期刊
ANALYTICAL CHEMISTRY
卷 85, 期 16, 页码 7826-7833出版社
AMER CHEMICAL SOC
DOI: 10.1021/ac401370t
关键词
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资金
- National Science Foundation [DBI-0821700, CHE-0541587]
- U.S. Department of Energy, Division of Chemical Sciences, Basic Energy Sciences [DE-FG02-04R15520]
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](2+), and these are assigned as the parallel beta-helix, antiparallel beta-helix, and head-to-head dimer. The monomerization kinetics and equilibrium abundances of the dimer ions depend upon solvent polarity. The antiparallel beta-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.
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