The vibrational theory of olfaction was posited to explain subtle effects in the sense of smell inexplicable by models in which a molecular structure alone determines an odorant’s smell. Amazingly, behavioral and neurophysiological evidence suggests that humans and some insects can be trained to distinguish isotopologue molecules that are related by the substitution of isotopes for certain atoms, such as a hydrogen-to-deuterium substitution. How is it possible to smell a neutron? The physics of olfaction may explain this isotopomer effect. Inelastic electron transfer spectroscopy (IETS) has been proposed as a candidate mechanism for such subtle olfactory effects: the vibrational spectrum of an appropriately quantized odorant molecule may enhance a transfer rate in the discriminating electron transfer (ET) process. In contrast to other semiclassical or quantum-master-equation-based models of olfactory IETS, the model presented here explicitly treats the dynamics of a dominant odorant vibrational mode, which provides an indirect dissipative path from the electron to the thermal environment. A direct dissipative path to the environment is also included. Within this model, a calculation of the ET rate is developed, along with a calculation of power dissipation to the thermal environment. Under very weak direct dissipative coupling, spectroscopic behaviors of the indirect path are revealed, and the resulting ET rate exhibits resonant peaks at certain odorant frequencies. Resonant peaks in the ET rate also correlate to peaks in power dissipation. Spectroscopic behaviors are masked by strong direct dissipative coupling. Results support a rate-based discrimination between a preferred ligand and an isotopomer if indirect dissipative coupling dominates.

1.
A.
Keller
and
L.
Vosshall
, “
A psychophysical test of the vibration theory of olfaction
,”
Nat. Neurosci.
7
(
4
),
337
338
(
2004
).
2.
M.
Franco
,
L.
Turin
,
A.
Mershin
, and
E.
Skoulakis
, “
Molecular vibration-sensing component in Drosophila melanogaster olfaction
,”
Proc. Natl. Acad. Sci. U.S.A.
108
(
9
),
3797
3802
(
2011
).
3.
S.
Gane
,
D.
Georganakis
,
K.
Maniati
,
M.
Vamvakias
,
N.
Ragoussis
,
E.
Skoulakis
, and
L.
Turin
, “
Molecular vibration-sensing component in human olfaction
,”
PLoS One
8
(
1
),
e55780
(
2013
).
4.
E.
Block
,
S.
Jang
,
H.
Matsunami
,
S.
Sekharan
,
B.
Dethier
,
M.
Ertem
,
S.
Gundala
,
Y.
Pan
,
S.
Li
,
Z.
Li
,
S.
Lodge
,
M.
Ozbil
,
H.
Jiang
,
S.
Penalba
,
V.
Batista
, and
H.
Zhuang
, “
Implausibility of the vibrational theory of olfaction
,”
Proc. Natl. Acad. Sci. U.S.A.
112
(
21
),
E2766
E2774
(
2015
).
5.
L.
Turin
,
S.
Gane
,
D.
Georganakis
,
K.
Maniati
, and
E.
Skoulakis
, “
Plausibility of the vibrational theory of olfaction
,”
Proc. Natl. Acad. Sci. U.S.A.
112
(
25
),
E3154
(
2015
).
6.
E.
Block
,
S.
Jang
,
H.
Matsunami
,
V. S.
Batista
, and
H.
Zhuang
, “
Reply to Turin et al.: vibrational theory of olfaction is implausible
,”
Proc. Natl. Acad. Sci. U.S.A.
112
(
25
),
E3155
E3155
(
2015
).
7.
M.
Paoli
,
A.
Anesi
,
R.
Antolini
,
G.
Guella
,
G.
Vallortigara
, and
A.
Haase
, “
Differential odour coupling of isoptomers in the honeybee brain
,”
Sci. Rep.
6
,
21893
(
2016
).
8.
E.
Drimyli
,
A.
Gaitanidis
,
K.
Maniati
,
L.
Turin
, and
E. M.
Skoulakis
, “
Differential electrophysiological responses to odorant isotopologues in drosophilid antennae
,”
eNeuro
3
(
3
),
e0152.2016
(
2016
).
9.
J.
Brookes
,
A.
Horsfield
, and
A.
Stoneham
, “
The swipe card model of odorant recognition
,”
Sensors
12
,
15 709
15 749
(
2012
).
10.
L.
Turin
, “
A spectroscopic mechanism for primary olfactory reception
,”
Chem. Senses
21
,
773
791
(
1996
).
11.
R.
Hoehn
,
D.
Nichols
,
H.
Neven
, and
S.
Kais
, “
Status of the vibrational theory of olfaction
,”
Front. Phys.
6
,
25
(
2018
).
12.
J.
Brookes
,
F.
Hartoutsiou
,
A.
Horsfield
, and
A.
Stoneham
, “
Could humans recognize odor by phonon assisted tunneling?
,”
Phys. Rev. Lett.
98
,
038101
(
2007
).
13.
I.
Solv’yov
,
P.-Y.
Chang
, and
K.
Schulten
, “
Vibrationally assisted electron transfer mechanism of olfaction: Myth or reality?
,”
Phys. Chem. Chem. Phys.
14
,
13 861
13 871
(
2012
).
14.
E.
Bittner
,
A.
Madalan
,
A.
Czader
, and
G.
Roman
, “
Quantum origins of molecular recognition and olfaction in drosophila
,”
J. Chem. Phys.
137
,
22A551
(
2012
).
15.
A.
Checinska
,
F.
Pollock
,
L.
Heaney
, and
A.
Nazir
, “
Dissipation enhanced vibrational sensing in an olfactory molecular switch
,”
J. Chem. Phys.
142
,
025102
(
2015
).
16.
A.
Tirandaz
,
F. T.
Ghahramani
, and
V.
Salari
, “
Validity examination of the dissipative quantum model of olfaction
,”
Sci. Rep.
7
,
4432
(
2017
).
17.
J.
Brookes
, “
Quantum effects in biology: Golden rule in enzymes, olfaction, photosynthesis and magnetodetection
,”
Proc. R. Soc. A
473
,
20160822
(
2017
).
18.
A.
Tirandaz
,
F.
Ghahramani
, and
A.
Shafiee
, “
Dissipative vibrational model for chiral recognition in olfaction
,”
Phys. Rev. E
92
,
032724
(
2015
).
19.
G.
Lindblad
, “
On the generators of quantum dynamical semigroups
,”
Commun. Math. Phys.
48
,
119
130
(
1967
).
20.
I.
Khemis
,
N.
Mechi
, and
A.
Lamine
, “
Stereochemical study of mouse muscone receptor mor215-1 and vibrational theory based on statistical physics formalism
,”
Prog. Biophys. Mol. Biol.
136
,
54
60
(
2018
).
21.
J.-P.
Vilardaga
,
M.
Bünemann
,
C.
Krasel
,
M.
Castro
, and
M.
Lohse
, “
Measurement of the millisecond activation switch of g protein–coupled receptors in living cells
,”
Nat. Biotechnol.
21
,
807
812
(
2003
).
22.
R.
Hoehn
,
D.
Nichols
,
H.
Neven
, and
S.
Kais
, “
Neuroreceptor activation by vibration-assisted tunneling
,”
Sci. Rep.
5
,
9990
(
2014
).
You do not currently have access to this content.