The reaction kinetics of fluoride and ammonia with acid and alkaline ferrimyoglobin in a crystalline state.

Differences between the reactivity of amorphous and crystalline myoglobin have been studied by the rapid-flow method combined with dual-wavelength spectrophotometry. The binding of ammonia to the hydroxide compound has a half-time of 55 ms. The reverse reaction has a half-time of 70 ms. At pH 7.0 the relative half-times of combination and dissociation with fluoride are 10 min for crystalline and 1.8 min for amorphous materials. Reactivity of the crystals to fluoride at pH 6.0 greatly increased as compared with pH 8.7. Half-time at pH 8.7 is 10 min, while at pH 6.0 the half-time is 2.5 s for the crystalline material and 1.4 s for the amorphous material. The exchange of fluoride by azide at pH 6.0 is 3.1-fold faster in amorphous material than in crystalline material.