20.109(S08):Characterize protein expression (Day5)
From Course Wiki
Revision as of 22:42, 18 December 2007 by AgiStachowiak (Talk)
Contents
Introduction
Protocols
You may find it helpful to prepare the solutions you will need for Part 3 (or at least the relevant calculations) before beginning Part 1.
Part 1: Lysis of cells producing mutant protein
- You will be given an aliquot of room temperature BPER (bacterial protein extraction reagent), which also contains 0.1% bovine serum albumin (BSA, a stabilizer), and a protease inhibitor cocktail to guard against protein degradation. When you are ready to begin, add 1:1000 of cold enzyme mixture (obtained from teaching staff).
- Per cell pellet, add 300 μL of enzyme-containing BPER and resuspend by pipetting until the solution is relatively homogeneous.
- Vortex for 30-60 seconds.
- Incubate the solutions (at room temperature) for 3 min.
- Finally, spin for 3 min. at maximum speed and transfer supernatants to fresh tubes.
Part 2: SDS-PAGE of protein extracts
Want PAGE of no IPTG samples for comparison - add it.
- Add 15 μL of 2X sample buffer to 15 μL of each of your lysates. Also retrieve a 15 μL sample of MW markers from the teaching faculty.
- Boil all four eppendorfs for 5 minutes in the water bath.
- You will be shown by the teaching faculty how to load your samples into the gel. Two groups will share each gel : [TABLE OF SAMPLES]
- Note the starting and stopping time of electrophoresis, which will be initiated by the teaching faculty at 200 V, and run for 30-45 minutes.
- Pry apart the plates using a spatula, and transfer your gel to a staining box. Add Coomassie Brilliant Blue, and incubate for 1 hour.
- The teaching faculty will show you how to transfer your gel to destaining buffer in the fume hood.
- Replace the staining buffer after about 1 hour.
- Tomorrow, the teaching staff will transfer each gel to water, then photograph them and post the results to the wiki. You will have a chance to physically observe your gels next time.
Part 3: Protein purification
All spins should be performed at 7000 rcf for 1 min.
Part 4: Protein Concentration
- Prepare 10 mL Bradford reagent from the 5x concentrated stock by adding water.
- Obtain BSA standards from the teaching faculty. The standards were prepared in elution buffer, since imidazole has some absorbance at 590 nm.
- Aliquot 10 μL of each standard (0.1-1 mg/mL) into labeled eppendorfs, as well as 10 μL of elution buffer alone as a control.
- Add 1 mL of Bradford reagent to each standard, as well as to your ?four? unknown protein samples. Incubate 10-20 min at room temperature.
- Measure the absorbance of each sample at 590 nm.