THE HEAT OF COMBUSTION OF THULIUM<sup>1</sup>

Huber, Elmer J.; Head, Earl L.; Holley, Charles E.

doi:10.1021/j100832a510

Cited by 17 publications

(14 citation statements)

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“…Minimum least-squares fits to a model spin Hamiltonian including only the Zeeman interaction of radicals with an isotropic orientation distribution are shown as dashed lines together with the measured spectra. The g-values obtained from these fŸ [43] are in accordance with previous measurements within the error limits [51,60,65,66,72,77,78]. In discussing differences of g-values, such as Ag = (g.~~ -g=), the error in the 360 GHz EPR measurements is only 2.10 -s, and the small shifts in the order of 10 -4 that are induced by the mutations of the protein environment of P'+ are detected with high significance.…”

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidessupporting

confidence: 87%

“…The expected shifts of the g-tensor components upon mutation will be extremely small -in the order of 10 -4 -as has been shown by previous W-band measurements on similar mutants [65,66]. The further increase of EPR frequency and B 0 field by a factor of 4 to 360 GHz and 12.9 T, however, provides the spectral resolution necessary to fully resolve all three principal g-tensor components of P'+ randomly oriented in frozen solution [77], and to measure their mutation-induced shifts [43] with high precision.…”

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidessupporting

confidence: 55%

“…The effect on the electronic structure caused by mutations can be measured, e.g., by transient absorption in the visible/near infrared regions [5,6,24] or via oxidation-potential changes [24,63,64] resulting in characteristic shifts of gtensor and hyperfine tensor components that are resolved by high-field EPR [43,51,65] and ENDOR [16,[66][67][68], respectively. For example, in the course of X-band ENDOR and TRIPLE (electron-nuclear-nuclear triple resonance) [69] experiments on the R-26.1 mutant and wild-type RCs [1,61,62,70], a pronounced asymmetry of 2:1 of the spin density distribution over the two dimer halves in Pff6+5 was determined, favoring the BChl axially ligated by the L subunit.…”

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidesmentioning

confidence: 99%

“…P86+5 in photosynthetic RCs exhibits extremely small g-tensor anisotropies of about l0 -3. It is, therefore, a prime example of a situation where even high-field EPR at 3.4 T/95 GHz can only partially resolve the powder pattem of disordered samples [51,60,65,66,72]. To move these samples into the high-field regime already at W-band frequencies, one has to reduce the line width by deuteration or to employ a single crystal for the measurements.…”

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidesmentioning

confidence: 99%

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High-field EPR, ENDOR and ELDOR on bacterial photosynthetic reaction centers

et al. 2007

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We report on recent 95 and 360 GHz high-field electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and pulsed electron-electron double resonance (PELDOR) studies of wild-type and mutant reaction centers (RCs) from the photosynthetic bacterium Rhodobacter sphaeroides. Taking advantage of the excellent spectral and temporal resolution of EPR at 95 and 360 GHz, the electron-transfer (ET) cofactors radical ions and spin-correlated radical pairs were characte¡ by their g-and hyperfine-tensor components, their anisotropic T, relaxation as well as by the dipolar interaction between P~~sQ~-radical pairs. The goal of these studies is to better understand the dominant factors determining the specificity and directionality of transmembrane ET processes in photosynthetic RC proteins. In particular, our multifrequency experiments elucidate the subtle cofactor-protein interactions, which are essential for fine-tuning the ET characteristics, e.g., the unidirectionality of the light-induced ET pathways along the A branch of the RC protein. By our high-field techniques, frozen-solution RCs of novel site-specific single and double mutants of R. sphaeroides were studied to modulate the ET characteristics, e.g., even to the extent that dominant B branch ET prevails. The presented multifrequency EPR work culminates in first 360 GHz ENDOR results from organic nitroxide radicals as well as in first 95 GHz high-field PELDOR results from orientationally selected spin-polarized radical pairs Ps which a|low to determine the full geometrical structure of the pairs even in frozen-solution RCs.

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Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidessupporting

confidence: 87%

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidessupporting

confidence: 55%

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidesmentioning

confidence: 99%

Section: Ghz Cw Epr On P8~5 Of Mutant Rcs From R Sphaeroidesmentioning

confidence: 99%

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High-field EPR, ENDOR and ELDOR on bacterial photosynthetic reaction centers

et al. 2007

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“…19, and in ref. 20 it is compared also to a monomer-type axis system, localized on the L-half of the dimer. For D+' the largest g-tensor component is oriented along the direction connecting the nitrogen atoms of rings I and III of the BCh1 a.…”

Section: Discussionmentioning

confidence: 99%

Theg-tensor anisotropy of the triplet state of the primary electron donor in the photosynthetic bacteriumRhodobacter sphaeroides by high-field (95 GHz) EPR

Labahn

Huber

2001

Appl. Magn. Reson.

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The anisotropy of the g-tensor of the light-induced triplet state of the primary electron donor (D) of the photosynthetic bacterium Rhodobacter sphaeroides is determined by electron-spinecho-detected electron paramagnetic resonance at 95 GHz. Measurements on frozen solutions of quinone-depleted reaction centers yield g-values along the principal directions of the zero-field splitting tensor (Norris J.R., Budil D.E., Gast P., Chang C.H., ElKabbani 0., Schiffer M.: Proc. Natl.Acad. Sei. USA 86, [4335][4336][4337][4338][4339] 1989). g-Values determined are: 2.00308, 2.00238, and 2.00138. The deviation from axial symmetry and the z-component of the g-tensor are smaller than observed in the cation radical of D.

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