Preservation of corneous beta proteins in Mesozoic feathers

<p><strong>S-XANES data. </strong>Small samples (&ge;3 mm²) of untreated and experimentally degraded feathers in addition to fossil material and samples of host sediment were placed on low-sulfur mylar tape and analyzed at the Stanford Synchrotron Radiation Lightsource (SSRL) using synchrotron X-ray absorption near-edge spectroscopy (XANES) at beam line 6-2. S-XANES data were collected in fluorescence mode using a single element Vortex silicon drift detector set at an angle of ~90&deg; to the incident beam to minimize the scatter signal. The incident x-ray energy was selected using a Si(111) monochromator, which was calibrated using a Na₂S₂O₃standard with the thiol pre-edge peak defined as 2472.02 eV. S-XANES standards for selected S-bearing compounds, representing different S species, were prepared by mixing commercially available analytical standards (Sigma Aldrich; &ge;98% pure) with BN to obtain a S concentration of ca. 5 wt% in each standard. Data alignment, averaging, background subtraction and normalisation were performed using Athena v. 0.9.26.</p> <p>&nbsp;</p> <p><strong>FTIR data.</strong>&nbsp;Fossil data were collected in the 4000&ndash;600 cm^-1 range using a PerkinElmer Frontier FTIR spectrometer fitted with a Spotlight 400 microscope. Each spectrum was collected as an average of 8&ndash;36 scans. Spectra for untreated and matured feathers were collected in the 4000&ndash;500 cm^-1 range using a universal diamond ATR accessory on the Frontier spectrometer. Each spectrum was collected as an average of 10 scans. Each spectrum was baseline-corrected using SpectraGryph v. 1.2.7 using the parameters adaptive correction, 15% coarseness and no offset. In addition, interactive baseline correction was performed on data in the region 898&ndash;450 cm^-1 using Spectrum IR v. 10.6.1 (PerkinElmer, USA). This ensured a consistent baseline across the entire scan range to facilitate spectral comparison. Each spectrum was standardized to remove sample thickness effects.</p>