Chlorophyll‐protein complexes of barley photosystem I

Photosystem I (PSI) preparations with a chlorophyll a/b ratio of 6.0 were isolated from barley thylakoids using two different methods. The high‐molecular‐mass complex (CP1a*) which is resolved by non‐denaturing gel electrophoresis had the same properties as a PSI preparation (PSI‐200) isolated by Triton X‐100 solubilisation of thylakoids followed by sucrose gradient ultracentrifugation. This material had a chlorophyll:P700 ratio of 208:1 and was composed of three different chlorophyll‐protein complexes which could be separated from each other by solubilising the PSI preparation in dodecyl maltoside followed by sucrose gradient ultracentrifugation. Approximately half of the chlorophyll, including all the chlorophyll b, was located in two antenna complexes designated LHCI‐680 and LHCI‐730, which were identified by their characteristic low‐temperature fluorescence emission spectra. The rest of the chlorophyll a was associated with the PSI reaction centre, P700 Chla‐P1, which fluoresced at 720 nm. Each chlorophyll‐protein complex had a unique polypeptide composition and characteristic circular dichroic and absorption spectra. The use of dodecyl maltoside instead of dodecyl sulphate res