@article {1436, title = {Glycosynthase-based synthesis of xylo-oligosaccharides using an engineered retaining xylanase from Cellulomonas fimi}, journal = {Organic \& Biomolecular Chemistry}, volume = {4}, number = {10}, year = {2006}, note = {ISI Document Delivery No.: 041NHTimes Cited: 20Cited Reference Count: 39}, pages = {2025-2032}, type = {Article}, abstract = {Glycosynthases are synthetic enzymes derived from retaining glycosidases in which the catalytic nucleophile has been replaced. The mutation allows irreversible glycosylation of sugar acceptors using glycosyl fluoride donors to afford oligosaccharides without any enzymatic hydrolysis. Glycosynthase technology has proven fruitful for the facile synthesis of useful oligosaccharides, therefore the expansion of the glycosynthase repertoire is of the utmost importance. Herein, we describe for the first time a glycosynthase, derived from a retaining xylanase, that synthesizes a range of xylo-oligosaccharides. The catalytic domain of the retaining endo-1,4-beta-xylanase from Cellulomonas fimi (CFXcd) was successfully converted to the corresponding glycosynthase by mutation of the catalytic nucleophile to a glycine residue. The mutant enzyme (CFXcd-E235G) was found to catalyze the transfer of a xylobiosyl moiety from alpha-xylobiosyl fluoride to either p-nitrophenyl beta-xylobioside or benzylthio beta-xylobioside to afford oligosaccharides ranging in length from tetra- to dodecasaccharides. These products were purified by high performance liquid chromatography in greater than 60\% combined yield. H-1 and C-13 NMR spectroscopic analyses of the isolated p-nitrophenyl xylotetraoside and p-nitrophenyl xylohexaoside revealed that CFXcd-E235G catalyzes both the regio- and stereo-selective synthesis of xylo-oligosaccharides containing, exclusively, beta-(1 {\textendash}> 4) linkages.}, keywords = {4-GLYCANASE, BETA-1, DIRECTED EVOLUTION, EFFICIENT SYNTHESIS, ENZYMATIC-SYNTHESIS, GLYCOSIDASES, MASS-SPECTROMETRY, SPECIFICITY, SUBSTRATE, TRANSGLYCOSYLATION, XYLOOLIGOSACCHARIDES}, isbn = {1477-0520}, url = {://000237462400022}, author = {Kim, Y. W. and Fox, D. T. and Hekmat, O. and Kantner, T. and McIntosh, L. P. and Warren, R. A. J. and Withers, S. G.} } @article {896, title = {Inhibition of Chk1 by the G(2) DNA damage checkpoint inhibitor isogranulatimide}, journal = {Molecular Cancer Therapeutics}, volume = {3}, number = {10}, year = {2004}, note = {ISI Document Delivery No.: 862KBTimes Cited: 40Cited Reference Count: 40}, month = {Oct}, pages = {1221-1227}, type = {Article}, abstract = {Inhibitors of the G(2) DNA damage checkpoint can selectively sensitize cancer cells with mutated p53 to killing by DNA-damaging agents. Isogranulatimide is a G2 checkpoint inhibitor containing a unique indole/maleimide/ imidazole skeleton identified in a phenotypic cell-based screen; however, the mechanism of action of isogranulatimide is unknown. Using natural and synthetic isogranulatimide analogues, we show that the imide nitrogen and a basic nitrogen at position 14 or 15 in the imidazole ring are important for checkpoint inhibition. Isogranulatimide shows structural resemblance to the aglycon of UCN-01, a potent bisindolemaleimide inhibitor of protein kinase Cbeta (IC50, 0.001 mumol/L) and of the checkpoint kinase Chk1 (IC50, 0.007 mumol/L). In vitro kinase assays show that isogranulatimide inhibits Chk1 (IC50, 0.1 mumol/L) but not protein kinase Cbeta. Of 13 additional protein kinases tested, isogranulatimide significantly inhibits only glycogen synthase kinase-3beta (IC50, 0.5 mumol/L). We determined the crystal structure of the Chk1 catalytic domain complexed with isogranulatimicle. Like UCN-01, isogranulatimide binds in the ATP-binding pocket of Chk1 and hydrogen bonds with the backbone carbonyl oxygen of Glu(85) and the amide nitrogen Of Cys(87). Unlike UCN-01, the basic N15 of isogranulatimide interacts with Glu(17), causing a conformation change in the kinase glycine-rich loop that may contribute importantly to inhibition. The mechanism by which isogranulatimide inhibits Chk1 and its favorable kinase selectivity profile make it a promising candidate for modulating checkpoint responses in tumors for therapeutic benefit.}, keywords = {7-HYDROXYSTAUROSPORINE UCN-01, ACTIVATION, CANCER, CELL-CYCLE, DEPENDENT PROTEIN-KINASE, IDENTIFICATION, MECHANISMS, PHOSPHORYLATION, SPECIFICITY, SUBSTRATE}, isbn = {1535-7163}, url = {://000224488400006}, author = {Jiang, X. X. and Zhao, B. G. and Britton, R. and Lim, L. Y. and Leong, D. and Sanghera, J. S. and Zhou, B. B. S. and Piers, E. and Andersen, R. J. and Roberge, M.} } @article {988, title = {Surface-induced ordering of nematics in an external field: The strong influence of tilted walls}, journal = {Physical Review Letters}, volume = {92}, number = {18}, year = {2004}, note = {ISI Document Delivery No.: 818XNTimes Cited: 8Cited Reference Count: 19}, month = {May}, pages = {4}, type = {Article}, abstract = {Microscopic theory is used to investigate surface-induced order in a model nematic subjected to an external orienting field. The wall-particle interaction tends to orient particles perpendicular to the surface. It is shown that if the wall is tilted at similar to45degrees to the field, the reorientational effects can be an order of magnitude larger than those observed for perpendicular or parallel orientations. The surprising observation is associated with the breaking of a particular bulk symmetry. A possible practical application of the tilted geometry is briefly discussed.}, keywords = {CONTACT, FLUID, LIQUID-CRYSTALS, ORNSTEIN-ZERNIKE EQUATION, PHASE, SUBSTRATE, TRANSITIONS}, isbn = {0031-9007}, url = {://000221277900033}, author = {Sokolovska, T. G. and Sokolovskii, R. O. and Patey, G. N.} } @article {653, title = {Synthesis of poly(N,N-dimethylacrylamide) brushes from charged polymeric surfaces by aqueous ATRP: Effect of surface initiator concentration}, journal = {Macromolecules}, volume = {36}, number = {3}, year = {2003}, note = {ISI Document Delivery No.: 643NUTimes Cited: 49Cited Reference Count: 34}, month = {Feb}, pages = {591-598}, type = {Article}, abstract = {We have synthesized polystyrene shell latex (PSL) surfaces with different initiator concentrations by changing the feed ratio of styrene to 2-(methyl-2{\textquoteright}-chloropropionato)ethyl acrylate (HEACl) in a series of shell-growth copolymerization reactions. Surfaces were characterized by conductometric titration of saponified and nonsaponified functionalized PSL to give the surface charge and initiator concentrations accessible to aqueous reagents and by H-1 NMR methods. Poly(N,N-dimethylacrylamide) brushes were grafted from the functionalized surfaces by aqueous atom transfer radical polymerization and the dependence of molecular weight and chain density determined as a function of monomer concentration, ligand type, and surface initiator concentration by analyzing the chains cleaved from the PSL by saponification. M. varies linearly with monomer concentration for most systems, and grafting density is roughly independent of monomer concentration except at the highest initiator concentration. Very high molecular weights were obtained at low initiator concentration, up to M-n similar to 1.2 x 10(6) with M-w/M-n < 1.3; chain separations down to 1.1 mn and brush thicknesses to similar to800 nm were found. Grafting density varies as (initiator surface concentration)(2.6). The surface charge density also varies among the latexes synthesized and seems to play a role in this strong dependence on surface initiator concentration, perhaps by partially immobilizing the positively charged catalyst complex.}, keywords = {ADSORPTION, SELF-ASSEMBLED MONOLAYERS, SUBSTRATE, TRANSFER RADICAL POLYMERIZATION}, isbn = {0024-9297}, url = {://000180868000015}, author = {Kizhakkedathu, J. N. and Brooks, D. E.} } @article {5130, title = {Arsenicals inhibit thioredoxin reductase in cultured rat hepatocytes}, journal = {Chemical Research in Toxicology}, volume = {14}, number = {3}, year = {2001}, note = {ISI Document Delivery No.: 415LTTimes Cited: 86Cited Reference Count: 46}, month = {Mar}, pages = {305-311}, type = {Article}, abstract = {Thioredoxin reductase (TR), an NADPH-dependent flavoenzyme that catalyzes the reduction of many disulfide-containing substrates, plays an important role in the cellular response to oxidative stress. Trivalent arsenicals, especially methyl As that contains trivalent arsenic (MAsIII), are potent noncompetitive inhibitors of TR purified from mouse liver. Because MAsIII is produced in the biomethylation of As, it was postulated that the extent of inhibition of TR in cultured rat hepatocytes would correlate with the intracellular concentration of methyl As. Exposure of cultured hepatocytes to inorganic As-III (iAs(III)), MAsIII, or aurothioglucose (ATG, a competitive inhibitor of TR activity) for 30 min caused a concentration-dependent reduction in TR activity. The estimated IC50 was much greater than 100 muM for iAS(III), similar to 10 muM for ATG, and similar to3 muM for MAsIII. In hepatocytes exposed to 1 muM MAsIII for up to 24 h, the inhibition of TR activity was maximal (similar to 40\%) after exposure for 15 min. After exposure for 3 h [when most MAsIII has been converted to dimethyl As (DMAs)], TR activity in these cells had returned to control levels. Notably, exposure of the cell to 50 muM DMAsIII did not affect TR activity. In hepatocytes exposed to 10 muM iAs(III) for up to 24 h, the inhibition of TR activity was progressive; at 24 h, activity was reduced similar to 35\%. Following exposure to iAsIII or MAsIII, the extent of inhibition of TR activity correlated strongly with the intracellular concentration of MAs. Taken together, these results suggest that arsenicals formed in the course of cellular metabolism of As are potent inhibitors of TR activity. In particular, MAsIII, an intermediate in the metabolic pathway, is an especially potent inhibitor of TR. Hence, the capacity of cells to produce or consume the intermediates in the pathway for As methylation may be an important determinant of susceptibility to the toxic effects of As.}, keywords = {apoptosis, ENZYMATIC REDUCTION, IN-VITRO METHYLATION, LIVER, MAMMALIAN SYSTEMS, MONOMETHYLARSONOUS ACID MMA(III), NF-KAPPA-B, RABBIT ERYTHROCYTES, REDOX, REGULATION, SUBSTRATE}, isbn = {0893-228X}, url = {://000167723600007}, author = {Lin, S. and Del Razo, L. M. and Styblo, M. and Wang, C. Q. and Cullen, W. R. and Thomas, D. J.} } @article {4655, title = {Tensor LEED analysis for the Cu(111)-(root x root 7)R19.1 degrees-S surface structure}, journal = {Surface Science}, volume = {441}, number = {2-3}, year = {1999}, note = {ISI Document Delivery No.: 253RWTimes Cited: 11Cited Reference Count: 36}, month = {Nov}, pages = {425-435}, type = {Article}, abstract = {A tensor LEED analysis is reported for the (root 7 x root 7)R19.1 degrees structure formed by S at the Cu(lll)surface. A new structural model is found which corresponds to a modified version of the copper sulphide overlayer model first proposed by Domange and Oudar. In that model, the topmost layer has 3/7 monolayer each of Cu and S atoms, but the modification involves one S atom per unit mesh moving down to displace a Cu atom from the second metal layer. Relaxations among the topmost Cu atoms result in one S atom being effectively three-fold coordinate while the other two are sixfold coordinate and 12-fold coordinate: the averaged S-Cu bond lengths are indicated to equal 2.19, 2.47 and 2.62 Angstrom respectively. Some discussion is included of factors that may influence this choice of surface structure. (C) 1999 Elsevier Science B.V. All rights reserved.}, keywords = {ADSORPTION, chemisorption, copper, ENERGY-ELECTRON-DIFFRACTION, LAYERS, low energy electron diffraction, LOW INDEX SINGLE CRYSTAL, METAL-SURFACES, MOLECULE, RAY STANDING-WAVE, RECONSTRUCTION, RU(0001), SUBSTRATE, SULFUR, sulphur, SURFACE, surface reconstruction}, isbn = {0039-6028}, url = {://000083570400024}, author = {Saidy, M. and Mitchell, K. A. R.} } @article {4657, title = {Tensor LEED analysis for the Ni(111)-(root 7 x root 7)R19.1 degrees-P surface structure: Comparison with other root 7 systems}, journal = {Surface and Interface Analysis}, volume = {28}, number = {1}, year = {1999}, note = {ISI Document Delivery No.: 234JZTimes Cited: 1Cited Reference Count: 36Asia-Pacific Surface and Interface Analysis Conference 1998 (APSIAC 98)NOV 30-DEC 04, 1998SINGAPORE, SINGAPORE}, month = {Aug}, pages = {84-91}, type = {Proceedings Paper}, abstract = {A crystallographic analysis is reported using low-energy electron diffraction (LEED) in the tensor LEED approach for the (root 7 x root 7)R19.1 degrees structure formed by 3/7 monolayer of phosphorus at the Ni(111) surface. This surface has a novel structure in which each phosphorus atom bonds to seven neighbouring Ni atoms, four in the top layer and three in the second layer, at an average distance close to 2.39 Angstrom. Formally this reconstruction involves three neighbouring Ni atoms in a triangular arrangement per unit mesh of the original unreconstructed surface being replaced by three phosphorus atoms. A discussion is included of the structural relaxations that occur in this surface as the demands of Ni-P bonding are balanced against those for Ni-Ni and P-P contributions. Comparisons are made with the root 7 reconstructions observed for related systems, including those for P/Rh(111), S/Pd(111) and S/Cu(111). Copyright (C) 1999 John Wiley \& Sons, Ltd.}, keywords = {(ROOT-3X-ROOT-3)R30-DEGREES, analysis, chemisorption, CRYSTALLOGRAPHIC, ENERGY-ELECTRON-DIFFRACTION, LEED, METAL-SURFACES, Ni, NI(111), P, RAY STANDING-WAVE, RECONSTRUCTION, RELAXATIONS, SUBSTRATE, SULFUR}, isbn = {0142-2421}, url = {://000082482200018}, author = {Saidy, M. and Zhou, M. Y. and Mitchell, K. A. R.} } @article {3430, title = {A NOVEL SURFACE-STRUCTURE - RH(111)-(ROOT-7X-ROOT-7)R19.1-DEGREES-P}, journal = {Journal of the American Chemical Society}, volume = {117}, number = {49}, year = {1995}, note = {ISI Document Delivery No.: TK382Times Cited: 7Cited Reference Count: 26}, month = {Dec}, pages = {12344-12345}, type = {Note}, keywords = {acetylene, chemisorption, CYCLOTRIMERIZATION, ENERGY-ELECTRON-DIFFRACTION, HETEROCYCLIZATION SITES, INTERMEDIATE, MOLECULAR PATHWAYS, palladium, SUBSTRATE, SULFIDED PD(111) SURFACE}, isbn = {0002-7863}, url = {://A1995TK38200041}, author = {Liu, W. and Wong, K. C. and Mitchell, K. A. R.} } @article {3186, title = {TENSOR LEED ANALYSIS OF THE CU(110)-(2 X 3)-N SURFACE-STRUCTURE}, journal = {Physical Review B}, volume = {49}, number = {16}, year = {1994}, note = {ISI Document Delivery No.: NK063Times Cited: 27Cited Reference Count: 25}, month = {Apr}, pages = {11515-11518}, type = {Note}, abstract = {A tensor LEED analysis of the Cu(110)-(2 x 3)-N surface structure supports. a reconstruction model in which the topmost layer can be described as a pseudo-(100)-c(2 x 2)-N overlayer, with metal corrugation of about 0.52 angstrom in the reconstructed layer. Each N atom is nearly coplanar with the local plane formed by the four neighboring Cu atoms. Of the four N atoms per unit mesh, three also bond to Cu atoms in the layer below and are therefore five-coordinate. Two of the three five-coordinate sites result from appreciable lateral displacements toward each other of both N atoms and Cu atoms below in the topmost Cu(110) layer. Average N-Cu bond lengths for the five-coordinate sites (1.87 angstrom) agree well with prediction, while the bond lengths for the four-coordinate sites (1.85 angstrom) appear somewhat long. These different N sites are discussed in relation to a recent STM study, and results from this LEED analysis are contrasted with those from the previous LEED study, which supported a [001]-missing row reconstruction of the surface.}, keywords = {CU(110)(2X3)-N STRUCTURE, ENERGY-ELECTRON-DIFFRACTION, ION-SCATTERING, NITRIDE, NITROGEN, RECONSTRUCTION, SITE, SUBSTRATE}, isbn = {0163-1829}, url = {://A1994NK06300093}, author = {Vu, D. T. and Mitchell, K. A. R.} } @article {7321, title = {BINDING-ENERGY AND CATALYSIS - FLUORINATED AND DEOXYGENATED GLYCOSIDES AS MECHANISTIC PROBES OF ESCHERICHIA-COLI (LACZ) BETA-GALACTOSIDASE}, journal = {Biochemical Journal}, volume = {286}, year = {1992}, note = {ISI Document Delivery No.: JN815Times Cited: 86Cited Reference Count: 40Part 3}, month = {Sep}, pages = {721-727}, type = {Article}, abstract = {Kinetic parameters for the hydrolysis of a series of deoxy and deoxyfluoro analogues of 2{\textquoteright},4{\textquoteright}-dinitrophenyl beta-D-galactopyranoside by Escherichia coli (lacZ) beta-galactosidase have been determined and rates found to be two to nine orders of magnitude lower than that for the parent compound. These large rate reductions result primarily from the loss of transition-state binding interactions due to the replacement of sugar hydroxy groups, and such interactions are estimated to contribute at least 16.7 kJ (4 kcal).mol-1 to binding at the 3, 4 and 6 positions and more than 33.5 kJ (8 kcal).mol-1 at the 2 position. The existence of a linear free-energy relationship between log(k(cat.)/K(m)) for these compounds and the logarithm of the first-order rate constant for their spontaneous hydrolysis demonstrates that electronic effects are also important and provides direct evidence for oxocarbonium ion character in the enzymic transition state. A covalent intermediate which turns over only extremely slowly (t1/2 = 45 h) accumulates during hydrolysis of the 2-deoxyfluorogalactoside, and kinetic parameters for its formation have been determined. This intermediate is nonetheless catalytically competent, since it re-activates much more rapidly in the presence of the transglycosylation acceptors methanol or glucose, thereby providing support for the notion of a covalent intermediate during hydrolysis of the parent substrates.}, keywords = {ALPHA-D-GLUCOPYRANOSYL, D-GLUCOPYRANOSYL PHOSPHATES, ENZYME, GLYCOGEN-PHOSPHORYLASE, HYDROLYSIS, inhibitors, OLIGOSACCHARIDE, SITE, SPECIFICITY, SUBSTRATE}, isbn = {0264-6021}, url = {://A1992JN81500010}, author = {McCarter, J. D. and Adam,Michael J. and Withers, S. G.} }