%0 Journal Article
%T The Potential of Isotopomers as a Test for the Vibrational Theory of Olfactory Sense Recognition
%A Karel D. Klika
%J ISRN Organic Chemistry
%D 2013
%R 10.1155/2013/515810
%X The continuing debate over the basis of odorant recognition with respect to the molecular shape (¡°lock and key¡±) theory versus the vibrational theory could potentially be resolved by the testing of 13C-labeled odorants. The application of 13C isotopomers is discussed herein by means of DFT-calculated IR vibrations and Gibbs¡¯ free energies (¦¤ ) for acetophenone and octan-1-ol, two odorants for which the 2D (deuterium) isotopomers have previously been shown to be discernible from their respective 1H (normal) counterparts by Drosophila melanogaster. 1. Introduction For many animals, their ability to detect volatile molecules-odorants-by way of the olfactory sense can literally mean the difference between survival and demise or the continued propagation of the species. By contrast, for human beings, our sense of smell, which is weak in comparison to some animals, is considered more of an indulgence rather than a functionality necessary for survival on a par with sight and hearing, perhaps thereby explaining in part, from an anthropocentric perspective, why it is the least understood of our senses. Although olfactory receptor (OR) sites have been identified and the molecular basis for the olfactory sensory process elucidated (both in vertebrates and insects for which the processes differ [1])¡ªindeed, the work warranted the awarding of a Nobel Prize to Buck and Axel [2¨C4] for this outstanding accomplishment¡ªthe means by which odorants are recognized at the molecular level and actuation occurs is still debated. Thus, intriguingly, despite numerous attempts and decades of endeavor, there is still no definitive consensus on the identity of the molecular property that the OR is responding to, and the manner of odorant recognition remains, surprisingly, a contentious issue [5¨C15]. Overall, there are, or have been over the years, a number of competing theories, either distinct or modified, and these theories or variations thereof number in the dozens [6, 15, 16]. It is, however, generally accepted [1, 6, 15, 17] presently by mainstream researchers that the molecular basis for odorant recognition by an OR is essentially based on the molecular size and shape (the ¡°fit¡±) of the odorant originating from the work of Moncrieff [16, 18] and then further solidified by Amoore [16, 19, 20]. The concept is generally referred to as the shape or ¡°lock and key¡± theory (in addition to various permutations). An alternate theory that is nonetheless prominent, and somewhat controversial (e.g., [12]), is the vibrational theory whereby odorant recognition is considered to be based on
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2013/515810/