Water-soluble full-length single-wall carbon nanotube polyelectrolytes: Preparation and characterization

HiPco single-wall carbon nanotubes (SWNTs) have been noncovalently modified with ionic pyrene and naphthalene derivatives to prepare water-soluble SWNT polyelectrolytes (SWNT-PEs), which are analogous to polyanions and polycations. The modified nanotubes have been characterized with UV-vis-NIR, fluorescence, Raman and X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The nanotube-adsorbate interactions consist of π-π stacking interactions between the aromatic core of the adsorbate and the nanotube surface and specific contributions because of the substituents. The interaction between nanotubes and adsorbates also involves charge transfer from adsorbates to SWNTs, and with naphthalene sulfonates the role of a free amino group was important. The ionic surface charge density of the modified SWNTs is constant and probably controlled by electrostatic repulsion between like charges. The linear ionic charge density of the modified SWNTs is similar to that of common highly charged polyelectrolytes

Chemical Analysis of Cellular and Extracellular Carbohydrates of a Biofilm-Forming Strain Pseudomonas aeruginosa PA14

Background: Pseudomonas aeruginosa is a Gram-negative bacterium and an opportunistic pathogen, which causes persisting life-threatening infections in cystic fibrosis (CF) patients. Biofilm mode of growth facilitates its survival in a variety of environments. Most P. aeruginosa isolates, including the non-mucoid laboratory strain PA14, are able to form a thick pellicle, which results in a surface-associated biofilm at the air-liquid (A\ufffdL) interface in standing liquid cultures. Exopolysaccharides (EPS) are considered as key components in the formation of this biofilm pellicle. In the non-mucoid P. aeruginosa strain PA14, the \ufffd\ufffdscaffolding\ufffd\ufffd polysaccharides of the biofilm matrix, and the molecules responsible for the structural integrity of rigid A\ufffdL biofilm have not been identified. Moreover, the role of LPS in this process is unclear, and the chemical structure of the LPS O-antigen of PA14 has not yet been elucidated. Principal Findings: In the present work we carried out a systematic analysis of cellular and extracellular (EC) carbohydrates of P. aeruginosa PA14. We also elucidated the chemical structure of the LPS O-antigen by chemical methods and 2-D NMR spectroscopy. Our results showed that it is composed of linear trisaccharide repeating units, identical to those described for P. aeruginosa Lanyi type O:2a,c (Lanyi-Bergman O-serogroup 10a, 10c; IATS serotype 19) and having the following structure: -4)-a-L-GalNAcA-(1\ufffd3)-a-D-QuiNAc-(1\ufffd3)- a-L-Rha-(1-. Furthermore, an EC O-antigen polysaccharide (EC O-PS) and the glycerol-phosphorylated cyclic b-(1,3)-glucans were identified in the culture supernatant of PA14, grown statically in minimal medium. Finally, the extracellular matrix of the thick biofilm formed at the A-L interface contained, in addition to eDNA, important quantities (at least ,20% of dry weight) of LPS-like material. Conclusions: We characterized the chemical structure of the LPS O-antigen and showed that the O-antigen polysaccharide is an abundant extracellular carbohydrate of PA14. We present evidence that LPS-like material is found as a component of a biofilm matrix of P. aeruginosa.Peer reviewed: YesNRC publication: Ye

The structure of glycerol teichoic acid-like O-specific polysaccharide of Hafnia alvei 1205

ABSTRACT The O-specific polysaccharide of Hafniu aluei 1205 contained p-glucose, D-galactose, 2-acetamido-2-deoxy-o-glucose, 4-acetamido-4,6-dideoxy-p-glucose (Qui4NAc), glycerol, phosphate, and 0-acetyl groups. On the basis of 1D and 2D shift-correlated homonuclear and 13C-'H heteronuclear NMR spectroscopy, methylation analysis, Smith degradation, and dephosphorylation with hydrofluoric acid, it was concluded that the O-antigen was a partially 0-acetylated teichoic acid-like polysaccharide having the following structure: cy-D-Glc

The structure of the O−specific polysaccharide of Citrobacter O16 containing glycerol phosphate

The O−specific polysaccharide, obtained by mild acid degradation of Citrobacrer 016 lipopolysaccharide, consists of D−glucose, D−galactose, 2−acetamido−2−deoxy−˜−galactosgel,y cerol and phosphate in the ratios 2 : 2:2 : 1 :l. Selective cleavage of the polysaccharide was carried out by Smith degradation, N−deacetylation−deamination and dephosphorylation with 48 % hydrofluoric acid, which was accompanied by unexpected splitting of one of the glycosidic linkages. The structures of the oligosaccharides thus obtained were established using 'H− and I3C−NMR spectroscopy, including one−dimensional NOE, two−dimensional rotating−frame NOE, homonuclear and heteronuclear 'qC,lH correlation spectroscopy, and, for the Smith degradation product, positive− and negative−ion−mode fast−atom−bombardment MS and MSMS with collision−induced dissociation. On the basis of these data and the results of methylation analysis, it was concluded that the O−specific polysaccharide has the following repeating unit structur