| Abstract
| - Low temperature (4.2 K) absorption and hole-burned spectra are presented for the trimeric (wild-type, WT)photosystem I complex of the cyanobacterium Synechocystis sp. PCC 6803, its monomeric form, and mutantsdeficient in the PsaF, K, L, and M protein subunits. High-pressure- and Stark-hole-burning data for the WTtrimer are presented as well as its temperature-dependent Qy-absorption and -fluorescence spectra. Taken asa whole, the data lead to assignment of a new and lowest energy antenna Qy-state located at 714 nm at lowtemperatures. It is this state that is responsible for the fluorescence in the low-temperature limit and not thepreviously identified antenna Qy-state near 708 nm. The data indicate that the 714 nm state is associated withstrongly coupled chlorophyll a molecules (perhaps a dimer) and possesses significant charge transfer character.The red chlorophylls absorbing at 708 and 714 nm do not appear to be directly bound to any of the aboveprotein subunits. The results are consistent with a location close to the interfacial regions between PsaL andM and the PsaA/B heterodimeric core. It is likely that the red chlorophylls are bound to PsaA and/or PsaB.
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