Surface Effects of Iron Oxide Nanoparticles on the MALDI In-Source Decay Analysis of Glycans and Peptides

Inorganic nanoparticles as MALDI matrices have recently been explored to study the molecular mass determination and structural analysis of glycans and peptides. However, the specific factors contributing to the success of the analysis are not well elucidated. In this paper, we investigated the roles of nanoparticle surface coatings and additive ions in MALDI in-source decay (ISD) analysis of model glycans and peptides. Specifically, iron oxide nanoparticles with four defined capping molecules (gluconic acid, citric acid, lactobionic acid, or glutathione) were tested, and the roles of additives (NH₄OH, NaOH, LiOH, NaCl, or trifluoroacetic acid) were examined. For a model glycan, maltoheptaose, and a model peptide, substance P acid, nanoparticle capping molecules, additive cations, and additive anions altogether influenced the molecular ion sensitivity and ISD fragmentation efficiency.