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Spectroscopy and reactivity of pheno...

Pratt, Russell.

Spectroscopy and reactivity of phenolate- and phenoxyl-copper(II) complexes relevant to the enzyme galactose oxidase.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Spectroscopy and reactivity of phenolate- and phenoxyl-copper(II) complexes relevant to the enzyme galactose oxidase.
作者:	Pratt, Russell.
面頁冊數:	131 p.
附註:	Adviser: T. Daniel P. Stack.
附註:	Source: Dissertation Abstracts International, Volume: 65-09, Section: B, page: 4568.
Contained By:	Dissertation Abstracts International65-09B.
標題:	Chemistry, Inorganic.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3145599
ISBN:	0496045970

Spectroscopy and reactivity of phenolate- and phenoxyl-copper(II) complexes relevant to the enzyme galactose oxidase.
Pratt, Russell.

Spectroscopy and reactivity of phenolate- and phenoxyl-copper(II) complexes relevant to the enzyme galactose oxidase. - 131 p.

Adviser: T. Daniel P. Stack.

Thesis (Ph.D.)--Stanford University, 2004.

Structural, spectroscopic and mechanistic studies have shown that the active site of the enzyme galactose oxidase contains a single copper ion and a cysteine-linked tyrosine residue; these cofactors couple the two-electron, two-proton oxidation of alcohols to aldehydes and reduction of dioxygen to hydrogen peroxide by oscillating between copper(II)-tyrosyl radical and copper(I)-tyrosine oxidation states. Models of galactose oxidase have been constructed by complexation of copper(II) with ligands derived from condensation of trans-1,2-diaminocyclohexane with salicylaldehydes. The model complexes undergo ligand-based oxidation centered on the phenolate moieties to form phenoxyl-copper(II) complexes that can be stabilized by proper choice of substituents and conditions. The phenoxyl and phenolate portions of the model complex form a mixed-valence system, and intervalence charge transfer gives rise to a characteristic near-infrared absorption. The energies of the intervalence charge transfer band are altered by including heteroatom substituents on the phenolate rings in imitation of the cross-linked cysteine or by incorporating two different phenolates into the ligand. When correlations that emerge from these small-molecule studies are extended to galactose oxidase itself, they corroborate partial assignment of a visible-near-infrared absorption of its oxidized, copper(II)-tyrosyl radical form to tyrosyl-tyrosinate intervalence charge transfer.

ISBN: 0496045970Subjects--Topical Terms:

197298
Chemistry, Inorganic.

Spectroscopy and reactivity of phenolate- and phenoxyl-copper(II) complexes relevant to the enzyme galactose oxidase.
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245 1 0 $a Spectroscopy and reactivity of phenolate- and phenoxyl-copper(II) complexes relevant to the enzyme galactose oxidase.
300 $a 131 p.
500 $a Adviser: T. Daniel P. Stack.
500 $a Source: Dissertation Abstracts International, Volume: 65-09, Section: B, page: 4568.
502 $a Thesis (Ph.D.)--Stanford University, 2004.
520 # $a Structural, spectroscopic and mechanistic studies have shown that the active site of the enzyme galactose oxidase contains a single copper ion and a cysteine-linked tyrosine residue; these cofactors couple the two-electron, two-proton oxidation of alcohols to aldehydes and reduction of dioxygen to hydrogen peroxide by oscillating between copper(II)-tyrosyl radical and copper(I)-tyrosine oxidation states. Models of galactose oxidase have been constructed by complexation of copper(II) with ligands derived from condensation of trans-1,2-diaminocyclohexane with salicylaldehydes. The model complexes undergo ligand-based oxidation centered on the phenolate moieties to form phenoxyl-copper(II) complexes that can be stabilized by proper choice of substituents and conditions. The phenoxyl and phenolate portions of the model complex form a mixed-valence system, and intervalence charge transfer gives rise to a characteristic near-infrared absorption. The energies of the intervalence charge transfer band are altered by including heteroatom substituents on the phenolate rings in imitation of the cross-linked cysteine or by incorporating two different phenolates into the ligand. When correlations that emerge from these small-molecule studies are extended to galactose oxidase itself, they corroborate partial assignment of a visible-near-infrared absorption of its oxidized, copper(II)-tyrosyl radical form to tyrosyl-tyrosinate intervalence charge transfer.
520 # $a The reactions of two representative copper(II)-phenoxyl complexes with benzyl alcohol and 9,10-dihydroanthracene have been studied. Faster reaction rates with the latter substrate which contains weaker C-H bonds and large H/D kinetic isotope effects indicate a hydrogen atom abstraction mechanism. Some of the reactions show kinetic evidence for a substrate-binding equilibrium that accelerates the reaction. However, the model complexes' reactivity is limited by an inability to use the oxidizing equivalent of the copper(II) ion, which prevents completion of a putative catalytic cycle. To circumvent this limitation, a bis(phenolate) ligand including ligating thioethers intended to stabilize copper(I) has been synthesized. Solvent adducts of the copper(II) complex demonstrate canonical forms of the EPR spectrum for an S = 1/2 system, prompting their structural characterization and computational studies. Copper(II)-phenoxyl and copper(I) forms of this new complex are observable in electrochemical experiments but have yet to be isolated or characterized.
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