Collision-induced symmetric fission of doubly-charged cubelike [Fe4S4X4]2- clusters

A series of doubly-charged [4Fe4S] cluster ions, [Fe4S4X4](2-) (X = Cl, Br, I, and SCZHS), were produced in the gas phase by electrospray ionization and examined using collision-induced dissociation (CID) in a quadrupole ion trap. CID channels of each dianion were analyzed by MS/MS experiments at different collision energies. Two CID channels were observed for these dianions: symmetric fission and electron detachment. The most interesting observation is the symmetric fission of [Fe4S4X4](2-) into two identical daughter ions, [Fe2S2X2](-). The important role of the intramolecular coulomb repulsion in the symmetric fission was shown by comparing with CID of the singly-charged anions, [Fe4S4X4](-). Our gas-phase experiments suggest that solution phase conversions between [Fe4S4] and [Fe2S2] assemblies in proteins may also involve related fission chemistry with reactive [Fe2S2X2](-) intermediates. (C) 2003 Elsevier Science B.V All rights reserved.