Mass Spectrometry Letters (Sep 2012)
Examination of Various Metal Ion Sources for Reducing Nonspecific Zinc finger−Zn2+ Complex Formation in ESI Mass Spectrometry
Abstract
The formation of zinc finger peptide−Zn2+ complexes in electrospray ionization mass spectrometry (ESI-MS) was examined using three different metal ion sources: ZnCl2, Zn(CH3COO)2, and Zn(OOC(CHOH)2COO). For the four zinc finger peptides (Sp1-1, Sp1-3, CF2II-4, and CF2II-6) that bind only a single Zn2+ in the native condition, electrospray of apo-zinc finger in solution containing ZnCl2 or Zn(CH3COO)2 resulted in the formation of zinc finger−Zn2+ complexes with multiple zinc ions. This result suggests the formation of nonspecific zinc finger−Zn2+ complexes. Zn(tartrate), Zn(OOC(CHOH)2COO),mainly produced specific zinc finger−Zn2+ complexes with a single zinc ion. This study clearly indicates that tartrate is an excellent counter ion in ESI-MS studies of zinc finger−Zn2+ complexes, which prevents the formation of nonspecific zinc finger−Zn2+ complexes.