Molecular machine

A molecular machine, nanite, or nanomachine, is a molecular component that produces quasi-mechanical movements (output) in response to specific stimuli (input). In biology, macromolecular machines frequently perform tasks essential for life such as DNA replication and ATP synthesis. The expression is often more generally applied to molecules that simply mimic functions that occur at the macroscopic level. The term is also common in nanotechnology where a number of highly complex molecular machines have been proposed that are aimed at the goal of constructing a molecular assembler. A molecular machine, nanite, or nanomachine, is a molecular component that produces quasi-mechanical movements (output) in response to specific stimuli (input). In biology, macromolecular machines frequently perform tasks essential for life such as DNA replication and ATP synthesis. The expression is often more generally applied to molecules that simply mimic functions that occur at the macroscopic level. The term is also common in nanotechnology where a number of highly complex molecular machines have been proposed that are aimed at the goal of constructing a molecular assembler. For the last several decades, chemists and physicists alike have attempted, with varying degrees of success, to miniaturize machines found in the macroscopic world. Molecular machines research is currently at the forefront with the 2016 Nobel Prize in Chemistry being awarded to Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa for the design and synthesis of molecular machines. Molecular machines can be divided into two broad categories; artificial and biological. In general, artificial molecular machines (AMMs) refer to molecules that are artificially designed and synthesized whereas biological molecular machines can commonly be found in nature. A wide variety of artificial molecular machines (AMMs) have been synthesized by chemists which arerather simple and small compared to biological molecular machines.The first AMM, a molecular shuttle, was synthesized by Sir J. Fraser Stoddart. A molecular shuttle is a rotaxane molecule where a ring is mechanically interlocked onto an axle with two bulky stoppers. The ring can move between two binding sites with various stimuli such as light, pH, solvents, and ions. As the authors of this 1991 JACS paper noted: “Insofar as it becomes possible to control the movement of one molecular component with respect to the other in a rotaxane, the technology for building molecular machines will emerge.”, mechanically interlocked molecular architectures spearheaded AMM design and synthesis as they provide directed molecular motion. Today a wide variety of AMMs exists as listed below. Molecular motors are molecules that are capable of rotary motion around a single or double bond.Single bond rotary motors are generally fueled by chemical reactions whereas double bond rotary motors are generally fueled by light. The rotation speed of the motor can also be tuned by careful molecular design. Carbon nanotube nanomotors have also been produced. A molecular propeller is a molecule that can propel fluids when rotated, due to its special shape that is designed in analogy to macroscopic propellers. It has several molecular-scale blades attached at a certain pitch angle around the circumference of a nanoscale shaft. Also see molecular gyroscope. A molecular switch is a molecule that can be reversibly shifted between two or more stable states. The molecules may be shifted between the states in response to changes in pH, light, temperature, an electric current, microenvironment, or the presence of a ligand. A molecular shuttle is a molecule capable of shuttling molecules or ions from one location to another. A common molecular shuttle consists of a rotaxane where the macrocycle can move between two sites or stations along the dumbbell backbone. Nanocars are single molecule vehicles that resemble macroscopic automobiles and are important for understanding how to control molecular diffusion on surfaces. The first nanocars were synthesized by James M. Tour in 2005. They had an H shaped chassis and 4 molecular wheels (fullerenes) attached to the four corners. In 2011, Ben Feringa and co-workers synthesized the first motorized nanocar which had molecular motors attached to the chassis as rotating wheels. The authors were able to demonstrate directional motion of the nanocar on a copper surface by providing energy from a scanning tunneling microscope tip. Later in 2017, worlds first ever Nanocar race took place in France.