Assistant Professor
Department of Biological Sciences
University of Naples Federico II
A fast method for isolating DNA from both agarose gels and solutions is the wish of researchers who have to carry out downstream applications that need highly pure DNA samples (e.g. for cloning and/or sequencing). The UltraClean® GelSpin® DNA Purification Kit allows the recovery of small DNA fragments from 0.2 mg agarose slices. DNA of 100 bp-50kb can be recovered. We have mostly used the kit for gel purification of 200-500 bp DNA fragments, with very good results. The maximum spin filter binding capacity declared is 20 ug. The product specifications predict 80-100% recovery, depending upon the application. The datasheet included is informative, since every step is described in detail, and a little troubleshooting guide suggests how to recover DNA from agarose slices that are bigger than 0.2 mg. In our experience, however, isolating from large gel slices results in yields that are much lower than the standard protocol.
The technology used is the same that other commercially available kits use: the well known silica-based binding of DNA in chaotropic salt solution. After cutting out the gel slice and placing it in the column, the DNA-containing gel slice is melted in a NaClO4 solution (and does not re-solidify). Then the column is washed in Tris/ethanol solution and finally, the DNA is eluted by using 50 ul of Tris buffer pH 8.0. The whole protocol is carried out within 20 minutes, including 4 very quick centrifuges steps.
For recovery of DNA from solution, the easy protocol efficiently removes dNTPs, ethidium bromide and enzymes. In this case, obviously, there is no need to break the gel structure but, nonetheless, the GelBind® solution is added to the reaction to be purified in order to create the high salt conditions required for binding DNA to the column; then the solution is added to the spin filter, centrifuged, and then the Tris/ethanol and Tris solutions are used to wash and elute DNA, respectively.
The UltraClean GelSpin DNA Purification Kit is a versatile and inexpensive tool to effectively isolate DNA from agarose gels, reactions or solutions.