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31.
Three peroxisomal enzymes, glycolate oxidase, urate oxidase and catalase were localized cytochemically in Psychotria punctata (Rubiaceae) leaves and Yucca torreyi (Agavaceae) seedling root tips, both of which contain developing and mature calcium-oxalate raphide crystal idioblasts. Glycolate-oxidase (EC 1.1.3.1) and catalase (EC 1.11.1.6) activities were present within leaftype peroxisomes in nonidioblastic mesophyll cells in Psychotria leaves, while urate-oxidase (EC 1.7.3.3) activity could not be conclusively demonstrated in these organelles. Unspecialized peroxisomes in cortical parenchyma of Yucca roots exhibited activities of all three enzymes. Reactionproduct deposits attributable to glycolate-oxidase activity were never observed in peroxisomes of any developing or mature crystal idioblasts of Psychotria or Yucca. Catalase localization indicates that idioblast microbodies are functional peroxisomes. The apparent absence of glycolate oxidase in crystal idioblasts of Psychotria and Yucca casts serious doubt that pathways involving this enzyme are operational in the synthesis of the oxalic acid precipitated as calcium-oxalate crystals in these cells.Abbreviations AMPD
2-amino-2-methyl-1,3-propandiol
- CTEM
conventional transmission electron microscopy
- DAB
3,3-diaminobenzidine tetrahydrochloride
- HVEM
high-voltage electron microscopy 相似文献
32.
Rapid recycling of triose phosphates in oak stem tissue 总被引:10,自引:3,他引:7
S. A. HILL J. S. WATERHOUSE E. M. FIELD V. R. SWITSUR T. AP REES 《Plant, cell & environment》1995,18(8):931-936
We report the carbon-13 and oxygen-18 isotope ratios in cellulose from the early and late wood of pedunculate oak (Quercus robur L.). The δ13 C value of the early wood correlates best with that of the late wood of the previous year. The δ18O value of the early wood correlates best with that of the late wood of the same year. We suggest that a biochemical explanation of these data is that there is a rapid cycle between hexose monophosphates and triose phosphates in oak stem tissue during cellulose synthesis. Evidence in support of this explanation is provided by the intramolecular distribution of 14C in labelled fructose extracted from cores of wood that had been supplied with [1?14C]- and [6-14C]glucose. 相似文献
33.
CM Ward AP Wilkinson S Bramham HA Lee HW-S Chan GW Butcher A Hutchings MRA Morgan 《Mycotoxin Research》1990,6(2):73-83
From a single aflatoxin B1 oxime — bovine serum albumin conjugate, polyclonal and monoclonal antibody preparations were produced. The four rabbit polyclonal antisera were specific for aflatoxin Bi in a microtitration plate enzyme — linked immunosorbent assay. The monoclonal antibodies showed a wide range of differing specificities, recognizing, for example, aflatoxins B1, B2, G1 and G2; B1 and B2; B1 and G1; and G1 alone. No antibody preparations reacted with aflatoxin M1. The significance of these results to the strategy of anti-aflatoxin antibody production for use in quantitative enzyme immunoassays is discussed. 相似文献
34.
Beziehungen Zwischen Wurzelwachstum,Transpiration und CO2-Gaswechsel bei Einigen Kakteen 总被引:1,自引:0,他引:1
Walter Kausch 《Planta》1965,66(3):229-238
35.
Ultrafast Charge Generation Pathways in Photovoltaic Blends Based on Novel Star‐Shaped Conjugated Molecules 下载免费PDF全文
Oleg V. Kozlov Yuriy N. Luponosov Sergei A. Ponomarenko Nina Kausch‐Busies Dmitry Yu Paraschuk Yoann Olivier David Beljonne Jérôme Cornil Maxim S. Pshenichnikov 《Liver Transplantation》2015,5(7)
The quest for new materials is one of the main factors propelling recent advances in organic photovoltaics. Star‐shaped small molecules (SSMs) have been proven promising candidates as perspective donor material due to the increase in numbers of excitation pathways caused by the degeneracy of the lowest unoccupied molecular orbital (LUMO) level. In order to unravel the pathways of the initial photon‐to‐charge conversion, the photovoltaic blends based on three different SSMs with a generic structure of N(phenylene‐nthiophene‐dicyanovinyl‐alkyl)3 (n = 1–3), and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) acceptor are investigated by ultrafast photoinduced absorption spectroscopy assisted by density functional theory calculations. It is shown that both electron transfer from SSMs to PC71BM and hole transfer from PC71BM to SSMs are equally significant for generation of long‐lived charges. In contrast, intramolecular (intra‐SSM) charge separation results in geminate recombination and therefore constitutes a loss channel. Overall, up to 60% of long‐lived separated charges are generated at the optimal PC71BM concentrations. The obtained results suggest that further improvement of the SSM‐based solar cells is feasible via optimization of blend morphology and by suppressing the intra‐SSM recombination channel. 相似文献
36.
Inverted,Environmentally Stable Perovskite Solar Cell with a Novel Low‐Cost and Water‐Free PEDOT Hole‐Extraction Layer 下载免费PDF全文
37.
Rafael AP Guércio Anna Shevchenko Andrej Shevchenko Jorge L López-Lozano Jaime Paba Marcelo V Sousa Carlos AO Ricart 《Proteome science》2006,4(1):11-14
Background
Bothrops atrox is responsible for the majority of snakebite accidents in the Brazilian Amazon region. Previous studies have demonstrated that the biological and pharmacological activities of B. atrox venom alter with the age of the animal. Here, we present a comparative proteome analysis of B. atrox venom collected from specimens of three different stages of maturation: juveniles, sub-adults and adults. 相似文献38.
Leaf and callus tissues of a creeping bentgrass cultivar (Penn A4) had high nuclease activities that degraded exogenously added plasmid DNA. When callus tissue was incubated for 24 h with heparin, spermidine, aurintricarboxylic acid or polyethylene glycol, only heparin and spermidine were effective as in vitro nuclease inhibitors, protecting exogenously added plasmid DNA from degradation. When -glucuronidase (GUS) reporter gene activity was evaluated in heparin-treated (0.6%), 14-month old callus following microprojectile bombardment, GUS activity increased 1000-fold compared to equivalent aged untreated Penn A4 callus. Similar enhancement from heparin pretreatment (0.6% or 1.2%) was not observed in 6-month old callus. This is likely due to much higher activities of nuclease in the younger callus. 相似文献
39.
Females of the sea urchin Strongylocentrotus purpuratus differ in the structures of their egg jelly sulfated fucans 总被引:1,自引:0,他引:1
The egg jelly coats of sea urchins contain sulfated fucans which bind to a
sperm surface receptor glycoprotein to initiate the signal transduction
events resulting in the sperm acrosome reaction. The acrosome reaction is
an ion channel regulated exocytosis which is an obligatory event for sperm
binding to, and fusion with, the egg. Approximately 90% of individual
females of the sea urchin Strongylocentrotus purpuratus spawned eggs having
only one of two possible sulfated fucan electrophoretic isotypes, a slow
migrating (sulfated fucan I), or a fast migrating (sulfated fucan II)
isotype. The remaining 10% of females spawned eggs having both sulfated
fucan isotypes. The two sulfated fucan isotypes were purified from egg
jelly coats and their structures determined by NMR spectroscopy and
methylation analysis. Both sulfated fucans are linear polysaccharides
composed of 1-->3-linked alpha-L-fucopyranosyl units. Sulfated fucan I
is entirely sulfated at the O -2 position but with a heterogeneous
sulfation pattern at O -4 position. Sulfated fucan II is composed of a
regular repeating sequence of 3 residues, as follows: [3-alpha-L-Fuc p -
2,4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-
1]n. Both purified sulfated fucans have approximately equal potency in
inducing the sperm acrosome reaction. The significance of two structurally
different sulfated fucans in the egg jelly coat of this species could
relate to the finding that the sperm receptor protein which binds sulfated
fucan contains two carbohydrate recognition modules of the C-type lectin
variety which differ by 50% in their primary structure.
相似文献
40.
Fucose is a major constituent of the protein- and lipid-linked glycans of
the various life-cycle stages of schistosomes. These fucosylated glycans
are highly antigenic and seem to play a role in the pathology of
schistosomiasis. In this article we describe the identification and
characterization of two fucosyltransferases (FucTs) in cercariae of the
avian schistosome Trichobilharzia ocellata, a GDP-Fuc:[Galbeta1--
>4]GlcNAcbeta-R alpha1-->3-FucT and a novel GDP-Fuc:Fucalpha-R
alpha1-- >2-FucT. Triton X-100 extracts of cercariae were assayed for
FucT activity using a variety of acceptor substrates. Type 1 chain
(Galbeta1- ->3GlcNAc) based compounds were poor acceptors, whereas those
based on a type 2 chain (Galbeta1-->4GlcNAc), whether
alpha2'-fucosylated, alpha3'-sialylated, or unsubstituted, and whether
present as oligosaccharide or contained in a glycopeptide or glycoprotein,
all served as acceptor substrates. In this respect the schistosomal alpha3-
FucT resembles human FucT V and VI rather than other known FucTs. N-
ethylmaleimide, an inhibitor of several human FucTs, had no effect on the
activity of the schistosomal alpha3-FucT, whereas GDP-beta-S was strongly
inhibitory. Large scale incubations were carried out with
Galbeta1-->4GlcNAc, GalNAcbeta1-->4GlcNAcbeta-O -(CH2)8COOCH3 and
Fucalpha1-->3GlcNAcbeta1-->2Man as acceptor substrates and the
products of the incubations were isolated using a sequence of
chromatographic techniques. By methylation analysis and 2D-TOCSY and
ROESY1H-NMR spectroscopy the products formed were shown to be Galbeta1--
>4[Fucalpha1-->2Fucalpha1-->3]GlcNAc,
GalNAcbeta1-->4[Fucalpha1-- >2Fucalpha1-->3]GlcNAcbe
ta-O-(CH2)8COOCH3, and Fucalpha1-->2Fucalpha1--
>3GlcNAcbeta1-->2Man, respectively. It is concluded that the alpha2-
FucT and alpha3-FucT are involved in the biosynthesis of the (oligomeric)
Lewisx sequences and the Fucalpha1-->2Fucalpha1-->3GlcNAc structural
element that have been described on schistosomal glycoconjugates.
相似文献