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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 http://www.nature.com/naturebiotechnology 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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