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Pieri Lab Seeking to Perfect a Light-Emitting Protein for Peering Inside Live Tissues

Pieri Lab Seeking to Perfect a Light-Emitting Protein for Peering Inside Live Tissues

June 26, 2024 | By Dave DeFusco

UNC-Chapel Hill researchers are pushing the boundaries of bio-imaging by leveraging the power of computational chemistry. Utilizing advanced computer simulations, the Pieri Lab in the Chemistry Department is making significant strides in designing better biosensors and understanding new light-based reactions.

Bio-imaging allows scientists to see inside live tissues using special molecules that react to light. Despite having many such molecules available, finding the perfect one for each specific situation is challenging. This is where computational chemistry, which uses computer simulations to predict and design these molecules, comes into play.

The Pieri Lab’s primary focus is on photoactive biliproteins, which are proteins that emit light. By studying how changes in their structure affect their properties, they aim to find new systems that could work well for bio-imaging and optogenetics—using light to control cells.

“Understanding and designing these light-sensitive molecules is complex. Photoreactions involve multiple electronic states and happen very quickly, using a lot of energy,” said Pieri, an assistant professor of chemistry at UNC-Chapel Hill. “This makes them challenging to simulate accurately. However, with new techniques and better computers, we can now explore these reactions more systematically.”

A recent study published in the Journal of the American Chemical Society highlights Pieri’s success in understanding the structural intricacies that dictate the brightness of red fluorescent proteins (RFPs), essential tools for bio-imaging. The study, “Conical Intersection Accessibility Dictates Brightness in Red Fluorescent Proteins,” conducted while Pieri was a postdoctoral researcher at Stanford University, focused on two RFPs, mScarlet and mRouge, which have similar sequences but different brightness levels.

Using advanced computational simulations, the researchers identified key factors contributing to these differences. They found that mScarlet’s superior brightness is due to its more rigid structure, keeping the chromophore—the part of the molecule responsible for light absorption and emission—in a flat, strongly light-emitting configuration. In contrast, mRouge’s flexible structure allows the chromophore to twist, leading to energy dissipation and reduced fluorescence.

The study traced differences in protein behavior to specific changes in the area around the chromophore, caused by mutations affecting the electric charge and spatial environment. In mScarlet, strong and numerous hydrogen bonds keep the chromophore flat and light-emitting. In mRouge, a mutation creates more space around the chromophore, allowing it to twist and preventing light emission.

“These insights will enable us to design better fluorescent proteins,” said Pieri. “By understanding the structural factors that govern fluorescence, we can develop more efficient bioimaging tools.”

The potential applications of this research are vast. Improved fluorescent proteins could enhance the capabilities of bio-imaging technologies, allowing scientists to observe cellular and molecular processes in real-time with greater precision and brightness. This can lead to advancements in various fields, from medical diagnostics to biological research.

“As we continue to explore new techniques and applications, our work promises to expand the possibilities for innovation in materials design and bio-imaging,” said Pieri, “offering a versatile tool for creating advanced materials suited to specific industrial and scientific needs.”

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