
A depiction of DTA (C14H10S2), a 3-element synthetic molecule that walks like a human, with a triple benzene ring body, and two sulfur-hydrogen legs, i.e. thiol (Ѻ) leg.

A depiction of DTA (C14H10S2), a 3-element synthetic molecule that walks like a human, with a triple benzene ring body, and two sulfur-hydrogen legs, i.e. thiol (Ѻ) leg.

In molecules, DTA (TR:5), or “9,10-DiThioAnthracene”, molecular formula C14H10S2, is synthetic 3-element animate (see: animate molecule) bipedal (see: walking molecule) molecule, with the ability to move along a copper surface, specifically Cu(111), when cooled down to -223°C, and either powered with a little heat or induced to move by the lure of the tip of charged scanning tunneling microscope.

Overview
In 2004, Ludwig Bartels, and his University of California, Riverside research group, used a scanning tunneling microscope (STM) to investigate the diffusion of small molecules upon a CU(111) surface, during which 9,10-Dithioanthracene (DTA) was found to migrate linearly in fashion reminiscent of a bipedal ‘passing leg’ gait. [1]

The following shows a one-dimensional non-directional diffusion migration mechanism of DTA upon a high symmetry Cu(111) surface at 50K, images based on DFT calculations: [1]
DTA (walking)

Rotation around a sulfur atom which occupies a low energy site, bridging two copper atoms, brings both feet into favorable positions. However, the aromatic core is forced out of alignment with the high symmetry direction. This orientation is only observed in experiments conducted at 10K, where thermal movement of DTA is not observed. [1]

AQ molecule | Molecular carrier
In 2007, Bartels, expanding on his DTA experiments, began investigating so-called "molecular carriers", specifically by doing STM studies on AnthraQuinone (AQ) (Ѻ), a DTA-like molecule, formula C14H8O2, with two oxygen feet. The following shows an "AQ molecule" attaching to or carrying a CO2 molecule (or two CO2 molecules) during diffusion along the Cu(111) high-symmetry direction by means of individual steps: [1]

AQ molecule (carrying load)

Bartels found that carrying more load, e.g. 2 or three CO2 molecule, slows the carrier down, just as a human is slowed down when carrying more bundles.


A screen shot from Libb Thims' 2016 video “Walking Molecules: Philosophical Implications”, wherein he explains that to call DTA, a CHS-bipedal, as "not-alive", and to call a HUMAN, a CHNOPS+20-bipedal, "alive" is but a fallacious anthropism-rooted mythological dualism divide, buttressed by layers of ignorance.

A screen shot from Libb Thims' 2016 video “Walking Molecules: Philosophical Implications”, wherein he explains that to call DTA, a CHS-bipedal, as "not-alive", and to call a HUMAN, a CHNOPS+20-bipedal, "alive" is but a fallacious anthropism-rooted mythological dualism divide, buttressed by layers of ignorance.

Philosophical implications
In 2010, Libb Thims was using DTA in “defunct theory of life” debates with Georgi Gladyshev, among others; an example statement shown below:

“We are NOT in agreement. The terms “life”, “biological”, “biosphere”, are all meaningless. Science is very specific. According to your definition (life = structure with metabolism), then, one would conclude that a [synthetic] ‘walking molecule’ is alive. Is the walking molecule DTA (9,10-dithioanthracene) alive? Yes or No? What about the two-legged motile protein ‘kinesin’ (Ѻ) that walks along microtubules carrying loads to destinations, being powered by ATP. (Ѻ) Kinesin is a small 6-element molecule, with molecular formula of about C400H620N100O120P50S20, that walks, carries things, and has a metabolism. Kinesin is like a little human. Do you think that kinesin is alive? Certainly not. It is simply an animate molecule, just like you or I. The problem with the calling some "thing" alive is that it implies perpetual motion of both the first and second kind.”
— Libb Thims (2010). “Origin of Life Debate with Georgi Gladyshev” (post #9), Dec 6

The "life = structure with metabolism" model, to note, was debased by Michael Brooks (2008), who gave the counter argument (see: life criteria counterargument) that many other things not considered "alive", e.g. an automobile, rocket, the sun, etc., consume fuel and excrete waste. [5]

In 2016, Thims, in his “Walking Molecules: Philosophical Implications” video, discussed the philosophical implications of non-alive DTA, a synthetic CHS walking molecule, as opposed to a so-deemed "alive" human, a CHNOPS+20 walking molecule, in respect to Cartesian dualism (1637) as opposed to Goethean monism (1809). [2]

Quotes
The following are related quotes:

“Effectively, DTA kind of rotates around each of the feet and wobbles forward or wobbles backward.”
— Ludwig Bartels (2005), interview with MIT Technology Reviews [3]

“It is often a neglected fact that humans are molecules that walk, run, and sometimes fly, on or above a 'surface', which from a chemical-definitions sense can be defined as either substrate or catalyst, depending on the context of discussion, which varies depending on subject mode: surface chemistry, surface physics, or surface thermodynamics. In this perspective, an intuitive way to better come to understand human behavior (movement and reactions) is to use the conception or reality that humans are 'walking molecules' on a surface and, using this perspective, study the behaviors and operation of smaller nano-size 'walking molecules'. The first operational walking molecules were developed in 2004 by German-born American physical chemist Ludwig Bartels, at the University of California Riverside, who designed a molecule, called 9,10-dithioanthracene (DTA), that can walk in a straight line on a flat surface, like a little person.”
— Libb Thims (2010), opening paragraph from “Walking Molecule” section of the human molecule article; quoted (Ѻ) by QuantumMystics (2015) at BellGab forums, Nov 11

See also
● ATP
● DNA
● Kinesin
● Myosin
● Retinal | Retinal molecule | ABC model
● RNA
● Virus | Virus molecule

References
1. Leigh, David A., Lewandowska, Urszula, Lewandowski, Bartosz, and Wilson Miriam R. (2014). “Synthetic Molecular Walkers”, in: Molecular Machines and Motors: Recent Advances and Perspectives (editors: Alberto Credi, Serena Silvi, Margherita Venturi) (§4:111-38; pgs. 126-27). Springer.
2. Thims, Libb. (2016). “Walking Molecules: Theoretical Implications” (Ѻ), Human Chemistry 101, May 24.
3. Jonietz, Erika. (2005). “Wee Walker” (Ѻ), MIT Technology Reviews, Dec 14.
4. Staff. (2007). “Walking Molecule Now Carries Packages”, PhysOrg, Jan. 18.
5. Brooks, Michael. (2008). 13 Things That Don’t Make Sense: the Most Baffling Mysteries of Our Time (ch. 5: Life, pgs. 69-82). DoubleDay.

External links
● 9,10-DiThioAnthracene – Wikipedia.