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Cellulose microfibril orientation of Picea abies and its variability at the micron-level determined by Raman imaging.

Gierlinger N, Luss S, König C, Konnerth J, Eder M, Fratzl P - J. Exp. Bot. (2009)

Bottom Line: The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns.Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle).With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

View Article: PubMed Central - PubMed

Affiliation: Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Strasse 69, Linz, Austria.

ABSTRACT
The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns. Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle). By changing the laser polarization direction in 3 degrees steps, the dependency between cellulose and laser orientation direction was investigated. Orientation-dependent changes of band height ratios and spectra were described by quadratic linear regression and partial least square regressions, respectively. Using the models and regressions with high coefficients of determination (R(2) > 0.99) microfibril orientation was predicted in the S1 and S2 layers distinguished by the Raman imaging approach in cross-sections of spruce normal, opposite, and compression wood. The determined microfibril angle (MFA) in the different S2 layers ranged from 0 degrees to 49.9 degrees and was in coincidence with X-ray diffraction determination. With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

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Related in: MedlinePlus

Changes in the fingerprint region of baseline corrected spectra acquired from one position of the tangential S2 layer of a mechanically isolated single spruce latewood fibre whilst rotating the polarization direction of the incident laser in 3° steps from parallel (0°, red) to perpendicular (90°, black) with respect to the fibre axis (red: 0, 3, 6, 9°, pink: 12, 15, 18, 21°; turquoise, 24, 27, 30, 33°; blue, 36, 39, 42, 45; light green, 48, 51, 54, 57°; green: 60, 63, 66, 69°; grey: 72, 75, 78, 81°; black: 84, 87, 90, 93°).
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fig2: Changes in the fingerprint region of baseline corrected spectra acquired from one position of the tangential S2 layer of a mechanically isolated single spruce latewood fibre whilst rotating the polarization direction of the incident laser in 3° steps from parallel (0°, red) to perpendicular (90°, black) with respect to the fibre axis (red: 0, 3, 6, 9°, pink: 12, 15, 18, 21°; turquoise, 24, 27, 30, 33°; blue, 36, 39, 42, 45; light green, 48, 51, 54, 57°; green: 60, 63, 66, 69°; grey: 72, 75, 78, 81°; black: 84, 87, 90, 93°).

Mentions: The ScanCtrlSpectroscopyPlus software (Witec, Germany) was used for the measurement set-up and image processing and the OPUS software (Bruker, Germany) for spectra manipulation and Partial least squares (PLS) regression analyses. Before calculating the band height ratios, a baseline correction (concave rubberband, 64 points) was performed and, for the PLS modelling, in addition a normalization on the 1122 cm−1 band. The aim of a PLS-model is to determine the property Y of a system from an experimentally observable X, whereby X and Y are correlated by a calibration function b(Y=X×b). The vector Y consists of the component values as determined by the reference measurements. The row vectors of the matrix X are formed from the calibration spectra. The vector b is determined and used for the prediction of unknown values for Yn. Sixty-four spectra were used for cross validation (always one sample left out for validation) and, for test set validation, half of the samples were used as a test set. Wavenumber selection was done iteratively based on the visible differences in the spectra (Fig. 2) and the loadings calculated using the whole wavenumber range. The loadings (factors) describe the weighting of the individual x-variables with regard to their contribution to the variance. They allow to determine which data points make the biggest variance between the samples in order to assess the importance of the individual variable for the calibration. The optimal number of PLS components (factors) was estimated by the OPUS software, as described in Gierlinger et al. (2002).


Cellulose microfibril orientation of Picea abies and its variability at the micron-level determined by Raman imaging.

Gierlinger N, Luss S, König C, Konnerth J, Eder M, Fratzl P - J. Exp. Bot. (2009)

Changes in the fingerprint region of baseline corrected spectra acquired from one position of the tangential S2 layer of a mechanically isolated single spruce latewood fibre whilst rotating the polarization direction of the incident laser in 3° steps from parallel (0°, red) to perpendicular (90°, black) with respect to the fibre axis (red: 0, 3, 6, 9°, pink: 12, 15, 18, 21°; turquoise, 24, 27, 30, 33°; blue, 36, 39, 42, 45; light green, 48, 51, 54, 57°; green: 60, 63, 66, 69°; grey: 72, 75, 78, 81°; black: 84, 87, 90, 93°).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803219&req=5

fig2: Changes in the fingerprint region of baseline corrected spectra acquired from one position of the tangential S2 layer of a mechanically isolated single spruce latewood fibre whilst rotating the polarization direction of the incident laser in 3° steps from parallel (0°, red) to perpendicular (90°, black) with respect to the fibre axis (red: 0, 3, 6, 9°, pink: 12, 15, 18, 21°; turquoise, 24, 27, 30, 33°; blue, 36, 39, 42, 45; light green, 48, 51, 54, 57°; green: 60, 63, 66, 69°; grey: 72, 75, 78, 81°; black: 84, 87, 90, 93°).
Mentions: The ScanCtrlSpectroscopyPlus software (Witec, Germany) was used for the measurement set-up and image processing and the OPUS software (Bruker, Germany) for spectra manipulation and Partial least squares (PLS) regression analyses. Before calculating the band height ratios, a baseline correction (concave rubberband, 64 points) was performed and, for the PLS modelling, in addition a normalization on the 1122 cm−1 band. The aim of a PLS-model is to determine the property Y of a system from an experimentally observable X, whereby X and Y are correlated by a calibration function b(Y=X×b). The vector Y consists of the component values as determined by the reference measurements. The row vectors of the matrix X are formed from the calibration spectra. The vector b is determined and used for the prediction of unknown values for Yn. Sixty-four spectra were used for cross validation (always one sample left out for validation) and, for test set validation, half of the samples were used as a test set. Wavenumber selection was done iteratively based on the visible differences in the spectra (Fig. 2) and the loadings calculated using the whole wavenumber range. The loadings (factors) describe the weighting of the individual x-variables with regard to their contribution to the variance. They allow to determine which data points make the biggest variance between the samples in order to assess the importance of the individual variable for the calibration. The optimal number of PLS components (factors) was estimated by the OPUS software, as described in Gierlinger et al. (2002).

Bottom Line: The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns.Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle).With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

View Article: PubMed Central - PubMed

Affiliation: Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Strasse 69, Linz, Austria.

ABSTRACT
The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns. Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle). By changing the laser polarization direction in 3 degrees steps, the dependency between cellulose and laser orientation direction was investigated. Orientation-dependent changes of band height ratios and spectra were described by quadratic linear regression and partial least square regressions, respectively. Using the models and regressions with high coefficients of determination (R(2) > 0.99) microfibril orientation was predicted in the S1 and S2 layers distinguished by the Raman imaging approach in cross-sections of spruce normal, opposite, and compression wood. The determined microfibril angle (MFA) in the different S2 layers ranged from 0 degrees to 49.9 degrees and was in coincidence with X-ray diffraction determination. With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

Show MeSH
Related in: MedlinePlus