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991.

Background  

Many dimeric protein complexes bind cooperatively to families of bipartite nucleic acid sequence elements, which consist of pairs of conserved half-site sequences separated by intervening distances that vary among individual sites.  相似文献   
992.

Background  

DNA sequencing is used ubiquitously: from deciphering genomes[1] to determining the primary sequence of small RNAs (smRNAs) [25]. The cloning of smRNAs is currently the most conventional method to determine the actual sequence of these important regulators of gene expression. Typical smRNA cloning projects involve the sequencing of hundreds to thousands of smRNA clones that are delimited at their 5' and 3' ends by fixed sequence regions. These primers result from the biochemical protocol used to isolate and convert the smRNA into clonable PCR products. Recently we completed a smRNA cloning project involving tobacco plants, where analysis was required for ~700 smRNA sequences[6]. Finding no easily accessible research tool to enter and analyze smRNA sequences we developed Ebbie to assist us with our study.  相似文献   
993.
994.
A new zoarcid fish, Lycodes mcallisteri, is described on the basis of nine specimens (230–375 mm SL) from eastern Arctic Canada, Nunavut (Hudson Strait, 298 m; Cumberland Sound and Baffin Bay, 579 m). It resembles about 15 other Lycodes spp. in having a long tail and a "ventromediolateral" type of lateral line. It is distinguished from Arctic members of this group (Lycodes marisalbi, L. palearis, and L. sagittarius) by the high number of pectoral fin rays (22–23), short pelvic fins, low submental crests, and coloration (6–10 light patches dorsally). It resembles two Pacific species (L. macrochir and L. soldatovi) by the high number of pectoral fin rays, but differs by coloration, meristics, and shape of the pectoral fin. Received: April 13, 2000 / Revised: September 7, 2000 / Accepted: January 11, 2001  相似文献   
995.
Plants protect their roots by alerting the enemies of grubs   总被引:7,自引:0,他引:7  
Plant roots in the soil are under attack from many soil organisms. Although many ecologists are aware of the presence and importance of natural enemies in the soil that protect the plants from herbivores, the existence and nature of tritrophic interactions are poorly understood. So far, attention has focused on how plants protect their above-ground parts against herbivorous arthropods, either directly or indirectly (i.e. by getting help from the herbivore's enemies). This article is the first in showing that indirect plant defences also operate underground. We show that the roots of a coniferous plant ( Thuja occidentalis ) release chemicals upon attack by weevil larvae ( Otiorhynchus sulcatus ) and that these chemicals thereby attract parasitic nematodes ( Heterorhabditis megidis ).  相似文献   
996.
BACKGROUND: The mechanism for the disappointing late outcome following stenting of bifurcation lesions is unclear. This prospective observational study aims to evaluate culotte stent deployment and dimensions with intravascular ultrasound (IVUS). PATIENTS AND METHODS: Patients with bifurcation stenoses were treated using two stents in a culotte configuration. After optimizing the angiographic appearance of both stents, IVUS was used to evaluate both limbs of the culotte. The main outcome measures were cross-sectional area (CSA) and minimal lumen diameter (MLD) assessed by IVUS. RESULTS: Within the culotte stent, the final mean CSA in the main limb was 6.1 mm(2) (97% of reference) and in the side-limb was 5.9 mm(2) (97% of reference). However, in each case, the minimum CSA and IVUS MLD of both limbs was at the bifurcation point. For all patients, the final mean CSA at the bifurcation point of the main limb was 4.3 mm(2) (70% of main stent) and of the side-limb was 4.4 mm(2) (75% of side stent). The IVUS MLD at the bifurcation point of the main limb was 2.1 mm (78% of main stent) and of the side-limb was 2.1 mm (84% of the side stent). Importantly, this significant residual stenosis was not detectable with quantitative coronary angiography. CONCLUSIONS: IVUS evaluation of culotte stents is feasible. The minimum IVUS CSA and MLD of both limbs of the culotte stent is at the bifurcation point. Despite an optimal angiographic appearance a significant residual stenosis was noted with IVUS at each bifurcation point.  相似文献   
997.
A shift in the growth temperature of Streptococcus faecalis from 37 to 10°C resulted in an 18% increase in the proportion of unsaturated fatty acids. Electron spin resonance spectra of spin-labeled membranes and extracted phospholipids indicated viscosity changes consistent with the alterations in fatty acid composition. Growth temperature had no significant effect on the active transport of leucine and alanine; uptake rates assayed at 10 or 35°C were essentially the same in cells grown at either 10 or 37°C. The relative rapidity of amino acid transport, which presumably contributes to the ability of S. faecalis to thrive in cold environments, is evidently unrelated to adaptive changes in the viscosity of membrane lipids.Abbreviations doxyl 4-4-dimethyloxazolidine-N-oxyl - proxyl 2,2-disubstituted 5,5-dimethylpyrrolidine-N-oxyl  相似文献   
998.
To elucidate the role of tyrosine residues in the shift of max and the light-driven proton pump of bacteriorhodopsin~ the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and i t was stable in the dark for several hours at –65°C.Four batho-intermediates were formed by irradiation with green light (500 nm) at –170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at –170°C. Four corresponding meta-intermediates were also formed by irradiation at –60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin.  相似文献   
999.
1000.
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