

The characteristic DEFGH-ring system of type B physalins has been synthesized by means of a one-pot procedure incorporating domino-type ring transformations. Unexpectedly, we found that introduction of an α-hydroxyester functionality at C17 in ring E allowed the key 7-endo oxy-Michael reaction to proceed. Originally this was thought to be an unfavored process. This afforded the desired caged ring system to be formed in a kinetically controlled manner. Consecutive treatment with AcOH at 100 °C furnished the DEFGH-ring system in one pot.     

Simulation of the opening and closing of Hsp70 chaperones by coarse-grained molecular dynamics

Heat-shock proteins 70 (Hsp70s) are key molecular chaperones which assist in the folding and refolding/disaggregation of proteins. Hsp70s, which consist of a nucleotide-binding domain (NBD, consisting of NBD-I and NBD-II subdomains) and a substrate-binding domain [SBD, further split into the β-sheet (SBD-β) and α-helical (SBD-α) subdomains], occur in two major conformations having (a) a closed SBD, in which the SBD and NBD domains do not interact, (b) an open SBD, in which SBD-α interacts with NBD-I and SBD-β interacts with the top parts of NBD-I and NBD-II. In the SBD-closed conformation, SBD is bound to a substrate protein, with release occurring after transition to the open conformation. While the transition from the closed to the open conformation is triggered efficiently by binding of adenosine triphosphate (ATP) to the NBD, it also occurs, although less frequently, in the absence of ATP. The reverse transition occurs after ATP hydrolysis. Here, we report canonical and multiplexed replica exchange simulations of the conformational dynamics of Hsp70s using a coarse-grained molecular dynamics approach with the UNRES force field. The simulations were run in the following three modes: (i) with the two halves of the NBD unrestrained relative to each other, (ii) with the two halves of the NBD restrained in an "open" geometry as in the SBD-closed form of DnaK (2KHO), and (iii) the two halves of NBD restrained in a "closed" geometry as in known experimental structures of ATP-bound NBD forms of Hsp70. Open conformations, in which the SBD interacted strongly with the NBD, formed spontaneously during all simulations; the number of transitions was largest in simulations carried out with the "closed" NBD domain, and smallest in those carried out with the "open" NBD domain; this observation is in agreement with the experimentally-observed influence of ATP-binding on the transition of Hsp70's from the SBD-closed to the SBD-open form. Two kinds of open conformations were observed: one in which SBD-α interacts with NBD-I and SBD-β interacts with the top parts of NBD-I and NBD-II (as observed in the structures of nucleotide exchange factors), and another one in which this interaction pattern is swapped. A third type of motion, in which SBD-α binds to NBD without dissociating from SBD-β was also observed. It was found that the first stage of interdomain communication (approach of SBD-β, to NBD) is coupled with the rotation of the long axes of NBD-I and NBD-II towards each other. To the best of our knowledge, this is the first successful simulation of the full transition of an Hsp70 from the SBD-closed to the SBD-open conformation.     

Search for bioactive compounds from Cantharellus cibarius

Ground fruit bodies of Cantharellus cibarius (chanterelle) were extracted with dichloromethane and subjected to CC followed by preparative HPLC, which led to the isolation of glycerol 1,2- and 1,3-dilinoleates and glycerol tridehydrocrepenynate. Extraction of C. cibarius fruit bodies with ethanol or methanol afforded fatty acid ethyl or methyl esters as a result of esterification/transesterification reactions. Insecticidal activity of the isolated glycerides and esters was much lower than that of the crude extracts and chromatographic fractions suggesting a synergistic effect of some of the compounds present in the mixture.     

Supersymmetric gauge theories on the five-sphere

We construct Euclidean 5d supersymmetric gauge theories on the five-sphere with vector and hypermultiplets. The SUSY transformation and the action are explicitly determined from the standard Noether procedure as well as from off-shell supergravity. Using localization techniques, the path-integral is shown to be restricted to the integration over a generalization of instantons on CP²${\mathbb{CP}}^2$ and the Coulomb moduli.     

Homophilic interaction of the L1 family of cell adhesion molecules

Homophilic interaction of the L1 family of cell adhesion molecules plays a pivotal role in regulating neurite outgrowth and neural cell networking in vivo. Functional defects in L1 family members are associated with neurological disorders such as X-linked mental retardation, multiple sclerosis, low-IQ syndrome, developmental delay, and schizophrenia. Various human tumors with poor prognosis also implicate the role of L1, a representative member of the L1 family of cell adhesion molecules, and ectopic expression of L1 in fibroblastic cells induces metastasis-associated gene expression. Previous studies on L1 homologs indicated that four N-terminal immunoglobulin-like domains form a horseshoe-like structure that mediates homophilic interactions. Various models including the zipper, domain-swap, and symmetry-related models are proposed to be involved in structural mechanism of homophilic interaction of the L1 family members. Recently, cryo-electron tomography of L1 and crystal structure studies of neurofascin, an L1 family protein, have been performed. This review focuses on recent discoveries of different models and describes the possible structural mechanisms of homophilic interactions of L1 family members. Understanding structural mechanisms of homophilic interactions in various cell adhesion proteins should aid the development of therapeutic strategies for L1 family cell adhesion molecule-associated diseases.     

Gene mapping study for constitutive skin color in an isolated Mongolian population

To elucidate the genes responsible for constitutive human skin color, we measured the extent of skin pigmentation in the buttock, representative of lifelong non-sun-exposed skin, and conducted a gene mapping study on skin color in an isolated Mongolian population composed of 344 individuals from 59 families who lived in Dashbalbar, Mongolia. The heritability of constitutive skin color was 0.82, indicating significant genetic association on this trait. Through the linkage analysis using 1,039 short tandem repeat (STR) microsatellite markers, we identified a novel genomic region regulating constitutive skin color on 11q24.2 with an logarithm of odds (LOD) score of 3.39. In addition, we also found other candidate regions on 17q23.2, 6q25.1, and 13q33.2 (LOD ≥ 2). Family-based association tests on these regions with suggestive linkage peaks revealed ten and two significant single nucleotide polymorphisms (SNPs) on the linkage regions of chromosome 11 and 17, respectively. We were able to discover four possible candidate genes that would be implicated to regulate human skin color: ETS1, UBASH3B, ASAM, and CLTC.