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91.
The core of the herpes simplex virion consists of an electron-dense toroidal structure 50 nm high, with an inside diameter of 18 nm and an outside diameter of 70 nm, penetrated by a less dense cylindrical mass. The toroid contains deoxyribonucleic acid (DNA), as evident from the observation that uranyl ion staining is removed by ethylenediaminetetraacetic acid under conditions which result in the extraction of uranyl ions bound to nuclear DNA. Studies on negatively stained preparations of purified capsids suggest that the toroid consists of DNA arranged as if it were spooled around the cylindrical mass. 相似文献
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Fibroblast cultures derived from skin biopsies of patients with Fanconi anemia had doubling times (mean of five lines: 30.3 +/- 0.2 hours) significantly longer than randomly selected normal controls (mean of nine lines: 22.9 +/- 0.4 hours). Control cultures grew more slowly in the enriched media RPMI 1640 and McCoy's 5A than in MEM; while a culture from a patient with Fanconi anemia grew more slowly only in McCoy's 5A. Differences in growth characteristics between Fanconi anemia and normal cell cultures may be useful in analyzing the metabolic error determined by the Fanconi anemia gene. 相似文献
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Summary Inclusions have been found within lipid droplets in cells of a number of air-dry seeds when investigated by freeze-etching. The inclusions invariably appear as depressions in the replicas. It is deduced that the inclusions are gaseous, and evidence from artificial preparations supports this. 相似文献
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Karen L. Anderson Christopher Page Mark F. Swift Dorit Hanein Niels Volkmann 《Journal of structural biology》2018,201(1):46-51
Combining fluorescence microscopy with electron cryo-tomography allows, in principle, spatial localization of tagged macromolecular assemblies and structural features within the cellular environment. To allow precise localization and scale integration between the two disparate imaging modalities, accurate alignment procedures are needed. Here, we describe a marker-free method for aligning images from light or cryo-light fluorescence microscopy and from electron cryo-microscopy that takes advantage of sample support features, namely the holes in the carbon film. We find that the accuracy of this method, as judged by prediction errors of the hole center coordinates, is better than 100?nm. 相似文献
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The aqueous solution equilibria and solute structure of vitamin B6 compounds and several model compounds have been investigated using 13C-nmr spectroscopy. The unsubstituted α-carbon of these compounds is a very good probe for data which permits assignment of the ionization steps to indicidual groups. While the ionizations of the pyridinium and phenolic groups take place simultaneously in 3-hydroxypyridine, they take place in well-separated steps in pyridoxamine (PM), pyridoxamine phosphate (PMP), and pyridoxal phosphate. It has been established that the ionization with a pKa value of 3.7 is predominantly phenolic in origin in PM and PMP. A zwitterionic structure consistent with the earlier spectroscopic investigations is proposed for the vitamin B6 compounds in neutral aqueous solution. 相似文献