May read this article; Bacteriopheophytin g: Properties and Some Speculations on a Possible Primary Role for Bacteriochlorophylls b and g in the Biosynthesis of Chlorophylls
June 1987Proceedings of the National Academy of Sciences 84(9):2570-4
Check out this link too; The Effect of Bacteriochlorophyll g Oxidation on Energy and Electron Transfer in Reaction Centers from Heliobacterium modesticaldum.