Data type: Experimental spectroscopic measurements, computer plots. Files are with filename extensions: .DSC, .DAT, .txt, .m Information on origin of the data: EPR spectroscopic measurements with filename extensions: .DSC, .DTA, .txt. EPR spectroscopic plots with filename extension: .m. CW-EPR X-band were performed on a Bruker Elexys E580 X-band spectrometer (microwave frequency 9.76 GHz) equipped with a cylindrical dielectric cavity and a helium gas-flow cryostat from Oxford Inc. The spectrum was recorded at 4.5 K and a microwave power of 1mW, a modulation amplitude of 0.7mT and a modulation frequency of 100 KHz were used. Raw and Processed Data, and Computational Protein Design files If the dataset includes multiple files that relate to each other: Files in PARACAT_WP5_20230425_CW folder includes X-band CW-EPR spectroscopic measurements, original data are in .DTA/.DSC/.txt. Files in PARACAT_WP5_20230425_MATLAB folder includes plots of the EPR measurements, data are in .m format. Information on: Specialized abbreviations: EPR – Electron Paramagnetic Resonance; CW – Continuous Wave-EPR; METP - Miniaturized Electron Transfer Protein; METPsc1 - single-chain high-potential miniaturized electron transfer protein. Definitions of variables: Magnetic field, Temperature. Units of measurement: Gauss (G), milliTesla (mT), Kelvin (K)

 Files with extension .m are MATLAB input files. MATLAB license can be acquired at the link https://it.mathworks.com/downloads/web_downloads/. To run the codes present in these files, it is necessary to install, in MATLAB, a free toolbox called EasySpin, which can be found at the link https://easyspin.org/.