Amyloid fibrils are deposits of proteins in the body that build up in the form of nano-sized fibres. Their formation has been linked to many human diseases including Alzheimer's and Parkinson's. Understanding how these fibrils grow could inform the treatment of these diseases and other areas of bioscience that rely on protein folding and self-assembly.
Most experimental techniques for measuring fibril growth have limitations, either measuring the average growth of a collection of fibrils, or measuring just one fibril under conditions that may not be representative of biological conditions.
For the first time, this study, published in RSC Chemical Biology, used Small Angle Neutron Scattering (SANS) to study the growth rate and length of amyloid fibrils as they assemble. By using the unique way that neutrons interact with hydrogen and its isomer deuterium, the researchers were able to create contrast pictures to measure the number of fibril ends present. This enabled them to know how many were growing and how long each of them were.
Fibril formation is greatly influenced by the presence of 'seeds'; proteins that prompt the initial growth. As well as accelerating growth, the seeds may also influence the shape and structure of the fibrils themselves, which may lead to different physiological effects.
This experiment on the Sans2D instrument was able to use the contrast method to produce the seeds in a way that meant they were effectively invisible to neutrons, enabling the researchers to focus their study on the growing fibrils. Their growth rate results align with those from other techniques, indicating that SANS is a suitable method for measuring amyloid fibril growth.
The fibrils studied in this experiment grew in a cylindrical shape, but the researchers believe that the technique could be applied to systems where other shapes are formed, or where particularly long fibrils are present.
Lead researcher, Dr Ben Eves, carried out the experiments in the laboratory of Dr Adam Squires at the University of Bath, as part of his ISIS Facility Development studentship. He is now a Postdoctoral Research Fellow at the Princess Margaret Cancer Centre in Toronto, which is part of the University Health Network.
“I'm thrilled with the success of this method." He says; “Developing this technique at the ISIS Neutron and Muon Source, a world-leading research centre, in collaboration with the University of Bath was a truly amazing experience. Understanding the growth of amyloid fibrils is fundamental to their pathogenic, biological and technological properties."
He adds; “In future, I believe this technique could be used to investigate the effect of solution conditions on the rate of amyloid fibril elongation, as well as to measure the impact of inhibitors that slow down or prevent the growth of amyloid fibrils."
Further information
The full paper can be found online at DOI: 10.1039/D1CB00001B
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