Hydrogen atom transfer 1036 INDEX

Density differences (Fig. 7) once more qualitatively show an asynchronous transition state with the Cu-O bond breaking/O-Si bond formation being more advanced compared to the hydrogen transfer toward the Cu atom. Wiberg indexes (Table 7) confirm this asynchronicity, although it being less pronounced compared to the previous steps (Sy = 0.90-0.95). At the TS, the Si-H and Cu-O bonds are broken at approximately 75 and 85 %, while almost 85 % of the Si-O bond has been formed. The Cu-H bond has only been formed up to about 60-65 %. SB ay... 

Figure 2.29. Detail of photosystem I, seen from the side, with the division between units A and B (see Fig. 2.27) in the middle. Chlorophyll molecules (chi) other than the six central ones involved in transfer of energy to the three Fe4S4 clusters (FeS) are omitted. Chlorophylls, phylloquinones (phy, also known as vitamin K) and iron-sulphur clusters are further indexed with the subimit label A, B or X (cf. Fig. 2.27), and the chlorophylls are shown with an index number 1 to 3. Other identified molecules include LHG (CggHygOjoP), LMG (C45H84OJQ) and a number of p-carotenes (BCR). The scattered dots are oxygen atoms of water molecules (no hydrogens are shown). Based on Protein Data Bank ID IJBO Jordan et ah, 2001).

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