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The geometry of pi electron cloudsThe Geometry of pi electron clouds Stuart Hameroff http://www.quantumconsciousness.org/ Living
organisms are seen as being characterised by self-organisation,
maintenance of a stable internal environment, metabolism (energy
utilisation), growth, adaption, reproduction and evolution. The
uniqueness of living systems is often attributed to emergent properties
of biochemical and physiological processes. The idea of emergence, much
touted in consciousness studies, assumes an hierarchical organisation
in which a novel property arises from the interaction of simpler
components. Thus candle flames emerge from the interaction of gas and
dust particles. In his 1944 book, ‘What is Life?’ Schrödinger suggested a quantum basis for life. His ideas relate to the subsequently discovered structures of DNA, RNA, cytoskeletal proteins such as microtubules and actin. Schrödinger also proposed that living systems might involve non-local quantum correlations. Mainstream science moved away from the idea of quantum processes in living organisms during the second half of the 20th century, although a few physicists such as Fröhlich kept the idea alive. Fröhlich proposed that biochemical energy could pump quantum coherent dipole states in geometrical arrays of non-polar π electron resonance clouds. Such electron clouds are now known to be isolated from water and ions, and present in cells within membranes, microtubules and organelles. These electron clouds can use London forces, involving interaction between instantly forming dipoles in different electron clouds, to govern the conformation of biomolecules, particularly proteins. The solid parts of cells include membranes and protein structures and these have within them hydrophobic areas containing oil-like structures with π electron resonance clouds. In water, non-polar oily molecules such as benzene, which are hydrophobic are pushed together, attracting each other by London forces, and eventually aggregate into stable regions shielded from interaction with water. London forces can govern the configurations of protein in these regions. Such regions occur as planes in membranes and as pockets in proteins. In some structures, notably the microtubule lattices, π electrons are less than two nanometres apart, at which distance they can become entangled. The mainstream view has discounted quantum processes on the basis that in the conditions within living organisms, they would decohere too rapidly to be useful for biological processes. Hameroff has for a long time argued that the microtubules could be screened from the general environment of the brain. Some recent studies suggest that biomolecules can use the energy of the system to support quantum states (1. Engel et al) (2. Ouyang & Awscalom). The Engel study demonstrated quantum coherence as driving photosynthesis at normal temperatures for plant life. Photons travel through all the possible pathways of the protein scaffold surrounding photosynthetic chlorophyll. Ouyang & Awschalom demonstrated that quantum spin transfer through benzene π electrons clouds is enhanced in efficiency as temperature rises, which is opposite to what conventional thinking would have predicted. Life
is based on carbon chemistry and notably carbon ring molecules, such as
benzene, which has electron resonance clouds in which London forces are
active. Carbon has four atoms in its outer shell, able to form four
covalent bonds with other atoms. In some cases two of the electrons
form a double bond with another atom, and the remaining two outer
electrons remain mobile and are known as π electrons. In benzene, there
are three double bonds between six carbon atoms, such that all six
carbon atoms are involved in a bond. The ring structure, into which
these atoms are formed, famously came to its discoverer, Friedrich von
Kekule, in a dream of a snake biting its tail. There are varying
configurations of the bonds and the π electrons and the molecule
resonates between these stable configurations. Benzene rings and the
more complex indole rings are referred to as aromatic rings and make up
several of the amino acid side groups that are attached to proteins.
The indole rings also resonate between states. Some larger biomolecules
can have a polar hydrophylic end and a non-polar hydrophobic ring end.
Components of the lipid cell membrane take this form. Membranes
comprise double layers of such molecules, with an internal non-polar
and hydrophobic region. However, Hameroff regards the cell membrane as
too fluid and lacking in lattice structure to make it a good candidate
for information processing. Proteins look to be more suitable in this
respect. Proteins constitute the driving machinery of living systems, since it is they which open and close ion channels, grasp molecules to enzymes and receptors, make alterations within cells, and govern the bending and sliding of muscle filaments. The organisation of protein is still poorly understood. Proteins are formed from 20 different amino acids with an enormous number of possible sequences. Van der Waals forces are involved in the proteins folding into different conformations, with a huge number of possible patterns of attraction and repulsion between the side groups of the protein. During the protein folding process there are non-local interactions between aromatic rings, which has been seen as suggestive of quantum mechanical sampling of possible foldings (3. Klein-Seetharaman). Once formed a protein structure can be stabilised by outwardly facing polar groups and by regulation from non-polar regions within. The coalescence of non-polar amino acid side groups such as two aromatic rings can result in extended electron clouds constituting hydrophobic pockets. Protein conformation represents a delicate balance between forces such as chemical and ionic bonds, and as a result London forces driven by π electrons in hydrophobic pockets can tip the balance and thus govern conformations of protein. Anaesthesia appears to be another process involving hydrophobic pockets in protein. A century ago Meyer & Overton showed that the potency of anaesthetic gases correlated with their solubility in lipid-like mediums, and for a long time this was assumed to mean that the lipid cell membrane was the site of action. However, Franks and Lieb (4.) showed that anaesthetic agents act in the hydrophobic pockets in protein, by means of London forces. Microtubules are comprised of the protein tubulin. Tubulin has a dimer form with an alpha and beta monomer joined by a ‘hinge’. The tubulin has a large non-polar region in the beta monomer just below the ‘hinge’. Other smaller non-polar regions with π electron rich indole rings, are distributed throughout the tubulin with distances of about two nanometres between them. The positioning of π electron clouds within about two nanometres of one another is suggested to allow the electrons to become entangled. This entanglement can spread through the microtubule and to other microtubules in the same dendrite and then via gap junctions to other neurons, thus allowing a macroscopic quantum state to extend over a large region of the brain. Hameroff argues for the information processing potential of microtubules. This idea goes back to Sherrington, the prominent mid-20th century neuroscientist. The microtubules are formed of 13 filamentous tubulin chains skewed so that the filaments run down the cylinder of the microtubule in a helical form, and hexagonal in that each tubulin dimer has six neighbours. It is argued that if each tubulin stands for an information bit, then the form of this microtubule lattice is suitable for computation. In simulations, interactions with neighbouring tubulins allow processing of information with memory coded into modification of the tubulins (5. Rasmussen et al). The skewed form of the microtubules means that where winding patterns intersect, they coincide with the attachment of microtubule associated proteins (MAPs), which link microtubules into a scaffolding. In simulations these sites correspond with coherent phonon resonance in the lattice (6. Samsonovich). Hameroff also suggests that the Fibonacci series of the winding pathways on the microtubules match biochemical resonances, and may provide for quantum error correction, which can help to prevent decoherence. |
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