Graduate Student Spotlight: Yang Liu Develops a New Method for Chemistry with “Roots” in Biology

Yang Liu in the lab. Photo provided by Yang Liu.
Yang Liu in the lab. Photo provided by Yang Liu.

Yang Liu (Salaita Group) is bringing new techniques to the emerging field of mechanobiology; at the same time, he’s returning to his roots.

Literally. As in, plants.

Yang’s father is an academic biologist studying agriculture in China.

“I think in the beginning, my dad really wanted me to be a biologist,” says Yang. “But normally kids don’t want to pursue the same career path as their parents.”

As an undergraduate in China, Yang started out studying mechanical engineering. Then, he attended a general chemistry lecture with a famous chemistry professor who made a convincing case for the importance of the discipline. “He said, ‘chemistry is the central science connecting physical sciences, life sciences and applied sciences all together,’’ says Yang. “And I was so fascinated by it. And I changed my major.”

At Emory, Yang joined the lab of Khalid Salaita. His research in the Salaita Group takes a novel approach to a common scientific question: how does the immune system recognizes and eliminates “invaders”, such as pathogens or cancer cells? Most research explores how chemical signals mediate this process. Yang’s work expands on existing work in the Salaita Group that focuses on mechanical signaling—the way that immune cells physically probe their targets within the body. “Cells can touch and apply forces to one another,” explains Yang, a process he refers to as a “handshake.” Yang’s research develops tools that allow scientists to “see” these kinds of physical interactions.

Gold nanoparticle (yellow) with elastic spring molecules (gray) bound to a fluorophore and ligand (black). When a ligand binds to a membrane receptor (cyan), the spring “pulls” and the fluorophore elicits a signal (bright white).
Gold nanoparticle (yellow) with elastic spring molecules (gray) bound to a fluorophore and ligand (black). When a ligand binds to a membrane receptor (cyan), the spring “pulls” and the fluorophore elicits a signal (bright white). Photo provided by Yang Liu.

Specifically, Yang has developed a technique named molecular tension fluorescence microscopy (MTFM) that employs single elastic molecules—DNA, protein, and polymer— as sensors to visualize membrane receptor mediated forces at the piconewton level. “One piconewton is the weight of one trillionth of an apple and surprisingly, pN forces regulate biochemical signaling pathways,” says Yang. These forces are too small for scientists to measure using conventional methods. Existing tools aren’t sensitive enough or they are inefficient.

“Until our method kicks in,” says Yang.

Yang has combined nanotechnology and the “easy” surface chemistry of gold nanoparticles to make MTFM probes more effective. “These gold particle sensors are spring scales at nanoscale ,” says Yang. “Compared to previous techniques, these probes are of significantly enhanced sensitivity, stability and amenable for detecting forces mediated by almost all kinds of cell receptors.”

The improvements have caught the attention of researchers in other Emory units—and even nationally and internationally. Yang has collaborated with the Evavold Lab in the Department of Immunology at Emory to help them measure mechanical forces mediated by different immune cells. He also has collaborators from as far away as New York and Germany.

Regarding these collaborations, Yang says: “The need to be trained [to use this method] is very high. The method is not hard, it’s easy. So people usually spend a few days and they should be able to master it…and we still maintain quite tight collaboration. We not only teach them how to make it, we actually get involved in the scientific questions they care about and continue this collaboration.”

Recently, Yang’s success in developing the new method was recognized with the department’s highest graduate student honor, the Quayle Outstanding Student Award. Speaking of Yang’s progress shortly after the award ceremony, advisor Khalid Salaita praised Yang’s work ethic as well as his science: “Yang was a real pleasure to have in the lab. He was incredibly thoughtful, well read, and intensely motivated. More than anyone else I’ve worked with, Yang displayed a keen instinct for experimental design. He spent countless hours in the dark microscope room collecting data and working around the clock fueled up with his favorite bbq Pringles and excited by the science.”

The award ceremony was followed swiftly by another milestone—a successful PhD defense. Next, Yang is headed to John’s Hopkins University where he will work in the lab of Dr. Taekjip Ha, a world leader in the development of single molecule fluorescence microscopy and force spectroscopy.

Salaita Group "Logo"
Salaita Group Logo

Yang’s pioneering research wasn’t always smooth sailing. “I didn’t get my first experiment done until the first semester of my third year. Everything before that didn’t work.” He credits his perseverance to his father’s example—“agriculture is even slower, waiting for the growth of plants. You can only do two experiments a year!”—as well as his own scientific curiosity. His advisor, Khalid Salaita, was also an inspiration throughout the process. “He is always passionate and ignited my love for science. You love it and you work hard to make something meaningful to the society and also make yourself valuable, so, that’s what I’d like to do and that’s because of these two people.”

Does all this mean that Yang has overcome his initial reluctance to follow in his father’s footsteps towards biology?

“I think I’m going back to the route, mining chemistry, biology. In the beginning I was against it, but I do like it.” Still, chemistry has his heart. “Chemists not only create new tools, new theories and new materials, but also create new opportunities. And if you want to study biology as a chemist, there are some advantages too because you can understand and explore the secret of life at the molecular level.”