High photochemical trapping efficiency in Photosystem I from the red Glade algae Chromera velia and Phaeodactylum tricornuturn

In the present work, we report the first comparative spectroscopic investigation between Photosystem I (PSI) complexes isolated from two red Glade algae. Excitation energy transfer was measured in PSI from Chromera velia, an alga possessing a split PsaA protein, and from the model diatom Phaeodactylum tricornutum. In both cases, the estimated effective photochemical trapping time was in the 15-25 ps range, i.e. twice as fast as higher plants. In contrast to green phototrophs, the trapping time was rather constant across the whole emission spectrum. The weak wavelength dependence was attributed to the limited presence of long-wavelength emitting chlorophylls, as verified by low temperature spectroscopy. As the trapping kinetics of C. velia PSI were barely distinguishable from those of P. tricornutum PSI, it was concluded that the scission of PsaA protein had no significant impact on the overall PSI functionality. In conclusion, the two red Glade algae analysed here, carried amongst the most efficient charge separation so far reported for isolated Photosystems. (C) 2016 Published by Elsevier B.V.