Reagents and Equipments TRIzol Reagent (Life Technologies cat# 15596-026) or TRI reagent (Sigma cat # T-9424) DEPC (RNase free) water or 0.5% SDS solution in DEPC treated water Chloroform (Fisher ) Isopropyl alcohol (2-Propanol) (Fisher) 75% Ethanol (in DEPC treated water) Sterile or RNase treated pipette tips, microcentrifuge tubes, and pestles or motorized homogenizer. Microcentrifuge 1.Homogenization for Cell Suspensions a.Place 1 ml aliquots of the cell suspension in sterile RNase free 1.5 ml microcentrifuge tubes. b.Centrifuge for 1 minute to pellet the cells. c.Pour off the supernatant. d.Add 1 ml of TRIzol or TRI reagent to the tubes. e.Lyse cells by repetitive pipetting. f.Centrifuge homogenate at 12000 x g for 10 minutes at 4℃. g.Transfer the homogenate in a sterile microcentrifuge tube. h.If this RNA will be used for RT-PCR, repeat steps f and g twice. Modification for tissues a.Add 1 ml of TRIzol or TRI reagent to every 50-100 mg of tissue. Sample volume should not exceed 100 μl. If you using 1.5 -2 ml microcentrifuge tube and pestle for homogenization, start with 500 μl of TRIzol or TRI reagent, then add remaining 500 μl. b.Homogenize the samples using a sterile or RNAse free plastic, glass pestles or power homogenizer and tubes. Modification for monolayers a.Lyse cells directly in a culture dish by adding 1 ml of TRIzol or TRI reagent to a 3.5 cm diameter dish. b.Pass the cells through a pipette several times. 2. Phase Separation a.Incubate samples (from 1g) for 5 minutes at room temperature. b.Add 0.2 ml of chloroform to each tube. b.Cap each tube. Shake samples vigorously by hand for 15 seconds. c.Incubate samples for 5 minutes at room temperature. d.Centrifuge samples for 15 minutes at 12,000 x g at 4oC. |
3. RNA Precipitation a.Transfer the upper aqueous phase to a fresh tube. b.Add 0.5 ml of isopropyl alcohol to precipitate RNA. If this RNA will be used for RT-PCR, first add 50 μl isopropyl alcohol, mix, incubate the samples at room temperature for 5 minutes and centrifuge at 12,000 x g for 10 minutes at 4oC. Transfer the sample in a new tube. c.Incubate for 5-10 minutes at room temperature. d.Centrifuge for 10 minutes at 12,000 x g at 4oC. The RNA will form a pellet on the side or bottom of the tube. 4. RNA Wash a.Discard the supernatant. b.Wash pellet with 1 ml 75% ethanol. c.Mix sample by vortexing. The RNA pellet may float. d.Centrifuge at 12000 x g for 5 minutes at 4oC. If this RNA will be used for RT-PCR repeat steps a,b and c twice. e.RNA pellet may be stored in ethanol at -70oC for months. 5. Redissolving the RNA a.Remove supernatant. b.Air dry the pellet for 5-10 minutes. Do not completely dry out the pellet. c.Dissolve pellet in 30 to 60 μl RNase free water or 0.5% SDS by passing the solution through a pipette tip and incubating for 10 minutes at 55-60oC. 6. Determination of RNA Concentration and Purity a.Take 2 to 5 μl RNA sample from the original stock, diluted with 998 or 995 μl RNase free water in a 1.5 ml microcentrifuge tube. This will give you 500 or 200 time dilution of the RNA sample. b.Pipet 1 ml RNAse free water in a clean cuvette and read absorbance as blank. c.Pipet the diluted RNA sample in to a clean cuvette and read absorbance at 260 nm and 280 nm. d. Use the formula below to determine RNA Concentration of the original sample: [RNA μg/μl]= A260 x 33 x dilution factor / 1000 e. To determine the purity of the RNA sample, calculate ratio of A260/A280. Ratios between 1.7 to 2 represent good RNA. Preparation of RNase-free water a.Measure water into RNase-free glass bottles. b.Add 0.01% (v/v) diethylpyrocarbonate (DEPC). c.Let stand overnight. d.Autoclave. Note: RNase free DEPC treated water is Biotecx brand (cat # BL-5611). Note: If using 0.5% SDS solution to resuspend the RNA. It must be prepared in RNase free water. |
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