When Linda Buck and Richard Axel published their Nobel Prize winning research on the olfactory receptors in 1991, they identified in mice 1,000 G-protein-coupled receptors used for olfaction [REF].
The most recent shape theory, also known as odotope theory or Weak Shape Theory, holds that a combination of activated receptors is responsible for any one smell, as opposed to the older model of one receptor, one shape, one smell.