Figure 2. Wild type and E107A mutant differ very little in their surface exposure of apolar residues and in their structural stability. A: Intrinsic fluorescence of wild-type and E107A mutant HGDC. The protein concentrations used were 10 μM (0.2 mg/ml) in MOPS buffer, pH 7.3, cell path length 2 mm, and spectra were recorded at room temperature, using an excitation wavelength of 295 nm, with 2.5 nm slits. B: Guanidinium chloride–induced denaturation of wild-type and E107A HGDC. The relative emission intensity of the 360 nm band (of the denatured form) was compared to that of the 320 nm band (of the native protein) and monitored as a function of denaturant concentration.