Here are some suggestions for your experiments:
- Many enzymes, including restriction endonucleases and ligases, are inhibited by small amounts of agarose and by perchlorate contaminants. This is not normally a problem. If it is, however, you can use the DNA without repurification by increasing the amount of enzyme used in the digest or ligation or by increasing the digestion incubation time. Also, you may use less DNA in your digest or ligation with the same total volume and the same amount of restriction enzyme.
- There may have been residual ethanol in the eluted fragment. Be sure to thoroughly centrifuge to remove the wash buffer, discard the wash buffer, and use a fresh tube to collect the eluted DNA. For applications that are very sensitive to ethanol, let the open spin column stand for 15 minutes at room temperature to let any excess ethanol evaporate.
- The washing steps may not be as efficient as they should be. Under these circumstances, there may be trace amounts of perchlorate in the eluate. To avoid this, extend the centrifugation times to 5 minutes and wash 2 times with wash buffer.
- Be sure to perform the optional wash step if you are using higher concentrations of agarose or are adding more than 250 mg to the cartridge. If applications are sensitive to EDTA, elute with water (pH 7.5-8.5), or with 10 mM Tris, pH 8.0 without EDTA.