[小组图标] The Hilbert curve
来自: 蔡鸟(20091212 20200930)
COVER First described by David Hilbert in 1891, the Hilbert curve is a one-dimensional fractal trajectory that densely fills higher-dimensional space without crossing itself. A new method for reconstructing the three-dimensional architecture of the human genome, described on page 289, reveals a polymer analog of Hilbert's curve at the megabase scale. Image: Leonid A. Mirny and Erez Lieberman-Aiden Picture from http://www.sciencemag.org/content/vol326/issue5950/cover.dtl Science 9 October 2009: Vol. 326. no. 5950, pp. 289 - 293 DOI: 10.1126/science.1181369 Reports Comprehensive Mapping of Long-Range Interactions Reveals Folding Principles of the Human Genome Erez Lieberman-Aiden,1,2,3,4,* Nynke L. van Berkum,5,* Louise Williams,1 Maxim Imakaev,2 Tobias Ragoczy,6,7 Agnes Telling,6,7 Ido Amit,1 Bryan R. Lajoie,5 Peter J. Sabo,8 Michael O. Dorschner,8 Richard Sandstrom,8 Bradley Bernstein,1,9 M. A. Bender,10 Mark Groudine,6,7 Andreas Gnirke,1 John Stamatoyannopoulos,8 Leonid A. Mirny,2,11 Eric S. Lander,1,12,13, Job Dekker5, We describe Hi-C, a method that probes the three-dimensional architecture of whole genomes by coupling proximity-based ligation with massively parallel sequencing. We constructed spatial proximity maps of the human genome with Hi-C at a resolution of 1 megabase. These maps confirm the presence of chromosome territories and the spatial proximity of small, gene-rich chromosomes. We identified an additional level of genome organization that is characterized by the spatial segregation of open and closed chromatin to form two genome-wide compartments. At the megabase scale, the chromatin conformation is consistent with a fractal globule, a knot-free, polymer conformation that enables maximally dense packing while preserving the ability to easily fold and unfold any genomic locus. The fractal globule is distinct from the more commonly used globular equilibrium model. Our results demonstrate the power of Hi-C to map the dynamic conformations of whole genomes. ================================================= 无意中发现一个网站,东京大学的研究人员用1000000个小细胞胶囊堆积起来,放在一个模子里,组成了一个小人的,目的很简单,就是为了验证一种新的活细胞三维呈像系统。这些细胞胶囊是由表面覆盖了几十个皮肤细胞的胶原蛋白组成的。据说这个小人形状的“组织”,在陪液中也活了好几天。当然研究员并不只是想测试这个成像系统,他们更大的愿望是想重塑组织,还有就是发展生物医药。 原文摘自 http://www.pinktentacle.com/2009/01/tiny-doll-made-of-living-cells/ 不过我觉得评论也很有意思,贴在这里一篇,大概是作者的回复,她看到有人说照片是ps的,气疯了 ;) Strychnos 2009.01.23 ::: 21:52 You utter utter good for nothing, waste of human skin morons. Yes you Oz and Phil. If I see another post that says photoshopped I think I’m going to sell my computer and go and live as a hermit off the land somewhere where I don’t have to come across idiots like you. There is no reason to photoshop this. They do not claim that the little green mass of cells can get up and walk off (or bounce around as the flubber bit suggests). The shape is purely jeewhizz and arbitrary (thats the meaning of ‘mold’). They are illustrating a principal. Please note the granulation on the figure; that will account for the little micro capsules. Also note that this photograph was taken ‘in situ’ which means it is still floating in or submersed in whatever medium it is in. Given the small size (5mm) means that they probably photographing through a microscope. This image is both top and back lit, which, together with the constraints placed by photographing under a microscope accounts for the strange glowing effect. Now commenting on the usefulness of this experiment would make more sense. Personally I can’t see it and I suspect the gist was omitted from the article (or maybe it was lost in translation). It does not state whether any physiological processes were in operation and how they jugged the doll to be alive. How is it different taking single cells and clumping them together? This article hints at multi-cellular organization, i.e. creating tissue and not just single cells. For any functional organization this assumes chemical exchange (purposeful chemical exchange?) between the cells. What I’m getting at is that this article says nothing. It was either pounced on by some journalist seeking a fantasy story or a lab seeking cheap publicity threw it out there.
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