in 3 mM NaAzide
                                  The protein solution was in a buffer
                                  containing 25 mM NaCl, 100 mM NaMES/MES
                                  buffer, pH 7.5, 3 mM NaAzide
                                        in 3 mM NaAzide. Buffer components were mixed
                                  to produce a pH of 4.7 according to a ratio
                                  calculated from the pKa. The actual pH of
                                  solution 2 was not measured.