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71.
The electron impact mass spectra of 19 trimethyl silylated flavonol mono-, di- and -triglycosides are reported for the first time. All spectra show wel 相似文献
72.
The intial phases of auxin-induced growth in coleoptile segments of Avena sativa L. were investigated using a high resolution growth recording technique, based on an angular position sensing transducer. The first response to the hormone is a slight, transient reduction of the growth rate lasting about 5 min. After this phase growth rate increases to a maximum. The duration of the increase and the maximum clearly depend on the concentration of the hormone. With increasing auxin concentration the duration of the growth rate increase is reduced from about 80 min in 10-9 M indoleacetic acid (IAA) to about 14 min in 10-4 M IAA. After the maximum the growth rate declines. Looking at the maximum of the growth rate, we obtained a dose-response curve with a sharp increase between 10-9 M and 10-6 M IAA and a slight decline between 10-6 M and 10-4 M IAA. This result is confirmed by growth rates measured one and two hours after the application of the hormone.Abbreviations IAA
indoleacetic acid 相似文献
73.
Fourier analysis of sequences along edges of the type I collagen molecule constructed from two α1(I) and one α2 chains shows that the molecule is two-sided if the supercoil pitch of the α chains along the molecular axis, P, is 39 residues (, where D = 234 residues or 67 nm). One side has alternating charged and hydrophobic regions with spacings of , while the other side has an excess of hydrophobic residues with a spacing of . These characteristics arise from sequence regularities in the α chains and the geometric relationship between the chains. The pattern is marginally strongest with α2 as chain 1. The sides could form the inside of a helical microfibril where contacts between molecules would fall P apart along the α chains. The sides could form the outside of the microfibril where contacts between microfibrils would be spaced apart by the α chain supercoil along the microfibril axis, P′. If the microfibril is a 54 helix of D-staggered collagen molecules with a left-handed supercoil of pitch , P′ is close to (43 residues). subsets in the α chains give rise to the spacing along the molecule. The microfibril has 41 screw symmetry satisfying X-ray diffraction evidence that microfibrils pack in a tetragonal unit cell.This model is the same as proposed previously by us (Trus & Piez, 1976: Piez & Trus, 1977) except that P = 39 rather than 30 residues. Contrary to our earlier assumption, P = 39 residues is within the range allowed by X-ray diffraction measurements. The present results favor P = 39 since it relates regularities in the α chain sequences to helical parameters in a direct way. Furthermore, model studies show that geometric arguments which support P = 30 are equally strong at P = 39 residues. 相似文献
74.
Ulf Stahl Paul A. Lemke Paul Tudzynski Ulrich Kück Karl Esser 《Molecular & general genetics : MGG》1978,162(3):341-343
Summary The existece of plasmid like DNA was demonstrated in senescent mycelia of Podospora anserina (strain s) by biophysical and electronmicroscopic methods. According to their contour length of about 1.4 and 2.7 m respectively the molecular weight for the monomer is in the range of 3·106.This work was supported by the Deutsche Forschungsgemeinschaft. The sojourn of P.A.L. for six months in Bochum was made possible by a Senior U.S. Scientist Award of the Alexander von Humboldt Stiftung (Bonn). 相似文献
75.
Attempted cyclization of 2,3,4-tri-O-methyl-5-seleno-L-arabinose dimethyl acetal in acidic solution gave the corresponding diselenide. Intramolecular attack by the selenobenzyl group at C-5 of 5-O-p-tolylsulfonyl-L-arabinose dibenzyl diseleno-acetal resulted in the formation of benzyl 1,5-diseleno-L-arabinopyranoside. Similarly, 2,3,5-tri-O-methyl-4-O-p-tolylsulfonyl-D-xylose dibenzyl diselenoacetal gave benzyl 2,3,5-tri-O-methyl-1,4-diseleno-L-arabinofuranoside, and 2,3,4-tri-O-acetyl-5-O-p-tolylsulfonyl-D-xylose (or ribose) dibenzyl diselenoacetal gave benzyl 2,3,4-tri-O-acetyl-1,5-diseleno-D-xylo- (or ribo-)pyranoside. The glycosylic benzylseleno group was removed from the pyranoside with mercuric acetate, but attempted deacetylation of the product led to decomposition and not to the expected 5-seleno-D-xylopyranose. 相似文献
76.
Ulrich Petzoldt Kurt Bürki Gamsl R. Illmensee Karl Illmensee 《Development genes and evolution》1983,192(3-4):138-144
Summary The cleavage of fertilized mouse eggs was prevented during cytochalasin B incubation and consequently these eggs became tetraploid the following day during in vitro culture. When the eggs were cultured further in normal medium, they cleaved and gave rise to tetraploid blastocysts. Protein synthesis was analysed in these embryos at different developmental stages using two-dimensional polyacrylamide gel electrophoresis. The protein synthesis pattern of one-cell tetraploid eggs was intermediate between those of normal one- and two-cell embryos. Tetraploid two-cell embryos expressed protein sets equivalent to those of untreated four-cell embryos, and tetraploid four-cell embryos synthesized proteins similar to those of four- to eight-cell controls. At subsequent pre-implantation stages the asynchrony was no longer detectable. When fertilized eggs were cultured continuously in the presence of cytochalasin B, they became tetraploid, octoploid and more and more polyploid without cleavage occurring. The protein synthesis patterns expressed by these one-cell polyploid eggs did not resemble that of normal fertilized eggs, but were similar to those of cleaving control embryos and blastocysts of equivalent age and nuclear division. These results strongly suggest that in early mouse embryos stage-specific translation is temporally correlated with chromosome replication (karyokinesis) and independent of cell division (cytokinesis) or cell interaction.Some of these results were presented at the IX Congress of the International Society of Developmental Biologists in Basle, Switzerland, August 28–September 1, 1981 相似文献
77.
Summary Cell recovery by means of continuous flotation of the Hansenula polymorpha cultivation medium without additives was investigated as a function of the cultivation conditions as well as of the flotation equipment construction and flotation operational parameters. The cell enrichment and separation is improved at high liquid residence times, high aeration rates, small bubble sizes, increasing height of the aerated column, and diameter of the foam column. Increasing cell age and cultivation with nitrogen limitation reduce the cell separation.Symbols CP
cell mass concentration in medium g·l–1
- CR
cell mass concentration in residue g·l–1
- CS
cell mass concentration in foam liquid g·l–1
-
V
equilibrium foam volume cm3
- V
gas flow rate through the aerated liquid column cm3·s–1
- VF
feed rate to the flotation column ml/min
-
1
V
S/V foaminess s
-
mean liquid residence time in the column s 相似文献
78.
Karl Ekwall Michèle Kermorgant Geneviève Dujardin Olga Groudinsky Piotr P. Slonimski 《Molecular & general genetics : MGG》1992,233(1-2):136-144
Summary We have characterized the nuclear geneNAM8 inSaccharomyces cerevisiae. It acts as a suppressor of mitochondrial splicing deficiencies when present on a multicopy plasmid. The suppressed mutations affect RNA folding and are located in both group I and group II introns. The gene is weakly transcribed in wildtype strains, its overexpression is a prerequisite for the suppressor action. Inactivation of theNAM8 gene does not affect cell viability, mitochondrial function or mitochondrial genome stability. TheNAM8 gene encodes a protein of 523 amino acids which includes two conserved (RNP) motifs common to RNA-binding proteins from widely different organisms. This homology with RNA-binding proteins, together with the intronic location of the suppressed mitochondrial mutations, suggests that the NAM8 protein could be a non-essential component of the mitochondrial splicing machinery and, when present in increased amounts, it could convert a deficient intron RNA folding pattern into a productive one. 相似文献
79.
The flow of jelly within a honeybee colony 总被引:8,自引:0,他引:8
Karl Crailsheim 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(8):681-689
Summary The flow of jelly from 100 nurse bees to the members of two normal-sized colonies was measured during one night. To follow the flow, nurses were injected with 14C-phenylalanine. They incorporated this label into the protein of their hypopharyngeal (brood food) glands and their own body protein. When they were allowed trophallactic contacts during the investigation period a loss of label and a shift away from the abdomen was observed, indicating protein synthesis in the hypopharyngeal glands from previously stored protein. Very young larvae were fed less frequently than older ones. Younger workers received larger amounts of jelly than older ones, but considerable amounts were given to foragers. Drones behaved similarly. Between one-third and one-half of the distributed jelly was given to imagines; 10% and 16% of all workers received radioactive jelly from 100 nurses in the two colonies during one night. Thus, jelly is a very important food for adult honey bees. There was a remarkable exchange of label within the class of nurses themselves that is interpreted as communication within the social system.Abbreviation dpm
decays per minute 相似文献
80.