=} }. ‘8 Aad Ayn ae CA. Fhr 3 us : 7 S STANFORD UNIVERSITY MEDICAL CENTER PALO ALTO, CALIFORNIA DEPARTMENT OF GENETICS School of Medicine s e 3 oS jo ¢ April 24, 1960 Dr. Edward Ginzzton Hansen Laboratories Stanford Unigessity Stanford Dear Eda: I wonder if you noticed a piece by Richard Feynman in the Saturday Review for April 2. This had to do with cum a proposal tm for Art to emlate Nature in storing information on a minute scale. I think we had actually discussed some speculations along the same line at our luncheon meeting. At any rate, it would be a great trick if we could use a linear information program like the sequences of purines and pyrimidines in the DNA of chromosomes as the memory for a computer, but... we haven/'t begun to think of how we could read out this information, though I think it may be feasible when the biochemistry has gone a bit further. You did ask me to alert you if I could visualize any new directions for contributions from Varian for biological research. Apart from the rather trite suggestions I made before (particle counting devices) I haven't run into anything very promising. But I suggest that you do give some thought to the possibilities of developments in the direction of microstorage of information. Since the bits have to be disctiminated from one another, some sort of ampkkikex microscope is presumably required; eventually some kind of chemical amplification (e.g. self- replication of the sequence) might come in too. I had not noticed that microscopes play any important role in information technique until now, except for the use of rather limited aptical magnigwification in, e.g., the microfilm reader. There are, I think, 3 kinds of microscope that are likely to be useful -- the standard light microscope, resolutions to about 1 micron; the electron microscope, useful resdlution to about .001 micron, and the electron-field microscope which might go to an angstrom. (The last item, by the way, might well warrant attention as an instrument that is technically rather tricky now, but might have tremendous application if suitably developed.) Once you think of using a microscope, the ways of using it become fairly obvious. For example, Ultra-violet light beams of 1 micron diameter are not tovdifficult to prodice, and even smaller particle kum beams are available. A high intensity beam can be modulated to write a message -§ ona microtape dyed with a bleachable stain, which can then be read @t by microscopy 8 at innocuous light intensities. Even erasure and reimprint can be provided for by using some reversible reactions. Micromanipulators are already available that should be able to handle specimens to the same 1 micron resolution; they could be improved by incorporating positional information on the tapes and feeding this back to the controls. As you will have calculated, a grid 1 em“ could accomodate bits(without overstraining present day technique). ((Erasing and correcting a single bit in such an array may be somewhat optimistic -- I have in mind some chemical analogues to biological photoreversal of UV effects -- and it might be easier at first to mmpx correct by recopying/ to fresh tape. )) The chief limitation to using higher resolutions may be some mechanicak problems of registration; I would have to ask kim what the relative angular resolution of a flying spot can be held to. In connection with his work on skerkemnorkexssnepy X-ray micreecopy, reading the latent images in the electron microscope, Howard Pattee may have some useful background. Yrs. cordially, Setb-— Joshua Lederberg J?’