Temperature-dependent electron spin polarization of the triplet state of the primary donor in Rhodopseudomonas viridis

Brink, J.S. van den; Manikowski, H.; Gast, P.; Hoff, A.J.

doi:10.1016/0005-2728(94)90208-9

Cited by 12 publications

(16 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In principle, additional polarization can also be accumulated during the lifetime of the doublettriplet pair 3 P*IQA generated by recombination of the triplet radical pair 3 (P+I -) [13]. However, the spin relaxation time of the triplet is short [26,27] thus, we will assume that this contribution can be ignored. A general treatment of polarization transfer from a triplet state to an observer doublet state will be presented elsewhere.…”

Section: Theorymentioning

confidence: 99%

“…(26) This situation corresponds to the polarization of the observer electron spin if the parameters are chosen appropriately:…”

Section: Cidnp Oc [Hsto(a)] 2 -[Hstomentioning

confidence: 99%

“…(19) yields Eq. (26). Thus, there is a close analogy between the observer spin polarization and the CIDNP formation.…”

Section: Cidnp Oc [Hsto(a)] 2 -[Hstomentioning

confidence: 99%

“…Eqs. (26), (27)). Thus, characteristic features of the observer spin polarization in the three-spin system correspond to a basic paradigm of the CIDNP effect: in high magnetic fields, the exchange interaction between radicals in the spin-correlated pair can often be neglected when discussing CIDNP rules, while in low magnetic fields it plays an important role in creating nuclear spin polarization.…”

Section: Cidnp Oc [Hsto(a)] 2 -[Hstomentioning

confidence: 99%

See 3 more Smart Citations

The transient EPR spectra and spin dynamics of coupled three-spin systems in photosynthetic reaction centres

1999

View full text Add to dashboard Cite

The concept of introducing an additional, stable paramagnetic species into photosynthetic reaction centres to increase the information content of their spin polarized transient EPR spectra is investigated theoretically. The light-induced electron transfer in such systems generates a series of coupled three-spin states consisting of sequential photoinduced radical pairs coupled to the stable spin which acts as an "observer". The spin polarized transient EPR spectra are investigated using the coupled three-spin system P* I -Qp in pre-reduced bacterial reaction centres as a specific example which has been studied experimentally. The evolution of the spin system and the spin polarized EPR spectra of PI -Qp and Qq following recombination of the radical pair (P = primary donor, I = primary acceptor, QA = quinone acceptor) are calculated numerically by solving the equations of motion for the density matrix. The net polarization of the observer spin is also calculated analytically by perturbation theory for the case of a single, short-lived, charge-separated state The result bears a close resemblance to the chemically induced nuclear polarization (CIDNP) generated in photolysis reactions in which a nuclear spin plays the role of the observer interacting with the radical pair intermediates. However, because the Zeeman frequencies of the three electron spins involved are usually quite similar, the polarization of the electron observer spin in strong magnetic fields can reflect features of the CIDNP effect in both, high and low magnetic fields. The dependence of the quinone spin polarization on the exchange couplings in the three-spin system is investigated by numerical simulations, and it is shown that the observed emissive polarization pattern is compatible with either sign, positive or negative, for a range of exchange couplings, Jp" in the primary pair. The microwave frequency and orientation dependence of the spectra are discussed as two of several possible criteria for determining the sign of JPY .

show abstract

Section: Theorymentioning

confidence: 99%

“…(26) This situation corresponds to the polarization of the observer electron spin if the parameters are chosen appropriately:…”

Section: Cidnp Oc [Hsto(a)] 2 -[Hstomentioning

confidence: 99%

“…(19) yields Eq. (26). Thus, there is a close analogy between the observer spin polarization and the CIDNP formation.…”

Section: Cidnp Oc [Hsto(a)] 2 -[Hstomentioning

confidence: 99%

Section: Cidnp Oc [Hsto(a)] 2 -[Hstomentioning

confidence: 99%

See 2 more Smart Citations

The transient EPR spectra and spin dynamics of coupled three-spin systems in photosynthetic reaction centres

1999

View full text Add to dashboard Cite

show abstract

“…By contrast, studies on the variation of the X-band ESP spectra of the P •1 Q •ÿ A secondary radical pair in Q B -depleted, Zn 21reconstituted RCs of Rb. sphaeroides R26 when cooled in the dark and under illumination revealed only slight modifications of the cofactor arrangement (van den Brink et al, 1994). Small conformational changes depending on the illumination history were also observed for the special pair (Mu ¨h et al, 1997) and the photoactive bacteriopheophytin of the RC of Rb.…”

Section: Dependence Of Et Rates On Temperature and Illumination Protocolmentioning

confidence: 98%

Charge Recombination and Protein Dynamics in Bacterial Photosynthetic Reaction Centers Entrapped in a Sol-Gel Matrix

Kriegl

Forster

Nienhaus

2003

Biophysical Journal

View full text Add to dashboard Cite

Many proteins can be immobilized in silica hydrogel matrices without compromising their function, making this a suitable technique for biosensor applications. Immobilization will in general affect protein structure and dynamics. To study these effects, we have measured the P(+)Q(A)(-) charge recombination kinetics after laser excitation of Q(B)-depleted wild-type photosynthetic reaction centers from Rhodobacter sphaeroides in a tetramethoxysilane (TMOS) sol-gel matrix and, for comparison, also in cryosolvent. The nonexponential electron transfer kinetics observed between 10 and 300 K were analyzed quantitatively using the spin boson model for the intrinsic temperature dependence of the electron transfer and an adiabatic change of the energy gap and electronic coupling caused by protein motions in response to the altered charge distributions. The analysis reveals similarities and differences in the TMOS-matrix and bulk-solvent samples. In both preparations, electron transfer is coupled to the same spectrum of low frequency phonons. As in bulk solvent, charge-solvating protein motions are present in the TMOS matrix. Large-scale conformational changes are arrested in the hydrogel, as evident from the nonexponential kinetics even at room temperature. The altered dynamics is likely responsible for the observed changes in the electronic coupling matrix element.

show abstract

EPR characterisation of the triplet state in photosystem II reaction centers with singly reduced primary acceptor QA

Feikema

Gast

Klenina

et al. 2005

Biochimica et Biophysica Acta (BBA) - Bioenergetics

View full text Add to dashboard Cite

The triplet states of photosystem II core particles from spinach were studied using time-resolved cw EPR technique at different reduction states of the iron--quinone complex of the reaction center primary electron acceptor. With doubly reduced primary acceptor, the well-known photosystem II triplet state characterised by zero-field splitting parameters |D|=0.0286 cm(-1), |E|=0.0044 cm(-1) was detected. When the primary acceptor was singly reduced either chemically or photochemically, a triplet state of a different spectral shape was observed, bearing the same D and E values and characteristic spin polarization pattern arising from RC radical pair recombination. The latter triplet state was strongly temperature dependent disappearing at T=100 K, and had a much faster decay than the former one. Based on its properties, this triplet state was also ascribed to the photosystem II reaction center. A sequence of electron-transfer events in the reaction centers is proposed that explains the dependence of the triplet state properties on the reduction state of the iron--quinone primary acceptor complex.

show abstract

Temperature-dependent electron spin polarization of the triplet state of the primary donor in Rhodopseudomonas viridis

Cited by 12 publications

References 30 publications

The transient EPR spectra and spin dynamics of coupled three-spin systems in photosynthetic reaction centres

The transient EPR spectra and spin dynamics of coupled three-spin systems in photosynthetic reaction centres

Charge Recombination and Protein Dynamics in Bacterial Photosynthetic Reaction Centers Entrapped in a Sol-Gel Matrix

EPR characterisation of the triplet state in photosystem II reaction centers with singly reduced primary acceptor QA

Contact Info

Product

Resources

About