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

Abstract

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.

Validation and extended application of cellulose microfibril swelling enzyme assay method to alkali induced swelling of cellulose

“…The interaction of CR with cellulose is exothermic, and CR molecules are adsorbed on cellulose surface through chemical interactions. During CR adsorption, most of the H-bonds occur via the sulfonate, amino, and azo groups of CR and hydroxyl methyl groups of C2 and C6 carbon atom of each glucosyl ring of cellulose (Mazeau et al, 2012). Therefore, the increased CAE might mainly be due to the enhanced H-bonding of CR with the exposed hydroxyl groups of cellulose.…”

“…However, in swelled cellulose, the hydrogen bond degradation occurs instead of cellulose degradation, may cause more exposure of free hydroxyl groups that may enhance the Congo red binding site. Chemical structure of an individual dye determines the possibility of a break up of fiber-fiber hydrogen bonds, with a simultaneous creation of fiber-dye bonds (Mazeau et al, 2012). Thus amorphous area generated by the disruption of H-bonds that expose more -OH in crystal-Vol-2 Issue-1 SIFT DESK line cellulose, further binds with Congo red.…”

Medium optimization of beta-glucanase production by Bacillus subtilis SAHA 32.6 used as biological control of oil palm pathogen

“…Congo-red dye will detect nonpolar hydrogen linked (β-glycosidic) on polysaccharides. The detection due to the strongly hydrophobic interactions of van der walls between dye and polysaccharide which contain nonpolar hydrogen linked (Teather and Wood 1982;Mazeau and Wyszomirski 2012).…”

Critical review of the methods of β-glucan analysis and its significance in the beer filtration process

“…After incubation at room temperature for 20 min, the absorbance is measured at 550 nm and compared with that of a blank reaction mixture [30]. Reasons for this specific binding to glucose units linked by β-glycosidic bonds include electrostatic and hydrogenbonding interactions, as well as van der Waals-type attractions of the two aromatic moieties of the dye with the corresponding hydrophobic cellulose surface [70]. Investigations of Anderson [30] showed that the Congo red reaction is optimally sensitive to β-glucans with a molecular weight of approximately 250 kDa.…”