Cat. No. / ID: 201203
Taq DNA Polymerase outperformed kits tested from other suppliers and delivers robust PCR performance in a wide range of PCR conditions, without the need for time-consuming optimization (see figures " Tolerance of different primer Tm Values" and " Specific amplification of long PCR products"). Every lot of Taq DNA Polymerase is subjected to a comprehensive range of quality control tests, including a stringent PCR specificity and reproducibility assay in which low-copy targets are amplified from human genomic DNA (see figure " Lot-to-lot reproducibility"). The unique formulation of QIAGEN PCR Buffer and CoralLoad PCR Buffer, also provided with the kit, enable highly specific PCR in a variety of PCR conditions with minimal optimization requirements (see figure " Wide annealing-temperature window and Tolerance to variable magnesium concentration"). In addition, CoralLoad PCR Buffer enables immediate loading of PCR products onto an agarose gel for even easier handling and faster results. Suboptimal PCR can be improved using Q-Solution, a PCR additive, also provided with the kit (see figure " Amplification of difficult templates").
Concentration: 5 units/µl
Recombinant enzyme: Yes
Substrate analogs: dNTP, ddNTP, dUTP, biotin-11-dUTP, DIG-11-dUTP, fluorescent-dNTP/ddNTP
Extension rate: 2–4 kb/min at 72°C
Half-life: 10 min at 97°C; 60 min at 94°C
Amplification efficiency: ≥105 fold
5'–>3' exonuclease activity: Yes
Extra A addition: Yes
3'–>5' exonuclease activity: No
Contaminating nucleases: No
Contaminating RNases: No
Contaminating proteases: No
Self-priming activity: No >
Taq DNA Polymerase is a high-quality recombinant enzyme that is suitable for general and specialized PCR applications (see figures " Tolerance of different primer Tm Values" and " Specific amplification of long PCR products").
Innovative QIAGEN PCR Buffer has been developed to save time and effort by reducing the need for PCR optimization. QIAGEN PCR Buffer contains both KCl and (NH4)2SO4(see figure " Increased specificity of primer annealing"). This unique buffer facilitates the amplification of specific PCR products. During the annealing step of every PCR cycle, the buffer allows a high ratio of specific-to-nonspecific primer binding. Owing to a uniquely balanced combination of KCl and (NH4)2SO4, the PCR buffer provides stringent primer-annealing conditions over a wider range of annealing temperatures and Mg2+ concentrations than conventional PCR buffers. Optimization of PCR by varying the annealing temperature or the Mg2+ concentration is dramatically reduced and often not required (see figure " Wide annealing temperature window and Tolerance of variable magnesium concentration").
CoralLoad PCR Buffer has all the advantages of QIAGEN PCR Buffer. In addition, it can also be used to directly load the PCR reaction onto an agarose gel — separate addition of a gel loading buffer is not required. CoralLoad PCR Buffer provides the same high PCR specificity and minimal reaction optimization as the conventional QIAGEN PCR Buffer. Additionally, it contains two marker dyes — an orange dye and a red dye — that facilitate estimation of DNA migration distance and optimization of agarose gel run time (see figure " CoralLoad PCR Buffer"). The buffer ensures improved pipetting visibility and enables direct loading of PCR products onto a gel, for enhanced convenience.
Q-Solution facilitates amplification of GC-rich templates or templates with a high degree of secondary structure by modifying the melting behavior of DNA. Use of this unique reagent often enables or improves suboptimal PCR (see figure " Amplification of difficult templates"). Unlike DMSO and other PCR additives, Q-Solution is used at a defined working concentration with any primer–template system and is not toxic.
Taq DNA Polymerase is used for standard and specialized applications, including:
A fragment of the single-copy gene for cystic fibrosis was amplified from 30 ng, 3 ng, and 300 pg human genomic DNA corresponding to 104, 103, and 102 copies of target template, respectively. Three different lots of QIAGEN Taq DNA Polymerase were used and equal volumes of the PCR product were analyzed on a 1% agarose gel. M: markers.
|Applications||PCR, RT-PCR, DNA fingerprinting|
|Real-time or endpoint||Endpoint|
|Reaction type||PCR amplification|
|Single or multiplex||Single|
|With/without hotstart||Without hotstart|
|Enzyme activity||5' -> 3' exonuclease activity|
|Sample/target type||Genomic DNA and cDNA|
Touchdown PCR uses a cycling program with varying annealing temperatures. It is a useful method to increase the specificity of PCR. The annealing temperature in the initial cycle should be 5–10°C above the Tm of the primers. In subsequent cycles, the annealing temperature is decreased in steps of 1–2°C/cycle until a temperature is reached that is equal to, or 2–5°C below, the Tm of the primers. Touchdown PCR enhances the specificity of the initial primer–template duplex formation and hence the specificity of the final PCR product.
To program your thermal cycler for touchdown PCR, you should refer to the manufacturer’s instructions. For additional hints and tips for successful PCR, review the Appendix Sections in our PCR Kit handbooks, and our Brochures and Application Guides for PCR and RT-PCR.
Both the quality and quantity of nucleic acid starting template affect PCR, in particular the sensitivity and efficiency of amplification. PCR sensitivity and efficiency can be reduced by the presence of impurities in nucleic acid preparations or in biological samples. These PCR inhibitors are completely removed when template is prepared using QIAGEN Kits for nucleic acid purification. Please refer to the Brochure "Maximizing PCR and RT-PCR success" for additional information.
The optimal primer–template ratio has to be determined empirically. If too little template is used, primers may not be able to find their complementary sequences. Too much template may lead to an increase in mispriming events. Generally, no more than 1 ug of template DNA should be used per PCR reaction. As an initial guide, spectrophotometric and molar conversion values for different nucleic acid templates are listed below.
Spectrophotometric conversions for nucleic acid templates
|1 A260 unit*||Concentration (ug/ml)|
*Absorbance at 260 nm = 1
Molar conversions for nucleic acid templates
|1 kb DNA||1000 bp||1.52||9.1 x 1011|
|pUC 19 DNA||2686 bp||0.57||3.4 x 1011|
|pTZ18R DNA||2870 bp||0.54||3.2 x 1011|
|pBluescript II DNA||2961 bp||0.52||3.1 x 1011|
|Lambda DNA||48,502 bp||0.03||1.8 x 1010|
|Average mRNA||1930 nt||1.67||1.0 x 1012|
|Escherichia coli||4.7 x 106*||3.0 x 10-4||1.8 x 108**|
|Drosophila melanogaster||1.4 x 108*||1.1 x 10-5||6.6 x 105**|
|Mus musculus (mouse)||2.7 x 109*||5.7 x 10-7||3.4 x 105**|
|Homo sapiens (human)||3.3 x 109*||4.7 x 10-7||2.8 x 105**|
* Base pairs per haploid genome
** For single-copy genes
PCR products that will be cloned using the QIAGEN PCR Cloning Kit should be generated using a thermostable DNA Polymerase without proofreading activity, such as Taq DNA Polymerase. Such polymerases attach a single A overhang to their reaction products, which can hybridize to the U overhang of the pDrive Cloning Vector. For efficient addition of an A overhang during the PCR procedure, we recommend a final extension step for 10 min at 72°C as described in the standard protocols of the Taq PCR- and HotStarTaq PCR handbook.
Please see the following factors that can contribute to unspecific, smeared PCR products, and suggestions how to avoid it:
too much starting templateCheck the concentration of the starting template. Make serial dilutions of template nucleic acid from stock solutions. Perform PCR using these serial dilutions.
carry-over contaminationIf the negative-control PCR (without template DNA) shows a PCR product or a smear, exchange all reagents. Use disposable pipet tips containing hydrophobic filters to minimize cross-contamination. Set up all reaction mixtures in an area separate from that used for DNA preparation or PCR product analysis.
enzyme concentration too highWhen using HotStarTaq or Taq DNA Polymerase, use 2.5 units per 100 µl reaction.
too many PCR cyclesReduce the number of cycles in steps of 3 cycles.
Mg2+ concentration not optimalPerform PCR with different final concentrations of Mg2+ from 1.5–5.0 mM (in 0.5 mM steps) using the 25 mM MgCl2 solution provided (see table below):
|Final Mg2+ concentration in reaction (mM)||1.5||2.0||2.5||3.0||3.5||4.0||4.5||5.0|
|Required volume of 25 mM MgCl2 per reaction (ul)||0||2||4||6||8||10||12||14|
Primer concentration not optimal or primers degradedRepeat the PCR with different primer concentrations from 0.1–0.5 µM of each primer (in 0.1 µM steps). In particular, when performing highly sensitive PCR, check for possible degradation of the primers on a denaturing polyacrylamide gel.
Primer design not optimal
Review your primer design, and design new primers
For additional information on optimization of PCR results, please refer to the Appendix sections of the Taq PCR and HotStarTaq DNA Polymerase Handbook, and our comprehensive Brochure Critical Factors for Successful PCR.
Not necessarily. In a lot of cases, the uniquely formulated PCR Buffer provided in the HotStarTag Plus DNA Polymerase, HotStar HiFidelity Polymerase, Taq DNA Polymerase, HotStarTaq DNA Polymerase, and QIAGEN Multiplex PCR Kits provides optimal amplification of specific PCR products. The usefulness of Q-Solution needs to be determined empirically for each primer/template setup, by running parallel PCR reactions with and without Q-Solution under the same cycling conditions.
Q-Solution changes the melting behavior of DNA and will often improve a suboptimal PCR caused by templates that have a high degree of secondary structure or high GC-contents. For more details on the effects of Q-Solution on PCR amplification, please see the Q-Solution sections of the HotStarTag Plus DNA Polymerase, HotStar HiFidelity Polymerase, Taq DNA Polymerase, HotStarTaq DNA Polymerase, and the QIAGEN Multiplex PCR Handbooks.
Yes. Please see Table 3 in our brochure Maximizing PCR and RT-PCR success. We tested the effects of different inhibitory substances in a number of PCR systems. We also analyzed the effect of including different volumes of reverse transcription (RT) reaction mixtures in PCR. Please see the table below for a list of commonly encountered template impurities and their inhibitory effects on PCR.
Impurities showing inhibitory effects on PCR
|Sodium Acetate||≥5 mM|
|Sodium Chloride||≥25 nM|
|RT reaction mixture||≥15%|
The DNA yield obtained in a PCR reaction depends on the size of the amplicon, design of the primers, starting amount of template and primers, amplification efficiency, reaction volume, numbers of PCR cycles etc. Therefore it is really difficult to predict what yield to expect. Nevertheless, in our experience, approximately 1 µg is a good guess for most cases.
In QIAGEN labs, we have amplified PCR products up to 5 kb from complex genomic DNA, and up to 10 kb from less complex lambda phage DNA with the HotStar HiFidelity Polymerase Kit, following standard protocols in the HotStar HiFidelity PCR Handbook.
For targets larger than 5 kb of complex genomic DNA, and larger than 10 kb of less complex DNA, we recommend to follow the protocol 'Amplification of Long PCR Products' in the HotStar HiFidelity PCR Handbook. The protocol uses a mixture of HotStar HiFidelity DNA Polymerase and Taq, or HotStar Taq Plus DNA Polymerase, and allows much longer fragments to be generated. In-house we have tested fragments up to 13 kb from complex genomic DNA or up to 30 kb from less complex lambda phage DNA using this protocol.
To determine the optimal annealing temperature for a PCR assay, a Temperature Gradient experiment should be performed. To do this, you will set up several PCR reactions in duplicate for the same primer/template combination, using the same PCR chemistry, and subject each of the reactions to a slightly different annealing temperature within a specified range. If a thermal cycler with a temperature gradient function can be used, you can simply program a temperature range for adjacent wells in the cycling block. If no cycler with a gradient function exists in your lab, you will either have to perform duplicate reactions at different temperatures in different machines (if available), or back to back in the same machine.