Shortly after Hameroff and Penrose combined their ideas to produce the Orch OR theory, three particle physicists (Ellis, Mavromatos, Nanopoulos) came out with a string-theoretic alternative, in which the microtubule is modelled as a 1+1 dimensional quantum gravitational system.
Thanks to an ideonomy from T.L., I realised that it might be time for another look at their model, as there has been a revolution in 2D quantum gravity since those days, associated with extending holographic duality to "JT gravity".
My main misgiving is that the microtubule is not actually just a 1+1 dimensional line, it's a 2+1 dimensional cylinder. But perhaps there's an uplift to M theory that adds the extra dimension...
