Active Contour
Mostrando 13-22 de 22 artigos, teses e dissertações.
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13. Isolation and visualization of active presynaptic filaments of recA protein and single-stranded DNA.
In the presence of ATP, recA protein forms a presynaptic complex with single-stranded DNA that is an obligatory intermediate in homologous pairing. Presynaptic complexes of recA protein and circular single strands that are active in forming joint molecules can be isolated by gel filtration. These isolated active complexes are nucleoprotein filaments with the
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14. A new automated method for the segmentation and characterization of breast masses on ultrasound images
Segmentation is one of the first steps in most computer-aided diagnosis systems for characterization of masses as malignant or benign. In this study, the authors designed an automated method for segmentation of breast masses on ultrasound (US) images. The method automatically estimated an initial contour based on a manually identified point approximately at
American Association of Physicists in Medicine.
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15. The inactive form of recA protein: the 'compact' structure.
When recA protein is enzymatically inactive in vitro, it adopts a more compact helical polymer form than that of the active protein polymerized onto DNA in the presence of ATP. Here we describe some aspects of this structure. By cryo-electron microscopy, a pitch of 76 A is found for both the self-polymer and the inactive complex with ssDNA. A smaller pitch o
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16. Three-Dimensional Quantitative Structure-Activity Relationship and Comparative Molecular Field Analysis of Dipeptide Hydroxamic Acid Helicobacter pylori Urease Inhibitors
A homology model of Helicobacter pylori urease was developed by using the crystal structure of urease from Klebsiella aerogenes (EC 3.5.1.5) as a template. The acetohydroxamic acid moiety was docked into the active pocket of the enzyme model, followed by relaxation of the complex by use of molecular dynamics. The resulting conformation was used as a template
American Society for Microbiology.
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17. Sequences near the Active Site in Chimeric Penicillin Binding Proteins 5 and 6 Affect Uniform Morphology of Escherichia coli
Penicillin binding protein (PBP) 5, a dd-carboxypeptidase that removes the terminal d-alanine from peptide side chains of peptidoglycan, plays an important role in creating and maintaining the uniform cell shape of Escherichia coli. PBP 6, a highly similar homologue, cannot substitute for PBP 5 in this respect. Previously, we localized the shape-maintaining
American Society for Microbiology.
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18. Penicillin Binding Protein 5 Affects Cell Diameter, Contour, and Morphology of Escherichia coli
Although general physiological functions have been ascribed to the high-molecular-weight penicillin binding proteins (PBPs) of Escherichia coli, the low-molecular-weight PBPs have no well-defined biological roles. When we examined the morphology of a set of E. coli mutants lacking multiple PBPs, we observed that strains expressing active PBP 5 produced cells
American Society for Microbiology.
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19. A motion area in human visual cortex.
We have localized an area in the human brain involved in the processing of contours defined by motion differences (kinetic contours) by comparing with positron emission tomography the regional cerebral blood flow in tasks performed with kinetic and luminance-defined gratings. These tasks included passive viewing, counting the total number of grating stimuli,
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20. Recombination by resolvase to analyse DNA communications by the SfiI restriction endonuclease.
The SfiI endonuclease differs from other type II restriction enzymes by cleaving DNA concertedly at two copies of its recognition site, its optimal activity being with two sites on the same DNA molecule. The nature of this communication event between distant DNA sites was analysed on plasmids with recognition sites for SfiI interspersed with recombination si
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21. Plasmids of Shigella dysenteriae Y6R: a Defective Col Factor
The six plasmids of Shigella dysenteriae Y6R were separated by sucrose gradients into five fractions containing deoxyribonucleic acid (DNA), having contour lengths (expressed in units equal to the fraction of the length of the replicative form of φX174), respectively, of 0.29, 0.35, 0.74, 1.08, and a mixture of 5.7 and 7.2. DNA-DNA hybridization on nitrocel
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22. The effect of partial extraction of troponin C on the elementary steps of the cross-bridge cycle in rabbit psoas muscle fibers.
The elementary steps of the cross-bridge cycle in which troponin C (TnC) was partially extracted were investigated by sinusoidal analysis in rabbit psoas muscle fibers. The effects of MgATP and phosphate on the rate constants of exponential processes were studied at 200 mM ionic strength, pCa 4.20, pH 7.00, and at 20 degrees C. The results were analyzed with