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  • Female  (18)
  • Chemistry  (7)
  • Amino Acid Sequence  (6)
  • Protein Binding  (6)
  • 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.
    Type of Medium: Electronic Resource
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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.
    Type of Medium: Electronic Resource
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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.
    Type of Medium: Electronic Resource
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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: 2012-06-09
    Description: A fundamental feature of the mammalian neocortex is its columnar organization. In the visual cortex, functional columns consisting of neurons with similar orientation preferences have been characterized extensively, but how these columns are constructed during development remains unclear. The radial unit hypothesis posits that the ontogenetic columns formed by clonally related neurons migrating along the same radial glial fibre during corticogenesis provide the basis for functional columns in adult neocortex. However, a direct correspondence between the ontogenetic and functional columns has not been demonstrated. Here we show that, despite the lack of a discernible orientation map in mouse visual cortex, sister neurons in the same radial clone exhibit similar orientation preferences. Using a retroviral vector encoding green fluorescent protein to label radial clones of excitatory neurons, and in vivo two-photon calcium imaging to measure neuronal response properties, we found that sister neurons preferred similar orientations whereas nearby non-sister neurons showed no such relationship. Interestingly, disruption of gap junction coupling by viral expression of a dominant-negative mutant of Cx26 (also known as Gjb2) or by daily administration of a gap junction blocker, carbenoxolone, during the first postnatal week greatly diminished the functional similarity between sister neurons, suggesting that the maturation of ontogenetic into functional columns requires intercellular communication through gap junctions. Together with the recent finding of preferential excitatory connections among sister neurons, our results support the radial unit hypothesis and unify the ontogenetic and functional columns in the visual cortex.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3375857/" 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/PMC3375857/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Ye -- Lu, Hui -- Cheng, Pei-lin -- Ge, Shaoyu -- Xu, Huatai -- Shi, Song-Hai -- Dan, Yang -- R01 DA024681/DA/NIDA NIH HHS/ -- R01 EY018861/EY/NEI NIH HHS/ -- R01 NS065915/NS/NINDS NIH HHS/ -- R21NS072483/NS/NINDS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 May 2;486(7401):118-21. doi: 10.1038/nature11110.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Neurobiology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22678292" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Animals, Newborn ; Carbenoxolone/pharmacology ; *Cell Communication ; Clone Cells/cytology ; Connexins/genetics/metabolism ; Female ; Gap Junctions/drug effects/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Models, Neurological ; Neurons/*physiology ; Visual Cortex/*cytology
    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: 2013-09-13
    Description: Established infections with the human and simian immunodeficiency viruses (HIV and SIV, respectively) are thought to be permanent with even the most effective immune responses and antiretroviral therapies only able to control, but not clear, these infections. Whether the residual virus that maintains these infections is vulnerable to clearance is a question of central importance to the future management of millions of HIV-infected individuals. We recently reported that approximately 50% of rhesus macaques (RM; Macaca mulatta) vaccinated with SIV protein-expressing rhesus cytomegalovirus (RhCMV/SIV) vectors manifest durable, aviraemic control of infection with the highly pathogenic strain SIVmac239 (ref. 5). Here we show that regardless of the route of challenge, RhCMV/SIV vector-elicited immune responses control SIVmac239 after demonstrable lymphatic and haematogenous viral dissemination, and that replication-competent SIV persists in several sites for weeks to months. Over time, however, protected RM lost signs of SIV infection, showing a consistent lack of measurable plasma- or tissue-associated virus using ultrasensitive assays, and a loss of T-cell reactivity to SIV determinants not in the vaccine. Extensive ultrasensitive quantitative PCR and quantitative PCR with reverse transcription analyses of tissues from RhCMV/SIV vector-protected RM necropsied 69-172 weeks after challenge did not detect SIV RNA or DNA sequences above background levels, and replication-competent SIV was not detected in these RM by extensive co-culture analysis of tissues or by adoptive transfer of 60 million haematolymphoid cells to naive RM. These data provide compelling evidence for progressive clearance of a pathogenic lentiviral infection, and suggest that some lentiviral reservoirs may be susceptible to the continuous effector memory T-cell-mediated immune surveillance elicited and maintained by cytomegalovirus vectors.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3849456/" 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/PMC3849456/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hansen, Scott G -- Piatak, Michael Jr -- Ventura, Abigail B -- Hughes, Colette M -- Gilbride, Roxanne M -- Ford, Julia C -- Oswald, Kelli -- Shoemaker, Rebecca -- Li, Yuan -- Lewis, Matthew S -- Gilliam, Awbrey N -- Xu, Guangwu -- Whizin, Nathan -- Burwitz, Benjamin J -- Planer, Shannon L -- Turner, John M -- Legasse, Alfred W -- Axthelm, Michael K -- Nelson, Jay A -- Fruh, Klaus -- Sacha, Jonah B -- Estes, Jacob D -- Keele, Brandon F -- Edlefsen, Paul T -- Lifson, Jeffrey D -- Picker, Louis J -- HHSN261200800001E/PHS HHS/ -- P01 AI094417/AI/NIAID NIH HHS/ -- P51OD011092/OD/NIH HHS/ -- R01 AI060392/AI/NIAID NIH HHS/ -- R01 DE021291/DE/NIDCR NIH HHS/ -- R37 AI054292/AI/NIAID NIH HHS/ -- U19 AI095985/AI/NIAID NIH HHS/ -- U19 AI096109/AI/NIAID NIH HHS/ -- U24 OD010850/OD/NIH HHS/ -- U42 OD010426/OD/NIH HHS/ -- England -- Nature. 2013 Oct 3;502(7469):100-4. doi: 10.1038/nature12519. Epub 2013 Sep 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Vaccine and Gene Therapy Institute and Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24025770" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cytomegalovirus/genetics/immunology ; Female ; Macaca mulatta ; Male ; Molecular Sequence Data ; SAIDS Vaccines/*immunology ; Simian Acquired Immunodeficiency Syndrome/*prevention & control/virology ; Simian Immunodeficiency Virus/*immunology ; Time Factors ; Vaccines, Attenuated/immunology ; Viral Load ; Virus Replication/physiology
    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: 2013-07-09
    Description: The newly emergent Middle East respiratory syndrome coronavirus (MERS-CoV) can cause severe pulmonary disease in humans, representing the second example of a highly pathogenic coronavirus, the first being SARS-CoV. CD26 (also known as dipeptidyl peptidase 4, DPP4) was recently identified as the cellular receptor for MERS-CoV. The engagement of the MERS-CoV spike protein with CD26 mediates viral attachment to host cells and virus-cell fusion, thereby initiating infection. Here we delineate the molecular basis of this specific interaction by presenting the first crystal structures of both the free receptor binding domain (RBD) of the MERS-CoV spike protein and its complex with CD26. Furthermore, binding between the RBD and CD26 is measured using real-time surface plasmon resonance with a dissociation constant of 16.7 nM. The viral RBD is composed of a core subdomain homologous to that of the SARS-CoV spike protein, and a unique strand-dominated external receptor binding motif that recognizes blades IV and V of the CD26 beta-propeller. The atomic details at the interface between the two binding entities reveal a surprising protein-protein contact mediated mainly by hydrophilic residues. Sequence alignment indicates, among betacoronaviruses, a possible structural conservation for the region homologous to the MERS-CoV RBD core, but a high variation in the external receptor binding motif region for virus-specific pathogenesis such as receptor recognition.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lu, Guangwen -- Hu, Yawei -- Wang, Qihui -- Qi, Jianxun -- Gao, Feng -- Li, Yan -- Zhang, Yanfang -- Zhang, Wei -- Yuan, Yuan -- Bao, Jinku -- Zhang, Buchang -- Shi, Yi -- Yan, Jinghua -- Gao, George F -- England -- Nature. 2013 Aug 8;500(7461):227-31. doi: 10.1038/nature12328. Epub 2013 Jul 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23831647" target="_blank"〉PubMed〈/a〉
    Keywords: Conserved Sequence/genetics ; Coronavirus/*chemistry/genetics/*metabolism ; Dipeptidyl Peptidase 4/*chemistry/metabolism ; Humans ; Protein Binding ; Protein Interaction Domains and Motifs/genetics ; Protein Structure, Tertiary/genetics ; Receptors, Virus/*chemistry/*metabolism ; *Virus Attachment
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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