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Why do I get genomic DNA contamination in my plasmid prep?
Too vigorous mixing of the bacterial lysate causes genomic DNA to appear in the eluate. The lysate must be handled gently after addition of buffers P2 and P3 to prevent shearing of chromosomal DNA. The culture volume needs to be reduced if the lysate is too viscous for gentle mixing.
Use of LyseBlue Reagent enables visualization of efficient bacterial cell resuspension as a prerequisite for complete lysis, thereby helping to avoid overloading of the columns and additional difficulties related to highly viscous lysates.
Additional information for successful plasmid preparations using QIAGEN's broad selection of Plasmid Kits can be found at our Plasmid Resource Center.
Related products
QIAprep Spin Miniprep Kit
The QIAprep Spin Miniprep Kit is designed for isolating high-purity plasmid or cosmid DNA, offering up to 20 µg yields for various molecular biology applications like sequencing and cloning. Higher yields (up to 30 µg) can be achieved using the High-Yield Supplementary Protocol. The kit is automatable on the QIAcube Connect.
Want to try the QIAprep Spin Miniprep Kit for the first time? Request a quote for a trial kit.
For optimal results, we recommend pairing this kit with the QIAvac 24 Plus system.
QIAGEN Plasmid Kits
QIAGEN Plasmid Kits provide gravity-flow, anion-exchange tips for purification of transfection-grade plasmid DNA. Lysate clearing and isopropanol precipitation are achieved by centrifugation.
The QIAGEN Plasmid Mega Kit (cat. no. 12181) and the QIAGEN Plasmid Giga Kit (cat. no. 12191) can be used with the QIAfilter Mega-Giga Cartridges (cat. no. 19781) as an optional protocol step for rapid clearing of bacterial lysates by filtration instead of centrifugation. See more information regarding principle below.
EndoFree Plasmid Kits
EndoFree Plasmid Kits provide anion-exchange-based endotoxin-free plasmid DNA purification. QIAfilter Cartridges enable fast lysate clearing by filtration. The purified DNA exceeds the purity obtained by 2 x CsCl gradient centrifugation and is suitable for advanced transfection-grade applications. The EndoFree Plasmid Buffer Set can be used for preparations of 10 mega or 5 giga transfection-grade plasmid or cosmid DNA preparations.
The Buffer ER in EndoFree Plasmid Kits has been updated to exclude Triton™ X-114, ensuring REACH compliance and even lower endotoxin levels (<0.04 EU/μg) in line with FDA vaccine standards. The improved buffer reduces incubation time from 30 minutes on ice to just 5 minutes at room temperature.*
*Please note: This update includes adjusted Buffer ER volumes and revised incubation times in the protocol.
Plasmid Buffers
Plasmid Buffers are used in plasmid DNA purification procedures. They include Buffer P1 (resuspension buffer), Buffer P2 (lysis buffer), Buffer N3 and Buffer P3 (neutralization buffers), Buffer QC (wash buffer) Buffer QBT (equilibration buffer) and Buffer QF (elution buffer).
QIAwave Plasmid Miniprep Kit
The QIAwave Plasmid Miniprep Kit is an eco-friendlier version of our standard QIAprep Spin Miniprep Kit. The QIAwave Kit uses up to 22% less plastic and up to 14% less cardboard than our standard kit and offers waste tubes made from 100% post-consumer recycled plastic that you can reuse throughout the procedure. QIAwave buffers come as concentrates, reducing the amount of plastic by up to 93% per bottle. To save paper, there are no printed protocols in the kit. You can download the protocols from the resources list or scan the QR code inside the kit box. Although the kit packaging and components of our QIAwave Kit may look different, it’s as easy to use as our standard kit, and the chemistry and performance are identical.
Please be aware that you will need sterile glass bottles to store the reconstituted buffers.
In partnership with My Green Lab, we've also assessed the environmental impact of this kit. My Green Lab ACT labels are designed to evaluate and score products on several sustainability criteria. These include:
• Manufacturing• Responsible chemical management• Sustainable content within products and packaging materials• Disposal of the packaging at the end of life
Products are scored from 1 to 10 except for energy and water consumption, which are scored as 1 point per kWh or gallon, respectively. A low score means a lower environmental impact – see figures "QIAwave Plasmid Miniprep Kit ACT environmental impact factor label US 50/250, EU 50/250 and UK 50/250 ").
The QIAwave Plasmid Miniprep Kit is designed to isolate up to 20 μg high-purity plasmid or cosmid DNA for routine molecular biology applications, including fluorescent and radioactive sequencing and cloning. You can achieve even higher yields (up to 30 μg) using the QIAprep High-Yield Supplementary Protocol. We recommend using this kit with the QIAvac 24 Plus for optimal results.