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901.
902.
Lernanthropus huamani n. sp. (Copepoda: Lernanthropidae), a parasite of the Peruvian sciaenid fish Menticirrhus ophicephalus (Jenyns), is described and illustrated. The new species differs from all other species of Lernanthropus by a combination of characters, including the dorsal plate, legs and other appendages. L. guacoldae Villalba & Fernández, 1984 is considered a synonym of L. pacificus Oliva & Duran, 1982. 相似文献
903.
A new spectrophotometric assay for dopachrome tautomerase 总被引:2,自引:0,他引:2
P Aroca F Solano J C García-Borrón J A Lozano 《Journal of biochemical and biophysical methods》1990,21(1):35-46
The existence of a new enzyme involved in mammalian melanogenesis has been recently reported. The names dopachrome oxidoreductase and dopachrome tautomerase have been proposed for the enzyme. So far, this enzyme has been assayed at 475 nm on the basis of its ability to catalyze dopachrome decoloration. This method presents two major problems, derived from the instability of the substrate (dopachrome): (1) dopachrome must be prepared immediately before use, and (2) the rate of dopachrome decoloration in the absence of the enzyme is not negligible, and, furthermore, is enhanced by non-enzymatic agents. In order to overcome these problems, we present a new procedure that combines: (1) a quantitative, fast and easy way to prepare dopachrome from L-dopa by sodium periodate oxidation; (2) a spectrophotometric method in the UV region, at 308 nm, based on following the absorbance increase due to the enzyme-specific tautomerization of dopachrome to 5,6-dihydroxyindole-2-carboxylic acid as opposed to the absorbance decrease due to the spontaneous decarboxylative transformation of dopachrome into 5,6-dihydroxyindole. The advantages of these methods as compared to the previously used procedures are discussed. 相似文献
904.
María Teresa Herrera Margarita Cacho M. Purificación Corchete Jorge Fernandez-Tarrago 《Plant Cell, Tissue and Organ Culture》1990,22(3):179-182
Shoot tips from seedlings of Digitalis thapsi L. were cultured on Murashige and Skoog's medium and the effect of various auxins (2,4-D, NAA and IAA) were analyzed alone or in combination with cytokinis (BA and kinetin). Shoot multiplication and direct rooting of the new shoots were obtained after four weeks of culture in MS medium without hormones, but callus formation and the appearance of abnormal phenotypes were frequent. The addition of auxins to the cultures prevented the formation of callus but not the appearance of variant phenotypes. Both drawbacks could be avoided by combination of NAA or IAA with BA or kinetin. The best results for shoot multiplication and direct rooting were obtained with 0.5 mg l-1 NAA and 0.1 or 0.5 mg l-1 kinetin.Abbreviations BA
6-benciladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- IAA
indole-3-acetic acid
- Kin
kinetin
- NAA
naphtalene acetic acid
- MS
Murashige and Skoog 相似文献
905.
The fusarium mycotoxin zearalenone was transformed in cell suspension cultures of Zea mays giving α- and β-zearalenol and the β-D-glu cos ides of zearalenone and α- and β-zearalenol. The structure of zearalenone-4-β-D-glucopyranoside was determined by liquid — chromatography-mass spectrometry and specific hydrolysis with β-glucosidase. α- and β-zearalenol and their glucosides were identified by co chromatography using tic and HPLC and glucosidase — treatment Up to 50% of the mycotoxin added was bound to a non extractable or “bound” residue fraction. After treating this residue by a sequential cell wall fractionation procedure, zearalenone was found to be bound mainly to starch, hemicellulose, and lignin fractions. 相似文献
906.
Francisco Guillén Angel T. Martinez Maria Jesús Martínez 《Applied microbiology and biotechnology》1990,32(4):465-469
Summary Production of extracellular hydrogen peroxide by fungal oxidases is been investigated as a requirement for lignin degradation. Aryl-alcohol oxidase activity is described in extracellular liquid and mycelium ofPleurotus eryngii and studied under non-limiting nitrogen conditions. This aryl-alcohol oxidase catalyses conversion of primary aromatic alcohols to the corresponding aldehydes and H2O2, showing no activity with aliphatic and secondary aromatic alcohols. The enzyme is stable at pH 4.0–9.0, has maximal activity at 45°–50°C and pH 6.0–6.5, is inhibited by Ag+, Pb2+ and NaN3, and has aK
m
of 1.2 mM using veratryl alcohol as substrate. A single protein band with aryl-alcohol oxidase activity was found in zymograms of extracellular and intracellular crude enzyme preparations fromP. eryngii. 相似文献
907.
James P. Ferris Kamaluddin Gözen Ertem 《Origins of life and evolution of the biosphere》1990,20(3-4):279-291
2-d-5-GMP and 2-d-5-AMP bind 2 times more strongly to montmorillonite 22A than do 2-d-5-CMP and 5-TMP. The dinucleotide d(pG)2 forms in 9.2% yield and the cyclic dinucleotide c(dpG)2 in 5.4% yield in the reaction of 2-d-5-GMP with EDAC in the presence of montmorillonite 22A. The yield of d(pC)2 (2.0%) is significantly lower but comparable to that obtained from 5-TMP. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5-ImdpA on montmorillonite 22A. The cyclic nucleotide (3,5-cdAMP) was obtained in 14% yield from 3-ImdpA. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na+-montmorillonite used as catalyst. Evidence is presented which shows that the acidity of the Na+-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation. 相似文献
908.
Summary
Candida tropicalis S001 was grown on the lipid fraction of a protein-containing waste-water in order to (i) remove fat from the water, and (ii) produre yeast biomass for feed. The yeast cells were separated from the waste-water by sedimentation. Defatted waste-water was used for methane production and gave a yield of a 0.3 m3 methane/kg reduced chemical oxygen demand. The maximum specific growth rate (µmax) of C. tropicalis growing on waste-water fat at pH 4.0 was 0.35 h–1; the fat content was decreased from 8 g/l to about 0.1 g/l within 24 h. In continous culture a corresponding reduction was maintained at dilution rates up to 0.36 h–1. The effect on growth of pH, temperature and CO2 concentration was studied with triolein as the major carbon source. The µmax was nearly constant (0.16 h–1) in the pH and temperature range of 3.2–4.0 and 30°–38° C, respectively; 10% CO2 was optimal for growth. Growth on triolein resulted in a biomass yield of 0.70 g dry weight/g fat.
Offprint requests to: S. Rydin 相似文献
909.
A Go-like protein in Drosophila melanogaster and its expression in memory mutants. 总被引:2,自引:2,他引:0 下载免费PDF全文
A Guilln J M Jallon J A Fehrentz C Pantaloni J Bockaert V Homburger 《The EMBO journal》1990,9(5):1449-1455
G proteins couple receptors for extracellular signals to several intracellular effector systems and play a key role in signalling transduction mechanisms. In particulate preparations of Drosophila melanogaster heads, only one substrate for pertussis toxin at 39-40 kd was detected. This substrate, which showed only one isoform when analysed by isoelectric focusing, was recognized by immunoblotting and immunoprecipitation techniques using a polyclonal antibody against the alpha subunit of the Go protein purified from bovine brain and can be thus considered as a Go-like protein. Antibodies obtained against a carboxy-terminal sequence of the alpha subunit of Go (but not of Gi1 or Gi2) and against an internal sequence shared by all the alpha subunits, were also able to cross-react with the alpha subunit of this protein in insects. We have also studied the Go-like protein in several D.melanogaster mutants, primarily in memory and learning mutants. In these mutants there was a sex-dependent enhancement in pertussis toxin-catalysed ADP-ribosylation with respect to the wild-type. This increase could be attributed in part to an increase in the alpha subunit of the Go-like protein, as revealed by immunoblotting with anti-Go alpha polyclonal antibody. This report constitutes the first evidence for the participation of a Go protein in learning and memory. 相似文献
910.
Chemical mechanism of lysophosphatidylcholine: lysophosphatidylcholine acyltransferase from rabbit lung. pH-dependence of kinetic parameters. 下载免费PDF全文
Lysophosphatidylcholine: lysophosphatidylcholine acyltransferase is an enzyme that catalyses two reactions: hydrolysis of lysophosphatidylcholine and transacylation between two molecules of lysophosphatidylcholine to give disaturated phosphatidylcholine. Following the kinetic model previously proposed for this enzyme [Martín, Pérez-Gil, Acebal & Arche (1990) Biochem. J. 266, 47-53], the values of essential pK values in free enzyme and substrate-enzyme complexes have now been determined. The chemical mechanism of catalysis was dependent on the deprotonation of a histidine residue with pK about 5.7. This result was supported by the perturbation of pK values by addition of organic solvent. Very high and exothermic enthalpy of ionization was measured, indicating that a conformational re-arrangement in the enzyme accompanies the ionization of the essential histidine residue. These results, as well as the results from previous studies, enabled the proposal of a chemical mechanism for the enzymic reactions catalysed by lysophosphatidylcholine: lysophosphatidylcholine acyltransferase from rabbit lung. 相似文献