Thermostability measurements of recombinant class I complexes using circular dichroism (CD) Circular Dichroism Spectra were measured on a Jasco 815 spectropolarimeter using a thermostatically controlled cuvette. A far-UV spectra was collected from 190nm to 250nm. The UV minimum was determined as 219 nm for H2Db-NP-N3A. The measurements for the thermal melting experiments was made at the minimum for H2Db-NP-N3A, at intervals of 0.1uC at a rate of 1uC/min from 20uC to 90uC. The Jasco Spectra Manager software was used to view and smooth the traces and then the GraphPad Prism software was used to plot Temperature versus % unfolded. The midpoint of thermal denaturation (Tm) for each protein was determined as the point at which 50% unfolding was achieved. The measurements were done in duplicate at two concentrations (4mM and 2.2mM) in a solution of 10mM Tris pH 8, 150mM NaCl.