Meeting notice: The 00.01.04 meeting will be held at 7:30 p.m. at the Royal East (782 Main St., Cambridge), a block down from the corner of Main St. and Mass Ave. If you're new and can't recognize us, ask the manager. He'll probably know where we are. <-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-> Suggested topic: Open Mike <-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-> Nanonews: One of the long standing debates in NT is whether it makes more sense to begin by expanding the functionalities of cells or to plunge ahead with the effort to design a general purpose programmable mechanical assembler from the ground up. The first path hands you a free solution of the self- replication problem and the benefit of immediate access to a very wide range of intermediate applications or markets. However, it imposes the burden of puzzling out how to build on the "legacy functions" of cells so as to get cells to do things they have generally not cared much about, such as the synthesis of a wide range of inorganic materials (like metals) and the fabrication of inorganic structures. Recently the Materials Society held its convention in Boston. One of the presentations bore on this question. The following text is borrowed (I will return it when I am finished with it.) from Science Magazine, 24 December 1999, pp 2442-2444. The writer is Robert F. Service <-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-> ... two independent research teams, one led by materials scientist Mehmet Sarikaya of the University of Washington, Seattle, and the other by Angela Belcher, a chemist at the University of Texas, Austin, reported that they had used ... evolution to create proteins that could bind to tiny semiconductor and metal particles and assemble them into larger clusters. If the same protein- engineering techniques can generate molecules capable of organizing and patterning a wide variety of materials, proteins could become invaluable tools for crafting transistors, wires, and other electronic devices with components hundreds of times smaller than those on current computer chips. [...] Both Sarikaya and Belcher hoped to exploit the abilities that the proteins critical to forming bones, shell, and teeth display: They have the selectivity to bind only certain inorganics, seeding and organizing their growth into desired patterns. Abalone, for example, use separate proteins to organize calcium carbonate into different mineral phases: iridescent mother-of-pearl, or aragonite, for the shell's inner layers and rock-hard calcite for the shell's outer surface. Such naturally occurring proteins don't work well with many industrially important materials such as metals and semiconductors, however. So the Washington and Texas researchers decided to see if they could improve matters. For their part, Sarikaya and his Washington colleagues set out to coax bacterial proteins into binding to gold, which is used widely in the electronics industry. They started with multiporin, a cell membrane protein from the bacterium Escherichia coli that does not bind gold in its natural form. They then cloned the multiporin gene to make millions of copies. From each copy, they snipped out a section coding for a segment of the protein that forms a loop projecting from the E. coli membrane. That's where the protein would bind gold if its chemical makeup allowed it to do so. To alter the makeup of the loop, the researchers replaced the snipped- out gene segment with random DNA sequences produced by an automated DNA synthesizer. They then introduced the mutated genes back into bacteria, grew the bacteria, exposed them to gold particles, and--in a set of steps analogous to natural selection-- they washed off poor binders and regrew the better ones, eventually identifying the colony that did the best job of binding gold. Finally, they purified multiporin from these bacteria and attached the protein to the outer surface of both tiny plastic spheres and flat surfaces in solution. When they then spiked their mixture with a small amount of gold, the protein picked up the flecks, decorating either the outside of the spheres or dotting the surface. Belcher's group, meanwhile, took a different approach to evolving proteins that could bind to semiconductors, such as zinc selenide and gallium arsenide, which are also widely used in electronics. The team used an off-the-shelf kit containing 109 random DNA sequences, which they inserted into copies of a gene that codes for the outer coat of a bacterial virus called a phage. They then infected bacteria with the modified phages, allowed the phages to multiply, and exposed the viruses to a solution containing semiconductor particles to select the viruses best able to bind the semiconductor. Thus far, Belcher reported, the technique has worked beautifully. Her team has identified proteins that can discriminate between similar semiconductor alloys, such as gallium-arsenide versus aluminum- gallium-arsenide, and can even discriminate between different faces of the same semiconductor crystal, which have different arrangements of the atoms on the crystal surface. Down the road, she says, her team is planning to pattern the semiconductor-binding proteins on surfaces and use them to nucleate the growth of tiny semiconductor crystals in controlled arrangements. That's just what researchers around the globe are trying to do, in an effort to create ultrasmall transistors and other computing devices. And if Belcher and Sarikaya have their way, proteins may be just the handle they need to get there. <-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-> Announcement Archive: http://www.pobox.com/~fhapgood/nsgpage.html. <-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-><-> If you wish to subscribe to this list (perhaps having received a sample via a forward) send the string 'subscribe nsg' to majordomo@world.std.com. Unsubs follow the same model. Discussion should be sent to nsg-d@world.std.com, which must be subscribed to separately. You must be subscribed to nsg-d to post to it and you must post from the address from which you subscribed (An anti-spam thing). Comments, petitions, and suggestions re list management to: nsg@pobox.com