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

Highlights

• Brain neuron is made of octave musical string, microtubule.

• Brain neurons eliminate noise automatically via microtubule.

• Protein based supramolecule exhibits size-independent electronic and optical properties.

Abstract

Microtubule nanotubes are found in every living eukaryotic cells; these are formed by reversible polymerization of the tubulin protein, and their hollow fibers are filled with uniquely arranged water molecules. Here we measure single tubulin molecule and single brain-neuron extracted microtubule nanowire with and without water channel inside to unravel their unique electronic and optical properties for the first time. We demonstrate that the energy levels of a single tubulin protein and single microtubule made of 40,000 tubulin dimers are identical unlike conventional materials. Moreover, the transmitted ac power and the transient fluorescence decay (single photon count) are independent of the microtubule length. Even more remarkable is the fact that the microtubule nanowire is more conducting than a single protein molecule that constitutes the nanowire. Microtubule's vibrational peaks condense to a single mode that controls the emergence of size independent electronic/optical properties, and automated noise alleviation, which disappear when the atomic water core is released from the inner cylinder. We have carried out several tricky state-of-the-art experiments and identified the electromagnetic resonance peaks of single microtubule reliably. The resonant vibrations established that the condensation of energy levels and periodic oscillation of unique energy fringes on the microtubule surface, emerge as the atomic water core resonantly integrates all proteins around it such that the nanotube irrespective of its size functions like a single protein molecule. Thus, a monomolecular water channel residing inside the protein-cylinder displays an unprecedented control in governing the tantalizing electronic and optical properties of microtubule.

Introduction

In spite of incredible claims, the carbon nanotube could not revolutionize the industry due to complicacy in isolating metallic and semiconducting nanotube, and the DNA adventure (Dekker and Ratner, 2001, Fink and Schönenberger, 1999, Rakitin et al., 2001, Storm et al., 2001, Zhang et al., 2002) turned critical due to its extreme conformational-fluctuations on the atomic scale. The 25 nm wide and from 200 nm to 25 μm long microtubule nanotube stores cellular dynamics codes as doped drugs inside its main constituent tubulin protein similar to ATGC that stores DNA's genetic code. Nature has a catalog of microtubule's cellular code, in all eukaryotes, plants, animals, fungi and Protista kingdom for 3.5 billion years. It forms a complex network inside neurons and living cells controlling fundamental life functions via massively parallel and hierarchical information processing (Barabási and Albert, 1999, Butts, 2009, Gerhart et al., 1997, Moriya et al., 2001, Song et al., 2005, Strogatz, 2001). Since single tubulin and microtubule properties were never studied extensively, here we cater state-of-the-art technologies to unravel the electronics and information processing in these systems (Mange and Tomassini, 1998, Sipper, 2002, Teuscher et al., 2003, Zhang and Gao, 2012). As microtubules are dipped into an extremely noisy cellular soup (Braun et al., 2003, Roberts et al., 2011, Shibata and Ueda, 2008, Szendro et al., 2001a, Szendro et al., 2001b), the properties studied therein contain artifacts, while noise-free bio-material studies are irrelevant to real bio-systems (Roberts et al., 2011). Yet, microtubule is a rigid elastic string unlike DNA and its composition of lattice mixtures is many folds more resourceful than carbon nanotube with no isolation issues—a prime candidate for the state-of-the-art investigations to unravel its embedded nanotechnologies.

The naturally produced drug molecules were automatically doped inside the tubulin protein to add unique properties to the microtubule while keeping the original properties intact. During design and construction of microtubule for a particular species following this route (Nielsen et al., 2010, Nielsen et al., 2006, Redeker et al., 2004), the microtubule structure remained unchanged. The origin of this flexibility is unknown. Moreover, the fusion of DNA-like coding via drug-molecules and carbon nanotube like modulation of property by changing lattice parameters requires identification of its true nano-material class. Consequent theoretical predictions of its remarkable properties (Sahu et al., 2011) were not verified experimentally. In this first comprehensive documentation, we underpin both the fundamental and the applied potentials of this nanotube. We compare single tubulin and microtubule's properties when water channel resides in its core and then after releasing the water in a controlled manner. The water channel couples helically wrapped tubulins such that even though microtubule is a complex composition of several distinct structural symmetries only the single tubulin property defines the microtubule property.

Protein is a single chain polymer, but folds into various patterns, called secondary structures; switching of these structures into an astronomically large number of combinations is restricted via allowed and blocked symmetries. Tubulin protein has two parts, α and β, both appear similar, connected face-to-face, see Fig. 1a. They assemble in a hexagonal close packing into a 2D sheet which folds into a hollow cylinder wrapped around a water channel (see Fig. 1a).