Cdf 426s peltier unit

Circular Dichroism experiments were performed in 10 mM Tris-SO₄ pH 7.0 with 2 mM CaSO₄ buffer. Samples were analyzed on a J-815 Circular Dichroism Spectrometer (Jasco) using a 1 mm path-length Spectrosil quartz cuvette (Starna Scientific). The temperature was controlled using a CDF-426S Peltier unit (Jasco). Far-UV CD spectra were obtained by incubating 0.15 mg/mL protein at 10 °C, before ramping at 12 °C/min to 55, 75 or 90 °C. Samples were held at that temperature for 3 minutes before starting a read (the “During heating” trace). The scanning speed of the instrument was set to 50 nm/min and scans were performed from 260 to 185 nm. After the read, samples were cooled to 10 °C. Samples were kept at 10 °C for 3 minutes before taking another read (the “After cooling” trace). Four scans were recorded from each independent sample, the recorded spectra were averaged, and then subtracted by the averaged baseline spectrum (buffer alone). Spectra were smoothened using the Savitzky-Golay method44 on the SpectraManager 2 software (Jasco). Ellipticity was converted to molar ellipticity using the SpectraManager 2 software.

The spectra were recorded on a JASCO J-810 spectropolarimeter with the CDF-426S Peltier unit using a quartz cuvette of 0.2 cm optical path length teflon stopper. The peptide was dissolved in sodium phosphate buffer pH 7.4. Solutions of 50, 25, 10 and 5 μM of peptides were prepared in aqueous buffer alone or in the presence of 30% of trifluoroethanol. The measurement was obtained between 190 and 260 nm with a data pitch of 0.2 nm, a band width of 1 nm and scanning speed of 0.8 nm/min for four accumulations. All spectra were corrected by subtracting the buffer spectrum. The circular dichroism (CD) data were expressed as molar ellipticity [θ] (deg.cm².dmol⁻¹) calculated by [θ_MR] = 100θ/C_MR × l, where θ is the ellipticity in mdeg, C_MR is the molar concentration divided by the number of residues, and l is the path length of the cell in cm.