Studies on the Interaction of Klebsiella K34 Capsular Polysaccharide with Oppositely Charged Dyes and Surfactants

Spectral studies on the interaction of capsular polysaccharide (SPS) isolated from Klebsiella serotype K34, with oppositely charged dyes and surfactants have been reported. The SPS was acidic in nature and induced strong metachromacy (~110 nm blue shift) in the cationic dye pinacyanol chloride (PCYN) which was due to “card-pack stacking” of individual dye monomers on the surface of the polyanions. Reversal of metachromacy offered a qualitative measurement of stability and nature of binding associated with PCYN-SPS complex. Thermodynamic parameters of dye-polymer complex were evaluated. SPS – cationic dye acridine orange (AO) interaction in aqueous solution have been investigated fluorimetrically. Dye incorporation technique was employed to study cationic surfactant–polymer interactions. Interactions between the polyelectrolyte and oppositely charged surfactants lead to the formation of induced premicelles at surfactant concentrations lower than the CMC of the surfactants and the corresponding binding constant was evaluated. Such studies revealed that the surfactant is not exclusively bound electrostatically, but also through hydrophobic interactions.