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The native-like structures of protonated glycine and peptide Gly3H+ were elucidated using cold ion IR spectroscopy of these biomolecules hydrated by a controlled number of water molecules. The complexes were generated directly from an aqueous solution using gentle electrospray ionization. Already with a single retained water molecule, GlyH+ exhibits the native-like structure characterized by a lack of intramolecular hydrogen bonds. We use our spectra to calibrate the available data for the same complexes, which are produced by cryogenic condensation of water onto the gas-phase glycine. In some conformers of these complexes, GlyH+ adopts the native-like structure, while in the others, it remains “kinetically” trapped in the intrinsic state. Upon condensation of 4–5 water molecules, the embedded amino acid fully adopts its native-like structure. Similarly, condensation of one water molecule onto the tripeptide is insufficient to fully eliminate its kinetically trapped intrinsic states.
Richard Gaal, Livia Eleonora Bove Kado, Umbertoluca Ranieri
Natalia Nagornova, Andrei Zviagin, Ruslan Yamaletdinov, Manuel Dömer