JoVE Science Education Database. Basic Methods in Cellular and Molecular Biology. Gel Purification. Journal of Visualized Experiments, Cambridge, MA, doi: 10.3791/5063 (2014).

Overview
Gel-purification is a standard procedure performed to recover desired DNA fragments from agarose gels after electrophoretic separation. After dissolving the gel fragment and running it through a specialized filter, this procedure yields DNA freed from impurities such as salts, free nucleotides and enzymes, suitable for downstream applications.

Summary
Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, washing and eluting from a silica column. DNA is believed to bind to silica in the presence of high salt via a salt bridge. Following binding, DNA is washed of impurities and eluted under low salt conditions disrupting this interaction.

This video goes through a step-by-step, generalized procedure for cutting out a band from the gel, gel solubilization, purification through binding to a silica column, and elution of purified DNA. In addition, the presentation discusses several tips for ensuring successful gel purification, including the importance of running an agarose gel with a marker or ladder that has DNA of known sizes.

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