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  • 1
    Electronic Resource
    Electronic Resource
    Micellar radical pair decay (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8260-8269 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetic-field dependence of hyperfine coupling-induced radical pair processes in micelles is studied theoretically. We show that experimental observations on reaction dynamics of triplet benzylic radical pairs can be explained by a hyperfine interaction mechanism when the exchange interaction between the unpaired spins in the radical pair confined to a micelle is taken into account. The theoretical description applied involves a stochastic Liouville equation. The time-dependent solutions of the stochastic Liouville equation qualitatively reproduce the observed magnetic-field and isotope dependence of micellar radical pair decay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459306
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  • 2
    Electronic Resource
    Electronic Resource
    Probing the dynamics of a polymer with paramagnetic end groups by magnetic fields (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 5155-5161 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show that magnetic field effects observed on reactions between two paramagnetic end groups of a polymer can be explained through the folding motion of the polymer. This folding stochastically alters the exchange interaction between the paramagnetic end groups and, thereby, affects their spin dynamics. We describe the resulting stochastic quantum system by a (Monte Carlo) computer simulation as well as by a new approximation which involves the spectrum of the stochastic interaction. This approximation can be of general use for the description of stochastic quantum systems when a diagonal stochastic interaction originates from an arbitrary, i.e., nonlinear and non-Gaussian, stochastic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450668
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Pulsed ENDOR of the photoexcited triplet states of bacteriochlorophyll a and of the primary donor P865 in reaction centers of Rhodobacter sphaeroides R-26 (1998)
    Springer
    Photosynthesis research 55 (1998), S. 189-197 
    Details
    ISSN: 1573-5079
    Keywords: bacterial reaction center ; charge transfer ; excitation delocalization ; ENDOR ; primary donor ; triplet states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photoexcited triplet states of bacteriochlorophyll a, 3BChl a, and of the primary donor in reaction centers of Rhodobacter sphaeroides R-26, 3P865, are investigated by pulsed EPR and ENDOR spectroscopy. In 3P865 a splitting of ENDOR lines and reduction of corresponding positive and negative hyperfine couplings as compared with the monomeric 3BChl a is observed. This indicates an asymmetric distribution of the triplet excitation over the two BChl a moieties, PL and PM, forming 3P865. Based on the signs of the hyperfine couplings and on a comparison with the cation and anion radical of BChl a an assignment to nuclei in the different dimer halves is proposed. This yields an estimate for the extent of delocalization of the triplet excitation over PL and PM and for the charge transfer contribution of 3P865.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006030221445
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  • 4
    Electronic Resource
    Electronic Resource
    EPR and ENDOR studies of the water oxidizing complex of Photosystem II (1996)
    Springer
    Photosynthesis research 48 (1996), S. 227-237 
    Details
    ISSN: 1573-5079
    Keywords: manganese cluster ; multiline signal ; oxygen evolution ; S-states ; water ligation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparative study of X-band EPR and ENDOR of the S2 state of photosystem II membrane fragments and core complexes in the frozen state is presented. The S2 state was generated either by continuous illumination at T=200 K or by a single turn-over light flash at T=273 K yielding entirely the same S2 state EPR signals at 10 K. In membrane fragments and core complex preparations both the multiline and the g=4.1 signals were detected with comparable relative intensity. The absence of the 17 and 23 kDa proteins in the core complex preparation has no effect on the appearance of the EPR signals. 1H-ENDOR experiments performed at two different field positions of the S2 state multiline signal of core complexes permitted the resolution of four hyperfine (hf) splittings. The hf coupling constants obtained are 4.0, 2.3, 1.1 and 0.6 MHz, in good agreement with results that were previously reported (Tang et al. (1993) J Am Chem Soc 115: 2382–2389). The intensities of all four line pairs belonging to these hf couplings are diminished in D2O. A novel model is presented and on the basis of the two largest hfc's distances between the manganese ions and the exchangeable protons are deduced. The interpretation of the ENDOR data indicates that these hf couplings might arise from water which is directly ligated to the manganese of the water oxidizing complex in redox state S2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041013
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    Paper (German National Licenses)
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