Wednesday, June 9, 2010

June 8th

Today in the morning, I read through an article titled "DNA Aggregation Induced by Polyamines and Cobalthexamine". This article discussed how spermidine, spermine, and cobalthexamine could cause DNA molecules to precipitate out of solution. Then, further addition of these cations can also cause the DNA to become soluble again. The concentrations required to make the DNA precipitate are basically independent of how much DNA is in the solution. This precipitation is not caused by a classical "salting out" situation, where high salt concentrations change the activity of the water. One explanation for the precipitation and then resolubilization is that it is caused by short-range electrostatic attractions. Another explanation is that the DNA undergoes a charge reversal, but this explanation is less likely.

The rest of my day was spent preparing three different series of test solutions to test the calibration of the spectrometer. The reason for these test solutions is to find the optimal reading conditions for a later test of a specific sample that has a similar make up. I made a Mg series that was varied over 7 concentrations, a Co series over 4 concentrations, and a P series over 3 concentrations. These will be used to see how accurately the machine can read my "standardized" samples, but also I guess it will measure how well I can make solutions. At the end of the day, I was just finishing the tests, and did get to finish looking at the results. What I did see did seem to have a systematic difference of around 5%.

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