title: Surfactant copolymers prevent aggregation of heat denatured lysozyme.
abstract: We investigated the ability of certain triblock copolymer surfactant poloxamers of the form polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO), to prevent formation of stable aggregates of heat denatured hen egg lysozyme. Differential scanning calorimetry (DSC) and synchrotron small angle x-ray scattering (SAXS) experiments were performed to study the thermodynamics and solution structures of lysozyme at temperatures between 20 and 90 degrees C in the presence and absence of poloxamers with various molecular weights (8.4-14.3 kDa), but similar hydrophile/hydrophobe (PEO:PPO) ratio of 80%. Poloxmer 188 was found to be very effective in preventing aggregation of heat denatured lysozyme and those functioned as a synthetic surfactant, thus enabling them to refold when the conditions become optimal. For comparison, we measured the ability of 8 kDa polyethylene glycol (PEG) to prevent lysozyme aggregation under same conditions. The results of these studies suggest that poloxamers are more efficient than PEG in preventing aggregation of heat denaturated lysozyme. To achieve equivalence, more than an order of magnitude higher concentration of PEG concentration was needed. Apparently, the presence of a hydrophobic segment in the poloxamers increases their ability to target the hydrophobic region of the unfolded proteins and protect them from self association. Given their biocompatibility and the low concentrations at which they effectively facilitate refolding of denatured proteins, they may be useful in the treatment of burns and other conditions resulting in the denaturation of proteins.
authors.affiliation: Department of Surgery, The University of Chicago, Chicago, IL 60637, USA. r-lee@uchicago.edu
authors.forename: Raphael C
authors.initials: RC
authors.lastname: Lee
authors.forename: Florin
authors.initials: F
authors.lastname: Despa
authors.forename: L
authors.initials: L
authors.lastname: Guo
authors.forename: Pravin
authors.initials: P
authors.lastname: Betala
authors.forename: Anne
authors.initials: A
authors.lastname: Kuo
authors.forename: P
authors.initials: P
authors.lastname: Thiyagarajan
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D009113:Muramidase / Q000737:chemistry*; D020442:Poloxamer / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: C116176:PEO-PPO-PEO; D011409:Propylene Glycols; D013501:Surface-Active Agents; D020442:Poloxamer; D011092:Polyethylene Glycols; D009113:Muramidase