FIGURE 11.

Relative Raman intensities for Mfp-2 with different admixtures of iron. No added Fe³⁺ (bottom) and with Fe³⁺ added at DOPA:iron ratios of 20:1 (middle) and 2:1 (top). Fe³⁺ was added to Mfp-2 at pH 5.5, after which the protein-iron complex was precipitated by raising the pH to 8. Tris-DOPA-iron complexes (as shown) are detected primarily by the ring and -O-iron resonances indicated (arrows). Excitation laser was at 532 nm. Inset spectrum shows actual intensities normalized to CH band (2850–3010 cm⁻¹) to emphasize the Raman enhancement by resonance. a.u., arbitrary units.