Purification of PCR products for downstream applications is a crucial step in molecular biology. Kits that enable the rapid removal of impurities such as primers, dNTPs and enzymes are commonly used to perform this procedure, and the PureLink™ PCR Purification Kit from Invitrogen is an example of one such product.
The PureLink™ PCR Purification Kit from Invitrogen is similar to other PCR purification kits; in that it uses silica membranes to bind the double stranded DNA while unwanted byproducts are washed away. A brief description of the procedure is as follows: a Binding Buffer is added to the completed PCR reaction to prepare the DNA for membrane binding. The sample is added to a PureLink™ Spin Column and centrifuged to bind the DNA to the silica membrane. The membrane is washed with an ethanol-containing buffer, and then centrifuged to remove excess ethanol. An Elution Buffer is added to the membrane, incubated to allow the DNA to release from the silica and then the DNA is eluted by centrifugation into a clean tube. The whole procedure takes no more than 15 minutes according to the company directions. The column can bind up to 40 µg DNA (usually from a 50 -100 µl PCR reaction). Primer removal is reported at greater than 99%, and DNA recovery greater than 80%. The kit is available in sizes of 50 reactions, 250 reactions and also in a 96-well plate format (enough for 4 x 96 well plates).
The kit has several features which are different from other PCR purification systems. To begin with, the PureLink™ Kit comes with 2 Binding Buffers. One (called the Binding Buffer) is for use with PCR products from 100 bp to 12 kb in size. The second buffer (Binding Buffer HC, or high cutoff) is to enhance the removal of short PCR products and primer dimers and is intended for use with PCR products 600 bp or greater. When using the HC buffer, products less than 300 bp do not bind, and products between 300 and 600 bp bind less efficiently. This means that the user wishing to purify a PCR product longer than 600 bp will be able to more efficiently remove unwanted products, leading to a much cleaner sample. The second feature that is different from other similar products is that only one wash step is required, making the process much faster. One negative with the PureLink™ PCR Purification Kit is that it is only for PCR products. Many similar kits will allow DNA to be extracted from gel slices with slight modifications to the protocol – effectively giving two kits for the price of one.
We have used this kit in our laboratory for several months and have found it be superior for cleaning PCR products, allowing consistent and high yield recovery of DNA from PCR reactions. The flexibility offered by the 2 buffer system is useful and effective. The PCR products have been used for applications such as sequencing, enzyme digestion and ligation with no problems. The price per reaction is reasonable when compared to other kits; however, the lack of a gel extraction function should be taken into account.
PureLink™ PCR Purification Kit From Invitrogen
A fast procedure. Includes a choice of buffers for removing short PCR products and primer dimers. Available in a 96-well format for high throughput users.
Kit is designed for PCR purification only, and cannot be used for extracting DNA from gels.
The Bottom Line
A simple kit that works well and is reasonably priced.