Photoinduced electron transfer across fixed distances in chlorophyll donor-acceptor molecules

Conference · Mon Jun 01 04:00:00 EDT 1987

OSTI ID:6523813

Wasielewski, M R; Johnson, D G; Svec, W A

The primary events of photosynthesis are a series of rapid, unidirectional electron transfer events between donors and acceptors that are positioned in the reaction center protein at precise spatial orientations and distances relative to one another. Recent work suggests that electron transfer rates depend on distance and free energy of reaction in porphyrin-quinone models in which the distance and orientation of the donor relative to the acceptor is highly restricted. Spacer molecules were developed which were used to link chlorophyll donors with either chlorophyll or quinone acceptors to produce models in which the donor-acceptor distance is well-defined. Recent theoretical studies and photochemical hole-burning experiments have suggested that the actual primary event of photosynthesis is the production of an intramolecular charge transfer state involving the two bacteriochlorophyll molecules of the special pair dimer. This possibility was explored with symmetric, fixed distance chlorophyll dimer. The chlorophyll macrocycles share a common vinyl group at the 2-position. This linkage serves to increase the degree of electronic coupling between the macrocycles. This dimer exhibits a remarkable decrease in fluorescence quantum yield as the dielectric constant of the medium in which it is dissolved increases. This decrease is accompanied by a proportional decrease in the lowest excited singlet state lifetime as measured by picosecond fluorescence and absorption. 11 refs., 2 figs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6523813
• Report Number(s): CONF-870666-1; ON: DE87011442
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
550200 -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
CARBOXYLIC ACIDS
CHLOROPHYLL
CHLOROPHYLL-BINDING PROTEINS
DIMERS
ELECTRON TRANSFER
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
KINETICS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOSYNTHETIC REACTION CENTERS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
STRUCTURE-ACTIVITY RELATIONSHIPS