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11.
Pecchia P Cammareri M Malafronte N Consiglio MF Gualtieri MJ Conicella C 《Natural product communications》2011,6(11):1665-1669
Several different classes of secondary metabolites, including flavonoids, triterpenoid saponins and quinic acid derivatives, are found in Aster spp. (Fam. Asteraceae). Several Aster compounds revealed biological as well as pharmacological activities. In this work, a phytochemical investigation of A. caucasicus evidenced the presence of quinic acid derivatives, as well as the absence of triterpene saponins. To combine in one species the production of different phytochemicals, including triterpenes, an Agrobacterium-mediated transformation of A. caucasicus was set up to introduce A. sedifolius beta-amyrin synthase (AsOXA1)-encoding gene under the control of the constitutive promoter CaMV35S. The quali-quantitative analysis of transgenic calli with ectopic expression of AsOXA1 showed, in one sample, a negligible amount of triterpene saponins combined with higher amount of quinic acid derivatives as compared with the wild type callus. 相似文献
12.
Mario Giannella Fulvio Gualtieri Maria Luisa Stein 《Journal of heterocyclic chemistry》1971,8(3):397-403
The Posner reaction between coumarin and hydroxylamine was studied and extended to several substituted coumarins. Isolation of some significant reaction intermediates permitted rationalization of a possible reaction pathway. 相似文献
13.
In models with extra dimensions, a black hole evaporates both in the bulk and on the visible brane, where standard model fields live. The exact emissivities of each particle species are needed to determine how the black hole decay proceeds. We compute and discuss the absorption cross sections, the relative emissivities, and the total power output of all known fields in the evaporation phase. Graviton emissivity is highly enhanced as the spacetime dimensionality increases. Therefore, a black hole loses a significant fraction of its mass in the bulk. This result has important consequences for the phenomenology of black holes in models with extra dimensions and black hole detection in particle colliders. 相似文献
14.
Barsanti L Coltelli P Evangelista V Passarelli V Frassanito AM Vesentini N Santoro F Gualtieri P 《Photochemistry and photobiology》2009,85(1):304-312
Euglena gracilis possesses a simple but sophisticated light detecting system, consisting of an eyespot formed by carotenoids globules and a photoreceptor. The photoreceptor of Euglena is characterized by optical bistability, with two stable states. In order to provide important and discriminating information on the series of structural changes that Euglena photoreceptive protein(s) undergoes inside the photoreceptor in response to light, we measured the in vivo absorption spectra of the two stable states A and B of photoreceptor photocycle. Data were collected using two different devices, i.e. a microspectrophotometer and a digital microscope. Our results show that the photocycle and the absorption spectra of the photoreceptor possess strong spectroscopic similarities with a rhodopsin-like protein. Moreover, the analysis of the absorption spectra of the two stable states of the photoreceptor and the absorption spectrum of the eyespot suggests an intriguing hypothesis for the orientation of microalgae toward light. 相似文献
15.
Evangelista V Frassanito AM Passarelli V Barsanti L Gualtieri P 《Photochemistry and photobiology》2006,82(4):1039-1046
We performed microspectroscopic evaluation of the pigment composition of the photosynthetic compartments of algae belonging to different taxonomic divisions and higher plants. The feasibility of microspectroscopy for discriminating among species and/or phylogenetic groups was tested on laboratory cultures. Gaussian bands decompositions and a fitting algorithm, together with fourth-derivative transformation of absorbance spectra, provided a reliable discrimination among chlorophylls a, b and c, phycobiliproteins and carotenoids. Comparative analysis of absorption spectra highlighted the evolutionary grouping of the algae into three main lineages in accordance with the most recent endosymbiotic theories. 相似文献
16.
S. Colacicchi V. Carnicelli G. Gualtieri A. Di Giulio 《Research on Chemical Intermediates》2000,26(9):885-896
EPR and UV spectroscopy were used to investigate the efficiency of ascorbic acid in reducing Fremy’s salt. Our data indicates
that the first proton electron transfer from ascorbate occurs within the mixing time. Even after the disappearance of the
UV signal of the ascorbate, EPR measurements showed that the reaction goes forward, indicating a biphasic redox process. The
slower time-course of this second phase was related to the initial concentrations of the reductant. Experiments performed
at four different pH values demonstrated that the reduction was a function of the bulk solution pH. At the lower pH, after
a fast initial reduction, the Fremy’s salt EPR signal remained constant, while at physiological or higher pH a further reduction
was found.
The reaction rates demonstrate that the reducing power of ascorbic acid towards Fremy’s salt strongly depends on its dissociation
state. 相似文献
17.
Maria Novella Romanelli Silvia Dei Serena Scapecchi Elisabetta Teodori Fulvio Gualtieri Roberta Budriesi Raimund Mannhold 《Journal of computer-aided molecular design》1994,8(2):123-134
Summary In this work the rigid-analogue approach has been used to obtain information on the active conformation(s) of the calcium antagonist verapamil. A series of semi-rigid analogues of verapamil were synthesized and their biological activities evaluated on guinea-pig heart and aorta. These molecules were analysed by means of molecular modelling techniques.On the basis of the pharmacological profile and conformational analysis of these compounds, two different models for negative inotropic and negative chronotropic activity are proposed. The two actions seem to be due to conformations of the molecules which differ in the orientation of their phenylethylamino groups. 相似文献
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20.
Giampiero Chiaselotti Maria Italia Gualtieri Paolamaria Pietramala 《Journal of Mathematical Modelling and Algorithms》2010,9(1):39-51
A new n log n algorithm for the scheduling problem of n independent jobs on m identical parallel machines with minimum makespan objective is proposed and its worst-case performance ratio is estimated.
The algorithm iteratively combines partial solutions that are obtained by partitioning the set of jobs into suitable families
of subsets. The computational behavior on three families of instances taken from the literature provided interesting results. 相似文献