Pitfalls in Sample Preparation of Metalloproteins for Low-Temperature EPR: The Example of Alkaline Myoglobin

<strong>Description of the dataset: </strong> <strong>Data type</strong>: Experimental spectroscopic measurements (EPR and UV-vis), computer simulations and data analysis Files are with filename extensions: <strong>DSC</strong>, <strong>DTA</strong>, <strong>m</strong>, <strong>mat</strong>, <strong>ods</strong>,<strong> tif</strong> Information on <strong>origin of the data</strong>: EPR spectroscopic measurements have filename extensions <strong>DSC</strong> and <strong>DTA</strong> EPR spectroscopic simulation and analyses with filename extension <strong>m</strong> UV-vis spectroscopic measurements have filename extensions <strong>ods</strong> Processed data ready for simulation/figure preparation have filename extension <strong>mat </strong>(both for EPR and UV-vis) High-quality figures published in main text and supplementary are provided as <strong>tif</strong> files CW-EPR measurements were generated with a Bruker ELEXSYS E580 X-band spectrometer equipped either with an Oxford CF935 continuous flow cryostat and a Bruker ER4118 SPT-N1 resonator or with an Oxford ESR 900 continuous-flow cryostat and a Bruker ER 4122 SHQ resonator. Pulse EPR experiments were performed with an Oxford CF935 continuous flow cryostat and a Bruker ER4118 SPT-N1 resonator. Simulations of EPR spectra and fitting were performed with the Easyspin software (v. 6.0.0-dev.26) implemented in Matlab (MathWorks, R2020b) <strong>The dataset</strong>Files with extension <strong>m</strong> normally recall files with extension <strong>mat</strong> which should be stored in the same working folder Files in <strong>PARACAT_WP3_20210929_01_CW</strong> folder include subfolders organised by topic: “Alternative cryoprotectants” contains: ready-to-plot / ready-to-simulate data in <strong>mat</strong> format; simulation scripts in <strong>m</strong> format. “Glycerol effects - different buffers” contains: ready-to-plot / ready-to-simulate data in <strong>mat</strong> format; simulation scripts in <strong>m</strong> format. Files in <strong>PARACAT_WP3_20210929_02_PULSE</strong> folder include pulse EPR spectroscopic measurements; original data are in <strong>DSC</strong> and <strong>DTA</strong> formats; processed data and fitting are in <strong>m</strong> format. Files in <strong>m</strong> format recall original data files, therefore they should be stored in the same working folder. Files in <strong>PARACAT_WP3_20210929_03_UV-VIS</strong> folder include UV-vis spectroscopic measurements; original and basic processed data are in <strong>ods</strong> format; ready-to-plot data are in <strong>mat</strong> format; scripts for figure preparation are in <strong>m</strong> format. Files in <strong>PARACAT_WP3_20210929_04_FIGURES</strong> folder include high-quality figures published in main text and supplementary, provided as <strong>tif</strong> files <strong>Information on</strong>: <strong>Specialized abbreviations:</strong> <strong>EPR</strong> – Electron Paramagnetic Resonance, <strong>CW</strong> – Continuous Wave EPR, <strong><em>T_m</em></strong> or <strong><em>T₂</em></strong>– phase memory time, <strong>CAPS</strong> - N-cyclohexyl-3-aminopropanesulfonic acid, <strong>CHES</strong> - N-Cyclohexyl-2-aminoethanesulfonic acid <strong>Definitions of variables:</strong> magnetic field (<strong>mT</strong> - milliTesla), pH (pH units), UV-vis absorbance intensity (<strong>A.U.</strong> – arbitrary units), EPR intensity (<strong>A.U.</strong> – arbitrary units), Hahn Echo Intensity (<strong>A.U.</strong> – arbitrary units), <em>g</em>-values (adimensional) <strong>Units of measurements:</strong> Concentration: <strong>mM</strong> (millimolar), <strong>µM</strong> (micromolar), <strong>% v/v</strong> (percentage volume/volume) Volume: <strong>mL</strong> (milliliters), <strong>µL</strong> (microliters) Wavelength: <strong>nm</strong> (nanometers) Temperature: <strong>°C</strong> (Celsius degrees), <strong>K</strong> (Kelvin degrees) Time: <strong>ns</strong> (nanoseconds) Frequency: <strong>GHz</strong> (gigahertz) Power: <strong>mW</strong> (milliwatt)