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排序方式: 共有194条查询结果,搜索用时 15 毫秒
101.
102.
John E T Corrie V Ranjit N Munasinghe David R Trentham Andreas Barth 《Photochemical & photobiological sciences》2008,7(1):84-97
Photolysis of alpha-carboxy-2-nitrobenzyl (CNB) caged compounds, studied here by time-resolved IR and UV spectroscopy, involves at least two pathways. In one, a conventional 2-nitrobenzyl type rearrangement takes place to release the photoprotected species via rapid decay of an aci-nitro intermediate. The alpha-carboxylate moiety of the CNB group is retained and the final by-product from this pathway is 2-nitrosophenylglyoxylate. Direct measurements of product formation confirmed that release via this pathway is faster for CNB-caged compounds than for related caged compounds without an alpha-carboxylate substituent and a rationale for the faster release rate is proposed. In a second pathway, photodecarboxylation of the starting material occurs: this pathway leads only to a slow, minor release of the photoprotected species. The extent to which the latter pathway contributes is affected by the nature of buffer salts in the irradiated solution. It was more prominent in an amine-based buffer (MOPS) than in phosphate buffer. 相似文献
103.
Peter J.A. Van Den Broek Corrie J.P. Haasnoot Carla C.M. Van Leeuwen Johnny Van Steveninck 《生物化学与生物物理学报:生物膜》1982,689(3):429-436
Sorbose uptake in Saccharomyces cerevisiae, strain Delft 1, proceeds via mediated passive transport. In the cell sorbose is distributed in at least two compartments. Efflux studies showed that sorbose uptake in one of these compartments is not readily reversible. Uncouplers of oxidative phosphorylation inhibit both transport velocity and steady-state uptake level. It could be shown that these two effects are caused by different modes of action of the uncouplers. None of these two effects could be ascribed to changes of the electrochemical H+ gradient or of the intracellular pH. It is suggested that the inhibition of uptake velocity is caused by binding of the uncoupler to the sorbose translocator, thus lowering the transport activity. The uncoupler binding site is probably located at the intracellular fragment of the carrier. The second effect, reduction of the steady-state uptake level, is probably due to blocking of sorbose influx into the compartment that exhibits poor reversibility. 相似文献
104.
Forgacs E Cartwright S Kovács M Sakamoto T Sellers JR Corrie JE Webb MR White HD 《Biochemistry》2006,45(43):13035-13045
We have used a new fluorescent ATP analogue, 3'-(7-diethylaminocoumarin-3-carbonylamino)-3'-deoxyadenosine-5'-triphosphate (deac-aminoATP), to study the ATP hydrolysis mechanism of the single headed myosinV-S1. Our study demonstrates that deac-aminoATP is an excellent substrate for these studies. Although the deac-amino nucleotides have a low quantum yield in free solution, there is a very large increase in fluorescence emission ( approximately 20-fold) upon binding to the myosinV active site. The fluorescence emission intensity is independent of the hydrolysis state of the nucleotide bound to myosinV-S1. The very good signal-to-noise ratio that is obtained with deac-amino nucleotides makes them excellent substrates for studying expressed proteins that can only be isolated in small quantities. The combination of the fast rate of binding and the favorable signal-to-noise ratio also allows deac-nucleotides to be used in chase experiments to determine the kinetics of ADP and Pi dissociation from actomyosin-ADP-Pi. Although phosphate dissociation from actomyosinV-ADP-Pi does not itself produce a fluorescence signal, it produces a lag in the signal for deac-aminoADP dissociation. The lag provides direct evidence that the principal pathway of product dissociation from actomyosinV-ADP-Pi is an ordered mechanism in which phosphate precedes ADP. Although the mechanism of hydrolysis of deac-aminoATP by (acto)myosinV-S1 is qualitatively similar to the ATP hydrolysis mechanism, there are significant differences in some of the rate constants. Deac-aminoATP binds 3-fold faster to myosinV-S1, and the rate of deac-aminoADP dissociation from actomyosinV-S1 is 20-fold slower. Deac-aminoATP supports motility by myosinV-HMM on actin at a rate consistent with the slower rate of deac-aminoADP dissociation. 相似文献
105.
George Papageorgiou Andreas Barth John E T Corrie 《Photochemical & photobiological sciences》2005,4(2):216-220
Flash photolysis of a 7-nitroindolinyl carbamate derivative in neutral aqueous solution rapidly generated a monoalkyl carbonate salt. The rate constant for subsequent decarboxylation of this salt [mono(2-phosphoryloxyethyl) carbonate], determined by rapid scan IR difference spectroscopy, was 0.4 s(-1) at pH 7.0, 20 degrees C. This rate reflects release of the product alcohol upon photolysis of the parent compound. In general, alcohols protected as photolabile carbamate (or carbonate) derivatives will therefore be released too slowly for studies of the kinetics of millisecond time scale biological processes. 相似文献
106.
Davis DS Bosley EE Gronell LC Keeney SA Rossetti AM Mancinelli CA Petronis JJ 《Journal of strength and conditioning research / National Strength & Conditioning Association》2006,20(1):136-140
The purpose of this study was to determine if segmental skeletal length contributes to vertical jump (VJ) displacement in recreational athletes. Skeletal length measurements of the trunk, femur, tibia, and foot were obtained by palpation of bony landmarks and a standard tape measure. A pilot study (n = 10) examined the intratester and intertester reliability for each skeletal measure. The pilot investigation revealed fair to excellent intratester and intertester reliability. Seventy-eight recreational athletes (55 men and 23 women) with a mean age of 21.9 +/- 2.9 years participated in the investigation. Multiple regression analysis with gender as a categorical indicator variable revealed a significant gender difference; therefore, men and women were analyzed separately. Regression analysis for men identified foot length (p < 0.033, R(2) = 0.08) as the only significant skeletal length predictor of VJ displacement. None of the skeletal length measures was predictive of VJ displacement in women. Based on the results of this investigation, intrinsic skeletal length is not a strong predictor of VJ displacement in young adult recreational athletes. 相似文献
107.
Aaron W. Miller Corrie Befort Emily O. Kerr Maitreya J. Dunham 《Journal of visualized experiments : JoVE》2013,(72)
Chemostats are continuous culture systems in which cells are grown in a tightly controlled, chemically constant environment where culture density is constrained by limiting specific nutrients.1,2 Data from chemostats are highly reproducible for the measurement of quantitative phenotypes as they provide a constant growth rate and environment at steady state. For these reasons, chemostats have become useful tools for fine-scale characterization of physiology through analysis of gene expression3-6 and other characteristics of cultures at steady-state equilibrium.7 Long-term experiments in chemostats can highlight specific trajectories that microbial populations adopt during adaptive evolution in a controlled environment. In fact, chemostats have been used for experimental evolution since their invention.8 A common result in evolution experiments is for each biological replicate to acquire a unique repertoire of mutations.9-13 This diversity suggests that there is much left to be discovered by performing evolution experiments with far greater throughput. We present here the design and operation of a relatively simple, low cost array of miniature chemostats—or ministats—and validate their use in determination of physiology and in evolution experiments with yeast. This approach entails growth of tens of chemostats run off a single multiplexed peristaltic pump. The cultures are maintained at a 20 ml working volume, which is practical for a variety of applications. It is our hope that increasing throughput, decreasing expense, and providing detailed building and operation instructions may also motivate research and industrial application of this design as a general platform for functionally characterizing large numbers of strains, species, and growth parameters, as well as genetic or drug libraries. 相似文献
108.
109.
Deterministic filters such as competition and prey defences should have a strong influence on the community structure of animals
like animalivorous bats which have life histories characterized by low fecundity, low predation risk, long life expectancy
and stable populations. We investigated the relative influence of these two deterministic filters on the trophic structure
of animalivorous bat assemblages in South Africa. We used null models to test if patterns of dietary overlap were significantly
different from patterns expected by chance and multivariate analyses to test the correlations between diet and phenotype (body
size, wing morphology and echolocation). We found little evidence that competition structured the trophic niche of coexisting
bats. Contrary to predictions from competition, dietary overlap between bats of ensembles and functional groups (open-air,
clutter-edge, and clutter foragers) were significantly higher than expected by chance. Instead, we found support for the predictions
of the allotonic frequency hypothesis: there were significant relationships between peak echolocation frequency and the proportion
of moths in the diets of bats at local and regional scales, and peak echolocation frequency was the best predictor of diet
even after we controlled for the influence of body size and phylogeny. These results suggest that echolocation frequency and
prey hearing exert more influence on the trophic structure of sympatric animalivorous bats than competition. Nonetheless,
differential habitat use and sensory bias may also be major determinants of trophic structure because these are also correlated
with frequencies of bat calls. 相似文献
110.
Funaro CF Kronauer DJ Moreau CS Goldman-Huertas B Pierce NE Russell JA 《Applied and environmental microbiology》2011,77(1):346-350
In this article, we describe the distributions of Entomoplasmatales bacteria across the ants, identifying a novel lineage of gut bacteria that is unique to the army ants. While our findings indicate that the Entomoplasmatales are not essential for growth or development, molecular analyses suggest that this relationship is host specific and potentially ancient. The documented trends add to a growing body of literature that hints at a diversity of undiscovered associations between ants and bacterial symbionts. 相似文献