A new technique, partially influenced by the James Webb Space Telescope (JWST) design, uses mirror segments to sort and gather light on a microscopic scale and to take three-dimensional images of molecules in position and orientation.
On December 5th, 2022, the journal Nature Photonics published details of this new system, which was created by Oumeng Zhang, a recent Ph.D. graduate from the lab of Matthew Lew, associate professor of electrical and systems engineering at the McKelvey School of Engineering at Washington University in St. Louis.
The radially and azimuthally polarized multi-view reflector (raMVR) microscope relies on capturing as much light as possible, just like the space telescope. However, it uses that light to distinguish between various characteristics of tiny, fluorescent molecules attached to proteins and cell membranes instead of using it to see distant objects.
The setup is partially inspired by telescopes. It is a very similar setup. Instead of the familiar honeycomb shape of the JWST, we use pyramid-shaped mirrors.
Oumeng Zhang, Ph.D. Student, McKelvey School of Engineering, Washington University in St. Louis
At the moment, making biological images with microscopes in this field is difficult. One reason is that the fluorescent molecules emit such minute amounts of light that they are sensitive to even the smallest aberrations, such as the murky conditions inside a cell.
This makes precise imaging more dependent on computer processing to determine orientation after an image has been captured.
Think of creating a color picture when all you have are gray-scale camera sensors. You could try to recreate the color using a computational tool, or you can directly measure it using a color sensor, which uses various absorbing color filters on top of different pixels to detect colors.
Matthew Lew, Associate Professor, Electrical and Systems Engineering, McKelvey School of Engineering, Washington University in St. Louis
Similarly, molecular orientation cannot be seen by regular microscopes. The eight channels of the raMVR microscope, each representing a different aspect of the molecule’s position and orientation, are divided by polarization optics, known as waveplates, and the microscope’s pyramid-shaped mirrors.
Notably, the raMVR microscope is not just a small technology; however, smaller is not always superior.
Lew added, “At the cutting edge of engineering physics, we often have to make tradeoffs to make our instruments compact. Here, we decided to take a different tack: How could we use every precious bit of light to make the most precise measurement possible? It is absolutely fun to think differently about the architecture of a microscope, and here, we think the newfound 6D imaging performance will enable new scientific discoveries in the near future.”
This study was funded by the National Institutes of Health’s National Institute of Allergy and Infectious Diseases (R21AI163985), National Science Foundation (ECCS-1653777), and National Institute of General Medical Sciences (R35GM124858).
Video Credit: Washington University in St. Louis
Zhang, O., et al. (2022) Six-dimensional single-molecule imaging with isotropic resolution using a multi-view reflector microscope. Nature Photonics. doi:10.1038/s41566-022-01116-6.