Proposed Modifications to MALDI-CID Fragmentation Mechanisms of Silver Ionized Polystyrene Oligomers

摘要

The MALDI-CID of polystyrene has been thoroughly investigated by A.T. Jackson and co-workers [1-3]. Abundant A and B series distonic ion fragments with low m/z values contain the terminating and initiating end groups, respectively. They are reasonably attributed to arise via homolytic cleavage of polystyrene backbone bonds followed by rapid depolymerization. However, less intense terminating (alpha), D, F and initiating (beta), C, E fragment ion series are proposed to originate from mechanisms invoking improbable 1,5-hydrogen rearrangement reactions. Intense low mass G series fragment peaks contain neither chain end. This study presents alternative dissociation mechanisms based upon typical free radical reactions which more rationally explain MALDI-CID spectral data, indicating that currently accepted mechanistic schemes are incorrect.