Neurotransmitters are specific molecules involved in the transmission of neural signals between neurons. The study of the shape of neurotransmitters and their most essential precursors is of great relevance to biochemistry since it plays a key role in the molecular recognition process at the receptor site. We here report the first rotational study of neutral levodopa, an aminoacid precursor of neurotransmitters dopamine [1], adrenaline and noradrenaline using a combination of broadband chirped pulse FTMW spectroscopy and a laser ablation vaporization system (LA-CP-FTMW). Three distinct conformers of levodopa have been unambiguously identified in the supersonic jet. Also, we have analyzed the ¹⁴N nuclear quadrupole hyperfine structure to identify and experimentally establish the intramolecular interactions in which the N-bearing functional group is involved, showing the existence of stabilizing N-H-π interactions for the observed structures.

Acknowledgments: The authors thank the financial fundings from Ministerio de Ciencia e Innovación (CTQ2016- 76393-P and PID2019-111396GB-I00), Junta de Castilla y Leon (VA077U16 and VA244P20) and European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC-2013-SyG, Grant Agreement n. 610256 NANOCOSMOS, are gratefully acknowledged. E.R.A. acknowledges MINECO for a Juan de la Cierva postdoctoral fellowship and the Fundación Biofísica Bizkaia (Spain). M.S.N. acknowledges funding from the Spanish ”Ministerio de Ciencia, Innovacion y Universidades” under predoctoral FPU Grant (FPU17/02987).

[1] C. Cabezas, I. Pena, J. C. Lopez and J. L. Alonso, J. Phys. Chem. Lett., 2013, 4, 486–490.