Carotenoid Radical Cations as a Probe for the Molecular Mechanism of Nonphotochemical Quenching in Oxygenic Photosynthesis
详细信息 查看全文
- 作者：Sergiu Amarie ; Jö ; rg Standfuss ; Tiago Barros ; Werner Kü ; hlbrandt ; Andreas Dreuw ; Josef Wachtveitl
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：April 5, 2007
- 年：2007
- 卷：111
- 期：13
- 页码：3481 - 3487
- 全文大小：168K
- 年卷期：v.111,no.13(April 5, 2007)
- ISSN：1520-5207
文摘
Nonphotochemical quenching (NPQ) is a fundamental mechanism in photosynthesis which protects plantsagainst excess excitation energy and is of crucial importance for their survival and fitness. Recently, carotenoidradical cation (Car
+) formation has been discovered to be a key step for the feedback deexcitation quenchingmechanism (qE), a component of NPQ, of which the molecular mechanism and location is still unknown. Wehave generated and characterized carotenoid radical cations by means of resonant two color, two photonionization (R2C2PI) spectroscopy. The Car+ bands have maxima located at 830 nm (violaxanthin), 880 nm(lutein), 900 nm (zeaxanthin), and 920 nm (
-carotene). The positions of these maxima depend strongly onsolution conditions, the number of conjugated C=C bonds, and molecular structure. Furthermore, R2C2PImeasurements on the light-harvesting complex of photosystem II (LHC II) samples with or without zeaxanthin(Zea) reveal the violaxanthin (Vio) radical cation (Vio+) band at 909 nm and the Zea+ band at 983 nm. Thereplacement of Vio by Zea in the light-harvesting complex II (LHC II) has no influence on the Chl excitationlifetime, and by exciting the Chls lowest excited state, no additional rise and decay corresponding to theCar+ signal observed previously during qE was detected in the spectral range investigated (800-1050 nm).On the basis of our findings, the mechanism of qE involving the simple replacement of Vio with Zea inLHC II needs to be reconsidered.
+) formation has been discovered to be a key step for the feedback deexcitation quenchingmechanism (qE), a component of NPQ, of which the molecular mechanism and location is still unknown. Wehave generated and characterized carotenoid radical cations by means of resonant two color, two photonionization (R2C2PI) spectroscopy. The Car+ bands have maxima located at 830 nm (violaxanthin), 880 nm(lutein), 900 nm (zeaxanthin), and 920 nm (-carotene). The positions of these maxima depend strongly onsolution conditions, the number of conjugated C=C bonds, and molecular structure. Furthermore, R2C2PImeasurements on the light-harvesting complex of photosystem II (LHC II) samples with or without zeaxanthin(Zea) reveal the violaxanthin (Vio) radical cation (Vio+) band at 909 nm and the Zea+ band at 983 nm. Thereplacement of Vio by Zea in the light-harvesting complex II (LHC II) has no influence on the Chl excitationlifetime, and by exciting the Chls lowest excited state, no additional rise and decay corresponding to theCar+ signal observed previously during qE was detected in the spectral range investigated (800-1050 nm).On the basis of our findings, the mechanism of qE involving the simple replacement of Vio with Zea inLHC II needs to be reconsidered.