Mitochondrial evolution   总被引：1，自引：0，他引：1  

Gray MW  Burger G  Lang BF 《Science (New York, N.Y.)》1999,283(5407):1476-1481

The serial endosymbiosis theory is a favored model for explaining the origin of mitochondria, a defining event in the evolution of eukaryotic cells. As usually described, this theory posits that mitochondria are the direct descendants of a bacterial endosymbiont that became established at an early stage in a nucleus-containing (but amitochondriate) host cell. Gene sequence data strongly support a monophyletic origin of the mitochondrion from a eubacterial ancestor shared with a subgroup of the alpha-Proteobacteria. However, recent studies of unicellular eukaryotes (protists), some of them little known, have provided insights that challenge the traditional serial endosymbiosis-based view of how the eukaryotic cell and its mitochondrion came to be. These data indicate that the mitochondrion arose in a common ancestor of all extant eukaryotes and raise the possibility that this organelle originated at essentially the same time as the nuclear component of the eukaryotic cell rather than in a separate, subsequent event.  相似文献   

Deeply inverted electron-hole recombination in a luminescent antibody-stilbene complex     

Debler EW  Kaufmann GF  Meijler MM  Heine A  Mee JM  Pljevaljcic G  Di Bilio AJ  Schultz PG  Millar DP  Janda KD  Wilson IA  Gray HB  Lerner RA 《Science (New York, N.Y.)》2008,319(5867):1232-1235

The blue-emissive antibody EP2-19G2 that has been elicited against trans-stilbene has unprecedented ability to produce bright luminescence and has been used as a biosensor in various applications. We show that the prolonged luminescence is not stilbene fluorescence. Instead, the emissive species is a charge-transfer excited complex of an anionic stilbene and a cationic, parallel pi-stacked tryptophan. Upon charge recombination, this complex generates exceptionally bright blue light. Complex formation is enabled by a deeply penetrating ligand-binding pocket, which in turn results from a noncanonical interface between the two variable domains of the antibody.  相似文献   

Silurian trilete spores and spore tetrads from gotland: their implications for land plant evolution     

Gray J  Laufeld S  Boucot AJ 《Science (New York, N.Y.)》1974,185(4147):260-263

Land-plant type spores occur in argillaceous limestones and platform graptolitic mudstones of Wenlock-Ludlow age in Sweden. Analysis of the stratal sequence demonstrates that occurrence of abundant spores is a function of depositional ecology, particularly water depth and shoreline proximity. This ecological analysis and the seeming absence of any correlation between the first appearances of abundant spores and megafossils of land-plant type raise the possibility that land plants evolved far earlier than the megafossil record suggests.  相似文献   

Antiproliferative activity of a hybrid protein between interferon-gamma and tumor necrosis factor-beta   总被引：2，自引：0，他引：2  

G S Feng  P W Gray  H M Shepard  M W Taylor 《Science (New York, N.Y.)》1988,241(4872):1501-1503

A hybrid protein between interferon-gamma and tumor necrosis factor-beta was made by ligating the respective genes and expressing the fused genes under the control of the trp promoter in Escherichia coli. The antiproliferative activity of the hybrid protein in vitro was greatly increased compared with either interferon-gamma or tumor necrosis factor-beta alone, and both antiviral activity and cytotoxic effect were retained in the hybrid protein. The hybrid protein may have potential clinical application.  相似文献   

Gaussian free-energy dependence of electron-transfer rates in iridium complexes     

Fox LS  Kozik M  Winkler JR  Gray HB 《Science (New York, N.Y.)》1990,247(4946):1069-1071

The kinetics of photoinduced electron-transfer (ET) reactions have been measured in a series of synthetic donor-acceptor complexes. The electron donors are singlet or triplet excited iridium(I) dimers (Ir(2)), and the acceptors are N-alkylpyridinium groups covalently bound to phosphinite ligands on the Ir(2) core. Rate constants for excited-state ET range from 3.5 x 10(6) to 1.1 x 10(11) per second, and thermal back ET (pyridinium radical to Ir(2)(+)) rates vary from 2.0 x 10(10) to 6.7 x 10(7) per second. The variation of these rates with driving force is in remarkably good agreement with the Marcus theory prediction of a Gaussian free-energy dependence.  相似文献   

Modelling the oceanic habitats of two pelagic species using recreational fisheries data          下载免费PDF全文

Stephanie Brodie  Alistair J. Hobday  James A. Smith  Jason D. Everett  Matt D. Taylor  Charles A. Gray  Iain M. Suthers 《Fisheries Oceanography》2015,24(5):463-477

Defining the oceanic habitats of migratory marine species is important for both single species and ecosystem‐based fisheries management, particularly when the distribution of these habitats vary temporally. This can be achieved using species distribution models that include physical environmental predictors. In the present study, species distribution models that describe the seasonal habitats of two pelagic fish (dolphinfish, Coryphaena hippurus and yellowtail kingfish, Seriola lalandi), are developed using 19 yr of presence‐only data from a recreational angler‐based catch‐and‐release fishing programme. A Poisson point process model within a generalized additive modelling framework was used to determine the species distributions off the east coast of Australia as a function of several oceanographic covariates. This modelling framework uses presence‐only data to determine the intensity of fish (fish km^?2), rather than a probability of fish presence. Sea surface temperature (SST), sea level anomaly, SST frontal index and eddy kinetic energy were significant environmental predictors for both dolphinfish and kingfish distributions. Models for both species indicate a greater fish intensity off the east Australian coast during summer and autumn in response to the regional oceanography, namely shelf incursions by the East Australian Current. This study provides a framework for using presence‐only recreational fisheries data to create species distribution models that can contribute to the future dynamic spatial management of pelagic fisheries.  相似文献   

Epizootics in Industrial Livestock Production: Preventable Gaps in Biosecurity and Biocontainment          下载免费PDF全文

J. H. Leibler  K. Dalton  A. Pekosz  G. C. Gray  E. K. Silbergeld 《Zoonoses and public health》2017,64(2):137-145

While technological advances in animal husbandry have facilitated increases in global meat production, the high density and geographic concentration of food animal production facilities pose risks of infectious disease transmission. The scale of the 2014–2015 highly pathogenic avian influenza H5N2 outbreak in the United States demonstrates the challenges in achieving pathogen control within and around industrial animal facilities using existing technologies. We discuss gaps in current practice in two specific systems within these facilities – ventilation and waste management – which are under‐recognized as important drivers of microbial porosity. The development of innovative ventilation systems to reduce influx and efflux of pathogens is critically needed, and cross‐sectoral partnerships should be incentivized to do so. Adapting current human biosolid treatment technologies for farm applications, reducing animal stocking density and shifting waste management responsibility from farmer to corporation would reduce risk from current manure management systems. While innovative approaches to functionally altering the industrial food animal production system remain important priorities to promote sustainability, our intention here is to identify gaps within the current system that allow for pathogen emergence and transmission and address specific areas in which technological, administrative or policy changes are necessary to mitigate these risks.  相似文献