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21.
Kontos F Maniati M Costopoulos C Gitti Z Nicolaou S Petinaki E Anagnostou S Tselentis I Maniatis AN 《Journal of microbiological methods》2004,56(2):291-294
The accuracy of the Bactec MGIT 960 system for susceptibility testing of 177 clinical isolates of Mycobacterium tuberculosis to first line drugs (isoniazid, rifampicin, ethambutol and streptomycin) was compared with the agar reference method. The sensitivity, the ability to detect resistance, of the MGIT system was 100%, while the specificity, the ability to detect susceptibility, ranged from 98.6% to 100% for all drugs tested. 相似文献
22.
Slavov S van Onckelen H Batchvarova R Atanassov A Prinsen E 《Journal of plant physiology》2004,161(7):847-853
Broomrapes (Orobanche spp.) are parasitic plants, whose growth and development fully depend on the nutritional connection established between the parasite and the roots of the respective host plant. Phytohormones are known to play a role in establishing the specific Orobanche-host plant interaction. The first step in the interaction is seed germination triggered by a germination stimulant secreted by the host-plant roots. We quantified indole-3-acetic acid (IAA) and abscisic acid (ABA) during the seed germination of tobacco broomrape (Orobanche ramosa) and sunflower broomrape (O. cumana). IAA was mainly released from Orobanche seeds in host-parasite interactions as compared to non-host-parasite interactions. Moreover, germinating seeds of O. ramosa released IAA as early as 24 h after the seeds were exposed to the germination stimulant, even before development of the germ tube. ABA levels remained unchanged during the germination of the parasites' seeds. The results presented here show that IAA production is probably part of a mechanism triggering germination upon the induction by the host factor, thus resulting in seed germination. 相似文献
23.
Ivanov IN Mitkova N Reye AL Hübschen JM Vatcheva-Dobrevska RS Dobreva EG Kantardjiev TV Muller CP 《Applied and environmental microbiology》2011,77(15):5562-5565
We report on the identification of two new Francisella-like endosymbionts (FLEs) found in three different tick species from Bulgaria. The FLEs were characterized by 16S rRNA and tul4 gene sequencing and seem to lack the molecular marker RD1. These two new taxa seem to be facultative secondary endosymbionts of ticks. 相似文献
24.
Wright NT Varney KM Ellis KC Markowitz J Gitti RK Zimmer DB Weber DJ 《Journal of molecular biology》2005,353(2):410-426
S100A1 is an EF-hand-containing Ca(2+)-binding protein that undergoes a conformational change upon binding calcium as is necessary to interact with protein targets and initiate a biological response. To better understand how calcium influences the structure and function of S100A1, the three-dimensional structure of calcium-bound S100A1 was determined by multidimensional NMR spectroscopy and compared to the previously determined structure of apo. In total, 3354 nuclear Overhauser effect-derived distance constraints, 240 dihedral constraints, 160 hydrogen bond constraints, and 362 residual dipolar coupling restraints derived from a series of two-dimensional, three-dimensional, and four-dimensional NMR experiments were used in its structure determination (>21 constraints per residue). As with other dimeric S100 proteins, S100A1 is a symmetric homodimer with helices 1, 1', 4, and 4' associating into an X-type four-helix bundle at the dimer interface. Within each subunit there are four alpha-helices and a short antiparallel beta-sheet typical of two helix-loop-helix EF-hand calcium-binding domains. The addition of calcium did not change the interhelical angle of helices 1 and 2 in the pseudo EF-hand significantly; however, there was a large reorientation of helix 3 in the typical EF-hand. The large conformational change exposes a hydrophobic cleft, defined by residues in the hinge region, the C terminus, and regions of helix 3, which are important for the interaction between S100A1 and a peptide (TRTK-12) derived from the actin-capping protein CapZ. 相似文献
25.
The coaggregation of Streptococcus mitis strain J22 in the early stages of dental plaque formation has been shown to result from interaction of cell wall polysaccharides with lectins on the surface of other oral bacterial species. This bacterium was grown in a medium containing 13C as the sole carbon source. We have isolated the lectin receptor polysaccharide from this strain with full enrichment in 13C and have determined a number of two-bond and three-bond 13C-1H coupling constants from measurements of the offsets in two-dimensional homonuclear nmr spectra [exclusive correlated spectroscopy (E-COSY) method]. A scheme for reliable extraction of these coupling constants from homonuclear Hartmann-Hahn and nuclear Overhauser effect spectroscopy spectra is tested in model compounds. We interpret the three-bond coupling across the glycosidic linkage in terms of dihedral angles in order to provide conformational information to supplement molecular modeling and nuclear Overhauser effect data. We show that the E-COSY method works well even for coupling constants smaller than the nmr line width and that a number of the 3JCH across the glycosidic linkage are in the range of 1–2 Hz, which is much smaller than many previously reported values. © 1994 John Wiley & Sons, Inc. 相似文献
26.
Yuan-Min Shen Wen-Hsin Chung Tung-Chin Huang Rossitza Rodeva Ting-Hsuan Hung 《Mycoscience》2018,59(3):218-228
Three rust fungi from high mountains and pear-producing areas in Taiwan were described using morphological and molecular data based on 34 specimens. Gymnosporangium corniforme was demonstrated to produce spermogonia and aecia on Sorbus randaiensis based on molecular analyses and inoculation experiments. The pear rust pathogen G. unicorne was discovered in Taiwan for the first time. Gymnosporangium niitakayamense sp. nov. was observed on the leaves of Photinia niitakayamensis. It was distinct from other species in peridial cell wall structures, i.e., smooth outer wall, rugose side wall, and coralloid projections on the inner wall, and in having echinulate aeciospores. 相似文献
27.
Michel Schalk Francisco Cabello-Hurtado Marie-Agnès Pierrel Rossitza Atanossova Patrick Saindrenan Danièle Werck-Reichhart 《Plant physiology》1998,118(1):209-218
Piperonylic acid (PA) is a natural
molecule bearing a methylenedioxy function that closely mimics the
structure of trans-cinnamic acid. The CYP73A subfamily
of plant P450s catalyzes trans-cinnamic acid
4-hydroxylation, the second step of the general phenylpropanoid
pathway. We show that when incubated in vitro with yeast-expressed
CYP73A1, PA behaves as a potent mechanism-based and quasi-irreversible
inactivator of trans-cinnamate 4-hydroxylase.
Inactivation requires NADPH, is time dependent and saturable
(KI = 17 μm,
kinact = 0.064 min−1), and
results from the formation of a stable metabolite-P450 complex
absorbing at 427 nm. The formation of this complex is reversible with
substrate or other strong ligands of the enzyme. In plant microsomes PA
seems to selectively inactivate the CYP73A P450 subpopulation. It does
not form detectable complexes with other recombinant plant P450
enzymes. In vivo PA induces a sharp decrease in 4-coumaric acid
concomitant to cinnamic acid accumulation in an elicited tobacco
(Nicotiana tabacum) cell suspension. It also strongly
decreases the formation of scopoletin in tobacco leaves infected with
tobacco mosaic virus.The phenylpropanoid metabolism is a plant-specific pathway leading
to compounds of extremely diverse structure and function (Dixon and
Paiva, 1995; Werck-Reichhart, 1995). It is involved in the formation of
quantitatively major biopolymers such as lignin and suberin, but also
in the biosynthesis of signaling molecules such as salicylic acid and
isoflavonoids in flower pigments, UV protectants such as anthocyanins,
flavonoids, and coumarins, and several classes of phytoalexins. The
upstream part of the phenylpropanoid metabolism, which branches from
the shikimate pathway at the level of l-Phe, consists of a
core of three enzymatic steps leading to 4-coumaroyl CoA (Fig.
(Fig.1).1). This set of three reactions, often
called the general phenylpropanoid pathway, controls the flux of
metabolites toward all families of compounds derived from the C6-C3
skeleton of Phe. Compounds with a C6-C1 structure are not strictly
phenylpropanoids, but also derive from l-Phe. They
originate from the core pathway intermediates cinnamic acid or
4-coumaric acid (Yalpani et al., 1993). Molecules with a C6-C1 backbone
include benzoic and salicylic acids and economically important
compounds such as vanillin.
Figure 1Branching and inhibitors of the phenylpropanoid
pathway. AOPP, α-Amino-β-phenylpropionic acid; MDCA,
methylenedioxycinnamic acid.The second step in the core phenylpropanoid pathway is the
hydroxylation of trans-cinnamic acid to 4-coumaric acid. The
reaction is catalyzed by C4H, a member of the superfamily of Cyt P450
heme-thiolate proteins. P450s are monooxygenases that catalyze the
oxidation of a remarkably broad range of endogenous and exogenous
chemicals in all organisms. In plants they play important roles in
biosynthetic pathways, including those of sterols, isoprenoids,
alkaloids, oxygenated fatty acids, and phenylpropanoids (Bolwell et
al., 1994; Durst and O''Keefe, 1995; Schuler, 1996). They are also
involved in the metabolism and sometimes in the activation of many
herbicides, insecticides, and other xenobiotics. CYP73A1 is a C4H from
Jerusalem artichoke (Helianthus tuberosus). Its coding
sequence was isolated from tuber tissues (Teutsch et al., 1993) and
expressed in yeast (Urban et al., 1994). The yeast-expressed enzyme is
catalytically active and capable of hydroxylating cinnamic acid with a
very high efficiency (kcat ranging from 100
to 400 min−1).The high activity of the recombinant enzyme led us to investigate its
activity toward other potential substrates, natural plant components,
and xenobiotics. Several exogenous molecules were thus found to be
substrates of CYP73A1 (Pierrel et al., 1994; Schalk et al., 1997). The
efficiency of the metabolism of the xenobiotic molecules largely relied
on their structural analogy to the natural substrate. A systematic
structure-activity study recently led to the characterization of some
good alternative substrates and high-affinity inhibitors of the enzyme,
and of the structural requirements for an efficient binding into the
active site of CYP73A1 (Schalk et al., 1997). The ideal ligand of C4H
was thus defined as a rigid hydrophobic backbone of the size of a
bicyclic aromatic structure (e.g. naphthalene), bearing one or several
small negatively charged substituent(s) centered around carbon 2 of the
naphthalene ring, the prototype alternative substrate being 2-naphthoic
acid (Fig. (Fig.2).
2).
Figure 2Structural analogy between substrates of
CYP73A1.PA is a natural molecule extracted from the bark of the Paracoto tree
that roughly fulfills all of these requirements. PA contains a MDP
function at a position suitable for oxidative attack by CYP73A1. Many
compounds with MDP function have been shown to inhibit mammalian or
insect P450 enzymes both in vitro and in vivo (Franklin, 1977;
Wilkinson et al., 1984; Ortiz de Montellano and Correia, 1995). They
were shown to act as mechanism-based inactivators and to require
P450-catalyzed metabolism to generate a MI forming a stable complex
with the enzyme (Franklin, 1971). Available data suggest that the MI is
likely a carbene that binds as the sixth coordinant to the heme iron
(Mansuy et al., 1979).We have tested PA inhibition of recombinant CYP73A1 and show that it
behaves as a very potent, mechanism-based inhibitor of C4H. It is
effective in vitro on the recombinant enzyme, being far more efficient
than other MDP compounds. It is apparently selective for C4H. Assays
performed in vivo on tobacco (Nicotiana tabacum) leaves and
cell cultures indicate that it can be used to inactivate C4H and to
block the input of precursors into the main C6-C3 pathway. To our
knowledge, it is the first selective and quasi-irreversible inhibitor
of the C4H so far described. 相似文献
28.
Damien Afoufa-Bastien Anna Medici Julien Jeauffre Pierre Coutos-Thévenot Rémi Lemoine Rossitza Atanassova Maryse Laloi 《BMC plant biology》2010,10(1):245
Background
In higher plants, sugars are not only nutrients but also important signal molecules. They are distributed through the plant via sugar transporters, which are involved not only in sugar long-distance transport via the loading and the unloading of the conducting complex, but also in sugar allocation into source and sink cells. The availability of the recently released grapevine genome sequence offers the opportunity to identify sucrose and monosaccharide transporter gene families in a woody species and to compare them with those of the herbaceous Arabidopsis thaliana using a phylogenetic analysis. 相似文献29.
Plamen Todorov Elena Hristova Rossitza Konakchieva Antoaneta Michova Josif Dimitrov 《Cell biology international》2010,34(5):455-462
Fetal stem cells possess some intriguing characteristics, which delineate them as promising cellular therapeutics. They are less immunogenic, at lower stage of differentiation and have higher potential for repopulation and migration. Furthermore, the fetal stem cells secrete a set of cytokines and growth factors, which stimulate the regeneration of the recipient tissue. The present study indicated that the adhesive fraction of human fetal liver cells possessed the morphological characteristics of mesenchymal stem cells, as well as potential to differentiate into adipocyte and osteoblast lineages. The immunophenotypic analysis showed that the cells expressed CD13, CD73, CD90 and CD105 (typical for mesenchymal stem cells) and lacked the haematopoietic lineage markers CD34 and CD45. Addressing the issue of the low‐temperature storage of the human fetal liver cells, four different methods for cryopreservation were assessed: conventional slow freezing, program freezing and two vitrification protocols. The obtained results demonstrated that the cells were cryotolerant and maintained their properties and differentiation potential after thawing. Program freezing showed to be the most efficient method for cryopreservation of the investigated cells. 相似文献
30.
Kontos F Nicolaou S Kostopoulos C Gitti Z Petinaki E Maniati M Anagnostou S Raftopoulou A Papageorgiou P Scrioubellou A Tselentis I Maniatis AN 《Journal of microbiological methods》2003,55(1):331-333
One hundred and fifty clinical isolates of Mycobacterium tuberculosis were tested for susceptibility to pyrazinamide using the fully automated Bactec MGIT 960 system and the radiometric Bactec 460TB system. The overall concordance rate between MGIT 960 and radiometric system was 100% and the mean turnaround times to report the susceptibility test results were almost identical (6.37 and 6.8 days, respectively). 相似文献