Abstract
In the photosynthetic membrane, there is a particular aggregated state for the chlorophyll
a
(Chl
a
) molecules with a specific arrangement responsible for the high efficiency of energy conversion. Chl
a
monolayers, transferred onto solid substrates, are systems that potentially can mimic the packing of the
in vivo
system. The association of Chl
a
in the monolayer results in the formation of dimers with an average size of 3.00 ± 0.15 nm. Considering the organization of the dimers, we assume that P680 is a dimer with the (anti) parallel transition moments of the constituent. The Chl
a
macrocycles most likely are tilted to each other by 30° with respect to the membrane plane.
