Boreskov

OP‐8participation of the antenna, which role is played by the other flavin molecule, deazaflavin orpterin. The evolution of these proteins resulted in the formation of the complex of antennaand reaction center which organization is fundamentally different from the photosyntheticapparatus. The difference refers to the structure of pigments, their stoichiometry andrelative ability of the antenna and RC pigments to absorb light. The study of the propertiesof the excited flavin and pterin molecules has revealed some structural features that wereimportant in the process of selection of the chromophores for photoreceptor proteins.Since the flavoprotein photoreceptors from different families are structurally verydistant from each other, we can conclude that the "invasion" of flavins into the mechanismsof reception of light occurred repeatedly in the history of biosphere. We believe that inbiological evolution, there were prerequisites for the formation of the photon energyconverting mechanism based on the chemical activity of excited flavins and able to conservethe photon energy in macroergic phosphoanhydride bonds of ATP. The photoreceptor couldbe complemented with a light harvesting antenna using pteridine or benzopteridinederivatives.The proposed model utilizes the shortwave visible and UV‐A radiation with a mainmaximum in visible areas at 450‐470 nm. Its spectral sensitivity almost ideally correspondsto the spectrum of solar radiation, not distorted by the atmospheric ozone shield, i.e. it isconsistent with the conditions of early Earth. The presence of ozone in actualisticatmosphere shifts the irradiance maximum reaching the planet's surface to longerwavelengths what makes the situation less favorable for flavin‐based photoenergetics. Animportant disadvantage of the flavin model as compared to chlorophyll photosynthesis, is alow photon absorptive capacity. The ε value for the long‐wavelength absorption maximamaxare as = 1,2 10 M cm for FMN and = 5 10 M cm for chlorophyll. Another4504 –1 –16804 –1 –1drawback of flavins as compared with chlorophyll is that the flavin molecule’s absorption isrestricted by the shortwave visible (blue) and ultraviolet areas and even when assisted bythe antenna pigments, flavins cannot utilize photons of the whole range of visible spectrum.Supported by the Program of Basic Research № 25 of the Presidium of Russian Academyof Sciences and Russian Foundation for Basic Research Grant 11‐04‐01007‐а.References[1]. Kolesnikov, M.P., Telegina, T.A., Lyudnikova, T.A., and Kritsky, M.S. (2008) Origins Life Evol. Biosph., 38,243–255.[2]. Kritsky, M.S. Telegina, T.A., Vechtomova, Y.L., Kolesnikov, M.P., Lyudnikova, T.A., Golub, O.A. (2010)Biochemistry (Moscow), 75, 1200‐1216.43