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111.
Nichola J. Hill Eric J. Ma Brandt W. Meixell Mark S. Lindberg Walter M. Boyce Jonathan A. Runstadler 《Ecology letters》2016,19(8):915-925
Influenza A Viruses (IAV) in nature must overcome shifting transmission barriers caused by the mobility of their primary host, migratory wild birds, that change throughout the annual cycle. Using a phylogenetic network of viral sequences from North American wild birds (2008–2011) we demonstrate a shift from intraspecific to interspecific transmission that along with reassortment, allows IAV to achieve viral flow across successive seasons from summer to winter. Our study supports amplification of IAV during summer breeding seeded by overwintering virus persisting locally and virus introduced from a wide range of latitudes. As birds migrate from breeding sites to lower latitudes, they become involved in transmission networks with greater connectivity to other bird species, with interspecies transmission of reassortant viruses peaking during the winter. We propose that switching transmission dynamics may be a critical strategy for pathogens that infect mobile hosts inhabiting regions with strong seasonality. 相似文献
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113.
Brain proteolipids. Isolation, purification and effect on ionic permeability of membranes 总被引:8,自引:0,他引:8
G Helynck B Luu J L Nussbaum D Picken G Skalidis E Trifilieff A Van Dorsselaer P Seta R Sandeaux C Gavach F Heitz D Simon G Spach 《European journal of biochemistry》1983,133(3):689-695
Proteolipid apoproteins have been isolated from a whole bovine brain homogenate by chloroform/methanol extraction, and fractionated by chromatography on modified (lipophilic) Sephadex, followed by ion-exchange chromatography on CM-Trisacryl. The various final, highly hydrophobic, fractions are homogeneous (sodium dodecyl sulfate/polyacrylamide gel electrophoresis). Transmembrane ion transfers were studied by 22Na + flux and electrical conductance measurements. Single channel events were observed at low protein concentrations, in particular with one of the final homogeneous apoproteolipids of molecular mass 24 kDa. 相似文献
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115.
Circular dichroism (CD) is a useful technique for an assessment of DNA-binding mode, being a more accessible, low-resolution complement to NMR and X-ray diffraction methods. Ligand-DNA interactions can be studied by virtue of the interpretation of induced ligand CD signals resulting from the coupling of electric transition moments of the ligand and DNA bases within the asymmetric DNA environment. This protocol outlines methods to determine the binding mode and affinity of ligand-DNA interactions and takes approximately 7.5 h. 相似文献
116.
Nichola J. Hawkins 《Evolution; international journal of organic evolution》2019,73(3):628-629
Plants and their pathogens are in a coevolutionary arms race. Some pathogens, such as anther smuts, use their host plants’ pollinators for spore dispersal. In the plant Dianthus pavonius, gynodioecy (having female and hermaphroditic plants) has evolved to reduce flowering duration and therefore limit exposure to anther smut pathogens. Bruns et al. (2019) show that this shift in breeding system has evolved as a disease escape mechanism. 相似文献
117.
The melting of DNA in the presence of osmolytes has been studied with the intention of obtaining information about how base pair stability is affected by changes in solution conditions. In previous investigations, the melting enthalpies were assumed to be constant as osmolalities change, but no systematic evaluation of whether this condition is true has been offered. This paper presents calorimetric data on the melting of two synthetic DNA samples in the presence of a number of common osmolytes. Poly(dAdT)*poly(dTdA) and poly(dGdC)*poly(dCdG) melting have been examined by differential scanning calorimetry in solutions containing ethylene glycol, glycerol, sucrose, urea, betaine, PEG 200 and PEG 1450 at increasing osmolalities. The results show small, but significant changes in the enthalpy of melting of the two polynucleotides that are different, depending on the structure of the cosolvent. The polyols, ethylene glycol, glycerol, PEG 200 and also urea all show decreases in melting enthalpy, while betaine and sucrose display increases with increasing concentration of cosolvent. The large stabilizing PEG 1450 shows no change within the experimental errors. Using concepts relating to preferential interactions of the cosolvents with the DNA base pairs, it is possible to interpret some of the observed changes in the thermodynamic properties of melting. The results indicate that there is strong entropy-enthalpy compensation upon melting base pairs, but entropy increases dominate to cause the decreases in stability with increased cosolvent concentration. Excess hydration parameters are evaluated and their magnitudes discussed in terms of changes in cosolvent interactions with the DNA base pairs. 相似文献
118.
Expansion,harvest and cryopreservation of human mesenchymal stem cells in a serum‐free microcarrier process
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Thomas R. J. Heathman Veronica A. M. Glyn Andrew Picken Qasim A. Rafiq Karen Coopman Alvin W. Nienow Bo Kara Christopher J. Hewitt 《Biotechnology and bioengineering》2015,112(8):1696-1707
119.
Competition dialysis is a powerful new tool for the discovery of ligands that bind to nucleic acids with structural- or sequence-selectivity. The method is based on firm thermodynamic principles and is simple to implement. In the competition dialysis experiment, an array of nucleic acid structures and sequences is dialyzed against a common test ligand solution. After equilibration, the amount of ligand bound to each structure or sequence is determined by absorbance or fluorescence measurements. Since all structures and sequences are in equilibrium with the same free ligand concentration, the amount bound is directly proportional to the ligand binding affinity. Competition dialysis thus provides a direct and quantitative measure of selectivity, and unambiguously identifies which of the samples within the array are preferred by a particular ligand. We describe here the third generation implementation of the method, in which competition dialysis was adapted for use in a 96-well plate format. In this format, we have been able to greatly expand the array of nucleic acid structures studied, and now can routinely study the interactions of a ligand of interest with 46 different structures and sequences. 相似文献
120.
Shawn J. Leroux Eric Vander Wal Yolanda F. Wiersma Louis Charron Jonathan D. Ebel Nichola M. Ellis Christopher Hart Emilie Kissler Paul W. Saunders Lucie Moudrá Amy L. Tanner Semra Yalcin 《Ecology letters》2017,20(12):1495-1506
Human activities are altering the fundamental geography of biogeochemicals. Yet we lack an understanding of how the spatial patterns in organismal stoichiometry affect biogeochemical processes and the tools to predict the impacts of global changes on biogeochemical processes. In this contribution we develop stoichiometric distribution models (StDMs), which allow us to map spatial structure in resource elemental composition across a landscape and evaluate spatial responses of consumers. We parameterise StDMs for a consumer‐resource (moose‐white birch) system and demonstrate that we can develop predictive models of resource stoichiometry across a landscape and that such models could improve our predictions of consumer space use. With results from our study system application, we argue that explicit consideration of the spatial patterns in organismal elemental composition may uncover emergent individual, population, community and ecosystem properties that are not revealed at the local extents routinely used in ecological stoichiometry. We discuss perspectives for further developments and application of StDMs to advance three emerging frameworks for spatial ecosystem ecology in an era of global change; meta‐ecosystem theory, macroecological stoichiometry and remotely sensed biogeochemistry. Progress on these emerging frameworks will allow for the integration of ecological stoichiometry and individual space use and fitness. 相似文献