Name:

ΔHD (Tm)

Category:

Stability/Folding

Property:

Enthalpy of Unfolding (ΔH)

Units:

kJ/mol

Measurement Technique:

Circular Dichroism (CD)

Buffers:

0.1 M sodium cacodylate–HCl (pH 7.0)

Temperature:

pH:

None

Protein Concentration:

4 μM

Wavelength:

222.6 nm

Ionic Strength:

Details:

The thermodynamic parameters were derived from thermal unfolding transitions as shown in Figure 1 (see details under Tm measurement); accuracy of ΔHD is ± 5 kJ/mol.
Tm pH7.0 details: Thermal unfolding transitions of 4 μM protein in 0.1 M sodium cacodylate–HCl (pH 7.0) and different concentra- tions of NaCl were followed by circular dichroism at 222.6 nm with a 1 nm bandwidth in 10 mm cells using a Jasco J-600A spectropolarimeter equipped with a PTC-348 WI Peltier device. The data were analyzed according to a two-state model using non-linear regression and the program Grafit (Erithacus Software, Staines, UK). The heat capacity change ΔCp was held constant at 4000 J mol− 1 K− 1. The reversibility of thermal unfolding was examined by heating protein samples for 5 min at a temperature that was 10 °C above its Tm value, followed by rapid cooling to 20 °C. The subsequent thermal unfolding transitions were identical with those obtained for a sample without pre-heating.