Search results for "Activity"
showing 10 items of 7178 documents
Novel Terphenyls and 3,5-Diaryl Isoxazole Derivatives Endowed with Growth Supporting and Antiapoptotic Properties
2008
A new study on terphenyl and diaryl-isoxazole and -isoxazoline derivatives, maintaining a common 3-adamantyl-4-hydroxyphenyl moiety, has been conducted to find compounds with growth supporting and antiapoptotic properties. Unexpectedly, diphenyisoxazole derivatives bearing a nitro group replacing the carboxylic function have been found with the highest cell protective activity within the series, in complete and in serum-free conditions. Inhibition of apoptosis induced by daunorubicin has also been observed for the most active compound.
Functional end groups for polymers prepared using ring-opening metathesis polymerization.
2011
The precise placement of functional groups on the chain-ends of macromolecules is a major focus of polymer research. Most common living polymerization techniques offer specific methods of end-functionalization governed by the active propagating species and the kinetics of the polymerization reaction. Ring-opening metathesis polymerization has established itself as one of the most functional-group-tolerant living polymerization techniques known, but this tolerance has limited the number of available functionalization reactions. Metathesis chemists have therefore been required to develop a variety of end-functionalizations, adapting each of them to the reactivity scheme of the particular cata…
Reduction of benzo(a)pyrene mutagenicity by dihydrodiol dehydrogenase
1979
THE enigma of how inert chemicals can exert potent mutagenic, carcinogenic, allergenic and cytotoxic effects has been much debated. It has been learned that such compounds are metabolically converted to chemically reactive species1. In the case of aromatic or olefinic compounds, monooxygenases located in the membranes of the cell can transform these compounds into epoxides2–5 which by virtue of electrophilic reactivity can bind chemically to cellular macromolecules such as DNA, RNA and proteins, thereby disturbing biochemical control mechanisms and leading to the above mentioned toxic effects. The same membranes in which such epoxides are produced possess an enzyme, epoxide hydratase, which…
Molecular and kinetic properties of lactate dehydrogenase in the degenerating peripheral nerve
1966
Abstract Electrophoretic and catalytic studies have been carried out on lactate dehydrogenase of normal and transected sciatic nerves of the rat. Lactate dehydrogenase of the intact nerve exhibits an almost even distribution of activity among its component iso-enzymes. The complete transection of the nerve is responsible for a deep and immediate shift of the enzyme towards the so-called muscle type pattern. Seven days after the nerve section the percentage activity of iso-enzyme 5 is almost three times higher than in the intact nerve. After a short lag period lactate dehydrogenase specific activity (activity/mg protein) undergoes a sharp decrease in transected nerves. The return of the elec…
Quantitative characterization of the global electrophilicity pattern of some reagents involved in 1,3-dipolar cycloaddition reactions
2003
Abstract The global electrophilicity power, ω, of a series of dipoles and dipolarophiles commonly used in 1,3-dipolar cycloadditions may be conveniently classified within a unique relative scale. The effects of chemical substitution on the electrophilicity of molecules have been evaluated using a representative set of electron-withdrawing and electron-releasing groups for a series of dipoles including nitrone, nitrile oxide and azide derivatives. The absolute scale of electrophilicity is used to rationalize the chemical reactivity of these species as compared to the static reactivity pattern of the reagents involved in the Diels–Alder reactions.
Reactivity of the carbon-carbon double bond towards nucleophilic additions. A dft analysis
2004
Abstract The global and local electrophilicity indexes have been used to characterize the reactivity pattern of the CC double bond towards nucleophilic addition reactions. A wide family of molecules including ketones, esters, anhydrides, nitriles and nitrocompounds containing appropriate substitution on the CC double bond have been classified within an unique scale of reactivity. The predictive capability of the theoretical model is tested against a series of benzylidenemalononitriles and substituted α-nitrostilbenes.
Reactivity of the di-μ-hydroxo-complexes [{Pd(NN)}2(μ-OH)2][ClO4]2 (NN=bis(pyrazol-1-yl)alkanes) towards protic electrophiles. Hydration of coordin…
2000
Abstract The hydroxo-complexes [{Pd(μ-OH)(NN)}2][ClO4]2 (NN=bpzm:bis(pyrazol-1-yl) methane: a-compounds, bpzm*:bis(3,5-dimethylpyrazol-1-yl)methane; b-compounds) react with a wide variety of weak protic electrophiles H(LL) in a 1:2 molar ratio to give the mononuclear cationic palladium(II) derivatives of general formula [Pd(LL)(NN)][ClO4] [LL=2-pyridine-methoxo (OCH2-py) (1a,b); picolinate (pic) (2a,b); 8-hydroxiquinolinate (oxin) (3a,b)] or the dinuclear complexes [{Pd(NN)}2(μ-ox)][ClO4]2 [ox=oxalate: (4a,b)] and [{Pd(μ-LL)(NN)}2][ClO4]2 [LL=pyrazolate (pz) (5a,b); p-thiocresolate (SC6H4Me-p) (6a,b); triazolate (tz) (7b); thiophenolate (SPh) (8b)] when reacting with oxalic acid, azole…
Biological effects of short-chain fatty acids in nonruminant mammals.
1993
propionate, volatile fatty acids (VFAs), cholesterol, cell prolifera tion, human gastric lipase
Staphylococcal NreB: an O2-sensing histidine protein kinase with an O2-labile iron-sulphur cluster of the FNR type
2004
Summary The nreABC ( n itrogen re gulation) operon encodes a new staphylococcal two-component regulatory sys- tem that controls dissimilatory nitrate/nitrite reduc- tion in response to oxygen. Unlike other two- component sensors NreB is a cytosolic protein with four N-terminal cysteine residues. It was shown that both the NreB-cysteine cluster and Fe ions are required for function. Isolated NreB was converted to the active form by incubation with cysteine desul- phurase, ferrous ions and cysteine. This activation is typical for FeS-containing proteins and was reversed by oxygen. During reconstitution an absorption band at 420 nm and a yellow-brownish colour (typical for an FNR-type iron-sul…
Alkylation of lithium dienediolates of butenoic acids. Regioselectivity effects of structure and leaving group of the alkylating agent
1998
Abstract Regioselectivity of alkylation of but-2-enoic acids 1 and 2 by alkyl halides strongly depends on the reactivity of the electrophile. High α selectivity results for saturated alkyl halides, whereas poor α-selectivity is obtained for highly reactive allyl and benzyl halides. For reactive alkylating halides selectivity is partly governed by the ion pairing aggregates of the dienediolates. Lithium bromide and the carboxylate generated in the ongoing reaction cause opposite effects on regioselectivity.