Molecular machine

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A molecular machine or nanomachine is a structure made up of macromolecules that can perform certain functions. It is a class of supramolecular compounds that can perform mechanical movements. As in bionics , systems are copied from animal or plant cells and an attempt is made to construct them synthetically. On the other hand, one tries to apply the basic principles of classical mechanics to machines in the molecular domain. Molecular machines belong to the research area nanotechnology , where a number of complex molecular machines have been proposed. Since it has been proven that a perpetual motion machine is impossible according to the fundamental laws of physics, a molecular machine, just like a classical machine , has to be supplied with energy from outside .

Molecular systems that are able to shift a chemical or mechanical process into equilibrium represent a potentially important branch of chemistry and nanotechnology . For this process, a gradient previously generated externally (e.g. concentration gradient, temperature difference, Potential difference or similar) is necessary for the machine to be able to perform useful work. Since a system always strives for equilibrium, substances in cells will always migrate in the direction of a concentration gradient, or molecules of different temperatures will mix in such a way that temperature equilibrium occurs.

The 2016 Nobel Prize in Chemistry was awarded to Jean-Pierre Sauvage , Sir J. Fraser Stoddart and Bernard L. Feringa for the design and synthesis of molecular machines.

Historical background

There are two thought experiments on the historical background of molecular machines: Maxwell's demon and Feynman's "ratchet" (or molecular ratchet ): Maxwell's demon is described elsewhere, and a different interpretation of Feynman's law can be found below:

Imagine a very small system (see picture below) of two paddle wheels or gear wheels, connected by a rigid axle, and that it is possible to keep these two wheels at two different temperatures. The gear at temperature 2 (T2) is prevented from rotating counterclockwise by a pawl, which ensures that the system moves in the same direction. Therefore, the axis can only turn clockwise and the machine could lift a weight (m) upwards. If the paddle wheel in box with temperature 1 (T1) were in a much hotter environment than the gear in box T2, one would expect the kinetic energy with which the gas molecules (red circles) hit the blades to be much higher at T1 would be than the energy of the gas molecules that will hit against the teeth of the gear at T2. Therefore, at temperature T2, i.e. with lower kinetic energy of the gaseous particles, there would be a much lower probability that the molecules would collide with the gearwheel in the statistically opposite direction. Furthermore, the pawl would make it possible, with a directed movement, to rotate the axis slowly over a certain period of time and to lift the weight (m).

Scheme of Feynman's ratchet

As described, the system can seem like a perpetual motion machine; however, the main component of the system is the thermal gradient within the system. The second law of thermodynamics also applies here, because the temperature gradient has to be generated by some external conditions. The Brownian molecular motion of the gaseous particles supplies the machine with energy, and the temperature gradient causes the device to unbalance the system with a circular motion. In Feynman's ratchet, the accidental Brownian movement is not counteracted, but it is made usable and guided. It depends on whether the temperature gradient can also be maintained on a molecular scale, or whether a redistribution of energy takes place through molecular vibrations within the molecule. In addition, it should be noted that Feynman's machine does valuable work in lifting a mass to provide energy to a molecular machine using Brownian motion. This energy (potential energy of the lifted weight (m)) can possibly be used to carry out nanoscale tasks.

Function of molecular machines

From a synthetic point of view, there are two main types of molecular machines: molecular switches (or pendulums) and molecular motors. The main difference between the two systems is that a switch acts on a system as a function of state, whereas a motor acts on a system as a function of movement. A switch (or a pendulum) is operated by translational motion, but the return of the switch to its original position has a mechanical effect and releases energy that is fed into the system. In addition, switches cannot be used to repeatedly disrupt a chemical system while energizing, which a motor can in turn.

Synthesis and types of molecular machines

A variety of simple molecular machines have been synthesized by chemists. They cannot consist of a single molecule, but are designed for mechanical molecular architectures such as rotaxanes and catenanes . Carbon nanomotors have also been made.

  • A synthetic molecular motor is a molecule that is able to execute a directional rotational movement, driven by external energy. A number of molecular machines have been synthesized, powered by light or a reaction with other molecules. One example is a molecular drill that - powered by UV light - perforates cell walls to such an extent that small molecules - especially water (H 2 O) - can escape. The UV light can be used selectively to treat the desired tissue.
  • Molecular propeller is a molecule that can drive liquids when it rotates, due to its special shape, which is analogous to the macroscopic propeller. It has several wings that are attached on a molecular scale at a certain angle of inclination around the stem of a nanoscale wave.
  • Molecular switch is a molecule that can be reversibly switched between two or more stable states. The molecules react to changes in pH, light, temperature, electrical current, microenvironment or the presence of a ligand and are thereby shifted between different states.
  • A molecular pendulum (shuttle) is a molecule that moves molecules or ions from one place to another. A molecular pendulum consists of a rotaxane, a macrocycle that can move between two locations or stations along a dumbbell bar.
  • Molecular tweezers are host molecules that are able to enclose objects. The open cavity of the molecule binds (like a pair of tweezers) elements with non-covalent bonding, (including hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, π-π interactions and / or electrostatic effects). Examples of molecular tweezers made up of DNA and referred to as DNA machines have been described.
  • Molecular sensor is a molecule that is used to detect the change in concentration of a substance to be analyzed. Molecular sensors, like detectors, combine molecular recognition with signal recording or transmission so that the presence of a particular substance can be observed.
  • A molecular logic gate is a molecule that performs a logical operation on one or more logical inputs and produces a single logical output. In contrast to a molecular sensor, the molecular logic gate only gives an output when there is a certain combination of inputs.

Role models from biology

Examples of biological molecular machines

The most complex molecular machines are the proteins found in cells . These include motor proteins such as myosin , which is responsible for muscle contraction, kinesin , which transports the organelles in the cells away from the nucleus with microtubules, dynein , which causes the flagella to move, and membrane-based ATPases such as ATP synthase . These proteins and their nanoscale dynamics are more complex than any molecular machine ever constructed. Probably the most important biological machines are the ribosomes . In fact, microtubules are nanomachines made up of over 600 proteins in molecular complexes. The first meaningful applications of these biological machines may be in nanomedicine . For example, they could be used to detect and destroy cancer cells. Molecular nanotechnology is a subchapter of nanotechnology. If one considers the entire possibilities of molecular mechanics , biological machines could affect a therapy on a molecular or atomic level. Nanomedicine could use these nanorobots to detect and repair damage or infection. Molecular nanotechnology is highly theoretical in order to anticipate that inventions in the field of nanotechnology are promising and a future-oriented research area. The current state of research in nanotechnology with the proposed elements is still a long way from that of nanorobots.

use

The synthesis of complex molecular machines is a promising area of ​​theoretical research. A variety of molecules, such as a molecular propeller , have been designed, the difficulty being in implementing these synthetic plans. They form the basis of a large area of ​​nanotechnology.

See also

literature

  • Ballardini R, Balzani V, Credi A, Gandolfi MT, Venturi M .: Artificial Molecular-Level Machines: Which Energy To Make Them Work? . In: Acc. Chem. Res . 34, No. 6, 2001, pp. 445-455. doi : 10.1021 / ar000170g .
  • Peter Satir, Søren T. Christensen: Structure and function of mammalian cilia . In: Springer Berlin / Heidelberg (ed.): Histochemistry and Cell Biology . 129, No. 6, March 26, 2008, p. 688. doi : 10.1007 / s00418-008-0416-9 . PMID 18365235 . PMC 2386530 (free full text).
  • V. Balzani, M. Venturi, A. Credi: Molecular Devices and Machines, A Journey into the Nanoworld , Wiley, VCH 2003, ISBN 3-527-30506-8
  • David A. Leigh: Genesis of the Nanomachines: The 2016 Nobel Prize in Chemistry , Angew Chem Int Ed, 55, 14506-14508 (2016).
  • B. Lewandowski, G. De Bo, JW Ward, M. Papmeyer, S. Kuschel, MJ Aldegunde, PME Gramlich, D. Heckmann, SM Goldup, DM D'Souza, AE Fernandes and DA Leigh: Sequence-Specific Peptide Synthesis by on Artificial Small-Molecule Machine , Science, 339, 189-193 (2013).

Individual evidence

  1. ↑ AM Fennimore, TD Yuzvinsky, Wei-Qiang Han, MS Fuhrer, J. Cumings and A. Zettl: Rotational actuators based on carbon nanotubes . In: Nature . 424, No. 6947, 2003, pp. 408-410. bibcode : 2003Natur.424..408F . doi : 10.1038 / nature01823 . PMID 12879064 .
  2. ↑ Lars Fischer: The smallest drill in the world , on Spektrum online from August 31, 2017
  3. ↑ Victor García-López, Fang Chen, Lizanne G. Nilewski, Guillaume Duret, Amir Aliyan, Anatoly B. Kolomeisky, Jacob T. Robinson, Gufeng Wang, Robert Pal, James M. Tour: Molecular machines open cell membranes , in: Nature 548, pp. 567-572, from August 31, 2017, doi: 10.1038 / nature23657
  4. ↑ Cavalcanti A, Shirinzadeh B, Freitas Jr RA, Hogg T .: Nanorobot architecture for medical target identification . In: Nanotechnology . 19, No. 1, 2008, p. 015103 (15pp). bibcode : 2008Nanot..19a5103C . doi : 10.1088 / 0957-4484 / 19/01/015103 .
  5. ↑ Bu Z, Callaway DJ: Proteins MOVE! Protein dynamics and long-range allostery in cell signaling . In: Adv in Protein Chemistry and Structural Biology . 83, 2011, pp. 163-221. doi : 10.1016 / B978-0-12-381262-9.00005-7 . PMID 21570668 .
  6. ↑ M. Amrute-Nayak, RP Diensthuber, W. Steffen, D. Kathmann, FK Hartmann, R. Fedorov, C. Urbanke, DJ Manstein, B. Brenner, G. Tsiavaliaris: Targeted Optimization of a Protein Nanomachine for Operation in Biohybrid Devices . In: Angewandte Chemie . 122, No. 2, 2010, p. 322. doi : 10.1002 / anie.200905200 .
  7. ↑ GM Patel, GC Patel, RB Patel, JK Patel, M. Patel: Nanorobot: A versatile tool in nanomedicine . In: Journal of Drug Targeting . 14, No. 2, 2006, p. 63. doi : 10.1080 / 10611860600612862 .
  8. ↑ S. Balasubramanian, D. Kagan, CM Jack Hu, S. Campuzano, MJ Lobo-Castañon, N. Lim, DY Kang, M. Zimmerman, L. Zhang, J. Wang: Micromachine-Enabled Capture and Isolation of Cancer Cells in Complex Media . In: Angewandte Chemie International Edition . 50, No. 18, 2011, p. 4161. doi : 10.1002 / anie.201100115 .
  9. ^ Robert A., Freitas Jr., Ilkka Havukkala: Current Status of Nanomedicine and Medical Nanorobotics . In: Journal of Computational and Theoretical Nanoscience . 2, No. 4, 2005, pp. 1-25. doi : 10.1166 / jctn.2005.001 .
  10. ^ Robert A. Freitas Jr., Ralph C. Merkle: Nanofactory Collaboration