Fig. 99: a) Schematic representation of the transmembrane -helices of one Photosystem I monomer. Adjoining monomers are partially included, separated by bold, broken lines. The proposed assignment of -helices and the approximate extent of individual subunits are indicated by thin, dotted lines, the stromal subunits by continuous black lines. The region occupied by the chlorophyll a units of the core antenna system is indicated by light grey shading [courtesy of N. Krauss]. b) An equivalent depiction to Figure 99a but looking along the membrane plane (stroma, top; lumen, bottom). The a-helices (light blue) of the stromal subunits are shown in addition to those in Figure 99a [courtesy of N. Krauss].