Energy levels in microtubules

Atomic water channel controlling remarkable properties of a single brain microtubule: Correlating single protein to its supramolecular assembly

Satyajit Sahu & Anirban Bandyopadhyay et al, National Institute for Materials Science, Japan

Biosensors and Bioelectronics 47 141-148, 21 February 2013

Summary and review of the above paper

INTRODUCTION: The authors say the prior to this paper the properties of tubulin and microtubules were not extensively studies using the up-to-date technologies mentioned here. Theories that apply to metals, insulators and semi-conductors are not relevant to microtubules. Bandyopadhyay’s group demonstrate that in microtubules the energy level of up to 40,000 individual tubulin proteins and the energy level of the microtubule are the same. The water core and the individual tubulin proteins are suggested to control the properties of the microtubule by means of delocalised electromagnetic oscillations. The properties of the microtubule might be taken to suggest that the system can support a macroscopic quantum state.

Unique properties

The nanotubes of microtubules are filled by water molecules with unique electrical and optical properties. A microtubule comprises about 30-40,000 tubulin proteins. This study demonstrates that, in contrast to most materials, the energy level of each protein and the energy level of the microtubule are the same. The total microtubule is also more conducting than the individual protein molecules that comprise it. The water core of the microtubule is seen as resonantly integrating the nanotube so that it functions like a single protein. The authors say that prior to them, tubulin and microtubule properties were not extensively studied, implying a lead in applying the most up-to-date technology to this area. They point out that studies based on noise-free conditions are not relevant to microtubules located within cells. Moreover, the composition of the microtubule lattice is much more complicated than that of artificial carbon nanotubes. The water channel in the core of the microtubule binds the helically wrapped tubulins so that the properties of the individual tubulin proteins define the properties of the microtubule.

Structure of the microtubules

Proteins are single chain polymers that fold into various structures related to their biological functions. The microtubule tubulin proteins assemble into an hexagonal close-packing in a 2D sheet, which forms into a hollow cylinder with a water channel inside it. Between 30-40,000 tubulin proteins can assemble into a microtubule without modifying the energy level of the whole polymer. Theories that apply for metals, insulators or semi-conductors do not apply for microtubules. Energy levels are always the same for microtubules irrespective of energy absorption.

Delocalised electromagnetic oscillations

This is seen as making microtubules into potential noise alleviators. The tubulins are viewed as reaching a particular energy level, beyond which further energy absorption from outside the microtubule is not allowed. The vibrational peaks of tubulin survive in the entire microtubule. Vibrations surviving for picoseconds or even nanoseconds are distributed over the entire length of the microtubule. Relaxation times for tubulins and microtubules over picoseconds and nanosecond timescales are identical. In studies where water is removed from the microtubule core, the special properties of the microtubule disappear, suggesting that the water channel is involved in the conductivity and force modulation of the microtubule. The water channel and the tubulin protein are between them seen as controlling the properties of the microtubule. It is thought that it is only possible for the water molecules and the tubulin to be coupled by delocalised electromagnetic oscillations.

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