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  • Female  (18)
  • Chemistry  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 536-539 
    ISSN: 0894-3230
    Keywords: enzyme design ; enzyme mechanism ; genetic engineering ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aspartate aminotransferase (AATase) and aminocyclopropane carboxylate synthase (ACC synthase) are pyridoxal phosphate (PLP)-dependent enzymes whose common junction of mechanistic divergence is after the formation of a Cα carbanion from the amino acid substrate bound to PLP as a Schiff base (aldimine). AATase catalyzes the reversible interconversion of α-amino acids and α-keto acids, while ACC synthase effects the irreversible decomposition of S-adenosylmethionine (SAM) to 1-aminocyclopropane-1-carboxylate (ACC) and 5′-methylthioadenosine (MTA). ACC is subsequently converted to ethylene, the plant ripening and senescence hormone, by ACC oxidase, the next enzyme in the pathway. AATase and ACC synthase exhibit many similar phenomenological characteristics that result from different detailed mechanistic origins. The kcat/KM versus pH profiles for both enzymes are similar (AATase, acidic pKa = 6.9, basic pKa = 9.6; ACC synthase, acidic pKa = 7.5, basic pKa = 8.9); however the acidic pKa of AATase reflects the ionization of an enzyme proton from the internal Schiff base, and the basic one is that of the α-amino group of the substrate, while the opposite situation obtains for ACC synthase, i.e. the apparent pKa of 7.4 is due to the α-amino group of SAM, whereas that of 9 reflects the Schiff base pKa. The mechanistic imperative underlying this reversal is dictated by the reaction mechanism and the low pKa of the α-amino group of SAM. The low pKa of SAM requires that the enzyme pKa be moved upward in order to have sufficient quantities of the reacting species at neutral pH. It is shown by viscosity variation experiments with wild-type and active site mutant controls of both enzymes that the reaction of SAM with ACC synthase is 100% diffusion controlled (kcat/KM = 1.2 × 106 l mol-1 s-1) while the corresponding reaction for the combination of L-aspartate with AATase is insensitive to viscosity, and is therefore chemically not diffusion limited. Tyr225 (AATase) or Tyr233 (ACC synthase) forms a hydrogen bond with the PLP in both enzymes, but that formed with the former enzyme is stronger and accounts for the lower pKa of the Schiff base. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 14 (1995), S. 257-265 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust layers on the bottom of mine tunnels, on factory floors, or on the floors of grain elevator passages are the most frequent cause of highly destructive dust explosions. Typically, such layered dust explosions involve a high velocity, accelerating, turbulent flame which is fed by the dust layer and results in high destructive static and dynamic pressures. In some cases transition to detonation has been observed, and such explosions are the most destructive. Scientific studies of such layered dust explosions, conducted at the University of Michigan, are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1375-1379 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A dynamic mechanical thermal analyzer (DMTA) was used to monitor changes of dynamic mechanical properties during thermal degradation of two types of epoxy/silica composites, both of which are used as electrical insulation in power apparatus. It was found that the peak value of the dynamic loss factor (tan δ), glass transition temperature (Tg), and dynamic storage modulus (E′) above Tg changed considerably with increasing thermal degradation, while E′ at the glassy state only underwent a moderate change with increased thermal degradation. It is concluded that the DMTA technique is very sensitive to the structural changes in the investigated epoxy composites due to the thermal degradation. It is also confirmed by DMTA tests that further cross-linking and loss of dangling chains are occurring slowly during the stage prior to the onset of the severe degradation. © 1992 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectra of gaseous, liquid and solid 1,1,1,3,3,3-hexafluoro-2-methoxypropane, (CF3)2 CHOCH3, and the corresponding methoxy-d3 isotope, (CF3)2 CHOCD3, together with the infrared spectra of the gases and solids, have been recorded from 3500 to 30 cm-1. A comparison of the vibrational spectra obtained for the fluid phases with those obtained for the amorphous and annealed solids indicates the predominance of a single conformer at ambient temperature in the fluid phases with the same conformer present in the solid state. Based on the lack of depolarized Raman lines in the fluid phases, and a predominance of nondescript infrared band contours, it is concluded that the stable conformer is the gauche form which has the methoxy group rotated approximately 60° from eclipsing the secondary carbon—hydrogen bond. Thirty-eight of the 39 normal modes have been assigned based on group frequencies, isotopic shifts, depolarization values and infrared band contours. There appears to be coupling of the CF3 and methoxy torsional modes. Utilizing a coupled-top barrier calculation, the barrier to internal rotation of the perfluoromethyl groups is estimated to be 2858 ± 100 cm-1 (8.2 ± 0.3 kcal mol-1) based on the torsional frequencies of 107 and 64 cm-1 observed in the solid phase. Several of the fundamentals appear as doublets in the spectra of the solids, which indicates that there are at least two molecules per primitive cell. These results are compared with similar data for some corresponding molecules.
    Additional Material: 6 Ill.
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  • 5
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectrum of gaseous nitrocyclopropane, c—C3H5NO2 has been recorded from 3500 to 30 cm-1. The interesting internal NO2 torsion was observed at 85±2cm-1 from which a barrier to internal rotation in the vapor state of 1680±70 cm-1 (4.8±0.2 kcal mol-1) was calculated. It is shown that this torsional frequency is consistent with the relative intensities of the vibrational excited states in the microwave spectrum. This barrier value is compared to those for several other NO2 substituted hydrocarbons as well as for the corresponding isoelectronic BF2 substituted molecules. The high barrier value supports the structural arguments that there is significant pseudo-conjugation between the cyclopropane ring orbitals and the substituent NO2 group. A revised vibrational assignment is presented which is compared to the one previously given for the isoelectronic molecule, c-C3H5BF2, as well as for c-C3H5BCI2.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1157-1163 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A knowledge of flow behavior is important in the study of laminar flow in twin-screw extrusion processes to predict the velocity distribution and to understand the mixing process. The flow of a power law fluid in self-wiping twin-screw extruders is examined using a two-dimensional finite element analysis of a mid-channel section of intermeshing screws. Theory is compared with experiment using food biopolymer and plastic materials. Comparisons showing overprediction of throughputs, but similarities in behavior, suggest that this model could provide an upper limit for melt conveying. For most of the throughput range examined, pumping of intermeshing self-wiping screws appears to be almost independent of the power law flow index of the melt extruded, but the value of the flow index determines the degree of influence intermeshing has on the overall pressure gradient generated in the extruder.
    Additional Material: 6 Ill.
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  • 7
    Publication Date: 2018-06-29
    Description: Chiral amines are widely used as catalysts in asymmetric synthesis to activate carbonyl groups for α-functionalization. Carbonyl catalysis reverses that strategy by using a carbonyl group to activate a primary amine. Inspired by biological carbonyl catalysis, which is exemplified by reactions of pyridoxal-dependent enzymes, we developed an N-quaternized pyridoxal catalyst for the asymmetric Mannich reaction of glycinate with aryl N -diphenylphosphinyl imines. The catalyst exhibits high activity and stereoselectivity, likely enabled by enzyme-like cooperative bifunctional activation of the substrates. Our work demonstrates the catalytic utility of the pyridoxal moiety in asymmetric catalysis.
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
    Publication Date: 2011-04-15
    Description: Schizophrenia (SCZD) is a debilitating neurological disorder with a world-wide prevalence of 1%; there is a strong genetic component, with an estimated heritability of 80-85%. Although post-mortem studies have revealed reduced brain volume, cell size, spine density and abnormal neural distribution in the prefrontal cortex and hippocampus of SCZD brain tissue and neuropharmacological studies have implicated dopaminergic, glutamatergic and GABAergic activity in SCZD, the cell types affected in SCZD and the molecular mechanisms underlying the disease state remain unclear. To elucidate the cellular and molecular defects of SCZD, we directly reprogrammed fibroblasts from SCZD patients into human induced pluripotent stem cells (hiPSCs) and subsequently differentiated these disorder-specific hiPSCs into neurons (Supplementary Fig. 1). SCZD hiPSC neurons showed diminished neuronal connectivity in conjunction with decreased neurite number, PSD95-protein levels and glutamate receptor expression. Gene expression profiles of SCZD hiPSC neurons identified altered expression of many components of the cyclic AMP and WNT signalling pathways. Key cellular and molecular elements of the SCZD phenotype were ameliorated following treatment of SCZD hiPSC neurons with the antipsychotic loxapine. To date, hiPSC neuronal pathology has only been demonstrated in diseases characterized by both the loss of function of a single gene product and rapid disease progression in early childhood. We now report hiPSC neuronal phenotypes and gene expression changes associated with SCZD, a complex genetic psychiatric disorder.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3392969/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3392969/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brennand, Kristen J -- Simone, Anthony -- Jou, Jessica -- Gelboin-Burkhart, Chelsea -- Tran, Ngoc -- Sangar, Sarah -- Li, Yan -- Mu, Yangling -- Chen, Gong -- Yu, Diana -- McCarthy, Shane -- Sebat, Jonathan -- Gage, Fred H -- P01 NS028121/NS/NINDS NIH HHS/ -- P30 NS072031/NS/NINDS NIH HHS/ -- R01 MH083911/MH/NIMH NIH HHS/ -- England -- Nature. 2011 May 12;473(7346):221-5. doi: 10.1038/nature09915. Epub 2011 Apr 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Salk Institute for Biological Studies, Laboratory of Genetics, 10010 North Torrey Pines Road, La Jolla California 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21490598" target="_blank"〉PubMed〈/a〉
    Keywords: Adolescent ; Adult ; Antipsychotic Agents/pharmacology ; Cell Differentiation ; Cells, Cultured ; Cellular Reprogramming/genetics ; Child ; Female ; Fibroblasts/cytology ; Gene Expression Profiling ; *Gene Expression Regulation/drug effects ; Humans ; Intracellular Signaling Peptides and Proteins/metabolism ; Loxapine/pharmacology ; Male ; Membrane Proteins/metabolism ; Models, Biological ; Neurites ; Neurons/*cytology/drug effects/*metabolism ; Phenotype ; Pluripotent Stem Cells/*cytology/*metabolism/pathology ; Receptors, Glutamate/metabolism ; Schizophrenia/*pathology ; Young Adult
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 9
    Publication Date: 2012-08-03
    Description: Glioblastoma multiforme is the most common primary malignant brain tumour, with a median survival of about one year. This poor prognosis is due to therapeutic resistance and tumour recurrence after surgical removal. Precisely how recurrence occurs is unknown. Using a genetically engineered mouse model of glioma, here we identify a subset of endogenous tumour cells that are the source of new tumour cells after the drug temozolomide (TMZ) is administered to transiently arrest tumour growth. A nestin-DeltaTK-IRES-GFP (Nes-DeltaTK-GFP) transgene that labels quiescent subventricular zone adult neural stem cells also labels a subset of endogenous glioma tumour cells. On arrest of tumour cell proliferation with TMZ, pulse-chase experiments demonstrate a tumour re-growth cell hierarchy originating with the Nes-DeltaTK-GFP transgene subpopulation. Ablation of the GFP+ cells with chronic ganciclovir administration significantly arrested tumour growth, and combined TMZ and ganciclovir treatment impeded tumour development. Thus, a relatively quiescent subset of endogenous glioma cells, with properties similar to those proposed for cancer stem cells, is responsible for sustaining long-term tumour growth through the production of transient populations of highly proliferative cells.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427400/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427400/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chen, Jian -- Li, Yanjiao -- Yu, Tzong-Shiue -- McKay, Renee M -- Burns, Dennis K -- Kernie, Steven G -- Parada, Luis F -- R01 CA131313/CA/NCI NIH HHS/ -- R01 NS048192-01/NS/NINDS NIH HHS/ -- England -- Nature. 2012 Aug 23;488(7412):522-6. doi: 10.1038/nature11287.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Developmental Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22854781" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antineoplastic Agents, Alkylating/pharmacology/therapeutic use ; Brain Neoplasms/*drug therapy/*pathology ; Cell Proliferation/drug effects ; Cell Tracking ; Dacarbazine/*analogs & derivatives/pharmacology/therapeutic use ; Disease Models, Animal ; Disease Progression ; Female ; Ganciclovir/pharmacology ; Glioblastoma/*drug therapy/*pathology ; Green Fluorescent Proteins/genetics/metabolism ; Male ; Mice ; Mice, Transgenic ; Neoplastic Stem Cells/*drug effects/*pathology ; Neural Stem Cells/drug effects/pathology ; Transgenes/genetics
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2012-09-21
    Description: The Pacific oyster Crassostrea gigas belongs to one of the most species-rich but genomically poorly explored phyla, the Mollusca. Here we report the sequencing and assembly of the oyster genome using short reads and a fosmid-pooling strategy, along with transcriptomes of development and stress response and the proteome of the shell. The oyster genome is highly polymorphic and rich in repetitive sequences, with some transposable elements still actively shaping variation. Transcriptome studies reveal an extensive set of genes responding to environmental stress. The expansion of genes coding for heat shock protein 70 and inhibitors of apoptosis is probably central to the oyster's adaptation to sessile life in the highly stressful intertidal zone. Our analyses also show that shell formation in molluscs is more complex than currently understood and involves extensive participation of cells and their exosomes. The oyster genome sequence fills a void in our understanding of the Lophotrochozoa.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Guofan -- Fang, Xiaodong -- Guo, Ximing -- Li, Li -- Luo, Ruibang -- Xu, Fei -- Yang, Pengcheng -- Zhang, Linlin -- Wang, Xiaotong -- Qi, Haigang -- Xiong, Zhiqiang -- Que, Huayong -- Xie, Yinlong -- Holland, Peter W H -- Paps, Jordi -- Zhu, Yabing -- Wu, Fucun -- Chen, Yuanxin -- Wang, Jiafeng -- Peng, Chunfang -- Meng, Jie -- Yang, Lan -- Liu, Jun -- Wen, Bo -- Zhang, Na -- Huang, Zhiyong -- Zhu, Qihui -- Feng, Yue -- Mount, Andrew -- Hedgecock, Dennis -- Xu, Zhe -- Liu, Yunjie -- Domazet-Loso, Tomislav -- Du, Yishuai -- Sun, Xiaoqing -- Zhang, Shoudu -- Liu, Binghang -- Cheng, Peizhou -- Jiang, Xuanting -- Li, Juan -- Fan, Dingding -- Wang, Wei -- Fu, Wenjing -- Wang, Tong -- Wang, Bo -- Zhang, Jibiao -- Peng, Zhiyu -- Li, Yingxiang -- Li, Na -- Wang, Jinpeng -- Chen, Maoshan -- He, Yan -- Tan, Fengji -- Song, Xiaorui -- Zheng, Qiumei -- Huang, Ronglian -- Yang, Hailong -- Du, Xuedi -- Chen, Li -- Yang, Mei -- Gaffney, Patrick M -- Wang, Shan -- Luo, Longhai -- She, Zhicai -- Ming, Yao -- Huang, Wen -- Zhang, Shu -- Huang, Baoyu -- Zhang, Yong -- Qu, Tao -- Ni, Peixiang -- Miao, Guoying -- Wang, Junyi -- Wang, Qiang -- Steinberg, Christian E W -- Wang, Haiyan -- Li, Ning -- Qian, Lumin -- Zhang, Guojie -- Li, Yingrui -- Yang, Huanming -- Liu, Xiao -- Wang, Jian -- Yin, Ye -- Wang, Jun -- 268513/European Research Council/International -- England -- Nature. 2012 Oct 4;490(7418):49-54. doi: 10.1038/nature11413. Epub 2012 Sep 19.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22992520" target="_blank"〉PubMed〈/a〉
    Keywords: Adaptation, Physiological/*genetics ; Animal Shells/chemistry/*growth & development ; Animals ; Apoptosis Regulatory Proteins/genetics ; Crassostrea/*genetics ; DNA Transposable Elements/genetics ; Evolution, Molecular ; Female ; Gene Expression Regulation, Developmental/genetics ; Genes, Homeobox/genetics ; Genome/*genetics ; Genomics ; HSP70 Heat-Shock Proteins/genetics ; Humans ; Larva/genetics/growth & development ; Mass Spectrometry ; Molecular Sequence Annotation ; Molecular Sequence Data ; Polymorphism, Genetic/genetics ; Repetitive Sequences, Nucleic Acid/genetics ; Sequence Analysis, DNA ; Stress, Physiological/genetics/*physiology ; Transcriptome/genetics
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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