Nanostructure of cellulose microfibrils in spruce wood

Fernandes, Anwesha N.; Thomas, Lynne H.; Altaner, Clemens M.; Callow, Philip; Forsyth, V. Trevor; Apperley, David C.; Kennedy, Craig J; Jarvis, Michael C.

doi:10.1073/pnas.1108942108

Cited by 625 publications

(766 citation statements)

References 82 publications

Supporting

Mentioning

693

Contrasting

Unclassified

Order By: Relevance

“…The two peaks have also been assigned as the signals from solventexposed and interior chains, respectively (Ha et al 1998;Newman 1998). The intensity ratio between these two peaks gives information about the number of chains in the microfibril, which is consistent with the results obtained from diffraction methods and absorption spectroscopy, which collectively constrain the cross-sectional dimension of cellulose microfibrils (Fernandes et al 2011). However, the molecular structures of cellulose responsible for the specific surface and interior C4 peaks have not been positively confirmed.…”

Section: Introductionsupporting

confidence: 77%

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

et al. 2017

View full text Add to dashboard Cite

The doublet C4 peaks at * 85 and * 89 ppm in solid-state 13 C NMR spectra of native cellulose have been attributed to signals of C4 atoms on the surface (solvent-exposed) and in the interior of microfibrils, designated as sC4 and iC4, respectively. The relative intensity ratios of sC4 and iC4 observed in NMR spectra of cellulose have been used to estimate the degree of crystallinity of cellulose and the number of glucan chains in cellulose microfibrils. However, the molecular structures of cellulose responsible for the specific surface and interior C4 peaks have not been positively confirmed. Using density functional theory (DFT) methods and structures produced from classical molecular dynamics simulations, we investigated how the following four factors affect 13 C NMR chemical shifts in cellulose: conformations of exocyclic groups at C6 (tg, gt and gg), H 2 O molecules H-bonded on the surface of the microfibril, glycosidic bond angles (U, W) and the distances between H4 and HO3 atoms. We focus on changes in the d 13 C4 value because it is the most significant observable for the same C atom within the cellulose structure. DFT results indicate that different conformations of the exocyclic groups at C6 have the greatest influence on d 13 C4 peak separation, while the other three factors have secondary effects that increase the spread of the calculated C4 interior and surface peaks.

show abstract

Section: Introductionsupporting

confidence: 77%

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Based on the individual spectra, the native state relative hydroxyl accessibility is calculated and is shown in Fig. 3 to be about 40-45% of hydroxyls accessible to liquid water in line with other studies on wood (Altaner et al 2006;Chow 1972;Fackler and Schwanninger 2011;Fernandes et al 2011;Taniguchi et al 1966). This is, however, lower than the theoretically estimated accessibility which includes all hydroxyls in lignin and hemicelluloses as well as those cellulose microfibril surface hydroxyls accessible for deuteration, see electronic supplementary material.…”

Section: Hydroxyl Accessibility To Liquid D 2 Omentioning

confidence: 77%

“…Deuterated water has been used in a number of studies to assess wood cell wall hydroxyl accessibility to water (Altaner et al 2006;Chow 1972;Fackler and Schwanninger 2011;Fernandes et al 2011;Kontturi and Vuorinen 2009;Suchy 2011;Suchy et al 2010a, b;Sumi et al 1964;Taniguchi et al 1966Taniguchi et al , 1978, as functional groups capable of forming H-bonded complexes with water can have their hydrogen exchanged with deuterium (Englander et al 1972). This exchange can be detected by spectroscopic or gravimetric techniques, both of which are employed in the current study.…”

Section: Introductionmentioning

confidence: 99%

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

2017

View full text Add to dashboard Cite

The first drying of wood cell walls from the native state has sometimes been described as producing irreversible structural changes which reduce the accessibility to water, a phenomenon often referred to as hornification. This study demonstrates that while changes do seem to take place, these are more complex than what has hitherto been described. The accessibility of wood cell wall hydroxyls to deuteration in the form of liquid water was not found to be affected by drying, since vacuum impregnation with liquid water restores the native cell wall accessibility. Contrary to this, hydroxyl accessibility to deuteration by water vapour was found to decrease to different levels depending on the drying conditions. Vacuum drying at 60°C for 3 days reduced the accessibility more than drying for 1 day at 103°C without vacuum. Drying for 3 days at 103°C increased the hydroxyl accessibility compared to 1 day. Moreover, the decrease in hydroxyl accessibility to deuteration by water vapour induced by the first drying could be at least partially erased by subsequent vacuum impregnation with liquid water, indicating reversibility. For the drying of solid, non-degraded wood cell walls the results challenge the often supposed process of hornification, understood as a permanent decrease in hydroxyl accessibility to water.

show abstract

“…Covalent bonds were created across the periodic box in order to model infinitely long chains. Following the models of Xu et al (2009) and Fernandes et al (2011) who described the surface of cellulose microfibrils as consisting of a mixture of dominant hydrophilic and minor hydrophobic components, our cellulose model exposes 3 chains of the hydrophobic (1 0 0) surface. Two types of cellulose chains were considered: (1) those unconstrained in the top two layers, which may interact with the CR molecules; (2) those in the two underlying layers, which are composed of chains that will not be in contact with the adsorbate; they represent the inner bulk chains of cellulose and were constrained.…”

Section: System Preparationmentioning

confidence: 99%

Modelling of Congo red adsorption on the hydrophobic surface of cellulose using molecular dynamics

Mazeau

Wyszomirski

2012

Cellulose

View full text Add to dashboard Cite

This study describes the interaction between crystalline cellulose and the direct dye Congo red (CR) using molecular dynamics simulations. A model of a microfibril corner of cellulose Ib, exposing one hydrophobic (1 0 0) and the two hydrophilic (1 1 0) and (1 -1 0) surfaces was built. The energetic and geometric features of the dye adsorption were investigated at different temperatures following different initial positions of the CR. The relative positions and orientations of the CR with respect to the cellulose surface were unambiguously characterized using three translation (shift, slide, and rise) and three rotation (roll, tilt, and twist) parameters. Changes of twist and roll parameters showed that there was a tendency for the once adsorbed dye molecules, to become more planar and parallel to the cellulose surface. Several stable adsorption sites, translated laterally with respect to one another were obtained and adsorbed CR molecules were laid with their long axis either parallel or inclined by 50°with respect to the cellulose chain axis. Both vacuum and explicit water environments were considered. In this latter case, there was an increase in the energy of interaction between CR and cellulose and the adsorbed dye molecule behaved more rigidly than in vacuum case.

show abstract

Nanostructure of cellulose microfibrils in spruce wood

Cited by 625 publications

References 82 publications

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

Modelling of Congo red adsorption on the hydrophobic surface of cellulose using molecular dynamics

Contact Info

Product

Resources

About