NPR : News

Filed Under:

How Tears Go 'Pac-Man' To Beat Bacteria

They mystical healing properties of tears are invoked in fairy tales and fantasies from Rapunzel to Harry Potter. So it may surprise you to hear that tears really are pretty powerful, on the microbial level at least.

In 1922, a few years before he won the Nobel Prize for his discovery of penicillin, bacteriologist Alexander Fleming discovered in human tears a germ-fighting enzyme which he named lysozyme. He collected and crystallized lysozyme from his own tears, then wowed contemporaries at Britain's Royal Society by demonstrating its miraculous power to dissolve bacteria before their very eyes.

"That's a seriously bodacious experiment," Gregory Weiss, professor of molecular biology at the University of California, Irvine, tells Shots. Weiss is co-author of a paper on a modern-day bodacious experiment that for the first time reveals details of how lysozyme works.

"People had always wondered, did 100 molecules gang up and attack a bacterium?" says Philip Collins, a physics professor at Irvine who joined the interdisciplinary research team. "What we've shown is that just one molecule of enzyme is enough."

How is that possible? Well, each molecule is essentially a set of voracious jaws that latches on to microbial invaders, starts chewing and doesn't let go. "The enzyme opens and closes almost like a Pac-Man mouth as it chomps away," Collins says, which means it can chew through bacterial cell walls as easily as scissors slice through paper.

"This tells us that the enzyme opens huge, gaping holes in the bacteria, which cause the bacteria to explode," Weiss says.

Each tear you shed contains an army of these enzymatic Pac-Men, ready to chase down and gobble up germs before they infect the sensitive tissues around your eye. But in order to study their motion up close, the researchers had to keep one of the molecules still. And to do that, they relied on some very tiny technology: carbon nanotubes.

The team attached a lysozyme molecule to a nanotube, using an amino acid as a tether. Then they passed an electric current along the tube, essentially turning the molecule into a very tiny transistor. When the molecule sprang into action, each chomp of its jaws produced a blip of electrical activity, like the dit-dit-dit of a telegraph.

That signal was like "a microphone that allowed us to listen in on the enzyme's activity," Collins says.

The findings were just published in the journal Science.

The researchers plan to use this technique to study many other molecules. Down the road, everything from DNA, to pharmaceuticals, to cancer biomarkers could be incorporated into similar biological transistors.

"We're building circuits that are hybrids between biology and technology," Weiss says. "It's fun because we're building a new field. It's something that hasn't been done, and that's what makes it exciting."

Copyright 2012 National Public Radio. To see more, visit


No Meekness Here: Meet Rosa Parks, 'Lifelong Freedom Fighter'

As the 60th anniversary of the historic Montgomery Bus Boycott approaches, author Jeanne Theoharis says it's time to let go of the image of Rosa Parks as an unassuming accidental activist.

Internet Food Culture Gives Rise To New 'Eatymology'

Internet food culture has brought us new words for nearly every gastronomical condition. The author of "Eatymology," parodist Josh Friedland, discusses "brogurt" with NPR's Rachel Martin.
WAMU 88.5

World Leaders Meet For The UN Climate Change Summit In Paris

World leaders meet for the UN climate change summit in Paris to discuss plans for reducing carbon emissions. What's at stake for the talks, and prospects for a major agreement.


Payoffs For Prediction: Could Markets Help Identify Terrorism Risk?

In a terror prediction market, people would bet real money on the likelihood of attacks. NPR's Scott Simon speaks with Stephen Carter about whether such a market could predict — and deter — attacks.

Leave a Comment

Help keep the conversation civil. Please refer to our Terms of Use and Code of Conduct before posting your comments.