Energy migration in purple bacteria. The criterion for discrimination between migration- and trapping-limited photosynthetic units

A criterion has been evolved for distinguishing between migration- and trapping-limited photosynthetic units (PSUs). Its application to purple bacteria has proved their PSUs to be of trapping-limited type. It means that any improvements of the molecular structure of their PSUs cannot noticeably increase the overall rate constant of excitation delivery from antenna BChls to reaction centers (RCs).Abbreviations PSUs photosynthetic units - RCs reaction centers - Chl chlorophyll - BChl bacteriochlorophyll - R intermolecular distance, _e - quantum yields of the primary excitation trapping and wasteful losses respectively - _fl excitation and fluorescence lifetimes respectively