Physicochemical functionality of chimeric isomaltomegalosaccharides with α-(1→4)-glucosidic segments of various lengths

Isomaltomegalosaccharide (IMS) is a long chimeric glucosaccharide composed of alpha-(1-+ 6)-and alpha-(1-+ 4)-linked segments at nonreducing and reducing ends, respectively; the hydrophilicity and hydrophobicity of these segments are expected to lead to bifunctionality. We enzymatically synthesized IMS with average degrees of polymerization (DPs) of 15.8, 19.3, and 23.5, where alpha-(1-+ 4)-segments had DPs of 3, 6, and 9, respectively. IMS exhibited considerably higher water solubility than maltodextrin because of the alpha-(1-+ 6)-segment and an identical resistance to thermal degradation as short dextran. Interaction of IMS with a fluorescent probe of 2-p- toluidinylnaphthalene-6-sulfonate demonstrated that IMS was more hydrophobic than maltodextrin, where the degree of hydrophobicity increased as DP of alpha-(1-+ 4)-segment increased (9 > 6 > 3). Fluorescent pyreneestimating polarity of IMS was found to be similar to that of methanol or 1-butanol. The bifunctional IMS enhanced the water solubility of quercetin-3-O-glucoside and quercetin: the solubilization of less-soluble bioactive substances is beneficial in carbohydrate industry

A practical approach to producing isomaltomegalosaccharide using dextran dextrinase from Gluconobacter oxydans ATCC 11894

Dextran dextrinase (DDase) catalyzes formation of the polysaccharide dextran from maltodextrin. During the synthesis of dextran, DDase also generates the beneficial material isomaltomegalosaccharide (IMS). The term megalosaccharide is used for a saccharide having DP=10-100 or 10-200 (DP, degree of polymerization). IMS is a chimeric glucosaccharide comprising alpha-(1 -> 6)- and alpha-(1 -> 4)-linked portions at the nonreducing and reducing ends, respectively, in which the alpha-(1 -> 4)-glucosyl portion originates from maltodextrin of the substrate. In this study, IMS was produced by a practical approach using extracellular DDase (DDext) or cell surface DDase (DDsur) of Gluconobacter oxydans ATCC 11894. DDsur was the original form, so we prepared DDext via secretion from intact cells by incubating with 0.5% G6/G7 (maltohexaose/maltoheptaose); this was followed by generation of IMS from various concentrations of G6/G7 substrate at different temperatures for 96 h. However, IMS synthesis by DDext was limited by insufficient formation of alpha-(1 -> 6)-glucosidic linkages, suggesting that DDase also catalyzes elongation of alpha-(1 -> 4)-glucosyl chain. For production of IMS using DDsur, intact cells bearing DDsur were directly incubated with 20% G6/G7 at 45 degrees C by optimizing conditions such as cell concentration and agitation efficiency, which resulted in generation of IMS (average DP =14.7) with 61% alpha-(1 -> 6)-glucosyl content in 51% yield. Increases in substrate concentration and agitation efficiency were found to decrease dextran formation and increase IMS production, which improved the reaction conditions for DDext. Under modified conditions (20% G6/G7, agitation speed of 100 rpm at 45 degrees C), DDext produced IMS (average DP =14.5) with 65% alpha-(1 -> 6)-glucosyl content in a good yield of 87%

Hydrogen-Bonding Assembly of Coordination Polymers Showing Reversible Dynamic Solid-State Structural Transformations

We herein report the synthesis, single-crystal structures of coordination polymers, and structural transformations of complexes employing 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile (tdpd2−) and pyrazine (pyz) as bridging ligands. {[M(H2O)4(pyz)][M(tdpd)2(pyz)]·6(H2O)}n, [1·10H2O and 2·10H2O where M = Co (1) and Zn (2)], consists of two types of crystallographically independent one-dimensional (1D) structures packed together. One motif, [M(tdpd)2(pyz)]2− (A), is an anionic infinite pyz bridged 1D array with chelating tdpd2− ligands, and the other motif is a cationic chain, [M(H2O)4(pyz)]2+ (B), which is decorated with four terminal water molecules. The 1D arrays (A) and (B) are arranged in parallel by multi-point hydrogen-bonding interactions in an alternate (A)(B)(A)(B) sequence extending along the c-axis. Both compounds exhibit structural transformations driven by thermal dehydration processes around 350 K to give partially dehydrated forms, 1·2H2O and 2·2H2O. The structural determination of the partially dehydrated form, 2·2H2O, reveals a solid-state structural transformation from a 1D chain structure to a two-dimensional (2D) coordination sheet structure, [Zn2(tdpd)2(H2O)2(pyz)]n (2·2H2O). Further heating to 500 K yields the anhydrous form 2. While the virgin samples of 1·10H2O and 2·10H2O crystallize in different crystal systems, powder X-ray diffraction (PXRD) measurements of the dehydrated forms, 1·2H2O and 2·2H2O, are indicative of the same structure. The structural transformation is irreversible for 1·10H2O at ambient conditions. On the other hand, compound 2·10H2O shows a reversible structural change. The solid-state structural transformation for 1·10H2O was also confirmed by monitoring in-situ magnetic susceptibility, which is consistent with other thermally-induced measurements

RDF-Based Integration with SPARQL Building System for Life Science Database Archive

Abstract. The Life Science Database Archive (LSDB Archive, https://dbarchive.biosciencedbc.jp/ ) is a service to collect, preserve and provide databases generated by life-science researchers in Japan. As of September 2015, the LSDB Archive includes 103 databases and all the databases can be downloadable with appropriate licenses and metadata. Although a simple keyword search tool is available for the databases, more flexible retrieval system to obtain relevant data from heterogeneous databases is required. Therefore, we first converted the databases into RDF datasets, uploaded in a triple store. Then, we developed a prototype of retrieval system using SPARQL Builder. Because SPARQL Builder assists users in writing queries, the prototype enables users without knowledge of RDF to access the datasets

Side-chain engineering in a thermal precursor approach for efficient photocurrent generation

An ideal active-layer compound for bulk-heterojunction (BHJ) organic photovoltaic devices (OPVs) can assemble upon deposition to form the effective π-π stacking that facilitates exciton diffusion and charge-carrier transport. It is also expected to possess high-enough miscibility for forming sufficient heterojunctions to ensure efficient charge separation. However, these characteristics are often not compatible in organic small-molecule semiconductors: compounds endowed with rich self-π-π interaction capacity tend to be poor in miscibility, or maybe even insoluble in extreme cases. Herein, we postulate that a thermal precursor approach can serve as a way out of this dilemma, provided that molecules are properly engineered. This work evaluates a series of diketopyrrolopyrrole (DPP)-tetrabenzoporphyrin (BP) conjugates named Cn-DPP-BP (n = 4, 6, 8 or 10 depending on the length of alkyl groups on the DPP unit) as a p-type material in BHJ OPVs. These compounds are strongly aggregating and insoluble, thus processed via the thermal precursor approach in which the corresponding soluble derivatives (Cn-DPP-CP) are solution-processed into thin films and then converted to the target materials by in situ thermal reactions. The comparative study shows that the short-circuit current density largely depends on the length of alkyl substituents, ranging from 0.88 mA cm-2 with C10-DPP-BP to 15.2 mA cm-2 with C4-DPP-BP. Investigation into the structure of active layers through fluorescence-decay analysis, atomic-force microscopy, and two-dimensional grazing-incidence wide-angle X-ray diffractometry indicates that the introduction of shorter alkyl chains positively affects the miscibility and molecular orientation in BHJ layers. This trend is not fully parallel to those observed in the BHJ systems prepared through conventional solution techniques, and will provide a unique basis for devising a new class of high-performance OPV materials