User guide

Quantity One User Guide

15-24

Note: Relative quantity expresses the quantity of each band as a percentage of

either all the bands in a lane or the total intensity of a lane (depending on

the setting in Preferences). This can tell you that there is twice as much of

Band X than Band Y; however, it does not tell you how many micrograms

there are of Band X in the gel. Absolute quantity is calculated based on

the relative quantity, standards, and a calibration curve that you create.

First the software calculates the relative quantity of each band from the area

under the intensity proﬁle peak. Using the Quantity Standards function, you

then identify standards of known quantity and use these to generate a

calibration curve. You can apply this curve to unknown bands in the current

image as well as other images.

To create a calibration curve, the absolute quantities of at least two bands

must be known. The greater the number of known bands and the wider the

range of their values, the more accurate the calibration curve will be.

Note: The quantities calculated by Gaussian ﬁtting (section 14.7) cannot be used

to in conjunction with Quantity Standards. However, you can continue to

use the original trace quantities in calculating Quantity Standards after

you have Gauss-modeled your bands.

15.3.a Creating and Applying a Set of Quantity Standards

Choose Quantity Standards from the Match menu. A pop-up box will appear,

asking you to create a new curve or load a previously deﬁned calibration

curve (if any has been saved).

Fig. 15-17. Loading a quantity calibration curve.

Selecting Create New will open the Quantity Standards dialog box.