Before revision:  a mechanism to prevent damage from excess sunlight, an advantage of the dimeric form, a reason that the cross section of the light harvestor must not be circular, a reason for the modular design of nature , a function of the non-heme iron at the reaction center, and a reason that the light harvestor must not be spherical . Based upon our analysis we provide a mechanism for dimerization and propose an experiment .
After revision:  a mechanism to prevent damage from excess sunlight, an advantage of the dimeric form, a reason that the cross section of the light harvestor must not be circular, a reason for the modular design of nature , a function of the non-heme iron at the reaction center, and a reason that the light harvestor must not be spherical . Based upon our analysis we provide a mechanism for dimerization .