title: Conformational changes in single carboxymethylcellulose chains on a highly oriented pyrolytic graphite surface under different salt conditions.
abstract: Conformational changes in individual carboxymethylcellulose (CMC) chains deposited on a highly oriented pyrolytic graphite (HOPG) surface were investigated by atomic force microscopy (AFM). A small amount of CMC solution with various salt concentrations was deposited onto the HOPG surface. The CMC molecular chains adsorbed onto the HOPG surface were clearly visualized using tapping-mode AFM under ambient conditions, as compared with those on a hydrophilic mica surface. Each CMC chain was distinguishable at the molecular level based on the vertical profiles of the AFM images, and probably aligned along the HOPG crystal lattice. Higher NaCl concentrations brought about dramatic conformational changes from aligned single chains to globular aggregates via the molecular network structure only on the HOPG surface through electrostatic screening of the CM groups. Although CMC is a water-soluble hydrophilic polyelectrolyte, some interaction, possibly due to a CH-pi bonding between the glucopyranosic axial plane of CMC and the aromatic rings of HOPG, is considered to be effective and dominant for the unique molecular attachment. These phenomena would imply the potential use of HOPG as a substrate for not only molecular imaging, but also for nano-scale morphological control of cellulosic polymers and other structural polysaccharides.
authors.affiliation: Department of Forest and Forest Products Sciences, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Tomotsugu
authors.initials: T
authors.lastname: Ueno
authors.forename: Shingo
authors.initials: S
authors.lastname: Yokota
authors.forename: Takuya
authors.initials: T
authors.lastname: Kitaoka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Wariishi
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002236:Carbohydrate Conformation; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D003460:Crystallization; D006108:Graphite; D018625:Microscopy, Atomic Force; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D013379:Substrate Specificity; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D012996:Solutions; D014867:Water; D012965:Sodium Chloride; D006108:Graphite; D002266:Carboxymethylcellulose Sodium; C011934:mica