Setting a molecular weight standard ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ One method for determining molecular weight from a scattering profile is comparison to a known scattering profile with known molecular weight. This part will teach you how to set that known standard in RAW. *Note:* The calibration dataset used for the first parts of this tutorial doesn't have the requisite data to use for this part. So we will use the data in the **calibration_data/extra** folder. A video version of this tutorial is available: .. raw:: html
The written version of the tutorial follows. #. Load the **SAXS.cfg** file in the **calibration_data/extra** folder. #. Plot all of the **lysbuf2_52_001_000x.tiff** files, where x is 0-9, on the main plot. * *Tip:* :ref:`Section 1 Part 1 ` of this tutorial document teaches you how to do this. #. Average the **lysbuf2** files you just loaded. #. Repeat steps 2-3 for the **lys2_52_001_000x.tiff** files. #. Subtract the averaged buffer profile (**lysbuf2**\ ) from the averaged sample profile (**lys2**\ ). * *Tip:* :ref:`Section 1 Part 1 ` of this tutorial document teaches you how to do this. #. Select the subtracted profile by clicking on it. In the information panel, set the concentration to 4.14 (this is concentration in mg/ml). * *Tip:* You will have to scroll down to the bottom of the Information panel to find the Concentration. |config_mwstd1_png| #. Perform a Guinier fit on the subtracted profile. * *Tip:* :ref:`Section 1 Part 2 ` of this tutorial document teaches you how to do this. #. Right click on the subtracted profile and select the “Other Operations->Use as MW Standard” option. #. Enter the molecular weight of the standard in kDa in the box that appears. For this lysozyme sample, the molecular weight is 14.3 kDa. |config_mwstd2_png| #. Click “OK” to save the molecular weight standard. #. Save the settings for future use. .. |config_mwstd1_png| image:: images/config_mwstd1.png :target: ../_images/config_mwstd1.png .. |config_mwstd2_png| image:: images/config_mwstd2.png :width: 450 px :target: ../_images/config_mwstd2.png