QIAquick PCR Purification Kit for PCR Cleanup

CoralLoad dyes supplied in PCR Kits such as, e.g., Taq, HotStarTaq, and TopTaq DNA Polymerase and TopTaq Master Mix do not interfere with most downstream enzymatic applications.

However, for reproducible results, purification of PCR products using the QIAquick or MinElute PCR Purification Kits prior to enzymatic manipulation is recommended.

• Add 1/10 volume of 3 M Na-Acetate pH 5.2, and 2 to 2.5 volumes of ice-cold 100% ethanol to the DNA sample
• Mix, and store at –20°C for at least 1 h to precipitate the DNA
• Recover the precipitated DNA by centrifugation at full speed in a microcentrifuge for 15–20 min
• Pour off the ethanol and wash the pellet twice with room-temperature 70% ethanol
• Allow the DNA pellet to air-dry
• resuspend the DNA in a suitable volume of sterile TE buffer or distilled water

Based on our experience, the QIAquick PCR Purification Kit removes SYBR Green dye efficiently from PCR reactions.

We strongly assume that the QIAquick Gel Extraction Kit will be equally efficient in removing this dye, however, we recommend a 5 min incubation with wash Buffer PE on the QIAquick spin column at step 10 of the QIAquick Gel Extraction Kit Protocol. Efficiency of SYBR Green dye removal has to be validated by the enduser.

Yes. The QIAquick PCR Purification Kit has been used to clean up fragments between 100 bp and 10 kb from a wide range of enzymatic reactions, removing salts, buffers, enzymes, nucleotides, and primers smaller than 40 nucleotides. Reactions that can be cleaned up with the QIAquick PCR Purification Kit include restriction digests, random priming, ligase, kinase, phosphatase, nuclease, nick translation, and cDNA synthesis reactions.
For data and additional information, please see QIAGEN News article Issue No. 5, 1998 "Fast and efficient enzyme removal with QIAquick Spin kits."

DNA fragments purified with the QIAGEN DNA Cleanup Systems, i.e., the QIAquick PCR Purification Kit, the MinElute Reaction Cleanup Kit, the QIAEX II Gel Extraction Kit etc. may float out of the loading wells of agarose gels due to residual ethanol carried over from the wash step with Buffer PE (despite the addtition of glycerol-containing loading buffer).

Use either of the following options to remove residual ethanol from the eluate:

• re-purify the sample using a QIAquick-, or MinElute column, or QIAEX II resin
• incubate the eluate at 56°C for 10 min to evaporate the ethanol
• dry down the sample in a vacuum centrifuge, and resuspend the pellet in a small volume of sterile water

As a rule of thumb, single-stranded DNA binds to silica with approximately half the affinity of a double-stranded DNA fragment of the same length under the buffer conditions used in the QIAquick and MinElute Kits. Even though no systematic experimental data exists, we expect that recovery of ssDNA fragments of approximately 200 nucleotides and below will not be very efficient after cleanup using the QIAquick PCR Purification Kit or MinElute PCR Purification Kit. By comparison, it should be possible to purify fragments longer than 140 nucleotides using the QIAquick Gel Extraction Kit.

Note that recovery of single strand DNA is influenced to some degree also by factors such as base composition and secondary structure. It has to be determined empirically by the researcher if cleanup of single-stranded DNA with QIAquick columns yields satisfactory results.

The composition of Buffer EB is:

• 10 mM Tris-Cl, pH 8.5

Buffer EB is the elution buffer used in the QIAquick PCR, Gel Extraction, Nucleotide Removal Kits, and MinElute Kits for DNA cleanup, and the QIAprep Miniprep Kits for small-scale plasmid purification. The purified DNA can also be eluted in TE (10 mM Tris-Cl, 1 mM EDTA, pH 8.0), but the EDTA may inhibit subsequent enzymatic reactions.

Occasionally, DNA fragments eluted from the silica matrix of QIAquick, MinElute or QIAEX II Kits will contain denatured single-stranded DNA (ssDNA), appearing as a smaller band on an analytical gel. Under certain conditions, chaotropic agents (present in all silica-based DNA purification methods) can denature DNA fragments. This is a rare event that may be influenced by sequence characteristics such as the presence of inverted repeats or A–T-rich stretches.

Because salt and buffering agents promote renaturation of DNA strands, the following tips are recommended:

• use the eluted DNA to prepare your downstream enzymatic reaction, but omit the enzyme. Incubate the reaction mix at 95°C for 2 minutes to reanneal the ssDNA, and allow the tube to cool slowly to room temperature before adding the enzyme and proceeding
• alternatively, the DNA can be eluted from the silica-gel membrane or resin in 10 mM Tris buffer containing 10 mM NaCl. However, the salt concentration of the eluate must then be taken into consideration in downstream applications.

The QIAquick Spin Columns (100) (cat. no. 28115) in the QIAquick PCR Purification, Gel Extraction, Nucleotide Removal and PCR & Gel Cleanup kits are also sold separately from the kits.

The MinElute columns in the MinElute PCR Purification, Gel Extraction and Reaction Cleanup kits are not sold separately.

We always provide extra buffers in our kits so you can scale up reactions, add extra washes or allow for spillage.