Copper Catalyzed Lipid Polysaccharide Monooxygenase Biomimicry of Polysaccharide Oxidative Cleavage Restricted; Files Only
Pandey, Ritika (Spring 2024)
Published
Abstract
Lipid polysaccharide monooxygenases (LPMO) can degrade glycosidic bonds via oxidative cleavage using ascorbate reagents in a redox system with a debated mechanism, and copper complex mimetics display similar capabilities with more room for optimization. This work investigates four copper complex mimetics of LPMO designed with N, N, N or N, N, O coordination spheres in terms of glycosidic cleavage capability. This work investigates their reactivity towards model substrates of cellulose and gain insight into the mechanism via reactive intermediates. It demonstrates a novel ligand-centered radical reactive capability of a proline-derived ligand on a copper complex mimetic with oxidative glycosidic capability. One copper complex LPMO mimetic was synthesized with desired reactive properties, and its abilities in oxidative cleavage using peroxide as well as ascorbic/dioxygen reagent conditions were demonstrated using 4-nitrophenyl-β-D-glucopyranoside and cellobiose as substrates. Numerous reactions to probe the mechanism revealed the reactivity of ligand-centered radicals from proline-derived ligands as central to this glycosidic cleavage capability.
Table of Contents
Chapter 1: An Introduction to Complex 4 and Cellulose Breakdown
1.1 The Energy Crisis
1.1.1 The Challenges of Energy 1
1.1.2 Plant Biomass as an Energy Source 2
1.2 Copper Complex Mimetics 3
1.3 Reaction Overview 5
1.4 Scopes and Aims 6
1.5 References 7
Chapter 2: Oxygen and Ascorbate as Reagents
2.1 Introduction 8
2.2 Methodology
2.2.1 Peroxide as a Reagent 9
2.2.2 Ascorbate as a Reagent 10
2.3 Results and Discussion
2.3.1 Peroxide as a Reagent 11
2.3.2 Ascorbate as a Reagent 14
2.4 References 15
Chapter 3: The Copper Complex
3.1 Introduction 16
3.2 Methodology
3.2.1 Complex 4 Synthesis 19
3.2.2 Evaluation of Different Complexes in LPMO Mimetic Activity 20
3.2.3 Complex 4 Mechanism 20
3.3 Results and Discussion
3.3.1 Complex 4 Synthesis 21
3.3.2 Evaluation of Different Complexes in LPMO Mimetic Activity 22
3.3.3 Complex 4 Mechanism 25
3.4 References 28
Chapter 4: Optimizing Reaction Conditions
4.1 Introduction 29
4.2 Methodology
4.2.1 Reagent Concentrations 29
4.2.2 pH stability 30
4.2.3 Breakdown of Cellobiose 30
4.3 Results and Discussion
4.2.1 Reagent Concentrations 30
4.2.2 pH stability 33
4.2.3 Breakdown of Cellobiose 34
4.4 References 35
Chapter 5: Conclusions and Perspectives 36
List of Figures
Figure 1.1 Energy consumption in the United States 1
Figure 1.2 Corn Production and Fuel Use in the United States 2
Figure 1.3 LPMO Catalytic Site Structure from Panu similis and LPMO glycosidic cleavage reactions. 3
Figure 1.4 LPMO Copper Complex Mimetic 4
Figure 1.5 Complex Characterization 5
Figure 1.6 Reaction Scheme. 6
Figure 2.1 The depiction of the dioxygen intermediate with a binuclear copper active site 9
Figure 2.2 Reaction Scheme for Experiment 10
Figure 2.3 Reaction Scheme for Experiment 11
Figure 2.4 Study of Oxidative Cleavage Rate and the Copper Complexes 12
Figure 2.5 Kinetic Data Comparison of Model Substrate Turnover in Copper Complexes 13
Figure 2.6 Absorbance Characterization of Peroxy Intermediate 14
Figure 2.7 Monooxygenase Activity of Complex 4 With Ascorbate and Oxygen Reagents 15
Figure 3.1 Copper Complexes analyzed for LPMO reactivity 17
Figure 3.2 HRMS of Complex 4 in Water and Methanol 17
Figure 3.3 EPR Evaluation of Radical Forming in Complex 4 19
Figure 3.4 Mass Spectrum of Complex 4 Synthesis 22
Figure 3.5 Study of Influence of Complex Concentration on Catalysis 24
Figure 3.6 Influence of Ascorbate concentration in Catalysis 25
Figure 3.7 Mass Spectrum of Complex4- Peroxy Intermediate with Peroxide Reagent 26
Figure 3.8 Mass Spectrum of Complex4- Peroxy Intermediate with Ascorbate Reagent 27
Figure 3.9 Absorbance Spectrum of Peroxy Intermediate of Complex 4 Using Ascorbate Reagent 28
Figure 4.1 Study of the Influence of Peroxide Concentration on Catalysis 31
Figure 4.2 Evaluation of Different Substrate Concentration on Catalysis 32
Figure 4.3 Study of Influence of pH on Reaction Rate of Complex 4 33
Figure 4.4 Absorbance Spectrum of Complex 4 Reaction with Cellobiose Substrate 34
Figure 4.5 Mass Spectrum of Complex 4 Reaction Oxidative Cleavage 35
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