title: Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening.
abstract: Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K(+) and I(-) ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.e., helix content θ > 0.30, the effect of chain stiffening, accompanied with a rapid increase in helix length ζ, becomes dominant and tends to dissociate the electrostatic complexation. The effect of chain stiffening can be theoretically interpreted in terms of double helix association.
authors.affiliation: Glyn O. Phillips Hydrocolloid Research Centre, School of Food and Pharmaceutical Engineering, Faculty of Light Industry, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Yiping
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Glyn O. Phillips Hydrocolloid Research Centre, School of Food and Pharmaceutical Engineering, Faculty of Light Industry, Hubei University of Technology, Wuhan 430068, China.|Hubei Collaborative Innovation Centre for Industrial Fermentation, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Yapeng
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Glyn O. Phillips Hydrocolloid Research Centre, School of Food and Pharmaceutical Engineering, Faculty of Light Industry, Hubei University of Technology, Wuhan 430068, China.|Hubei Collaborative Innovation Centre for Industrial Fermentation, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Nishinari
authors.affiliation: Glyn O. Phillips Hydrocolloid Research Centre, School of Food and Pharmaceutical Engineering, Faculty of Light Industry, Hubei University of Technology, Wuhan 430068, China.
authors.forename: Glyn O
authors.initials: GO
authors.lastname: Phillips
mesh_terms: D000838:Anions; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002351:Carrageenan / Q000737:chemistry*; D002414:Cations, Monovalent; D005780:Gelatin / Q000737:chemistry*; D000071228:Polyelectrolytes / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry*; D011485:Protein Binding; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012996:Solutions; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D000838:Anions; D002414:Cations, Monovalent; D000071228:Polyelectrolytes; D000644:Quaternary Ammonium Compounds; D012996:Solutions; D011189:Potassium Chloride; D002351:Carrageenan; D005780:Gelatin; C027917:tetramethylammonium