title: Early stage aggregation of human serum albumin in the presence of metal ions.
abstract: The heat induced aggregation of human serum albumin (HSA) with and without an equimolar amount of Cu(II) and Zn(II) was investigated by using optical absorption, fluorescence, AFM and EPR spectroscopy. Turbidity experiments as a function of temperature indicate that the protein aggregation occurs after the melting of the protein. The kinetic of HSA aggregation, investigated between 60 and 70°C by monitoring the optical density changes at 400nm on a 180min time window, shows an exponential growth with a rate that increases with the temperature. Fluorescence of the thioflavin T evidences a significant increase of the intensity at 480nm at increasing incubation time. These results combined with AFM experiments show that the protein aggregates are elongated oligomers with fibrillar-like features. The absence of a lag-phase suggests that the early stage aggregation of HSA follows a downhill pathway that does not require the formation of an organized nucleus. The presence of Cu(II) and Zn(II) ions does not affect the thermally induced aggregation process and the morphology of HSA aggregates. The result is compatible with the binding of the metal ions to the protein in the native state and with the high conformational stability of HSA.
authors.affiliation: Department of Physics, University of Calabria, 87036 Rende, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Stirpe
authors.forename: Manuela
authors.initials: M
authors.lastname: Pantusa
authors.forename: Bruno
authors.initials: B
authors.lastname: Rizzuti
authors.forename: Luigi
authors.initials: L
authors.lastname: Sportelli
authors.forename: Rosa
authors.initials: R
authors.lastname: Bartucci
authors.forename: Rita
authors.initials: R
authors.lastname: Guzzi
mesh_terms: D000818:Animals; D002417:Cattle; D003300:Copper / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018625:Microscopy, Atomic Force; D055620:Optical Phenomena; D055503:Protein Multimerization / Q000187:drug effects*; D017433:Protein Structure, Secondary; D012709:Serum Albumin / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D015032:Zinc / Q000494:pharmacology*
chemical_list: D012709:Serum Albumin; D003300:Copper; D015032:Zinc