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91.
Francesca Gherardi Federica Tarducci Marco Vannini 《Ethology : formerly Zeitschrift fur Tierpsychologie》1988,77(4):300-316
Locomotor activity in a field population of the freshwater crab, Potamon fluviatile, was studied during the breeding season by means of radio-telemetry and by direct counts of active animals along a transect of the stream. The basic pattern of crabs' locomotor activity can be described as a sequence of short distance movements around the shelters (foraging movements), followed by rarer long distance displacements (wandering movements). Whilst direct counting showed that the crabs exhibit a broadly nocturnal rhythm in foraging movements, no daily periodicity in wandering activity was revealed by telemetry. There is sexual difference in these latter excursions: females move farther along the stream and into the surrounding terrestrial habitat than do males. This behaviour is in contrast to observations made during the non-breeding season and is probably related to the stage of female reproduction. 相似文献
92.
Marco Rito-Palomares Andrew Lyddiatt 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,680(1-2):81-89
A practical study is presented of the influence of cell debris and polymer recycling upon the operation of two-stage acqueous two-phase systems (ATPS) for the recovery of yeast bulk protein, pyruvate kinase and fumarase. Brewers' yeast was disrupted using one of two types of high-pressure homogenisers or a bead mill. The different cell debris suspensions were partitioned in a single PEG-phosphate ATPS extraction and the efficiency of solid-liquid separation was examined. A continuously operated two-stage ATPS process, using spray columns, is presented and practical problems of polymer recycling are discussed. Conclusions are drawn concerning the generic implementation and operational stability of ATPS in practical protein recoveries. 相似文献
93.
Ersilia Cassano Marco Macchia Mahmud Hamdan Paolo Rovero 《Letters in Peptide Science》1996,3(3):117-120
Summary We describe a new solid-phase strategy for the selective reduction of the C=N bond in peptide oximes using a trialkylsilane in trifluoroacetic acid. The reduction is performed directly on the resin-bound peptide, with concomitant cleavage of the peptide from the resin and deblocking of protected side chains. 相似文献
94.
Identification of a locus involved in meningococcal lipopolysaccharide biosynthesis by deletion mutagenesis 总被引:4,自引:0,他引:4
Peter van der Ley Marco Kramer Liana Steeghs Betsy Kuipers Svein R. Andersen Michael P. Jennings E. Richard Moxon & Jan T. Poolman 《Molecular microbiology》1996,19(5):1117-1125
A novel method for insertion/deletion mutagenesis in meningococci was devised. This consisted of ligating a digest of total chromosomal DNA to a 1.1 kb restriction fragment containing an erythromycin-resistance marker ( ermC ), and subsequent transformation of the ligation mixture into the homologous meningococcal strain H44/76. Southern blotting of a number of the resulting erythromycin-resistant transformants demonstrated that all carried the ermC gene inserted at different positions in the chromosome. Mutants with a specific phenotype were identified by screening with the anti-lipopolysaccharide (LPS) monoclonal antibody MN4A8B2, which is specific for immunotype L3. In this way, two independent L3-negative mutant strains were isolated. In transformation experiments with chromosomal DNA from these mutants, erythromycin-resistance and lack of MN4A8B2 reactivity were always linked, showing that the insertion/deletion was in a locus involved in LPS biosynthesis. On SDS–PAGE, the mutant LPS displayed an electrophoretic mobility intermediate between that produced by the previously isolated galE and rfaF mutant strains. Chemical analysis of the mutant LPS revealed that the structure was probably lipid A–(KDO)2 –(Hep)2 . Chromosomal DNA flanking the ermC insertion in these two mutant strains was cloned, and used as probe for the isolation of the corresponding region of the wild-type strain. From hybridization and polymerase chain reaction (PCR) analysis, it could be concluded that both mutations map to the same locus. The affected gene probably encodes the glycosyltransferase necessary for adding N -acetylglucosamine to heptose. 相似文献
95.
Vittorio Moretto Fernando Formaggio Marco Crisma Gian Maria Bonora Claudio Toniolo Ettore Benedetti Antonello Santini Michele Saviano Benedetto Di Blasio Carlo Pedone 《Journal of peptide science》1996,2(1):14-27
A complete series of terminally blocked, monodispersed homo-oligopeptides (to the pentamer level) from the sterically demanding, medium-ring alicyclic Cα,α-disubstituted glycine 1-aminocyclooctane-1-carb oxylic acid (Ac8c), and two Ala/Ac8c tripeptides, were synthesized by solution methods and fully characterized. The preferred conformation of all the oligopeptides was determined in deuterochloroform solution by IR absorption and 1H-NMR. The molecular structures of the amino acid derivative Z-Ac8c-OH, the dipeptide pBrBz- (Ac8c)2-OH and the tripeptide pBrBz-(Ac8c)3-OtBu were assessed in the crystal state by X-ray diffraction. Conformational energy computations were performed on the monopeptide Ac-Ac8c-NHMe. Taken together, the results obtained strongly support the view that the Ac8c residue is an effective β-turn and helix former. A comparison is also made with the conformational preferences of α-aminoisobutyric acid, the prototype of Cα, α-disubstituted glycines, and of the other members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3, 5–7) investigated so far. The implications for the use of the Ac8c residue in peptide conformational design are considered. 相似文献
96.
Pierluigi Gariboldi Francesca Pelizzoni Marco Tat Luisella Verotta Nadia El-Sebakhy Aya M. Asaad Rokia M. Abdallah Soad M. Toaima 《Phytochemistry》1995,40(6):1755-1760
Three new cycloartane glycosides, trigonoside I, II and III, and the known astragalosides I and II were isolated from the roots of Astragalus trigonus. The structures of the new glycosides were totally elucidated by high field (600 MHz) NMR analyses as cycloastragenol-6-O-β-xylopyranoside, cycloastragenol-3-O-[-l-arabinopyranosyl(1 → 2)-β-d-xylopyranosyl]-6-O-β- d-xylopyranoside and cycloastragenol-3-O-[-l-arabinopyranosyl(1 → 2)-β-d-(3-O-acetyl)-xylopyranosyl]-6-O-β-d-xylopyranoside. 相似文献
97.
Clare Gough Pascale Hemon Maurice Tronchet Christophe Lacomme Yves Marco Dominique Roby 《Molecular & general genetics : MGG》1995,247(3):323-337
A family of genes, the so-called msr genes (multiple stimulus response), has recently been identified on the basis of sequence homology in various plant species. Members of this gene family are thought to be regulated by a number of environmental or developmental stimuli, although it is not known whether any one member responds more specifically to one stimulus, or whether each gene member responds to various environmental stimuli. In this report, we address this question by studying the tobacco msr gene str246C. Using transgenic tobacco plants containing 2.1 kb of 5 flanking DNA sequence from the str246C gene fused to the -glucuronidase (GUS) coding region, the complex expression pattern of the str246C promoter has been characterized. Expression of the str246C promoter is strongly and rapidly induced by bacterial, fungal and viral infection and this induction is systemic. Elicitor preparations from phytopathogenic bacteria and fungi activate the str246C promoter to high levels, as do wounding, the application of auxin, auxin and cytokinin, salicylic acid or copper sulfate, indicating the absence of gene specialization within the msr gene family, at least for str246C. In addition, GUS activity was visualized. histochemically in root meristematic tissues of tobacco seedlings and is restricted to roots and sepals of mature plants. Finally, analysis of a series of 5 deletions of the str246C promoter-GUS gene fusion in transgenic tobacco plants confirms the involvement of multiple regulatory elements. A region of 83 by was found to be necessary for induction of promoter activity in response to Pseudomonas solanacearum, while auxin inducibility and root expression are apparently not controlled by this element, since its removal does not abolish either response. An element of the promoter with a negative effect on promoter activation by P. solanacearum was also identified.Joint first authors 相似文献
98.
99.
Gianantonio Battistuzzi Marco Borsari Lodovica Loschi M. Sola 《Journal of biological inorganic chemistry》1997,2(3):350-359
The reduction potential of the basic blue-copper protein from cucumber peels (CBP) was determined through voltammetric techniques
in different conditions of temperature, pH and ionic composition of the medium. The most notable properties of CBP include
a positive entropy change upon reduction, a low-pH protonation and detachment of a metal-binding histidine in the reduced
protein, and specific binding interactions with a number of anions present in common laboratory buffers, which influence to
some extent the redox thermodynamics. The enthalpy and entropy changes accompanying reduction of the Cu(II) center were compared
with those for other blue-copper proteins and correlated with spectroscopic data, structural properties and theoretical calculations.
This allows some general considerations to be offered regarding the determinants of the reduction potential in this protein
class. It emerges, in line with previous studies of the electronic structure of blue-copper sites, that the enthalpic contribution
to the reduction potential is mainly modulated by the metal-binding interactions in the trigonal N2S ligand set, and particularly by the Cu-cysteinate bond, while the entropy term is mainly affected by solvation properties
and possibly by the weak axial bond to copper. The role of solvent exposure of the metal site in the active-site protonations
in reduced blue-copper proteins is discussed. Finally, it is shown that the Nernst-Debye-Huckel model qualitatively accounts
for the ionic strength dependence of the reduction potential.
Received: 20 December 1996 / Accepted: 26 March 1997 相似文献
100.
The unprecedented Friedländer reaction of densely functionalized 2-amino-3-cyano-4H-pyrans (1) with cyclohexanone has afforded in one step and good yield 5-amino-4-aryl-3-ethoxycarbonyl-2-methyl-6,7,8,9-tetrahydro-4H-pyran[2,3-b]quinolines (2), novel amino-substituted fused pyran derivatives. These compounds are new tacrine analogues. 相似文献