[Discussion transcription]

Date:
[c. 1956]
Reference:
PP/CRI/H/2/15
Catalogue details

Licence: In copyright

Credit: [Discussion transcription]. Source: Wellcome Collection.

    11/48
    v-c s the reasons that Dr® Smith already illustrated concerning the triesterified phosphate; so we proposed just making some cuts in the duplet picture pro posed in the original paper of Watson and Crick, and this would have explained those data. We looked around to see if there was anything else in this direction, and the question came up about the stability of ENA and the making of apurinic acid by heating. We did some heating experiments, and we made DNA preparations by heating 1$ minutes at pH 7.5 at 100*. It seemed unlikely to us that phosphodiester bonds were broken due to this treatment, but unlike ly is far from sure. We therefore did some experiments to detect the hydrogen ion which would have been liberated had there been a hydrolysis of the phospho diester bond, and we can't find hydrogen ions that one would expect to find if there were hydrolysis. This doesn't mean, however, that there wasn't hydroly sis. We did all our heating experiments by design in the absence of salt regardless of its effect on biological activity. The reason for this, of course, was that we wanted the effects to be manifested, and therefore we didn't have any salts. This will cause degradation to appear if it occurs. The heating experiments, I think, are very good, and I for one am in no better position than I was a year ago to say whether heating experiments can be interpreted to mean that DNA has interruptions. The next part of our own studies has been directed to find whether or not there are interruptions by enzyme kinetics. At first let's forget interruptions and deal with enzyme kinetics. Now, first of all, the enzyme kinetics tell us that there are two strands. First, to do this we had to tell DNAase how to act. We had no ob jections to doing this, but we don't know whether the DNAase follows our instructions. In any case, if we work on the assumption that DNAase breaks only a single bond at a time and acts completely at random, we are quite sure that that's right. If we treat the data in a statistical fashion and calculate directly the number of strands - because you see if you havo a one-strand structure every attack is going to be 100$ effective in causing fission - if you have a two-strand structure you need at least two attacks