1. Volume 83, Issue 3, Pages 1701-1715 (September 2002)
Spectroscopy on Individual Light-Harvesting 1 Complexes of Rhodopseudomonas acidophila 
Martijn Ketelaars, Clemens Hofmann, Jürgen Köhler, Tina D. Howard, Richard J. Cogdell, Jan Schmidt, Thijs J. Aartsma 
Biophysical Journal 
Volume 83, Issue 3, Pages (September 2002)
DOI: /S (02)
Copyright © 2002 The Biophysical Society Terms and Conditions

2. Figure 1
Three tentative structural models for the LH1-RC complex. The αβ-subunits of the LH1 are depicted as cylinders. Qb represents the secondary quinone site of the RC. (A) A closed-ring model with the LH1 ring, consisting of 16 αβ-subunits, completely surrounding the RC and blocking the Qb site. (B) A LH1 model with incorporation of the PufX protein represented as a dimer substituting 2 αβ subunits. The PufX protein may facilitate ubiquinone transfer from the Qb site. (C) An open-ring model, consisting of 8 αβ-subunits in which the Qb site is exposed. Adapted from Cogdell et al. (1996).
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions

3. Figure 2
Ensemble spectra of LH1-RC complex of Rps. acidophila. (a) Room-temperature absorption spectrum in solution (solid line) and the fluorescence-excitation spectrum at 1.2K of a high-concentrated sample with 1% PVA spincoated onto a LiF substrate (dotted line). The dashed line indicates the transmission of the filter used in the emission path (center, 910nm; FWHM 20nm). (b) Fluorescence-excitation spectrum of a bulk ensemble of LH1-RC complexes in a PVA-film at 1.2K (dotted line, same as in a) together with the sum of 24 spectra recorded from individual complexes (solid line). The spectrum of each individual complex was obtained at 1.2K in a PVA film at an intensity of 2 to 10W/cm2. The spectra are scaled to the same intensity.
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions

4. Figure 3
Eight examples of fluorescence-excitation spectra of individual LH1-RC complexes of Rps. acidophila. Each individual complex was studied at 1.2K in a PVA-film at an intensity of 2 to 10W/cm2. The arrows point towards the narrow absorption lines present in some of the spectra.
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions

5. Figure 4
Fluorescence-excitation experiment on an individual LH1-RC complex (number 1) of Rps. acidophila at 1.2K. (a, Top) Stack of 300 fluorescence-excitation scans recorded at a scan speed of 3nm/s. After each scan, corresponding to one horizontal line, the excitation polarization was rotated by 3.6° (see Materials and Methods). The series of scans correspond to five complete turns of the polarization. The fluorescence intensity is indicated by the grey scale (white; high intensity). (a, Bottom) Average of the 300 individual scans. The numbers 1 to 4 indicate the four different bands that were observed for this particular complex. (b, Top) The relative intensity of the four bands as a function of the excitation polarization. From the phase difference between these oscillations the mutual polarization of the bands was determined. (b, Bottom) The two spectra of band 2 and 3 plotted at their maximum intensity. Their mutual orientation was 88±3°. No data processing was done except for averaging of three adjacent points. The encircled bidirectional arrows in the center of the figure indicate the polarization of the excitation light. No background was subtracted, and therefore the transmission of the detection window is visible in the red edge of the spectrum.
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions

6. Figure 5
Four different types of polarization behavior of the fluorescence-excitation spectra of individual LH1-RC complexes (Rps. acidophila). The upper panels in I, II, III, and IV show a stack of 100 fluorescence-excitation scans. After each scan the excitation polarization was rotated by 3.6° (see Materials and Methods). The fluorescence intensity is indicated by the grey scale (white; high intensity). Five complete turns of the polarization were made in successive scans, although only two turns are shown. The two spectra at the bottom of I, II, III and IV are taken at a specific polarization, indicated by the two white dashed lines in the corresponding upper panel. Experimental conditions as in Fig. 3. The encircled numbers indicate the particular complex chosen. In I two broad orthogonal bands are observed that show the same behavior as for complex 1 (Fig. 4). In II two broad bands are present with a mutual angle of less than 90°. In III one broad band is observed with no absorption at the perpendicular polarization. In IV multiple narrow lines are observed. The arrows point towards the narrow absorption lines present in some of the spectra.
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions

7. Figure 6
Simulation of the excited state energies of both LH2 (a) and LH1 (b). Only the lowest part of the exciton manifold is depicted. For LH2 the atomic co-ordinates of Rps. acidophila were used consisting of 18 pigments with a C9 symmetry (1kzu.pdb). For LH1 a closed-ring model was used consisting of 32 pigments with a C16 symmetry. The mutual distances and orientations of the pigments were taken to be the same as in LH2 (Rps. acidophila), resulting in the same intra en interdimer interaction strengths. The left part of both figures depicts the manifolds without site heterogeneity. The right part is obtained with the introduction of site heterogeneity with Γintra/Vavg=1. Γintra is defined as the full width at FWHM of a Gaussian distribution of site energies within a complex. Vavg is the average of the inter- and intradimer interaction between the pigments. The transition probabilities from the ground state to the various excited states of the exciton manifold are depicted by the length of the black bars. In the presence of site heterogeneity averaging over 10,000 complexes was performed. See Material and Methods for a more detailed description of the simulations. Note that the LH2 manifold is only shown for comparison to the LH1 case and does not match the exciton manifold as proposed by Ketelaars et al. (2001) based on the spectra of individual LH2 complexes.
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions

8. Figure 7
Simulation of the absorption spectrum of an individual LH1 complex, which forms a complete ring (A), a LH1 ring with 1 subunit missing (B), and a LH1 complex with a partial ring consisting of eight αβ subunits (C). The overall absorption spectrum in the xy plane of the complex is plotted (solid line) together with the absorption spectra along the x axis (dashed line) and y axis (dotted line). The x axis is chosen along the transition-dipole moment of one of the kcirc=±1 states in the case of A and along the k=2 state in the cases B and C. The insets sketch the arrangement of the subunits in the xy plane, showing the Qy transition-dipole moments (arrows). The lowest energetic state of the exciton manifold is assigned a homogenous linewidth of 1cm−1. All the other states 100cm−1. See Material and Methods for a more detailed description of the simulations.
Biophysical Journal  , DOI: ( /S (02) )
Copyright © 2002 The Biophysical Society Terms and Conditions