Pfd 425s temperature controller

Temperature-dependent CD spectroscopy was performed on a JASCO J-810 spectropolarimeter equipped with a PFD-425S Jasco temperature controller (Jasco, Inc., Easton, MD) in a quartz cuvette with a 1 mm path length. Temperature-dependent fluorescence measurements were obtained on a Dual-FL spectrophotometer (Horiba Scientific, Edison, New Jersey) with a Peltier thermostat to control the cuvette temperature to within 0.1 °C. The MPX peptide was dissolved in 20 mM sodium phosphate buffer at pH 7.4 to a concentration of 75 μM either in the presence or absence of d62-DPPC lipid vesicles (1.24 mM concentration, yielding a 1:16.5 peptide-to-lipid molar ratio). Temperature-dependent equilibrium FTIR spectra were measured on a Varian 3100 Excalibur FTIR spectrophotometer equipped with a liquid nitrogen cooled mercury cadmium telluride detector. Sample and reference solutions were prepared in D₂O with matching conditions (20 mM sodium phosphate buffer, 100 mM NaCl, uncorrected pH meter reading of 7.4) but with the sample containing 1.5 mM MPX and 24 mM d62-DPPC, a 16:1 lipid:MPX ratio and loaded into a split IR cell with a 126 μm Teflon spacer between two CaF₂ windows held in a copper housing.