Synthesis of novel photoprobes for mapping of the serotonin 5-HT3 receptor binding site
Hallaq, Hasan Y. (2012) Synthesis of novel photoprobes for mapping of the serotonin 5-HT3 receptor binding site. PhD thesis, University of Warwick.Full text not available from this repository.
Official URL: http://webcat.warwick.ac.uk/record=b2584803~S1
The 5-HT3 receptor is phylogenetically the oldest of all the ligand-gated ion channel receptors, yet little information is known about its structure at the atomic level and no crystal structure has been solved. Most of the information gathered on the 5-HT3 receptor structure is largely derived from homology models of high resolution structures of nicotic acetylcholine binding protein and engineered nicotinic acetylcholine receptor subunits. Post-photoaffinity labelling modification (PPALM) is a technique that allows the mapping of the receptor binding site by screening various photoaffinity-tagged antagonists (PPALM reagent) and identifying the sequence of ligand-bound peptides from the analysed receptor-ligand complex.
A convergent synthetic approach was used in order to construct and conjugate a high affinity 5-HT3 antagonist granisetron, the trifluorophenyldiazirine (TPD) photogroup and the disulfide-linked tether. 5-, 6-, 7- and N-9- methoxy-, hydroxy- and benzyloxy-granisetron derivatives were synthesized and tested (against radiolabelled granisetron) for their binding affinity (Ki) to human 5-HT3A receptors to find the ideal tethering positions for attachment of the tether and the TPD photogroup. The 7-Bn-granisetron was found to have the highest binding affinity i.e. the lowest Ki value (0.2 nM) and was chosen as scaffold for the successful synthesis of the PPALM reagent.
Overall 16 novel antagonists were synthesised and tested with 7 of them having a Ki below 25 nM (Graph 1). The 7-substituted-granisetron derivatives were generally found to have the lowest set of Ki values even with bulky groups such as the 7-Bn (0.7 nM) and 7-TPD (13.5 nM) further supporting the group B model proposed by Thompson et al., 2005 and Maksey et al., 2003 that the aromatic rings of granisetron are positioned between Trp-183 and Tyr-234 in the 5-HT3 binding site.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QD Chemistry
Q Science > QP Physiology
|Library of Congress Subject Headings (LCSH):||Photoaffinity labeling, Binding sites (Biochemistry), Ion channels|
|Institution:||University of Warwick|
|Theses Department:||Department of Chemistry|
|Extent:||275 leaves : illustrations|
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