Vision Research Involves Use of Ultrafast Imaging

Thomas D. Grant, PhD.

Thomas D. Grant, PhD

Published April 30, 2019

Thomas D. Grant, PhD, research assistant professor of structural biology, is co-principal investigator on a research project using ultrafast imaging technologies to study how vision occurs at the molecular level.

The National Science Foundation has funded the three-year study, titled “Light-Induced Protein Quake of Visual Rhodopsin Investigated by Femtosecond Time-Resolved X-Ray Scattering,” with an $800,000 grant.

X-Ray Scattering Reveals Atomic Structures

Rhodopsin is the major protein involved in vision, and it serves as an archetype for determining molecular movies of receptors in action.

“Rhodopsin is responsible for sensing light in the eye,” Grant says. “When light gets absorbed by rhodopsin, it causes changes in its atomic structure, which results in a series of interactions with other proteins that ultimately send a signal to the brain triggering vision.”

The research project will investigate the light activation mechanism of visual rhodopsin in solution.

“We’re using a technique called solution scattering along with essentially the fastest X-ray camera in the world — called an X-ray free-electron laser (XFEL) — to look at what the earliest changes in the atomic structure of rhodopsin are when it absorbs light, those first few trillionths of a second,” Grant says.

“Doing so will allow us to understand in greater detail how human vision works, and more broadly, how many signals are sent throughout cells on an atomic scale,” he adds.

Protein Motions Triggered By Light Absorption

The research promises to illuminate the earliest events of light activation that occur in the eyes, together with the protein changes that yield vision.

The primary benefit of the research is to understand how light absorption by visual rhodopsin leads to changes in its mobility followed by transmission of a nerve signal to the brain.

Time-resolved X-ray studies of rhodopsin in detergent solutions will reveal the protein motions triggered by light absorption of its cofactor (retinal, a derivative of Vitamin A).

Computer simulations will further interpret the experimental observations in terms of changes in the dynamics of the protein molecules due to light.

Other principal investigators on the study are from the following institutions:

  • Arizona State University
  • University of Arizona
  • University of Rochester