Eric Betzig: Not Resting on His Laureate
"If you want to understand any dynamic system, no matter how good your information is about its components, no matter how good the static images of these components are, it's not enough to understand that system," noted Eric Betzig at the BiOS Plenary Session at SPIE Photonics West, where he talked about "the secret life of cells" and some of his work involved in discovering that secret life.
Betzig opened his talk with a little history of the compound microscope, which was invented some 400 years ago. But until the 1980s, it was limited in its resolution and contrast. Biologists in the 20th century created new techniques to study cellular dynamics, such as biochemical assays to break apart cells; molecular biology to determine the cellular genetic blueprint; and structural biology to understand the structure of cells. But even with these powerful tools, researchers couldn't capture how various parts of living cells interacted with each other.
To help explain the issue, showed a slide of a BMW engine with all its parts laid out. "If I had no prior knowledge of how combustion works, or how the gears or the crankshaft works, it would be damned difficult for me to reverse engineer that," he said. "Many of the tools I just described don't give a comprehension of all of the parts, so you're missing many of the parts. If you're doing biochemistry over express, now you have three crankshafts and 18 pistons and you're wondering how that's going to work. Starting in the 1980s optical microscopy would start to play a bigger role in in biology."
Betzig's work in this role in the 80s and 90s led to the 2014 Nobel Prize "for the development of super-resolved fluorescence microscopy," which he shared with Stefan Hell and William E. Moerner. Not one to sit back after recognition, Betzig has maintained super-resolution momentum in his research career. He is currently a Senior Fellow at the Howard Hughes Medical Institute's (HHMI), Janelia Farm Research Campus, where he and his lab team develop new optical imaging technologies for biology. He and his wife, biophysicist Na Ji, both serve as faculty scientists in the Molecular Biophysics and Integrated Bioimaging Division of the Biosciences Area at University of California at Berkeley.
The need to go somewhere
Betzig describes himself as the proverbial "jack-of-all trades; master of none." He doesn't consider himself a chemist, a physicist, or even a scientist. "I'm an engineer at heart," he says. "Particularly a systems engineer, where you bring in little pieces of knowledge across different disciplines and stir them all together and hook up something new."
Growing up during the Apollo era, Betzig was all about becoming an astronaut. One of his heroes was, and still is, Joe Shea, who was head of the Apollo Spacecraft Program Office. "He had to bring together the engineering skills of about 30,000 people scattered all across the country and try to make the command and service modules for the Apollo program," Betzig explains. "So he had to have all of these details in his head."
When the the shuttle program was being developed, he became more interested in physics because he "wasn't interested in circling, I wanted to go somewhere." As an undergraduate at Cal Tech, he switched from theory to experiments, realizing that he enjoyed building things with his hands.
"There's a huge difference between what you learn in the classroom and what you learn in the lab," says Betzig. "I found out that I actually enjoyed building things and making widgets much more than I liked studying and learning quantum mechanics. There is nothing like the excitement of actually building an experiment and getting it to work."
Journey to PALM
Betzig's career has three stages — the first began with near-field microscopy, which he began working on in 1982 as a graduate student at Cornell. By 1992, he had his own lab at Bell Laboratories where he built a near-field microscope, that he says was too slow and difficult to use. Frustrated with the project, Betzig quit Bell Labs in 1994. For the next eight years, he worked as vice president of R&D in his father's machine tool company where he developed a high-speed motion-control technology based on an electrohydraulic hybrid drive with adaptive control algorithms. The technology was a commercial failure, so he left the business. "You'll learn a hell of a lot more from a failure then you do from a success," said Betzig. "All my failures shaped my career. So, pain is the best teacher."
After leaving his father's business, Betzig became a stay-home dad, taking long walks in the woods and wondering what to do next. His main plan at the time was to stop making microscopes, but inspiration had other plans. A couple of months into this meditative life, insight came to him as he was pushing his child's stroller — an idea of how to make his microscope finally work. He and former Bell colleague Harald Hess worked on the concept of using stochastic photoactivation instead of color to isolate molecules. Their work led to the super-resolution technique of photoactivated localization microscopy (PALM).
"We were both unemployed, so we built it in Harold's living room," said Betzig "Since we knew zero biology, we contacted Jennifer Lippincott-Schwartz at NIH who had invented a photo-activatable fluorescent protein. Within about a month of working in her lab, we improved the resolution."
As Betzig explained to Show Daily, even though the round, diffraction-limited spot representing the image of a single fluorescent molecule in a conventional optical microscope is 100 times larger than the molecule itself, it is possible to point to the center of the spot with much better precision than its diameter, just as you can point precisely to the center of a basketball. The problem is that in most biological samples, the fluorescent molecules are so closely packed that their diffraction-limited images overlap, making it impossible to isolate each and localize their centers. The trick in PALM is to use special molecules to tag the proteins of interest that can be "turned on" from a non-fluorescent state to a fluorescent one with a second color of "activating" light. By reducing the intensity of the activating light to a very low level, only a few molecules will be active at a given time. This active subset will likely be well separated others, and hence can be precisely localized to a small fraction of the diffraction limit (~10-20 nm). The active subset is turned off, and the cycle is repeated until most of the molecules in the sample are precisely located, creating the super-resolution PALM image.
It's a simple enough technique," says Betzig. "You can get 20 nanometer resolution in your living room, so as a result it took off very quickly and eventually led to Stockholm, to my still great surprise."
The journey ahead
In conclusion, Betzig noted that going forward, the real challenge for microscopy is making existing microscopes accessible to biologists. "That's why we have the Advanced Imaging Center at Janelia and the Advanced Bio-imaging Center at Berkeley," said Betzig. "We present plans for everybody to build their own. But it is a slow, slow process until commercialization sets in."
Betzig added that he and other researchers "have petabytes of data we can't deal with." Computational tools to handle data at this scale need to be developed.
"The 20th century was an incredible century for discovery in biology thanks to biochemistry, molecular and structural biology and, I think, to a lesser extent, optical microscopy," said Betzig. "But, if we can get these tools in the hands of biologists, that will launch a new level of discovery in the 21st century where optical microscopy will stand as an equal aside biochemistry, molecular biology, and structural biology."
A shortened version of this article appeared in the 2020 Photonics West Show Daily.
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