title: Instantaneous inclusion of a polynucleotide and hydrophobic guest molecules into a helical core of cationic beta-1,3-glucan polysaccharide.
abstract: We succeeded in the quantitative and selective introduction of an ammonium cationic group into the C6 position of Curdlan (CUR) by "Click Chemistry", and the obtained cationic Curdlan (CUR-N+) showed good solubility in water. ORD studies suggested that CUR-N+ adopts a single-stranded structure, different from a right-handed, triple-stranded helical structure of beta-1,3-glucan polysaccharides in water. It has been revealed that the polymeric complexes of CUR-N+ with polymeric guest molecules, such as polycytidylic acid (poly(C)), permethyldecasilane (PMDS), and single-walled carbon nanotubes (SWNTs), can be easily obtained by just mixing them in water with sonication. The characterization of the resultant CUR-N+-poly(C) complexes by UV-vis, CD spectroscopic measurements, and AFM and TEM observations revealed that they have stoichiometric, nanosized fibrous structures. From these experimental results as well as our precedent studies (e.g., refs 6 and 23), we propose that the complexation would be driven by the cooperative action of (1) the hydrogen-bonding interaction between the OH group at the C2 position and hydrogen-bonding sites of the cytosine ring (ref 6d), (2) the electrostatic interaction between the ammonium cation and the phosphate anion (ref 23), as well as (3) the background hydrophobic interaction. In addition, the complexed polynucleotide chain showed a strong resistance against enzymatic hydrolysis. Likewise, the dispersion of PMDS and SWNTs in water by CUR-N+ and the fibrous structures of the complexes were confirmed by spectroscopic measurements as well as microscopic observations. These binding properties of CUR-N+, which can proceed spontaneously in water, clearly differ from those of schizophyllan (SPG), which inevitably require a denature-renature process corresponding to a conversion of a triple strand to single strands induced by DMSO or base for inclusion of polymeric guest molecules.
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Ikeda
authors.forename: Teruaki
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Munenori
authors.initials: M
authors.lastname: Numata
authors.forename: Kouta
authors.initials: K
authors.lastname: Sugikawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sakurai
authors.forename: Michiya
authors.initials: M
authors.lastname: Fujiki
authors.forename: Seiji
authors.initials: S
authors.lastname: Shinkai
mesh_terms: D002236:Carbohydrate Conformation; D002412:Cations / Q000737:chemistry*; D005936:Glucans / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D011119:Polynucleotides / Q000737:chemistry*; D012260:Ribonucleases / Q000378:metabolism; D012996:Solutions; D013057:Spectrum Analysis; D047071:beta-Glucans / Q000737:chemistry
chemical_list: D002412:Cations; D005936:Glucans; D011119:Polynucleotides; D012996:Solutions; D047071:beta-Glucans; C003045:paramylon; C038459:curdlan; D012260:Ribonucleases