Related Experiment Video
Updated: Aug 16, 2026
07:35
Label-free in situ Imaging of Lignification in Plant Cell Walls
Published on: November 1, 2010
Structural analysis of lignin by resonance Raman spectroscopy
Søren Barsberg1, Pavel Matousek, Mike Towrie
1Forest and Landscape, The Royal Veterinary and Agricultural University, Højbakkegård Allé 1, DK-2630 Taastrup, Denmark. sbar@kvl.dk
Macromolecular Bioscience
|August 10, 2005
Summary
Resonance Raman (RR) spectroscopy offers new insights into fluorescent natural macromolecules like lignin. This study explains RR spectral behavior, revealing wavelength-dependent sensitivity crucial for structural analysis.
Area of Science:
- Spectroscopy
- Biochemistry
- Materials Science
Background:
- Resonance Raman (RR) spectroscopy, coupled with Kerr gated fluorescence rejection, provides unique sensitivity for studying lignin structure.
- Previous limitations in analyzing fluorescent natural macromolecules like lignin are being overcome by advanced spectroscopic techniques.
- The RR spectral behavior of lignin is not well understood, hindering detailed structural investigations.
Purpose of the Study:
- To elucidate the Resonance Raman spectral behavior of lignin for the first time.
- To develop a theoretical framework explaining RR spectral characteristics in vascular plant lignin.
- To investigate how excitation wavelength influences RR sensitivity and selectivity for lignin structural elements.
Main Methods:
- Utilized Resonance Raman (RR) spectroscopy combined with Kerr gated fluorescence rejection in the time domain.
- Employed well-defined oxidative treatments to probe specific lignin structural elements.
- Applied a semi-empirical theory to explain observed RR spectral behavior and its dependence on excitation wavelength (e.g., 400 nm vs. 500 nm).
Main Results:
- A semi-empirical theory was developed to explain RR spectral behavior in vascular plant lignin.
- RR sensitivity and selectivity were found to be critically dependent on the excitation wavelength.
- Blue light excitation (400 nm) highlighted low redox potential syringyl lignin groups, while lower photon energy (500 nm) reduced selectivity.
Conclusions:
- The study provides the first theoretical explanation for RR spectral behavior in lignin.
- Excitation wavelength significantly impacts RR spectral analysis, with blue light offering higher selectivity for specific lignin moieties.
- Charge transfer interactions within lignin influence RR band intensity, offering deeper insights into molecular structure and environment.
Related Concept Videos
01:20Raman Spectroscopy: Overview
The underlying principle of Raman spectroscopy is based on the interaction between light and matter, specifically molecules' inelastic scattering of photons. When a monochromatic beam of light, typically from a laser source, interacts with a sample, most scattered light has the same frequency as the incident light. This is known as Rayleigh scattering.
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and the...
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and the...
01:26Raman Spectroscopy Instrumentation: Overview
A conventional Raman spectrophotometer includes a laser source, a sample holding system, a wavelength selector, and a detector.
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
01:24IR Spectroscopy: Molecular Vibration Overview
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
01:14NMR Spectroscopy of Aromatic Compounds
Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
01:03IR Frequency Region: Fingerprint Region
IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the C=O, C=N, and C=C occur between 1600–1850 cm−1.
The...
The...