Ptc 423s

Wavelength-dependent Circular Dichroism (CD) spectra were collected on a Jasco J-815 CD Spectrometer equipped with a PTC-423S single position Peltier temperature control system and counter-cooled with an Isotemp 3016S (Fisher Scientific) water bath. Samples were loaded in a Hellma 218 quartz cuvette (500 µL, 1 mm path length). A far-UV temperature-dependent wavelength scan from 185–260 nm as a function of temperature was completed for CE₁-His₆ and E₁C-His₆ in the absence and presence of GNPs at 0.2 mg/mL in 10 mM sodium phosphate buffer pH 8.0 at scan rate of 50 nm/min for a range of temperatures (25–90°C) with 3 accumulation scans. At least two batches of separately purified proteins were measured. CD data was converted into mean residue molar ellipticity (MRW) via equation [θ]_MRW = θ·MW/(10·n·C·l), where θ is in mdeg, MW is molecular weight, n is amino acid number in protein, C is concentration in mg/mL, l is path length in cm [35 (link)]. Fitting and calculation of protein secondary structure was processed with CDSSTR methods [36 (link)–38 (link)]. Parameters for the calculation using CDSSTR program were identical to our previously published work [31 (link)].