Hydration of Guanidinium Ions: An Experimental Search for Like-Charged Ion Pairs.
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Guanidinium ions (GdmH+) are reported to form stable complexes (GdmH+/GdmH+) in aqueous solution despite strong repulsive interactions between the like-charged centers. These complexes are thought to play important roles in protein folding, membrane penetration, and formation of protein dimers. Although GdmH+ ions are weakly hydrated, semiempirical calculations provide evidence that these like-charged complexes are stabilized by water molecules, which serve important structural and energetic roles. Specifically, water molecules bridge between the GdmH+ ions of GdmH+/GdmH+ complexes as well as complexes involving the guanidinium side chains of arginine. Potential biological significances of like-charged complexes have been largely confirmed by ab initio molecular dynamics simulations and indirect experimental evidence. We report cryo-ion mobility-mass spectrometry results for the GdmH+/GdmH+ ion pair confined in a nanodroplet- the first direct experimental observation of this like-charged complex. A second like-charged complex, described as a water-mediated complex involving GdmH+ and H3O+, was also observed.
author list (cited authors)
Hebert, M. J., & Russell, D. H.
complete list of authors
Hebert, Michael J||Russell, David H