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41.
Jens Chr. Madsen Ole Winneche Sørensen Poul Sørensen Flemming M. Poulsen 《Journal of biomolecular NMR》1993,3(2):239-244
Summary NMR pulse sequences for measuring coupling constants in 13C, 15N-labeled proteins are presented. These pulse sequences represent improvements over earlier experiments with respect to resolution and number of radiofrequency pulses. The experiments are useful for measuring JNH
, JNCO, JNC
, JH
N
CO and JH
N
H
. Applications to chymotrypsin inhibitor 2 (CI-2) are shown. 相似文献
42.
43.
Phosphorylation and dephosphorylation of ribosomal proteins have been suggested to participate in the regulation of protein synthesis in eukaryotic organisms. The present research focuses on the purification and partial characterization of a protein kinase from maize ribosomes that specifically phosphorylates acidic ribosomal proteins. Ribosomes purified from maize axes were used as the enzyme source. Purification of ribosomes was performed by centrifugation through a 0.5 M sucrose, 0.8 M KCl cushion. A protein kinase activity present in this fraction was released by extraction with 1.5 M KCl and further purified by diethylaminoethyl cellulose column chromatography. A peak containing protein kinase activity was eluted around 400 m M KCl. Analysis of this fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one band of 38 kDa molecular mass, which cross-reacted in a western blot with antibodies raised against proteins from the large ribosomal subunit. This enzyme specifically phosphorylates one of the acidic ribosomal proteins (P2 ). Its activity is inhibited by Ca2+ and Zn2+ and is activated by Mg2+ , polylysine and spermine. The relevance of this protein kinase in reinitiating the protein synthesis process during germination is discussed. 相似文献
44.
Autonomous division of the endosperm was induced by in vitro culture of unpollinated ovaries or placenta-attached ovules in Helleborus niger, Lupinus luteus and Melandrium album. The induction frequencies for the three species were 50%, 10–20% and 0.1%, respectively. The endosperms contained up to 20 free nuclei; only a few ovules with 80–420 endosperm nuclei were found. Induction of autonomous division of the endosperm, which is unusual in amphimictic plants, was observed in three new species. No embryos appeared in the ovules. This suggests a developmental independence of the endosperm from the embryo in the culture of unpollinated ovaries or ovules. 相似文献
45.
Summary The permeability of fenestrated capillaries in the mouse pineal gland to proteins and peptides was demonstrated by means of ultrastructural tracers. Horseradish peroxidase (HRP) and microperoxidase (MP) were injected intravenously and allowed to circulate for approximately 30 s, 1 min, 5 min, 1 or 2h. The tissue was then fixed by vascular perfusion or by immersion with aldehydes. In all experiments a pronounced extravasation of HRP and MP occurred. Transendothelial vesicular transport seemed to have occurred across the fenestrated capillaries. The most pronounced tracer labeling of vesicles was found after 1 min of MP- or HRP-circulation. The vesicles were uncoated and more than 70 % of the HRP-and MP-containing vesicles exhibited diameters between 50 and 110 nm. Furthermore, three other transcapillary pathways taken by the tracers are suggested: 1) via intercellular junctions, 2) through fenestrae and 3) via channels formed by fusion of vesicles with the luminal and abluminal cell membranes. Based on these results, it is assumed that the capillaries in the mouse pineal gland are also permeable to peptides synthesized and secreted by the pineal gland.Part of this study was presented at the EMCELL-76 meeting, Copenhagen, 1976 相似文献
46.
Ulrik Merrild Vibeke Schiøler Flemming Christensen Ewald Wolny Carl Johan Edeling 《Human genetics》1978,45(1):85-88
Summary Elevated levels of alpha-1-fetoprotein (AFP) were found in the amniotic fluid of a 36-year-old woman in the 15th week of gestation. Because of this and the results of repeated ultrasonography, abortion was induced. An anencephalic fetus with trisomy 18 was delivered. The possible correlation among neural-tube defects, chromosomal abnormalities, and level of AFP is discussed. 相似文献
47.
P. O. Fanger J. Højbjerre J. O. B. Thomsen 《International journal of biometeorology》1977,21(1):44-50
Preferred room temperatures were determined for 16 winter swimmers who had been exposed to cold shock daily by bathing in the sea (0–6°C) during at least two winter seasons. Each subject participated in one comfort experiment (2 1/2 h) in an environmental test chamber, where the preferred ambient temperature was determined by adjusting it according to his wishes. The subjects were sedentary and clothed in a standard uniform. Skin temperatures, rectal temperature and evaporative weight loss were measured. The results were compared with similar data for two other groups: (a) a control group of 64 normal subjects and (b) 16 persons who had been working 8 h a day at 8°C during at least 6 months in the meat packing industry. The results showed no significant differences between the ambient temperatures preferred by the three groups of subjects. This indicated that man cannot be adapted to prefer lower ambient temperatures by exposing him daily to cold. 相似文献
48.
J C Brochon P Wahl M Charlier J C Maurizot C Hélène 《Biochemical and biophysical research communications》1977,79(4):1261-1271
A new crystal form of a mitogenic lectin from pea seeds () has been obtained which is suitable for high resolution structural work. The crystals are orthorhombic, space group P212121, with unit cell dimensions: = 64.2Å, = 72. 7Å, = 108. 3Å. The asymmetric unit contains one protein molecule. 相似文献
49.
A new diol glucoside, 2-β-d-glucopyranosyloxy-2-methylpropanol, the first reported naturally occurring monoglucoside of an aliphatic dihydric alcohol, was isolated from pods of Acacia sieberana var. woodii. Structure elucidation was based on 1 H and 13C NMR spectroscopy, and enzymatic analyses. The compound was hydrolysed very slowly by almond β-glucosidase, but cleaved by a β-glucuronidase enzyme complex from Helix pomatia. 相似文献
50.
Persistence and spread of a chloramphenicol resistance-mediating plasmid in antigenic types of Escherichia coli, pathogenic for piglets 总被引:1,自引:0,他引:1
All chloramphenicol-resistant Escherichia coli strains isolated from piglets in the State veterinary Serum Laboratory, Copenhagen, in 1974-1975 harbored plasmids of IncFII group with largely the same resistance markers. Two strains from 1978 carried plasmids with similar characters. Restriction enzyme analysis of DNA from these plasmids with restriction endonucleases EcoRI, BglII, and PstI shows that the Cm plasmids are extremely closely related; but the patterns obtained (particularly from PstI digests) enable the classification of the plasmids into groups. These bear a strong relation to time and place of isolation so that plasmids isolated on the same farm belong to the same group even when their host strains are of different antigenic types. It is concluded that these plasmids have evolved from a single plasmid. 相似文献