Fig. 2: Assignment of the FeS cluster EPR signals to the structure of T. elongatus PS-CI using DEER spectroscopy.
From: Functional basis of electron transport within photosynthetic complex I
a Continuous-wave EPR spectra (15 K) of the FeS clusters in sodium dithionite reduced PS-CI (Photosynthetic complex I) of Synechocystis (blue) and T. elongatus (black), 2 mW, 100 kHz modulation frequency, 7 G modulation amplitude. Simulations of the total (red) and individual N2 (pink), N1 (purple) and N0 (grey): Synechocystis g values: N2 (gx,y = 1.922, gz = 2.055), N1 (gx = 1.886, gy = 1.927, gz = 2.043), N0 (gx = 1.851, gy = 1.867, gz = 2.079); T. elongatus g values: N2 (gx,y = 1.922, gz = 2.055), N1 (gx = 1.907, gy = 1.913, gz = 2.045), N0 (gx = 1.852, gy = 1.899, gz = 2.064); See Supplementary Table 3 for full simulation parameters. b Set up of the pump pulse positions (red) and detection pulse position (black) for the corresponding DEER traces (for full experimental set up see Fig. S3) (10 K). Echo-detected field sweep of T. elongatus (black), the sum of simulations (red), N2 (pink), N1 (purple), N0 (grey) (N2:N1:N0 ratio 1.00:0.92:0.90); see Table S3 for simulation parameters. c, d T. elongatus orientation-selective DEER traces for the corresponding pump and probe positions (black) (10 K). The modulation depth is indicated as a scale bar. c Best-fit simulated DEER traces for model A, with the N1 cluster at 26.1 Å from N2 (red). d Best-fit simulated DEER traces for model B, with N0 at 26.1 Å from N2 (blue). Schematics of the structural models are shown below. Note that the shorter distances (i.e. dipolar coupling to the middle cluster) do not contribute to the DEER traces; see Supplementary Note 2 for details on the simulation of the DEER traces and models employed. See Fig. S4 for a complete set of the DEER traces and simulations.
