transmission electron microscopy
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Fractals are complex geometric patterns repeated at progressively smaller scales. You’ll find them throughout nature. That includes in the 3D structures and shapes of tissues throughout our bodies, from the bones in our skulls down to the blood vessels in our feet. But the fractal pattern above isn’t from a precisely patterned human tissue. It comes from some unexpected biochemistry that formed the stunning pattern on its own.
In fact, the exact source for this fractal pattern reminiscent of peacock feathers isn’t known. It turned up out of the blue (and green) in a sample that had been sitting around on the shelf for some time. The original image appeared in black and white, but the colors added post-collection help to highlight the fractal pattern of a sample including an essential hormone produced in the pancreas. The hormone is called islet amyloid polypeptide (IAPP).
Also known as amylin, IAPP plays many important roles in our bodies, including the feeling of fullness after a meal. But the amino acid chains that make up IAPP also are prone to forming abnormal clumps of misfolded polypeptides (a long name for proteins) known as amyloids. Much like the amyloid plaques in the brains of people with Alzheimer’s disease, misfolded IAPP amyloids in people with type 2 diabetes also can damage insulin-producing beta cells in the pancreas and make controlling their blood sugar levels even more difficult.
This unusual image comes from graduate students Bryan Bogin and Matthew Steinsaltz. They study the biophysics and biochemistry of protein folding and misfolding in the lab of Zachary Levine, Yale School of Medicine, New Haven, CT. The Levine lab recently moved to the Altos Labs San Diego Institute. However, Bogin and Steinsaltz continue to conduct their studies at Yale.
The two conduct in-solution experiments and molecular simulations to elucidate the precise conditions and triggers that can lead otherwise normal polypeptide chains to fold up incorrectly and wreak havoc as they do in diabetes and other diseases. When Steinsaltz was learning how to use transmission electron microscopy (TEM), a technique in which an electron beam captures images including detailed molecular-level structures, Bogin handed over an assortment of IAPP samples in different solution conditions from some of his past experiments for a look.
In those microscopy images, they expected to see long, linear fibrils consisting of IAPP polypeptides. While that’s indeed what they saw in most of the samples, this one was the exception. It was such a remarkable image that they submitted it in the Biophysical Society’s 2022 Art of Science Image Contest, where it took the top prize.
Bogin and Steinsaltz say they still can’t explain the source or meaning behind these unusual fractal patterns. But they do continue to conduct experiments to understand how various polypeptides implicated in health and disease misfold to form destructive aggregates. This striking image may not hold the answers they seek, but it is an inspiring reminder that the path to making groundbreaking biomedical discoveries will have many beautiful surprises along the way.
Type 2 Diabetes (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)
Zachary Levine Lab (Yale School of Medicine, New Haven, CT)
Art of Science Image Contest (Biophysical Society, Rockville, MD)
NIH Support: National Institute on Aging