Eiger 2 4 m detector

To determined possible effects on myofilament organization by the stone heart development, trabecular preparations were isolated from fresh control hearts and from hearts with developed stone heart condition. The muscle strips were mounted horizontally using silk thread in a temperature controlled (37°C) cuvette in MOPS buffered physiological solution (NaCl 118, KCl 5, Na₂HPO₄ 1.2, MgC₂ 1.2, CaCl₂ 1.6, glucose 10 mM, pH 7.4). The solution was gassed with air and exchanged every 5–10 min. The cuvette was equipped with Kapton windows and mounted on a stand in the CoSAXS beamline at the MAX IV synchrotron light facility, Lund, Sweden. The X-ray beam (wavelength 1 Å), had a size at the sample of about 50 × 60 μm. The sample detector distance was set to 3.5 m which gave a good resolution of the equatorial pattern using exposures of 0.5–1 s. The sample was moved between exposures to prevent beam damage. Scattering patterns were recorded using an EIGER 2 × 4 M detector (Dectris AG, Baden-Daettwil, Switzerland) and analyzed using a dedicated software. For each sample, recordings were made at different lengths (L) starting at slack length (L_s) and stretched to 1.0, 1.2, 1.3, and 1.4 L/L_s. At each length, the filament lattice spacing and intensity of the equatorial reflections were determined.

Ultra-small-angle X-ray scattering (USAXS) was performed on the ID02 beamline at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France).^{44 (link)} The X-ray wavelength was 0.1 nm and the sample-to-detector distance was fixed at 31 m to cover a q-range of about ≈0.004–0.2 nm⁻¹, where q is the scattering vector. At the sample position, the photon flux was about 1010 photons s⁻¹, and the beam size was 120 μm × 63 μm (horizontal and vertical dimensions). Scattering patterns were recorded on a flight tube-enclosed EIGER2 4M detector (Dectris) with a 0.1 s exposure time. The samples were sufficiently translated after exposure to avoid beam damage by X-ray overexposure. Several individual scales were scratched off the insect and sandwiched between two pieces of Kapton tape. Radial integration of 2D SAXS patterns was performed to obtain 1D plots. The fits were obtained with the software SasView‡‡

https://www.sasview.org/.

5.0.5 using model spheres with a Guinier form factor and an interparticle structure factor for polydisperse spherical particles interacting through hard sphere (excluded volume) interactions, employing the Percus–Yevick closure relationship. These fits yield a Gaussian distribution of the sphere diameters and their volume fraction.