Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!uupsi!njin!paul.rutgers.edu!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: 5 Dec 90 03:08:30 GMT Sender: nanotech@athos.rutgers.edu Organization: NCI Supercomputer Facility, Frederick, MD Lines: 54 Approved: nanotech@aramis.rutgers.edu >>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? :-) >[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] Molecular biologists label DNA this way all the time! I'm looking this up in the latest edition of "Molecular Cloning": a laboratory manual, second edition, Sambrook, Fritsch and Maniatis, Cold Spring Harbor Laboratory Press, 1989, page 10.6-10.8. Mix together: dATP dTTP dGTP dCTP (each with 32P on the alpha position, so it stays in the final product) DNA buffer (with salts and water) DNA polymerase The DNA polymerase will bind to the DNA at nicks, and run along, replicating the DNA, replacing the 'cold' bases with the 'hot' bases. They say that one can use all four radiolabeled to get things really hot: "By replacing the preexisting nucleotides with highly radioactive nucleotides, it is possible to prepare 32P-labeled DNA with a specific activity well in excess of 10^8 cpm/ug." Now, that should tell us how frequently the bases are hot, if I knew what to calculate next. Lesee.... The rule is if we divide the ug by the length in kb and multiply by 1.5 we get the number of picomoles. So we have for 1 ug 1500 pmole of bases. but there are about 10^23 molecules per mole, and a pmole is 10^-12 mole, so that's 1.5x10^11 basepairs. Each could bust up, so that's 3x10^11 base pairs. With 10^8 counts per minute, that's 3x10-4 cpm per base. If we were to watch 100 bases for an hour, we should see about 2 events. This is a rough calculation, and I haven't checked it closely (could someone confirm please?) but it looks like the experiment is practical! Tom Schneider National Cancer Institute Laboratory of Mathematical Biology Frederick, Maryland 21702-1201 toms@ncifcrf.gov Brought to you by Super Global Mega Corp .com