Fei tecnai f20 microscope

The morphological and structural properties of the samples were investigated by TEM and High Angle Annular Dark Field- Scanning Transmission Electron Microscopy (HAADF)-STEM analyses. The TEM analyses were performed with a FEI TECNAI F20 microscope (Thermo Fisher Scientific, Milano) operating at 200 keV. The instrument was also equipped with a dispersion micro-analysis of energy (EDS) and STEM accessory. The TEM images were taken in the phase contrast mode (HREM).
The STEM pictures were recorded using HAADF detectors: in this imaging mode the intensity I was proportional to Z^1.7t, where Z is the mean atomic number and t is the thickness of the specimen.
The samples for TEM observations consisted of QD solution dropped over the TEM grid. The QD solutions were prepared by dissolving the laser-treated film deposited on a glass substrate (25 mm × 10 mm) with 240 μL of chloroform.

Gold concentration in GNR solutions was determined before and after the ligand exchange reaction by atomic absorption spectroscopy (SpectraAA 100 Varian, Agilent Technologies Inc., Santa Clara, CA, USA) using air-acetylene flame for atomization. Standard solutions at 1, 2, 5, and 10 mg L⁻¹ of atomic gold were analyzed to obtain a calibration curve. GNRs were previously digested with aqua regia at room temperature and diluted with water to achieve a gold concentration that could fit in the calibration curve.
VIS-NIR spectroscopy was performed with a Cary5000 double-beam spectrometer (Agilent Technologies Inc., Santa Clara, CA, USA) on 500 μM GNRs samples using water as a reference and scanning from 400 to 1100 nm.
Transmission Electron Microscopy was performed with an FEI TECNAI F20 microscope (Thermo Fisher Scientific, Waltham, MA, USA) operating at 200 keV after drop-casting a perforated carbon film supported by a copper grid with an aqueous dispersion of GNRs. The preparation was then dried at 100 °C.
Dynamic light scattering measurements were performed on a Malvern Zetasizer-Nano-S (Malvern Panalytical, Malvern, UK) working with a 532 nm laser beam. ζ potential measurements were conducted in DTS1060C-Clear (Malvern Panalytical, Malvern, UK) disposable zeta cells at 25 °C.

Purified Atlas G_C ectodomain trimer (3 μl at a concentration of 0.025 mg ml⁻¹) in 20 mM tris (pH 7.8), 0.15 M NaCl, 5% glycerol, and 0.5 mM TCEP was applied onto glow-discharged R1.2/1.3 400 mesh copper grids (Quantifoil Micro Tools, Germany). The grids were blotted for 4 s and plunge-frozen in liquid ethane with a Vitrobot Mark IV (Thermo Fisher Scientific) at 4°C and 100% humidity. Preliminary sample screening and initial datasets were acquired on a FEI Tecnai F20 microscope operated at 200 kV equipped with a Falcon II direct electron detector (Thermo Fisher Scientific) at −4-μm defocus. High-resolution cryo-EM dataset collection was performed on a Titan Krios microscope (Thermo Fisher Scientific) operated at 300 kV equipped with a 20 eV slit-width GIF Quantum energy–filtered Gatan K2 Summit direct electron detector in counting mode. A total of 3027 movies were recorded at a calibrated magnification of ×130,000, leading to a magnified pixel size of 1.047 Å on the specimen. Each movie comprised 36 frames with an exposure rate of 1.28 e⁻ Å⁻² per frame, with a total exposure time of 8 s and an accumulated exposure of 46.18 e⁻ Å⁻². Data acquisition was performed with the EPU software for automated data acquisition for single-particle analysis (Thermo Fisher Scientific) with three shots per hole at −1.3- to −3.5-μm defocus.