Oxidative Cleavage of Cellobiose by Lytic Polysaccharide Monooxygenase (LPMO)-Inspired Copper Complexes
(2019) In ACS Omega 4(6). p.10729-10740- 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... (More)
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(μ-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.
(Less)
- author
- organization
- publishing date
- 2019
- type
- Contribution to journal
- publication status
- published
- subject
- in
- ACS Omega
- volume
- 4
- issue
- 6
- pages
- 12 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- pmid:31460171
- scopus:85067701259
- ISSN
- 2470-1343
- DOI
- 10.1021/acsomega.9b00785
- language
- English
- LU publication?
- yes
- id
- 8674d777-3b64-4dd6-b52a-9da44cf4e795
- date added to LUP
- 2019-07-04 16:47:12
- date last changed
- 2024-03-03 19:51:34
@article{8674d777-3b64-4dd6-b52a-9da44cf4e795,
abstract = {{<p>The potentially tridentate ligand bis[(1-methyl-2-benzimidazolyl)ethyl]amine (2BB) was employed to prepare copper complexes [(2BB)Cu<sup>I</sup>]OTf and [(2BB)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 [(2BB)Cu<sup>I</sup>]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)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>](OTf)<sub>2</sub> indicates that [(2BB)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup> is the main species from pH 4 to 7.5; above pH 7.5, the hydroxo-bridged species [{(2BB)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>x</sub>}<sub>2</sub>(μ-OH)<sub>2</sub>]<sup>2+</sup> 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)Cu<sup>I</sup>]OTf and [(2BB)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>](OTf)<sub>2</sub> 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)Cu<sup>I</sup>]OTf/O<sub>2</sub> or [(2BB)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>](OTf)<sub>2</sub>/H<sub>2</sub>O<sub>2</sub>/NEt<sub>3</sub> 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)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>](OTf)<sub>2</sub>/H<sub>2</sub>O<sub>2</sub>/NEt<sub>3</sub> results in more extensive cellobiose degradation. Likewise, the use of both [(2BB)Cu<sup>I</sup>]OTf and [(2BB)Cu<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>](OTf)<sub>2</sub> with KO<sub>2</sub> afforded cellobiose oxidation products. In all cases, a common Cu(II) complex formulated as [(2BB)Cu<sup>II</sup>(OH)(H<sub>2</sub>O)]<sup>+</sup> was detected by mass spectrometry as the final form of the complex.</p>}},
author = {{Neira, Andrea C. and Martínez-Alanis, Paulina R. and Aullón, Gabriel and Flores-Alamo, Marcos and Zerón, Paulino and Company, Anna and Chen, Juan and Kasper, Johann B. and Browne, Wesley R. and Nordlander, Ebbe and Castillo, Ivan}},
issn = {{2470-1343}},
language = {{eng}},
number = {{6}},
pages = {{10729--10740}},
publisher = {{The American Chemical Society (ACS)}},
series = {{ACS Omega}},
title = {{Oxidative Cleavage of Cellobiose by Lytic Polysaccharide Monooxygenase (LPMO)-Inspired Copper Complexes}},
url = {{http://dx.doi.org/10.1021/acsomega.9b00785}},
doi = {{10.1021/acsomega.9b00785}},
volume = {{4}},
year = {{2019}},
}