Influence of Temperature and Osmolytes on Conformational Dynamics of Alpha Synuclein.

Alpha-synuclein (α-syn) is an intrinsically disordered protein (IDP) associated with amyloid formation in neurodegenerative diseases, including Parkinson's, dementia with Lewy bodies, and multiple system atrophy. Disease progression is linked to the transition of α-syn from native to misfolded conformations, although the mechanisms underlying this process remain unclear. An effective method for investigating protein dynamics is native mass spectrometry, specifically when coupled with ion mobility-mass spectrometry (IM-MS) to examine differences in the shape and size of various analytes. In this study, variable-temperature electrospray ionization ion mobility-mass spectrometry (vT-ESI-IM-MS) was used to investigate the conformational dynamics of wild-type and A30P α-syn in the presence and absence of five osmolytes trimethylamine-N-oxide (TMAO), urea, guanidine, 1-dodecylguanidine (dodine), and arginine. For both α-syn variants, the abundance of extended conformers increased with temperature in the absence of osmolytes, consistent with temperature-dependent conformational shifts. This study shows osmolytes significantly alter conformational distributions and temperature-dependent responses, with dodine promoting extended conformations and guanidine producing the lowest abundance of extended states. These results demonstrate the utility of vT-ESI-IM-MS for probing IDP dynamics and highlight the influence of osmolytes on IDP conformational behavior.