Multienzymatic Sucrose Conversion into Fructose and Gluconic Acid through Fed-Batch and Membrane-Continuous Processes

Multienzymatic conversion of sucrose into fructose and gluconic acid was studied through fed-batch and continuous (in a membrane reactor) processes. The law of substrate addition (sucrose or glucose) for the fed-batch process which led to a yield superior to 80% was the decreasing linear type, whose feeding rate (?; L/h) was calculated through the equation: ? = ?_o ? k.t, where ?_o (initial feeding rate, L/h), k (linear addition constant, L/h ²), and t (reaction time, h). In the continuous process, the yield of conversion of sucrose (Y) was superior to 70% under the following conditions: dilution rate?=?0.33 h^?1, total duration of 15 h, pH 5.0, 37 °C and initial sucrose concentration of 64 g/L (Y?=?92%), 100 g/L (Y?=?83%), or 150 g/L (Y?=?76%).     

Calcium in the oxygen-evolving complex: structural and mechanistic role determined by X-ray spectroscopy

This review describes the results from X-ray Absorption Spectroscopy studies that have contributed to an understanding of the role of Ca in the photosynthetic water-oxidation reaction. The results include the first Mn, Ca and Sr X-ray spectroscopy studies using Ca or Sr-substituted PS II samples that established the presence of a MnCa heteronuclear structure and its orientation, and the most recent Sr X-ray spectroscopy study using biosynthetically prepared Sr-containing PS II in the various S-states that provide important insights into the requirement for Ca in the mechanism of the Mn(4)Ca catalytic center.     

Invasion inhibitors of human fibrosarcoma HT 1080 cells from the rhizomes of Zingiber cassumunar: structures of phenylbutanoids, cassumunols

The methanolic extract and its EtOAc-soluble fraction from the rhizomes of Zingiber cassumunar inhibited invasion of human fibrosarcoma HT 1080 cells. From the EtOAc-soluble fraction, eight new phenylbutanoids, cassumunols A-H, were isolated together with 30 known constituents. The structures of new phenylbutanoids were elucidated on the basis of chemical and physicochemical evidence. Principal constituents were examined the inhibitory effects on the invasion of HT 1080 cells. Among them, phlain I and III, (E)-1-(3,4-dimethoxyphenyl)buta-1,3-diene, (E)-1-(2,4,5-trimethoxyphenyl)buta-1,3-diene, and (-)-β-sesquiphellandrene showed anti-invasion effects. Interestingly, (E)-1-(2,4,5-trimethoxyphenyl)buta-1,3-diene [inhibition (%) 46.8 ± 7.2 (p<0.05) at 30 μM] significantly inhibited the invasion, and only a weak cytotoxic effect was observed.     

Tricalysionoside A, a megastigmane gentiobioside, sulfatricalysines A-F, and tricalysiosides X-Z, ent-kaurane glucosides, from the leaves of Tricalysia dubia

Further isolation work on the water-soluble fraction of a MeOH extract of Tricalysia dubia afforded one new megastigmane gentiobioside, named tricalysionoside A (1), and three sulfates, named sulfatricalysines A-C (2-4). Extensive isolation work on the 1-BuOH-soluble fraction of a MeOH extract of T. dubia yielded sulfatricalysines D-F (5-7) and three new ent-kaurane glucosides, named tricalysiosides X-Z (8-10). The structures of the new compounds were elucidated by analyses of one- and two-dimensional NMR spectroscopic data. The absolute stereochemistry of tricalysionoside A (1) was established by modified Mosher's method.     

Five non‐synonymous SNPs in the gene encoding human deoxyribonuclease I‐like 2 implicated in terminal differentiation of keratinocytes reduce or abolish its activity

Several non‐synonymous SNPs in the human deoxyribonuclease I‐like 2 (DNase 1L2) gene responsible for DNA degradation during terminal differentiation of epidermal keratinocytes have been identified. However, only limited population data are available, and furthermore the effect of these SNPs on the DNase 1L2 activity remains unknown. Genotyping of all of the 17 SNPs was performed using the PCR‐RFLP method in three ethnic groups including 14 different populations. A series of amino acid‐substituted DNase 1L2 corresponding to each SNP was expressed, and its activity was measured. All of the six non‐synonymous SNPs exhibited a mono‐allelic distribution, whereas the distribution of some SNPs other than exonic ones was ethnicity‐dependent. Each of the minor alleles in SNPs, p.Ala20Asp, p.Val104Leu, p.Asp197Ala, p.Glu274Lys and p.Asp287Asn, among the non‐synonymous SNPs produced low or no activity‐harbouring DNase 1L2. DNase 1L2 is well conserved, retaining full levels of enzymatic activity, with regard to these exonic SNPs in human populations. It seems plausible to assume that these SNPs affecting the activity may be one of the factors responsible for a genetic pre‐disposition for failure of differentiation‐associated cell death in various keratinocyte lineages, thereby leading to the development of parakeratosis. Our results may have clinical implications in relation to the pathogenesis of parakeratosis.     

Synthesis of 6-S-(5-Acetamido-3,5-Dideoxy-D-Glycero-α-D-Galacto-2-Nonulopyranosylonic Acid)-6-Thio-Hexopyranosides

The reaction of the sodium salt of methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-α-D-galacto-2-nonulo-pyranosonate with a variety of 6-bromo-6-deoxy-D-hexopyranosides, such as methyl 2,3,4-tri-O-acetyl-6-bromo-6-deoxy-α-D-glucopyranos-ide, -galactopyranoside, allyl 2,3,4-tri-O-acetyl-6-bromo-6-deoxy-β-D-glucopyranoside, and allyl 2-acetamido-3,4-di-O-acetyl-6-bromo-2,6-dideoxy-β-D-glucopyranoside, gave the corresponding (2→6)-linked disaccharides, α-glycosides of 2-thio-N-acetylneuraminic acid derivative in good yields. These disaccharides were converted, via O-deacetylation, followed by hydrolytic removal of the ester group, into the title compounds.     

Reactions of ruthenium complexes having pyridyl-containing ligands, 2-pyridinecarboxylato and 2,2'-bipyridine, with an azide ion: formation of nitrido-bridged diruthenium complexes

Reactions of ruthenium complexes having 2-pyridinecarboxylato and 2,2'-bipyridine ligands with sodium azide in alcohol afforded nitrido-bridged diruthenium complexes, [{Ru(OR)(pyca)(bpy)}2(mu-N)](+) (R = CH3, C2H5). Diruthenium complexes showed diamagnetic properties, a linear Ru-N-Ru coordination configuration, and two irreversible oxidation waves and two reversible reduction waves.     

Single-molecule magnetism properties of the first strontium-manganese cluster [SrMn14O11(OMe)3(O2CPh)18(MeCN)2

The preparation and properties of the first strontium-manganese molecular complex are described. The reaction of (NBu(n)4)[Mn4O2(O2CPh)9(H 2O)] (4Mn(III)) with Sr(ClO4)2 in MeCN/MeOH led to the isolation of [SrMn14O11(OMe)3(O2CPh)18(MeCN)2] ( 1; 13Mn(III), Mn(II)). The structure of 1 consists of two [Mn4O3(OMe)] cubane units attached to a central, near-planar, trinuclear [Mn3O4] unit, to which are also attached a Mn and a Sr above the plane and a [Mn2O(OMe)] rhomb below the plane. Peripheral ligation is provided by 18 bridging benzoate and two terminal MeCN groups. Variable-temperature and -field dc magnetization (M) data were collected in the 1.8-10 K and 0.1-4.0 T ranges and fit by matrix diagonalization methods to give S = 9/2, D = -0.50(5) cm(-1), and g = 1.88(10), where S is the ground-state spin and D is the axial zero-field splitting parameter. Magnetization versus dc field sweeps at various temperatures and scan rates exhibited hysteresis loops, confirming 1 to be a new single-molecule magnet. Because complex 1 is the initial molecular example of intimately associated Mn and Sr atoms, Sr EXAFS studies have been performed for the first time on a synthetic Sr-containing molecule. This has also allowed comparisons with the EXAFS data on the Sr-substituted water oxidizing complex (WOC) of Photosystem II (PS II), which contains a SrMn4 complex.     

Alkoxy-derived multiscale porous TiO<Subscript>2</Subscript> gels probed by ultra-small-angle X-ray scattering and small-angle X-ray scattering

Titania (TiO₂) monoliths with well-defined bicontinuous macropores and gel skeletons were prepared through the alkoxy-derived sol–gel process accompanied by spinodal decomposition, and the structural evolution during evaporation drying and heat treatment was probed by a combination of ultra-small-angle X-ray scattering and small-angle X-ray scattering. X-ray scattering profiles of wet and dried gels revealed that microporous structures related to the existence of primary particles are present in the gel skeletons at the wet stage and are preserved during drying. Additionally, it is found that the primary particles swollen in the wet condition are dried to compact aggregates to produce the smooth surface of gel skeletons. Upon heating at 400 °C, the particle–particle correlation associated with regularity of mesostructures is enhanced. From nitrogen adsorption–desorption measurements, the average pore size is less than 1 nm in the dried gel and increases to 3.1 nm by the heat treatment. Homogeneous growth of primary particles due to interparticle-polycondensation reaction is responsible for the increased size and uniform distribution of mesopores in the heat-treated gel.     

Activation of hydrocarbons on acidic zeolites: superior selectivity of methylation of ethene with methanol to propene on weakly acidic catalysts

The study of methylation of ethene with methanol to propene over MFI zeolites with different heteroatoms has found that an efficient catalyst with weak acidities prevented the side reactions related with the formation of ethene oligomers from occurring, as evidenced by in situ IR spectroscopy, leading to superior propene selectivity in the product distribution.