July 12th

Yesterday morning, I read two different articles. One was about DNA stretching, and the other was about incomplete ion dissociation. The DNA stretching article was not as relevant as I had hoped, but it was still interesting. It was about a statistical mechanical model for the condensing of DNA under tension. It was based on data similar to that which I am collecting, on the condensing of DNA in the presence of Cohex. It gave approximate values for the tension present when DNA collapses. The second article provided another theory as to why the DNA would condense and the resolubize under increasing amounts of Cohex. It suggests that as the concentration increases, not all of the Cl- leaves the Cohex, so there are increasing concentrations of Cohex+2 instead of the normal +3. This would mean that the Cohex is actually out-competing itself, causing the DNA to return to solution. It is possible that our results could be supporting this theory, although it is hard to tell without the Cl- concentration. This is unfortunately impossible to get because the solution was flooded with NaCl to resolubize the DNA. In the afternoon, the nitrogen finally got here, and I was able to resume testing. The first thing that I tested was the fourth of four initial runs that I did on the real sample.