Chemical and biosynthetic studies of chlorophylls
Chlorophyll occurrence, structure, biosynthesis, and degradation are discussed. Degradation and ring cleavage of heme is also discussed. The author examines the formation of dihydrobiliverdins by alkaline hydrolysis of zinc(II) meso-trifluoroacetoxypheophoribides, as a possible model for chlorophyll catabolism. {sup 18}O{sub 2}-labelling experiments show that the dihydrobiliverdin terminal lactam oxygens are derived from two different dioxygen molecules, also analogous to the Two Oxygen Molecular mechanism observed in heme degradation. The initially obtained dihydrobiliverdin readily undergoes an isomeric structural transformation, which is proposed as a model for the P{sub R}-P{sub FR} interconversion of the light sensor pigment phytochrome. The generality of the ring-opening reaction is demonstrated with various chlorophyll-derived zinc(II) trifluoroacetoxychlorins, and side reactions of the isocyclic ring are discussed. The synthesis and properties of a chlorophyll-derived meso-oxochlorin are described. Facile one-electron oxidation, and its inhibition by protonation, is demonstrated by NMR, ESR, and cyclic voltammetry studies. Cyclic voltammetry is also used to measure redox potentials of a range of pheophorbide and meso-trifluoroacetoxypheophorbide metal complexes, including an oxochlorin nickel(II) complex. The results are presented of biosynthetic feeding studies of green sulfur bacteria with {sup 13}C- and {sup 14}C-labelled glutamate, glycine, and methionine. This study examines an unusual oxidation of a bacteriomethylpheophorbide 5-ethyl substituent, and describes attempts to elucidate the mechanism by {sup 18}O-labelling studies. Attempts to similarily derivatize a pyropheophorbide 5-methyl substituent are discussed.
- Research Organization:
- California Univ., Davis, CA (USA)
- OSTI ID:
- 6983944
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHLOROPHYLL
BIOCHEMISTRY
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBON 13
CARBON 14 COMPOUNDS
CHEMICAL COMPOSITION
ELECTRON SPIN RESONANCE
GLUTAMIC ACID
GLYCINE
METABOLISM
METHIONINE
MOLECULAR STRUCTURE
NMR SPECTRA
OXYGEN 18
REDOX POTENTIAL
TRACER TECHNIQUES
AMINO ACIDS
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMISTRY
DRUGS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN ISOTOPES
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
RESONANCE
SPECTRA
STABLE ISOTOPES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques