Movement of unique biological catalytic reactivity to small synthetic molecules, while a formidable challenge, is an extremely intriguing and informative endeavor providing critical insights into the native reactivity. The broad and long-term objective of this research is elucidation of the structural and electronic properties of Cu-O2 species formed in biological mononuclear, binuclear and trinuclear Cu-sites and subsequent characterization of their oxidative reactivity. The methodology is that of the synthetic analog approach to the active sites of metallobiomolecules, whereby low molecular weight complexes are synthesized and examined at a small molecule level of detail to reveal intrinsic properties of the metal complexes uncoupled from the influences of the protein matrix. The premise is that the formation and subsequent reactivity of biological intermediates should be reproducible in small synthetic complexes if appropriate ligation environments are engineered, and if deleterious bimolecular reactions of the reactive intermediates are avoided. Creation of spectroscopically congruent, functional models is the ultimate goal so that specific aspects of proposed biological mechanisms may be investigated at a small molecule level of detail.
The specific aims are as follows: Structural, spectroscopic and reactivity characterization of [Cu(I)LDAL(MeCN)]1+-O2 products using simple peralkylated diamines ligands (LDA) to provide chemical precedence for possible biological intermediates and spectroscopic benchmarks by which such intermediates may be identified. Reactivity characterization of new intermediates may lead to new bio-inspired oxidation catalysts. Defining the mechanistic relationship of catalytically functional galactose oxidase model complexes to the native system. Development of more oxidatively resistant model complexes will aid in the mechanistic and kinetic studies. Integration of histidine terminated peptides into the ligand framework will provide more biologically relevant functional models of galactose oxidase. Functional modeling of the reactivity of mononuclear trigonally-ligated copper sites to investigate the type of environments that promote O2 activation, the type of Cu-O2 intermediates formed, and the mechanism of phenolate group oxidative modification, an emerging theme in mononuclear copper enzymes. Development of a mechanistic relationship between lipoxygenase, a mononuclear iron enzyme, and mononuclear iron models that exhibit oxidation behavior most consistent with CH hydrogen atom abstraction.
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