Exchange effects and cidep

Jenks, William S.; Turro, Nicholas J.

doi:10.1163/156856790x00111

Cited by 41 publications

(43 citation statements)

References 99 publications

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“…is the consequence of the principle of conservation of spin angular momentum [ 8,13,14]. The symbol # is used here and below for designation of electron polarization, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Single-phase primary electron spin polarization transfer in spin-trapping reactions

Turro

Khudyakov

1992

Chemical Physics Letters

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“…is the consequence of the principle of conservation of spin angular momentum [ 8,13,14]. The symbol # is used here and below for designation of electron polarization, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The two-phase (or multiplet) ESPT has been observed in reactions of addition to double bonds [6,7,9-l 1 ] ; the direct transfer of single-phase (or net) polarization was reported only for hydrogenatom transfer reactions [ 15 ] and for reactions with stable nitroxyl radicals [ 8,161 to the best of our knowledge .…”

Section: Introductionmentioning

confidence: 99%

Single-phase primary electron spin polarization transfer in spin-trapping reactions

Turro

Khudyakov

1992

Chemical Physics Letters

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“…Spin-polarized nitroxides can be generated by chemically induced dynamic electron polarization (CIDEP) by quenching of triplet excited states with nitroxides. [8][9][10] High triplet quantum yields, fast intersystem crossing, and high triplet energies favor aromatic ketones, such as benzophenone derivatives as triplet sensitizers in CIDEP experiments. If the aromatic ketone and the pubs.acs.org/JPCL nitroxide are covalently linked, then the observed spin-polarization of the nitroxide is optimized.…”

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confidence: 99%

Electron Spin Polarization Transfer from a Nitroxide Incarcerated within a Nanocapsule to a Nitroxide in the Bulk Aqueous Solution

Jockusch

Zeika

Nithyanandhan

et al. 2010

J. Phys. Chem. Lett.

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A thioxanthone derivative containing a covalently attached 15 N-labeled nitroxide was incarcerated into an octaacid nanocapsule. Photoexcitation of the thioxanthone chromophore generated electron spin polarization of the nitroxide. This spin polarization of the 15 N-labeled nitroxide was transferred through the walls of the carcerand to a 14 N-labeled nitroxide in external bulk solvent, a process that was directly observed by time-resolved EPR spectroscopy. The efficiency of the communication between the incarcerated guest and molecules in the bulk solvent was shown to be controlled by supramolecular factors such as Coulombic attraction and repulsion between the guest@host complex and charged molecules in the bulk solvent phase.

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“…Electron spin polarization (ESP), routinely detected by TREPR, is a major tool for establishing the sequence of free radical events in the nanosecond to microsecond timeframes (21)(22)(23)(24)(25)(26)(27)(28). To determine whether EPR with nanosecond time resolution can follow the photochemistry of RPE cells and to confirm the suggestion that melanin radicals are generated from the photoexcited triplet state (20), TREPR spectroscopy was used to study human RPE cells and tyrosinederived synthetic melanin, revealing details of melanin photochemistry.…”

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confidence: 99%

Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis

Seagle

Rezai

Kobori

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

103

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Time-resolved electron paramagnetic resonance (TREPR) spectroscopy was used to study melanin free radicals in human retinal pigment epithelium (RPE) cells and tyrosine-derived synthetic melanin. TREPR signal traces from RPE cells reveal in vivo light-induced melanin free radical photochemistry in more detail than previously known. Electron spin polarization reflecting a non-Boltzmann population within the energy levels of the spin system is observed in RPE cells as the result of the triplet state photoproduction and subsequent disappearance of free radicals in the melanin polymer. In a set of RPE cells cultured from individual sources, differences in optical absorption, continuous wave EPR spectra, and TREPR signals were correlated with apoptosis assays performed by flow cytometry. Continuous wave EPR spectra of RPE cells and TREPR of acidified synthetic melanin suggest that increased melanin aggregation provides an increase in photoprotection in the RPE cells that are relatively less susceptible to blue light-induced apoptosis.continuous wave EPR ͉ electron spin polarization ͉ time-resolved EPR I n the eye, retinal pigment epithelium (RPE) is a monolayer of cuboidal cells between the photoreceptors and choriocapillaris of the eye and is specialized to uptake, phagocytize, and recycle the outer segment of photoreceptors and retinaldehyde, the chromophore of rhodopsin (1). RPE cell death plays a major role in the pathogenesis of age-related macular degeneration, the leading cause of blindness in the population Ͼ60 years of age in the developed world (2). Possible reasons given for the degeneration of RPE cells are their exposure to high oxidative stress and damaging irradiation (2-6).The pigment melanin, found in RPE cells, is a heterogeneous polymer consisting of various monomers believed to be oxidation products of dopa (dihydroxyphenylalinine) derived from tyrosine (7). Melanin contains intrinsic, indolesemiquinone-like doublet-state radicals (8, 9). Extrinsic indolesemiquinone-like radicals are reversibly photogenerated under visible or UV irradiation (9). RPE melanin serves a photoprotective role by absorbing radiation and scavenging free radicals and reactive oxygen species (ROS) (8-11). Evidence also exists for a phototoxic role for melanin in RPE cells, especially in aged cells, including measurable ROS photoproduction (8,(12)(13)(14)(15)(16)(17)(18). Electron paramagnetic resonance (EPR) spectroscopy enables a sensitive and nondestructive analysis and differentiation of natural melanin (9,19,20). The photophysical, redox, and aggregation properties of melanin as well as its ability to bind metals, proteins, and drugs have stimulated numerous studies in chemical, physical, and medical research (8, 9). The diversity and interrelations of its properties and the lack of chemical structures have hampered a clear understanding of the roles of melanin in RPE cells (8,9). Nanosecond time-resolved (TR) EPR studies have not been reported despite the relevance of TREPR to the study of melanin photochemistry (9). El...

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Exchange effects and cidep

Cited by 41 publications

References 99 publications

Single-phase primary electron spin polarization transfer in spin-trapping reactions

Single-phase primary electron spin polarization transfer in spin-trapping reactions

Electron Spin Polarization Transfer from a Nitroxide Incarcerated within a Nanocapsule to a Nitroxide in the Bulk Aqueous Solution

Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis

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