Preparation of synthetic lignins with superior NMR characteristics via isotopically labeled monolignols

Ralph, John; Zhang, Yingsheng; Ede, Richard M.

doi:10.1039/a803281e

Cited by 10 publications

(6 citation statements)

References 15 publications

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“…40,47, 55 Nevertheless, all the correct coupling and cross-coupling products that are found in lignins are usually produced, just in different ratios. 40,56 To gather the required NMR data, it is not usually necessary to resort to more timeconsuming methods to enhance cross-coupling reactions such as diffusion of monomers through dialysis membranes. 55, 57 Simple in vitro DHP methods were used here to produce poly-mers to allow acquisition of the 1D 13 C-NMR spectra shown in Figs.…”

Section: Dehydrogenation Polymers (Dhps)mentioning

confidence: 99%

NMR analysis of lignins in CAD-deficient plants. Part 1. Incorporation of hydroxycinnamaldehydes and hydroxybenzaldehydes into lignins

et al. 2002

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Peroxidase/H2O2-mediated radical coupling of 4-hydroxycinnamaldehydes produces 8-O-4-, 8-5-, and 8-8-coupled dehydrodimers as has been documented earlier, as well as the 5-5-coupled dehydrodimer. The 8-5-dehydrodimer is however produced kinetically in its cyclic phenylcoumaran form at neutral pH. Synthetic polymers produced from mixtures of hydroxycinnamaldehydes and normal monolignols provide the next level of complexity. Spectral data from dimers, oligomers, and synthetic polymers have allowed a more substantive assignment of aldehyde components in lignins isolated from a CAD-deficient pine mutant and an antisense-CAD-downregulated transgenic tobacco. CAD-deficient pine lignin shows enhanced levels of the typical benzaldehyde and cinnamaldehyde end-groups, along with evidence for two types of 8-O-4-coupled coniferaldehyde units. The CAD-downregulated tobacco also has higher levels of hydroxycinnamaldehyde and hydroxybenzaldehyde (mainly syringaldehyde) incorporation, but the analogous two types of 8-O-4-coupled products are the dominant features. 8-8-Coupled units are also clearly evident. There is clear evidence for coupling of hydroxycinnamaldehydes to each other and then incorporation into the lignin, as well as for the incorporation of hydroxycinnamaldehyde monomers into the growing lignin polymer. Coniferaldehyde and sinapaldehyde (as well as vanillin and syringaldehyde) co-polymerize with the traditional monolignols into lignins and do so at enhanced levels when CAD-deficiency has an impact on the normal monolignol production. The implication is that, particularly in angiosperms, the aldehydes behave like the traditional monolignols and should probably be regarded as authentic lignin monomers in normal and CAD-deficient plants.

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Section: Dehydrogenation Polymers (Dhps)mentioning

confidence: 99%

NMR analysis of lignins in CAD-deficient plants. Part 1. Incorporation of hydroxycinnamaldehydes and hydroxybenzaldehydes into lignins

et al. 2002

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“…2a was prepared by the action of peroxidase and hydrogen peroxide on coniferyl alcohol in which the methoxy was specifically 13 C-depleted and trideuterated (from a previous study). 44…”

Section: Experimental Generalmentioning

confidence: 99%

NMR characterization of lignins from transgenic poplars with suppressed caffeic acid O-methyltransferase activity

Marita

Ralph

Lapierre

et al. 2001

J. Chem. Soc., Perkin Trans. 1

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Perturbing the lignin biosynthetic pathway provides a tool for understanding the complex process of lignification. Caffeic acid O-methyltransferase (COMT) is required to produce syringyl units in lignins. Down-regulating the expression of its gene in poplar dramatically affects the lignin composition. 2D and 3D NMR investigations detail structural differences between lignins from a control and COMT-deficient poplars obtained by means of two independent transformation techniques. This rst application of 3D NMR to natural abundance lignins reveals the full side-chain network and provides diagnostic evidence for the intimate incorporation of 5-hydroxyconiferyl alcohol into the lignins to form novel benzodioxanes as major structures. The flexibility of a plant to utilize novel monomers to produce functional lignins provides opportunities for engineering the structure and affecting the consequent properties of lignins

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“…“End-wise” DHP obtained from the ZT procedure has a larger molar mass and a structure more similar to isolated wood lignin than “bulk” DHP obtained from the ZL procedure. Control of DHP structure has been obtained through the structure and composition of precursors, − polymerization conditions (e.g., pH, − solvent, − and enzyme/monolignol ratio), enzyme type, − the presence of soluble carbohydrates, − isotopic labeling, , and mediators. − Resulting DHPs served as substrates for lignin biodegradation studies via ligninolytic enzymes, enzymes which oxidatively produce reactive species capable of attacking chemical bonds in lignin. − On the other hand, synthesized DHP has lower molar mass and may have a higher proportion of ether linkages (e.g., β-O-4) and end groups than native lignin, , although contradictory studies exist. , …”

Section: Introductionmentioning

confidence: 99%

Surface-Initiated Dehydrogenative Polymerization of Monolignols: A Quartz Crystal Microbalance with Dissipation Monitoring and Atomic Force Microscopy Study

et al. 2013

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This work highlights a real-time and label-free method to monitor the dehydrogenative polymerization of monolignols initiated by horseradish peroxidase (HRP) physically immobilized on surfaces using a quartz crystal microbalance with dissipation monitoring (QCM-D). The dehydrogenative polymer (DHP) films are expected to provide good model substrates for studying ligninolytic enzymes. The HRP was adsorbed onto gold or silica surfaces or onto and within porous desulfated nanocrystalline cellulose films from an aqueous solution. Surface-immobilized HRP retained its activity and selectivity for monolignols as coniferyl and p-coumaryl alcohol underwent dehydrogenative polymerization in the presence of hydrogen peroxide, whereas sinapyl alcohol polymerization required the addition of a nucleophile. The morphologies of the DHP layers on the surfaces were investigated via atomic force microscopy (AFM). Data from QCM-D and AFM showed that the surface-immobilized HRP-initiated dehydrogenative polymerization of monolignols was greatly affected by the support surface, monolignol concentration, hydrogen peroxide concentration, and temperature.

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Preparation of synthetic lignins with superior NMR characteristics via isotopically labeled monolignols

Cited by 10 publications

References 15 publications

NMR analysis of lignins in CAD-deficient plants. Part 1. Incorporation of hydroxycinnamaldehydes and hydroxybenzaldehydes into lignins

NMR analysis of lignins in CAD-deficient plants. Part 1. Incorporation of hydroxycinnamaldehydes and hydroxybenzaldehydes into lignins

NMR characterization of lignins from transgenic poplars with suppressed caffeic acid O-methyltransferase activity

Surface-Initiated Dehydrogenative Polymerization of Monolignols: A Quartz Crystal Microbalance with Dissipation Monitoring and Atomic Force Microscopy Study

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