Researchers have developed a new imaging technique to illuminate interlocking peptides using a chemical probe. This method will help scientists distinguish between synthetic peptides and toxic ones that are associated with Alzheimer’s disease. The engineers at Washington University in St. Louis created the technique to provide a closer examination of fibril assemblies, particularly those made of amyloid beta, which are commonly linked to Alzheimer’s disease. These cross-β fibril assemblies are not only found in Alzheimer’s disease but are also important in the construction of designer biomaterials for medical purposes.The concern about the toxicity and function of amyloid beta and its relatives, which are associated with neurodegenerative disease, has led researchers to investigate the connection between different peptide sequences. This includes both naturally occurring peptides and engineered synthetic versions.
Through a collaboration between lead author Matthew Lew, associate professor in the Preston M. Green Department of Electrical & Systems Engineering, and Jai Rud, scientists have been able to closely examine the differences in how synthetic peptides stack up compared to amyloid beta fibril assemblies. The results show notable variations in the way these peptides assemble.ra, a member of the faculty of biomedical engineering at WashU’s McKelvey School of Engineering.
“We design microscopes to improve nanoscale measurements in order to advance the field of science,” Lew explained.
In a recent article published in ACS Nano, Lew and her colleagues describe their use of the Nile red chemical probe to illuminate cross-β fibrils. Their method, known as single-molecule orientation-localization microscopy (SMOLM), utilizes the bursts of light emitted by Nile red to visualize the fiber structures created by synthetic peptides and amyloid beta.
In summary, these assemblies are significantly more complex and diverse than previously thought.The discovery of more protein stacking possibilities is a positive development, as it indicates that there are multiple safe methods for stacking proteins. By obtaining improved measurements and images of fibril assemblies, bioengineers can gain a better understanding of the regulations that determine the impact of protein structure on toxicity and biological functionality. This, in turn, can lead to the development of more efficient and less harmful therapeutic treatments.
However, in order for scientists to distinguish between these protein assemblies, they first need to be able to detect the differences, which is a considerable challenge due to the minuscule scale of these structures.
“The helical twist of these fibers is impossible to discern using an optical microscope, or even some super-resolutiLew mentioned that microscopes are essential for observing things that are too small to see with the naked eye. In the past few years, Lew’s lab has developed high-dimensional imaging technology that allows them to observe these differences. A typical fluorescence microscope uses fluorescent molecules to illuminate specific aspects of a biological target. In this particular study, they utilized a fluorescent probe called Nile red to sense its surroundings. As Nile red moves through its environment and interacts with the fibrils, it produces bursts of light, which can be measured to determine the probe’s location and orientation. This data allows them to analyze the behavior and characteristics of the fluorescent probe.The team has successfully pieced together a comprehensive understanding of engineered fibrils, which differ greatly from natural ones such as amyloid beta. The visual representation of these fibril assemblies was featured on the cover of ACS Nano and was created by Weiyan Zhou. By color-coding the image based on the orientation of the Nile reds, the resulting image resembles a blueish, red flowing assembly of peptides, reminiscent of a river valley.
Moving forward, the team aims to further develop techniques like SMOLM in order to explore new methods for studying biological structures and processes at the nanoscale. According to Lew, this approach allows them to observe things that were previously impossible with existing technology.
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