Time- and pH-Dependent Copper Binding to Aβ(1-16) Peptide: An Electrospray Ionization-Mass Spectrometric Approach

An elevated concentration of copper ions in the brain of Alzheimer's disease patients has been reported in many studies and might be associated with an increased aggregation of beta-amyloid (A beta) peptides. In the present work, the interaction with copper ions of a model beta-amyloid peptide, A beta(1-16), was investigated by electrospray ionization-mass spectrometry (ESI-MS) at two pH values, 7.4 and 6.6, as well as at various peptide: copper ion ratios in the first minutes after components mixing and time intervals. Our results indicated that copper ions specifically bound to A beta(1-16) peptide in solution and that the complex formation increased with time. Once formed in solution, Cu2+-A beta(1-16) complexes could easily be detected in the gas phase by ESI-MS. The pH shift from 7.4 to 6.6 only slightly influenced the Cu2+ binding to A beta(1-16). No oligomerization of A beta(1-16) peptide was noticed in the first minutes of copper-peptide interaction.