TY - JOUR
T1 - The spectroscopic and photochemical properties of locked-15,15'-cis-spheroidene in solution and incorporated into the reaction center of rhodobacter sphaeroides r-26.1
AU - Bautista, James A.
AU - Chynwat, Veeradej
AU - Cua, Agnes
AU - Jansen, Frans Jos
AU - Lugtenburg, Johan
AU - Gosztola, David
AU - Wasielewski, Michael R.
AU - Frank, Harry A.
N1 - Funding Information:
The authors wish to thank Professors George Britton, Richard Cogdell, Robert Connors, and Ronald Chris-tensen for helpful discussions. This work was supported by grants to H.A.F. from the National Institutes of Health (GM-30353), the Human Frontier Science Program, the United States Department of Agriculture (92-37306-7690) and the University of Connecticut Research Foundation, and to J.L. from the Human Frontier Science Program, and the Netherlands Foundation of Chemical Research (SON), which is financed by the Netherlands Organization for the Advancement of Pure Research (NWO). The work at Argonne National Laboratory was supported by the Office of Basic Energy Sciences, Division of Chemical Sciences, US Department of Energy under contract W-31-109-Eng-38.
PY - 1998
Y1 - 1998
N2 - The spectroscopic and photochemical properties of the synthetic carotenoid, locked-15,15'-cis-spheroidene, were studied by absorption, fluorescence, circular dichroism, fast transient absorption and electron spin resonance spectroscopies in solution and after incorporation into the reaction center of Rhodobacter (Rb.) sphaeroides R-26.1. HPLC purification of the synthetic molecule reveals the presence of several di-cis geometric isomers in addition to the mono-cis isomer of locked-15,15'-cis-spheroidene. In solution, the absorption spectrum of the purified mono-cis sample was red-shifted and showed a large cis-peak at 351 nm compared to unlocked all-trans spheroidene. Molecular modeling and semi-empirical calculations reveal how geometric isomerization and structural factors affect the room temperature spectra. The spectroscopic studies of the purified locked-15,15'-mono-cis molecule in solution reveal a more stable manifold of excited states compared to the unlocked spheroidene. Reaction centers of Rb. sphaeroides R-26.1 in which the locked-15,15'-cis-spheroidene was incorporated show no difference in either the spectroscopic properties or photochemistry compared to reaction centers in which unlocked spheroidene was incorporated or to Rb. sphaeroides wild type strain 2.4.1 reaction centers which naturally contain spheroidene. The data suggest that the natural selection of a cis-isomer of spheroidene for incorporation into native reaction centers of Rb. sphaeroides wild type strain 2.4.1 is more determined by the structure or assembly of the reaction center protein than by any special quality of the cis-isomer of the carotenoid that would affect its ability to participate in triplet energy transfer or carry out photoprotection.
AB - The spectroscopic and photochemical properties of the synthetic carotenoid, locked-15,15'-cis-spheroidene, were studied by absorption, fluorescence, circular dichroism, fast transient absorption and electron spin resonance spectroscopies in solution and after incorporation into the reaction center of Rhodobacter (Rb.) sphaeroides R-26.1. HPLC purification of the synthetic molecule reveals the presence of several di-cis geometric isomers in addition to the mono-cis isomer of locked-15,15'-cis-spheroidene. In solution, the absorption spectrum of the purified mono-cis sample was red-shifted and showed a large cis-peak at 351 nm compared to unlocked all-trans spheroidene. Molecular modeling and semi-empirical calculations reveal how geometric isomerization and structural factors affect the room temperature spectra. The spectroscopic studies of the purified locked-15,15'-mono-cis molecule in solution reveal a more stable manifold of excited states compared to the unlocked spheroidene. Reaction centers of Rb. sphaeroides R-26.1 in which the locked-15,15'-cis-spheroidene was incorporated show no difference in either the spectroscopic properties or photochemistry compared to reaction centers in which unlocked spheroidene was incorporated or to Rb. sphaeroides wild type strain 2.4.1 reaction centers which naturally contain spheroidene. The data suggest that the natural selection of a cis-isomer of spheroidene for incorporation into native reaction centers of Rb. sphaeroides wild type strain 2.4.1 is more determined by the structure or assembly of the reaction center protein than by any special quality of the cis-isomer of the carotenoid that would affect its ability to participate in triplet energy transfer or carry out photoprotection.
KW - Carotenoid
KW - Electron spin resonance
KW - Energy transfer
KW - Geometric isomerization
KW - Optical spectroscopy
KW - Photoprotection
KW - Triplet state
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U2 - 10.1023/A:1005955425420
DO - 10.1023/A:1005955425420
M3 - Article
AN - SCOPUS:0031921683
VL - 55
SP - 49
EP - 65
JO - Photosynthesis Research
JF - Photosynthesis Research
SN - 0166-8595
IS - 1
ER -