we interrupt this thread to make the following announcement:
people, can we bring this back on topic, otherwise vecktors' ruthless signal to noise scythe will be used.
Personal insults are not acceptable even if someone dares to have a different opinion, the whole point of discussing is that you should be able to argue your position without resorting to personal attacks. Disaggreement and unorthodoxy and maverick ideas are essential to science, homogenous consensus bullshit dogma is for comittees, politicans and global warming science.
KEEP IT CIVIL
That ends the public announcement....
Back on topic
Turins theory Olefaction still requires an element of lock and key in his original paper he never proposed that there was some special receptor that looked for IR stretches and bends, rather he said that they were pretty standard G-protein coupled receptors might be activated through electron tunneling.
fundementally it doesn't matter what IR features or molecular structure the ligand possesses it is totally irrelevant if the molecule cannot get into the tunneling gap. so Turins theory cannot be a replacement for lock and key/ induced fit unless as someone pointed out there were special non shape descriminant receptors, for which there is no real evidence
I personally do not see any reason why electronic effects at the receptor cannot be part and parcel of receptor activation, however they would work in concert with lock and key.
A few quick thoughts,
take the 5ht2a receptor, there are lots of competitive ligands for the normal binding domain, most are pretty much of a muchness but we already know that there are several down stream signalling pathways. yet the ligands are so similar in shape it is difficult to see how such a slight difference in shape could cause such a radical change in receptor conformation in order to trigger a whole different cascade of downstream signalling. the two ligands I am thinking of are Lisuride and LSD.
In the late 1960s there were a series of papers on mescaline analogs which correllated HOMO to psychedelic potency ( schneider I think), and with the 245 series the correlation was pretty good.
the 245 substituted phenethylamines are perfect for electron tunneling, the 4 side chain is perpendicular to the oxygens and the lone pairs of the oxygens can act as the contacts to each side of the gap.
I can think of a couple of ways of testing the electronic hypothesis It would be good to kill it off once and for all as it has been bouncing around for over a decade, but I need to do some proper reading.