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51.
Mazor S Regev T Mileykovskaya E Margolin W Dowhan W Fishov I 《Biochimica et biophysica acta》2008,1778(11):2505-2511
MinD, a well-conserved bacterial amphitropic protein involved in spatial regulation of cell division, has a typical feature of reversible binding to the membrane. MinD shows a clear preference for acidic phospholipids organized into lipid domains in bacterial membrane. We have shown that binding of MinD may change the dynamics of model and native membranes (see accompanying paper [1]). On the other hand, MinD dimerization and anchoring could be enhanced on pre-existing anionic phospholipid domains. We have tested MinD binding to model membranes in which acidic and zwitterionic phospholipids are either well-mixed or segregated to phase domains. The phase separation was achieved in binary mixtures of 1-Stearoyl-2-Oleoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol] (SOPG) with 1,2-Distearoyl-sn-Glycero-3-Phosphocholine (DSPC) or 1,2-Distearoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (DSPG) and binding to these membranes was compared with that to a fluid mixture of SOPG with 1-Stearoyl-2-Oleoyl-sn-Glycero-3-Phosphocholine (SOPC). The results demonstrate that MinD binding to the membrane is enhanced by segregation of anionic phospholipids to fluid domains in a gel-phase environment and, moreover, the protein stabilizes such domains. This suggests that an uneven binding of MinD to the heterogeneous native membrane is possible, leading to formation of a lipid-specific distribution pattern of MinD and/or modulation of its temporal behavior. 相似文献
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Previous experimental studies of competition among foragers rarely distinguished between exploitation and interference competition.
In many systems this separation is experimentally impossible without interfering with the natural behavior of the animals.
Consequently, these studies can only demonstrate the combined effect of interference and exploitation on the forager’s feeding
rate, namely, it usually decreases in a decelerating rate as a function of density. We suggest here a simple experimental
and statistical procedure that facilitates the separation of the effects of interference from those of exploitation. This
procedure includes manipulation of both predator density and the foraging experiment duration. The statistical analysis is
based on multiple linear regression. The working assumption is that exploitation can be neglected at the beginning of the
foraging experiment because, initially, predators do not experience diminishing returns in prey capture rates. Using both
the results of an individual-based simulation and a field experiment dataset of gerbils foraging for seeds in an artificial
food patch located in the field, we demonstrate that our procedure can successfully detect and separate the effect of interference
from the combined overall effect of competition (i.e., interference plus exploitation).
Inon Scharf and Ido Filin contributed equally to this paper. 相似文献
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Foraging theory postulates that interference is a foraging cost and affects patch exploitation and activity times. One such system contains two species of seed-eating gerbils inhabiting sandy habitats in the Negev Desert of Israel. Low population densities of the dominant species allowed us to examine the interaction between males and females of the subordinate species, Gerbillus andersoni allenbyi , as a function of interference and resource renewal. We used giving-up densities (GUDs; the amount of food left in a resource patch when a forager abandons the patch) in seed trays to quantify patch use by gerbils. By placing 6 trays at each foraging station and either presenting all 6 trays at the start of the night (pulse treatment) or presenting one tray at a station 6 times per night (renewal treatment), we were able to manipulate characteristics of resource renewal. We used radio telemetry to obtain an independent assessment of activity. Male and female G. a. allenbyi differed in their timing of activity, with males beginning earlier than females and remaining active later. This was most pronounced for the pulse treatment. For the renewal treatment, female activity in trays was more intense early in the night, but thereafter male activity was more intense. At the same time, telemetry showed that males and females did not differ in their total activity in or out of trays. This suggests that males begin their activity on the renewal treatment by exploiting the richest natural patches of seeds. Only later when these are depleted do they move to dominate the renewing seed trays. Finally, females exploited stabilized sand habitats more than did males, especially during the renewal treatment. Taken together, these findings suggest that male G. a. allenbyi interfere with foraging in females, causing temporal shifts in their use of space and resources. 相似文献
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Capsule: In Griffon Vultures Gyps fulvus both parents take part in all parenting tasks but males take a significantly larger part of the burden. 相似文献
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Preciado-Patt Liana Hershkovitz Rami Lider Ofer Feiertag Susanne Jung Günther Fridkin Mati 《International journal of peptide research and therapeutics》1999,6(2-3):99-108
Summary Serum amyloid A (SAA), an acute-phase protein, exists normally in the serum while complexed with high-density lipoprotein
3 (SAA-HDL3). Its levels increase markedly during inflammatory diseases. The pentapeptide Tyr-Ile-Gly-Ser-Asp (YIGSR-like) and the tripeptide
Arg-Gly-Asn (RGD-like), related to the cell adhesion domains of laminin and fibronectin, respectively, exist in SAA within
close proximity (YIGSDKYFHARGNY; amino acid residues 29–42). A structure-function study of linear and head-to-tail cyclic peptides, related to the amino
acid residues 29–42) and 70–76 (GRGAEDS) of human SAA, was performed in order to evaluate their ability to inhibit adhesion of human T-lymphocytes to surfaces coated
with extracellular matrix purified from bovine corneal cells. 相似文献