Measuring Up

​​Nanoscience’s measurement tools provide amazing insights into how things work at the atomic and molecular level. Take, for example, the way bacteria fight viruses. Thanks to new gene splicing technology, we can see what an amazing machine nature has built to protect bacteria from infection. Then there is a new way to trace how cells interact and move around in tissues during development and disease. And, thanks to a combination of atomic force microscope and scanning tunneling microscope, we can understand how oxygen fills defects in atomically thin semiconductors. On the lighter side, nanoscience also unveils, for the first time, how bees surf on water.

---

• Killer CRISPR

CRISPR-Cas9 has revolutionized gene editing by making it easy to cut and insert DNA into genes. Yet when we try to use those modified genes, they sometimes lead to lethal mutations. To tame CRISPR, scientists need to understand more about how it works in nature. That means studying bacteria, which use it to slice and dice viral invaders. To find out more, Stan Brouns, a member of the Kavli Institute of Nanoscience at Delft Technical University, used laser pulses to freeze the action of CRISPR-Cas systems as it went chased viruses inside bacteria. This worked like a strobe light in a disco to freeze the action and see what was going on. His team found a single CRISPER complex could sort through 100 viruses (or other floating pieces of DNA) per second. When it found an invader, the Cas molecule sliced it apart. CRISPER-CAS is so effective, a bacteria would need only 20 copies to give it a 50-50 chance of survival in the wild.

• Tracing cellular ancestry

A cell’s behavior cell depends on its genetic history and its location within a tissue. One way to trace that is to insert DNA “barcodes” into cells that will produce markers that show up when specific events occur, when the cells use specific genes, or when the cells split and divide. Researchers can insert those barcodes into cells within tissues, but they must remove the cells to analyze the results. Now, thanks to a team of Caltech researchers led by Michael Elowitz, a member of the Kavli Nanoscience Institute, they can observe those markers while the cells are still in the tissue. This is important because the position of a cell often reveals information about, says, how it functions in the brain or how it changes as part of a solid cancer tumor.

• The upside of defects

Atomically thin (2D) semiconductors know as transition metal dichalcogenides (TMDs) can absorb and emit light, conduct electricity, or act as catalysts. That’s good news if you want to make quantum light emitters and optoelectronic devices. But their behavior is largely due to defects. Now, thanks to researchers led by Jeff Neaton, a member of the Kavli Energy NanoScience Institute at Berkeley, we are learning more about how those imperfections work. Neaton looked at tungsten disulfide and molybdenum diselenide, which often have vacancies with missing sulfur or selenium. It turns out that those empty spaces can be filled with oxygen, and Neaton’s team has found a way to create them. This will enable researchers to study just how oxygen can modifies TMD properties. They have already discovered some unusual hybrid electronic states.

• Let’s go surfing now

How many times have you seen a bee flapping its wings in a pool or pond of water? The bee in not trying to fly away—water sticking to the bottom of its wings makes it too heavy to fly. Instead, it is creating a series of waves that it can body surf to shore (or the edge of a pool). They use a very different type of stroke when surfing, moving their wings up and down only 10 degrees, as opposed to 90-120 degrees when flying. The downside is that bees can keep this up only about 10 minutes before they drown. The insights come from the work of Chris Roh, a research engineered, who noticed the wave pattern of a bee stuck in a fountain and then worked with his advisor, Mory Gharib, a member of Caltech’s Kavli Nanoscience Institute. They believe they can apply this technique, which uses very little energy, to robots that can both fly and swim.