Photocrystallography with LEDs - MX1

Thorlabs mounted LEDs are now available for use on the MX1 beamline through the new LED tab on the Shutter Flux GUI. If you require them on MX2, they must be run manually by beamline staff.

Considerations

• Crystals should be of good quality and UV-Vis absorption studies should have been done to know the appropriate wavelength of light to use.

• Photosensitive crystals must be mounted with as little exposure to ambient light as possible (depending on the sensitivity, the microscope light can be filtered to allow for mounting), however generally once at 100K they should be stable.

• Collect an initial dataset before starting irradiation studies.

•  Most samples will not react under light irradiation at 100K. The crystals should be warmed (target temperature will be sample dependant), then irradiated. The X-ray diffraction may either be collected at the warm temperature or the crystal may be cooled again before data collection.

Safety

High powered LEDs can cause eye and skin damage. MX staff will set up the hardware so that the LEDs are only powered when the experimental hutch is searched and secured. Fill in the “LEDs in use” form before starting your experiment and stick it to the hutch door, including wavelength, risk group, type of laser glasses needed and contact details of a responsible user on site.

Manual data collection

1. Centre and screen your crystal as usual.

2. Set the desired cryo temperature and collect an initial dataset once at temperature.

3. Select the required driver current from the table of LEDs

4. Set the power level then select the “LED on” button.

5. Irradiate for your desired length of time, then collect another dataset.

6. Repeat step 5 as many times as required.

7. Turn off the LED with the “LED off” button.

8. Return the cryo to 100K

Automated data collection

1. Centre and screen the crystal as usual.

 

 

 

2. Change the cryo set-point to the required temperature in the “Cryojet Temperature” tab

 

3. Input your LED wavelength (this will select the correct driver current) and desired power level (0-100%). Input your total experiment time and collection interval in minutes. For example, 60 min total experiment time with an interval of 6 min will result in data collections every 6 min for an hour.

 

4. Select “collect”. This will turn on the LED and trigger data collections. The crystal will rotate between 0-180 degrees in between data collections. Follow progress of the experiment in the pop-up terminal. If you want to stop the experiment, input Ctrl C in the terminal. At the end of the data collection the LED will turn off and a file called filename_ASphoto.cif will be written to your /auto/dataset/ folder. Make sure you give different file prefixes to subsequent experiments, or this file will be overwritten.

 

5. Return the cryo to 100K.

 

6. Make sure you copy filename_ASphoto.cif when you get your data to include in your published cif. This file will include the collection parameters including wavelength, light source, power, irradiation time and interval.

Open

 

Available LEDs