Must-Read for MicroCal DSC Users! FAQ About DSC System

by Malvern Panalytical, Monday, 25th February 2019

Verna Frasca, the application manager for MicroCal products, addresses frequently asked questions about the new PEAQ-DSC product. There is also useful information for those using the VP-Capillary DSC. Please have a read.

Read this article in English here

[Q1: What is the required amount of sample?]

The PEAQ-DSC Automated requires a minimum of 325 μL, including dead volume. In practice, 300 μL will be filled into the cell. Please ensure the solution is set accurately into a 96-well plate.

The 96-well plate can be filled up to 400 μL. Enter the actual amount of solution set in the “Load Settings” under “Well Plate Volume (μL).” (Figure 1.) The PEAQ-DSC Automated accounts for dilution caused by the autosampler in the software. The dilution factor is reflected in the concentration information entered during analysis.

Figure 1.

In the manual PEAQ-DSC, fill 250 μL using the supplied micropipette. It is recommended to prepare between 270-280 μL to be safe. Dilution does not need to be considered in the manual system.

[Q2: How many “Warm up” scans should be performed to stabilize the thermal history?]

It is important in DSC to stabilize the thermal history by repeating heating/cooling cycles before actually measuring the sample from a standby state. Whether manual or automated, if the PEAQ-DSC system is clean, performing water-water or buffer-buffer scans at least 2-3 times before measuring the sample is sufficient for a warm-up.

Note that in the PEAQ-DSC Automated, if the Sample Type is set to Buffer, you can check “Assessment Setting” to automatically perform a warm-up of up to 5 scans until completion.

[Q3: What is “Number of Purge Refills” (Figure 2.) in the PEAQ-DSC Automated, and how should it be set?]

The “Number of Purge Refills” is the setting for how many times the solution in the well is drawn and expelled with a syringe before filling the solution from the 96-well plate into the cell. In the autosampler, if the solution containing high concentrations of salt, etc., is set on the plate before measurement, a concentration gradient could occur. Therefore, if you only perform one round of drawing/exchange, concentration bias may occur, affecting the thermal capacity of the solution and data reproducibility, so it is recommended to repeat the purge/refills at least three times. If more than 325 μL of solution is set on the well, or if the solution is highly viscous, repeating the purge/refills five times is recommended.

Figure 2.

For VP-Capillary DSC users, the “Number of Filling Strokes” under the “Advanced” tab serves the same function. Like the PEAQ-DSC Automated, it is recommended to use settings of 3-5 times.

[Q4: What are the differences between the Clean settings, and which one should be used?]

Keeping the DSC cell clean is important for obtaining high-quality data. The PEAQ-DSC Automated has three cleaning options. The recommended detergents are 14% Decon90 or 20% Contrad70, which should be set in Reservoir 1.

The selected cleaning option will be executed after the scan ends and before the next sample is filled. (Note: In VP-Capillary DSC, cleaning is performed before scan starts and after the previous sample measurement ends.)

Rinse: The cell is washed with water after the scan ends. Rinse is recommended when measuring water-water or buffer-buffer.
Wash: The cell is washed with detergent followed by water after the scan ends. Wash is recommended to be performed after each sample scan.
Scan: Detergent is placed in the cell after the scan ends, followed by heating according to the next scheduled scan, and then washed with water. To avoid damage to the cell, set Tend to 80°C. Scan is recommended to keep the cell clean after the last sample measurement ends or when the sample is viscous. Note that Scan data is saved as “DETERGENTSCAN.dscx” but is not used for analysis and is not included in the DMES file.

When Wash or Scan is selected, the default water washing is set to 5 mL, but this can be increased. Using 14% Decon90 (or 20% Contrad70) with PEAQ-DSC Automated has been verified to be sufficient with 5 mL of water wash. However, depending on sample conditions or if using other detergents, users may need to determine the necessary amount of water, so please be aware.

Additionally, pay close attention to the cell’s condition at the start of measurement with the PEAQ-DSC Automated. When the system starts, it will first empty the cell and load the solution from the 96-well plate without cleaning the cell. Therefore, if it hasn’t been used for a long period or if the cleanliness of the cell is unknown, select and execute an appropriate cleaning method from the “Maintenance” screen. PEAQ-DSC Automated is designed to alert you if cleaning hasn’t been executed for a while. (Figure 3)

Figure 3.

VP-Capillary DSC can also configure cell cleaning from the “Maintenance” tab. (Figure 4)

Figure 4.

For manual PEAQ-DSC, it is recommended to follow the movie included in the software and perform cleaning with 14% Decon90 (or 20% Contrad70).

[Q5: What is the Reference Material used for PEAQ-DSC delivery and OQ (Operational Qualification), and can this material be used as a verification sample?]

The MicroCal PEAQ-DSC Reference Material is an oligonucleotide, available for purchase (Product name: Reference Material Kit, Catalog number: MCL2015). It can also be used on VP-Capillary DSC. This kit includes reagents sufficient for performing the recommended method twice.

[Q6: “Filtering Period” needed adjusting in VP-Capillary DSC. Why isn’t this present in PEAQ-DSC?]

In the PEAQ-DSC, the Filtering Period is automatically set based on the Scan Rate. As the Scan Rate increases, the Filtering Period decreases (to a few seconds). The thermogram adjusts to ensure the same number of data points at any Scan Rate.

[Q7: How can I save frequently used Load/Scan settings when constructing methods in PEAQ-DSC?]

Select the Load settings you wish to save, click the Save button, name it appropriately, and save. Saved settings will appear in gray under the default “Load” and “Scan”.

Figure 5.

[Q8: I accidentally entered the wrong sample concentration, how can I change it?]

Open the data in the “Analysis” screen and proceed to the “Fit” screen. Enter the correct concentration under “Concentration (M)” below the thermogram. Note that dilution done by the autosampler is not automatically factored in, so it needs to be calculated beforehand. Since dilution ratio changes depending on the set sample amount, be careful. When recalculating concentration, account for the 22 μL of buffer remaining in the syringe. For example, if you set 325 μL of a 10 μM sample in the well, calculate 10e-6*325/(325+22)=9.37e-6 and enter that in the Concentration (M).

If you want to change multiple data records to the same concentration at once, select and highlight them in the “Records” list and enter the concentration information in “Concentration (M).” If the data is pre-model fitting, click “Restore” to confirm. If you fit with Two-state or Non-Two-State, click “Fit” to confirm.

Figure 6.

When you change concentration, an asterisk (*) is added next to the sample name in “Records” and in “[Cell] (M)” in “Record Information.” (Figure 7)

Figure 7.

It is recommended to save the modified file under a different name.

[Q9: How can I export DSC data?]

In PEAQ-DSC, you can save as images or in CSV format. Go to the “Reports” screen and select the desired Report format. Select the data to export from the “Records” list (multiple selections possible). Click the Export Menu icon in the upper right of the screen displaying the desired data, and “Export Data” or “Export Image” will appear. (Figure 8) “Export Data” saves data in CSV format. “Export Image” saves the plot in your preferred format.

Figure 8.

[Q10: Where can I obtain the latest software and user manuals?]

The current latest software version for PEAQ-DSC is 1.30. It can be obtained from the following site (as of February 26, 2019).

For software update information, be sure to click “Software Update Notification” and check the ‘SOFTWARE UPDATE NOTIFICATION [SUN]’.

Contact us for inquiries and sample measurement requests about MicroCal PEAQ-DSC here
Learn more about MicroCal PEAQ-DSC here
Learn about the principles, usage, and tips for calorimeters here

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