Biomedical Engineering Reference
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Fig. 11.4
Reporter gene technology for whole-cell olfactory biosensor using fluorescence and
bioluminescence.
a
An analyte or a stimulus i.e odorant specifically activates a regulatory gene
sequence via signal transduction that controls the reporter gene expression and the synthesis of
the reporter protein, which is then measured by fluorescence or bioluminescence. (Reprinted from
Ref. [
65
] with permission from NPG).
b
Yeast cells containing rat ORs were used as a 2,4-dini-
trotoluene (DNT) detection. Schematic showing the construction of olfactory yeast strain WIF-
1α-RX. Transfection with a plasmid containing the GFP gene formed the WIF-1α strain, in which
GFP expression serves as a reporter.
c
Specificity of WIF-1α-ORI7 response. Cells were incubated
with hexanal (6-CHO), heptanal (7-CHO), octanal (8-CHO) or octanol (8-OH).
d
Response of
WIF-1α-Olfr226 strain to DNT. (Reprinted from Ref. [
66
] with permission from NPG)
the receptor level could be involved in the perceptual complexities seen in odorant
mixtures. This phenomenon, known as mixture suppression, has been verified in
behavioral experiments, as well as at the cellular and olfactory epithelial levels for
various OR [
43
,
48
,
60
,
61
].
11.2.2
Reporter Gene-based Selective Odorant Sensing
Reporter gene technology represents one of the major recent achievements in mo-
lecular biology. Reporter genes are DNA sequences that encode an easily detectable
protein or enzyme such as luciferase or GFP [
62
-
64
]. The rate of fluorescence and
bioluminescence output is directly proportional to the concentration of the indicator
material present. The principle of reporter gene technology applied to the develop-
ment of whole-cell olfactory biosensors is shown in Fig.
11.4
.
The cAMP responsive binding protein is a well-characterized transcription fac-
tor regulated by cAMP [
50
]. The transcription factor cAMP-responsive element
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