Biomedical Engineering Reference
In-Depth Information
Chapter 11
Optical Methods in Studies of Olfactory System
Sang Hun Lee, Seung-min Park and Luke P. Lee
Abstract
The olfactory receptor (OR) comprises the largest multi-gene G pro-
tein-coupled receptor (GPCR) family by playing a critical role in recognizing
thousands of odorant molecules. Odorant-OR pairs have been characterized using
various functional assays, and have provided an understanding of molecular basis
in olfaction as well as characterizing specificity between agonist and antagonist.
This chapter introduces the most commonly employed, labeled or label-free optical
techniques employed to identify the odorant-OR pairs on a cellular and molecu-
lar level, and reviews recent developments in odorant binding assays to ORs with
optical methods such as Ca
2+
imaging, reporter-gene technology, surface plasmon
resonance (SPR) and so on. For OR and GPCR study, a set of optical technologies
including—but not limited to—Raman spectroscopy, photonic crystal, and total
internal reflection (TIR) are also discussed in an analytical science point of view.
11.1
Molecular and Neural Basis of Olfaction
11.1.1
Olfactory System
Landmark discovery of the gene family encoding vertebrate olfactory receptors
(ORs) in rats by Buck and Axel has led to a detailed understanding of the molecular
and neurological bases in the olfaction [
1
]. The initial steps in an olfaction take
place in olfactory sensory neurons located in the olfactory epithelium inside the
nasal cavity. These neurons are responsible for the detection of odorants and the
generation of the neural signal that is transmitted to the brain via olfactory bulb as
shown in Fig.
11.1
. Based on this process, the olfactory sensory system can detect
thousands of different single and mixed odorants. For many organisms, the olfac-
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