title: The role of protonation in protein fibrillation.
abstract: Many proteins fibrillate at low pH despite a high population of charged side chains. Therefore exchange of protons between the fibrillating peptide and its surroundings may play an important role in fibrillation. Here, we use isothermal titration calorimetry to measure exchange of protons between buffer and the peptide hormone glucagon during fibrillation. Glucagon absorbs or releases protons to an extent which allows it to attain a net charge of zero in the fibrillar state, both at acidic and basic pH. Similar results are obtained for lysozyme. This suggests that side chain pK(a) values change dramatically in the fibrillar state.
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Centre, University of Aarhus, Aarhus C, Denmark.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Jeppesen
authors.forename: Peter
authors.initials: P
authors.lastname: Westh
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Otzen
mesh_terms: D002021:Buffers; D002151:Calorimetry; D002942:Circular Dichroism; D005934:Glucagon / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D009113:Muramidase / Q000737:chemistry; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics; D017186:Titrimetry
chemical_list: D002021:Buffers; D011506:Proteins; D011522:Protons; D005934:Glucagon; D009113:Muramidase