Theoretical studies of photosynthesis
The conversion of light energy to chemical energy by the process of photosynthetic charge separation is one of the most important chemical transformation for life on this planet. With the atomic level structures of photosynthetic reaction centers (RC) for some bacteria now known, one can attempt to attain a more complete understanding of the properties and mechanisms of these systems. In this dissertation theoretical studies on both monomeric bacteriochlorophylls (BChl) and aggregates of these related pigments representing models of the RC are presented. Models for the effects of nearby charged and polar groups on monomeric BChls and how these relate to spectroscopic shifts in the absorption spectrum of the RC are discussed. The calculated properties of the BChl dimer or special pair is best described in terms of a dimer of strongly interacting BChl monomers rather than the more traditional coupled chromophore model. That this BChl dimer is responsible for the lowest absorption band in the UV/vis spectrum of RCs is well described by these results. A description of these interactions in the BChl dimer is presented using a simpler model system composed of Mg-bacteriochlorin dimers. A model of the RC consisting of the four BChlbs and two bacteriopheophytins as well as some of the surrounding amino acids of the RC protein is sufficient to give a reasonable description of the calculated UV/vis spectrum of the RC. These results show that the lowest two excited states of the RC are attributed to the BChl dimer. This strengthens the identification of the second lowest excited state with the shoulder seen at 850 nm in experimental spectra as the upper exciton-like component of the BChl dimer. Charge transfer (CT) states are calculated and demonstrate the preference for flow of charge in the RC along only one of its branches.
- Research Organization:
- Florida Univ., Gainesville, FL (United States)
- OSTI ID:
- 6089103
- Resource Relation:
- Other Information: Thesis (Ph.D)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
PHOTOSYNTHESIS
CHEMICAL REACTION KINETICS
ABSORPTION
CHARGE TRANSPORT
CHEMICAL PROPERTIES
CHLOROPHYLL
DIMERS
MOLECULAR MODELS
SOLAR RADIATION
ULTRAVIOLET RADIATION
VISIBLE RADIATION
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
ELECTROMAGNETIC RADIATION
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
KINETICS
MATHEMATICAL MODELS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
RADIATIONS
REACTION KINETICS
STELLAR RADIATION
SYNTHESIS
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)