The PureLink PCR Purification kit is part of the new range of nucleic acid purification products from Invitrogen. The kit is designed to provide fast, inexpensive and highly purified products directly from the PCR reaction for downstream applications, such as sequencing and cloning. We have also used the kit to purify DNA from other procedures, such as end-fill and labeling reactions.
We have found that the Invitrogen product is similar to many of the competing cleanup kits yet the price is significantly less. The kit is available in a 50-reaction or 250-reaction kit. We have found that the cost saving is greater on the larger package sizes and this is the kit we purchase for all routine DNA cleanup procedures. The kit is also available in 96-well microtitre tray format, allowing a total of 384 purification reactions per kit.
Aside from price, we purchase the PureLink PCR Purification kit because it offers an additional feature that many kits do not provide – the selective removal of products smaller than 300bp, rather than the more conventional collection of all products larger than 100bp. By default, most kits (including this one) will collect any nucleic acid molecules that are between 100bp and approximately 10-15kb. We have found that this can cause problems when long primers, short failed PCR products, primer dimers and other molecules are present in the reaction as these can be carried forward to interfere with downstream applications. The PureLink kit provides two separate binding buffers that allow the user to change the binding properties of the affinity matrix to collect either 100bp-12kb, or 300bp to 12kb. We now use the high cut-off buffer to reduce our need for gel extraction and purification, decreasing the time required to complete many procedures. However, we have also noted that this procedure often decreases the yield of products up to approximately 600bp.
The kit utilizes the standard immobilized silica column format to bind the nucleic acids in conjunction with a chaotropic salt to dissolve any enzymes and other proteins. A wash buffer is applied to remove salts and the DNA is eluted using water or Tris buffer. This is the same system used by nearly all competing products so the results from this kit are similar to that of others. We routinely obtain high yield and purity products (A260:A280 of approximately 1.8-2) using this kit and they perform identically in side-by-side testing with the products from several other major competitors. At 40ug per column, the binding capacity is excellent. Many competing products have a binding capacity of 20ug or less. The recovery rate is greater than 80%, which is similar to that of other kits.
According to Invitrogen, these kits are designed to be stored at room temperature for 6 months, which is lower than that of many competitors’ products who claim a shelf life 12 months and beyond. We use these kits at a sufficient rate that we have not been able to evaluate their shelf life beyond that recommended by the Invitrogen. We have never experienced a problem in storing these kits within their recommended shelf life.
Scott Coutts
Bacterial Pathogenesis Research Group
Monash University
Australia