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  • Time Factors  (30)
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  • 2005-2009  (30)
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  • 1
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    Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-09-19
    Description: Terrestrial ecosystems control carbon dioxide fluxes to and from the atmosphere through photosynthesis and respiration, a balance between net primary productivity and heterotrophic respiration, that determines whether an ecosystem is sequestering carbon or releasing it to the atmosphere. Global and site-specific data sets have demonstrated that climate and climate variability influence biogeochemical processes that determine net ecosystem carbon dioxide exchange (NEE) at multiple timescales. Experimental data necessary to quantify impacts of a single climate variable, such as temperature anomalies, on NEE and carbon sequestration of ecosystems at interannual timescales have been lacking. This derives from an inability of field studies to avoid the confounding effects of natural intra-annual and interannual variability in temperature and precipitation. Here we present results from a four-year study using replicate 12,000-kg intact tallgrass prairie monoliths located in four 184-m(3) enclosed lysimeters. We exposed 6 of 12 monoliths to an anomalously warm year in the second year of the study and continuously quantified rates of ecosystem processes, including NEE. We find that warming decreases NEE in both the extreme year and the following year by inducing drought that suppresses net primary productivity in the extreme year and by stimulating heterotrophic respiration of soil biota in the subsequent year. Our data indicate that two years are required for NEE in the previously warmed experimental ecosystems to recover to levels measured in the control ecosystems. This time lag caused net ecosystem carbon sequestration in previously warmed ecosystems to be decreased threefold over the study period, compared with control ecosystems. Our findings suggest that more frequent anomalously warm years, a possible consequence of increasing anthropogenic carbon dioxide levels, may lead to a sustained decrease in carbon dioxide uptake by terrestrial ecosystems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arnone, John A 3rd -- Verburg, Paul S J -- Johnson, Dale W -- Larsen, Jessica D -- Jasoni, Richard L -- Lucchesi, Annmarie J -- Batts, Candace M -- von Nagy, Christopher -- Coulombe, William G -- Schorran, David E -- Buck, Paul E -- Braswell, Bobby H -- Coleman, James S -- Sherry, Rebecca A -- Wallace, Linda L -- Luo, Yiqi -- Schimel, David S -- England -- Nature. 2008 Sep 18;455(7211):383-6. doi: 10.1038/nature07296.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Desert Research Institute, Reno, Nevada 89512, USA. jarnone@dri.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18800137" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon Dioxide/*metabolism ; *Climate ; Disasters ; *Ecosystem ; *Hot Temperature ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
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    Old-growth forests as global carbon sinks (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-09-12
    Description: Old-growth forests remove carbon dioxide from the atmosphere at rates that vary with climate and nitrogen deposition. The sequestered carbon dioxide is stored in live woody tissues and slowly decomposing organic matter in litter and soil. Old-growth forests therefore serve as a global carbon dioxide sink, but they are not protected by international treaties, because it is generally thought that ageing forests cease to accumulate carbon. Here we report a search of literature and databases for forest carbon-flux estimates. We find that in forests between 15 and 800 years of age, net ecosystem productivity (the net carbon balance of the forest including soils) is usually positive. Our results demonstrate that old-growth forests can continue to accumulate carbon, contrary to the long-standing view that they are carbon neutral. Over 30 per cent of the global forest area is unmanaged primary forest, and this area contains the remaining old-growth forests. Half of the primary forests (6 x 10(8) hectares) are located in the boreal and temperate regions of the Northern Hemisphere. On the basis of our analysis, these forests alone sequester about 1.3 +/- 0.5 gigatonnes of carbon per year. Thus, our findings suggest that 15 per cent of the global forest area, which is currently not considered when offsetting increasing atmospheric carbon dioxide concentrations, provides at least 10 per cent of the global net ecosystem productivity. Old-growth forests accumulate carbon for centuries and contain large quantities of it. We expect, however, that much of this carbon, even soil carbon, will move back to the atmosphere if these forests are disturbed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Luyssaert, Sebastiaan -- Schulze, E-Detlef -- Borner, Annett -- Knohl, Alexander -- Hessenmoller, Dominik -- Law, Beverly E -- Ciais, Philippe -- Grace, John -- England -- Nature. 2008 Sep 11;455(7210):213-5. doi: 10.1038/nature07276.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, University of Antwerp, 2610 Wilrijk, Belgium. sebastiaan.luyssaert@ua.ac.be〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18784722" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atmosphere/chemistry ; Biomass ; Carbon/*metabolism ; Carbon Dioxide/metabolism ; Databases, Factual ; Disasters ; *Ecosystem ; History, 15th Century ; History, 16th Century ; History, 17th Century ; History, 18th Century ; History, 19th Century ; History, 20th Century ; History, 21st Century ; History, Ancient ; History, Medieval ; Human Activities ; Time Factors ; Trees/*metabolism
    Print ISSN: 0028-0836
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
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    The amphioxus genome and the evolution of the chordate karyotype (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-06-20
    Description: Lancelets ('amphioxus') are the modern survivors of an ancient chordate lineage, with a fossil record dating back to the Cambrian period. Here we describe the structure and gene content of the highly polymorphic approximately 520-megabase genome of the Florida lancelet Branchiostoma floridae, and analyse it in the context of chordate evolution. Whole-genome comparisons illuminate the murky relationships among the three chordate groups (tunicates, lancelets and vertebrates), and allow not only reconstruction of the gene complement of the last common chordate ancestor but also partial reconstruction of its genomic organization, as well as a description of two genome-wide duplications and subsequent reorganizations in the vertebrate lineage. These genome-scale events shaped the vertebrate genome and provided additional genetic variation for exploitation during vertebrate evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Putnam, Nicholas H -- Butts, Thomas -- Ferrier, David E K -- Furlong, Rebecca F -- Hellsten, Uffe -- Kawashima, Takeshi -- Robinson-Rechavi, Marc -- Shoguchi, Eiichi -- Terry, Astrid -- Yu, Jr-Kai -- Benito-Gutierrez, E Lia -- Dubchak, Inna -- Garcia-Fernandez, Jordi -- Gibson-Brown, Jeremy J -- Grigoriev, Igor V -- Horton, Amy C -- de Jong, Pieter J -- Jurka, Jerzy -- Kapitonov, Vladimir V -- Kohara, Yuji -- Kuroki, Yoko -- Lindquist, Erika -- Lucas, Susan -- Osoegawa, Kazutoyo -- Pennacchio, Len A -- Salamov, Asaf A -- Satou, Yutaka -- Sauka-Spengler, Tatjana -- Schmutz, Jeremy -- Shin-I, Tadasu -- Toyoda, Atsushi -- Bronner-Fraser, Marianne -- Fujiyama, Asao -- Holland, Linda Z -- Holland, Peter W H -- Satoh, Nori -- Rokhsar, Daniel S -- BBS/B/12067/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBS/B/12067/2/Biotechnology and Biological Sciences Research Council/United Kingdom -- Biotechnology and Biological Sciences Research Council/United Kingdom -- Wellcome Trust/United Kingdom -- England -- Nature. 2008 Jun 19;453(7198):1064-71. doi: 10.1038/nature06967.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Energy Joint Genome Institute, Walnut Creek, California 94598, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18563158" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chordata/classification/*genetics ; Conserved Sequence ; DNA Transposable Elements/genetics ; *Evolution, Molecular ; Gene Duplication ; Genes/genetics ; Genetic Linkage ; Genome/*genetics ; Humans ; Introns/genetics ; Karyotyping ; Multigene Family ; Phylogeny ; Polymorphism, Genetic/genetics ; Proteins/genetics ; Synteny ; Time Factors ; Vertebrates/classification/genetics
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
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    Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-05-16
    Description: Atmospheric methane is an important greenhouse gas and a sensitive indicator of climate change and millennial-scale temperature variability. Its concentrations over the past 650,000 years have varied between approximately 350 and approximately 800 parts per 10(9) by volume (p.p.b.v.) during glacial and interglacial periods, respectively. In comparison, present-day methane levels of approximately 1,770 p.p.b.v. have been reported. Insights into the external forcing factors and internal feedbacks controlling atmospheric methane are essential for predicting the methane budget in a warmer world. Here we present a detailed atmospheric methane record from the EPICA Dome C ice core that extends the history of this greenhouse gas to 800,000 yr before present. The average time resolution of the new data is approximately 380 yr and permits the identification of orbital and millennial-scale features. Spectral analyses indicate that the long-term variability in atmospheric methane levels is dominated by approximately 100,000 yr glacial-interglacial cycles up to approximately 400,000 yr ago with an increasing contribution of the precessional component during the four more recent climatic cycles. We suggest that changes in the strength of tropical methane sources and sinks (wetlands, atmospheric oxidation), possibly influenced by changes in monsoon systems and the position of the intertropical convergence zone, controlled the atmospheric methane budget, with an additional source input during major terminations as the retreat of the northern ice sheet allowed higher methane emissions from extending periglacial wetlands. Millennial-scale changes in methane levels identified in our record as being associated with Antarctic isotope maxima events are indicative of ubiquitous millennial-scale temperature variability during the past eight glacial cycles.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Loulergue, Laetitia -- Schilt, Adrian -- Spahni, Renato -- Masson-Delmotte, Valerie -- Blunier, Thomas -- Lemieux, Benedicte -- Barnola, Jean-Marc -- Raynaud, Dominique -- Stocker, Thomas F -- Chappellaz, Jerome -- England -- Nature. 2008 May 15;453(7193):383-6. doi: 10.1038/nature06950.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS-Universite Joseph Fourier Grenoble, 54 Rue Moliere, 38402 St Martin d'Heres, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18480822" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Greenhouse Effect ; History, Ancient ; Ice Cover ; Methane/*analysis ; Temperature ; Time Factors ; Tropical Climate ; Wetlands
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
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    Loss of plant species after chronic low-level nitrogen deposition to prairie grasslands (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-02-08
    Description: Rates of atmospheric deposition of biologically active nitrogen (N) are two to seven times the pre-industrial rates in many developed nations because of combustion of fossil fuels and agricultural fertilization. They are expected to increase similarly over the next 50 years in industrializing nations of Asia and South America. Although the environmental impacts of high rates of nitrogen addition have been well studied, this is not so for the lower, chronic rates that characterize much of the globe. Here we present results of the first multi-decadal experiment to examine the impacts of chronic, experimental nitrogen addition as low as 10 kg N ha(-1) yr(-1) above ambient atmospheric nitrogen deposition (6 kg N ha(-1) yr(-1) at our site). This total input rate is comparable to terrestrial nitrogen deposition in many industrialized nations. We found that this chronic low-level nitrogen addition rate reduced plant species numbers by 17% relative to controls receiving ambient N deposition. Moreover, species numbers were reduced more per unit of added nitrogen at lower addition rates, suggesting that chronic but low-level nitrogen deposition may have a greater impact on diversity than previously thought. A second experiment showed that a decade after cessation of nitrogen addition, relative plant species number, although not species abundances, had recovered, demonstrating that some effects of nitrogen addition are reversible.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clark, Christopher M -- Tilman, David -- England -- Nature. 2008 Feb 7;451(7179):712-5. doi: 10.1038/nature06503.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Ecology, Evolution and Behavior, 100 Ecology, 1987 Upper Buford Circle, University of Minnesota, St. Paul, Minnesota 55108, USA. clark134@umn.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18256670" target="_blank"〉PubMed〈/a〉
    Keywords: *Biodiversity ; Biomass ; *Ecosystem ; Nitrogen/*metabolism ; Plants/classification/*metabolism ; *Poaceae/metabolism ; Random Allocation ; Time Factors
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 6
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    Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-08-30
    Description: It is thought that the Northern Hemisphere experienced only ephemeral glaciations from the Late Eocene to the Early Pliocene epochs (about 38 to 4 million years ago), and that the onset of extensive glaciations did not occur until about 3 million years ago. Several hypotheses have been proposed to explain this increase in Northern Hemisphere glaciation during the Late Pliocene. Here we use a fully coupled atmosphere-ocean general circulation model and an ice-sheet model to assess the impact of the proposed driving mechanisms for glaciation and the influence of orbital variations on the development of the Greenland ice sheet in particular. We find that Greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene. By contrast, our model results suggest that climatic shifts associated with the tectonically driven closure of the Panama seaway, with the termination of a permanent El Nino state or with tectonic uplift are not large enough to contribute significantly to the growth of the Greenland ice sheet; moreover, we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the Earth's orbit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lunt, Daniel J -- Foster, Gavin L -- Haywood, Alan M -- Stone, Emma J -- England -- Nature. 2008 Aug 28;454(7208):1102-5. doi: 10.1038/nature07223.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉BRIDGE, School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK. d.j.lunt@bristol.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18756254" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Carbon Dioxide/analysis/*metabolism ; Climate ; Greenland ; History, Ancient ; *Ice Cover ; North America ; Rain ; Time Factors
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 7
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    Polo-like kinase-1 is activated by aurora A to promote checkpoint recovery (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-07-11
    Description: Polo-like kinase-1 (PLK1) is an essential mitotic kinase regulating multiple aspects of the cell division process. Activation of PLK1 requires phosphorylation of a conserved threonine residue (Thr 210) in the T-loop of the PLK1 kinase domain, but the kinase responsible for this has not yet been affirmatively identified. Here we show that in human cells PLK1 activation occurs several hours before entry into mitosis, and requires aurora A (AURKA, also known as STK6)-dependent phosphorylation of Thr 210. We find that aurora A can directly phosphorylate PLK1 on Thr 210, and that activity of aurora A towards PLK1 is greatly enhanced by Bora (also known as C13orf34 and FLJ22624), a known cofactor for aurora A (ref. 7). We show that Bora/aurora-A-dependent phosphorylation is a prerequisite for PLK1 to promote mitotic entry after a checkpoint-dependent arrest. Importantly, expression of a PLK1-T210D phospho-mimicking mutant partially overcomes the requirement for aurora A in checkpoint recovery. Taken together, these data demonstrate that the initial activation of PLK1 is a primary function of aurora A.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Macurek, Libor -- Lindqvist, Arne -- Lim, Dan -- Lampson, Michael A -- Klompmaker, Rob -- Freire, Raimundo -- Clouin, Christophe -- Taylor, Stephen S -- Yaffe, Michael B -- Medema, Rene H -- CA112967/CA/NCI NIH HHS/ -- GM-60594/GM/NIGMS NIH HHS/ -- England -- Nature. 2008 Sep 4;455(7209):119-23. doi: 10.1038/nature07185. Epub 2008 Jul 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medical Oncology, University Medical Center Utrecht, Utrecht 3584CG, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18615013" target="_blank"〉PubMed〈/a〉
    Keywords: Aurora Kinase A ; Aurora Kinases ; Cell Cycle/*physiology ; Cell Cycle Proteins/genetics/*metabolism ; Cell Line ; DNA Damage ; Enzyme Activation ; Humans ; Mitosis ; Molecular Sequence Data ; Phosphorylation ; Phosphothreonine/metabolism ; Protein-Serine-Threonine Kinases/genetics/*metabolism ; Proto-Oncogene Proteins/genetics/*metabolism ; Time Factors
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  • 8
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    Chaos in a long-term experiment with a plankton community (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-02-15
    Description: Mathematical models predict that species interactions such as competition and predation can generate chaos. However, experimental demonstrations of chaos in ecology are scarce, and have been limited to simple laboratory systems with a short duration and artificial species combinations. Here, we present the first experimental demonstration of chaos in a long-term experiment with a complex food web. Our food web was isolated from the Baltic Sea, and consisted of bacteria, several phytoplankton species, herbivorous and predatory zooplankton species, and detritivores. The food web was cultured in a laboratory mesocosm, and sampled twice a week for more than 2,300 days. Despite constant external conditions, the species abundances showed striking fluctuations over several orders of magnitude. These fluctuations displayed a variety of different periodicities, which could be attributed to different species interactions in the food web. The population dynamics were characterized by positive Lyapunov exponents of similar magnitude for each species. Predictability was limited to a time horizon of 15-30 days, only slightly longer than the local weather forecast. Hence, our results demonstrate that species interactions in food webs can generate chaos. This implies that stability is not required for the persistence of complex food webs, and that the long-term prediction of species abundances can be fundamentally impossible.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beninca, Elisa -- Huisman, Jef -- Heerkloss, Reinhard -- Johnk, Klaus D -- Branco, Pedro -- Van Nes, Egbert H -- Scheffer, Marten -- Ellner, Stephen P -- England -- Nature. 2008 Feb 14;451(7180):822-5. doi: 10.1038/nature06512.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18273017" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bacteria/metabolism ; *Food Chain ; Models, Biological ; *Nonlinear Dynamics ; Oceans and Seas ; Plankton/*metabolism ; Population Dynamics ; Species Specificity ; Time Factors
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  • 9
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    Transient FTY720 treatment promotes immune-mediated clearance of a chronic viral infection (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-08-16
    Description: For a wide variety of microbial pathogens, the outcome of the infection is indeterminate. In some individuals the microbe is cleared, but in others it establishes a chronic infection, and the factors that tip this balance are often unknown. In a widely used model of chronic viral infection, C57BL/6 mice clear the Armstrong strain of lymphocytic choriomeningitis virus (LCMV), but the clone 13 strain persists. Here we show that the Armstrong strain induces a profound lymphopenia at days 1-3 after infection, but the clone 13 strain does not. If we transiently augment lymphopenia by treating the clone-13-infected mice with the drug FTY720 at days 0-2 after infection, the mice successfully clear the infection by day 30. Clearance does not occur when CD4 T cells are absent at the time of treatment, indicating that the drug is not exerting direct antiviral effects. Notably, FTY720 treatment of an already established persistent infection also leads to viral clearance. In both models, FTY720 treatment preserves or augments LCMV-specific CD4 and CD8 T-cell responses, a result that is counter-intuitive because FTY720 is generally regarded as a new immunosuppressive agent. Because FTY720 targets host pathways that are completely evolutionarily conserved, our results may be translatable into new immunotherapies for the treatment of chronic microbial infections in humans.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Premenko-Lanier, Mary -- Moseley, Nelson B -- Pruett, Sarah T -- Romagnoli, Pablo A -- Altman, John D -- 5F32AI062002/AI/NIAID NIH HHS/ -- AI042373/AI/NIAID NIH HHS/ -- England -- Nature. 2008 Aug 14;454(7206):894-8. doi: 10.1038/nature07199.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Emory Vaccine Center and Department of Microbiology and Immunology, Yerkes National Primate Research Center and Emory University School of Medicine, 954 Gatewood Road, Atlanta, Georgia 30329, USA. mflanie@emory.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18704087" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chronic Disease ; Fingolimod Hydrochloride ; Lymphocytic Choriomeningitis/complications/*drug therapy/*immunology/prevention & ; control ; Lymphocytic choriomeningitis virus/*immunology/physiology ; Lymphopenia/etiology ; Mice ; Mice, Inbred C57BL ; Propylene Glycols/administration & dosage/*pharmacology/*therapeutic use ; Sphingosine/administration & dosage/*analogs & ; derivatives/pharmacology/therapeutic use ; T-Lymphocytes/drug effects/immunology ; Time Factors
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  • 10
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    Template-directed synthesis of a genetic polymer in a model protocell (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-06-06
    Description: Contemporary phospholipid-based cell membranes are formidable barriers to the uptake of polar and charged molecules ranging from metal ions to complex nutrients. Modern cells therefore require sophisticated protein channels and pumps to mediate the exchange of molecules with their environment. The strong barrier function of membranes has made it difficult to understand the origin of cellular life and has been thought to preclude a heterotrophic lifestyle for primitive cells. Although nucleotides can cross dimyristoyl phosphatidylcholine membranes through defects formed at the gel-to-liquid transition temperature, phospholipid membranes lack the dynamic properties required for membrane growth. Fatty acids and their corresponding alcohols and glycerol monoesters are attractive candidates for the components of protocell membranes because they are simple amphiphiles that form bilayer membrane vesicles that retain encapsulated oligonucleotides and are capable of growth and division. Here we show that such membranes allow the passage of charged molecules such as nucleotides, so that activated nucleotides added to the outside of a model protocell spontaneously cross the membrane and take part in efficient template copying in the protocell interior. The permeability properties of prebiotically plausible membranes suggest that primitive protocells could have acquired complex nutrients from their environment in the absence of any macromolecular transport machinery; that is, they could have been obligate heterotrophs.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2743009/" 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/PMC2743009/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mansy, Sheref S -- Schrum, Jason P -- Krishnamurthy, Mathangi -- Tobe, Sylvia -- Treco, Douglas A -- Szostak, Jack W -- F32 GM074506-01/GM/NIGMS NIH HHS/ -- F32 GM07450601/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2008 Jul 3;454(7200):122-5. doi: 10.1038/nature07018. Epub 2008 Jun 4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Department of Molecular Biology and the Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18528332" target="_blank"〉PubMed〈/a〉
    Keywords: Biological Transport ; Cell Membrane/chemistry/*metabolism ; Cell Membrane Permeability/physiology ; *Cell Physiological Phenomena ; Fatty Acids/metabolism ; Heterotrophic Processes ; *Models, Biological ; Nucleotides/metabolism ; Oligonucleotides/*metabolism ; Ribose/metabolism ; Templates, Genetic ; Time Factors
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