Biomaterial Database

Time-resolved fluorescence and absorption spectroscopy of photosystem I. 1994

G Hastings, and F A Kleinherenbrink, and S Lin, and R E Blankenship

Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604.

Picosecond fluorescence and femtosecond transient absorption spectroscopy have been used to investigate the primary energy transfer and trapping processes in a photosystem II deletion mutant from the cyanobacterium Synechocystis sp. PCC 6803, which contains active photosystem I reaction centers with approximately 100 chlorophylls per P700. In all experiments, low levels of excitation were used which avoid annihilation processes. Following 590-nm excitation, at room temperature, spectral equilibration is observed in both fluorescence and absorption measurements and is characterized by a time constant of 4-6 ps. The shape of the spectra associated with the equilibration process indicates that long wavelength pigments (pigments with absorption maxima at longer wavelength than that of the primary electron donor, P700) are present and functional at physiological temperatures in this preparation. The overall decay of excitations in the antenna is characterized by a time constant of 24-28 ps, in both fluorescence and absorption measurements. The 24-28-ps process results in the appearance of absorption changes associated with only P700+ formation. Absorption changes associated with the reduction of the primary electron acceptor were not resolved under the experimental conditions used here.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D010777	Photochemistry	A branch of physical chemistry which studies chemical reactions, isomerization and physical behavior that may occur under the influence of visible and/or ultraviolet light.	Photochemistries
D002734	Chlorophyll	Porphyrin derivatives containing magnesium that act to convert light energy in photosynthetic organisms.	Phyllobilins,Chlorophyll 740
D004735	Energy Transfer	The transfer of energy of a given form among different scales of motion. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed). It includes the transfer of kinetic energy and the transfer of chemical energy. The transfer of chemical energy from one molecule to another depends on proximity of molecules so it is often used as in techniques to measure distance such as the use of FORSTER RESONANCE ENERGY TRANSFER.	Transfer, Energy
D000458	Cyanobacteria	A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.	Algae, Blue-Green,Blue-Green Bacteria,Cyanophyceae,Algae, Blue Green,Bacteria, Blue Green,Bacteria, Blue-Green,Blue Green Algae,Blue Green Bacteria,Blue-Green Algae
D013050	Spectrometry, Fluorescence	Measurement of the intensity and quality of fluorescence.	Fluorescence Spectrophotometry,Fluorescence Spectroscopy,Spectrofluorometry,Fluorescence Spectrometry,Spectrophotometry, Fluorescence,Spectroscopy, Fluorescence
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D013997	Time Factors	Elements of limited time intervals, contributing to particular results or situations.	Time Series,Factor, Time,Time Factor
D045322	Photosynthetic Reaction Center Complex Proteins	Protein complexes that take part in the process of PHOTOSYNTHESIS. They are located within the THYLAKOID MEMBRANES of plant CHLOROPLASTS and a variety of structures in more primitive organisms. There are two major complexes involved in the photosynthetic process called PHOTOSYSTEM I and PHOTOSYSTEM II.	Photosynthetic Complex,Photosynthetic Reaction Center,Photosynthetic Reaction Center Complex Protein,Photosynthetic Complexes,Photosynthetic Reaction Centers,Center, Photosynthetic Reaction,Complex, Photosynthetic,Complexes, Photosynthetic,Reaction Center, Photosynthetic,Reaction Centers, Photosynthetic