When running a gel, what could cause a standard to run "faster" than usual?

Question

We are running a gel on the products of a restriction digest to determine the size of an insert. We know the vector backbone size should be ~2.9kb; however, the standard appears to be running too quickly (or our samples too slowly), causing the backbone size to be about 4kb (which distorts our results for the insert size).What could possibly cause this? Thank you.

Answer 1

Hello,

In order to explain why the standard appears to be running too quickly, we must first examine the factors that determine the measured speed. Size and charge are the two major determinants (ie: Small bands run the fastest). If the charge is altered (ie: pH or salt content is different from the normal conditions for the standard), then run time would also change. When you apply the electrical current, the sample will be affected in accordance with ion concentrations and pH. Assuming that the buffer is at the correct pH, the most likely problem is the ion (salt) levels present.

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Sincerely,

Starlyte