title: Sodium chloride enhances the storage and conformational stability of BDNF and PEG-BDNF.
abstract: OBJECTIVE
  BDNF, a noncovalent homodimer, was modified by covalently attaching polyethylene glycol (PEG) with an average molecular weight of 20kDa to the N-terminal methionine. Stability of modified BDNF (PEG-BDNF) in aqueous solution was compared to BDNF after storage at elevated temperature in the presence and absence of NaCl.
  
  
  METHODS
  SDS-PAGE. Light Scattering and Size Exclusion Chromatography were used to assess conformational stability and chemical degradation. In addition, CD spectroscopy was used to follow changes in secondary and tertiary structures upon thermal stress of the protein.
  
  
  RESULTS
  NaCl containing formulations are more stable than NaCl-free formulations. In NaCl-free formulations, the main degradation product of BDNF and PEG-BDNF had a molecular weight of monomer that was more chemically degraded than the dimer. Additionally, the degradation of PEG-BDNF occurred at an accelerated rate compared to BDNF in NaCl-free environments.
  
  
  CONCLUSIONS
  The addition of NaCl to formulations enhances the shelf-life and conformational stability of both BDNF and PEG-BDNF.
authors.affiliation: Department of Pharmaceutics, Amgen, Inc, Thousand Oaks, California 91320, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: Callahan
authors.forename: L O
authors.initials: LO
authors.lastname: Narhi
authors.forename: A A
authors.initials: AA
authors.lastname: Kosky
authors.forename: M J
authors.initials: MJ
authors.lastname: Treuheit
mesh_terms: D019208:Brain-Derived Neurotrophic Factor / Q000737:chemistry*; D002942:Circular Dichroism; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D005079:Excipients; D007700:Kinetics; D008968:Molecular Conformation; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000737:chemistry; D011487:Protein Conformation; D012542:Scattering, Radiation; D012965:Sodium Chloride / Q000737:chemistry*
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D005079:Excipients; D011092:Polyethylene Glycols; D012965:Sodium Chloride