Microtubules as mechanical force sensors

Nick E. Mavromatos, D.V. Nanopoulos

Erik W. Streed, Valdis Blūms, Marcin Piotrowski +5 more

Xavier Alauze, Alexis Bonnin, Franck Pereira dos Santos

Ravid Shaniv, Roee Ozeri

Abstract Force sensors are at the heart of different technologies such as atomic force microscopy or inertial sensing. These sensors often rely on the measurement of the displacement amplitude of mechanical oscillators under applied force. The best sensitivity is typically achieved when the force is alternating at the mechanical resonance frequency of the oscillator, thus increasing its response by the mechanical quality factor. The measurement of low-frequency forces, that are below resonance, is a more difficult task as the resulting oscillation amplitudes are significantly lower. Here we use a single-trapped 88Sr+ ion as a force sensor. The ion is electrically driven at a frequency much lower than the trap resonance frequency. We measure small amplitude of motion by measuring the periodic Doppler shift of an atomic optical clock transition, enhanced using the quantum lock-in technique. We report frequency force detection sensitivity as low as 2.8 × 10−20 NHz−1/2.

N.Ž. Mišić

The existence of living organisms in the mesoscopic realm may be quite nontrivial and actuallymay emerge from the interplay between quantum mechanics and gravity. On one side, quantumbiology investigates how quantum mechanical phenomena, such as superposition, entanglement,and tunnelling, contribute to biological processes. These quantum effects, once thought to beirrelevant in the “warm, wet, and noisy” environment of living organisms due to decoherence, havebeen found to play significant roles in various biological systems, from photosynthesis to enzymecatalysis. On the other side, gravitational forces have been implicated in the organization ofmicrotubules, which are essential for maintaining cellular structure and function. Recent studieshave demonstrated that gravitational forces can induce three-dimensional chromosomal conformational changes, which are associated with rapid transcriptional responses in human T cells. Sometheories propose that gravity might play a role in decoherence, such as in the Penrose-Hameroffmodel, which proposes that quantum coherence in microtubules could be the basis for consciousawareness and quantum computing-like information processing, with gravity playing a role in thecollapse of the quantum wave function. The model predictions that microtubules can support longrange coherent phenomena have been confirmed by experimental observations of superradiancefrom mega-networks of tryptophan UV-excited transition dipoles, particularly in microtubulearchitectures. Another experimental research highlights that microtubule network exhibits ahierarchy of three-fold resonant frequency patterns across biological scales – from tubulin proteinsto microtubules and neurons. This suggests a quantum-to-classical transition governed by scalefree dynamics, potentially underlying information processing in the brain. A very intriguing fact isthat at the most fundamental level of the origin of life, the standard genetic code, we can observethe scale-free computing that arises from arithmetic regularities of the nucleon numbers related tothe code’s numerous symmetries. Given that some of these symmetries probably originate fromdifferent evolutionary epochs, such scale-free computing may be a latent background mechanismof the organization of the genetic code and therefore relevant to natural computing.

Martynas Skrabulis, Martin Colombano Sosa, Nicola Carlon Zambon +4 more

The sensitivity of a mechanical transducer is ultimately limited by its inherent quantum fluctuations. Here, we use an optically levitated nanoparticle to measure impulsive forces smaller than the particle's zero-point momentum uncertainty. Our approach relies on reversibly squeezing the levitated particle's center-of-mass motion to coherently amplify the perturbation. We demonstrate resolving single impulsive-force kicks as small as 6.9 keV/c, a value 0.6 dB below the sensor's zero-point value.