Thermal denaturation of the different b-lactamase variants studied in this work was studied using differential scanning calorimetry at a scan rate of 200 K/hour in HEPES 10 mM, 100 mM NaCl, pH 7 following protocols that have been previously described in detail. A single transition was observed in thermograms of heat capacity versus temperature. Denaturation temperature values correspond to the maximum of the calorimetric transition.