title: Interactions of bacterial polysaccharides with cationic dyes: physicochemical studies.
abstract: Capsular polysaccharides (SPS) are an integral component of gram-negative bacteria, and also have potential use as vaccine. In this paper, interactions of SPS isolated from Klebsiella strains K20 and K51 with cationic dyes pinacyanol chloride (PCYN) and acridine orange (AO) were studied by absorbance and fluorescence measurements. Both the polysaccharides having glucuronic acid as the potential anionic site induced strong metachromasy (blue shift approximately 100 nm) in the PCYN. The spectral changes were studied at different polymer/dye molar ratios (P/D = 0-40). A complete reversal of metachromasy was observed upon addition of co-solvents, suggesting the breakaway of dye molecules from the biopolymer matrix. Binding constant, changes in free energy, enthalpy and entropy of the dye polymer complex were also computed from the spectral data at different temperatures to reveal the nature of the interaction. Quenching of fluorescence of AO by the polymers and the incorporated mechanisms were also explored.
authors.affiliation: Department of Chemistry, Tripura University, Suryamaninagar, Tripura 799 130, India.
authors.forename: S
authors.initials: S
authors.lastname: Dasgupta
authors.forename: R K
authors.initials: RK
authors.lastname: Nath
authors.forename: S
authors.initials: S
authors.lastname: Biswas
authors.forename: A
authors.initials: A
authors.lastname: Mitra
authors.forename: A K
authors.initials: AK
authors.lastname: Panda
mesh_terms: D000042:Absorption / Q000187:drug effects; D000165:Acridine Orange / Q000378:metabolism*; D002232:Carbocyanines / Q000378:metabolism*; D004396:Coloring Agents / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D007709:Klebsiella / Q000737:chemistry*; D011135:Polysaccharides, Bacterial / Q000302:isolation & purification / Q000378:metabolism*; D013057:Spectrum Analysis; D013696:Temperature; D013816:Thermodynamics
chemical_list: D002232:Carbocyanines; D004396:Coloring Agents; D011135:Polysaccharides, Bacterial; D000431:Ethanol; C019071:quinaldine blue; D000165:Acridine Orange