At the massachusetts institute of technology mit

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Unformatted text preview: s, in which proteins function as templates to control the deposition of calcium carbonate–based materials with precision and crystallographic specificity. Belcher wanted to be able to exert the same level of control over other types of material, particularly those with interesting electrical or optical properties. But, she notes, biological systems are equipped to handle only a few elements—most of the periodic table is virtually untouched, and untouchable, by nature. So she turned to phage display as a way to evolve and select proteins with the ability to recognize other elements, starting with some used in the semiconductor industry. She showed in 2000 that she could evolve peptides to bind a range of semiconductor surfaces with high specificity and with particular crystallographic orientation4. She has gone on to show that the bacteriophage M13 can be made to pick just about up anything and organize it into nanoscale structures. Recently, she showed that quantum-dot nanowires could be grown on the head of M13 virus particles, which self-assemble into different orientations and phases5. So perfect were the crystals, she says, that she could shine a laser through the film and see a diffraction pattern on the wall (Fig. 4). This kind of precision will be 1140 Figure 4 Images of engineered virus directing nanocrystal synthesis. (a) Wild-type virus (no engineered insert). (b) Engineered virus nucleating nanowires. (c) Scanning transmission electron microscope image of a straight region of a viral nanowire at high magnification showing tightly packed nanocrystal morphology. Insert: Electron diffraction pattern. Image courtesy of Angela Belcher, Massachusetts Institute of Technology. hard to achieve with other kinds of nanomanufacturing processes. In addition, Belcher is looking for routes to build new materials on the nanoscale using conditions that are environmentally friendly—no organic solvents, or extremes of temperature and pH. Belcher has formed a company (Semzyme, Cambridge, MA, USA) to exploit her work with biomimetics, and she is part of the newly announced Institute for Biotechnology Collaboration, which joins researchers at MIT, Caltech (Pasadena, CA, USA) and the University of California, Santa Barbara (UCSB, Santa Barbara, CA, USA). Laura DeFrancesco VOLUME 21 NUMBER 10 OCTOBER 2003 N ATURE BIOTECHNOLOGY F E AT U R E © 2003 Nature Publishing Group Box 2 Bottom-up or top-down? Two distinct strategies have been used to explore the nanometer domain (i.e., 1–100 nm)—often referred to as ‘bottom-up’ and ‘top-down’ development. For the former, nanoscale materials are assembled from smaller molecular and atomic components. Here, nanomaterials, such as quantum dots and nanobars, can be synthesized or designed layer by layer, blending techniques from chemical engineering and material science. The innovation lies in precise control of the material’s size and resulting optical and electro...
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