The QuickClean 5M Miniprep Kit is a plasmid/cosmid DNA purification kit from GenScript Corporation (Piscataway, NJ). Organized essentially identically to plasmid purification kits from other manufacturers, the protocol consists of alkaline lysis of the bacteria containing the DNA of interest, neutralization, binding the DNA to a matrix, washing away impurities, and elution. The DNA binding matrix is supplied in a spin-cartridge format and has a reported binding capacity of 20 µg per cartridge. Since plasmid purification kits such as the QuickClean Kit are available from a number of vendors, what distinguishes one kit from another comes down to performance and cost. In order to evaluate the performance of the GenScript product, I recently obtained a trial sized package of the QuickClean Miniprep Kit and used it to purify a plasmid I have been working with. As starting material, I used 1.5 ml of an overnight culture of E. coli (DH5) that had been transformed with the plasmid pTXB1 (6706 bp). The growth medium was LB containing 100 µg/ml ampicillin and the growth temperature was 37°C.
Before use, the kit requires a couple of standard manipulations: The addition of RNase to Solution I and the addition of ethanol to the wash solution. The RNase is included in the kit but the ethanol is not. Overall, the kit was very easy to use and the instructions were clear and easy to follow. I recovered 3.6 µg of plasmid from the 1.5 ml overnight culture and the 260/280 ratio was 1.87. In order to assess the quality of the isolated plasmid, I had the plasmid sequenced by our in-house sequencing facility. Using only 365 ng of DNA, approximately 770 bases were readable. The figure shows the quality of sequence obtained extending beyond 600 bases. This demonstrates that although the yield and 260/280 ratio were not the highest I’ve seen with plasmid purification kits, the quality of the purified DNA was excellent.
In addition, since pTXB1 is a medium copy number plasmid, the 3.6 µg yield from 1.5 ml culture is about right and is sufficient for close to 10 sequencing reactions.
The QuickClean 5M Miniprep Kit is available in a 250 prep-sized package only. Although it is unfortunate that GenScript doesn’t offer a smaller size given that many labs require plasmid preps only occasionally, the price almost makes up for it. The GenScript kit is about half the cost of one of the leading kit manufacturers and the performance is comparable.