Abstract by Andrew Arslanian
Chemistry and Biochemistry
Comparison of Leucine-enkephalin Precursor and Product Ion Conformations in the Same Experiment
Peptides are small biomolecules composed of amino acids. Mass spectrometry is often used to characterize peptide primary structure by identifying the mass-to-charge ratio (m/z), which results in likely molecular formulas, and allowing ion-neutral collisions, which fragment the peptide to determine amino acid connectivity. A unique ability of Fourier transform ion cyclotron resonance mass spectrometers is the ability to characterize secondary and tertiary structure through ion-neutral collision cross-section measurement. The above techniques were used to characterize protonated and alkali metallated (Li+, Na+, etc) leucine-enkephalin (LE) and their fragmentation products. While LE+H+ fragmentation leads to bn and an fragments, fragmentation of LE+Li+ leads to bn+17 and an-1 fragments. Cross-section measurements reveal conformational details that account for the change in fragmentation products when LE is metallated instead of protonated. LE+M+ adopts a more compact conformation than LE+H+, which stabilizes LE during ion-neutral collisions and leads to hydroxy transfer (+17) from the original c-terminus to the c-terminus of the bn fragment.