Delineating pMDI model reactions with loblolly pine via solution-state NMR spectroscopy. Part 1. Catalyzed reactions with wood models and wood polymers

Abstract To better understand adhesive interactions with wood, reactions between model compounds of wood and a model compound of polymeric methylene diphenyl diisocyanate (pMDI) were characterized by solution-state NMR spectroscopy. For comparison, finely ground loblolly pine sapwood, milled-wood lignin and holocellulose from the same wood were isolated and derivatized with the pMDI model compound. One-bond 13C–1H correlation (HSQC) experiments on derivatized and dissolved ball-milled wood revealed which hydroxyl group positions of the cell wall polymers reacted with the pMDI model compound to form carbamates. The chemical shifts of the derivatized model compounds correspond precisely to the chemical shifts of derivatized wood polymers. These model experiments will be taken as a basis in the next phase of our research (Part 2), in which the reactions of pMDI model compounds will be studied with intact wood cell walls under conditions similar to those used in oriented strand-board production.

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Delineating pMDI model reactions with loblolly pine via solution-state NMR spectroscopy. Part 2. Non-catalyzed reactions with the wood cell wall

Holzforschung ◽

10.1515/hf.2011.029 ◽

2011 ◽

Vol 65 (2) ◽

Cited By ~ 2

Author(s):

Daniel J. Yelle ◽

John Ralph ◽

Charles R. Frihart

Keyword(s):

Cell Wall ◽

Moisture Content ◽

Loblolly Pine ◽

Quantum Coherence ◽

Oriented Strand Board ◽

Hydroxyl Groups ◽

High Concentration ◽

Model Compounds ◽

Covalent Bonds ◽

Solution State

Abstract Solution-state NMR provides a powerful tool to observe the presence or absence of covalent bonds between wood and adhesives. Finely ground wood can be dissolved in an NMR-compatible solvent system containing dimethylsulfoxide-d 6 and N-methylimidazole-d 6 , in which the wood polymers remain largely intact. High-resolution solution-state two-dimensional NMR correlation experiments, based on 13C–1H one-bond heteronuclear single quantum coherence, allow structural analysis of the major cell wall components. This technique was applied to loblolly pine that was treated with polymeric methylene diphenyl diisocyanate (pMDI) related model compounds under controlled moisture and temperature conditions. Chemical shifts of carbamates formed between the pMDI model compounds and loblolly pine were determined. The results show that: (a) under dry conditions and a high concentration of isocyanate, carbamates will form preferentially with side-chain hydroxyl groups on β-aryl ether and phenylcoumaran-linked lignin units in a swelling solvent; (b) phenyl isocyanate is more capable of derivatization in the cell wall than the bulkier 4-benzylphenyl isocyanate; (c) at 5% and 14% moisture content, detectable carbamates on lignin side-chains dramatically decrease; and (d) under typical conditions of industrial oriented strand-board production in a hot press at 5% and 14% moisture content, no carbamate formation was detected.

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Introduction Nuclear Magnetic Resonance Spectroscopy: Basic Theory and Background

Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry ◽

10.1093/oso/9780195097511.003.0004 ◽

1997 ◽

Author(s):

Heike Knicker ◽

Mark A. Nanny

Keyword(s):

Nuclear Magnetic Resonance ◽

Nmr Spectroscopy ◽

Magnetic Resonance ◽

Chemical Shifts ◽

Level Structure ◽

Relaxation Times ◽

Coupling Constants ◽

Solution State ◽

The Many ◽

Nuclear Magnetic

Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental methods available for atomic and molecular level structure elucidation. It is a powerful technique in that it is a noninvasive probe that can be used to identify individual compounds, aid in determining structures of large macromolecules, such as proteins, and examine the kinetics of certain reactions. NMR spectroscopy takes advantage of the magnetic properties of the observed nucleus that are influenced not only by its chemical environment, but also by physical interactions with its environment. Both can be examined by measuring specific NMR parameters such as coupling constants, relaxation times, or changes in chemical shifts. As NMR techniques and instrumentation advance, NMR spectroscopy is becoming more important in the environmental sciences, tackling problems and questions that previously were difficult to answer. For example, sensitivity enhancement techniques increase the ability to examine a sample without chemical or physical pretreatment. A sample examined in this manner is in its original state and is unaffected by chemical or physical reactions caused by the pretreatment procedure. Despite its increasing popularity and numerous advantages, NMR spectroscopy can be a mysterious, and at times daunting, technique. The purpose of this chapter is to provide an overview of basic NMR theory and background for the uninitiated. It is hoped that it will provide enough information to those unfamiliar with NMR and its terminology for them to find the remaining chapters understandable and interesting. Those who desire a greater understanding are referred to the many textbooks on solution-state NMR, solid-state NMR, and the application of NMR to geochemistry, soil chemistry, oils and coals, and carbonaceous solids. The advance that led to NMR spectroscopy came in 1939 with resonance experiments by Rabi and coworkers, who demonstrated the property of nuclear spin. In 1945, the research groups of Bloch and Purcell independently obtained the first nuclear resonance signals. For this they won the 1952 Nobel prize. The first application of NMR spectroscopy in the field of humic substance research was 1H NMR of liquids. González-Vila et al. were the first to apply 13C solution-state NMR to natural humic acids.

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Polyoxometalate (POM) oxidation of lignin model compounds

Holzforschung ◽

10.1515/hf.2008.006 ◽

2008 ◽

Vol 62 (1) ◽

pp. 38-49 ◽

Cited By ~ 14

Author(s):

Yong Sik Kim ◽

Hou-min Chang ◽

John F. Kadla

Keyword(s):

Reaction Rate ◽

Model Compound ◽

Reaction Rates ◽

Hydroxyl Group ◽

Model Compounds ◽

Lignin Model Compounds ◽

Lignin Model Compound ◽

First Order ◽

Resonance Stabilization ◽

Lignin Model

Abstract Various lignin model compounds were oxidized with polyoxometalate (POM), K5[SiVW11O40]·12 H2O, in sodium acetate buffer (I=0.2 M, pH 5.0) and the reaction kinetics were investigated. The reactions were found to have second order reaction rates, first order with regards to both lignin model compound and POM. A dramatic increase in reactivity was observed upon addition of methoxyl groups in ortho-positions to the phenolic hydroxyl group. Syringyl units reacted faster than guaiacyl units. Reaction rates of para-substituted guaiacyl and syringyl model compounds showed a strong dependency on the nature of the substituents. The reaction rate of a 5-5′ dimer lignin model compound was extremely fast. The addition of the ortho-phenol substituent not only increased the electron density of the aromatic ring, but also helped stabilize the intermediate phenoxy radical through resonance stabilization and delocalization.

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Structure of Nanobody Nb23

Molecules ◽

10.3390/molecules26123567 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3567

Author(s):

Mathias Percipalle ◽

Yamanappa Hunashal ◽

Jan Steyaert ◽

Federico Fogolari ◽

Gennaro Esposito

Keyword(s):

Nmr Spectroscopy ◽

Chemical Shift ◽

Solution Structure ◽

Chemical Shifts ◽

Molecular Size ◽

Side Chain ◽

3D Nmr ◽

Target Antigen ◽

Internuclear Distances ◽

2D And 3D

Background: Nanobodies, or VHHs, are derived from heavy chain-only antibodies (hcAbs) found in camelids. They overcome some of the inherent limitations of monoclonal antibodies (mAbs) and derivatives thereof, due to their smaller molecular size and higher stability, and thus present an alternative to mAbs for therapeutic use. Two nanobodies, Nb23 and Nb24, have been shown to similarly inhibit the self-aggregation of very amyloidogenic variants of β2-microglobulin. Here, the structure of Nb23 was modeled with the Chemical-Shift (CS)-Rosetta server using chemical shift assignments from nuclear magnetic resonance (NMR) spectroscopy experiments, and used as prior knowledge in PONDEROSA restrained modeling based on experimentally assessed internuclear distances. Further validation was comparatively obtained with the results of molecular dynamics trajectories calculated from the resulting best energy-minimized Nb23 conformers. Methods: 2D and 3D NMR spectroscopy experiments were carried out to determine the assignment of the backbone and side chain hydrogen, nitrogen and carbon resonances to extract chemical shifts and interproton separations for restrained modeling. Results: The solution structure of isolated Nb23 nanobody was determined. Conclusions: The structural analysis indicated that isolated Nb23 has a dynamic CDR3 loop distributed over different orientations with respect to Nb24, which could determine differences in target antigen affinity or complex lability.

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Resolving Entangled JH-H-Coupling Patterns for Steroidal Structure Determinations by NMR Spectroscopy

Molecules ◽

10.3390/molecules26092643 ◽

2021 ◽

Vol 26 (9) ◽

pp. 2643

Author(s):

Danni Wu ◽

Kathleen Joyce Carillo ◽

Jiun-Jie Shie ◽

Steve S.-F. Yu ◽

Der-Lii M. Tzou

Keyword(s):

Nmr Spectroscopy ◽

1H Nmr Spectroscopy ◽

Chemical Shifts ◽

Atomic Level ◽

Molecular Structures ◽

Naturally Occurring ◽

Structure Determinations ◽

Ligand Interactions ◽

Synthetic Steroids ◽

The Individual

For decades, high-resolution 1H NMR spectroscopy has been routinely utilized to analyze both naturally occurring steroid hormones and synthetic steroids, which play important roles in regulating physiological functions in humans. Because the 1H signals are inevitably superimposed and entangled with various JH–H splitting patterns, such that the individual 1H chemical shift and associated JH–H coupling identities are hardly resolved. Given this, applications of thess information for elucidating steroidal molecular structures and steroid/ligand interactions at the atomic level were largely restricted. To overcome, we devoted to unraveling the entangled JH–H splitting patterns of two similar steroidal compounds having fully unsaturated protons, i.e., androstanolone and epiandrosterone (denoted as 1 and 2, respectively), in which only hydroxyl and ketone substituents attached to C3 and C17 were interchanged. Here we demonstrated that the JH–H values deduced from 1 and 2 are universal and applicable to other steroids, such as testosterone, 3β, 21-dihydroxygregna-5-en-20-one, prednisolone, and estradiol. On the other hand, the 1H chemical shifts may deviate substantially from sample to sample. In this communication, we propose a simple but novel scheme for resolving the complicate JH–H splitting patterns and 1H chemical shifts, aiming for steroidal structure determinations.

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Carbon-dot organic surface modifier analysis by solution-state NMR spectroscopy

Journal of Nanoparticle Research ◽

10.1007/s11051-013-1777-0 ◽

2013 ◽

Vol 15 (7) ◽

Cited By ~ 6

Author(s):

Aggelos Philippidis ◽

Apostolos Spyros ◽

Demetrios Anglos ◽

Athanasios B. Bourlinos ◽

Radek Zbořil ◽

...

Keyword(s):

Nmr Spectroscopy ◽

Carbon Dot ◽

Surface Modifier ◽

Solution State

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Reversal of order of chemical shifts. Differential solvent effects in the hydrogen shifts of toluene,m-xylene ando-xylene as determined by 320 MHz tritium NMR spectroscopy

Organic Magnetic Resonance ◽

10.1002/mrc.1270221014 ◽

1984 ◽

Vol 22 (10) ◽

pp. 665-667 ◽

Cited By ~ 1

Author(s):

Mervyn A. Long ◽

John K. Saunders ◽

Philip G. Williams ◽

Allan L. Odell ◽

R. Wayne Martin

Keyword(s):

Nmr Spectroscopy ◽

Solvent Effects ◽

Chemical Shifts ◽

Tritium Nmr ◽

Hydrogen Shifts

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Determination of chemical shifts in 6-condensed syringylic lignin model compounds

Holzforschung ◽

10.1515/hf-2021-0093 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Lucas Lagerquist ◽

Jani Rahkila ◽

Patrik Eklund

Keyword(s):

Chemical Shift ◽

Methoxy Group ◽

Chemical Shifts ◽

Model Compounds ◽

Correlation Peak ◽

Lignin Model Compounds ◽

Benzylic Alcohols ◽

Lignin Model ◽

C Nmr

Abstract A small library of 6-substituted syringyl model compounds with aliphatic, carboxylic, phenylic, benzylic alcohols and brominated substituents were prepared. The influence of the substituents on the chemical shifts of the compounds was analyzed. All of model compounds showed a characteristic increase in the 13C NMR chemical shift of the methoxy group vicinal to the substitution. This 13C NMR peak and its corresponding correlation peak in HSQC could potentially be used to identify 6-condensation in syringylic lignin samples.

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