Paramagnetic Resonance Study of Liquids during Photolysis. II. Acetone and Solutions Containing Acetone

Zeldes, Henry; Livingston, Ralph

doi:10.1063/1.1727877

Cited by 100 publications

(25 citation statements)

References 23 publications

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“…It has an isotropic muon hyperfine coupling constant (Ap) of 26.1 MHz in neat acetone. This is 9 times larger than that of the analogous H-atom adduct (A,,), even after compensation for the 3.18-fold higher nuclear moment of p+ compared to p+ [8]. This is by far the largest hyperfinecoupling isotope effect yet encountered.…”

Section: Introductionmentioning

confidence: 87%

Micelle-induced change of mechanism in the reaction of muonium with acetone

Stadlbauer¹,

Venkateswaran²,

Gillis³

et al. 1996

Can. J. Chem.

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Muonium atoms add to the 0 atom of the carbonyl group of acetone to give the muonated free radical (CH~)~C-O-MU when the reaction takes place in water or hydrocarbons, but not when the acetone is localized in micelles. Micelles have no effect on the formation of muonated cyclohexadienyl radicals when muonium reacts with benzene under similar conditions. The addition reaction with acetone appears to have been subsumed by a faster alternative reaction in the micellar environment. Evidence is presented for this interpretation rather than for an inhibition of the radical or for a shift in the muon level-crossing resonance spectrum with hydrogen (muonium) bonding, though major shifts are seen for the spectrum of this radical in pure solvents of widely different dielectric constant. It is suggested that muonium's "abstraction" reaction takes over in micelles because significant micelle-induced enhancement effects were previously observed in that type of reaction. The data are consistent with a rate constant for the abstraction reaction of muonium with acetone in micelles of >6 x lo8 M-' SKI.Key words: muonium, kinetic isotope effects, micelle enhancement, HMu-addition, H M u abstraction.RCsumC : Lorsqu'on opkre en solution dans I'eau ou dans les hydrocarbures, les atomes de muonium s'ajoutent h I'atome d'oxygkne du groupe carbonyle de l'acitone pour conduire h un radical muone (CH~)~C-O-MU; ce n'est toutefois pas le cas lorsque l'acitone est localisie dans des micelles. Les micelles n'ont aucun effet sur la formation de radicaux cyclohexadiinyles muonts lorsqu'on fait riagir des atomes de muonium avec le benzkne, dans des conditions semblables. I1 semble que, dans un environnement micellaire, la riaction d'addition sur l'acitone est dipassi par une autre riaction plus rapide. On prisente des rLsultats confortant cette interpretation plut6t que celle faisant appel h une inhibition du radical ou h un diplacement du spectre de risonance de croisement au niveau du muon avec une liaison hydrogkne (muonium); toutefois, on observe des diplacements pour les spectres de ce radical dans des solvants purs de constantes diilectriques fort diffirentes. On suggkre que la riaction d'<(enlkvementn des muonium se produit dans des micelles en raison des effets de rehaussement induit par les micelles qui ont it6 observis antirieurement dans ce type de riaction. Les donnies sont en accord avec une constante de vitesse, pour la riaction d'enlkvement du muonium avec l'acitone dans les micelles, qui serait supirieure h 6 x loX M-' s-I.

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Section: Introductionmentioning

confidence: 87%

Micelle-induced change of mechanism in the reaction of muonium with acetone

Stadlbauer¹,

Venkateswaran²,

Gillis³

et al. 1996

Can. J. Chem.

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“…CH3C0 radicals are formed from 2,3-butanedione both in the ultraviolet and the visible region, suggesting that CH3CO may be important in the inactivation of lactoperoxidase. Acetone, which inactivated the enzyme at 254 nm, also gives rise to several types of radicals at this wavelength [41]. Radicals like HCO may not be important, however, since glyoxal was unable to inactivate lactoperoxidase at 254 nm, although at this wavelength glyoxal forms particularly HCO radicals…”

Section: Discussionmentioning

confidence: 99%

Photochemical Inactivation of Lactoperoxidase Sensitized by Carbonyl Compounds

Mäkinen¹,

Mäkinen²

1982

European Journal of Biochemistry

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1. 2,3-Butanedione was found to be a poor noncompetitive inhibitor (Ki z 0.1 M) of bovine milk lactoperoxidase. Irradiation of an incubation mixture of these two substances in the visible region led, however, to an irreversible loss of enzyme activity. The inactivation rates were dependent on light intensity, light wavelength and sensitizer concentration. Maximal rate of inactivation occurred at 400 -420 nm. Other dicarbonyl compounds which caused a similar photodestruction of lactoperoxidase in the visible region were 2,3-pentanedione and 1 -phenyl-I ,2-propanedione, the following compounds being without effect : phenylglyoxal, methylglyoxal, glyoxal, 1,2-cyclohexanedione and acetone. Of the latter, however, 1,2-cyclohexanedione, phenylglyoxal, methylglyoxal and acetone inactivated lactoperoxidase at 254 nm.2. The butanedione-sensitized photochemical inactivation of lactoperoxidase was preventcd by the presence of free radical scavengers and singlet oxygen quenchers, the best protectors being the histidine derivatives ~-3-methylhistidine, L-I-methylhistidine and i.-thiol-2-histidine, which displayed dual quenching ability. No photochemical inactivation of lactoperoxidase occurred in anoxic media even in the presence of high butanedione concentration and strong illumination.3. The butanedione-sensitized photochemical inactivation of lactoperoxidase was accompanied by extensive changes in the ultraviolet absorption spectra of the enzyme. Simultaneously, a dramatic loss in tryptophan fluorescence occurred. All spectral and fluorescence changes were prevented by the above protectors. The sensitized enzyme inactivation was shown to be an all-or-none type of reaction ; no partially inactivatcd enzymes existed.4. Amino acid analysis of native and butanedione light-treated lactoperoxidase showed that the treated enzyme contained considerably less of the following amino acids than the native enzyme : methionine, arginine, tyrosine, aspartic acid, serine, glutamic acid. Histidine residues were probably attacked also. Inhibition and modification studies showed that the activity of the enzyme was not based on arginyl and tryptophyl residues.5. These results suggest that 2,3-butanedione, 1,2-cyclohexanedione, phenylglyoxal and related dicarbonyl compounds, which have previously been used as relatively specific probes for the active arginyl residues of enzymes, cause under suitable modification conditions extensive changes in the structure of an enzyme by affecting a multitude of amino acid residues. These compounds can totally inactivate an enzyme regardless of the essentiality or inessentiality of arginyl residues for enzyme activity. The present results warn against drawing conclusions from modification studies with dicarbonyl Compounds unless the irradiation conditions are carefully considered.2,3-Butanedione has in numerous studies been reported to demonstrate high selectively toward active arginyl residues of enzymes [l -141. A typical case is the modification of an active arginyl residue of carboxypeptidase A with thi...

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“…Thus, the possibility of an appreciable difference in the magnetic properties of the radicals .CH(NH,)COO-and .CH(NH,)COOH cannot be ruled out, especially as the alternative protonation 'This inequality, first observed in liquid acetone solution at -49.5 "C by Zeldes and Livingston (29), has now been discerned with the use of the substrate acetone and the aqueous titanous chloride -hydrogen peroxide radical-generating system at 25 "G (P. Smith and D. J.…”

Section: The Structure Of Radicals Formed Frommentioning

confidence: 99%

“…There are a variety of examples of methyl radicals bearing a single a-carbonyl substituent, i.e. of functional structure to show that the coupling of the unpaired spin to the a-protons may be symmetrical or unsymmetrical, as illustrated by the radical .CH,-CO-CH, (29), where the a-proton couplings are unequal7, and the radical .CH2-CO-NH, (11,32), where they are equal. In addition, the analogous coupling to the protons in the aromatic ring in radical anions from many aromatic ketones, such as that from acetophenone…”

Section: The Structure Of Radicals Formed Frommentioning

confidence: 99%

See 1 more Smart Citation

Electron paramagnetic resonance spectroscopic study of radicals derived from glycine, dl-α-alanine, and β-alanine in aqueous solution

Smith¹,

Fox²,

Mcginty³

et al. 1970

Can. J. Chem.

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The substrates glycine, dl-u-alanine, and B-alanine have been examined in turn within an aqueous continuous-flow system using the titanous chloride -hydrogen peroxide radical-generating method.The temperature was 25 i 2 "C and the p H of the reaction mixture was varied within the range of values ca. 2 to ca. 5 by addition of sulfuric acid. The electron paramagnetic resonance spectra of the following transient radicals were observed: from glycine, .CH(NHZ)COOH; from dl-a-alanine, CH3C(NNZ)COOH and .CH2CH(NH3+)COOH; and from P-alanine, CH2(NH3+)CHCOOH.

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Paramagnetic Resonance Study of Liquids during Photolysis. II. Acetone and Solutions Containing Acetone

Cited by 100 publications

References 23 publications

Micelle-induced change of mechanism in the reaction of muonium with acetone

Micelle-induced change of mechanism in the reaction of muonium with acetone

Photochemical Inactivation of Lactoperoxidase Sensitized by Carbonyl Compounds

Electron paramagnetic resonance spectroscopic study of radicals derived from glycine, dl-α-alanine, and β-alanine in aqueous solution

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