TY - JOUR
T1 - Triplet Charge Recombination in Heliobacterial Reaction Centers Does Not Produce a Spin-Polarized EPR Spectrum
AU - Ferlez, Bryan
AU - Agostini, Alessandro
AU - Carbonera, Donatella
AU - Golbeck, John H.
AU - Van Der Est, Art
N1 - Funding Information:
The work was supported by NSERC in the form of a Discovery Grant to AvdE and by a grant from the Photosynthetic Systems Program, Chemical Sciences, Geosciences, & Biosciences (CSGB) Division, US Department of Energy (DE-FG02-98ER20314) to JHG. BF, JHG and AvdE thank Stefan Weber and his group for their great hospitality during our stay in Freiburg. We also thank Donald Bryant for providing the culture of C. tepidum.
Publisher Copyright:
© 2017 Walter de Gruyter GmbH.
PY - 2017/3/1
Y1 - 2017/3/1
N2 - In photosynthetic reaction centers, reduction of the secondary acceptors leads to triplet charge recombination of the primary radical pair (RP). This process is spin selective and in a magnetic field it populates only the T0 state of the donor triplet state. As a result, the triplet state of the donor has a distinctive spin polarization pattern that can be measured by transient electron paramagnetic resonance (TREPR) spectroscopy. In heliobacterial reaction centers (HbRCs), the primary donor, P800, is composed of two bacteriochlorophyll g′ molecules and its triplet state has not been studied as extensively as those of other reaction centers. Here, we present TREPR and optically detected magnetic resonance (ODMR) data of 3P800 and show that although it can be detected by ODMR it is not observed in the TREPR data. We demonstrate that the absence of the TREPR spectrum is a result of the fact that the zero-field splitting (ZFS) tensor of 3P800 is maximally rhombic, which results in complete cancelation of the absorptive and emissive polarization in randomly oriented samples.
AB - In photosynthetic reaction centers, reduction of the secondary acceptors leads to triplet charge recombination of the primary radical pair (RP). This process is spin selective and in a magnetic field it populates only the T0 state of the donor triplet state. As a result, the triplet state of the donor has a distinctive spin polarization pattern that can be measured by transient electron paramagnetic resonance (TREPR) spectroscopy. In heliobacterial reaction centers (HbRCs), the primary donor, P800, is composed of two bacteriochlorophyll g′ molecules and its triplet state has not been studied as extensively as those of other reaction centers. Here, we present TREPR and optically detected magnetic resonance (ODMR) data of 3P800 and show that although it can be detected by ODMR it is not observed in the TREPR data. We demonstrate that the absence of the TREPR spectrum is a result of the fact that the zero-field splitting (ZFS) tensor of 3P800 is maximally rhombic, which results in complete cancelation of the absorptive and emissive polarization in randomly oriented samples.
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U2 - 10.1515/zpch-2016-0825
DO - 10.1515/zpch-2016-0825
M3 - Article
AN - SCOPUS:85012283244
SN - 0942-9352
VL - 231
SP - 593
EP - 607
JO - Zeitschrift fur Physikalische Chemie
JF - Zeitschrift fur Physikalische Chemie
IS - 3
ER -