Spektroskopie der Neurotransmitter Tryptamin und Phenylethylamin

The maintenance of bodily functions in living beings is determined by a variety of biochemical processes, collectively referred to as metabolism. Molecular spectroscopy can be used to study processes at the molecular level and to draw conclusions about interactions and possible functionalities. The signal transmission between chemical neurons is based inter alia on the binding of a neurotransmitter (NT) to a receptor, wherein the molecular recognition, following the key-and-lock principle, is based on noncovalent interactions. The intra- and intermolecular interactions allow for a certain structural diversity and, depending on the conformer, a NT binds to a specific receptor. In general, different charge states of the involved molecules play a role in biochemical processes, so that the elucidation of the molecular conformation in these states leads to a fundamental understanding of the biological processes at the molecular level. In this dissertation, the neurotransmitters tryptamine (TRA) and phenylethylamine (PEA) are investigated by means of infrared spectroscopy in different charge states (neutral, cationic and protonated). In particular, the influence of solvents is analyzed, such as the interaction of TRA and PEA with one or more polar and nonpolar molecules. Another focus is on the study of fluorinated PEA. Fluorine substitution of molecules is a powerful tool in bioorganic and pharmaceutical applications to influence physiochemical and pharmacological properties. The isolated characterization in the gas phase allows to investigate a molecule free of any solvents but also the controlled stepwise solvation of the molecule. Infrared spectroscopy, in combination with mass spectrometry and supported by quantum chemical calculations, provides access to the molecular structure based on the obtained vibrational information. The results in this work illustrate the considerable influence of the charge state on the conformation of TRA and PEA as well as their interaction with polar and nonpolar molecules. Basically, it is shown that for both TRA and PEA, the number of experimentally detected conformers in the cationic and protonated states is significantly reduced compared to the neutral state. The picture is not the same for the two biomolecules. A structure predicted by theory for both molecules in the cationic state, in which the amino group of the side chain covalently binds to the aromatic ring, can experimentally only be detected for PEA. The solvation for the cationic TRA starts at the indolic NH group and continues for the polar H2O with forming a water network and for the nonpolar N2 with weak pi bonded motifs. A similar picture emerges for cationic PEA, but by interaction with the amino group of the side chain and the pi electron system. Both TRA and PEA protonate at the side chain to form an ammonium group around which solvation takes place. For the investigated fluorination of protonated PEA, in particular, the ortho position at the aromatic ring plays a predominant role for the molecular level structure, as a result of NH+...pi and NH+...F interactions.

Author dc:creator

• Schütz, Markus

Advisor dc:contributor.advisor

• Dopfer, Otto

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

de

Identifier URI

http://dx.doi.org/10.14279/depositonce-6874

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/7696