04/17/13

         Finally!! Today during my internship I was introduced/ got to use the capillary electrophoresis machine! Just because it was so long since I last wrote about the machine, I will give you a recap: In electrophoresis, proteins are separated and then characterized according to various characteristics (ie: size and charge) when moved across an applied electric field. Once completely separated, scientists are able to find abnormalities according to the types and densities of proteins in the sample. Consequently, they are then able to diagnose disease conditions. Unlike gel electrophoresis (in which the medium used for separation is a gel), capillary electrophoresis uses a liquid buffer <which now I am extremely good at preparing :) >. This gives the protein the ability to move more naturally and freely as compared to migrating through a gel. In short, capillary electrophoresis is a technique that separates ions with the use of an applied voltage.

 Today, I learned everything from how to start the machine, how and where to insert the buffers and DNA sample, how to run a test trial, and so on. Each side of the high volage supply is connected to an electrode which helps induce an electric field to initiate the movement of the sample from the anode to the cathode via the capillary tube. First, the capillary tube must be coated with the prepared buffer solution. "Electroosmotic flow is observed when an electric field is applied to a solution in a capillary that has fixed charges on its interior wall. When a buffer solution is placed inside the capillary, the charge is accumulated on the inner surface." Thus, before the sample DNA is inserted for reading, the capillary must be coated with the desired buffer.

     After the run through of the machine, using the buffer I prepared and the sample that my mentor pre-made, I got to use the machine. Putting everything together was not hard [this is one of the many advantages of capillary electrophoresis] as all I had to do was first rinse the tubes with water [cleaning it of remnants of the buffer solution from other runs] and then placing the two viles of buffer and sample in their respective places. I also made sure the temperature of the machine was what it needed to be as extreme temperatures could cause many malfunctions, ie: causing proteins to denature. Then, my mentor showed me how to take a reading of the sample via the hooked up computer. Because the explanation process concerning the workings of the machine and preparing another set of buffers took a fair amount of time, I did not get to see the produced graph (as it takes 30 minutes or more to produce 1 graph).

However, this coming Wednesday, rather than preparing the mixtures, I believe (and hope) I will get to spend more time using the capillary electrophoresis machine and learn how to interpret the resulting graph!

http://www.chem.sc.edu/faculty/morgan/lab.html