Samples can be stabilized and stored in RNAprotect Tissue Reagent, included in RNeasy Protect Kits. For RNA purification, samples (0.5–30 mg tissue) are first lysed and then homogenized. Ethanol is added to the lysate to provide ideal binding conditions. The lysate is then loaded onto the RNeasy silica membrane (binding capacity up to 100 µg RNA). RNA binds, and all contaminants are efficiently washed away. Pure, concentrated RNA is eluted in 30–100 µl water (see flowchart "RNeasy Protect Mini procedure"). RNA purification can be automated on the QIAcube Connect.
Sorted or cultured cells are mixed with RNAprotect Cell Reagent, which immediately stabilizes the cellular RNA. After RNA stabilization, total RNA is purified using the RNeasy Plus Mini Kit (see flowchart " RNeasy Protect Cell procedure"). The cells in RNAprotect Cell Reagent are centrifuged, and the resulting cell pellet is lysed and homogenized in Buffer RLT Plus. The lysate is then passed through a gDNA Eliminator spin column, which rapidly and effectively removes genomic DNA. Ethanol is added to the lysate, which is then applied to an RNeasy spin column. After centrifugation, total RNA binds to the membrane of the RNeasy spin column. Contaminants are efficiently washed away, and high-quality total RNA is eluted in 30–50 µl of RNase-free water. Purification of DNA, or of RNA and DNA, requires the additional purchase of a QIAGEN DNA purification kit. Details are provided in the RNAprotect Cell Reagent Handbook.
Saliva (200 µl) collected from a donor is immediately mixed with RNAprotect Saliva Reagent to stabilize the RNA in the saliva. Total RNA is purified from stabilized saliva using the RNeasy Micro Kit (see flowchart " RNeasy Protect Saliva procedure"). The saliva sample is first centrifuged, and Buffer RLT is then added to the resulting pellet. After addition of ethanol, the sample is applied to an RNeasy MinElute spin column, where RNA binds to the membrane after centrifugation. Traces of genomic DNA are removed by DNase digestion, and contaminants are washed away in several wash steps. Highly pure RNA is then eluted using RNase-free water in a volume of just 14 µl. RNAprotect Saliva Reagent also stabilizes DNA. Protocols for purification of DNA, or RNA and DNA, from stabilized saliva are available.
Two volumes of RNAprotect Bacteria Reagent are added directly to 1 volume of bacterial culture (≤7.5 x 108 bacteria) prior to RNA isolation, providing immediate stabilization of RNA (see flowchart " RNAprotect Bacteria Reagent procedure"). The stabilization allows time for efficient bacterial lysis using a choice of protocols: enzymatic lysis, mechanical disruption, or a combination of both methods. We recommend the TissueLyser II for efficient mechanical disruption. Ethanol is then added to the lysate to provide ideal binding conditions. The lysate is loaded onto the RNeasy silica membrane (binding capacity 100 µg RNA). Following RNA binding, all contaminants are efficiently washed away. Pure, concentrated RNA is eluted in 30–100 µl of water. The RNeasy Protect Bacteria Mini Kit can be automated on the QIAcube Connect.
Amounts of RNA isolated from bacteria can vary due to species and growth conditions. The RNeasy Protect Bacteria Mini Kit is suitable for use with a wide range of bacterial species, both Gram positive (e.g., Staphylococcus aureus and Mycobacterium avium) and Gram negative (e.g., Escherichia coli and Salmonella typhimurium). Bacteria grown in either minimal or complex medium can be used. Since the RNeasy procedure enriches for RNA species >200 nucleotides, RNA yield does not include 5S rRNA, tRNAs, or other low-molecular-weight RNAs. RNeasy Protect Bacteria Kits provide the highest-quality RNA with minimum copurification of DNA. For certain RNA applications that are sensitive to very small amounts of DNA, the residual amounts of DNA remaining can be removed using the RNase-Free DNase Set for convenient on-column DNase treatment during the RNeasy procedure.