Photosynthetic light-harvesting: Reconciling dynamics and structure of purple bacterial LH2 reveals function of photosynthetic unit

Great progress in the study of structure and dynamics of photosynthetic lig ht-harvesting pigment-protein complexes has recently resulted in detailed u nderstanding of the light-harvesting and light-conversion processes of phot osynthesis. We review and discuss recent results on the elementary excitati on transfer dynamics of the purple bacterial LH2 peripheral complex. When c ombining the information from the two LH2 structures that are now available with the experimental results obtained from steady-state spectroscopy, a v ariety of ultrafast techniques and computer simulations, a detailed underst anding of the LH2 function is obtained. Dynamics relevant to the complete p hotosynthetic unit (PSU = LH2 + LH1 core + reaction center), as well as mod els of the PSU obtained on the basis of the LH2 structure, allow us to sugg est how the characteristic structural features of LH2 and LH1 have been des igned to optimize the overall light-harvesting and trapping process in the PSU.