Monday, June 7, 2010

June 7th

Today, after an overview and tour of the lab, we started out reading relevant research articles. The article I was reading was titled "DNA Inspired Electrostatics" by Gelbart, Bruinsma, Pincus and Parsegian. This article starts with a rough overview of DNA's characteristics and behaviors. It takes the form of a disordered coil in physiological conditions, but when polyvalent cations are introduced, it forms a tightly packed torus. Polyvalent counterions cause an attraction between charged DNA molecules that would repel under normal conditions. The electrostatics that govern these counterion-meditated attractions are still being refined, but there are two mechanisms being studied. One is a Gaussian fluctuation correction to the PB mean-field theory, which treats the counterion cloud around each rod as a one-dimensional ideal gas. It is longer range and more effective at high temps. The other mechanism is a short range electrostatic correlations between the counterions of the two clouds. This is more effective at lower temperatures. The dense cloud of counterions surrounding DNA also represents a large number of hidden degrees of freedom.

In the afternoon, we worked with preparing a few test solutions. We created 5 different solutions with varying concentrations of Magnesium. All five solutions had constant concentrations of 1mM Co and 5mM P. Solutions 1-5 had concentrations of 0mM, 10mM, 12mM, 15mM, 17mM, respectively. We also performed the appropriate calculations to prepare these solutions. After preparing the solutions with Micro Pipettes, we learned how to operate and calibrate the spectrometer. We aligned the spectrometer first, and then used three known solutions to calibrate it. Once it was calibrated, we put through the test solutions that we made. My concentration results were fairly consistent with the predicted values, and due to the fact that I sabotaged Travis's results, they were precise but rather inaccurate.

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