NTBI as a function of the volume of serum added to the test wells.

Aliquots of serum from 2 thalassemics (N.A. and M.M.) and a healthy individual (Control) were serially diluted in HBS containing 10 mg/mL BSA, and assayed for NTBI as described in “Materials and methods” and in Figure 2. Depicted on the abscissa is the volume of the aliquot of original serum in the 100-μL sample applied to each well. The fluorescence intensity obtained for each sample is indicated on the right scale in terms of raw fluorescence units (descending scale). The fluorescence units were converted to iron concentrations (IC, in μmol/L), using the calibration curve depicted in Figure 2B and then to pmol/well by multiplying IC by the volume of original serum in each well. Negative values are due to chelation of contaminant iron in the assay reagent by serum transferrin. Bars indicate standard deviation of the mean of 4 individual samples.