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971.
972.
The molecular properties of a novel membrane quinol oxidase from the marine bacterium Pseudomonas nautica 617 are presented. The protein contains 2b hemes/mole which may be distinguished by EPR spectroscopy but not by optical spectroscopy and electrochemistry. Respiration, though being cyanide insensitive, is not inhibited by carbon monoxide and oxygen reduction is carried out only half-way with production of hydrogen peroxide. The terminal oxidase represents, therefore, a unique example in the large family of terminal oxidases known up to date. 相似文献
973.
In higher plant cells, there are some enzymes capable of utilizing pyrophosphate (PPi ) as an energy donor. Among these, membrane-bound proton pumping pyrophosphatases (H+ -PPi ase) have been identified. In addition to the well-known vacuolar H+ -PPi ase (V-PPi ase), there is evidence for the presence of a mitochondrial H+ -PPi ase. This enzyme is localized on the inner surface of the inner membrane and catalyzes the specific hydrolysis of PPi , coupled to proton transport, with a H+ /PPi stoichiometry of ca 2. This activity is Mg2+ -requiring, is stimulated by monovalent cations, and is inhibited by Ca2+ , F− and diphosphonates. The H+ -PPi ase contains a catalytic head which is constituted by a 35-kDa protein which is loosely bound to the inner membrane. This protein exhibits a PPi ase activity, stimulated by phospholipids, with characteristics very similar to the membrane-bound enzyme. The mitochondrial PPi ase is distinct from the V-PPi ase, because an antibody raised against the 35-kDa protein does not react with tonoplast membranes. The mitochondrial H+ -PPi ase seems to have an F-type structure, similar to the F-ATP synthase and the membrane-bound PPi ases from mammalian and yeast mitochondria. It is suggested that, beside synthesizing PPi , this enzyme may act as a buffer for the electrochemical proton gradient, by hydrolyzing PPi, during conditions of oxygen deprivation. 相似文献
974.
When airways constrict, the surrounding parenchyma undergoesstretch and distortion. Because of the mechanical interdependence between airways and parenchyma, the material properties of the parenchyma are important factors that modulate the degree ofbronchoconstriction. The purpose of this study was to investigate theeffect of changes in transpulmonary pressure (Ptp) and inducedconstriction on parenchymal bulk (k)and shear (µ) moduli. In excised rat lungs, pressure was measured atthe airway opening, and pressure-volume curves were obtained byimposing step decreases in volume with a calibrated syringe from totallung inflation. Calculation was made ofk during small-volume oscillations (1 Hz). Absolute lung volume at 0 cmH2O Ptp was obtained bysaline displacement. To calculate µ, a lung-indentation test wasperformed. The lung surface was deformed with a cylindrical punch(diameter = 0.45 cm) in 0.25-mm increments, and the force required toeffect this displacement was measured by a weight balance. Measurementsof k and µ were obtained at 4 and 10 cmH2O Ptp, and again at 4 cmH2O Ptp, after delivery ofmethacholine aerosol (100 mg/ml) into the trachea. Values ofk and µ in rat lungs were similar tothose reported in other species. In addition, k and µ were dependent on Ptp. Afterinduced constriction, k and µ increased significantly. That k and µ can increase after induced constriction has important implicationsvis a vis the factors modulating airway narrowing. 相似文献
975.
Marco Zancani Carlo Peresson Antonino Biroccio Giorgio Federici Andrea Urbani Irene Murgia Carlo Soave Fulvio Micali Angelo Vianello Francesco Macrì 《European journal of biochemistry》2004,271(18):3657-3664
In this work, evidence for the presence of ferritins in plant mitochondria is supplied. Mitochondria were isolated from etiolated pea stems and Arabidopsis thaliana cell cultures. The proteins were separated by SDS/PAGE. A protein, with an apparent molecular mass of approximately 25-26 kDa (corresponding to that of ferritin), was cross-reacted with an antibody raised against pea seed ferritin. The mitochondrial ferritin from pea stems was also purified by immunoprecipitation. The purified protein was analyzed by MALDI-TOF mass spectrometry and the results of both mass finger print and peptide fragmentation by post source decay assign the polypeptide sequence to the pea ferritin (P < 0.05). The mitochondrial localization of ferritin was also confirmed by immunocytochemistry experiments on isolated mitochondria and cross-sections of pea stem cells. The possible role of ferritin in oxidative stress of plant mitochondria is discussed. 相似文献
976.
Francesco Fontana Ronald M Bruch Fred P Binkowski Massimo Lanfredi Milvia Chicca Nicola Beltrami Leonardo Congiu 《Génome》2004,47(4):742-746
A karyotype analysis using several staining techniques was carried out on the North American lake sturgeon, Acipenser fulvescens. The chromosome number was found to be 2n = 262 +/- 6. A representative karyotype of 264 chromosomes was composed of 134 meta- and submetacentrics, 70 telo- and acrocentrics, and 60 microchromosomes. The constitutive heterochromatin, revealed by C banding, was localized in various positions on several chromosomes, including microchromosomes. The signals of fluorescent in situ hybridization (FISH) with a HindIII satellite DNA probe were visible as centromeric heterochromatin blocks on 48 chromosomes. The telomeric repeat (TTAGGG)n detected by FISH was localized at both ends of all chromosomes and two chromosomes were entirely marked. Fluorescent staining with GC-specific chromomycin A3 showed recognizable fluorescent regions, whereas a more uniform base composition was revealed by the AT-specific 4',6-diamidino-2-phenylindole (DAPI). After silver staining, the active nucleolar organizer regions (NORs) were detected on 12 chromosomes. FISH with the 5S probe showed four signals on four small chromosomes. Our data suggest that A. fulvescens is a tetraploid species. 相似文献
977.
978.
Alberto Ricci Sophie Marchal-Victorion Elena Bronzetti Angelo Parini Francesco Amenta Seyed K Tayebati 《The journal of histochemistry and cytochemistry》2002,50(8):1091-1096
Dopamine D4 receptors mediate inhibition of vasopressin-dependent sodium reabsorption by dopamine in collecting tubules. At present, the distribution of D4 receptors in other renal districts remains an open issue. The renal distribution of D4 receptor was assessed in normally innervated and denervated male Sprague-Dawley rats by quantitative immunohistochemistry using an anti-dopamine D4 receptor rabbit polyclonal antibody. D4 receptor protein immunoreactivity was observed perivascularly in the adventitia and the adventitia-media border. The density of perivascular dopamine D4 receptor was higher in afferent and efferent arterioles than in other segments of the renal vascular tree. Renal denervation abolished perivascular dopamine D4 receptor protein immunoreactivity. In renal tubules, the epithelium of collecting tubules showed the highest dopamine D4 receptor protein immunoreactivity, followed by the epithelium of proximal and distal tubules. No dopamine D4 receptor protein immunoreactivity was observed in the epithelium of the loop of Henle. Denervation did not change dopamine D4 receptor protein immunoreactivity in renal tubules. These results indicate that rat kidney expresses dopamine D4 receptors located both prejunctionally and nonprejunctionally in collecting, proximal, and distal tubules. This suggests that the dopamine D4 receptor may be involved in the control of neurotransmitter release and in renal hemodynamic and tubule function. 相似文献
979.
From the aerial parts of Artemisia alba of Calabrian origin, five oxygenated nerolidol derivatives were isolated, two of them bearing hydroperoxyl groups. Structures were elucidated by spectral data and chemical reactions. Acetylation of the major hydroperoxyl constituent afforded a tris-nor aldehydic derivative as a result of loss of acetone from an unstable intermediate perester. An internally consistent set of 13C NMR assignments for the natural products and some derivatives is presented. 相似文献
980.
Aurelio Mateo-Alonso G M Aminur Rahman Christian Ehli Dirk M Guldi Giulia Fioravanti Massimo Marcaccio Francesco Paolucci Maurizio Prato 《Photochemical & photobiological sciences》2006,5(12):1173-1176
The photophysical and electrochemical properties of a fumaramide rotaxane stoppered with C(60) are reported. The results evidenced the strong binding interactions between the template and the macrocycle, which are also supported by molecular modelling. 相似文献