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By using a magnetic field generated by radiofrequency radiation to heat up gold nanocrystals bound to a specific DNA site, Kimberly Hamad-Schifferli, Shuguang Zhang, and Joseph M. Jacobson at MIT, and coworkers were able to disrupt DNA base pairing reversibly at that site [Nature, 415, 152 (2002); C&EN, Jan. 14, page 22]. In separate work, Zhang's group also created peptide nanotubes this year [Proc. Natl. Acad. Sci. USA, 99, 5355 (2002); Nano Lett., 2, 687 (2002); C&EN, April 15, page 39]. M. G. Finn, John E. Johnson, and coworkers at Scripps mutated a virus' coat protein so metal clusters or organic molecules could be attached to the viral surface [Angew. Chem. Int. Ed., 41, 459 (2002); C&EN, Feb. 4, page 10]. They used the decorations as chemical "glues" to form macroscopic viral arrays with defined nanoscale surface properties. Another technique for precisely ordering nanoparticles on the macroscale was devised by Angela M. Belcher (now at MIT) and coworkers at the University of Texas, Austin. They found that viruses engineered to bind zinc sulfide quantum dots self-assemble into highly ordered, 3-D liquid-crystal films [Science, 296, 892 (2002); C&EN, May 6, page 12]. Northwestern's Chad A. Mirkin and the University of Chicago's Milan Mrksich and coworkers used a technique called dip-pen nanolithography to create nanoarrays of single proteins with 100- to 350-nm diameter spots--the first nanoarrays made on such a small scale [Science, 295, 1702 (2002); C&EN, Feb. 11, page 6]. Each arrayed protein binds to complementary species with little nonspecific adsorption, suggesting biorecognition and biodetection applications. Mirkin and coworkers also used dip-pen nanolithography to directly pattern DNA on a variety of surfaces, including metals and oxides [Science, 296, 1836 (2002); C&EN, June 10, page 34]. Potential applications include high-density gene chips, nanoscale circuits, photonic crystals, and catalysts. The first artificial, single-molecule machine that converts light to physical work was developed by Hermann E. Gaub of the University of Munich and coworkers [Science, 296, 1103 (2002); C&EN, May 13, page 6). The light-induced contraction of a polymer molecule generates enough energy to deflect the cantilever of an atomic force microscope, generating a signal. And organic-based nanocavities of tunable size were created by Bing Gong of SUNY Buffalo and coworkers [Proc. Natl. Acad. Sci. USA, 99, 11583 (2002); C&EN, Aug. 26, page 30]. They might prove useful for catalysis, drug delivery, and ion-carrier applications.
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