Spectroscopic studies of two spectral variants of light-harvesting complex 2 (LH2) from the photosynthetic purple sulfur bacterium Allochromatium vinosum. 2012

Dariusz M Niedzwiedzki, and David Bina, and Nichola Picken, and Suvi Honkanen, and Robert E Blankenship, and Dewey Holten, and Richard J Cogdell
Photosynthetic Antenna Research Center, Washington University, St Louis, MO, USA. niedzwiedzki@wustl.edu

Two spectral forms of the peripheral light-harvesting complex (LH2) from the purple sulfur photosynthetic bacterium Allochromatium vinosum were purified and their photophysical properties characterized. The complexes contain bacteriochlorophyll a (BChl a) and multiple species of carotenoids. The composition of carotenoids depends on the light conditions applied during growth of the cultures. In addition, LH2 grown under high light has a noticeable split of the B800 absorption band. The influence of the change of carotenoid distribution as well as the spectral change of the excitonic absorption of the bacteriochlorophylls on the light-harvesting ability was studied using steady-state absorption, fluorescence and femtosecond time-resolved absorption at 77K. The results demonstrate that the change of the distribution of the carotenoids when cells were grown at low light adapts the absorptive properties of the complex to the light conditions and maintains maximum photon-capture performance. In addition, an explanation for the origin of the enigmatic split of the B800 absorption band is provided. This spectral splitting is also observed in LH2 complexes from other photosynthetic sulfur purple bacterial species. According to results obtained from transient absorption spectroscopy, the B800 band split originates from two spectral forms of the associated BChl a monomeric molecules bound within the same complex.

UI MeSH Term Description Entries
D010788 Photosynthesis The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001) Calvin Cycle,Calvin-Benson Cycle,Calvin-Benson-Bassham Cycle,Carbon Fixation, Photosynthetic,Reductive Pentose Phosphate Cycle,Dark Reactions of Photosynthesis,Calvin Benson Bassham Cycle,Calvin Benson Cycle,Cycle, Calvin,Cycle, Calvin-Benson,Cycle, Calvin-Benson-Bassham,Photosynthesis Dark Reaction,Photosynthesis Dark Reactions,Photosynthetic Carbon Fixation
D002338 Carotenoids The general name for a group of fat-soluble pigments found in green, yellow, and leafy vegetables, and yellow fruits. They are aliphatic hydrocarbons containing 4 terpene subunits. Carotenes,Carotenoid,Tetraterpene Derivatives,Tetraterpenes,Carotene,Derivatives, Tetraterpene
D002841 Chromatiaceae A family of phototrophic purple sulfur bacteria that deposit globules of elemental sulfur inside their cells. They are found in diverse aquatic environments. Bacteria, Purple Sulfur,Purple Sulfur Bacteria
D001426 Bacterial Proteins Proteins found in any species of bacterium. Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial
D013057 Spectrum Analysis The measurement of the amplitude of the components of a complex waveform throughout the frequency range of the waveform. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Spectroscopy,Analysis, Spectrum,Spectrometry
D045342 Light-Harvesting Protein Complexes Complexes containing CHLOROPHYLL and other photosensitive molecules. They serve to capture energy in the form of PHOTONS and are generally found as components of the PHOTOSYSTEM I PROTEIN COMPLEX or the PHOTOSYSTEM II PROTEIN COMPLEX. Antenna Complexes, Light-Harvesting,Light-Harvesting Antenna Complexes,Light-Harvesting Chlorophyll Protein,Light-Harvesting Chlorophyll Protein Complexes,Antenna Complexes, Light Harvesting,Chlorophyll Protein, Light-Harvesting,Complexes, Light-Harvesting Antenna,Complexes, Light-Harvesting Protein,Light Harvesting Antenna Complexes,Light Harvesting Chlorophyll Protein,Light Harvesting Chlorophyll Protein Complexes,Light Harvesting Protein Complexes,Protein Complexes, Light-Harvesting

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