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71.
A real-space structure refinement method, originally developed for macromolecular X-ray crystallography, has been applied to protein structure analysis by electron microscopy (EM). This method simultaneously optimizes the fit of an atomic model to a density map and the stereo-chemical properties of the model by minimizing an energy function. The performance of this method is characterized at different resolution and signal-to-noise ratio conditions typical for EM electron density maps. A multi-resolution scheme is devised to improve the convergence of the refinement on the global energy minimum. Applications of the method to various model systems are demonstrated here. The first case is the arrangement of FlgE molecules in the helical filament of flagellar hook, in which refinement with segmented rigid bodies improves the density correlation and reduces severe van der Waals contacts among the symmetry-related subunits. The second case is a conformational analysis of the NSF AAA ATPase in which a multi-conformer model is used in the refinement to investigate the arrangement of the two ATPase domains in the molecule. The third case is a docking simulation in which the crystal structure of actin and the NOE data from NMR experiments on the dematin headpiece are combined with a low-resolution EM density map to generate an atomic model of the F-actin-dematin headpiece structure. 相似文献
72.
Quantitative measurement of cell migration using time-lapse videomicroscopy and non-linear system analysis 总被引:2,自引:2,他引:0
Wick N Thurner S Paiha K Sedivy R Vietor I Huber LA 《Histochemistry and cell biology》2003,119(1):15-20
Epithelial cells of the mammary gland possess the inherent capacity to form epithelial monolayers in vitro. This requires coordination of cell migration, cell-cell contact formation, and cell proliferation. Using time-lapse phase contrast videomicroscopy we have observed mammary gland epithelial cells over different time scales. We show the generation of a complete polarized epithelial monolayer in real-time, starting from a few cells. We subsequently concentrated on the early stages of this process by tracking epithelial cells during phases of polarized migration. We performed migration analysis using fractal measures. With this technology the structure of seemingly random processes not accessible to the usual methods of linear analysis can be measured. As a control and proof of principle approach we applied infection of cells with an adenoviral vector, which is used as a gene targeting vector for many applications. Infection markedly influenced the patterns of migratory behavior. We, therefore, believe that time-lapse videomicroscopy in combination with fractal analysis can contribute to differential characterization of distinct cellular migration patterns. This will be useful in situations of long-term alterations in cell culture systems. 相似文献
73.
Functional analysis and cell-specific expression of a phosphate transporter from tomato 总被引:28,自引:0,他引:28
Pierre Daram Silvia Brunner Bengt L. Persson Nikolaus Amrhein Marcel Bucher 《Planta》1998,206(2):225-233
74.
Preprotein Translocase of the Outer Mitochondrial Membrane: Molecular Dissection and Assembly of the General Import Pore Complex 总被引:12,自引:5,他引:7 下载免费PDF全文
Peter J. T. Dekker Michael T. Ryan Jan Brix Hanne Müller Angelika Hnlinger Nikolaus Pfanner 《Molecular and cellular biology》1998,18(11):6515-6524
The preprotein translocase of the outer mitochondrial membrane (Tom) is a multisubunit machinery containing receptors and a general import pore (GIP). We have analyzed the molecular architecture of the Tom machinery. The receptor Tom22 stably associates with Tom40, the main component of the GIP, in a complex with a molecular weight of ~400,000 (~400K), while the other receptors, Tom20 and Tom70, are more loosely associated with this GIP complex and can be found in distinct subcomplexes. A yeast mutant lacking both Tom20 and Tom70 can still form the GIP complex when sufficient amounts of Tom22 are synthesized. Besides the essential proteins Tom22 and Tom40, the GIP complex contains three small subunits, Tom5, Tom6, and Tom7. In mutant mitochondria lacking Tom6, the interaction between Tom22 and Tom40 is destabilized, leading to the dissociation of Tom22 and the generation of a subcomplex of ~100K containing Tom40, Tom7, and Tom5. Tom6 is required to promote but not to maintain a stable association between Tom22 and Tom40. The following conclusions are suggested. (i) The GIP complex, containing Tom40, Tom22, and three small Tom proteins, forms the central unit of the outer membrane import machinery. (ii) Tom20 and Tom70 are not essential for the generation of the GIP complex. (iii) Tom6 functions as an assembly factor for Tom22, promoting its stable association with Tom40. 相似文献
75.
Jadwiga Jaruzelska Karen Friis Henriksen Flemming Güttler Olaf Riess Krzysztof Borski Nikolaus Blin Ryszard Slomski 《Human genetics》1991,86(3):247-250
Summary The incidence of phenylketonuria (PKU) in the western part of Poland is 1 in 5000 live births. Restriction fragment length polymorphism (RFLP) haplotypes at the phenylalanine hydroxylase locus have been analysed in 46 Polish families with PKU. Among 43 fully-informative families 16 RFLP haplotypes were identified. Haplotype 2 is the most frequently (62%) associated with Polish PKU alleles, and the codon 408 mutation is in complete linkage disequilibrium with this haplotype in Poland. This finding is in agreement with observations in other eastern European countries (German Democratic Republic, Czechoslovakia, and Hungary) and in contrast to the genotype distribution observed in western European countries. The present observation suggests the spread of classical PKU, due to the codon 408 mutation associated with haplotype 2, from east to west in European populations. Perhaps more important for genetic counselling, 62% of all PKU chromosomes in the Polish population can now be detected using only one mutantspecific oligonucleotide probe. 相似文献
76.
Florian Karolyi Nikolaus U. Szucsich Jonathan F. Colville Harald W. Krenn 《Biological journal of the Linnean Society. Linnean Society of London》2012,107(2):414-424
The insects with the longest proboscis in relation to body length are the nectar‐feeding Nemestrinidae. These flies represent important pollinators of the South African flora and feature adaptations to particularly long‐tubed flowers. The present study examined the morphology of the extremely long and slender mouthparts of Nemestrinidae for the first time. The heavily sclerotized tubular proboscis of flies from the genus Prosoeca is highly variable in length. It measures 20–47 mm in length and may exceed double the body length in some individuals. Proximally, the proboscis consists of the labrum–epipharynx unit, the laciniae, the hypopharynx, and the labium. The distal half is composed of the prementum of the labium, which solely forms the food tube. In adaptation to long‐tubed and narrow flowers, the prementum is extremely elongated, bearing the short apical labella that appear only to be able to spread apart slightly during nectar uptake. Moving the proboscis from resting position under the body to a vertical feeding position is accomplished in particular by the movements of the laciniae, which function as a lever arm. Comparisons with the mouthparts of other flower visiting flies provide insights into adaptations to nectar‐feeding from long‐tubed flowers. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??. 相似文献
77.
78.
Daniel Martinez-Ramirez Juan Giugni Vinata Vedam-Mai Aparna Wagle Shukla Irene A. Malaty Nikolaus R. McFarland Ramon L. Rodriguez Kelly D. Foote Michael S. Okun 《PloS one》2014,9(4)
Objective
Formulate a definition and describe the clinical characteristics of PD patients with a “brittle response” (BR) to medications versus a “non-brittle response” (NBR), and characterize the use of DBS for this population.Methods
An UF IRB approved protocol used a retrospective chart review of 400 consecutive PD patients presenting to the UF Center for Movement Disorders and Neurorestoration. Patient records were anonymized and de-identified prior to analysis. SPSS statistics were used to analyze data.Results
Of 345 included patients, 19 (5.5%) met criteria for BR PD. The BR group was comprised of 58% females, compared to 29% in the NBR group (P = .008). The former had a mean age of 63.4 compared to 68.1 in the latter. BR patients had lower mean weight (63.5 vs. 79.6, P = <.001), longer mean disease duration (12.6 vs. 8.9 years, P = .003), and had been on LD for more years compared to NBR patients (9.8 vs. 5.9, P = .001). UPDRS motor scores were higher (40.4 vs. 30.0, P = .001) in BR patients. No differences were observed regarding the Schwab and England scale, PDQ-39, and BDI-II. Sixty-three percent of the BR group had undergone DBS surgery compared to 18% (P = .001). Dyskinesias were more common, severe, and more often painful (P = <.001) in the BR group. There was an overall positive benefit from DBS.Conclusion
BR PD occurred more commonly in female patients with a low body weight. Patients with longer disease duration and longer duration of LD therapy were also at risk. The BR group responded well to DBS. 相似文献79.
80.
Stephanie Nikolaus Christina Bode Erik Taal Harald E. Vonkeman Cees A. W. Glas Mart A. F. J. van de Laar 《PloS one》2015,10(12)