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1.
Electric field-induced lateral mobility of photosystem I in the photosynthetic membrane: A study by electrophotoluminescence 总被引:2,自引:2,他引:0
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Electrophoretic movement of photosystem I (PS I) along the photosynthetic membrane of hypotonically swollen thylakoid vesicles was studied by analyzing the electric field-stimulated delayed luminescence (electrophotoluminescence) emitted from PS I. The electrophoretic mobility was inferred from the differences in electrophotoluminescence (EPL) of the photosynthetic vesicles in presence and absence of trains of low amplitude (<80 V/cm) prepulses of 1 ms duration at 4 ms spacing. The average apparent electric mobility, determined from the time course of EPL increase on one hemisphere or its decrease on the other one, as function of prepulse length and intensity was of the order of 3 · 10-5 cm2V-1s-1. The assymetric distribution of the PS I reached a steady state when the diffusional, electrostatic, and elastic forces balanced the electrophoretic driving force. A lateral diffusion coefficient of ~5 · 10-9 cm2s-1 was found for the PS I complex from the diffusional relaxation after cessation of the electric field pulse train. Experimental conditions such as concentration, temperature, and viscosity of the aqueous solution were not critical for the effect. Between 23 and 150 electron charges per moving particle were estimated from the measured electrophoretic mobility. 相似文献
2.
3.
The Photocycle of Bacteriorhodopsin in the Two-Dimensional Orthorombic Crystal Form of Purple Membrane
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Laser flash photolysis and low-temperature absorption studies of the photocycle of orthorhombic purple membrane (o-PM) reveal the existence of the same K, L, and M intermediates as found in the native hexagonal purple membrane (h-PM). However, the 0 intermediate is missing in the o-PM. The absorption spectrum of the K intermediate of o-PM is blueshifted by ~15 nm relative to the K intermediate found in the hexagonal purple membrane. The decay relaxation time constants of M in the o-PM are higher by more than an order of magnitude than the corresponding relaxation time constants in the h-PM. Similarly to the h-PM, the decay of M depends on the pulse width of excitation. The time-independent anisotropy factor obtained in photoselection studies of the M intermediate demonstrates the complete immobility of bacteriorhodopsin (bR) within the o-PM matrix. The same anisotropy factor of 0.3 obtained for o-PM and for h-PM suggests that in both crystalline lattices the transition moment of the retinal chromophore has similar angles with the plane of the membrane. The dependence of the decay kinetics of M on its occupancy may suggest the existence of kinetic coupling between neighboring bR molecules. 相似文献
4.
Globoid cell leukodystrophy, or Krabbe disease, is a severe, autosomal recessive disorder resulting from a deficiency of galactocerebrosidase (GALC) activity. GALC is responsible for the lysosomal catabolism of certain galactolipids, including galactosylceramide and psychosine. In addition to the human patients, there are several naturally occurring animal models for this disease, including the twitcher mouse, West Highland White terriers (WHWT), and Cairn terriers. All species have deficient GALC activity and have the characteristic pathological findings in the nervous system. We now describe the cloning of the canine GALC cDNA and the identification of the disease-causing mutation in both terrier breeds. The 2007-bp open reading frame is 88% identical to that in human, and the deduced amino acid sequence is about 90% identical. However, the 3′-untranslated region is about 1 kb shorter than that in the human. Two nucleotide changes were found in affected dogs, an A to C transversion at cDNA position 473 (Y158S) and a C to T transition at position 1915 (P639S). Expression studies in COS-1 cells demonstrated that the A to C change at 473 is the disease-causing mutation. A rapid test for the identification of the genotype at that position has been developed, and over 100 WHWT and Cairn terriers have been screened. This will allow breeders to mate their dogs selectively and will permit the establishment of a colony of dogs for use in therapy trials. 相似文献
5.
Christina Kennedy Natalie Doetsch Dietmar Meletzus Eduardo Patriarca Mohamad Amar Maurizio Iaccarino 《Plant and Soil》1994,161(1):43-57
A plentiful supply of fixed nitrogen as ammonium (or other compounds such as nitrate or amino acids) inhibits nitrogen fixation in free-living bacteria by preventing nitrogenase synthesis and/or activity. Ammonium and nitrate have variable effects on the ability ofRhizobiaceae (Rhizobium, Bradyrhizobium andAzorhizobium) species to nodulate legume hosts and on nitrogen fixation capacity in bacteroid cells contained in nodules or in plant-free bacterial cultures. In addition to effects on nitrogen fixation, excess ammonium can inhibit activity or expression of other pathways for utilization of nitrogenous compounds such as nitrate (through nitrate and nitrite reductase), or glutamine synthetase (GS) for assimilation of ammonium. This paper describes the roles of two key genesglnB andglnD, whose gene products sense levels of fixed nitrogen and initiate a cascade of reactions in response to nitrogen status. While work onEscherichia coli and other enteric bacteria provides the model system,glnB and, to a lesser extent,glnD have been studied in several nitrogen fixing bacteria. Such reports will be reviewed here. Recent results on the identity and function of theglnB andglnD gene products inAzotobacter vinelandii (a free-living soil diazotroph) and inRhizobium leguminosarum biovarviciae, hereinafter designatedR.l. viciae will be presented. New data suggests thatAzotobacter vinelandii probably contains aglnB-like gene and this organism may have twoglnD-like genes (one of which was recently identified and namednfrX). In addition, evidence for uridylylation of theglnB gene product (the PII protein) ofR. l. viciae in response to fixed nitrogen deficiency is presented. Also, aglnB mutant ofR. l. viciae has been isolated; its characteristics with respect to expression of nitrogen regulated genes is described. 相似文献
6.
Polysaccharide production by Aureobasidium pullulans: factors affecting polysaccharide formation 总被引:1,自引:0,他引:1
S. M. Badr-Eldin O. M. El-Tayeb H. G. El-Masry F. H. A. Mohamad O. A. Abd El-Rahman 《World journal of microbiology & biotechnology》1994,10(4):423-426
Aureobasidium pullulans NRRL 6220 synthesized polysaccharide most actively in media containing sucrose, fructose or maltose with (NH4)2SO4 (0.6 g/l) or ammonium acetate giving greatest yields of the polysaccharide. With (NH4)2SO4 at 1.2 g/l, production of polysaccharide was decreased considerably. Polysaccharide production was highest with an initial pH of 6.5 while biomass formation was better below an initial pH of 5.5. Optimum phosphate concentration for polysaccharide production was 0.03 m.S.M. Badr-Eldin, H.G. El-Masry and O.A. Abd El-Rahman are with the Microbial Chemistry Department, National Research Center, Dokki, Cairo, Egypt; F.H.A. Mohamad is with the Chemical Engineering and Pilot Plant Department, National Research Center, Dokki, Cairo, Egypt. O.M. El-Tayeb is with the Microbiology Department, Faculty of Pharmacy, Cairo University, Egypt. 相似文献
7.
8.
Anita Shepherd Danny Awty-Carroll Jason Kam Chris Ashman Elena Magenau Enrico Martani Mislav Kontek Andrea Ferrarini Stefano Amaducci Chris Davey Vanja Jurišić Gert-Jan Petrie Mohamad Al Hassan Isabelle Lamy Iris Lewandowski Emmanuel de Maupeou Jon McCalmont Luisa Trindade Kasper van der Cruijsen Philip van der Pluijm Rebecca Rowe Andrew Lovett Iain Donnison Andreas Kiesel John Clifton-Brown Astley Hastings 《Global Change Biology Bioenergy》2023,15(4):444-461
New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year−1 biomass, with potential for 1.2–1.3 EJ year−1 energy and 36.3–40.3 Mt year−1 carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over the current commercial miscanthus variety. 相似文献
9.
Spatial and temporal electroselection patterns in electric field stimulation of polarized luminescence from photosynthetic membrane vesicles 总被引:1,自引:1,他引:0
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Yosef Rosemberg Philip Rozen Shmuel Malkin Rafi Korenstein 《Biophysical journal》1992,61(6):1585-1594
Electroselection processes of charge recombination are manifested in the study of electric field induced polarized emission from photosynthetic membrane vesicles. The study explores the coupled spatial-temporal characteristics of electric field induced charge recombination by examining the dependence of the integrated polarized emission and the time dependent polarization on electric field strength. The experimental results were fitted to theoretical models by computer simulations employing empirical parameters. Simulation of the dependence of the integrated polarized components of emission on electric field strength, suggests field-dependent increased ratio between radiative and nonradiative rates of charge recombination. The observation that the initial polarization values are independent of electric field strength supports the assumption that electric field induced emission originates from the pole area and then spreads away from it towards the equator. The propagation rate of this electric field induced charge recombination from the pole area towards the equator is reflected by the decay of polarization which increases upon raising the electric field strength. Simulation of the polarization's decay, based on a calculated angle of 26.3 ± 0.4° between the transition moment of emission and the plane of the membrane, establishes coupled temporal spatial patterns of electroselection in intramembrane electron transfer invoked by exposing preilluminated photosynthetic vesicles to a homogeneous electric field. 相似文献
10.
Mohamad Kanouh Marie‐Stéphane Tixier Mireille Okassa Serge Kreiter 《Zoologica scripta》2010,39(5):450-461
Kanouh, M., Tixier, M.‐S., Okassa, M. & Kreiter, S. (2010). Phylogenetic and biogeographic analysis of the genus Phytoseiulus (Acari: Phytoseiidae) —Zoologica Scripta, 39, 450–461. The taxonomy of the genus Phytoseiulus (sub‐family Amblyseiinae), has a tumultuous and confused history. This genus currently contains four species, but in previous revisions it contained five, sometimes grouped in two genera. There are no thorough phylogenetic analyses available for the group, analyses against which taxonomic and evolutionary hypotheses could be tested. The present study aims to apply morphological and molecular data to determine phylogenetic relationships among the four species presently included in this genus plus Afroseiulus robertsi, which was previously included in this genus. The new analyses show that the species of the genus Phytoseiulus do not constitute a monophyletic group. A delineation between (i) P. macropilis, P. persimilis, P. fragariae and (ii) P. longipes and A. robertsi is observed. Biogeographic data sets showed that the Neotropical and Afrotropical regions contain the highest diversity of species of Phytoseiulus and of their host plants. Consequently, the western part of Gondwana is hypothesized to be the probable centre of origin for this taxon. 相似文献