GenElute Plasmid Prep Kit From Sigma-Aldrich

In the modern molecular world almost every biology lab today finds itself working with plasmid DNA in some capacity. One of the simplest tasks required is purifying plasmid DNA from small scale (1-5 ml) overnight cultures. Whether this is simply to produce additional plasmid DNA, to test multiple clones for presence of an insert, or for production of high purity DNA for sequencing or other downstream applications, the need exists for a fast, effective and reproducible technique for plasmid DNA isolation.

While a myriad of methods exist for performing plasmid DNA isolations, most depend on the same basic principles. Most standard plasmid preps rely on the use of an alkaline lysis based protocol. In short, bacterial cells are precipitated from liquid culture by centrifugation. The pelleted cells are re-suspended in a buffered solution. Following resuspension the cells are lysed in an alkaline buffer containing NaOH and SDS. The cellular debris is precipitated and the solution neutralized using a potassium acetate based buffer. The plasmid DNA is left in solution which is decanted from the debris pellet. It is here that manufactures have devised technologies to improve the speed, efficiency, and purity of the end product. By purifying the DNA from a standard alkaline lysis protocol via silica binding combined with spin column technology, it is possible to produce highly pure plasmid DNA in respectable quantities quite rapidly.

In our hands, the GenElute miniprep kits yield sufficient amounts of highly pure plasmid DNA. We have used this DNA directly following elution with no other treatment for multiple different enzymatic reactions. In addition, DNA from these preps has been used directly for automated sequencing. One point to consider when doing your elution is to determine whether the presence of the divalent cation chelator EDTA will interfere with downstream applications. If this is a concern, we recommend elution using the included Tris buffer rather than the standard TE commonly used.

A number of manufactures produce silica spin column based plasmid purification kits. While each touts its own proprietary buffers and manufacturing methods, in reality you pop the cells with NaOH/SDS, precipitate the cellular debris with a potassium acetate solution and bind the DNA in solution to a silica matrix. Proprietary buffers aside, in our hands, each of these kits requires approximately the same amount of time to complete a prep and yields equivalent amounts of DNA of roughly equal purity. The difference then would largely be the cost per prep. Comparison between Sigma’s GenElute kit and two other major manufacturers kits show that the Sigma kit represents a savings of approximately 25% per prep. In the short term, this represents nickels and dimes, however if you are performing large numbers of preps, the cost savings can certainly add up over time making the more cost effective kit a definite favorite over kits from other sources.