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  • 1
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    Infrared spectroscopy of the acetyl cation and its protonated ketene isomer (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-07-12
    Description: [C 2 ,H 3 ,O] + ions are generated with a pulsed discharge in a supersonic expansion containing methyl acetate or acetone. These ions are mass selected and their infrared spectra are recorded via laser photodissociation and the method of argon tagging. Computational chemistry is employed to investigate structural isomers and their spectra. The acetyl cation (CH 3 CO + ) is the global minimum and protonated ketene (CH 2 COH + ) is the next lowest energy isomer (+176.2 kJ/mol). When methyl acetate is employed as the precursor, the infrared spectrum reveals that only the acetyl cation is formed. Partially resolved rotational structure reveals rotation about the C 3 axis. When acetone is used as the precursor, acetyl is still the most abundant cation, but there is also a minor component of protonated ketene. Computations reveal a significant barrier to interconversion between the two isomers (+221 kJ/mol), indicating that protonated ketene must be obtained via kinetic trapping. Both isomers may be present in interstellar environments, and their implications for astrochemistry are discussed.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Stochastic pulse regulation in bacterial stress response (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-10-08
    Description: Gene regulatory circuits can use dynamic, and even stochastic, strategies to respond to environmental conditions. We examined activation of the general stress response mediated by the alternative sigma factor, sigma(B), in individual Bacillus subtilis cells. We observed that energy stress activates sigma(B) in discrete stochastic pulses, with increasing levels of stress leading to higher pulse frequencies. By perturbing and rewiring the endogenous system, we found that this behavior results from three key features of the sigma(B) circuit: an ultrasensitive phosphorylation switch; stochasticity ("noise"), which activates that switch; and a mixed (positive and negative) transcriptional feedback, which can both amplify a pulse and switch it off. Together, these results show how prokaryotes encode signals using stochastic pulse frequency modulation through a compact regulatory architecture.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4100694/" 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/PMC4100694/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Locke, James C W -- Young, Jonathan W -- Fontes, Michelle -- Hernandez Jimenez, Maria Jesus -- Elowitz, Michael B -- P50 GM068763/GM/NIGMS NIH HHS/ -- R01 GM079771/GM/NIGMS NIH HHS/ -- R01GM079771/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2011 Oct 21;334(6054):366-9. doi: 10.1126/science.1208144. Epub 2011 Oct 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Division of Biology and Bioengineering, Broad Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21979936" target="_blank"〉PubMed〈/a〉
    Keywords: Bacillus subtilis/*genetics/metabolism/*physiology ; Bacterial Proteins/genetics/*metabolism ; Carrier Proteins/genetics/metabolism ; Feedback, Physiological ; Gene Expression Regulation, Bacterial ; *Gene Regulatory Networks ; Mycophenolic Acid/pharmacology ; Phosphoric Monoester Hydrolases/genetics/metabolism ; Phosphorylation ; Protein-Serine-Threonine Kinases/genetics/metabolism ; Sigma Factor/genetics/*metabolism ; Stochastic Processes ; *Stress, Physiological ; Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Predominant autoantibody production by early human B cell precursors (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-08-16
    Description: During B lymphocyte development, antibodies are assembled by random gene segment reassortment to produce a vast number of specificities. A potential disadvantage of this process is that some of the antibodies produced are self-reactive. We determined the prevalence of self-reactive antibody formation and its regulation in human B cells. A majority (55 to 75%) of all antibodies expressed by early immature B cells displayed self-reactivity, including polyreactive and anti-nuclear specificities. Most of these autoantibodies were removed from the population at two discrete checkpoints during B cell development. Inefficient checkpoint regulation would lead to substantial increases in circulating autoantibodies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wardemann, Hedda -- Yurasov, Sergey -- Schaefer, Anne -- Young, James W -- Meffre, Eric -- Nussenzweig, Michel C -- New York, N.Y. -- Science. 2003 Sep 5;301(5638):1374-7. Epub 2003 Aug 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Molecular Immunology, Rockefeller University, New York, NY 10021, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12920303" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies, Antinuclear/biosynthesis/immunology ; Antibody Diversity ; Antibody Specificity ; Autoantibodies/*biosynthesis/immunology ; B-Lymphocytes/cytology/*immunology/physiology ; Cell Differentiation ; Cell Line ; Complementarity Determining Regions/chemistry/immunology ; Cytosol/immunology ; Genes, Immunoglobulin ; Humans ; Immunoglobulin Heavy Chains/chemistry/immunology ; Recombination, Genetic ; Selection, Genetic ; Tumor Cells, Cultured
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Gene regulation at the single-cell level (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-03-26
    Description: The quantitative relation between transcription factor concentrations and the rate of protein production from downstream genes is central to the function of genetic networks. Here we show that this relation, which we call the gene regulation function (GRF), fluctuates dynamically in individual living cells, thereby limiting the accuracy with which transcriptional genetic circuits can transfer signals. Using fluorescent reporter genes and fusion proteins, we characterized the bacteriophage lambda promoter P(R) in Escherichia coli. A novel technique based on binomial errors in protein partitioning enabled calibration of in vivo biochemical parameters in molecular units. We found that protein production rates fluctuate over a time scale of about one cell cycle, while intrinsic noise decays rapidly. Thus, biochemical parameters, noise, and slowly varying cellular states together determine the effective single-cell GRF. These results can form a basis for quantitative modeling of natural gene circuits and for design of synthetic ones.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rosenfeld, Nitzan -- Young, Jonathan W -- Alon, Uri -- Swain, Peter S -- Elowitz, Michael B -- New York, N.Y. -- Science. 2005 Mar 25;307(5717):1962-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departments of Molecular Cell Biology and Physics of Complex Systems, Weizmann Institute of Science, Rehovot, 76100, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15790856" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Proteins/biosynthesis ; Bacteriophage lambda/genetics ; Cell Cycle ; DNA-Binding Proteins/*metabolism ; Escherichia coli/*genetics/growth & development/metabolism ; Escherichia coli Proteins/biosynthesis/*metabolism ; Fluorescence ; *Gene Expression Regulation, Bacterial ; Green Fluorescent Proteins/biosynthesis ; Image Processing, Computer-Assisted ; Luminescent Proteins/biosynthesis ; Mathematics ; Microscopy, Fluorescence ; *Models, Genetic ; Promoter Regions, Genetic ; Recombinant Fusion Proteins/metabolism ; Repressor Proteins/*metabolism ; Signal Transduction ; Transcription Factors/*metabolism ; Transcription, Genetic ; Viral Proteins ; Viral Regulatory and Accessory Proteins
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    ER{alpha} polymorphism and alternative phenotypes [Evolution] (2014)
    National Academy of Sciences
    Details
    Publication Date: 2014-01-29
    Description: The evolution of behavior relies on changes at the level of the genome; yet the ability to attribute a behavioral change to a specific, naturally occurring genetic change is rare in vertebrates. In the white-throated sparrow (Zonotrichia albicollis), a chromosomal polymorphism (ZAL2/2m) is known to segregate with a behavioral phenotype....
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
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    Infrared spectroscopy of the methanol cation and its methylene-oxonium isomer (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-03-17
    Description: The carbenium ion with nominal formula [C,H 4 ,O] + is produced from methanol or ethylene glycol in a pulsed-discharge supersonic expansion source. The ion is mass selected, and its infrared spectrum is measured from 2000 to 4000 cm −1 using laser photodissociation spectroscopy and the method of rare gas atom tagging. Computational chemistry predicts two isomers, the methanol and methylene-oxonium cations. Predicted vibrational spectra based on scaled harmonic and reduced dimensional treatments are compared to the experimental spectra. The methanol cation is the only isomer produced when methanol is used as a precursor. When ethylene glycol is used as the precursor, methylene-oxonium is produced in addition to the methanol cation. Theoretical results at the CCSD(T)/cc-pVTZ level show that methylene-oxonium is lower in energy than methanol cation by 6.4 kcal/mol, and is in fact the global minimum isomer on the [C,H 4 ,O] + potential surface. Methanol cation is trapped behind an isomerization barrier in our source, providing a convenient method to produce and characterize this transient species. Analysis of the spectrum of the methanol cation provides evidence for strong CH stretch vibration/torsion coupling in this molecular ion.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Considerable uncertainty remains into how increasing atmospheric CO2 and anthropogenic climate changes are affecting open‐ocean marine ecosystems from phytoplankton to top predators. Biological time series data are thus urgently needed for the world’s oceans. Here, we use the carbon stable isotope composition of tuna to provide a first insight into the existence of global trends in complex ecosystem dynamics and changes in the oceanic carbon cycle. From 2000 to 2015, considerable declines in δ13C values of 0.8 to 2.5‰ were observed across three tuna species sampled globally, with more substantial changes in the Pacific Ocean compared to the Atlantic and Indian Oceans. Tunas not only recorded the Suess effect, i.e. fossil fuel‐derived and isotopically‐light carbon being incorporated into marine ecosystems, but also profound changes at the base of marine food webs. We suggest a global shift in phytoplankton community structure, e.g. a reduction of 13C‐rich phytoplankton such as diatoms, and/or a change in phytoplankton physiology during this period, while this does not prevent other concomitant changes at higher levels in the food webs. Our study establishes tuna δ13C values as a candidate essential ocean variable to assess complex ecosystem responses to climate change at regional to global scales and over decadal timescales. Finally, this time‐series will be invaluable in calibrating and validating global earth system models to project changes in marine biota.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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  • 8
    Electronic Resource
    Electronic Resource
    A Divided Titration Flask (1934)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 6 (1934), S. 388-388 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac50091a046
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  • 9
    Electronic Resource
    Electronic Resource
    Age and growth of the lanternfish Lampanyctodes hectoris (Myctophidae) from eastern Tasmania, Australia (1988)
    Springer
    Marine biology 99 (1988), S. 569-576 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The age, growth and mortality of the lanternfish Lampanyctodes hectoris (Gunther) were investigated by examining the otoliths, length-frequency data, and seasonal abundance of fish collected from continental slope waters of eastern Tasmania between April 1984 and June 1985. Although L. hectoris can live to 3 yr old, it has a high annual mortality (79%) and few live past their first year. Growth, described here by a variation of the Von Bertalanffy model, takes place mainly in the first six months of life and only during late spring and summer. The hypothesis of daily deposition of primary growth increments in myctophids was supported by comparing the back-calculated birth dates of daily-aged individuals of L. hectoris with the spawning season of this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392564
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  • 10
    Electronic Resource
    Electronic Resource
    4462811 Process and apparatus for removing hydrocarbons from air-hydrocarbon vapor mixtures
    Amsterdam : Elsevier
    Vacuum 35 (1985), S. 62 
    Details
    ISSN: 0042-207X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0042-207X(85)90106-X
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