I’m just back from Shanghai, where I attended the 2^nd DNA nanotechnology workshop, a very exciting meeting at which we also celebrated the prestigious Albert Einstein professorship of the Chinese Academy of Sciences being awarded to Ned Seeman, often called ‘the father of DNA nanotechnology’. The story goes that as a young crystallographer, worried about getting tenure, he went to the campus bar to have a few beers and mull things over. Seeman found inspiration in the Escher woodcut Depth to make crystals using DNA, so as to avoid the guessing game (and potentially praying)­ that everyone who ever tried to crystallize anything is only too familiar with. The rest, as they say, is DNA nanotechnology.

The idea of hybridization — mixing two separate DNA strands to make a double helix — was reported in 1956 by Alex Rich, in a paper that incidentally very nearly fitted into a single column (half a page) of the journal! The beauty of the assembly lies in the precisely controlled positioning it enables at the nanoscale, and by carefully designing strands you can fold them up into increasingly complex designer structures (origami).

The meeting — whose theme was “From structure to function” — undeniably showed that DNA nanotechnology now branches out in many directions. We saw a wide variety of DNA items, triangle, cube, tetrahedron, octahedron, and even curved architectures; used for example to position other species (from gold nanoparticles to proteins); or manipulated to form nanomechanical devices such as tweezers, chopsticks-renamed-pliers, or walkers. These behaviours can in turn be used for example for guest recognition, detection, or to construct logic gates; make up DNAzymes (single-stranded DNA sequences that act as enzymes). It would be impossible to try and discuss here all the elegant structures and systems presented at the workshop, but I would like to mention an unusual one. Fritz Simmel from Munich looked into autonomous behaviours, and coupled DNA tweezers with oscillating systems. You will find more details at PNAS, 108, E784-E793 (2011) but essentially, they used transcription and RNA degradation reactions to induce, under the right conditions, the periodic opening and closing of DNA tweezers, making for a synthetic transcriptional clock.

There was also quite a lot of talk of cell studies — which perhaps shouldn’t be surprising as we are, after all, discussing DNA here. When it comes to therapeutic applications though, as William Shih mentioned, it is great to have new drugs but the hurdle we need to get passed is their delivery — how to get them in the cells? And so he’s exploring how the shape, size and function of DNA items affects the rate at which they are internalized.

The wide variety of DNA assemblies presented leaves no doubt that the field will only continue to get more exciting, and I look forward to seeing these developments and further branching out. I have to say as well that, for me, all of this made all the more exciting by being hosted at the Shanghai synchrotron facility!

Anne

Anne Pichon (Associate Editor, Nature Chemistry)

All good things come to an end… Among the many, and varied, aspects discussed at ICCOSS over the past few days, I wanted to bring your attention to halogen–halogen bonding, which seems to be becoming quite popular. When a halogen atom engages in such a bond, its charge distribution changes a little, leading to a ‘polar flattening’ of the atom. The more electronegative side of one atom naturally engages in a halogen–halogen bond with what has become the more electropositive side of the other. Can these interactions be relied on to assemble building blocks? Can they be tuned in a controllable manner by judicious choice of the halogen?

But the good old hydrogen bond was far from being left out. I enjoyed E. Arunan’s presentation about giving atoms a hydrogen bond radius. After all, covalent, ionic or van der Waals interactions have their covalent, ionic or van der Waals radii counterparts, so although by no means easy it may well be possible to do that for the hydrogen bond too.

Another exciting feature of the solid state is chirality – which turns out to be a lot more widespread that one might think. Bart Kahr had some surprising numbers for us: 8% of organic compounds naturally crystallise in a helical form, and about 25% can be made to do so! He showed a very nice movie of a crystal growing helically — but with an optical axis that moves during the growth process: twisting occurs at the tip, and at the same time the bulk untwists. This, he suggested, is probably associated with strains and stresses that are caused by the presence of an impurity.

From a theoretical perspective, R. Ramasesha showed us how he goes about modelling molecular materials for electronic applications – in a JACS paper from 1911 (very possibly the oldest paper cited at the conference) Moore and McCoy wrote that “it is possible to prepare composite metallic substances from non-metallic constituent elements”. This is exactly what organic electronics are.

But I’m not going to list all the topics discussed. Why not come and see for yourself at the next ICCOSS, held in Cardiff in July 2013!

I did want to mention the presentation by Hitoshi Kanazawa, Professor at Fukushima University, about 60 km from the Daichi nuclear power plant, who reported on the situation and how he and his group went around measuring radioactivity after the accident (this is not easy, as the values measured depend on where exactly you take the measurement, how far above the ground, the winds at that moment and so on). He also tried to find a way to rinse the radioisotopes but all attempts have so far remained unsuccessful. As we know, this accident has been a disaster, and sadly cleaning up will take for ever.

Hitoshi Kanazawa also had a very interesting poster – but I’ll refrain from telling you all about it, as the results are unpublished. I will only say that admiring some sample materials that he’d brought involved a syringe and a band aid, which certainly made for an enhanced poster experience.

And finally… for all of you out there who just love pretty crystals – I know it’s not just me – I have good news: our Ali Baba’s cave does exist. It is in Chihuahua State, Mexico – aptly named the Crystal Cave – connected to the NAICA mines. Dario Braga showed striking pictures throughout his presentation – these caves shelter crystals as big as trees! How did they form? You can find out at the website of the team of scientists and explorers who are studying – and protecting – these amazing crystals.

Anne

Anne Pichon (Associate Editor, Nature Chemistry)

This morning I went to some physical chemistry sessions on computational quantum chemistry. I won’t attempt to summarize the various interesting points raised by the speakers as well as the members of the audience, but I’d like to highlight one conclusion from Stefan Grimme’s presentation: he showed that dispersion corrections should really be used routinely – rather than occasionally – in density functional theory (DFT) methods. Pavel Hobza, who next took the stage, wholeheartedly agreed, saying in particular that these corrections play an extremely important role when it comes to biomolecules.

After another few talks in that session – including a very engaging presentation from Mark Gordon about his favourite molecule, water – I nearly didn’t make it to the sessions held in a different hotel because the roads were getting flooded… [well, yes, after I mentioned the lovely weather and warm temperatures it’s only fair to let you know that we did have a lot of rain today]. But all went well and I managed to see some anion coordination chemistry, including a photo of beautiful crystals growing in a supramolecular gel, from Jon Steed’s lab (photo that appeared recently in a certain chemistry journal). Steed’s group first form a supramolecular bis(urea) gel for which the gelation can be reversed by adding an anion. They then use the gel as a matrix for the crystallisation of organic compounds, and subsequently remove it (by anion addition) to collect the crystals. Gels are often mentioned as promising host matrices for drugs, and this approach could serve for pharmaceutical polymorph screening.

The last talks of the conference will be held tomorrow morning — and this also marks the end of Chemistry Week, as December 15-20 had been officially proclaimed by the Governor and Lieutenant Governor of the State of Hawai’i.

It has certainly been a great meeting, with engaging presentations and discussions as well as very enjoyable evenings – for example, we were treated to some traditional chanting and dancing not only from Hawaii but also from the other Polynesian countries. And this is how I got to see a real New Zealand Haka (well known to those who like to watch international rugby), a little before a ‘fire dance’ accompanied by fireworks on Waikiki beach…

The only thing is that I missed a few speakers that I really wanted to go and listen to – I may just have to come back in five years time!

Anne

Anne Pichon, Associate Editor (Nature Chemistry )

This past couple of days I have been attending more traditional, ‘core’ areas of chemistry at the inorganic, macromolecular and organic sessions. I first went to “the new age of advanced materials” symposium, and although I was fighting a little bit of jet lag and sleep deprivation (not a good combination) it made for a very interesting morning. Among exciting endeavours on helicity, supramolecular chirality, and controlled assembly and organization, Sam Stupp from Northwestern University showed interesting bioapplications with his supramolecular polymers, such as some neurotherapy studies that look promising against Parkinson’s disease.

In the inorganic sessions, I indulged in some metal–organic frameworks (MOFs) chemistry — these relatively young hybrid materials seem to be acquiring some maturity, rapidly moving to a new level of complexity and functionality. For example, Seth Cohen from University of California, San Diego, wishes that they could soon(ish) be used as scaffolds, in which just the right functional groups would be held in just the right place and orientation to mimic a metallo-protein active centre. Talking about bio-inspired applications, I particularly liked this comment from Ivan Huc that “mimicking isn’t copying”: scientist do get inspiration from nature – who controls activity, accessibility, or selectivity with remarkable precision – but rather than trying to reproduce the same functions they will then look to construct systems that do what nature cannot.

This morning I headed over to a ‘redox redux’ session on non-innocent ligands from an inorganic and an organometallic perspectives. Although as Cortlandt Pierpont reminded us they have been alluded to as far back as 1966, and described clearly in 1978, the role of these redox-active ligands had then not been mentioned much. They have recently been attracting attention, and I was happy to see elegant compounds and reactivities, including a combination of redox and acidic activities in Thomas Rauchfuss’ talk, or some unusual oxidation states [such as Pd and Pt(III), Ag(II), or Ni(III)] from Martin Schröder’s lab. Over on the organic side of things, a symposium dedicated to Bob Moss was also packed with intermediates and unusual molecules, and we saw in particular some pretty versatile reactivity from carbenes and nitrenes.

I’d like to borrow the (nearly) last thought for today from Eugenio Coronado at the University of Valencia, who showed some interesting studies in which monolayers – rather than molecules – serve as building blocks to prepare functional materials. He highlighted that this work requires a combination of inorganic, organic, coordination, supramolecular and surface chemistries, which fits nicely in the spirit of such a broad conference.

And finally… for those of you who haven’t finished their Christmas shopping, check out the Periodic Quest! Featuring two board games and about 4 or 5 card games – all centred about the elements, as the name suggests – this might just be the perfect present to keep busy with (chemistry-friendly) family and friends during those long winter nights (those what?)

Anne

Anne Pichon, Associate Editor (Nature Chemistry)

I am now – for the first time – in Hawaii, attending the Pacifichem meeting [officially the International Chemical Congress of Pacific Basin Societies] (I resisted the urge to start this post by “Aloha”, a word I’ve heard a lot in the past day or so). The meeting is huge: 275 symposia, more than 1,000 papers, 12,000 delegates! This is a ‘self-assembled’ conference, in which the symposia are organized ‘from the bottom up’ — each symposium is submitted by a group of organizers, from at least 3 countries from the Pacific rim (Canada – host country this year – the US, Japan, New Zealand, Australia, Korea and China). This makes for a very diverse meeting. The only thing is that it is a little hard to pick which sessions to go to, with speakers that overlap. Also, should I go to topics I’m familiar with, such as the inorganic or macromolecular sessions, or plunge into the much less familiar?

According to our chairman, this year Pacifichem encouraged symposia at the interface between chemistry and other topics, such as health, environment and alternate technologies, where chemistry plays a leading role. In this spirit, today I attended parts of the sessions on analytical and environmental chemistry in human health; generation of hydrogen from water; and nanoparticle-based materials – and really enjoyed this variety. In the nanoparticle-based materials session, for example, we heard interesting approaches on how inorganic synthesis could be harnessed to control the properties, and pattern, particles. One talk that stood out for me was that of Terry Bigioni, from the University of Toledo. Usually, with nano-clusters, obtaining a uniform morphology and narrow size distribution is what matters — as Bigioni said, no-one is going to notice if you are missing about a hundred atoms. Today, however, he talked about magic (close-shell) clusters, in which every atom counts. These particularly stable sizes have been identified for gold [see for example this cluster reported in Science by Kornberg and co-workers], but much less is known about silver. Bigioni showed that, under wet chemical syntheses, silver clusters also form discrete clusters of specific sizes. These seem to share some of the stability rules of the gold clusters, but only to some extent, suggesting that there is more to the story than an extension of the gold clusters’ reactivity…

I also very much enjoyed the opening ceremony in the evening, at which Paul Corkum gave a wonderful talk that made physical chemistry very exciting, and even approachable. We can normally look at either the dynamics (femtochemistry) or structure (X-ray diffraction) of a particular system. In his lecture, Corkum talked about how new laser-based ways to image matter might soon make it possible to ‘film’ orbital changes during a chemical reaction, and perhaps make a 3D molecular movie. In the same way as the first film (‘The Horse in Motion’) made the cover of Scientific American in 1878, Corkum predicts the first ‘molecular movie’ will be on the cover again by 2018… Only eight years left! Exciting times.

Overall, a warm welcome from Pacifichem — and I’m not just talking about the temperature. I certainly look forward to the rest of the week, including some inorganic and macromolecular sessions.

Anne

Anne Pichon, Associate Editor (Nature Chemistry )

I am now – for the first time – in Hawaii, attending the Pacifichem meeting [officially the International Chemical Congress of Pacific Basin Societies] (I resisted the urge to start this post by “Aloha”, a word I’ve heard a lot in the past day or so). The meeting is huge: 275 symposia, more than 1,000 papers, 12,000 delegates! This is a ‘self-assembled’ conference, in which the symposia are organized ‘from the bottom up’ — each symposium is submitted by a group of organizers, from at least 3 countries from the Pacific rim (Canada – host country this year – the US, Japan, New Zealand, Australia, Korea and China). This makes for a very diverse meeting. The only thing is that it is a little hard to pick which sessions to go to, with speakers that overlap. Also, should I go to topics I’m familiar with, such as the inorganic or macromolecular sessions, or plunge into the much less familiar?

According to our chairman, this year Pacifichem encouraged symposia at the interface between chemistry and other topics, such as health, environment and alternate technologies, where chemistry plays a leading role. In this spirit, today I attended parts of the sessions on analytical and environmental chemistry in human health; generation of hydrogen from water; and nanoparticle-based materials – and really enjoyed this variety. In the nanoparticle-based materials session, for example, we heard interesting approaches on how inorganic synthesis could be harnessed to control the properties, and pattern, particles. One talk that stood out for me was that of Terry Bigioni, from the University of Toledo. Usually, with nano-clusters, obtaining a uniform morphology and narrow size distribution is what matters — as Bigioni said, no-one is going to notice if you are missing about a hundred atoms. Today, however, he talked about magic (close-shell) clusters, in which every atom counts. These particularly stable sizes have been identified for gold [see for example this cluster reported in Science by Kornberg and co-workers], but much less is known about silver. Bigioni showed that, under wet chemical syntheses, silver clusters also form discrete clusters of specific sizes. These seem to share some of the stability rules of the gold clusters, but only to some extent, suggesting that there is more to the story than an extension of the gold clusters’ reactivity…

I also very much enjoyed the opening ceremony in the evening, at which Paul Corkum gave a wonderful talk that made physical chemistry very exciting, and even approachable. We can normally look at either the dynamics (femtochemistry) or structure (X-ray diffraction) of a particular system. In his lecture, Corkum talked about how new laser-based ways to image matter might soon make it possible to ‘film’ orbital changes during a chemical reaction, and perhaps make a 3D molecular movie. In the same way as the first film (‘The Horse in Motion’) made the cover of Scientific American in 1878, Corkum predicts the first ‘molecular movie’ will be on the cover again by 2018… Only eight years left! Exciting times.

Overall, a warm welcome from Pacifichem — and I’m not just talking about the temperature. I certainly look forward to the rest of the week, including some inorganic and macromolecular sessions.

Anne

Anne Pichon, Associate Editor (Nature Chemistry )