Aromatic molecules & hydrophobic channels
Consciousness in the Universe: Neuroscience, Quantum Space-Time and Orch OR Theory
Roger Penrose and Stuart Hameroff (2011)
This paper sets out to update Penrose and Hameroff’s consciousness theory in the light of developments in quantum biology. What is lacking, however, is any proper discussion of the similarities between photosynthetic organisms that have functional quantum coherence based on aromatic molecules, and the aromatic molecules found in microtubular protein. This may be because the timescales involved in photosynthetic coherence are much shorter than those proposed by Hameroff. In this respect, it would seem more promising to work up from the photosynthetic mechanism that is known to exist, and to then possibly adjust the original Hameroff proposition accordingly. Despite this shortcoming, the matters introduced in this paper with respect to aromatic rings and possible hydrophobic channels look to be of potentially vital importance for a theory of quantum consciousness.
The paper starts with an attempt at a definition of consciousness, here summarised as the subjective experience of internal and external phenomenal worlds, and as being central to choices associated with the experience of freewill. Further to this, the authors take the view that in physics there are precursors of consciousness that became conscious through the processes of biology. They are particularly interested in the cognitive abilities of single-cell organisms that can find food, learn and reproduce all without a nervous system. This looks to be particularly relevant to the possibility, not however advanced by these authors, that consciousness can arise in single neurons, albeit single neurons bound together by the gamma synchrony.
Hameroff has for a long time argued that the form of quantum consciousness proposed by Penrose could be instantiated in microtubules within neurons. Synaptic inputs at neuronal membranes are suggested to reach microtubules via microtubule associated protein 2 (MAP2) and calcium calmodulin kinase II (CaMKII). Microtubules are suggested to have originated about 1.3 bn years ago, as a result of symbiosis between prokaryote cells, mitochondria and spirochetes. This merger allowed cells to become mobile.
Unexpected discoveries in biology
The most important change since Penrose and Hameroff first propounded their ideas in the 1980s and 1990s is the unexpected discoveries in biology relative to higher temperature quantum activity. In 2003 Ouyang & Awschalom (1.) showed that quantum spin transfer in phenyl rings (an aromatic ring molecule like those found in protein hydrophobic pockets) increases at higher temperatures. In 2005 Bernroider and Roy (2.) researched the possibility of quantum coherence in K+ neuronal ion channels. A more crucial discovery came in 2007 when it was demonstrated that quantum coherence was functional in efficiently transferring energy within photosynthetic organisms (Engel et al, 2007, 3). Subsequent papers showed functional quantum coherence in multicellular plants and also at room temperature. In 2011 papers by Gauger et al (4.) and Luo and Lu (5) dealt with higher temperature coherence in bird brain navigation and in protein folding. Work by Anirban Bandyopadhyay (6.) is seen as making the Penrose/Hameroff hypothesis more feasible. This research with single animal microtubules showed eight resonance peaks correlated with helical pathways round the cylindrical microtubule lattice. This allowed ‘lossless’ electrical conductance.
The authors make a direct reply to one critic in particular (McKemmish et al, 2010, 7.) McKemmish claimed that switching between two states of the tubulin protein in the microtubules would involve conformational changes requiring GTP hydrolysis which in turn would involve an impossible energy requirement. The authors however claim that electron cloud dipoles (van der Waals London forces) are sufficient to achieve switching without large conformational changes.
Tubulin, and aromatic rings: Building blocks of consciousness?
Each tubulin protein contains the amino acids tryptophan and phenylalanine with aromatic rings. Each hydrophobic pocket in the tubulin is suggested to be composed of four such aromatic rings, with the hydrophobic pockets being arranged in channels. Van der Waals London forces operate in the hydrophobic pockets in tubulin, based on the π electron rings of tryptophan and phenylaline. This concept derives originally from Fröhlich, who suggested that proteins are synchronised by the oscillations of dipoles in the electron clouds of these amino acids. Anaesthetic gases are similarly suggested to work through their action on aromatic amino acids in hydrophobic pockets in neuronal proteins, including membrane proteins.
Hydrophobic channels and long-range van der Waals
A paper published in 1998 (Nogales et al, 8.) described the structure of the tubulin protein and identified the existence and location of the non-polar aromatic amino acids tryptophan and phenylamine in tubulin. These are located in hydrophobic pockets, but these pockets are within 2 nanometres of one another, collectively they can be interpreted as hydrophobic channels or pathways rather than mere pockets. This is suggested to allow linear arrays of electron clouds capable of supporting long-range van der Waals London forces. The quantum channels in individual tubulins are seen as being aligned with those in neighbouring tubulins within the microtubule lattice, and these provide helical winding patterns.