Empower Tip #271 | Empower CDS User Question

By March 30, 2022


Tip #271: How to calculate isoelectric point or pI, when separating proteins by charge profile in Empower

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Welcome back! In this week’s tip for Empower Chromatography Data System (CDS), we will answer an Empower CDS user question. In last week’s tip, we explored the difference between Amount and Concentration. Tip #270.

Q: How can I get Empower to calculate isoelectric point (pI) when using the Maurice to do capillary isoelectric focusing (cIEF) to separate proteins by charge?

Great question. This scenario involves using two pI markers and Custom Fields to calculate pI for the peaks in between the markers. Please remember to validate all Custom Fields before using them to generate final reportable results.

Let’s get started.

Step 1

The information for the markers is entered in the ‘Instrument Method Editor’ under the ‘Markers’ section (figure 1).

Empower Chromatography Data System

figure 1

Step 2

Enter the values for the makers in the ‘Component Editor’ on the ‘Value’ tab (figure 2).

Empower Chromatography Data System

figure 2


Custom Fields

Step 3

The properties of the Custom Field PI_Calc and the full equation can be seen in figures 3 and 4.

Empower Chromatography Data System

figure 3

 

Empower Chromatography Data System

figure 4

Step 4

The properties of the Custom Field PI_Slope can be seen in figure 5.

Empower Chromatography Data System

figure 5

Step 5

The properties of the Custom Field PI_Unknown can be seen in figure 6.

Empower Chromatography Data System

figure 6

Step 6

The properties of the Custom Field PI_Y_Intercept can be seen in figure 7.

Empower Chromatography Data System

figure 7

Step 7

The properties of the Custom Field PI_Value can be seen in figure 8.

Empower Chromatography Data System

figure 8 

Processing Method and Results

Step 8

Enter the names of the markers in the Processing Method on the ‘Components’ tab. These names must match the ones in the Custom Fields. If you decide to create an LC Processing Method and use Retention Time rather than a CE Processing Method with Migration Time, you will need to adjust the Custom Fields accordingly (figure 9).

Empower Chromatography Data System

figure 9

 

Step 9

The calculated result with all fields populated can be seen in figure 10.

Empower Chromatography Data System

figure 10

 

It’s that easy!

Final Note: This can be done with either the Pro or QuickStart interface.

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Next time in Empower Tip #272– we answer another Empower user question. Don’t miss this tip! Subscribe to receive Empower Tips in your inbox every week. Subscribe now

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