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91.
The 16S-23S intergenic spacer region (spacer region 1) of Streptococcus salivarius, S. thermophilus, and Lactococcus lactis subsp. cremoris and the 23S-5S intergenic spacer region (spacer region 2) of S. salivarius and L. lactis subsp. cremoriswere sequenced and compared with the spacer regions 1 and 2 of other streptococci. A high degree of intraspecific conservation was observed for S. thermophilus and L. lactis, and very similar sequences were found for S. salivarius and S. thermophilus. Whereas spacer region 1 is highly conserved in the genus Streptococcus sensu-stricto,only the tRNA gene and the rRNA processing stems are highly conserved in the three genera: Streptococcussensu-stricto, Lactococcus, and Enterococcus. The presence of a unique tRNAAla gene without the 3 terminal CCA sequence seems to be a general feature of the streptococci spacer region 1. A secondary structure model was built to show the interaction between the spacer regions 1 and 2 of S. thermophilus and S. salivarius. The rapid evolution of spacer region 1 in streptococci is in part due to insertions and deletions of small RNA stem/loop structures. 相似文献
92.
Summary Understanding the physicochemical and structural properties of peptides are important prerequisites for the rational design of bioactive peptides and peptidomimetics. The present contribution reviews methods used for the assessment and prediction of lipophilicity (or hydrophobicity) and their correlation with structural elements of peptides and closely related peptidomimetics. 相似文献
93.
Vsevolod A. Tverdislov Salam El Karadaghi Doris J. Bucher Juri A. Zakomirdin Igor G. Kharitonenkov 《生物化学与生物物理学报:生物膜》1984,778(2):276-280
The dependence of the surface potential difference (ΔU), transversal elasticity module (E1) and membrane conductivity (G0) on the concentrations of the antiviral drugs, rimantadine and amantadine was studied in the planar bilayer lipid membrane system. The method used was based on independent measurements of the second and third harmonics of the membrane capacitance current. The binding constants of bilayer lipid membranes obtained from the drug adsorption isotherms were 2.1 · 105 M?1 and 1.3 · 104 M?1 for rimantadine and amantadine, respectively. The changes in G0 took place only after drug adsorption saturation had been achieved. The influence of rimantadine and amantadine on the interaction of bilayer lipid membranes with matrix protein from influenza virus was also investigated. The presence of 70 μg/ml rimantadine in the bathing solution resulted in an increase in the concentration of M-protein at which the adsorption and conductance changes were observed. The effects of amantadine were similar to those of rimantadine but required a higher critical concentration of amantadine. The results obtained suggest that the antiviral properties of rimantadine and amantadine may be related to the interaction of these drugs with the cell membrane, which can affect virus penetration into the cell as well as maturation of the viral particle at the cell membrane. 相似文献
94.
(1) Krebs II ascites cells were taken as a model of the neoplastic cells to investigate the transverse distribution of phospholipids in the plasma membrane. The experimental procedure was based on non-lytic degradation of phospholipids in the intact cell by Naja naja phospholipase A2 and Staphylococcus aureus sphingomyelinase C and on phopholipid analysis of purified plasma membranes. It was shown that the three major phospholipids, i.e., phosphatidylcholine, phosphatidylethanolamine and sphingomyelin, are randomly distributed between the two halves of the membranes, whereas phosphatidylserine remains located in the inner leaflet. (2) The membrane localization of phosphatidylcholine and phosphatidylethanolamine subclasses (diacyl, alkylacyl and alkenylacyl) was also examined, using a new procedure of ether-phospholipid determination. The method involves a selective removal of diacyl species by guinea pig pancreas phospholipase A1 and of alkenylacyl species by acidolysis. This analysis revealed a 50% increase of ether phospholipids in the plasma membrane as compared to the whole cell (36.5 and 23.1% of total phospholipid, respectively). Furthermore, a strong membrane asymmetry was demonstrated for the three phosphatidylcholine subclasses, since 1-alkyl-2-acyl-sn-glycerol-3-phosphocholine (alkylacyl-GPC) was entirely found in the inner leaflet, whereas both diacyl- and alkenylacyl-GPC displayed an external localization. The same pattern was observed for phosphatidylethanolamine subclasses, except for 1-alkenyl-2-acyl-sn-glycero-3-phosphoethanolamine, which was found randomly distributed. These results are discussed in relation to the process of cell malignant transformation and to the biosynthesis of platelet-activating factor (PAF-acether or 1-alkyl-2-acetyl-GPC). 相似文献
95.
Mohamed Kouider Randal Hauptmann Jack M. Widholm Robert M. Skirvin Safi S. Korban 《Plant cell reports》1984,3(4):142-145
Protoplasts could be successfully isolated and cultured from callus and suspension cultures of Malus xdomestica cv. Jonathan. Protoplast-derived colonies were recovered when the osmoticum (glucose) was gradually reduced in semi-solid 8p medium or by the use of feeder plates. Formation of embryo-like structures was induced from the protoplast-derived callus on media supplemented with IAA and BA. These structures formed roots but plants failed to develop. Protoplasts could be isolated from leaves, but not from stems or petioles. The leaf protoplasts failed to divide.List of abbreviations BA
benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- ABA
abscisic acid
- IAA
indole acetic acid 相似文献
96.
Summary Hemoglobin J Mexico, an chain mutant, was studied in eight unrelated Algerian families. The quantities of the abnormal hemoglobin in 116 subjects are trimodally distributed: 55% in homozygotes, 31% and 38% in heterozygotes. Both hematological data and the / chain biosynthetic ratio are normal in heterozygotes with 31% Hb J and in homozygotes. In contrast, the MCV and MCH as well as the / biosynthetic ratio are slightly reduced in heterozygotes with 38% Hb J and in their relatives carrying Hb A. The elevated expression of J chains in heterozygotes with 38% Hb J may be due to an thalassemia gene trans to the >J locus. 相似文献
97.
98.
L. R. Guy Valadon Mohamed Osman Rosemary S. Mummery Simone Jerebzoff-Quintin S. Jerebzoff 《Physiologia plantarum》1982,56(2):199-203
An action spectrum for carotenogenesis in V. agaricinum has maxima at 395, 433, 660 and 737 nm. In a previous study it had been shown that a light-minus-dark difference spectrum of a crude extract from V. agaricinum had maxima at 390 and 420 nm, and furthermore a red, far-red interaction suggesting phytochrome involvement has been proposed. All these data suggest that there may be at least two photoreceptor systems operating in the photoinduction process here; one for the near-ultraviolet (UV-A)-mediated carotenogenesis, presumably a novel pigment, and the other for the red, far-red region, most likely phytochrome. 相似文献
99.
In rats grown up in small and large nests the lipolytic activity of adipose tissue was studied in vitro in dependence on age. Independent of age and sex a significantly higher lipoprotein lipase activity as well as a lower basal or norepinephrine stimulated lipolysis and reesterification (absolute) occurred in rats from small nests compared with rats from large nests. The calculated degree of reesterification was independent of the nest size, but decreased from 80% to 30% from one month to one year of age. The marked differences in the lipolytic activities of adipose tissue emphasize the distinct influence of the post-natal nutrition on metabolic functions in the later life and lead to the conclusion that the metabolism of adipose tissue of animals from small nests is directed towards a long-term increased storage of lipids. 相似文献
100.
Summary The effect of growth at 30°, 35° and 40° on the biomass yield and on the nucleic acid and protein content of twelve isolates of yeast has been studied. Although yields of 41.6% and a true protein content of 34% were obtained, each of the strains exhibited a lower yield and protein content at 40° than at the lower temperatures. Nucleic acid levels were also reduced at 40°. 相似文献