PNNL

Abstract

Nicotine (NIC) is an agonist of nicotinic acetylcholine receptors and causes both addiction and related health problems. NIC is protonated in physiological condition and its recognition in the receptor is strongly affected by protonated positions (the Pyrrolidine (Pyrro-NICH+) and the Pyridine (Pyri-NICH+) nitrogen atoms). Pyrro-NICH+ is dominant in aqueous solution while it turns to mixture of Pyrro- and Pyri-NICH+ in gas phase. Recently it is found that the NICH+ binding protein traps NICH+ together with a single water, however protonated position of NICH+ is not clear. Here, we have applied the temperature-controlled double ion trap infrared spectroscopy assisted by collisional stripping method and high-level theoretical calculations to NICH+ and determined the protonated positions is strongly deviated to pyridine ring with a single water hydration. The protonated position of related molecule (NornicotineH+) with a single water hydration is also discussed.