Determination of a Binding Site of Cu and Ni Metal Ions with Oxytocin Peptide by Electrospray Tandem Mass Spectrometry and Multiple Mass Spectrometry

• DOI: 10.1255/ejms.977
• Publication Date: 2009-01-26T17:00:37Z
• Authors: Hye-Jin Jeong; Ho-Tae Kim
• Keywords: Solutions; 0301 basic medicine; Spectrometry, Mass, Electrospray Ionization; 03 medical and health sciences; Binding Sites; Molecular Structure; Cations, Divalent; Nickel; Tandem Mass Spectrometry; Water; Oxytocin; Copper

The structures of a [NiII, CuII—oxytocin] complex were investigated by electrospray ionization-mass spectrometry in positive mode. The fragmentation patterns of the [NiII, CuII + OT]2+ complex were analyzed by tandem mass spectrometry and multiple mass spectrometry in the gas-phase. Conformations of metalII ion binding to oxytocin (OT) have been studied to explain the biological activity difference in the physiological solution. The [NiII + OT]2+ and [CuII + OT]2+ complexes were observed as the main ions in MS spectra. The Cys1–Tyr2–Ile3–Gln4 sequence of oxytocin is suggested to be a binding site for the [NiII + OT]2+ gas-phase complex and Ile3–Gln4–Asn5–Cys6 sequence for the [CuII + OT]2+ gas-phase complex. The specific binding site of CuII ion in the [CuII + OT]2+ complex is explained as a reason of the negligible effect on the [CuII—oxytocin] biological activity in aqueous solution.