Decline in bacteriochlorophyll fluorescence induced by carotenoid absorption

Abstract

A marked decline in the fluorescence of bacteriochlorophyll from chromatophores of purple bacteria occurs when high intensity incident light of a wavelength absorbed by carotenoids is used for excitation. Intact bacteria show the same effect at temperatures below −20°. The fluorescence capacity is restored in the dark at temperatures higher than about −40°. At liquid N2 temperature the decline in fluorescence is not reversible in the dark.

Absorption in the weak 800-nm bacteriochlorophyll band of Rhodospirillum rubrum was also found to be effective in producing the above effect.