Cells regulate the function of proteins in a variety of ways, including by modifying the structure of proteins. Proteins can take on another form in a flash, do not perform functions, and even perform "wrong" functions: in humans, folding the wrong protein can lead to serious diseases such as Alzheimer's disease, Parkinson's disease And cystic fibrosis. Some of these proteins also tend to "infect" other molecules of the same type and aggregate into insoluble so-called amyloid fibers or plaques. These amyloids can damage cells and tissues and cause people to get sick.

Breaking the shackles

Until now, there has been a lack of methods to quantitatively record structurally modified proteins in complex biological samples. Although there are a series of technologies that can study structurally altered proteins such as X-ray crystallography, nuclear magnetic resonance spectroscopy, and other spectroscopic techniques, none of them can be used to analyze complex biological samples. Other procedures that researchers use to study protein structure changes in cells also have their limitations: Before the analysis, the proteins of interest must be specifically labeled so that scientists can observe them in the sample. However, this method is only possible for some proteins in a sample.

Combination of several methods

To develop new methods, researchers combined an "old" technology with a modern approach to proteomics research. First, a commonly used digestive enzyme (such as proteinase K) is added to the sample. This enzyme cuts the protein into smaller pieces, called peptides, based on the protein structure. Based on the peptides found, the proteins originally present in the sample can be determined and quantified.

What makes it so special: Digestive enzymes can cleave the same protein that has different structures in different places, resulting in different fragments. Just like fingerprints, these fragments can be clearly assigned to the individual structure of the protein.

Parkinsonian protein

Based on this new approach, the researchers designed an experiment to specifically measure "healthy" and "sick" versions of alpha-synuclein in complex, unpurified samples such as blood or cerebrospinal fluid. Alpha-synuclein, when its structure changes, is thought to cause Parkinson's disease. Pathological structural changes and its co-aggregation form amyloid fibers can damage nerve cells.

With experiments, scientists were able to directly measure the exact number of pathogenic and non-pathogenic alpha synuclein in complex samples. The test also produced information on the structure of the protein.

More and more amyloidosis

Over time, the concentration of alpha-synuclein cannot be used as a biomarker because the level of protein in the blood or cerebrospinal fluid of Parkinson's patients is similar to normal people. Professor Picotti said: "However, the ratio of pathogenic and non-pathogenic alpha-synuclein structures is likely to change over time and disease progression because this new method allows us to measure The two structures of α-synuclein in various samples, then we can use it to develop new biomarkers for this disease." Using this method it is also possible to find other, still unknown, amyloid samples. Proteins, according to previous knowledge they are related to disease.