Dr. Anjusha Mathew uses mass spectrometry and cryo-EM to transform our understanding of complex protein structures

To this end, Mathew combines mass spectrometry and cryogenic electron microscopy (cryo-EM). “In cryo-EM, first we freeze the MMA sample very rapidly at extremely low temperatures, so it keeps its original shape. Then the cryo-EM produces razor-sharp images using an electron beam instead of light. This gives us an incredibly detailed picture of the structure of MMAs. Cryo-EM is a powerful technique, but it also presents challenges – for example in sample preparation, data collection, and data processing. The electron beams can cause damage to the samples. And the microscope itself has limits in terms of resolution, or the sharpness of the images.”

Mathew and her team want to improve this by using image-guided native mass spectrometry (nMS) to prepare the samples before applying cryo-EM. “We guide the MMAs in their native state through vacuum in a mass spectrometer onto a surface – in this case, the cryo-EM sample grid – where they are collected for analysis. The molecules can break or deform in the process. We’re trying to give them a ‘soft landing,’ so they stay intact. This alternative approach could mitigate the reduced sample heterogeneity by leveraging the ultrahigh resolution mass separation and selection capabilities of the mass spectrometer, while maintaining the higher-order molecular structure of MMAs throughout the process, and can provide ultra-pure samples for cryo-EM. Because of this the cryo-EM can produce better and more reliable images. I received a grant through the National Technology Strategy to pursue this. I’m very excited, because it means we can now start developing a ‘soft landing unit.’ We hope to complete it within five years, and then refine it further. This will allow us to create better images of MMA structures and deepen our understanding of health and disease.”