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Molecular propeller is a
molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and b ...
that can propel fluids when rotated, due to its special shape that is designed in analogy to macroscopic
propellers A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
: it has several molecular-scale
blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Histor ...
s attached at a certain pitch angle around the circumference of a
shaft Shaft may refer to: Rotating machine elements * Shaft (mechanical engineering), a rotating machine element used to transmit power * Line shaft, a power transmission system * Drive shaft, a shaft for transferring torque * Axle, a shaft around whi ...
, aligned along the rotational axis. The molecular propellers designed in the group of Prof. Petr Král from the
University of Illinois at Chicago The University of Illinois Chicago (UIC) is a public research university in Chicago, Illinois. Its campus is in the Near West Side community area, adjacent to the Chicago Loop. The second campus established under the University of Illinois ...
have their blades formed by planar
aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
molecules and the shaft is a
carbon nanotube A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon na ...
.
Molecular dynamics Molecular dynamics (MD) is a computer simulation method for analyzing the physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a fixed period of time, giving a view of the dynamic "evolution" of th ...
simulations show that these propellers can serve as efficient pumps in the bulk and at the surfaces of liquids. Their pumping efficiency depends on the chemistry of the interface between the blades and the liquid. For example, if the blades are
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, ...
, water molecules do not bind to them, and the propellers can pump them well. If the blades are
hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...
, water molecules form
hydrogen bonds In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...
with the atoms in the polar blades. This can largely block the flow of other water molecules around the blades and significantly slow down their pumping.


Driving

Molecular propellers can be rotated by
molecular motors Molecular motors are natural (biological) or artificial molecular machines that are the essential agents of movement in living organisms. In general terms, a motor is a device that consumes energy in one form and converts it into motion or mecha ...
that can be driven by chemical, biological, optical and electrical means, or various ratchet-like mechanisms. Nature realizes most biological activities with a large number of highly sophisticated molecular motors, such as
myosin Myosins () are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility. The first myosin (M ...
,
kinesin A kinesin is a protein belonging to a class of motor proteins found in eukaryotic cells. Kinesins move along microtubule (MT) filaments and are powered by the hydrolysis of adenosine triphosphate (ATP) (thus kinesins are ATPases, a type of enzy ...
, and
ATP synthase ATP synthase is a protein that catalyzes the formation of the energy storage molecule adenosine triphosphate (ATP) using adenosine diphosphate (ADP) and inorganic phosphate (Pi). It is classified under ligases as it changes ADP by the formation ...
. For example, rotary
molecular motors Molecular motors are natural (biological) or artificial molecular machines that are the essential agents of movement in living organisms. In general terms, a motor is a device that consumes energy in one form and converts it into motion or mecha ...
attached to protein-based tails called
flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have fro ...
can propel bacteria.


Applications

In a similar way, the assembly of a molecular propeller and a molecular motor can form a nanoscale machine that can pump fluids or perform
locomotion Locomotion means the act or ability of something to transport or move itself from place to place. Locomotion may refer to: Motion * Motion (physics) * Robot locomotion, of man-made devices By environment * Aquatic locomotion * Flight * Locomo ...
. Future applications of these nanosystems range from novel analytical tools in physics and chemistry,
drug delivery Drug delivery refers to approaches, formulations, manufacturing techniques, storage systems, and technologies involved in transporting a pharmaceutical compound to its target site to achieve a desired therapeutic effect. Principles related to dr ...
and
gene therapy Gene therapy is a Medicine, medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying ...
in biology and medicine, advanced nanofluidic
lab-on-a-chip A lab-on-a-chip (LOC) is a device that integrates one or several laboratory functions on a single integrated circuit (commonly called a "chip") of only millimeters to a few square centimeters to achieve automation and high-throughput screening. ...
techniques, to tiny
robots "\n\n\n\n\nThe robots exclusion standard, also known as the robots exclusion protocol or simply robots.txt, is a standard used by websites to indicate to visiting web crawlers and other web robots which portions of the site they are allowed to visi ...
performing various activities at the nanoscale or microscale.


See also

*
Molecular modelling Molecular modelling encompasses all methods, theoretical and computational, used to model or mimic the behaviour of molecules. The methods are used in the fields of computational chemistry, drug design, computational biology and materials sci ...
*
Molecular motor Molecular motors are natural (biological) or artificial molecular machines that are the essential agents of movement in living organisms. In general terms, a motor is a device that consumes energy in one form and converts it into motion or mec ...
*
Nanocar The nanocar is a molecule designed in 2005 at Rice University by a group headed by Professor James Tour. Despite the name, the original nanocar does not contain a molecular motor, hence, it is not really a car. Rather, it was designed to answer t ...
*
Nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal ...


References

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External links


University of Illinois at Chicago press release
Molecular machines