Another application of strip densitometry is measurement of band densities on Western blots or protein/DNA gels. The image below is a polyacrylamide gel stained with Coomassie blue. Instead of measuring each lane as a separate strip, it is often faster to make the strip horizontal, so that the protein band of interest shows up as a series of rectangular peaks. This method is also very accurate.
In order to measure the amount of protein in this gel, click on ``Strip Densitometry'' and select two endpoints (shown with 'x') on either side of the gel, perpendicular to the migration direction as shown. The result is a simultaneous measurement of multiple bands.
In this graph, each of the five peaks represents the cross-sectional area of the corresponding band in the gel. After subtracting the background (manually using ``Manl.Baseline'' or automatically using ``Auto Baseline''), the area of each spot can be measured by dragging on the peak using the mouse. The measured band intensities are automatically placed in a list box which can be saved into a text file.