title: Interaction of lysozyme with negatively charged flexible chain polymers.
abstract: The complex formation between the basic protein lysozyme and anionic polyelectrolytes: poly acrylic acid and poly vinyl sulfonic acid was studied by turbidimetric and isothermal calorimetric titrations. The thermodynamic stability of the protein in the presence of these polymers was also studied by differential scanning calorimetry. The lysozyme-polymer complex was insoluble at pH lower than 6, with a stoichiometric ratio (polymer per protein mol) of 0.025-0.060 for lysozyme-poly vinyl sulfonic acid and around 0.003-0.001 for the lysozyme-poly acrylic acid. NaCl 0.1M inhibited the complex precipitation in agreement with the proposed coulombic mechanism of complex formation. Enthalpic and entropic changes associated to the complex formation showed highly negative values in accordance with a coulombic interaction mechanism. The protein tertiary structure and its thermodynamic stability were not affected by the presence of polyelectrolyte.
authors.affiliation: Bioseparation Lab, Physical-Chemistry Department, Faculty of Biochemical and Pharmaceutical Sciences, National University of Rosario, FonCyT, CIUNR and CONICET, Suipacha 570, S2002RLK, Rosario, Argentina. dianaromanini@hotmail.com
authors.forename: Diana
authors.initials: D
authors.lastname: Romanini
authors.forename: Mauricio
authors.initials: M
authors.lastname: Braia
authors.forename: Rodrigo Giatte
authors.initials: RG
authors.lastname: Angarten
authors.forename: Watson
authors.initials: W
authors.lastname: Loh
authors.forename: Guillermo
authors.initials: G
authors.lastname: Picó
mesh_terms: D000179:Acrylates / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D011232:Chemical Precipitation; D004527:Egg Proteins / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D009391:Nephelometry and Turbidimetry; D011092:Polyethylene Glycols / Q000737:chemistry; D011100:Polyglycolic Acid / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry; D011485:Protein Binding; D012995:Solubility / Q000187:drug effects; D013816:Thermodynamics
chemical_list: D000179:Acrylates; D004527:Egg Proteins; D046911:Macromolecular Substances; D011108:Polymers; D011145:Polyvinyls; D011100:Polyglycolic Acid; D011092:Polyethylene Glycols; D009113:Muramidase; C036658:acrylic acid