العناكب النانوية
لقد اخترع الفهماء روبوتات مجهرية من جزيئات الحمض النووي التي يمكنها المشي ، والدوران ، وحتى خلق منتجات صغيرة خاصة بهم على خط تجميعى نانوي النطاق.
والأجهزة التى تأخذ بالألباب والواردة في مجلة تخصصر ، قد يؤدي يوما ما إلى حشد جيوش من الروبوتات الجراحية التي يمكنها تنظيف شرايين الإنسان أوبناء مكونات لحاسوب . في واحدة من المشاريع لفريق من جامعة كولومبيا في نيويورك أدت إلى إنشاء واحدا من العنكبوتات النانوية قطره فقط أربعة نانومتر. أى حوالي ۱۰۰,۰۰۰ مرة أقل من قطر شعرة رأس الإنسان.
العناكب النانوية تتحرك على طول مسار يضم شرائط مخيطة معا لخيوط من الحمض النووي الذي هوأساسا بطبيعة الحال مبرمج مسبقا. المسار للحمض النووي هو تعقب حلزوني مزدوج الجزيء -- وهوهجريب هيكلى من أربع مواد كيميائية المقترنة في أزواج.
'بفتح خط الحمض النووي ينتهي بك الأمر مع مسار يمكن استخدامه مثل ترس ما في آلية يمكن تصورها. وتلعب دورا مهما يمكن ان تتحرك حوله التروس ، شريطة حتى تنسجم معا. باستخدام الخيوط التي تتوافق مع التسلسل في المسار ، يمكن للروبوت المشي ، والاتجاه يسارا أوحق ينجذب كيميائيا على الإمتداد المطابق التالى. جسم العنكبوت 'هو بروتين مألوف يسمى streptavidin . وملتصق به ثلاثة أرجل من 'الحمض النووي الأنزيمي منفرد الجديلة ، الذي يرتبط ومن ثم يفصل تسلسل معين من الحمض النووي. الرجل الرابعة هي جديلة تجذب العنكبوت كحبل المرساة إلى نقطة البداية.
By 'unzipping' the DNA you end up with a track that can be used rather like the teeth in a clockwork mechanism. A cog can move around the teeth, provided it meshes with them. By using strands that correspond to sequences in the track, the robot can be made to walk, turn left or right as it is biochemically attracted to the next matching stretch. The spider's 'body' is a common protein called streptavidin. Attached to it are three 'legs' of single-strand enzymatic DNA, which binds to, and then cuts, a particular sequence of DNA. The fourth leg is a strand that anchors the spider to the starting point. Study leader Milan Stojanovic said: 'After the robot is released from its start site by a trigger strand, it follows the track by binding to and then cutting the DNA strands.' Once the strand is cut, the leg starts reaching for the next matching stretch of DNA in the track. In this way, the spider is guided down the path set by the researchers. Eventually, the robot encounters a patch of DNA to which it can bind but cannot cut. At that point, it is immobilised.
To watch the spider in motion, the researchers used atomic force microscopy which showed the molecular robots following four different paths. Molecular robots have drawn huge interest because of the allure of programming them to sense their environment and react to it. For instance, they could note disease markers on a cell surface, decide that the cell is cancerous and needs to be destroyed and then deliver a compound to kill it. Other DNA walkers have been developed in the past, but they have never ventured more than a few steps, said Hao Yan, a professor at Arizona State University. Professor Yan said: 'This one can walk about to about 100 nanometers. That's roughly 50 steps.'
The next step is how to make the spider walk faster and how to make it more programmable, so that it can follow many commands on the track and make more decisions. In a separate study reported in Nature, Nadrian Seeman and colleagues from New York University said they had built a prototype molecular factory.
They used a number of DNA robots to assemble gold particles in different ways in response to chemical commands.
DNA walkers moved past three kinds of DNA machines that handed them a cargo of gold nano-particles, which are clutched with three 'hands'. 'This is the first time that systems of nano-machines, rather than individual devices have been used to perform operations, constituting a crucial advance in the evolution of DNA technology,' said Lloyd Smith, from the University of Wisconsin at Madison, in a commentary also published by Nature. Nearly £6billion is being invested in research and development of nano products worldwide, according to the Project on Emerging Nanotechnologies, which tracks environmental and health
Read more: http://www.dailymail.co.uk/sciencetech/article-1278133/Meet-nano-spiders-The-DNA-robots-day-walking-body.html#ixzz0o8SOkDus
