A comparison of the ΔC50 values concerning the in vitro stability test of human NGF Wild type and the mutants.

In order to measure the differences in stability between hNGF and the mutants after the treatments (4°C and 22°C incubation, freeze-thaw cycles, lyophilization) a comparison of the ΔC50 values was evaluated. The reference curve, corresponding to the hNGF or the mutant untreated, exhibits a ΔC50 value equal to 0, so that ΔC50 values higher than 0 indicate that the stability of the NGF sample tested was affected. The ΔC50 for the different treatments were calculated using the formula indicated in the Materials and Methods section. The errors were calculated based on the error propagation formulae. The hNGF R100E mutant exhibits in two treatments high error values (in bold). This is due to the fact that the experimental points corresponding to those treatments did not fit with the theoretical curve, causing high errors. This behavior indicates a strong destabilization of the protein (see S2 Fig).A comparison of the ΔC50 values concerning the in vitro stability test of human NGF Wild type and the mutants.