Integrity and activity of photosystem 2 complexes isolated from the thermophilic cyanobacterium Synechococcus elongatus using various detergents

The efficiency in selective extraction of photosystem (PS) 2 oxygen evolvin g complexes was compared among seven detergents. These were applied to thyl akoid membranes of the thermophilic cyanobacterium Synechococcus elongatus, Used were five non-ionic detergents with one ionic and one zwitterionic fo r comparison. To compare the suitability and efficiency of the detergents t he following properties of the extracts were examined: maximum rate of oxyg en evolution with various electron accepters, the relative variable fluores cence (F-V/F-M), the contamination of the extract with photosystem (PS) 1, and the status of the electron acceptor side of PS2 reaction centre, None o f the detergents yielded a highly selective extraction of the PS2 complexes (negligible contamination with PS1) which would simultaneously display a h igh photochemical activity and high structural intactness. Heptylthioglucos ide and dodecylmaltoside yielded the nearest approximation to the optimum r esult. Kinetic fluorometry was applied here for the first time to character ize the functional and structural properties of PS2 particles from cyanobac teria.