Surface Of Cellulose Microfibrils Research Articles

An insight into the mechanism of the cellulose dyeing process: Molecular modelling and simulations of cellulose and its interactions with water, urea, aromatic azo-dyes and aryl ammonium compounds

Potential cellulose-surface active aryl ammonium compounds that may also de-aggregate dye molecules in aqueous solution have been modelled using molecular mechanics methods and simulation methods, and compared with known additives such as amines and urea, as an extrapolation of modelling the interaction of water and urea molecules with cellulose microfibril surfaces. The results from these modelling studies have clearly elucidated the way in which polar molecules interact with cellulose surfaces, and have been used to provide insight into the dyeing process and to identify which new molecular systems might be predicted to act as molecular delivery agents for assisting dye processes.

Models of Xyloglucan Binding to Cellulose Microfibrils1

Abstract Molecular modeling is used to investigate the ways in which plant cell wall xyloglucans might bind to the surface of cellulose microfibrils. Binding involving the xyloglucan backbone is found to be sterically restricted. Plausible models are obtained that involve hydrogen bonding between the xylose residues and one kind of cellulose surface. In such a model, the xyloglucan sidechains mediate, as well as modulate, the binding.

Endo-xyloglucan transferase, a new class of transferase involved in cell wall construction

Cell shape in plants is constrained by cell walls, which are thick yet dynamic structures composed of crystalline cellulose microfibrils and matrix polymers. Xyloglucans are the principal component of the matrix polymers and bind tightly to the surface of cellulose microfibrils and thereby cross-link them to form an interwoven xyloglucan-cellulose network structure. Thus, cleavage and reconnection of the cross-links between xyloglucan molecules are required for the rearrangement of the cell wall architecture, the process essential for both cell wall expansion and the wall deposition occurring during cell growth and differentiation. Endoxyloglucan transferase (EXT) is a newly identified class of transferase that catalyzes molecular grafting between xyloglucan molecules. This enzyme catalyzes both endo-type splitting of a xyloglucan molecule and reconnection of a newly generated reducing terminus of the xyloglucan to the non-reducing terminus of another xyloglucan molecule, thereby mediating molecular grafting between xyloglucan cross-links in plant cell walls. Molecular cloning and sequencing of EXT-cDNAs derived from five different plant species includingA. thaliana andV. angularis has revealed that the amino acid sequence of the mature protein is extensively conserved in the five different plant species, indicating that EXT protein is ubiquitous among higher plants. This structural study has also disclosed the presence of a group of xyloglucan related proteins (XRPs) with transferase activity in higher plants. Current data strongly suggest that these proteins are involved in a wide spectrum of physiological activities including cell wall expansion and deposition in growing cell walls.

Aspect of Native and Redeposited Xylans at the Surface of Cellulose Microfibrils

On etudie la redeposition de xylanes sur la matrice cellulosique d'une pâte kraft de bouleau raffinee et on determine la nature des forces qui controlent la reassociation. L'etude est basee sur les interactions entre des microfibrilles de cellulose preparees a partir du roseau Arundo donax et le xylane correspondant pris comme modeles experimentaux simplifies

A study of the ordered adsorption of metal ions on the surface of cellulose microfibrils

Following observations already made on copper impregnated wood, a detailed study is made of the adsorption by a variety of celluloses of a number of cations from salt solutions. The uptake/concentration curve follows a Langmuir adsorption isotherm so that a surface phenomenon is certainly involved. The uptake is accompanied by a fall in pH of the solution, so that cations appear to be exchanged for hydrogen ions, and is initially rapid.The resultant metal-cellulose complex gives characteristic electron diffraction diagrams of which two types only have been found (together with “hybrids” between them). These diagrams are identically the same whatever the source of the cellulose and for any metallic cation. They can be interpreted on the basis of two-dimensional arrays of copper ions whose parameters are: I: p = 6.15 A, q = 7.05 A, Ø = 90°; II: p = 7.32 Å, q = 5.68 A Ø = 87°–90° (variable). It is concluded that the copper is adsorbed as a monolayer on the outer surface of the microfibrils and this is taken to imply order in the disposition of the chain-molecules at this surface. The parameters bear no relation to the accepted parameters of the (three-dimensional) unit cell of cellulose and suggest further, therefore, that the order at the surface is in some way different from that inside the microfibrils.The impact of the above findings on methods of determining the -COOH content of cellulose is briefly discussed.