LTBP-1 Interaction with Fibrillin Microfibrils

Full-length human LTBP-1 was purified as previously described^{56 (link)} and incubated with bovine fibrillin microfibrils at a 2:1 molar ratio for 4 h at 4 °C. The complex was adhered for 60 s to 400-mesh carbon-coated grids then washed with Milli-Q water three times and dried. The sample was visualized in STEM mode with a Fischione high-angle annular dark-field detector on an FEI Tecnai 12 Twin TEM at 34,000× magnification. A camera length of 350 cm was used to give an angular collection range of 20–100 mrad. Tobacco mosaic virus was used as a calibration standard for mass per unit length. The electron dose was kept sufficiently low (<300 e nm⁻¹) to produce negligible mass loss. Mass per unit length measurements and axial mass distributions were measured from STEM annular dark-field images using the Semper6 image analysis software (Synoptics).