Dimerization of Peptides by Calcium Ions: Investigation of a Calcium-Binding Motif

We investigated calcium-binding motifs of peptides and their recognition of active functionalities for coordination. This investigation generates the fundamentals to design carrier material for calcium-bound peptide-peptide interactions. Interactions of different peptides with active calcium domains were investigated. Evaluation of selectivity was performed by electrospray ionization mass spectrometry by infusing solutions containing two different peptides (P 1 and P 2 ) in the presence of calcium ions. In addition to signals for monomer species, intense dimer signals are observed for the heterodimer ions (P 1 ⋯ Ca 2+ ⋯ P 2 ) (⋯ represents the noncovalent binding of calcium with the peptide) in the positive ion mode and for ions ([P 1 -2H] 2− ⋯ Ca 2+ ⋯ [P 2 -2H] 2− ) in the negative ion mode. Monitoring of the dissociation from these mass selected dimer ions via the kinetic method provides information on the calcium affinity order of different peptide sequences.