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Optimize your experiments to get the best results. We’ve compiled a detailed knowledgebase of the top tips and tricks to meet your research needs.
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The Qubit® Fluorometer quantifies DNA, RNA, and protein with superior accuracy, sensitivity, and simplicity. It is designed for molecular biology labs working with precious samples that are rare or difficult to process, and applications requiring precise measurement such as real-time PCR.
The NanoDrop® instrument uses UV absorbance, which cannot distinguish between DNA, RNA, free nucleotides, and other contaminants. The Qubit® Fluorometer utilizes specifically designed fluorometric technology using Molecular Probes® dyes to quantitate biomolecules of interest. These fluorescent dyes emit signals ONLY when bound to specific target molecules, even at low concentrations.
UV absorbance readings measure anything that absorbs at 260 nm, including DNA, RNA, protein, free nucleotides, and excess salt. Quantification with the Qubit® Fluorometer only measures the molecule you are interested in, so the number is almost always lower than the A260 reading.
No. The Qubit fluorometer cannot take absorbance readings to provide a A260/A280 ratio or detect protein in nucleic acid samples. This can be done with the NanoDrop instrument. If your sample contains protein or other contaminants that can affect the assay, it should be further purified.
The Qubit DNA and RNA kits only quantify the amount of either DNA or RNA in the sample. If your sample contains both DNA and RNA, one may use either (or both) the DNA and RNA Qubit kits and compare with samples treated with either RNase or DNase to get an accurate determination of DNA or RNA, respectively.
The Qubit® 2.0 Fluorometer has a large, robust touch screen for seamless workflow navigation. It also offers automatic data logging and a USB port for efficient data management.
Yes, these kits will work with all Qubit® Fluorometers.
The Qubit® 3.0 Fluorometer can store up to 1,000 samples’ worth of data in a .csv file.
The Qubit® 2.0 Fluorometer can store up to 200 lines of data in a .csv file.
The original Qubit® (1.0) Fluorometer can store up to 20 lines of data in a .csv file.
No. But we do recommend using new standards every time you make a new working solution, so that the working solution used in your standards is the same as that used in your samples.
The diluted standards can be used for up to 3 hours if using the same working solution for the samples.
Generally, the cleaner the sample the better. Some salts, proteins, and detergents are tolerated in the assays; see the specific assay protocol for which ones and at what concentrations.
Yes, you can, for Qubit® instruments developed after the original Qubit® (1.0) Fluorometer. See MyQubit assay instructions here.
There are two light sources in the Qubit® 2.0 and 3.0 Fluorometesr - both are LEDs. They are expected to last at least 5 years.
No. The warranty will be voided if the instrument is disassembled or if you attempt to repair the instrument. It is best to call or email our technical support team for assistance.
We will replace the instrument. Please contact our Technical Support department for details by emailing techsupport@thermofisher.com.
For Qubit 4 and older instruments, use thin-walled, clear 0.5 mL PCR tubes such as Invitrogen Qubit Assay Tubes. For Qubit Flex Fluorometers, use thin-walled 200 µL polypropylene tubes such as Invitrogen Qubit Flex Assay Tube Strips. Other types of tubes can have auto-fluorescence or a frosted area for writing and may interfere with the assay.
The USB that comes with the Qubit® 2.0 Fluorometer is 2 GB, and the one that comes with the Qubit® 3.0 Fluorometer is 4 GB, but the following types are also compatible:
The following have not been verified by our R&D staff, but have been tested by customers:
DNA HS, DNA BR, DNA SS, microRNA, and Protein | RNA | |
Light sources | Blue LED, max ~460 nm | Red LED, max ~635 nm |
Excitation filters | Blue, 400–490 nm | Red, 570–645 nm |
Emission filters | Green, 510–580 nm | Red, 655–725 nm |
Kit | Assay range | Sample starting concentration |
Qubit® DNA HS Assay | 0.2–100 ng | 10 pg/µL to 100 ng/µL |
Qubit® DNA BR Assay | 2–1,000 ng | 100 pg/µL to 1 µg/µL |
Qubit® ssDNA Assay | 1–200 ng | 50 pg/µL to 200 ng/µL |
Qubit® RNA HS Assay | 5–100 ng | 250 pg/µL to 100 ng/µL |
Qubit® RNA BR Assay | 20–1,000 ng | 1 ng/µL to 1 µg/µL |
Qubit® microRNA Assay | 1–100 ng | 0.05 ng/µL to 100 ng/µL |
Qubit® Protein Assay | 0.25–5 µg | 12.5 µg/mL to 5 mg/mL |
Application | High/low limit | High/mid limit | Mid/low limit |
Qubit® DNA HS Assay | >50-fold | — | — |
Qubit® DNA BR Assay | >50-fold | — | — |
Qubit® ssDNA Assay | >30-fold | — | — |
Qubit® RNA HS Assay | >10-fold | — | — |
Qubit® RNA BR Assay | >10-fold | — | — |
Qubit® Protein Assay | — | > 1.4-fold | > 30-fold |
The Qubit® 3.0 Fluorometer employs a large, robust color touch screen for seamless workflow navigation and exports data to a USB drive or directly to your computer via a USB cable for efficient data management. Also, the instrument can be personalized to show only the frequently used assays, to add new assays, including user-defined assays created with the MyQubit assay design tool, and to display in the language of your choice including English, French, Spanish, Italian, German, simplified Chinese, and Japanese.
Yes, we expect to deplete the current inventory and discontinue the Qubit® 2.0 Fluorometer in 2015.
Yes, the Qubit®3.0 Fluorometer comes with both a USB and cable to connect to a computer.
The Quant-iT™ PicoGreen® DNA assay is the oldest assay and the most general-purpose. It requires the most user preparation and calculation, but can be adapted for cuvettes or plates. The Quant-iT™ DNA Assays are designed for high throughput (>20 samples) and for use in 96-well plate readers with no further adaptation. The Qubit® assays are intended for low throughput (<20 samples), and are only used on the Qubit® Fluorometer. The Qubit® Fluorometer contains highly optimized algorithms that calculate the concentration of your sample for you. The performance of all of these assays is similar.
Yes, we would recommend reducing the volume while keeping the dye: sample ratio constant.
Yes, short fragments may not stain well and plasmid DNA results will vary depending on conformation (see the following questions). Below is data for the PicoGreen® assay:
Effect of DNA structure on the PicoGreen® assay. The signals obtained using linear calf thymus DNA (closed stars), bacteriophage lambda DNA (closed squares), restriction-digested bacteriophage phi X174 RF DNA (open diamonds), and a commercially available set of size marker DNAs (open circles) were compared with signals obtained using supercoiled pUC19 (2,686 base pairs) DNA (open triangles) and phi X174 RF (5,836 bases) DNA (open stars).
Yes. Use the Qubit® DNA BR Assay for a typical plasmid miniprep with a high concentration of DNA (over 50 ng/μL). Use the Qubit® DNA HS Assay for plasmid rescue or methods that yield only small amounts of DNA. However, see the next question for conformation issues.
Yes. We have seen a 20–30% difference. For the different forms of plasmid DNA, we recommend using a standard that more closely represents the composition of the plasmid DNA in the sample. For information on creating custom optimized assays, please visit our website.
PicoGreen® dye and other fluorescence-based quantification reagents are not recommended for quantifying dye-conjugated nucleic acids. The attached dye molecules can interfere with either binding and/or fluorescence output of the quantification reagents.
The buffer included in the kit should assure the proper pH range, even if your DNA is at a pH outside of this range, since at least a 10-fold excess of kit buffer over sample is used in the assay.
Yes, the manual has directions for this application. You will use the 0 ng/μL lambda dsDNA HS standard to generate Standard #1. You will prepare a dilution of the 10 ng/μL lambda dsDNA HS standard to generate Standard #2. You then prepare the samples and compare them to this 2-point standard curve. The Quant-iT dsDNA BR Kit can be used in a similar manner.
There are several differences:
The linear ranges are:
Yes, the tag does not interfere with the signal.
No, they are not accurate for such small fragments. The Quant-iT™ microRNA Assay Kit and Qubit® microRNA Assay Kit are good tools for this application.
Yes, the manual has directions for this application.
No. The Qubit RNA IQ Assay does not assay the purity of the RNA sample, only the extent of degradation of the RNA (small versus large strands).
At present, we do not have a fluorescence-based assay that tests for sample purity (protein contamination). We do offer various instruments that can obtain absorbance readings (absorbance at 260/280), such as our NanoDrop, BioMate and GENESYS spectrophotometers.
No. The presence of an excess amount of free nucleotides/bases may affect the assay results in the same manner as other contaminants, but the reagents in this kit do not give a fluorescence response to nucleotides or bases.
For Research Use Only. Not for use in diagnostic procedures.