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141.
142.
Emma Smith Rina Vekaria Katherine A. Brown Colin Longstaff 《Molecular and cellular biochemistry》2013,382(1-2):193-201
A wide range of equilibrium and kinetic constants exist for the interaction of prothrombin and other coagulation factors with various model membranes from a variety of techniques. We have investigated the interaction of prothrombin with pure dioleoylphosphatidylcholine (DOPC) membranes and dioleoylphosphatidlyserine (DOPS)-containing membranes (DOPC:DOPS, 3:1) using surface plasmon resonance (SPR, with four different model membrane presentations) in addition to isotheral titration calorimetry (ITC, with suspensions of phospholipid vesicles) and ELISA methods. Using ITC, we found a simple low-affinity interaction with DOPC:DOPS membranes with a K D = 5.1 μM. However, ELISA methods using phospholipid bound to microtitre plates indicated a complex interaction with both DOPC:DOPS and DOPC membranes with K D values of 20 and 58 nM, respectively. An explanation for these discrepant results was developed from SPR studies. Using SPR with low levels of immobilised DOPC:DOPS, a high-affinity interaction with a K D of 18 nM was obtained. However, as phospholipid and prothrombin concentrations were increased, two distinct interactions could be discerned: (i) a kinetically slow, high-affinity interaction with K D in the 10?8 M range and (ii) a kinetically rapid, low-affinity interaction with K D in the 10?6 M range. This low affinity, rapidly equilibrating, interaction dominated in the presence of DOPS. Detailed SPR studies supported a heterogeneous binding model in agreement with ELISA data. The binding of prothrombin with phospholipid membranes is complex and the techniques used to measure binding will report K D values reflecting the mixture of complexes detected. Existing data suggest that the weaker rapid interaction between prothrombin and membranes is the most important in vivo when considering the activation of prothrombin at the cell surface. 相似文献
143.
Wafa Smaoui-Damak Feten Guebsi Sahar Karray Tarak Rebai Katherine Costil Amel Hamza-Chaffai 《Invertebrate reproduction & development.》2013,57(4):261-271
In this study, the variations of glycogen concentrations in Ruditapes decussatus from Sfax coasts (Tunisia) were described in relation to the reproductive cycle. Separate analyses were made of gonad, adductor muscle and ‘remainder’. The timing of gametogenic development and spawning was evaluated using qualitative histology associated with image analysis including (1) the estimation of the gonadal occupation index (GOI), (2) surface area occupied by reserve tissues and (3) variation in oocyte diameter. The reproductive cycle of R. decussatus exhibited partial asynchronization between sexes, the major difference being observed in the duration of the spawning period. Contrary to previous studies, we observed continuous partial spawning (e.g. 50% of ripe oocytes still subsisted at the partial spawning stage). During the gametogenic cycle, GOI varied significantly in males and in females. Most oocytes were ripe and ready to spawn when their diameter reached or exceeded 45?µm. The expansion of gonad was inversely proportional to the development of the foot tissue. Glycogen concentration showed significant temporal variations between tissues, indicating the clear differentiation in energy storage between the clam organs. 相似文献
144.
Vessel hull-fouling is increasingly recognised as one of the major vectors for the transfer of marine non-indigenous species. For hundreds of years, copper (Cu) has been used as a primary biocide to prevent the establishment of fouling assemblages on ships' hulls. Some non-indigenous fouling taxa continue to be transferred via hull-fouling despite the presence of Cu antifouling biocides. In addition, several of these species appear to enjoy a competitive advantage over similar native taxa within metal-polluted environments. This metal tolerance may further assist their establishment and spread in new habitats. This review synthesises existing research on the links between Cu and the invasion of fouling species, and shows that, with respect to the vector of hull-fouling, tolerance to Cu has the potential to play a role in the transfer of non-indigenous fouling organisms. Also highlighted are the future directions for research into this important nexus between industry, ecology and environmental management. 相似文献
145.
Justin W. Conway Christopher K. McLaughlin Katherine J. Castor 《Journal of biomolecular structure & dynamics》2013,31(1)
DNA cages hold tremendous potential to encapsulate and selectively release therapeutic drugs, and can provide useful tools to probe the size and shape dependence of nucleic acid delivery (McLaughlin & Sleiman, H. F., 2011). These structures have been shown to site-specifically present ligands, small molecule drugs, or antisense/siRNA motifs, in order to increase their therapeutic efficiency (Li & Fan, C. 2012). One of the major barriers towards their in vivo applications is the susceptibility of their strands towards nuclease degradation. A number of chemical strategies have been used to block nuclease digestion of oligonucleotides and improve potency, such as the use of a phosphorothioate backbone, 2´-O-methyl, locked nucleic acids, and short hybrid gapmers. However, the synthesis of these oligonucleotides is often complicated and expensive, driving the need for simple modifications to enhance serum stability and address in vivo biodistribution. We show here a simple method to significantly enhance the nuclease stability of DNA strands, through introduction of commercially available, single-endmodifications (Conway & Sleiman 2013). We use these oligonucleotides to construct DNA cages in a single step and in quantitative yields. Even in single-stranded form, these cages stabilize their component strands towards nucleases, with mean lifetimes as long as 62?h in 10 % (v/v) fetal bovine serum (FBS). We examine the effect of other DNA-end modifications on nuclease susceptibility. Finally, we show the ligation of these single-stranded cages into topologically interesting catenane ‘necklaces,’ with mean lifetimes in serum of ~200?h. 相似文献
146.
Annie J. Valuska Katherine A. Leighty Gina M. Ferrie Valerie D. Nichols Cheryl L. Tybor Chelle Plassé Tamara L. Bettinger 《Zoo biology》2013,32(2):216-221
Mixed‐species exhibits offer a variety of benefits but can be challenging to maintain due to difficulty in managing interspecific interactions. This is particularly true when little has been documented on the behavior of the species being mixed. This was the case when we attempted to house three species of turaco (family: Musophagidae) together with other species in a walk‐through aviary. To learn more about the behavior of great blue turacos, violaceous turacos, and white‐bellied gray go‐away birds, we supplemented opportunistic keeper observations with systematic data collection on their behavior, location, distance from other birds, and visibility to visitors. Keepers reported high levels of aggression among turacos, usually initiated by a go‐away bird or a violaceous turaco. Most aggression occurred during feedings or when pairs were defending nest sites. Attempts to reduce aggression by temporarily removing birds to holding areas and reintroducing them days later were ineffective. Systematic data collection revealed increased social behavior, including aggression, during breeding season in the violaceous turacos, as well as greater location fidelity. These behavioral cues may be useful in predicting breeding behavior in the future. Ultimately, we were only able to house three species of turaco together for a short time, and prohibitively high levels of conflict occurred when pairs were breeding. We conclude that mixing these three turaco species is challenging and may not be the most appropriate housing situation for them, particularly during breeding season. However, changes in turaco species composition, sex composition, or exhibit design may result in more compatible mixed‐turaco species groups. Zoo Biol. 32:216–221, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
147.
Declines in species richness due to fertilization are typically rapid and associated with increases in aboveground production. However, in a long-term experiment examining the impacts of fertilization in an early successional community, we found it took 14 years for plant species richness to significantly decline in fertilized plots, despite fertilization causing a rapid increase in aboveground production. To determine what accounted for this lag in the species richness response, we examined several potential mechanisms. We found evidence suggesting the abundance of one functional group—tall species with long-distance (runner) clonality—drove changes in species richness, and we found little support for other mechanisms. Tall runner species initially increased in abundance due to fertilization, then declined dramatically and were not abundant again until later in the experiment, when species richness and the combined biomass of all other functional groups (non-tall runner) declined. Over 86 % of the species found throughout the course of our study are non-tall runner, and there is a strong negative relationship between non-tall runner and tall runner biomass. We therefore suggest that declines in species richness in the fertilized treatment are due to high tall runner abundance that decreases the abundance and richness of non-tall runner species. By identifying the functional group that drives declines in richness due to fertilization, our results help to elucidate how fertilization decreases plant richness and also suggest that declines in richness due to fertilization can be lessened by controlling the abundance of species with a tall runner growth form. 相似文献
148.
149.
Katherine S. Lindeburg Peter Almond Josh J. Roering Oliver A. Chadwick 《Plant and Soil》2013,367(1-2):57-75
Background and Aims
Soil chronosequences on marine terraces along the Pacific Coast of California and Oregon show evidence of podzolization, though soils ultimately evolve to Ultisols. It is not clear if this pathway of soil evolution can be extended to the humid, inland Oregon Coast Range.Methods
We analyzed soil properties for a fluvial terrace chronosequence sampled along the Siuslaw River (Oregon, USA) about 50 km from the Pacific coast. The seven terraces ranged in age from <3.5 ky to nearly 1,000 ky.Results
There was no evidence of early podsolization. Instead, evidence was found that andisolization starts early and occurs even in older soils when pedogenic iron accumulation and clay synthesis and illuviation dominate. Soils develop the morphology characteristic of Ultisols sometime between 20 and 70 ky, but high levels of oxalate extractable iron and aluminum satisfy criteria of an andic subgroup. Alfisols are not formed as an intermediary stage.Conclusions
The lack of Spodosols inland is due to the inland shift from udic to ustic or xeric moisture regime, which favors summer drying and ripening of short-range order minerals rather than deep leaching or translocation. Other factors are higher pH, different organic chemistry and faster calcium cycling under the Douglas fir inland when compared to the Sitka spruce of the coastal terraces. 相似文献150.
Cynthia C. M. Deaton Kristen Dodd Katherine Drennon Jack Nagle 《Science activities》2013,50(4):128-137
“Prey Play” is an interactive role-play activity that provides fifth-grade students with opportunities to examine predator–prey interactions. This four-part, role-play activity allows students to take on the role of a predator and prey as they reflect on the behaviors animals exhibit as they collect food and interact with one another, as well as limiting factors. Through this activity, students will enhance their communication and observation skills and showcase their creativity. 相似文献