Reporting in the Journal of the American Chemical Society, they use what they call 'proton grease' to make a molecular rotor spin faster – by a factor of ten million. The advance is a significant signpost on the road toward functional synthetic molecular machines, said Ken Shimizu, lead author and professor in the department of chemistry and biochemistry in the College of Arts and Sciences at USC.
The team constructed their rotor by combining quinoline and succinimide subunits. At first blush it might look like rotation in the resulting molecule would be essentially unrestricted, but the appearance is deceiving. The partial charge on the carbonyls has highly unfavorable overlap with the quinoline nitrogen when the molecule is in a planar transition state.
But when the nitrogen is protonated, the planar rotamer is stabilized – leading to a huge increase in the rotational rate.
"We designed it to have more favorable overlap after protonation, so we expected it to speed up," said Shimizu. "But we never anticipated the magnitude of the increase – we were surprised by how well it worked, which is a rare thing to say."
The barrier to rotation dropped from about 22 kcal/mol to 13 kcal/mol upon titration with acid. The increase in rotation speed was so dramatic, covering seven orders of magnitude, that the team had to cobble together two different measurement techniques – one for fast rotation, and another for slow.
And as they show in their research article, the speed-up is reversible: addition of base restored the barrier to rotation.
The field of molecular devices is in its infancy, but the possibilities are tantalizing. "We're kind of making cogs right now, but we're moving toward being able to make more complex devices," said Shimizu. "People are imagining all sorts of electronic and mechanical devices based on single molecules, and we're building up this toolbox to be able to create machines and devices on the molecular scale."
Despite coming up with the evocative term 'proton grease,' Shimizu recognizes the name carries potential baggage as well. "It makes it more accessible to use these analogies about brakes and grease and things like that – but it's a little bit dangerous too," he said.
"When people talk about in these molecular machines, they often assume that you can take an engine, for example, and just scale it down to a molecular size. And conceptually you can, but the actual physics behind that falls apart," said Shimizu. "We don't have friction at that scale, for example."
"But that's actually the most exciting part, too," he added. "When you start making things on that scale, the rules are completely different."
"By controlling motion on the molecular level, people imagine that you could make switches, memory, transformers – all sorts of electronic and mechanical devices as single molecules."
Steven Powell | Newswise Science News
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
21.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
21.08.2017 | Materials Sciences
21.08.2017 | Health and Medicine
21.08.2017 | Materials Sciences