NanoporesPublished on 18.01.2017

'Protein fingerprinting' could help fight Alzheimer's, Parkinson's

In an advance that could one day lead to progress against neurodegenerative diseases like Alzheimer’s and Parkinson’s, Adolphe Merkle Institute (AMI) and University of Michigan researchers have demonstrated a technique for precisely measuring the properties of individual protein molecules in a liquid solution.

Measuring proteins in blood and other body fluids could unlock valuable information, as these molecules are a vital building block in the body, essential to the function of every cell. The body manufactures them in a variety of complex shapes that can transmit messages between cells, carry oxygen, and perform other important functions.

Sometimes, however, proteins don’t form properly. Scientists believe that some types of these misshapen proteins, called amyloids, can clump together into masses in the brain. The sticky tangles block normal cell function, leading to brain cell degeneration and diseases such as Alzheimer’s and Parkinson’s.

But the processes of how amyloids form and clump together are not well understood. This is due in part to the fact that there’s currently no optimal method to study them. Researchers say current techniques are expensive, time-consuming and difficult to interpret, and can only provide a broad picture of the overall level of amyloids in a patient’s system.

The researchers at AMI and the University of Michigan who developed the new approach believe that it could help solve the problem by measuring an individual molecule’s shape, volume, electrical charge, rotation speed and propensity for binding to other molecules. They call this information a “5-D fingerprint” and believe that it could uncover new information that may one day help doctors track the status of patients with neurodegenerative diseases and possibly even develop new treatments.

The researchers say current techniques for identifying proteins are similar to identifying a person based only on their weight and height. The 5-D fingerprinting adds more descriptors making it simpler to identify specific proteins.

Michael Mayer, the lead author of a paper published by the journal Nature Nanotechnology and AMI’s chair of Biophysics, says identifying individual proteins could help doctors keep better tabs on the status of a patient’s disease, and it could also help researchers gain a better understanding of exactly how amyloid proteins are involved with neurodegenerative disease.

To take the detailed measurements, the research team uses a nanopore, a passage in a surface that is just ten to 30 nanometers wide - so small that only one protein molecule can fit through at a time. The nanopore is filled with a salt solution and an electric current is passed through the solution.

As a protein molecule tumbles through the nanopore, its movement causes tiny, measurable fluctuations in the electric current. By carefully measuring this current, the researchers can determine the protein’s unique five-dimensional signature and identify it nearly instantaneously.

“Amyloid molecules not only vary widely in size, but they tend to clump together into masses that are even more difficult to study,” said Mayer, who launched the research at the University of Michigan and finalized it at AMI. “Because it can analyze each particle one by one, this new method gives us a much better window into how amyloids behave inside the body.”

Ultimately, the team aims to develop a device that doctors and researchers could use to quickly measure proteins in a sample of blood or other body fluid. This goal is likely several years off; in the meantime, they are working to improve the technique’s accuracy, honing it in order to get a better approximation of each protein’s shape. They believe that in the future, the technology could also be useful for measuring proteins associated with heart disease and in a variety of other applications as well.

“I think the possibilities are pretty vast,” said David Sept, a University of Michigan biomedical engineering professor who worked on the project. “Antibodies, larger hormones, perhaps pathogens could all be detected. Synthetic nanoparticles could also be easily characterized to see how uniform they are.”

Article in Nature Nanotechnology:

Yusko E.C., Bruhn B.R., Eggenberger O.M., Houghtaling J.,  Rollings R.C., Walsh N.C., Nandivada S., Pindrus M., Hall A.R., Sept D., Li J., Kalonia D.S., Mayer M. Real-time shape approximation and fingerprinting of single proteins using a nanopore, Nat. Nanotech., 2016