An Experimental Study of the Solvent-Dependent Self-Assembly/Disassembly and Conformer Preferences of Gramicidin A Liuxi Chen Shu-Hua Chen David H. Russell 10.1021/ac401370t.s001 https://acs.figshare.com/articles/journal_contribution/An_Experimental_Study_of_the_Solvent_Dependent_Self_Assembly_Disassembly_and_Conformer_Preferences_of_Gramicidin_A/2384863 The solvent dependence of self-assembly/disassembly kinetics and conformer preferences of the gramicidin A (GA) dimer is investigated using a combination of techniques, viz., electrospray ionization–ion mobility–mass spectrometry (IM-MS), collision-induced dissociation (CID), and hydrogen/deuterium exchange (HDX)-MS. IM-MS measurements reveal that there are possibly three distinct GA dimeric species, detected as sodium ion adduct ions [2GA + 2Na]<sup>2+</sup>, and these are assigned as the parallel β-helix, antiparallel β-helix, and head-to-head dimer. The monomerization kinetics and equilibrium abundances of the dimer ions depend upon solvent polarity. The antiparallel β-helix was the thermodynamically preferred species in less polar solvents. HDX measurements and collision-induced dissociation (CID) of the intermediate complex confirm the well-protected dimer geometry with strong intermolecular hydrogen bonds. This combined IM-HDX-CID methodology provides a comprehensive view of GA self-assembly/disassembly in low dielectric solutions, showing its potential utility in solving solution-phase protein self-assembly/disassembly kinetics and providing structural information of the multimers at the same time. 2013-08-20 00:00:00 dielectric solutions HDX measurements GA dimeric species dissociation dimer ions conformer preferences helix monomerization kinetics CID Conformer Preferences Experimental Study antiparallel hydrogen bonds equilibrium abundances Gramicidin AThe