Selective C-I Bond Cleavage in ECD: Prospects for Designing Novel Chemical Cross-linker and Mechanistic Implications

摘要

A series of peptides were iodinated. In the case of MSH, His and Tyr can be selectively iodinated by varying the initial reaction conditions. For all iodinated peptides, C-I bond cleavage was observed in both ECD and ETD but with various efficiencies. A proximate positive charge, either through bond or through space, appears to facilitate efficient C-I bond cleavage. ECD and ETD of triply protonated singly iodinated MSH on the same instrument (solariX FT-ICR MS) generate consistent ILE values with those from an Apex FT-ICR MS. ETD tends to result in less peptide backbone fragmentation, corresponding to higher ILEs than the corresponding values from ECD. These results provide a guide to designing novel cross-linkers and an additional model for understanding ECD/ETD mechanisms.