The following metadata refers exclusively to electron paramagnetic resonance (EPR) measurements, which represent the contribution of the PARACAT students to this work Data type: EPR spectroscopic measurements and simulations Files are in .DTA, .DSC, .m, .mat, and .xlxs, formats Information on origin of the data: EPR spectroscopic measurements in .DTA and .DSC formats EPR spectroscopic simulation and analyses in .m and .mat format “Ready-to-plot”, processed EPR spectra are in .xlxs format. The data are generated by: CW-EPR measurements were performed with a Bruker ELEXSYS E580 X-band spectrometer equipped with a Bruker ER4118 SPT-N1 resonator operating at a microwave (MW) frequency of ∼9.7 GHz. The temperature was set to 25 °C and controlled by a liquid nitrogen cryostat. If the dataset includes multiple files that relate to each other: Files in PARACAT_WP3_20221219_EPR folder includes EPR spectroscopic measurements and computer simulations/analyses, original data are in .DTA/.DSC formats; files in .m format were used to process the data. NB. See the “READ ME” text file for more detailed information on files organization. Information on: Abbreviations: avg = averaged aS_24 = alpha-synuclein protein with TEMPOL spin label at position 24 of the polypeptidic chain aS_122 = alpha-synuclein protein with TEMPOL spin label at position 122 of the polypeptidic chain pLK = poly-lysine Tau441 = Tau protein with complete amino-acid sequence Tau_DNt = truncated Tau protein lacking N-terminal (see paper methods for further details) Units of measurement: Temperature: °C (Celsius) Microwave Frequency: GHz (Giga-Hertz), MHz (Mega-Hertz), kHz (kilo-Hertz) Microwave Power: mW (milli-Watt) Magnetic Field: mT (milli-Tesla) Time: s (seconds) Concentration: μM (micro-Molar), % w/v (percentage weight-volume)

 EPR data: The .DTA and .DSC files can be opened on proprietary EPR softwares from Bruker or MatLab (version R2021b, used by the authors) with EasySpin toolbox (version 6.0.0-dev.34, used by the authors). The simulation scripts of EPR measurements can be opened and run on MatLab (version R2021b, used by the authors) with EasySpin toolbox (version 6.0.0-dev.34, used by the authors). MatLab can be purchased/downloaded from: https://www.mathworks.com/products/matlab.html; EasySpin toolbox can be downloaded from: https://easyspin.org/  "Ready-to-plot", processed EPR spectra can be opened with Microsoft Excel (or an analogous open access software).