PureLink™ Fast Low-Endotoxin Midi Plasmid Purification Kit

For any silica columns, elution with water is generally possible. However, a buffer is preferred for stability and accuracy of absorbance readings, as pure water can have a very low pH (4 - 5).

Endotoxins are typically any cell-associated bacterial toxins that are part of the outer surface of the cell wall of gram-negative bacteria. Endotoxins can influence cell growth, cell differentiation, contractility, and protein expression in mammalian cells. Endotoxins are released during bacterial lysis, and they can subsequently reduce transfection efficiency and protein expression levels. Please review the following article for more information about endotoxins: Butash KA et al. (2000) Reexamination of the effect of endotoxin on cell proliferation and transfection efficiency. Biotechniques 29(3): 610-614, 616, 618-619.

The ratio of absorbance at 260 nm to the absorbance at 280 nm (A260/A280) is typically used to measure purity of the sample. For DNA, the ideal A260/A280 ratio is 1.8, but it can be in the range of 1.7 - 1.9. The A260/A230 ratio is also used to determine if contamination is present. For DNA, the ideal A260/A230 ratio is between 1.8 and 2.0. DNA purity can also be examined by gel analysis. For plasmid DNA, look for a strong, single band (perhaps with a few extra bands representing multimers of the desired molecule). For genomic DNA, look for high average fragment sizes.

We offer the following silica column-based plasmid purification kits for isolation of endotoxin-free or low-endotoxin plasmid DNA:
- PureLink Expi Endotoxin-Free Maxi Plasmid Purification Kit (Cat. No. A31217, A31231, A33073) (<0.1 EU/µg endotoxins):
https://www.thermofisher.com/order/catalog/product/A31217
- PureLink Fast Low-Endotoxin Midi (Cat. No. A35892, A36227) or Maxi (Cat. No. A36228, A35895) Plasmid Purification Kits (<1 EU/µg endotoxins):
https://www.thermofisher.com/order/catalog/product/A35892
https://www.thermofisher.com/order/catalog/product/A36228

Our recommendation is to not exceed the maximum recommended culture volumes specified in the kit manuals; using larger culture volumes means increased cell mass, which will result in reduced plasmid yield and purity.