Investigation of molecular mechanisms in photodynamic action and radiobiology with nanosecond flash photolysis and pulse radiolysis. Progress report, July 1, 1976--September 30, 1977
Laser flash photolysis investigations on aromatic amino acids and proteins have demonstrated that monophotonic electron ejection is the major initial act, leading to e/sup -//sub aq/ and the corresponding aromatic radicals, followed by back reactions limited by available e/sup -//sub aq/ scavengers. Results with ribonuclease A, lysozyme and carboxypeptidase A have led to information about the relationship of the photoionization efficiency of aromatic residues to the microenvironment. Measurements on the decay kinetics of photoelectrons have shown that the lifetimes and their dependence on scavenger concentrations and dose are inconsistent with homogeneous reactions. A new theory is proposed in which the photoelectron diffuses through the medium as a quasi-free particle, where original pair-recombination competes with scavenging and pair-pair interactions. This theory is in good agreement with laser flash photolysis studies on I/sup -/, FE(CN)/sub 6//sup 4 -/, tryptophan and tyrosine and consistent with earlier photochemical scavenging measurements. The general analysis of radition sensitivity has been extended to suspensions of large biological targets, such as vesicles, viruses and cells, particularly where the radical diffusion length is smaller than or comparable to the collision radius. The development is exemplified with new work on inactivation of T7 bacteriophag by 25 MeV electrons and photodynamic inactivation of Saccharomyces cerevisiae. Detailed studies on yeast have shown that the sensitivity to singlet oxygen attack depends on the temperature and the culture growth phase. Spin label ESR measurements indicate that he conditions of low photosensitivity parallel low membrane fluidity.
- Research Organization:
- Illinois Inst. of Tech., Chicago (USA)
- OSTI ID:
- 7302961
- Report Number(s):
- COO-2217-21
- Country of Publication:
- United States
- Language:
- English
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Investigation of molecular mechanisms in photodynamic action and radiobiology with nanosecond flash photolysis and pulse radiolysis. Progress report, July 1, 1975--June 30, 1976
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
AZOLES
BACTERIOPHAGES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOMASS
CARBOXYLIC ACIDS
CARBOXYPEPTIDASE
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CRYOGENIC FLUIDS
DECOMPOSITION
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY SOURCES
ENZYMES
FERMIONS
FLUIDS
FUNGI
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROLASES
HYDROXY ACIDS
INDOLES
KINETICS
LEPTONS
MICROORGANISMS
MOLECULAR BIOLOGY
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN
PARASITES
PEPTIDE HYDROLASES
PHOSPHOTRANSFERASES
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOLYSIS
PLANTS
PROTEINS
PULSE TECHNIQUES
PYRROLES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION KINETICS
RENEWABLE ENERGY SOURCES
RNA-ASE
SACCHAROMYCES
SACCHAROMYCES CEREVISIAE
TRANSFERASES
TRYPTOPHAN
TYROSINE
VIRUSES
YEASTS