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81.
Properties of a Large Complex with NADH Dehydrogenase Activity from Barley Thylakoids 总被引:4,自引:0,他引:4
Cuello Juan; Quiles Maria Jose; Albacete Maria Eugenia; Sabater Bartolome 《Plant & cell physiology》1995,36(2):265-271
When assays for NAD(P)H-ferricyanide oxidoreductases were performed,activities specific for NADH (0.23 unit (mg protein)1)and NADPH (0.68 unit (mg protein)1) were detected inchloroplasts isolated from leaves of barley (Hordeum vulgareL.). Activities of chloroplast NADH- and NADPH-ferricyanideoxidoreductase were 5-fold and 25-fold higher, respectively,than the maximum activity that could be attributed to mitochondrialcontamination. Moreover, most of the chloroplast NADH-ferricyanideoxidoreductase (60 to 80%) was solubilized by deoxycholate (DOC)from thylakoids as a single, high-molecular-mass complex thatwas distinguishable from the mitochondrial complex by its lowerelectrophoretic mobility in 3% polyacrylamide, as revealed byreduction of nitro blue tetrazolium (NBT) in the presence ofNADH or NADPH on gels after electrophoresis. The stroma yieldeda single band of a dehydrogenase (66 kDa) that used NADH asits electron donor. Several NADPH-dependent activities weredetected after electrophoresis of the stromal fraction. Moreover,chloroplast-specific activities could be distinguished frommitochondrial activities on the basis of the specificity ofthe donor and the acceptor of electrons, the dependence of theactivities on pH, and the sensitivity to various inhibitors.Km values for NADH (26 µM) and NADPH (75 µM) werein the same range as those of mitochondrial activities. Mostof the NADPH-dependent activity probably corresponds to thechloroplast ferredoxin-NADP+ oxidoreductase. The possibilityis discussed that thylakoid NADH dehydrogenase(s) might be theproduct of chloroplast ndh genes and that this activity is involvedin chlororespiration. (Received April 25, 1994; Accepted December 5, 1994) 相似文献
82.
Jesús Zurdo Miguel A. Centeno José A. Odriozola Concepción Fernández-Cabrera Juan M. Ramírez 《Photosynthesis research》1995,46(1-2):363-369
In previous work (Zurdo J, Fernández-Cabrera C and Ramírez JM (1993) Biochem J 290: 531–537), it had been shown that selective extraction of the carotenoid from the light-harvesting protein 2 (LH2) of Rhodobacter capsulatus induced the dissociation of 800-nm absorbing bacteriochlorophyll (Bchl), a 10-nm red shift of 854-nm Bchl, and a decrease of the stability of the protein in detergent solution. In the present study, the Fourier transform Raman and near-infrared circular dichroism spectra of native and carotenoid-depleted LH2 membrane preparations were compared. It was found that while the coupled carbonyls of 854-nm Bchl remained specifically H-bonded to the peptides after carotenoid extraction, the optical activity of the near-infrared electronic transition was significantly altered. Given the excitonic origin of such optical activity, our data suggest that carotenoid extraction elicits a rearrengement of the chromophore cluster and of the associated polypeptide subunits. This implies a significant role of the carotenoid in maintaining the native quaternary structure of the protein, which would be consistent with the observed dissociation of 800-nm Bchl and the loss of solubilized LH2 stability that result from carotenoid removal. There is no evidence for a similar role of the carotenoid in the LH1 protein.Abbreviations Bchl
bacteriochlorophyll
- FT
Fourier transform
- CD
circular dichroism
- LH1 and LH2
the bacterial light-harvesting proteins 1 and 2
In memoriam of Daniel I. Arnon. 相似文献
83.
Twelve cDNAs corresponding to mRNAs inducible by ethylene were isolated by differential screening of a cDNA library from ethylene-treated Citrus sinensis fruits. Northern analysis of RNA extracted from flavedo of ethylene-treated fruits and from fruits at different maturation stages showed that some of the mRNAs corresponding to these cDNAs were regulated both by ethylene treatment and during fruit maturation. The effect of exogenous ethylene on leaves and of endogenous ethylene on flowers showed that gene induction was not restricted to the flavedo tissue. The possible role of ethylene during maturation of the non-climacteric Citrus fruit is discussed. 相似文献
84.
85.
Four xylanase preparations that are commercially available, namely Cartazyme from Sandoz, Ecopulp from Alko-ICI, Irgazyme from Ciba-Genencor and Pulpzyme HB from Novo Nordisk, were tested in bleaching experiments of kraft pulps from Pinus radiata. The main objective of this study was to optimize a reduction in the consumption of chlorine dioxide in the bleaching sequences C90/D10EoDED, C70/D30EoDED and D100EDED. Enzymatic treatments led to savings of ClO2 between 3.5 and 3.9 kg per air-dried tons (ADT) in the three bleaching sequences, without affecting the target brightness of the pulps. In these assays, some minor although reproducible differences in the performance of the enzymes were observed. In most cases, xylanase treatment partially affected the beatability of the pulps, measured as the number of revolutions in the PFI mill required to reach the same tensile index as the respective controls. 相似文献
86.
Diversity, abundance or rare species as a target for the conservation of mammalian carnivores: a case study in Southern Spain 总被引:6,自引:2,他引:4
Alejandro Travaini Miguel Delibes Pablo Ferreras Francisco Palomares 《Biodiversity and Conservation》1997,6(4):529-535
Management goals in protected areas and/or communities usually include diversity as one of the most valuable and confident criteria. Nevertheless, the use of diversity and related indices as a means of evaluating successful management practices could produce conflicting results. Here we report a case study in one of the most important European protected areas. After 6 years of intensive conservation management of the Don~ana National Park, the general abundance and numbers of the target single-species conservation plan (the Iberian lynx) increased, although carnivore community diversity and evenness decreased. This was a result of a disproportionate increase of an oportunistic native species, the red fox. We propose the combined use of diversity, richness and evenness indices when monitoring management practices such as those reported here. 相似文献
87.
Preliminary investigation of feeding performance of larvae of early red-spotted grouper, Epinephelus coioides, reared with mixed zooplankton 总被引:5,自引:0,他引:5
Masanori Doi Joebert D. Toledo Ma Salvacion N. Golez Miguel de los Santos Atsushi Ohno 《Hydrobiologia》1997,358(1-3):259-263
Larvae of red-spotted grouper, Epinephelus coioides, were reared inoutdoor tanks with nauplii of copepods (mainly Pseudodiaptomus annandaleiand Acartia tsuensis) and/or rotifers, Brachionus rotundiformis. Grouperlarvae successfully started feeding on early stage nauplii even though theirabundance was as low as approximately 100 individuals l–1 andshowed better survival and growth thereafter compared to those fed withrotifers only. Incidence of feeding reached 100% on day 4 whennauplii were available and only on day 9 when rotifers were given alone.Larvae seemed to be poor feeders at the onset of feeding, attempting tocapture any food organisms in the tank water. Selective feeding ability oflarvae started from day 4 and the larvae then preferred to feed on medium-and large-size nauplii rather than on rotifers as they grew. Larvae appearedto have a better chance at surviving in the presence of early stage nauplii,which were probably caught more easily than rotifers. 相似文献
88.
Contribution of Mutation and RNA Recombination to the Evolution of a Plant Pathogenic RNA 总被引:10,自引:0,他引:10
Miguel A. Aranda Aurora Fraile Joaquín Dopazo José M. Malpica Fernando García-Arenal 《Journal of molecular evolution》1997,44(1):81-88
The nucleotide sequence of 17 variants of the satellite RNA of cucumber mosaic virus (CMV-satRNA) isolated from field-infected
tomato plants in the springs of 1989, 1990, and 1991 was determined. The sequence of each of the 17 satRNAs was unique and
was between 334 and 340 nucleotides in length; 57 positions were polymorphic. There was much genetic divergence, ranging from
0.006 to 0.141 nucleotide substitutions per site for pairwise comparisons, and averaging 0.074 for any pair. When the polymorphic
positions were analyzed relative to a secondary structure model proposed for CMV-satRNAs, it was found that there were significantly
different numbers of changes in base-paired and non–base-paired positions, and that mutations that did not disrupt base pairing
were preferred at the putatively paired sites. This supports the concept that the need to maintain a functional structure
may limit genetic divergence of CMV-satRNA. Phylogenetic analyses showed that the 17 CMV-satRNA variants clustered into two
subgroups, I and II, and evolutionary lines proceeding by the sequential accumulation of mutations were apparent. Three satRNA
variants were outliers for these two phylogenetic groups. They were shown to be recombinants of subgroup I and II satRNAs
by calculating phylogenies for different molecular regions and by using Sawyer's test for gene conversion. At least two recombination
events were required to produce these three recombinant satRNAs. Thus, recombinants were found to be frequent (∼17%) in natural
populations of CMV-satRNA, and recombination may make an important contribution to the generation of new variants. To our
knowledge this is the first report of data allowing the frequency of recombinant isolates in natural populations of an RNA
replicon to be estimated.
Received: 14 May 1996 / Accepted: 17 July 1996 相似文献
89.
Pietro Paolo Fanciullt Miguel Gaju Carmen Bach Francesco Frati 《Biological journal of the Linnean Society. Linnean Society of London》1997,62(4):533-551
Different species of the bristletail genus Lepismachilis were collected in 14 localities in Italy and Spain and an allozyme electrophoretic survey was carried out to estimate the degree of genetic variability and differentiation at intra- and interspecific levels. Four morphological species were initially identified (L osellai, L. y-signata, L. affinis, L. targionii), but the electrophoretic analysis demonstrated the presence of two additional species among the individuals of L. targionii (Lepismachilis spl and sp2). The validity of these species and their differentiation from L targionii were demonstrated by the fixation of alternative allelic patterns at several loci (7 in Lepismachilis spl and 8 in Lepismachilis sp2), coupled with fixed, previously undetected, morphological differences. In addition, Lepismachilis sp2 was sympatric with L. targionii in three collecting sites, where the fixation of alternative allelic patterns unequivocally demonstrated reproductive isolation. Genetic variability did not seem to be correlated with local ecological factors, and differences between species should rather be explained by different historical factors. Low levels of gene flow, estimated with two different indirect methods, were observed in L. targionii and L. y-signata, and were due to high levels of structuring among populations. Genetic differentiation among conspecific populations was not correlated to their geographical arrangement and the presence of loci fixed for different alleles among them suggested that stochastic factors (such as genetic drift) may have played a role in determining genetic differentiation of geographically isolated populations. Genetic divergence values indicated that the six species are well differentiated and allozyme profiles were diagnostic for all of them. On the other hand, allozyme data did not provide adequate information to resolve evolutionary relationships among the species, nor did they confirm the validity of the two subgenera (Lepismachilis and Berlesilis) in which the genus Lepismachilis is traditionally divided. 相似文献
90.
Miguel Â. Marini Michael E. Weale 《Biological journal of the Linnean Society. Linnean Society of London》1997,62(2):195-208
Predators are often expected to vary their relative predation rates according to the frequency of prey types in the environment (frequency-dependent predation). The underlying cause for this must lie in some dependency of absolute predation rates on the density of prey types in the environment (density-dependent predation). However, frequency-dependent predation may either be caused by 'simple' density-dependent predation, in which the absolute predation rate on a given prey type depends purely on the density of that type, or by more complex responses in which absolute rates depend also on the density of other prey types. It is usually difficult to distinguish the underlying cause of frequency-dependent predation, because frequencies tend to change as densities change. Here, we describe the results of an experiment conducted to disentangle these phenomena under two prey richness (low and high) conditions. We used artificial bird nests (placed on shrubs and on saplings) baited with quail eggs placed in natural forests as models of natural bird nests. Our results indicate that both the absolute and relative predation rates on the prey types may vary in complex ways. Predation rates depend on a complex interaction between the prey's own density, other prey density and the diversity of prey in the environment. Neglecting to include, or consider, these complexities into analyses may lead to erroneous conclusions in studies of absolute or relative predation rates. 相似文献