Institution: | a School of Biological Sciences, Macquarie University, North Ryde, N.S.W. 2013, Australia b CSIRO, Division of Plant Industry, P.O. Box 1600, Canberra City, A.C.T. 2601, Australia |
Abstract: | Acrocarpia paniculata thylakoids were fragmented with Triton X-100 and the pigment-protein complexes so released were isolated by sucrose density gradient centrifugation. Three main chlorophyll-carotenoid-protein complexes with distinct pigment compositions were isolated. 1. (1) A P-700-chlorophyll a-protein complex, with a ratio of 1 P-700: 38 chlorophyll a: 4 ta-carotene molecules, had similar absorption and fluorescence characteristics to the chlorophyll-protein complex 1 isolated with Triton X-100 from higher plants, green algae and Ecklonia radiata. 2. (2) An orange-brown complex had a chlorophyll a : c2 : fucoxanthin molar ratio of 2 : 1 : 2. This complex had no chlorophyll c1 and contained most of the fucoxanthin present in the chloroplasts. This pigment complex is postulated to be the main light-harvesting complex of brown seaweeds. 3. (3) A green complex had a chlorophyll a : c1 : c2 : violaxanthin molar ratio of 8 : 1 : 1 : 1. This also is a light-harvesting complex.
The absorption and fluorescence spectral characteristics and other physical properties were consistent with the pigments of these three major complexes being bound to protein. Differential extraction of brown algal thylakoids with Triton X-100 showed that a chlorophyll c2-fucoxanthin-protein complex was a minor pigment complex of these thylakoids. |