Thermal denaturation of bjFixLH as monitored by far UV-CD spectroscopy (222 nm). The apparent fraction of unfolded protein is presented at pH 9.0 (20 mM borate, 250 mM NaCl). Protein concentrations were ≤ 25 μM (heme basis, met bjFixLH, □) and ≤ 10 μM (apo bjFixLH, ●). Fits are shown by the lines, and one representative set of data is shown by the symbols.