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Protokoll
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- For one immunoprecipitation reaction resuspend cell pellet (~107 cells) in 200 μl lysis buffer by pipetting (or using a syringe)
- Place the tube on ice for 30 min with extensively pipetting every 10 min
- Spin cell lysate at 20.000x g for 5 -10 minutes at 4°C
- Transfer supernatant to a precooled tube. Adjust volume with dilution buffer to 500 μl – 1000 μl. Discard pellet. The cell lysate can be frozen at this point for long-term storage at minus 80°C. Discard pellet. For immunoblot analysis dilute 50 μl cell lysate with 50 μl 4x SDS-sample buffer (-> refer as input)
- Equilibrate GFP-Trap® beads in dilution buffer. Resuspend 20 - 30 μl Beads Slurry in 500 μl ice cold dilution buffer and spin down at 2700x g for 2 minutes at 4°C. Discard supernatant and wash binder two more times with 500 μl ice cold dilution buffer.
- Add cell lysate to equilibrated GFP-Trap®_A beads
- Incubate with gentle end-over-end mixing for 10 min – 2 h at room temperature or 4°C
- Spin tube at 2000x g for 2 minutes at 4°C
- For western blot analysis dilute 50 μl supernatant with 50 μl 4x SDS-sample buffer (-> refer as non-bound)
- Discard remaining supernatant
- Wash pellet two times with 500 μl ice cold dilution buffer (optional: increase salt concentration in the second washing step up to 500 mM)
- Resuspend GFP-Trap®_A beads in 100 μl 2x SDS-Sample buffer
- Boil resuspended beads for 10 minutes at 95°C to dissociate the immunocomplexes from the beads. The beads can be collected by centrifugation at 2700x g for 2 minutes at 4°C and SDS-PAGE is performed with the supernatant. (-> refer as bound)
- (optional) elute bound proteins by adding 50 μl 0.1 M glycine pH 2.5 (incubation time: 30 sec – 2 min) followed by neutralisation with 5 μl 1M Tris-base
Suggested Buffers (as tested in our laboratory) - Lysis-buffer (native):
10 mM Tris/Cl, pH 7.5150 mM NaCl0.5 mM EDTA0.5% NP401 mM PMSF freshly added (optional)1x mammalian Protease Inhibitor Cocktail (e.g. Serva®) freshly added(optional for nuclear proteins / chromatin proteins:DNaseI final conc. 1 μg/μl2.5 mM MgCl2) Dilution-buffer10 mM Tris/Cl, pH 7.5150 mM NaCl0.5 mM EDTA1 mM PMSF freshly added (optional)1x Protease Inhibitor Cocktail (e.g. Serva) freshly addedWash-buffer10 mM Tris/Cl pH 7.5150 - 500 mM NaCl0.5 mM EDTA1 mM PMSF freshly added (optional)1x Protease Inhibitor Cocktail (e.g. Serva®) freshly addedRIPA-Buffer (for cell lysis):10 mM Tris/Cl, pH 7.5150 mM NaCl0.1% SDS1% TX1001% Deoxycholate5 mM EDTA1 mM PMSF freshly added (optional)1x Protease Inhibitor Cocktail (e.g. Serva®) freshly addedElution-Buffer:0.2 M glycine, pH 2.5
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