Chemoenzymatic synthesis of uridine diphosphate-GlcNAc and uridine diphosphate-GalNAc analogs for the preparation of unnatural glycosaminoglycans

Eight N-acetylglucosamine-1-phosphate and N-acetylgalactosamine-1-phosphate analogs have been synthesized chemically and were tested for their recognition by the GlmU uridyltransferase enzyme. Among these, only substrates that have an amide linkage to the C-2 nitrogen were transferred by GlmU to afford their corresponding uridine diphosphate(UDP)-sugar nucleotides. Resin-immobilized GlmU showed comparable activity to nonimmobilized GlmU and provides a more facile final step in the synthesis of an unnatural UDP-donor. The synthesized unnatural UDP-donors were tested for their activity as substrates for glycosyltransferases in the preparation of unnatural glycosaminoglycans in vitro. A subset of these analogs was useful as donors, increasing the synthetic repertoire for these medically important polysaccharides.     

Ultraviolet-Laser-Induced Crystallization of Sol-Gel Derived Inorganic Oxide Films

Structural changes stimulated by ultraviolet (UV) laser irradiations of sol-gel derived inorganic oxide films were investigated. Dried gel films of TiO₂, Nb₂O₅, Ta₂O₅, SrTiO₃ and Pb(Zr _x Ti_1–x )O₃ (PZT) were found to be crystallized by the laser irradiation. On the other hand, the photo-induced change in gel films of BaTiO₃, LiNbO₃ and LiTaO₃ was not observed although the laser beams were absorbed in the films. These sol-gel films were thermally crystallized at almost the same temperature around 600–700°C except TiO₂. Thus, the UV-laser-induced crystallization is not directly ascribed to a simple thermal effect with the irradiation. Photochemical properties of the cations are assumed to be important for the change in sol-gel films.     

Water sorption,glass transition,and freeze-concentrated glass-like transition properties of calcium maltobionate–maltose mixtures

Journal of Thermal Analysis and Calorimetry - The water sorption, glass transition, and freeze-concentrated thermal transition properties of calcium maltobionate (MBCa)–maltose mixtures were...     

Identification of aluminum species in an aluminum-accumulating plant, hydrangea (Hydrangea macrophylla), by electrospray ionization mass spectrometry.

The use of electrospray ionization mass spectrometry (ESI-MS) in negative ion mode was investigated as a direct probe for identifying Al species in Al-accumulating hydrangea (Hydrangea macrophylla) samples. Cell sap solutions of hydrangea leaves were purified using Sephadex G-10 liquid chromatography and each fraction was analyzed using ESI-MS and ESI-MS/MS to identify Al species. In hydrangea leaves, a 1:1 Al-citrate complex was found as [AlH(-1)cit](-) (m/z 215), where H(3)cit denotes citric acid. This result is consistent with that of Ma et al. who used (27)Al-NMR.     

Diffusion of linear aliphatic esters in polyethylene as a function of chain length of the esters,pressure and temperature

Diffusion of linear aliphatic mono- and diesters (C _N ) havingN main chain atoms (N=13–68) in bulk medium-density polyethylene (MDPE) has been studied under hydrostatic pressures up to 2500 bar at temperatures between 60°C and 125°C. Three triglycerides, phenyl stearate, and p-aminoazobenzene (pAAB, 80°C) as the diffusants and low-density (LDPE) and high-density (HDPE) polyethylenes as polyethylene substrate were used for comparison. Diffusion coefficientD was determined from concentration distribution of the diffusants through stacked PE sheets as substrate. Regarding the linear esters at 90°C, the relationshipD N holds at constant pressures. Under the atmospheric pressure, became –2.10 in accordance with de Gennes's proposal (1971)D N ^–2 as well as with the experimental results reported by Klein and Briscoe (1979) forN larger than 30.D's for the glycerides deviate from the relationshipD N ^–2 toward the smaller values by comparison at the sameN. The exponent is pressure-dependent. It decreases with increasing pressure according to =–2.10–0.000942P, whereP is measured by the unit of bar. Plots of lnD vsP for all the diffusants show linear relationships with negative slopes, from which activation volume for the diffusion V was calculated. At 90°C, V increases slowly with increasingN and increasingV _Ki, the intrinsic molecular volume of the diffusant, from 39.3 cm³/mol for ethyl caprate (C ₁₃,V _Ki=136 cm³/mol) to 76.8 cm³/mol for behenyl behenate (C₄₅,V _Ki=466 cm³/mol). Observed V s are explainable on the basis of the reptation mode of the chain molecule diffusion. V s for C₂₅ and C₄₅ are found to increase with increasing degree of crystallinity where MDPE, heat-treated MDPE, LDPE, and HDPE were used. The results obtained by varying temperature are as follows. V for C₄₅ was always found to be larger than C₂₅. Both decreased linearly with increasing temperature, giving two linear lines with different slopes whose extensions intersected at 132°C, the melting point of the MDPE, where the difference in V disappeared. The apparent activation energiesE _Ds for the diffusion of C₂₅ and C₄₅ increased linearly with increasing pressure, whose slopes are explainable according toE _D=E ₀+PV [1-(dln V /dlnT) _P ].     

Synthesis of [6]helicene-based sulfonic acid,sulfonamide, and disulfonimides

The synthesis of helically chiral [6]helicene-based sulfonic acid and sulfonamide from enantiomerically pure 1-acetylthio-5,6,9,10-tetrahydro[6]helicene is reported. The first helically chiral disulfonimides were developed as a synthetic application of [6]helicene-based sulfonamide. This new class of organocatalysts was tested in an asymmetric Mukaiyama aldol reaction to obtain up to quantitative yields and enantioselectivities up to 24%.     

Biochemical, molecular genetic, and structural analyses of the staphylococcal nucleoid.

The nucleoid structure of an important human pathogen, Staphylococcus aureus, was dissected by atomic force microscopy (AFM). The nucleoids dispersed on a cover glass consisted of fibrous units with two different widths of 40 and 80 nm, a feature shared with those of Escherichia coli. On the other hand, cells exposed to an oxidative stress exhibited clogged nucleoids. A knock-out of mrgA (metallo regulated genes A) encoding a staphylococcal homolog of the nucleoid compaction factor (E. coli Dps) eliminated the compaction response to the oxidative stress and reduced the susceptibilities to H2O2 and UV irradiation. We also observed that the negative supercoiling of plasmids is increased by the oxidative stress. A possible interrelation between the helical density and the nucleoid compaction is discussed in relation to the oxidative stress response.