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Oxidative Cleavage of Cellobiose by Lytic Polysaccharide Monooxygenase (LPMO)-Inspired Copper Complexes.


ABSTRACT: The potentially tridentate ligand bis[(1-methyl-2-benzimidazolyl)ethyl]amine (2BB) was employed to prepare copper complexes [(2BB)CuI]OTf and [(2BB)CuII(H2O)2](OTf)2 as bioinspired models of lytic polysaccharide copper-dependent monooxygenase (LPMO) enzymes. Solid-state characterization of [(2BB)CuI]OTf revealed a Cu(I) center with a T-shaped coordination environment and metric parameters in the range of those observed in reduced LPMOs. Solution characterization of [(2BB)CuII(H2O)2](OTf)2 indicates that [(2BB)CuII(H2O)2]2+ is the main species from pH 4 to 7.5; above pH 7.5, the hydroxo-bridged species [{(2BB)CuII(H2O) x }2(?-OH)2]2+ is also present, on the basis of cyclic voltammetry and mass spectrometry. These observations imply that deprotonation of the central amine of Cu(II)-coordinated 2BB is precluded, and by extension, amine deprotonation in the histidine brace of LPMOs appears unlikely at neutral pH. The complexes [(2BB)CuI]OTf and [(2BB)CuII(H2O)2](OTf)2 act as precursors for the oxidative degradation of cellobiose as a cellulose model substrate. Spectroscopic and reactivity studies indicate that a dicopper(II) side-on peroxide complex generated from [(2BB)CuI]OTf/O2 or [(2BB)CuII(H2O)2](OTf)2/H2O2/NEt3 oxidizes cellobiose both in acetonitrile and aqueous phosphate buffer solutions, as evidenced from product analysis by high-performance liquid chromatography-mass spectrometry. The mixture of [(2BB)CuII(H2O)2](OTf)2/H2O2/NEt3 results in more extensive cellobiose degradation. Likewise, the use of both [(2BB)CuI]OTf and [(2BB)CuII(H2O)2](OTf)2 with KO2 afforded cellobiose oxidation products. In all cases, a common Cu(II) complex formulated as [(2BB)CuII(OH)(H2O)]+ was detected by mass spectrometry as the final form of the complex.

SUBMITTER: Neira AC 

PROVIDER: S-EPMC6648734 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Oxidative Cleavage of Cellobiose by Lytic Polysaccharide Monooxygenase (LPMO)-Inspired Copper Complexes.

Neira Andrea C AC   Martínez-Alanis Paulina R PR   Aullón Gabriel G   Flores-Alamo Marcos M   Zerón Paulino P   Company Anna A   Chen Juan J   Kasper Johann B JB   Browne Wesley R WR   Nordlander Ebbe E   Castillo Ivan I  

ACS omega 20190620 6


The potentially tridentate ligand bis[(1-methyl-2-benzimidazolyl)ethyl]amine (<b>2BB</b>) was employed to prepare copper complexes [(<b>2BB</b>)Cu<sup>I</sup>]OTf and [(<b>2BB</b>)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>](OTf)<sub>2</sub> as bioinspired models of lytic polysaccharide copper-dependent monooxygenase (LPMO) enzymes. Solid-state characterization of [(<b>2BB</b>)Cu<sup>I</sup>]OTf revealed a Cu(I) center with a T-shaped coordination environment and metric parameters in the range o  ...[more]

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