Table 2. Fe and Mo Contents of Native and Modified Av1^a.

sample	Fe	Mo	Fe:Mo ratio
native Av1, 1	29.7 ± 0.5	1.99 ± 0.03	14.9 ± 0.5
native Av1, 2	29.7 ± 0.5	1.98 ± 0.03	15.0 ± 0.5
Av1-mod, 1	29.1 ± 0.5	1.99 ± 0.03	14.6 ± 0.5
Av1-mod, 2	29.0 ± 0.5	1.99 ± 0.04	14.6 ± 0.5

^aAv1-mod was generated at pH 9.5 by incubation of Av1 and Av2 (CR = 4.0) under turnover conditions at 30 °C for 4 h. The protein was isolated by size exclusion chromatography at pH 9.5 using the same tribuffer that was used for the inactivation. The control sample of Av1 alone was isolated by chromatography at pH 7.5. Full duplicate reactions and isolations were prepared for both proteins. The metal content was determined by ICP-MS performed in triplicate for each sample. The standard deviation for ⁵⁶Fe was ±0.56% and for ⁹⁶Mo was ±0.22%, while for the protein, the concentration varied from ±1.5 to ±1.8%. The results are normalized to the protein concentration for each individual sample and given with the standard deviation based upon multiple determinations of an individual sample.