Scientists at Perm Polytechnic University have developed a method to detect D-amino acids in different parts of the brain even at minimal concentrations. This opens the way for earlier diagnosis of neurodegenerative diseases. This was reported by the “Nauchnaya Rossiya” portal.
Neurodegenerative diseases develop imperceptibly: nerve cells die long before the first symptoms appear. Traditional diagnostics detect changes only at late stages. Scientists are looking for biomarkers – molecules that change in tissues in advance. One candidate is D-amino acids, mirror forms of common L-serine and aspartic acid. In a healthy body, there are few of them, but in pathology, the balance is disturbed.
The problem is that D-amino acids in the brain are extremely scarce compared to other molecules. Tracking their growth and not confusing them with other compounds is extremely difficult. Existing approaches are either too expensive or not accurate enough.
How the method works
Perm scientists combined two approaches. First, the sample is passed through a liquid chromatograph, where molecules are separated by their speed of movement. Then the mixture is sent to a mass spectrometer – a device that identifies molecules by mass and filters out foreign compounds. This allows target substances to be isolated even in a sample with hundreds of components.
To test the method, post-mortem samples from three brain regions were taken: the left and right frontal lobes, and the left temporal lobe. The material was crushed, the liquid part was extracted, and treated with dansyl chloride – a substance that “highlights” amino acids for instruments.
Results
In all zones, D-serine was many times less than L-serine. This is a normal picture. But the method allowed even small concentrations to be recorded. The indicators of the areas differed: in the left temporal lobe – 5.6 µg/g, in the frontal lobes – from 6.9 to 9.3 µg/g. This means that for diagnosis, not only the total amount of molecules is important, but also where exactly they are located.
Associate Professor of the Department of Chemistry and Biotechnology at PNNPU, Leonid Asnin, explained that complete separation of a complex biological sample by chromatograph was not achieved, so the mixture was additionally sent to a mass spectrometer. The device was pre-configured to search for molecules with a specific mass, known for D-forms.
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