Optimizing Gel Electrophoresis: Ampere, Volts and Buffer concentrations

Question

I am a master student in biochemistry, and I have used gel electrophoresis many times before. What I want to know is how one should adjust the mA (mAmpere) compared to the voltage and the buffer one uses.

Normally I used 1xTAE buffer (run at 90V) or 1x sodium borate buffer (run at 110V). I know that if I adjust the voltage up, the buffer heats up faster, the samples travel faster, but the "picture" of the gel becomes more blurry. This is however all I know about adjust the parameter.

So my questions can be summarized as the following:

1. How should I adjust the ampere, is there a range I should be in compared to the buffer or sample I am running?

2. Does the ampere effect the travel speed if adjusted up or down?

3. Can I adjust the concentration of the buffer to run sample at a higher voltage, what effects will this have (to increase or decrease concentration)?

4. Is there a relationship between the ampere and the voltage which I can manipulate, in this case: how and why?

Answer 1

1. As far as I know you can either adjust the ampere or the voltage as both is dependent of the resistance from the buffer. Which means that I would suggest you to let the voltage as it is.

2. As the ampere = voltage / resistance and voltage = resistance * ampere and as you can see that the voltage has to get higher if the ampere is increased and the ampere has to get higher if the voltage is increased (at least if I understand it correctly) the travel speed should be increased the higher the ampere is set.

3. I would neither decrease nor increase the concentration of the buffer. Maybe easily using another kind of buffer would help you. But this depends on the different samples you are running. Maybe that could help you: Brody, J.R., and Kern, S.E. (2004). History and principles of conductive media for standard DNA electrophoresis. Analytical Biochemistry 333, 1–13.

4. The resistance is more or less given. Therefore as far as I know: No.