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Last friday I attended a talk, which was organized by the munich center for nanoscience<\/a>. The talk was given by Tim Liedl from the Shih Laboratory<\/a>.<\/p>\n After a short motivation about the possible commercial applications, which are mainly of pharmaceutical nature he started out describing a joint work<\/a> with the center for nanoscience, Bell labs and the munich Biomolecular Systems and Bioelectronics group<\/a>. In the work a DNA-switchable polyacrylamide (PAAm) hydrogel is used for controlled trapping and release of fluorescent quantum dots<\/a>. <\/p>\n At the beginning of the experiment the researchers copolymerized two “noncomplementary Acrydite-modified oligonucleotides<\/a>” seperately with acrylamide, mixed the two solutions in order to obtain a highly viscous fluid and then complemented the fluid with fluorescent colloidal semiconductor quantum dots as tracer particles. You can imagine a liquid where the quantum dots are little beaming fluorescent dust particles (a bit like in here<\/a>). In particular the quantum dots are easy to track with fluorescence microscopy and fluorescence correlation spectroscopy and in fact Tim Liedl could even present a video showing the experiment. After mixing the liquid the researchers added with a pipette socalled “gelation oligonucleotides complementary to the Acrydite strands” which transformed the fluid PAAm\/nanoparticle mixture into a solid gel and thus trapped the beaming particles along the path of the pipette. So the quantum dots formed a more or less sculptural beaming structure (the particles cease to diffuse) within the liquid. I.e. the addition of the gelation oligonucleotides induced crosslinking of the DNA modified polyacrylamide strands or in simple words: the gel clogs together where the gelation oligonucleotides had been inserted. This process is reversible that is the DNA crosslinker strands are equipped with an additional \u201ctoehold\u201d section that acts as a \u201crecognition tag\u201d for socalled DNA release strands. When release DNA is added to the gel, it gets attached to the toeholds and removes the crosslinker strands via branch migration und thus the gel is again liquid. <\/p>\n The possible commercial applications for this kind of research is formulated by the researchers as<\/p>\n Our work demonstrates that a DNA-cross- I am not sure but I think Tim Liedl mentioned also a report by nanomarkets After the hydrogel experiment Tim Liedl gave a little overview about DNA origami, which already gained quite some attention last but not least since the funny DNA smiley<\/a> by Paul Rothemund<\/a>. However the field goes back to the eighties by work of pioneers such as Nadrian C. Seeman, see e.g. this article from 1994<\/a> with Yuwen Zhang where among others a DNA- truncated octahedron was presented. See also the links on the wikipedia site<\/a>. The article “Conformational flexibility facilitates self-assembly of complex DNA nanostructures<\/a>” by Chuan Zhang*, Min Su\u2020, Yu He*, Xin Zhao\u2020, Ping-an Fang\u2020, Alexander E. Ribbe*, Wen Jiang\u2020, and Chengde Mao*\u2021 holds nice images, so does the gallery<\/a> of the computersoftware company nanorex. While talking about computer software one should also mention the molecular programming project<\/a> who just got a little money boost. A nice review oriented towards the material aspects can be found in the article Review Constructing novel materials with DNA <\/a>(via metamodern<\/a>).<\/p>\n Some of the above mentioned researchers by the way wrote an essay “From DNA nanotechnology to synthetic biology<\/a>” however biobricks<\/a> (->wikipedia link<\/a>) was not mentioned.<\/p>\n After that Tim Liedl reported about experiments of attaching metal atoms to DNA strands, which may be important for using DNA as a conductive material. However a collegues of Tim Liedl, whose talk was right before him, so that I catched the very last minutes seemed to have covered this type of research. He actually seemed to have also used the insertion of (cadmium?) atoms in between double strands in order to control the bending of the helix, so that I suggested to use this for constructing a triple-stranded DNA<\/a>, which he found would be an interesting experiment.<\/p>\n Tim Liedl than began to talk about very new work, where an article is soon to be published using socalled 6-helix bundles. 6-helix bundles are tubes where 6 (double-stranded? scaffolded?) DNA helices interlink. Visualize a perpendicular cut helix viewed from above as a thick dot then the six helix dots of the six helices lie in the corners of a hexagon (see also the abstract image). I actually would like to learn a bit more about 6-helix bundles, there seems to be a good article on that Six-Helix Bundles Designed from DNA<\/a>, but it costs $30.00 for 48 hours of access. In particular involved combinatorics sounds interesting, it seems to play a part in the selfassembly:<\/p>\n We present a designed cyclic DNA motif that consists of six DNA double helices that are connected to each other at two crossover sites. DNA double helices with 10.5 nucleotide pairs per turn facilitate the programming of DNA double crossover molecules to form hexagonally symmetric arrangements when the crossover points are separated by seven or fourteen nucleotide pairs. We demonstrate by atomic force microscopy well-formed arrays of hexagonal six-helix bundle motifs both in 1D and in 2D.<\/p><\/blockquote>\n
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\nlinked PAAm gel could be used to release nanoparticles as
\npotential drug-delivery vehicles in response to the presence
\nof trigger DNA or RNA molecules.\n<\/p><\/blockquote>\n
\n<\/a> in which a market for drug delivery in the range of 100 million $ (?…I am not going to pay 250$ to check that number) was envisaged. So no wonder that there are already patent plagues<\/a> on DNA hydrogels<\/a> by…Motorola.<\/p>\n
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