The Feasibility of Coherent Energy Transfer in Microtubules
  It was once purported that biological systems were far too warm and wet to support quantum phenomena mainly due to thermal effects disrupting quantum coherence. However recent experimental results and theoretical analyses have shown that thermal energy may assist, rather than disrupt, quantum coherence, especially in the dry hydrophobic interiors of biomolecules. Specifically, evidence has been accumulating for the necessary involvement of quantum coherence and entanglement between uniquely arranged chromophores in light harvesting photosynthetic complexes. Amazingly, the tubulin subunit proteins, which comprise microtubules, also possess a distinct architecture of chromophores, namely aromatic amino acids including tryptophan. The geometry and dipolar properties of these aromatics are similar to those found in photosynthetic units indicating that tubulin may support coherent energy transfer. Tubulin aggregated into microtubule geometric lattices may support such energy transfer, which could be of import for biological signaling and communication essential to living processes. Here we perform a computational investigation of energy transfer between chromophoric amino acids in tubulin via dipole excitations coupled to the surrounding thermal environment. We present the spatial structure and energetic properties of the tryptophan residues in the microtubule constituent protein tubulin. Plausibility arguments for the conditions favoring a quantum mechanism of signal propagation along a microtubule are provided. Overall we find that coherent energy transfer in tubulin and microtubules is biologically feasible. 
Travis John Adrian Craddock, Douglas Friesen, Jonathan Mane, Stuart   Hameroff, and Jack A. Tuszynski
physics.bio-ph physics.chem-ph