SCIENCE
Molecular Computers Are Far from Realization Conference finds components are impossible to construct; promoters urge research to develop use of biological molecules as sensors Given that they were the subject of a five-day conference, a small wave of hype seems inevitable for socalled molecular computers. There are claims for the miraculous things they will be able to do compared to present computers, and suggestions that if only research funding were adequate—that is, a lot higher than at present—they would be closer to realization than they are. The idea behind chemically based computers is to replace the familiar silicon chips of current computers with large synthetic organic molecules or natural or custom-designed proteins produced using recombinant-DNA technology. In either case, the resultant computers would be orders of magnitude smaller and faster than current computers, their advocates claim. But at many levels of organization, such computers currently are barely a step removed from science fiction, and even the simplest of their components impossible to construct. Even their promoters aren't at all sure that they could do anything particularly fantastic. And with the current state of sophistication of silicon-based computers, such new technologies probably aren't needed. But such reservations tend to get muted when a group of scientists get excited about new ideas. Those were the impressions surfacing from a week-long conference on chemically based computing held late last month in Santa Monica,
Higgins: can't at this time compete Calif. The conference was organized by Crump Institute for Medical Engineering of the University of California, Los Angeles, and it brought together about 30 physicists, chemists, biologists, and computer scientists. The National Science
Yates: we must emulate biology
Foundation funded the conference to find out whether research into chemically based computers is a promising field to support. The straightforward answer to that question, even the enthusiastic conference participants admitted, is: Not really. But that simple answer was stated in muted terms, drowned in a succession of "gee whiz" tales of artificial intelligence, the computational potential of biological molecules, the possibilities for using arrays of organic molecules for computation. Much press coverage of the conference, for example, emphasized future computers billions of times more powerful than current computers and using only a tiny fraction of the energy. In the case of biochips—proteinbased chips—advocates sometimes claim some pretty remarkable additional possibilities. Biochip computers might be able to design and repair themselves, evolve, show emotions, and serve as the basis for true artificial intelligence. The computer conference opened with a press conference. For the conference participants, that day was organizational. On the second day, the participants broke into four workshops—physics, chemistry, biology, and computer science—to anaylyze chemically based computing from those four perspectives. On the third and fourth days, the four workshops presented their findings. Each presentation was preceded by a plenary talk. The fifth day was devoted to summing up. The afternoon session devoted to the chemistry group is illustrative of the tone of the conference. The plenary talk was given by Forrest L. Carter, a scientist with the chemistry division of the Naval Research Laboratory, Washington, D.C. It was essentially the talk that Carter has November 14, 1983 C&EN
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CIRCLE 38 ON READER SERVICE CARD November 14, 1983 C&EN
been giving for some time. He presented a series of remarkable looking molecules that he says could act as molecular switches. Many of them are highly conjugated organic molecules—either long chains similar to polyacetylene or very large ring systems—that, Carter says, one could somehow excite and have the double bonds do flip-flops into different positions, thereby acting as an on/off switch. Carter admits he wouldn't want to tackle the nearly impossible task of synthesizing the molecules he has drawn on papçr and that, once synthesized, it might be a bit difficult hooking the molecules up in the arrays he describes. Then there is the problem of how to excite a single, specific molecule. "Does one use light?" someone at the conference asked. "Maybe," said Carter. How? It can be worked out, he said. But there are fundamental physical laws that suggest that it would be, at best, extremely difficult. And all those highly conjugated systems with the double bonds alternating with the single bonds on paper: Aren't those electrons pretty well delocalized? Is it really known that they are either here or there so that they can be flip-flopped around as a switch? Carter shrugged. ' Other scientists at the conference recognized these and many other problems. Joseph J. Higgins, an associate professor of biophysics and biochemistry at the University of Pennsylvania, presented the findings of the chemistry workshop to the conference. Single molecules as switches won't work, the workshop found. Once one starts using collections of molecules as the switch, Higgins said, the scales of the resultant chips do not offer advantages over silicon chips, which are already well developed and which work extremely well. It is an interesting area to study in its own right, Higgins pointed out, but molecular computers "can't at this time compete with silicon." One promising area that should be developed, the chemistry workshop found, is the use of biological molecules as chemical and biological sensors. The idea would be to harness the exquisite pattern recognition ability of some proteins for
sensing specific molecules at very low concentrations. Apart from its obvious utility, developing such a technology would solve some of the initial problems of developing a computational device based on biological molecules. But that practical and realistic suggestion followed the sensationalism and tended to get lost. That's the way the conference went. The computer science and the biology workshops seemed to address two related questions. One was whether computer science could shed any light on the mechanisms of biological computing. The other was whether any computer science questions can be addressed using biological mechanisms as models. Both are significant questions, and the consensus of both groups seemed to be that the answer to each question was no. Those negatives, however, also got somewhat lost in the plenary talks and disputes about whether organisms actually "compute." (The computer science group felt it was clear they did, and the biology group felt it was stretching the term because the algorithm was not separable from the organism's structure.) Despite those negatives, F. Eugene Yates, head of Crump Institute, said in his summary on the last day of the conference that "technologically, sooner or later, we must emulate biology." The basis of the statement was that biological logic elements are more complex than the simple on/off of present binary computational systems based on silicon chips and thus require far fewer elements, and that biological systems such as enzymes possess an inherent threedimensional pattern recognition capability that the essentially twodimensional arrays of silicon lack. But it seems that the original point of the conference got lost. The questions the conference was supposed to address all were answered in the negative. But the outcome of the conference was a significant amount of press coverage about the incredible potential of molecular computers, and a call, on the last day of the conference, for two more conferences to address subsidiary questions that arose during it. Rudy Baum, San Francisco
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CIRCLE 37 ON READER SERVICE CARD November 14, 1983 C&EN
study genetics of aging
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Recently, a company called Senetek was set up to learn more about the genetic mechanisms that occur during the aging process and to atTwo ACS tempt to correlate these changes to Congressional cellular protein chemistry. Fellowships Senetek, a contraction of "senesAvailable To Begin cence" and "technology," is headquartered in London. Launched Fall 1984 with venture capital funding of some $1.7 million, its aim is to encourage basic research into the underlying factors that control aging The objectives of the fellowship and to use the knowledge for develprogram are: oping new products and techniques • To provide an opportunity for scientists in this and related areas for detectto gain firsthand knowledge of the op ing and combating human diseases. erations of the legislative branch of the federal government, The expectation is that there will • To make available to the government be commercial spinoff from the an increasing amount of scientific and work. It's likely, for instance, that a technical expertise, and standardized set of polymer gels will • To broaden the perspective of both the become available for two-dimensionscientific and governmental com al separation of cell proteins. Anothmunities regarding the value of such er possibility is the development of scientific-governmental interaction. simple devices to quantify insulin, interferon, and growth hormone. Central to Senetek's effort will Applications should be submit be the work of a team of chemists ted by January 31, 1984 to: and molecular biologists at Aarhus University, Denmark. Led by Brian Dr. Annette T. Rosenblum F. C. Clark, the group is doing funDepartment of Public Affairs damental research into the genetic American Chemical Society 1155—16th St., N.W. expression of proteins in the cells Washington, D.C. 20036 of young and old organisms, and is working on techniques for their separation and quantification. "It is an area which we consider holds Applications consist of a letter of intent, the key to understanding senesresume, and two letters of reference. The cence, the development of aging letter of intent should include a description phenotypes, and the concomitant inof the applicant's experience in publiccrease in susceptibility to disease," oriented projects in which scientific or says Clark, a Senetek board member. technical knowledge was used as a basis for interaction and a statement that tells A number of noted scientists are why they have applied for the Fellowship associated with Senetek. Sir Hans and what they hope to accomplish as an Kornberg of Cambridge University ACS Congressional Fellow. The resume is chairman. Its scientific and techshould describe the candidates educa tion and professional experience and in nical committee includes Friedrich clude other pertinent personal informa Cramer of the Max Planck Institute tion. Letters of reference should be so for Experimental Medicine in Gotlicited from people who can discuss not tingen, West Germany; Allan Fersht only the candidate's competence but also the applicant's experience in publicof Imperial College of Science & oriented projects. Arrangements should Technology, London; Nobel Laurebe made to send the letters of reference ate Aaron Klug of the U.K. Medical directly to ACS. Research Council, Cambridge; Eiko Ohtsuka of the University of Osaka For further information call in Japan; and Morten Simonsen of (202) 872-4384. the University of Copenhagen. Dermot Ο Sullivan, London
