title: Competing Insertion and External Binding Motifs in Hydrated Neurotransmitters: Infrared Spectra of Protonated Phenylethylamine Monohydrate.
abstract: Hydration has a drastic impact on the structure and function of flexible biomolecules, such as aromatic ethylamino neurotransmitters. The structure of monohydrated protonated phenylethylamine (H(+) PEA-H2 O) is investigated by infrared photodissociation (IRPD) spectroscopy of cold cluster ions by using rare-gas (Rg=Ne and Ar) tagging and dispersion-corrected density functional theory calculations at the B3LYP-D3/aug-cc-pVTZ level. Monohydration of this prototypical neurotransmitter gives an insight into the first step of the formation of its solvation shell, especially regarding the competition between intra- and intermolecular interactions. The spectra of Rg-tagged H(+) PEA-H2 O reveal the presence of a stable insertion structure in which the water molecule is located between the positively charged ammonium group and the phenyl ring of H(+) PEA, acting both as a hydrogen bond acceptor (NH(+) ⋅⋅⋅O) and donor (OH⋅⋅⋅π). Two other nearly equivalent isomers, in which water is externally H bonded to one of the free NH groups, are also identified. The balance between insertion and external hydration strongly depends on temperature.
authors.affiliation: Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany.
authors.forename: Aude
authors.initials: A
authors.lastname: Bouchet
authors.affiliation: Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany.
authors.forename: Markus
authors.identifier: http://orcid.org/0000-0002-3773-6009
authors.initials: M
authors.lastname: Schütz
authors.affiliation: Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany. dopfer@physik.tu-berlin.de.
authors.forename: Otto
authors.identifier: http://orcid.org/0000-0002-9834-4404
authors.initials: O
authors.lastname: Dopfer
mesh_terms: D018377:Neurotransmitter Agents / Q000737:chemistry*; D010627:Phenethylamines / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D014867:Water / Q000737:chemistry*
chemical_list: D018377:Neurotransmitter Agents; D010627:Phenethylamines; D011522:Protons; D014867:Water
keywords: conformation analysis; hydrates; hydrogen bonds; neurotransmitters; protonation