共查询到20条相似文献,搜索用时 437 毫秒
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J A Doudna 《Current biology : CB》1999,9(19):R731-R734
Structures of the ribosome and its two subunits have been determined by X-ray crystallography at resolutions sufficient to reveal interactions between RNA and protein in the subunits and orientations of substrates at the subunit interface in the intact ribosome. 相似文献
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B Czeczuga 《Folia biologica》1991,39(1-4):17-20
The presence of carotenoids in Catopus tritis infernus Szymanowski 1957 and Choleva lederiana gracilenta Szymanowski 1957 from a cave was studies, using columnar and thin-layer chromatography. Qualitative and quantitative differences in the carotenoid content of these insect species were found. 相似文献
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SEM studies on vessels in ferns. 11. Ophioglossum 总被引:4,自引:0,他引:4
EDWARD L. SCHNEIDER SHERWIN CARLQUIST FLS 《Botanical journal of the Linnean Society. Linnean Society of London》1999,129(2):105-114
With scanning electron microscopy (SEM), the nature of metaxylem vessel elements and tracheids was examined in Ophioglossum crotalophomides, 0. pendulum subsp. falcatum , and 0. vulgatum roots and rhizomes. Vessels were identified in all species. End walls of vessel elements, which bear perforations, are like lateral wall pitting of those elements in the secondary wall framework and differ only in absence of pit membranes or presence of pit membrane remnants. Some of the perforations contain pit membrane remnants that have large pores, small porosities, or are threadlike or weblike in structure. Dimorphic perforations were found in some vessel elements of rhizomes of 0. pendulum subsp. falcatum. Tracheids are very likely present in addition to vessels in all three species. The secondary wall framework of both tracheids and vessels is basically scalariform, although deviations in pattern are present. Vessel elements of Ophiglossum are entirely comparable to those of leptosporangiate ferns. 相似文献