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Title: Biochemical sensing mechansims in olfaction
Author: Wood, Philip Howard
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1985
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The present work, employing biochemical, biophysical and electrophysiological techniques, attempted to identify specific receptor sites in the vertebrate olfactory system for heterocyclic odorants. An in vitro rat preparation was developed and characterised for use in vapour-phase chemical modification experiments; the EOG responses obtained from this preparation were stable for up to 5 hours after the death of the animal. The signals to various compounds were differentially reduced when brominated odorants were employed as vapour-phase labelling reagents; the responses obtained to these derivatives and to their non-reactive analogues were preferentially diminished. The effect of concanavalin A on ECGs obtained from an in vivo frog preparation was examined. This lectin was found to preferentially inhibit the signals elicited by small, sweaty-smelling carboxylic acids; the responses to most of the non-carboxylic acid odorants tested were not significantly inhibited. The failure to identify specific receptor sites by electrophysiological techniques prompted the performance of odorant binding studies. Examinations of the interaction of [3H] 2-isobutyl-3- methoxypyrazine with 13,000 x g supernatant fractions of sheep olfactory epithelium showed that a component of the homogenate fraction exhibited high affinity saturable binding of this odorant (KD-10-8M). However, the presence of large amounts of non-specific binding, substantially decreased the sensitivity and accuracy of the assay. Non-specific binding was observed with tissue fractions of sheep respiratory epithelium, brain and liver. An investigation of binding specificity showed that other bell pepper odorants competed for the 2-iscbutyl-3-methoxypyrazine binding site. The steno requirements for the protein binding of various substituted heterocyclic odorants were examined using nuclear magnetic relaxation techniques. Model studies performed with bovine serum albumin showed that particular side chains of the odorants tested were primarily involved in the binding interaction. The methoxy group of 2-isopropyl-3-methoxypyrazine was found to be responsible for primary recognition by 13,000 x g supernatant fractions of sheep olfactory epithelium.
Supervisor: Not available Sponsor: Medical Research Council (Great Britain) (MRC) ; Royal Society (Great Britain)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH Natural history ; QP Physiology