An Attractive Genomic DNA Isolation Kit
I was becoming a bit bored with the tedium of column-based kits, so when I had to isolate genomic DNA from a range of micro-organisms for a recent project I decided to try something new.
Invitrogen’s ChargeSwitch genomic DNA isolation kit, which uses magnetic beads to separate the gDNA from the cell debris, seemed interesting so I thought I’d give it a go.
The initial outlay for the kit is higher than most since a specialized rack with integrated magnets is required. The racks cost upwards of 100 GBP depending on the size. Since I only needed the mini-prep rack, my boss wasn’t too upset at the price.
The kit uses a unique magnetic bead material that is positively charged, so forms an ionic bond with the negatively charged DNA backbone, at low pH but loses this charge and DNA binding ability at higher pH (see diagram above). After a standard lysis procedure, the genomic DNA can be isolated in a 15 minute procedure that involves binding the genomic DNA to the magnetic beads in a low pH buffer, immobilizing the beads with a magnet, washing and finally eluting in a higher pH buffer (click the thumbnail image on the left for a visual description).
Although the protocol advises that centrifugation is not required after the initial pelleting of the cells, I found that centrifugation after the lysis step (e.g. 14,000 rpm, 10 min) was required to prevent contamination of the final eluate with cell debris.
That said, I was delighted that yields and purities of the genomic DNA samples I obtained from this kit were easily better than I normally obtain with column-based kits, so I would definitely recommend giving this kit a go.
Invitrogen have kits for plasmid DNA and RNA isolation that use the same ChargeSwitch technology, so I think I will be giving these a go and getting rid of at least some of my column-based kits!
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Nick Oswald
Nick is a molecular biologist who grazes in the field of biocatalysis by day and cooks up Bitesize Bio by night.
July 5th, 2008 at 3:51 pm
Wow very cool