1 Proteins were expressed in E.coli C41 (DE3) cells with IPTG induction at 30 °C or 37 °C overnight. Histag-IMAC purification was carried out using HisTrap™ HP columns from GE Healthcare. The hexahistidine tags were then cleaved using TEV protease and proteins were purified by size exclusion chromatography on ÄKTApure purifier with GE Fraction collector F9-R, using HiLoad™ 16/600 SuperdexTM 75 pg column and eluting with 50 mM Tris buffer, pH 8. Protein-fullerene coupling Ca. 1 mg of pristine C 60 or C 60 -pyrrolidine tris-acid (C 60 A) was suspended in 1 ml of the test protein in 50 mM Tris, pH 8, and the suspension was subjected to probe-tip sonication for 20 min with 0.5 s on/off cycles at 0 °C, using Sartorius stedim biotech Labsonic ® P sonicator. Subsequently, the mixture was centrifuged in a bench top centrifuge at 21000 g for 10 min and the supernatant was purified by size exclusion chromatography on ÄKTApurifier with Frac-950 fraction collector, using Superdex™ 75 10/300 GL column, eluting with 50 mM Tris buffer, pH 8, and collecting fractions of 0.5 ml. Circular dichroism (CD) measurements CD spectra were recorded using a Jasco J-815 CD Spectrometer in a 0.1 cm path length quartz cuvette, acquired with a band-width of 1 nm at 1 nm increments and 10 s average time. Thermal denaturation was performed in a 0.1 cm path length quartz cuvette in MilliQ water or, in the case of CTPR8Y 16 -C 60 A, in 3, 4, 5 and 6 M urea solutions. The denaturation curves were monitored by following the CD signal at 222 nm wavelength as a function of temperature from 10 °C to 95 °C. Transmission electron microscopy (TEM) The samples for cryo-electron microscopy (cryo-TEM) experiments were vitrified on freshly glow-discharged (high vacuum coating system MED 020 BALTEC) holey carbon grids (Holey-carbon film on Copper 200 mesh; QUANTIFOIL R 2/2). The grids were held with ultra-thin tweezers inside the chamber of a Vitrobot Mark II (FEI Company, USA), maintained at 8 °C temperature and with relative humidity close to saturation (90% rH) to prevent drying artefacts in the blotting process. Four microliters of the sample solution were adsorbed onto the grid for 30 seconds and most of the liquid in the grid was removed by automatically blotting the grid (blot time = 3 seconds, number of blots = 1, drain time = zero and blot offset = -3 mm) with absorbent standard Vitrobot filter paper (Ø55/20mm, Grade 595, Thermo Fisher Scientific FEI) to create an "ultra-thin liquid film" (i.e., typically bellow ~100 nm film thicknesses). After the blotting, the grid was abruptly plunged into a liquid ethane bath, previously cooled with liquid nitrogen to approximately -180 °C. Vitrified grids were then removed from the plunger and stored under liquid nitrogen. High resolution zero tilt two-dimensional (2D) images were collected on a JEM-2200FS/CR (JEOL, Ltd.) field emission gun (FEG) transmission electron microscope, operated at 200 kV at liquid nitrogen temperature, using a 626 DH cryo transfer holder (Gatan Inc.). An in-column  energy filter was used to record images with improved signal to noise ratio by zero-loss filtering, with the energy slit width set at 15 eV. Digital images were recorded under lowdose conditions (on the order of 20-30 electrons/Å² per exposure) with an under-focus range from 2.0 to 5.0 m using DigitalMicrograph™ (Gatan) software with a 4K  4K Ultrascan4000™ CCD camera (Gatan Inc.). For electron tomography, a single-axis tilt series of ± 64° with 2° increments was recorded with under-focus values ranging from 5 to 8 m, using a 914 high tilt liquid nitrogen cryo transfer tomography holder (Gatan Inc.). Semiautomatic data acquisition software SerialEM 2 was used for data collection. Vitrified grids contained 10 nm gold nanoparticles for image alignment. Other conditions as described above. Computational Methods. Molecular Dynamics Simulations The parameters for the [60]fullerene species, C 60 or C 60 A, for the MD simulations were generated within the ANTECHAMBER module of AMBER 16 The charges were calculated according to the Merz-Singh-Kollman scheme 6, 7 using Gaussian 09. 8 MD simulations of CTPR8 were carried out using PDB 2HYZ as a reference, removing the crystallised samarium ion. The starting structure for the MD simulations of CTPR8Y 16 was prepared by manually introducing the abovementioned tyrosine mutations with the mutagenesis tool from PyMOL software using the CTPR8 crystal structure (PDB 2HYZ) as starting point. In all cases, i.e. CTPR8-C 60 , CTPR8-C 60 A, CTPR8Y 16 -C 60 , and CTPR8Y 16 -C 60 A simulations, [60]fullerenes were placed in arbitrary positions in the solvent region (more than 10 Å away from the protein surface and 20 Å far from other [60]fullerene molecules). In cases where more than one CTPR8Y 16 unit was included in the simulation, the proteins were separated by at least 40 Å. From these coordinates, conventional MD simulations were used to allow the fullerene molecules to diffuse freely until spontaneous association with the surface of the protein, and, finally, interaction with CTPR8 binding sites. 9