Structural Aspects in Semicrystalline Samples of the Mannan II Family

Abstract

A series of samples having the mannan II character were prepared by either (i) desincrusting stems of Acetabularia crenulata, or (ii) acetylating these stems, followed by dissolution and recrystallization under deacetylation conditions, or (iii) recrystallizing at low temperature the alkali soluble fraction of ivory nut mannan. The samples were characterized by transmission electron microscopy, X-ray and electron diffraction analysis together with (13)C CP/MAS NMR spectroscopy. Whereas the A. crenulata stems consisted of a mixture of mannan I and mannan II, the recrystallized samples were all of the hydrated mannan II family and occurred in a ribbonlike morphology where the mannan chains were organized with their molecular axis perpendicular to the ribbon long axis. The recrystallized ivory nut mannan samples presented X-ray and electron diffraction diagrams, together with (13)C solid-state NMR spectra recorded at 95% RH, different from those of recrystallized A. crenulata recorded under the same RH conditions. They corresponded therefore to a new allomorph of the mannan II family. Despite this difference, when the recrystallized samples were in an aqueous environment, they revealed an additional well-defined perhydrated phase, which showed the same (13)C solid-state NMR spectrum for both samples. As this phase, which gave 6-band NMR spectra with narrow line-width and low T1, had no counterpart in X-ray diffraction, it was attributed to specific amorphous segments of mannan chains, gaining some mobility when swollen in water. When the samples were totally dried, their NMR spectra lost their resolution, thus indicating the role played by water for the structural organization of the crystalline and amorphous components of mannan II.

Molecular architecture of softwood revealed by solid-state NMR

“…Such a change in M4 shift suggests that GGM adopts an altered in muro conformation, possibly when bound to cellulose, as seen when xylan is bound to cellulose 14 . Interestingly, the carbon 1, 4 and 6 shifts are similar to those of the mannan I crystal allomorph (Supplementary Table 2), which can be formed by unbranched mannans 31,32 . In this crystal allomorph, the mannosyl residues are in a two-fold screw conformation, similar to the glucan chains of cellulose, suggesting that the branched GGM in spruce cell walls may form a two-fold screw.…”

Morphological investigation of cellulose nanocrystals and nanocomposite applications

“…The resulting crystals were described as rod-like or ribbon-like depending on the source of mannan, with a width of 7 and 30 nm, respectively, and corresponding to allomorph II. As first shown by Bittiger and Husemann (1972) and confirmed by Heux et al (2005), the mannan chains lie perpendicular to the long axis of the particles. The crooked aspect of the ribbons of mannan from A. crenulata is very similar to that of our RCN-II nanocrystals.…”

“…The ribbon-like RCN-II nanocrystals present a strong analogy with the particles prepared by precipitation of mannan, a linear homopolymer of β- (1,4)-D-mannosyl residues found as an energy reserve or a cell-wall structural component in plants and algae (Chanzy et al, 1984). Heux et al (2005) precipitated solutions of mannan from ivory nut ( ̅̅̅̅̅̅ 30) and the seaweed Acetabularia crenulata ( ̅̅̅̅̅̅ 350). The resulting crystals were described as rod-like or ribbon-like depending on the source of mannan, with a width of 7 and 30 nm, respectively, and corresponding to allomorph II.…”

Preparation and Characterization of Lactobacilli‐Loaded Composite Films with Sustaining Antipathogenic Activity and Preservation Effect

“…Note: RR, F, TA, SSC, V c , and TPC represent respiration rate, firmness, titratable acidity, soluble solids content, ascorbic acid content and total phenolic content, respectively. and looser molecular arrangement (Heux, Hägglund, Putaux, & Chanzy, 2005;Li et al, 2014;Xiao, Liu, Lu, & Zhang, 2010). It also can be seen that some changes of crystallization properties have taken place in the HPC-KF complex film.…”

“…The XRD spectra of pure HPC showed two characteristic peaks at 2 θ values of about 9° and 20° (Figure A), which are separately attributed to the crystalline phase and the ordered amorphous phase of HPC (Halamus, Wojciechowski, & Bobowska, ; Wojciechowski, ). Furthermore, the XRD pattern of KF, a broad hump centered at 2 θ = 20° (Figure B), was characterized by a typical amorphous state on account of the weak molecular interactions and looser molecular arrangement (Heux, Hägglund, Putaux, & Chanzy, ; Li et al., ; Xiao, Liu, Lu, & Zhang, ). It also can be seen that some changes of crystallization properties have taken place in the HPC–KF complex film.…”