QIAamp Media MDx Kit

It is strongly advised to follow the recommendations for preparing sample material provided in the corresponding Protocol Sheet to ensure reliable results.

Plasma: It is recommended to perform plasma separation immediately after blood collection when using EDTA or citrate as anticoagulant to prevent the release of genomic DNA into the plasma fraction.

Urine: Because circulating cell-free DNA in non-stabilized urine samples is rapidly degraded after sample collection due to high nuclease activity, eluates may contain no DNA or exhibit low DNA concentration. Therefore, it is recommended to stabilize urine samples. Even when using stabilized urine, it is recommended to perform a centrifugation step immediately after stabilization to prevent the release of genomic DNA from cells. Alternatively, non-stabilized urine samples can be processed immediately after collection and centrifugation using ATL-pretreatment and automated DNA extraction as described in the corresponding Protocol Sheet.

QIAGEN Proteinase K is a subtilisin-type protease, which cleaves at the carboxyl side of hydrophobic, aliphatic and aromatic amino acids. It is particularly suitable for short digestion times. It possesses a high specific activity over a wide range of temperatures and pH values with substantially increased activity at higher temperature. Soluble calcium is not essential for enzymatic activity. This means that EDTA, which is used to inhibit Mg2+-dependent enzymes such as nucleases, will not inhibit Proteinase K activity.

QIAGEN Protease is a broad-specificity Serine protease with high activity, cleaving preferentially at neutral and acidic residues. It is an economical alternative to Proteinase K for isolation of native DNA and RNA from a variety of samples.

For more information on activity of QIAGEN Protease and Proteinase K in various buffers please click here.

Small amounts of RNA and DNA may be difficult to measure spectrophotometrically. Fluorometric measurements, or quantitative RT-PCR and PCR are more sensitive and accurate methods to quantify low amounts of RNA or DNA.

Fluorometric measurements are carried out using nucleic acid binding dyes, such as RiboGreen® RNA Quantitation Reagent for RNA, and PicoGreen® DNA Quantitation Reagent for DNA (Molecular Probes, Inc.).