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31.
32.
Phytochrome induces δ-aminolevulinate dehydratase (ALAD) activity in radish seedling cotyledons under continuous far red light. Analysis of the enzymatic activity in etioplasts vs total activity shows a constant ALAD level in these organelles (10 %) in etiolated seedlings. In far red irradiated seedlings, the percentage of enzyme detected into etioplasts increases up to 45 % of the total. Comparative kinetic studies of ALAD activity detected in the cytoplasm and the etioplasts indicate an increase in both compartments with a maximum value reached respectively at 96 and 120 hr from sowing. Treatment with cycloheximide shows a very fast abolition of cytoplasmic ALAD activity which is always correlated to an etioplast decrease with a time shift of ca 24 hr. Erythromycin acts only on the cytoplasmic level of ALAD, and only for far red irradiated seedlings, with an increase of activity twice the level detected in untreated ones. This unexpected effect is discussed. 相似文献
33.
The pigment composition of two clones of Isochrysis galbana Parke (CCMP 1323 and CCAP 927/1), and Isochrysis sp. (clone T-ISO) was analyzed by high-performance liquid chromatography using a polymeric octadecylsilica column. Fluorescent peaks with retention times higher than chlorophyll a were detected for all three clones. The corresponding pigments were isolated and characterized in terms of their visible absorbance and fluorescence spectra. The pigments were similar to phytol-substituted chlorophyll c, previously isolated from Emiliania huxleyi (Lohm.) Hay and Mohler and other species containing chlmophyll c3. The presence of phytol-substituted chlorophyll c in I. galbana which lacked chlorophyll c3, increases the diversity of chlorophyll patterns for the Haptophyta, which can be grouped, at present, into six different pigment types. This is the jrst observation of a haptophyte containing the apolar phytylated chlorophyll c-like pigment but lacking chlorophyll c3. 相似文献
34.
《Biocatalysis and Biotransformation》2013,31(5):212-216
AbstractThe stereoselective oxidation of (—)-isolongifolanol (1) with a longifolene skeleton by Aspergillus niger (NBRC 4414) as a biocatalyst and suppressive effect on umuC gene expression by chemical mutagens furylfuramid and AFB1 of the SOS response in Salmonella typhimurium TA1535/pSK1002 were investigated. Compound 1 was converted to a new terpenoid, (-)-(2S,8R)-8,12-dihydroxy-isolongifolanol (2). Its structure was determined by NMR, IR, specific rotation and mass spectrometry. The metabolites suppressed the SOS-inducing activity of furylfuramid and AFB1 in the umu test. Compound 1 suppressed 51% of the SOS-inducing activity against furylfuramid at < 1.0 mM. Compound 2 suppressed 15% and 24% of the SOS-inducing activity against furylfuramid and AFB1 at < 1.0 mM respectively. 相似文献
35.
《Electromagnetic biology and medicine》2013,32(2):161-168
Cultured fibroblasts isolated from murine livers by tissue trypsinization were exposed to a static magnetic field (0.490 T) and to extremely low frequency (ELF) magnetic field (50 Hz, 0.020 T). The cultures were exposed to magnetic fields on four consecutive days for exposure times of 2, 4, 8, 16, 32, and 64 min. After such exposures and obtaining of fibroblast subcellular fractions, lipid peroxidation product—malondialdehyde (MDA) was measured. Increased peroxidation of fibroblasts' membrane structures exposed to an ELF magnetic field was observed in subcellular fractions—microsomal, mitochondrial, and nuclear. No changes in peroxidation of membrane structures were found in fibroblasts exposed to a static magnetic field. 相似文献
36.
Katherine E. Eisen Amy C. Wruck Monica A. Geber 《Evolution; international journal of organic evolution》2020,74(8):1682-1698
Although the evolution and diversification of flowers is often attributed to pollinator-mediated selection, interactions between co-occurring plant species can alter patterns of selection mediated by pollinators and other agents. The extent to which both floral density and congeneric species richness affect patterns of net and pollinator-mediated selection on multiple co-occurring species in a community is unknown and is likely to depend on whether co-occurring plants experience competition or facilitation for reproduction. We conducted an observational study of selection on four species of Clarkia (Onagraceae) and tested for pollinator-mediated selection on two Clarkia species in communities differing in congeneric species richness and local floral density. When selection varied with community context, selection was generally stronger in communities with fewer species, where local conspecific floral density was higher, and where local heterospecific floral density was lower. These patterns suggest that intraspecific competition at high densities and interspecific competition at low densities may affect the evolution of floral traits. However, selection on floral traits was not pollinator mediated in Clarkia cylindrica or Clarkia xantiana, despite variation in pollinator visitation and the extent of pollen limitation across communities for C. cylindrica. As such, interactions between co-occurring species may alter patterns of selection mediated by abiotic agents of selection. 相似文献
37.
D. Jeya Sundara Sharmila K. Veluraja 《Journal of biomolecular structure & dynamics》2013,31(6):641-656
Abstract Molecular mechanics and molecular dynamics studies are performed to investigate the conformational preference of cell surface higher gangliosides (GT1A and GT1B) and their interaction with Cholera Toxin. The water mediated hydrogen bonding network exists between sugar residues in gangliosides. An integrated molecular modeling, molecular mechanics, and molecular dynamics calculation of cholera toxin complexed with GT1A and GT1B reveal that, the active site of cholera toxin can accommodate these higher gangliosides. Direct and water mediated hydrogen bonding interactions stabilize these binding modes and play an essential role in defining the order of specificity for different higher ganglioside towards cholera toxin. This study identifies that the binding site of cholera toxin is shallow and can accommodate a maximum of two NeuNAc residues. The NeuNAc binding site of cholera toxin may be crucial for the design of inhibitors that can prevent the infection of cholera. 相似文献
38.
Marijke de Jong-Brink H. M. Koop W. F. de Roos J. M. Bergamin-Sassen 《Invertebrate reproduction & development.》2013,57(4):207-219
The secretory activity of the albumen gland of the freshwater snail Lymnaea stagnalis was studied morphometrically (both at the light- and at the electron-microscope level) and biochemically under the following experimental conditions: (1) glandular tissue was implanted into acceptor snails and the glandular activity of the implants was compared to that of the glands of the donors and acceptors; (2) glandular activity was measured at various periods after oviposition; and (3) the activity was measured during a 24 h cycle (diurnal activity). The results indicate that cellular release of secretion material is regulated by a nervous mechanism, whereas synthetic activity is under hormonal control. 相似文献
39.
Mathivanan Packiarajan Michel Grenon Samuel Zorn Allen T. Hopper Andrew D. White Gamini Chandrasena Xiaosui Pu Robbin M. Brodbeck Albert J. Robichaud 《Bioorganic & medicinal chemistry letters》2013,23(14):4037-4043
A new series of potent fused thiazole mGlu5 receptor positive allosteric modulators (PAMs) (10, 11 and 27–31) are disclosed and details of the SAR and optimization are described. Optimization of alkynyl thiazole 9 (Lu AF11205) led to the identification of potent fused thiazole analogs 10b, 27a, 28j and 31d. In general, substituted cycloalkyl, aryl and heteroaryl carboxamides, and carbamate analogs are mGlu5 PAMs, whereas smaller alkyl carboxamide, sulfonamide and sulfamide analogs tend to be mGlu5 negative allosteric modulators (NAMs). 相似文献
40.
AbstractSorption of lead(II) or cadmium(II) ions on humic acid particles (at pH 3.5) yields surface complexes which are sparingly soluble in the pH 3.55 region. Interaction of these species with acetic acid or dilute nitric acid released ASV labile metal species (mainly hydrated metal ion). When the pH was adjusted between 4 and 7, increasing amounts of the metal humate species (and humic acid substrate) dissolved and low levels of ASV labile species were detected. Overnight interaction with an excess of acetate ions (0.01 M) led to higher lability values (attributed to acetate/humate ligand exchange). The percentage of labile metal ion detected in acetate solutions varied with the amount of metal ion initially sorbed (range 100 to 500 mmol g?1). With the lower loadings, the ASV labile levels peaked in the pH 6–7 region (at around 12% of total sorbed cadmium, and 4% of total lead). In alkaline solutions, the percentage of labile Cd fell to about half of the peak value, but with Pb, lability values increased at pH > 8, due possibly to the formation of hydroxy complex species. The ASV lability of the Cd and Pb humates, and their 24 hour lability values (determined using a transfer to cation exchanger technique) has been compared with the behaviour of Cu and Zn humates (using similar conditions). 相似文献