Graphene balloon yields unprecedented images of hydrated protein molecules

February 5, 2014 by Marcia Goodrich
Graphene balloon yields unprecedented images of hydrated protein molecules
In this image generated by an electron microscope, the white dots are the protein ferritin. The dark circle in the middle is a bubble of water vapor trapped within the graphene capsule enclosing the sample.

(Phys.org) —A graphene water balloon may soon open up new vistas for scientists seeking to understand health and disease at the most fundamental level.

Electron microscopes already provide amazingly clear images of samples just a few nanometers across. But if you want a good look at living tissue, look again.

"You can't put liquid in an electron microscope," says Tolou Shokuhfar, of Michigan Technological University. "So, if you have a hydrated sample—and all living things are hydrated—you have to freeze it, like a blueberry in an ice cube, and cut it into a million thin pieces, so the electrons can pass through. Only then can you image it to see what's going on."

After such treatment, the blueberry isn't what it was, and neither is . Shokuhfar, an assistant professor of mechanical engineering-engineering mechanics, wondered if there might be a way to make more friendly to biological samples. That way, you might get a much better view of what's really going on at the sub-cellular level.

So she joined colleagues at the University of Illinois-Chicago (UIC), and together they found a way. "You don't need to freeze the blueberry, you don't need to slice it up with a diamond knife," she said. "You just put it in the electron microscope, and you can get down and see the atoms."

The trick was to encapsulate the sample so that all the water stayed put while the electrons passed through freely. To do that, the team, including Robert F. Klie, an associate professor of physics and mechanical and industrial engineering at UIC, and UIC graduate student Canhui Wang, turned to graphene.

"Graphene is just a single layer of carbon atoms, and electrons can go through it easily, but water does not," Klie said. "If you put a drop of water on graphene and top it with graphene, it forms this little balloon of water." The graphene is strong enough to hold the water inside, even within the vacuum of an electron microscope.

The team tried their technique on a biochemical that plays a major role in human health: . "It's a protein that stores and releases iron, which is critical for many body functions, and if ferritin isn't working right, it may be contributing to lots of diseases, including Alzheimer's and cancer," Shokuhfar said.

The team made a microscopic sandwich, with ferritin immersed in as the filling and as the bread, and sealed the edges. Then, using a scanning , they captured a variety of images showing ferritin's atomic structure.  In addition, they used a special type of spectroscopy to identify various atomic and electronic structures within the ferritin. Those images showed that the ferritin was releasing iron and pinpointed its specific form.

If the technique were used to compare ferritin taken from diseased tissue with healthy ferritin, it could provide new insights into illness at the molecular level. Those discoveries could lead to new treatments. "I believe this will allow us to identify disease signatures in ferritin and many other proteins," Shokuhfar said.

Explore further: Physics group uses graphene to allow electron microscopy of liquid objects

More information: Wang, C., Qiao, Q., Shokuhfar, T. and Klie, R. F. (2014), "High-Resolution Electron Microscopy and Spectroscopy of Ferritin in Biocompatible Graphene Liquid Cells and Graphene Sandwiches." Adv. Mater.. DOI: 10.1002/adma.201306069

Related Stories

What can a graphene sandwich reveal about proteins?

December 11, 2013

(Phys.org) —Stronger than steel, but only one atom thick - latest research using the 2D miracle material graphene could be the key to unlocking the mysteries around the structure and behaviour of proteins in the very near ...

Graphene growth on silver

January 14, 2014

Users from Northwestern University, working with the Center for Nanoscale Materials EMMD Group at Argonne, have demonstrated the first growth of graphene on a silver substrate.

Recommended for you

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

Meet the high-performance single-molecule diode

July 29, 2015

A team of researchers from Berkeley Lab and Columbia University has passed a major milestone in molecular electronics with the creation of the world's highest-performance single-molecule diode. Working at Berkeley Lab's Molecular ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.