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Results: 3

1.
Fig. 1.

Fig. 1. From: Room temperature femtosecond X-ray diffraction of photosystem II microcrystals.

(A) Light microscope image of crystals (average size of 10 μm) of PS II used for the XRD measurements. (B) X-ray diffraction pattern of PS II obtained at CXI using a pulse width of < 50 fs and a flux of 3.4 × 1011 photons/pulse at 9 keV. Resolutions of some highlighted Bragg spots are given in yellow and resolution at edges of the selected area of the detector are indicated by white dashed circles. The background was removed by subtracting the average image of 1,052 misses recorded directly before and after the crystal diffraction. (C) Enlarged view of an area in the top left corner of the diffraction pattern shown in B (marked by a blue box) to show highest resolution spots observed.

Jan Kern, et al. Proc Natl Acad Sci U S A. 2012 June 19;109(25):9721-9726.
2.
Fig. 3.

Fig. 3. From: Room temperature femtosecond X-ray diffraction of photosystem II microcrystals.

Comparison of electron density computed from CXI data with SR data truncated to 6.5 Å resolution. Overview of the electron density (blue mesh) for one monomer of PS II computed from the CXI data (A) and from the truncated SR data (B). Protein is shown as cartoon in yellow; 2mFo-DFc electron density is contoured at 1σ; view is along the membrane plane with cytoplasm at top. Electron density in the region of the Mn4CaO5 cluster computed from the CXI data (C) or from the truncated SR data (D), respectively, view direction is approximately 90 deg rotated with respect to Fig. 2B and is along the membrane plane, with cytoplasm at the top, lumen at the bottom. Protein is shown as cartoon in yellow (D1) and magenta (CP43), Mn as violet spheres and Ca as orange sphere. The lumenal end of TMH c as well as helix cd and the C-terminal helix (eC) of D1 and the ef helix of CP43 are labeled. The 2mFo-DFc electron density map is contoured at 1σ (blue mesh); the difference density (mFo-DFc map) is shown at +3σ (green mesh) and at -3σ (red mesh).

Jan Kern, et al. Proc Natl Acad Sci U S A. 2012 June 19;109(25):9721-9726.
3.
Fig. 2.

Fig. 2. From: Room temperature femtosecond X-ray diffraction of photosystem II microcrystals.

Electron density obtained from femtosecond PS II microcrystal diffraction at CXI, 2mFo-DFc electron density maps are shown as blue mesh, omit maps (mFo-DFc) as green (positive) and red (negative) mesh, respectively. (A) Electron density map of PS II computed to a resolution of 6.5 Å, contoured at 1σ, view is along the membrane plane with cytoplasmic side on the top, lumenal side on the bottom. One monomer of PS II is shown as yellow cartoon, cofactors are shown as green sticks. The second monomer in the PS II dimer and the symmetry equivalent dimers in the unit cell are not shown. For better orientation the extrinsic subunit PsbO is labeled. (B) Electron density map of the region around the OEC; view is approximately perpendicular to the membrane plane, from the cytoplasmic side. Protein is shown as cartoon with subunit D1 in yellow and subunit CP43 in magenta. For better orientation the cd-helix and the C terminus of D1 and the ef-loop of CP43 as well as three of the protein ligands (Asp170, Glu333, and Asp342) of the OEC are indicated. The positions of Mn and Ca ions as derived from the 2.9 Å structure (20) are shown as violet and orange spheres, respectively. The electron density map is contoured at 1σ, omit maps at ± 3σ. (C) Electron density in the region around the nonheme Fe (shown as cyan sphere), helices d and e of subunits D1 (yellow) and D2 (orange) are labeled. Electron density map is contoured at 1σ, omit maps at 2.5σ. (D) Electron density around the two central Chl of the reaction center, helices d and cd of subunits D1 (yellow) and D2 (orange) are labeled; Chl are shown in pink with the central Mg2+ ions as gray spheres, 2mFo-DFc, electron density is contoured at 0.8σ, the omit maps at ± 2.5σ.

Jan Kern, et al. Proc Natl Acad Sci U S A. 2012 June 19;109(25):9721-9726.

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