1,721,130 research outputs found
KINETICS AND STEREOCHEMISTRY OF THE MICROSOMAL EPOXIDE HYDROLASE-CATALYZED HYDROLYSIS OF CIS-STILBENE OXIDES
No full textThe microsomal epoxide hydrolase (mEH)-catalyzed hydrolysis of cis-4,4'-dimethylstilbene oxide (1a), cis-4,4'-diethylstilbene oxide (1b), cis-4,4'-diisopropylstilbene oxide (Ic), and cis-4,4'-dichlorostilbene oxide (1d) have been investigated using rabbit liver microsomal preparations. The kinetic parameters, K-m and V-max, and the absolute stereochemistry of the reactions have been determined and compared with those of cis-stilbene oxide (1e). All epoxides 1a-d are hydrolyzed by mEH with high product enantioselectivity to give (R,R)-(+)-diols with ee greater than or equal to 90%. The presence of the substituents on the phenyl rings markedly reduces the rates of mEH catalyzed hydrolysis with respect to cis-stilbene oxide, by increasing K-m and reducing V-max in the cases of 1a, 1b, and 1d, or reducing only the V-max in the case of 1c. The very low V-max, together with a persistent ability to fit into the mEH active site, make all these epoxides, and particularly 1c, inhibitors of cis-stilbene oxide hydrolysis. The kinetic and stereochemical results are interpreted on the basis of the proposed topology of the mEH active site. (C) 1994 Wiley-Liss, Inc
L'autonomia finanziaria regionale nella Costituzione italiana: il caso della fiscalità di vantaggio.
No full textIl saggio affronta il tema dei poteri regionali in materia di fiscalità di vantaggio con particolare riguardo alle Autonomie speciali ricercandone, da un lato, la connessione con la normativa comunitaria sugli aiuti di Stato e, dall'altro, la possibile individuazione di un modus operandi che consenta loro di adottare "tributi propri in senso stretto" nel rispetto dell'ordinamento costituzionale e sovranazionale
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Enantioconvergent transformation of racemic cis-dialkyl substituted epoxides to (R,R) threo diols by microsomal epoxide hydrolase catalysed hydrolysis
No full textBoth enantiomers of (+/-)-9,10-epoxystearic acid (1b), cis-(+/-)-5,6-epoxyhexadecane (1c) and cis-(+/-)-11,12-epoxyhexadecan-1-ol (1d) as well as the meso cis-9,10-epoxyoctadecane (1a) undergo microsomal epoxide hydrolase catalyzed hydration at the (S) carbon to give the corresponding (R,R) threo diols in a >90 e.e. Copyright (C) 1996 Elsevier Science Lt
System of selfgravitating semidegenerate fermions with a cutoff of energy and angular momentum in their distribution function
No full textWe study the gravitational equilibrium of static, spherically symmetric, Newtonian systems consisting of a collisionless semidegenerate Fermi gas. A cutoff in the phase space distribution function of the particles is introduced in order to avoid the problems arising from the infinite radius of semidegenerate configurations when the usual Fermi-Dirac function is used. We consider, here, the more general case of a cutoff in energy and angular momentum, the latter giving an anisotropy in the velocity space. The treatment is applied to model massive galactic halos. Limits on the mass of the "inos" composing the halos are derived both from phase space constraints and from general features of the observed rotation curves in spiral galaxies
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