Figure 5.
Soret-excited rR spectra of alkaline Cld (pH 10) and its isotopically labeled forms. Spectra were recorded with 406.7-nm excitation (15 mW). The samples were prepared in H2O, D2O, or H218O solutions buffered at pH 10.0 with 50 mM Ches. The top three traces are the original spectra whose acquisition times were identical. The bottom three traces are difference spectra that were generated by 1:1 digital subtraction. The difference bands reveal isotope shifts characteristic of HS and LS heme hydroxides.