Figure 5.

The upper part of the electron transfer chain in PS I. ( a) Upper B branch of the electron transfer pathway modeled into 2F_obs− F_calc electron density contoured to 2 $\sigma$. Also shown are the aromatic amino acids PsaB-Trp673 and PsaB-Phe669 in proximity to the phylloquinone. The plane of Trp673 has twisted 15° relative to the cryogenic structure (inset). (b) Stick representation of the upper A and B branches of the reaction center including the [4Fe4S] cluster F_X and the phylloquinones PhQ_A and PhQ_B. The distance of PhQ_A to the symmetry breaking PsaB-Trp673 is with 7 Å in the room temperature structure longer than the 6.6 Å in the cryo structure. The distance between F_X and the quinones is not altered. Figure generated with Pymol v. 2.4.0a0. https://pymol.org.