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111.
Renata Novakova Jana Bistakova Dagmar Homerova Bronislava Rezuchova Lubica Feckova Jan Kormanec 《DNA sequence》2004,15(3):188-195
We cloned a new polyketide gene cluster, aur2, in Streptomyces aureofaciens CCM3239. Sequence analysis of the 9531-bp DNA fragment revealed 10 open reading frames, majority of which showed high similarity to the previously characterized type II polyketide synthase (PKS) genes. An unusual feature of the aur2 cluster is a disconnected organization of minimal PKS genes; ACP is located apart from the genes for ketosynthases KSalpha and KSbeta. The aur2 gene cluster was disrupted in S. aureofaciens CCM3239 by a homologous recombination, replacing the four genes (aur2A, E, F, G) including ketosynthase KSalpha, with antibiotic resistance marker gene. The disruption did not affect growth and differentiation, and disrupted strain produced spores with wild-type grey-pink pigmentation. The biochromatographic analysis of the culture extracts from S. aureofaciens wild type and aur2-disrupted strains did not reveal any difference in the pattern of antibacterial compounds. 相似文献
112.
Sarrah M'Barek Ziad Fajloun Sandrine Cestle Christiane Devaux Pascal Mansuelle Amor Mosbah Besma Jouirou Massimo Mantegazza Jurphaas van Rietschoten Mohamed El Ayeb Herv Rochat Jean‐Marc Sabatier Francois Sampieri 《Journal of peptide science》2004,10(11):666-677
Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time. 相似文献
113.
Cardoso RA Filho AA Melo MC Lyerly DM Wilkins TD Lima AA Ribeiro RA Souza GE 《Mediators of inflammation》1996,5(3):183-187
This study investigated the ability of Clostridium difficile toxin B, isolated from the VPI 10463 strain, to induce fever and neutrophilia in rats. Intravenous injection of toxin B (0.005-0.5 mug/kg) evoked a dose-dependent increase in body temperature. The febrile response to 0.5 mug/kg of the toxin started in 2.5 h, peaked at 5 h, and subsided fully within 24 h. Toxin B also induced a dosedependent neutrophilia. Pretreatment with indomethacin (2 mg/kg, i.p.) did not affect the neutrophilia induced by toxin B, but significantly reduced the febrile response measured 4 to 8 h after toxin B injection. Dexamethasone (0.5 mg/ kg) also markedly diminished the febrile response induced by toxin B. These results show that Clostridium difficile toxin B induced a febrile response susceptible to inhibition by dexamethasone and indomethacin. Furthermore, they suggest that prostaglandins are not involved in the neutrophilia caused by this toxin. 相似文献
114.
T. Macedo C. A. Fontes Ribeiro D. Cotrim P. Tavares M. T. Morgadinho M. Caramona M. T. Nunes Vicente L. Rodrigues M. G. Cardoso M. L. Keating 《Molecular neurobiology》1995,11(1-3):21-29
This work evaluated in a population of heroin and heroin plus cocaine human addicts:
- Norepinephrine (NE), epinephrine (Epi), and 3-methoxy-4-hydroxyphenylglycol (MHPG) (the principal metabolite of brain NE) plasma levels;
- Monoamine oxidase (MAO) activity; and
- 3H-imipramine specific binding to the amine carrier in platelets.
115.
116.
J M Ribeiro J J Sarkis P A Rossignol A Spielman 《Comparative biochemistry and physiology. B, Comparative biochemistry》1984,79(1):81-86
Salivary gland homogenates of female adult Aedes aegypti hydrolyzed ATP and ADP thereby defining an apyrase activity. Activity is divalent cation dependent with an optimum pH of 9.0. ATPase and ADPase activities could not be dissociated thus suggesting the presence of a true apyrase enzyme. Apyrase activity is low on the day of emergence but increases to 160 mU per pair of glands on the second day. The site at which mosquitoes probed into warm polyacrylamide gels retains apyrase activity, confirming the secretory fate of this activity. 相似文献
117.
Renata Brelińska Prof. Dr. Christoph Pilgrim Ingrid Reisert 《Cell and tissue research》1984,236(3):661-667
Summary Male Wistar rats were injected intravenously with 5-(3H)uridine-labeled lymphocytes isolated from lymph nodes of syngeneic donors and enriched in T cells. After short periods of time (3 to 120 min after injection), labeled lymphocytes were localized in spleen compartments using autoradiography to identify routes of lymphocyte movement from blood into splenic parenchyma and to follow migration pathways of recirculating lymphocytes within the periarterial lymphoid sheath (PALS). Topographical analysis of labeled lymphocytes was performed in specific planes of PALS characterized by the diameter of the arterial vessel and termed PALS large, PALS medium, and PALS small (PALS L, PALS M, PALS S, respectively). Attention was also paid to accumulations of labeled lymphocytes close to the arterial vessel wall. Initially, labeled lymphocytes were localized in PALS S and PALS M near the terminal branching of arterial vessels and in the marginal zone (MZ). We conclude that lymphocytes emigrate from blood into splenic parenchyma within two white pulp compartments: in MZ, and directly within PALS through the wall of capillary vessels. The sequential accumulation of labeled cells near arterial vessels of increasing diameter suggests that the recirculating pool of lymphocytes migrates into the central part of PALS L by two routes: from MZ, and along arterial vessels from PALS S and PALS M.R.B. was a fellow of the Alexander von Humboldt-Stiftung, on leave from the Department of Histology and Embryology, Institut of Biostructure, Academy of Medicine, ul. Swiecickiego 6, PL-60-781 Pozna, Poland. 相似文献
118.
New data on the development of polarity in the ovules during megasporogenesis and early stages of embryo sac development inOenothera-hybrids are presented. It is confirmed that allOe. hookeri-hybrids show a strong tendency to form heteropolar tetrads, with the micropylar megaspore developing into an embryo sac. This preference is seen in the delay of the second meiotic division on the chalazal side, the absence of callose in the lateral wall of the micropylar megaspore, and the accumulation of starch in this megaspore. However, homopolar tetrads, chalazal preference, and ovules with two developing embryo sacs are also observed with considerable frequency. Quantitative data on the frequency of the different developmental types are compared with earlier genetic results about competition in the haplophase. There is sufficiently good agreement to support the hypothesis ofRenner that there is a correlation between the developmental processes in the megaspore tetrad and the genetic phenomena of competition in the haplophase. 相似文献
119.
Preferred conformations of protected homo-oligo-L-glutamate peptides in CDCl3 and CDCl3/TFA mixtures
A conformational analysis of protected glutamate homo-oligopeptides Z-[Glu(OEt)]n-OEt (n = 2–7) was carried out in chloroform solution using high-resolution 1H-nmr spectroscopy. At dilute peptide concentrations, the backbone NH and α-CH resonances are well resolved and can be assigned by combining extensive homonuclear decoupling experiments with data for co-oligopeptide derivatives. The structure of these peptides in solution was then assessed using information from chemical shifts, coupling constants, temperature coefficients, and titration of each oligomer with trifluoroacetic acid (TFA). The di- and tripeptides are found to be in disordered forms in deuterochloroform (CDCl3) and CDCl3/TFA mixtures. The tetrapeptide exhibits a folded structure with intramolecular hydrogen bonding at Glu2 in CDCl3 and undergoes a transition to increasingly disordered forms as TFA is added. The pentamer to heptamer show a folded structure with a strong intramolecular hydrogen bond at Glu2 and a weaker hydrogen bond at Glu3, which are disrupted as these peptides go to random coils at high TFA/CDCl3 ratios. In addition, the N-terminal portions of these glutamate peptides appear to be involved in side chain–main chain interactions. The results support the hypothesis that protected linear homo-oligopeptides may possess two or more segments of conformation with intramolecular folding preferred near the N-terminal portion. 相似文献
120.
Anthony A. Ribeiro Robert P. Saltman Murray Goodman Manfred Mutter 《Biopolymers》1982,21(11):2225-2239
The use of 1H-nmr spectroscopy is demonstrated to be a useful analytical method to characterize the structure of synthetic peptides attached to soluble, macromolecular polyoxyethylene (POE) supports in the liquid-phase method (LPM) of peptide synthesis. We report an extensive 360-MHz 1H-nmr study of POE-bound homo-oligo-L -methionine peptides. A combination of high field and selective saturation or Redfield pulse methods allows resolution of individual backbone NH and α-CH resonances of dilute peptides in the presence of strong resonances from macromolecular POE and/or protonated solvents. The nmr spectra for the POE-bound peptides in CDCl3 are qualitatively similar to those of the low-molecular-weight Boc-L -Metn-OMe peptide esters. This corroborates other observations that POE has little effect on peptide stucture. The backbone α-CH region of peptides is overlapped by signals from the terminal oxyethylene group of POE, but the peptide side-chain and low-field backbone NH resonances are well resolved. In trifluoroethanol the Boc-(L -Met)n-NH-POE heptamer and octamer adopt the right-handed α-helical structure, and the present nmr studies provide evidence for two strong intramolecular hydrogen bonds to stabilize the helices. In water, the N-deblocked derivatives, (L -Met)n-NH-POE oligomers adopt β-sheet structure and manifest well-resolved nonequivalent NH resonances with 6–7 Hz 3JNH-CH coupling constants. 相似文献