排序方式: 共有58条查询结果,搜索用时 0 毫秒
41.
Coronary angiographic trials have demonstrated that lowering cholesterol can slow the progression of atherosclerosis, limit the formation of new lesions and enhance atherosclerotic regression together with reducing the incidence of clinical events (Waters D, 1996). Spontaneous regression of coronary atherosclerotic lesions is rare. We report the case of a patient with a severe within-stent restenotic lesion whose coronary disease spontaneously regressed 12 months after initial diagnosis, allowing for medical treatment of symptoms rather than repeated intervention. (Int J Cardiovasc Interventions 1999; 2: 121-123) 相似文献
42.
Andrew C Doxey Michael DJ Lynch Kirsten M Müller Elizabeth M Meiering Brendan J McConkey 《BMC evolutionary biology》2008,8(1):316
Background
Clostridial neurotoxins (CNTs) are the most deadly toxins known and causal agents of botulism and tetanus neuroparalytic diseases. Despite considerable progress in understanding CNT structure and function, the evolutionary origins of CNTs remain a mystery as they are unique to Clostridium and possess a sequence and structural architecture distinct from other protein families. Uncovering the origins of CNTs would be a significant contribution to our understanding of how pathogens evolve and generate novel toxin families. 相似文献43.
44.
45.
MOTIVATION: Searching a protein sequence database for homologs is a
powerful tool for discovering the structure and function of a sequence. Two
new methods for searching sequence databases have recently been described:
Probabilistic Smith-Waterman (PSW), which is based on Hidden Markov models
for a single sequence using a standard scoring matrix, and a new version of
BLAST (WU-BLAST2), which uses Sum statistics for gapped alignments.
RESULTS: This paper compares and contrasts the effectiveness of these
methods with three older methods (Smith- Waterman: SSEARCH, FASTA and
BLASTP). The analysis indicates that the new methods are useful, and often
offer improved accuracy. These tools are compared using a curated (by Bill
Pearson) version of the annotated portion of PIR 39. Three different
statistical criteria are utilized: equivalence number, minimum errors and
the receiver operating characteristic. For complete-length protein query
sequences from large families, PSW's accuracy is superior to that of the
other methods, but its accuracy is poor when used with partial-length query
sequences. False negatives are twice as common as false positives
irrespective of the search methods if a family-specific threshold score
that minimizes the total number of errors (i.e. the most favorable
threshold score possible) is used. Thus, sensitivity, not selectivity, is
the major problem. Among the analyzed methods using default parameters, the
best accuracy was obtained from SSEARCH and PSW for complete-length
proteins, and the two BLAST programs, plus SSEARCH, for partial-length
proteins.
相似文献
46.
We report here the structural determination of N-linked oligosaccharides
found on extracellular hemoglobins of the hydrothermal vent tube worm
Riftia pachyptila. Structures were elucidated by a combination of
electrospray ionization tandem mass spectrometry, matrix- assisted laser
desorption/ionization mass spectrometry, normal-phase high performance
liquid chromatography, and exoglycosidase digestion. The sugar chains were
found to consist mainly of high-mannose-type glycans with some structures
partially capped by one or two terminal glucose residues. The present study
represents the first report of the occurrence of glucose capping of
N-linked carbohydrates in a secreted glycoprotein of a metazoan.
Previously, glucose capping has only been described for a membrane-bound
surface glycoprotein from the unicellular parasite Leishmania mexicana
amazonensis.
相似文献
47.
In limulus sperm an actin filament bundle 55 mum in length extends from the acrosomal vacuole membrane through a canal in the nucleus and then coils in a regular fashion around the base of the nucleus. The bundle expands systematically from 15 filaments near the acrosomal vacuole to 85 filaments at the basal end. Thin sections of sperm fixed during stages in spermatid maturation reveal that the filament bundle begins to assemble on dense material attached to the acrosomal vacuole membrane. In micrographs fo these early stages in maturation, short bundles are seen extending posteriorly from the dense material. The significance is that these short, developing bundles have about 85 filaments, suggesting that the 85-filament end of the bundle is assembled first. By using filament bundles isolated and incubated in vitro with G actin from muscle, we can determine the end “preferred” for addition of actin monomers during polymerization. The end that would be associated with the acrosomal vacuole membrane, a membrane destined to be continuous with the plasma membrane, is preferred about 10 times over the other, thicker end. Decoration of the newly polymerized portions of the filament bundle with subfragment 1 of myosin reveals that the arrowheads point away from the acrosomal vacuole membrane, as is true of other actin filament bundles attached to membranes. From these observations we conclude that the bundle is nucleated from the dense material associated with the acrosomal vacuole and that monomers are added to the membrane-associated end. As monomers are added at the dense material, the thick first-made end of the filament bundle is pushed down through the nucleus where, upon reaching the base of the nucleus, it coils up. Tapering is brought about by the capping of the peripheral filaments in the bundle. 相似文献
48.
Motomi Ito Kuniaki Watanabe Yoko Kita Takayuki Kawahara DJ Crawford Tetsukazu Yahara 《Journal of plant research》2000,113(1):79-89
Eupatorium were examined by sequencing the internal transcribed spacers (ITS) of nuclear ribosomal DNA and restriction site analysis
of chloroplast DNA. Molecular data provided strong evidence that (1) this genus originated in North America, (2) the genus
diverged into three morphological species groups, Eutrochium, Traganthes and Uncasia in North America, and (3) one of the North American Uncasia lineages migrated into temperate Europe and eastern Asia over the Bering land bridge. The estimated divergence times support
a late Miocene to early Pliocene migration from North America to Eurasia via the Bering land bridge. A European species was
sister to all of the eastern Asian species examined. The disjunct distribution pattern of the genus Eupatorium is incongruent with the classical Arcto-Tertiary geoflora concept.
Received 13 September 1999/ Accepted in revised form 4 January 2000 相似文献
49.
The effects of 18-crown-6 on the synthesis of peptides catalyzed by alpha-chymotrypsin are reported. Lyophilization of the enzyme in the presence of 50 equivalents of 18-crown-6 results in a 425-fold enhanced activity when the reaction between the 2-chloroethylester of N-acetyl-L-phenylalanine and L-phenylalaninamide is carried out in acetonitrile. Addition of crown ether renders the dipeptide synthesis in nonaqueous solvents catalyzed by alpha-chymotrypsin possible on a preparative scale. The acceleration is observed in different solvents and for various peptide precursors. Copyright 1998 John Wiley & Sons, Inc. 相似文献