Tag Archives: Science

Organotextile catalysis

Ji-Woong Lee, Thomas Mayer-Gall, Klaus Opwis, Choong Eui Song, Jochen Stefan Gutmann, and Benjamin List
Science
DOI: 10.1126/science.1242196

list1

I’ve written a research highlight for Nature Chemistry talking about Opwis’ and List’s recent paper on organotextile catalysis in Science. Take a look.

Catalytic cloth

Image credit: © 2013 American Association for the Advancement of Science

Advertisements

A paramagnetic/diamagnetic molecular switch

Fraser Stoddart’s group have reported a catenane molecule that can be oxidised to a stable paramagnetic radical state. The oxidation states of the molecule are easily configurable, so this structure has significant potential for use in data storage on the molecular level.

From the Chemistry World article:

The key to the stability of the new radical compound is the mechanical bond that links the two macrocycles, forcing the charged species to remain close. And that proximity means that the molecule never oxidises to a fully charged species but stops at the paramagnetic species •7+. That, says Barnes, is because the molecule is trying to minimise the charge in the centre where the two catenanes link. ‘The charged units have no choice but to interact with one another,’ explains Barnes, so it holds on to that remaining electron to reduce the charge repulsion.

But while the •7+ species is paramagnetic, all the other charged species are diamagnetic, as the electrons spins pair. Using cyclic voltammetry it is possible to quickly switch between the paramagnetic and diamagnetic states by adding and removing electrons. And it is this simple switching that could be the key to a potential application of the material: memory storage.

DOI: 10.1126/science.1228429

Sequence-Specific Peptide Synthesis by an Artificial Small-Molecule Machine

Bartosz Lewandowski, Guillaume De Bo, John W. Ward, Marcus Papmeyer, Sonja Kuschel1, María J. Aldegunde, Philipp M. E. Gramlich, Dominik Heckmann, Stephen M. Goldup, Daniel M. D’Souza, Antony E. Fernandes, and David A. Leigh
Science
DOI: 10.1126/science.1229753

Chemical synthesis has advanced by an order of magnitude in the last two decades. So much so that the once groundbreaking field of natural product synthesis has become a relatively bland arena with occaisional highlights. Many synthetic chemists have turned their attention to far grander designs, passing over the mimicking of nature, and focusing their efforts on manipulating molecules ever more precisely.

Nowhere has this been demonstrated more clearly than in the development of complex molecular machines. Chemists have employed advances in synthesis to construct molecules that rotate in only one direction, walk along a track, and even change physical properties when irradiated with light. However, the field of nanotechnology has suffered from a lack of credibility in its creations: we have yet to make a molecular machine that does something useful.

This week, a report from Leigh and co-workers has taken a large step in addressing this problem, who in doing so have gone back to copying the functions of nature to inspire their designs.

Their machine mimics the function of the ribosome, taking amino acid building blocks in sequence and constructing a predefined peptide. This involes using two carefully interlocked molecules: a macrocycle with a thiolate-supporting arm and a ‘dock’ for amino acids; and a ‘track’, along which the macrocycle moves, that is functionalised at points with a defined set of amino acids. Once the machine is assembled, the macrocycle moves along the track cleaving the amino acid building blocks one at a time and docking them together in sequence. Once free of the track, the peptide can be removed from the macrocycle and isolated.

With such encouraging steps towards creating useful systems, it’s fascinating to think about what other uses this technology could be put to. The article is well worth reading to understand the chemical makeup of this machine and its function. (It’s unfortunately to complex to reproduce here.)