Stark effect measurements on monomers and trimers of reconstituted light-harvesting complex II of plants.
The electric-field induced absorption changes (Stark effect) of reconstituted light-harvesting complex II (LHCII) in different oligomerisation states-monomers and trimers-with different xanthophyll content have been probed at 77 K. The Stark spectra of the reconstituted control samples, containing the xanthophylls lutein and neoxanthin, are very similar to previously reported spectra of native LHCII. Reconstituted LHCII, containing lutein but no neoxanthin, shows a similar electrooptical response in the Chl a region, but the Stark signal of Chl b around 650 nm amounts to at most approximately 25% of that of the control samples. We conclude that neoxanthin strongly modifies the electronic states of the nearby Chl b molecules causing a large electrooptical response at 650 nm stemming from one or more Chls b in the control samples. Ambiguities about the assignment of several bands in the Soret region [Biochim. Biophys. Acta 1605 (2003) 83] are resolved and the striking difference in electric field response between the two lutein molecules is confirmed. The Stark effect in the carotenoid spectral region in both control and neoxanthin-deficient samples is almost identical, showing that the neoxanthin Stark signal is small and much less intense than the lutein Stark signal.
Palacios
Miguel A
MA
Department of Biophysics and Physics of Complex Systems, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands. miguelan@nat.vu.nl
Caffarri
Stefano
S
Bassi
Roberto
R
van Grondelle
Rienk
R
Amerongen Hv
Herbert van
Hv
D002338:Carotenoids / Q000737:chemistry; D002734:Chlorophyll / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D014975:Lutein / Q000737:chemistry / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D010944:Plants / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D013057:Spectrum Analysis; D024341:Xanthophylls / Q000032:analysis / Q000737:chemistry / Q000378:metabolism
D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011994:Recombinant Proteins; D024341:Xanthophylls; D002734:Chlorophyll; D002338:Carotenoids; C037184:chlorophyll b; C011947:neoxanthin; D014975:Lutein