Revealing Anisotropic Growth of Liraglutide Oligomers by Native Ion Mobility Mass Spectrometry and Molecular Dynamics Simulation

Oligomerization is an intriguing problem, particularly at the early stages of precursor formation, where the mechanisms of oligomer growth are difficult to study due to their complexity and heterogeneity. Liraglutide, a widely used drug for diabetes and obesity, has demonstrated various oligomerization outcomes across different studies. In this study, we integrate native ion mobility mass spectrometry (nIM-MS) and molecular dynamics (MD) simulations to unravel the assembly mechanisms of liraglutide oligomers. Our findings reveal that while assembly pathways vary in their steps, they consistently converge into a structure resembling a fuzzy oil drop model. Furthermore, a key residue is identified as a determining factor in oligomerization. The preference for specific shapes varies at different stages of oligomer formation, depending on the oligomer size. A theoretical model is proposed to fit collisional cross-section (CCS) data and is verified through both nIM-MS experiments and MD simulations, ultimately establishing an anisotropic growth mechanism for liraglutide. Additional MD simulations provide deeper insights into monomer conformations, which are closely linked to oligomer formation. A bias toward forming extended conformers is shown to facilitate assembly of larger oligomers in this self-assembling system.