Protein concentration

Measuring protein concentration using Nanodrop

Procedure (used at Rutger's University)

concentration = Absorbance at 280 nm divided by absorbance coefficient

Typical protein peak as measured by the Nanodrop on PC

1. Before starting the software module, clean the sample surfaces with DI water to remove any dried sample that might be present.
2. Alternatively, you can clean the sample surfaces with a Kimwipe moistened with 70% ethanol.
3. Open the Nanodrop program and the appropriate module (e.g., Protein).
4. Wipe off the top and bottom sensors of the instrument with a Kimwipe. These are just the polished ends of fiber optic cable, so wiping is sufficient to prevent carryover.
5. Pipette 2 μL of DD water onto the sensor. Bring down the lever arm.
6. Follow the onscreen prompts to calibrate.
7. Wipe the sensors and pipette on 2 μL of the corresponding blank (Buffer solution your protein is in). Bring down the lever arm.
8. Follow the onscreen prompts to blank.
9. Wipe the sensors and pipette on 2 μL of your protein sample. Bring down the lever arm.
10. Click Measure and record the concentration measured.
11. For protein, the peak should be at 280 nm
12. To test multiple samples, just wipe the sensor in between measurements with a Kimwipe. Recalibration or re-blanking is not necessary.
13. Clean the sample surfaces once more after you are finished.

Procedure (University of Toronto)

Since july of 2009, we use thermofisher nanodrop1000 to measure the protein absorbance at 280 nm.

The molecular weight and theoretical extinction coefficient are calculated using expasy.