Parameters of paramagnetic relaxation were determined by OD ESR and quantum beats techniques for a recombining pair of radical ions (DPS-d10)+/(PTP-d14)− inn-hexane, isooctane,cis-decalin, and squalane solutions. The T2 relaxation time determined by quantum beats technique is independent of...

With limited reductant and nitrite under anaerobic conditions, copper-containing nitrite reductase (NiR) of Rhodobacter sphaeroides yielded endogenous NO and the Cu(I)NO derivative of NiR. 14N- and 15N-nitrite substrates gave rise to characteristic 14NO and 15NO EPR hyperfine features indicating...

Magnetosensitive radiofluorescence resulting from geminate recombination of a spin triad involving a radical ion and a biradical ion formed radiolytically in non-polar solutions has been investigated theoretically. The effect of exchange interaction in the biradical ion on the kinetics and yield...

Cytochrome c' is a heme protein from a denitrifying variant of Rhodobacter sphaeroides which may serve to store and transport metabolic NO while protecting against NO toxicity. Its heme site bears resemblance through its 5-coordinate NO-binding capability to the regulatory site in soluble...

Di-μ-oxo MnIII−MnIV dimers are models for coupled, mixed-valence manganese in the oxygen-evolving centers of green plants. Using a recently reported method of exchanging water oxygen into the di-μ-oxo cross-bridges , we have incorporated 17O into the μ-oxo cross bridges of the MnIII−MnIV...

Copper nitrite reductase contains a T1 and T2 Cu center and catalyzes the one electron reduction of nitrite to NO. This study determines that reaction of the reduced enzyme with excess NO generates the T1 reduced T2 oxidized-nitrite bound form and not the η2-NO·Cu+ species observed in the...

The five-coordinate NO-bound heme in cytochrome c‘ from an overexpressing variant of denitrifying R. sphaeroides 2.4.3 was investigated by proton, nitrogen, and deuterium Q-band ENDOR (electron nuclear double resonance). ENDOR was a direct probe of the unpaired electron density on the nitrogen...

Activated bleomycin (ABLM) is a drug−Fe(III)−hydroperoxide complex kinetically competent in DNA attack (via H4‘ abstraction). This intermediate is relatively stable, but its spontaneous conversion to ferric bleomycin (Fe(III)·BLM) is poorly characterized because no observable intermediate...

The electronic structure of the 5-coordinate quantum-mechanically mixed-spin (sextet-quartet) heme center in cytochrome c‘ was investigated by electron nuclear double resonance (ENDOR), a technique not previously applied to this mixed-spin system. Cytochrome c‘ was obtained from...

Supercritical carbon dioxide was used as a solvent to produce polymeric films on fused silica plates and metal (Al, Mg) powders. Two polymers, poly(vinylidene fluoride) and poly(4-vinylbiphenyl) (PVB), were used. Polymer-coated particles of metal powders exhibit enhanced resistance to the...

Paramagnetic derivatives of tolan, anthracene, and terphenyl of the A−Sp−R• type, where A is an aromatic group, R• is a stable radical center, and Sp is a spacer, were synthesized.

Paramagnetic derivatives of tolan, anthracene, and terphenyl of the A−Sp−R• type, where A is an aromatic group, R• is a stable radical center, and Sp is a spacer, were synthesized. The electronic absorption and luminescence spectra of these compounds were examined. The introduction of the...

Quantum beats caused by the hyperfine coupling (hfc) with magnetically equivalent protons were observed in the recombination fluorescence of the singlet-correlated pairs of secondary radical ions generated in cyclohexane solutions by ionizing radiation. In agreement with theoretical predictions,...

The fractions Θβ and ΘX of spin-correlated singlet radical-ion pairs in alkane solutions irradiated by β-particles and X-rays were got from experiments on magnetic field effects and quantum beats in recombination fluorescence. The ratio Θβ/ΘX values of 1.3−2.8 for the solvent series...

Methods of synthesising stable 2-imidazoline nitroxides linked to a pyrazole moiety either directly or through a phenylethynylic bridge have been developed; an unusually strong temperature dependence of μeff for 2-(1-methylpyrazolyl-5)-4,4,5,5-tetramethyl- 1-oxyl-2-imidazoline-3-oxide is observed.

The quantum beats and magnetic field effect on the reaction yield spectroscopy techniques were employed to study the formation of diphenyl sulfide radical cations in squalane solutions under ionizing irradiation. It is demonstrated that the precursors of diphenyl sulfide radical cations are...

The technique of magnetic field modulation of reaction yield (MARY) spectroscopy was employed to obtain the ESR spectrum of squalane holes that are formed under the action of ionizing radiation at room temperature. The spectrum is shown to consist of a single line which is homogenously narrowed...

Amplitudes of quantum oscillations observed in the recombination fluorescence of the (diphenylsulfide-d10)+/(p-terphenyll-d14)− radical ion pairs in alkane solutions have been used to estimate a fraction of spin-correlated singlet pairs Θ in the radiation track. Θ values of 0.36 – 0.54 for...

The phase shift of quantum oscillations observed in the recombination fluorescence of the (diphenylsulfide-d10)+/(p-terphenyl-d14)− radical ion pair in isooctane has been detected experimentally. The shift is caused by the delay in (diphenylsulfide-d10)+ formation in the reaction of solvent...

Acyl derivatives of 2-aminopyridine, 2-aminopyrimidine, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl were obtained from long-chain diacetylenic acyl chlorides and the corresponding heterocyclic compounds. Spreading isotherms of monolayers on a...

Cleavage of long-chain 2-methyl-3,5-alkadiyne-2-ols in anhydrous benzene in the presence of KOH (Favorsky retroreaction) is accompanied by migration of the triple bonds and it affords 2,4-alkadiynes. Proton-donor additives (alcohol or water) completely suppress the isomerization process and...

Photoenolization of 1-methylanthraquinone (AQ) and its deuterated analogue (AQ-d,) has been studied by laser flash photolysis over a wide temperature range (120-340 K). Phototransfer of a H (or D) atom has been found to occur in both the singlet and triplet nr* states. The temperature dependence...

It has been found that the radical (CH3)2C̊CH2CH(NHCOCH3)CO2H transforms into (CH3)2CHCH2C̊(NHCOCH3)CO2H at temperatures of 293–315 K by the first-order reaction. The kinetic parameters determined for this reaction are k0 = 9.2 × 109s−1 and E‡ = 20.0 ±0.6 kcal/mole. The substitution of...

The optical and ESR spectra have been examined for complexes of Cu(I) with various radicals, which contain various numbers of Cl ions in the central-atom coordination sphere. The spin-Hamiltonian parameters have been determined for all these radical complexes, and the observed ESR spectra have...