Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: toms@fcs260c2.ncifcrf.gov (Tom Schneider) Newsgroups: sci.nanotech Subject: Re: STM nuclear reactions Message-ID: Date: 7 Nov 90 20:17:11 GMT Sender: nanotech@athos.rutgers.edu Organization: NCI Supercomputer Facility, Frederick, MD Lines: 68 Approved: nanotech@aramis.rutgers.edu In article ems@buttermilk.princeton.edu (Ed Strong) writes: > >In article toms@fcs260c2.ncifcrf.gov (Tom Schneider) writes: >> >>The discussion about STM makes me wonder whether anyone is planning on watching >>individual atoms decay? Imagine putting down some radioactively labeled DNA >>and observing the 32P go boom! Broken DNA! Does it leave a pit in the >>surface? :-) >I'm not an expert, (obligatory disclaimer inserted here :-) but it >seems to me there are a few problems with this scenario. You generally >can't tell which individual atoms of a radioisotope are about to decay, >half-life is a statistical measure of a large number of atoms. Right. So you label up some DNA as hot as possible, or simply put some hot radioactive compound on your 'stage'. The compound chosen should be easy to recognize by STM. Then you use the STM to scan a field of the molecules. One should be able to calculate the number of radioactively labeled atoms in the field given the way they were labeled. DNA is nice because it is easy to recognize by STM (right handed helix). It shouldn't be too hard to watch 200 base pairs of DNA. Anyone have the specific activity on hand? How many of the 400 phosphates could one get hot by current body labeling techniques? The next step is to calculate how long one needs to wait for a decay. 32P has a half life of about 2 weeks, so it should be pretty easy to observe events! In 2 days 1/8 of the atoms --- 50! --- should have gone if all of them were labeled initially. Of course it will be tougher than that because not all the atoms will be hot. > Also 32P is lighter than iron so you can't fission it. Do you mean cause it to fission by bombarding it with neutrons? That would take a lot more equipment than I was thinking about... >Assuming you knew where to >look, normal radioactive decay of an individual atom is a comparatively >tame event, compared to fission of an atom. > I can't say whether it would be energetic enough to break DNA bonds. Anybody know? >------------------------------------------------------------------------------ >Ed Strong, Technical Staff Member ems@princeton.edu >Princeton University (609) 258-1747 >35 Olden Street >Department of Computer Science >Princeton, NJ 08544-2087 >------------------------------------------------------------------------------ > >[My guess is that anything ionizing could break bonds. --JoSH] Tom Schneider National Cancer Institute Laboratory of Mathematical Biology Frederick, Maryland 21702-1201 toms@ncifcrf.gov [The only problem I can see with this scheme is that to get DNA with a high percentage of any atomic type in a radioactive isotope, one may have had to cause synthesis to occur with the isotope as a constituent, and it's easy to imagine a level of radioactivity seriously impeding the synthesis. This would be obviated is it were possible to transmute the marker in place (by neutron irradiation) without destroying the DNA in the process. I don't know whether this is true. --JoSH]