Two-photon excitation spectroscopy of carotenoid-containing and carotenoid-depleted LH2 complexes from purple bacteria.
We applied two-photon fluorescence excitation spectroscopy to LH2 complex from purple bacteria Allochromatium minutissimum and Rhodobacter sphaeroides . Bacteriochlorophyll fluorescence was measured under two-photon excitation of the samples within the 1200-1500 nm region. Spectra were obtained for both carotenoid-containing and -depleted complexes of each bacterium to allow their direct comparison. The depletion of carotenoids did not alter the two-photon excitation spectra of either bacteria. The spectra featured a wide excitation band around 1350 nm (2x675 nm, 14,800 cm(-1)) which strongly resembled two-photon fluorescence excitation spectra of similar complexes published by other authors. We consider obtained experimental data to be evidence of direct two-photon excitation of bacteriochlorophyll excitonic states in this spectral region.
Stepanenko
Ilya
I
A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119992 Leninskie Gory, MGU1S40, Moscow, Russia. ilya@ilc.edu.ru
Kompanetz
Viktor
V
Makhneva
Zoya
Z
Chekalin
Sergey
S
Moskalenko
Andrei
A
Razjivin
Andrei
A
D001429:Bacteriochlorophylls / Q000737:chemistry*; D002338:Carotenoids / Q000737:chemistry*; D002841:Chromatiaceae / Q000737:chemistry* / Q000254:growth & development; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D017785:Photons; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids