Table 1.
Mass spectrometry analysis of intact subunits
| Average molecular mass/μ | ||||||
| α-Chain | β-Chain | |||||
| Sample | Expected | Measured | ΔM | Expected | Measured | ΔM |
| α2Aβ2 | 15098.3 | 15098.5 ± 0.2 | 0.2 | 15867.2 | 15867.1 ± 0.5 | −0.1 |
| α2β2A | 15126.3 | 15126.6 ± 0.1 | 0.3 | 15839.1 | 15839.0 ± 0.3 | −0.1 |
| α2Aβ2A | 15098.3 | 15098.5 ± 0.2 | 0.2 | 15839.1 | 15838.9 ± 0.4 | −0.2 |
| α2AcSβ2 | 15156.3 | 15156.3 ± 0.4 | 0.0 | 15867.2 | 15867.3 ± 0.6 | 0.1 |
| α2β2AcS | 15126.3 | 15126.2 ± 0.3 | −0.1 | 15897.2 | 15897.5 ± 0.5 | 0.3 |
Average molecular masses for the intact globin chains are measured by ESI/MS in an ion trap mass spectrometer. Molecular masses were measured from the ion envelope in the charge state interval of 11+ through 20+ (see Fig. 1 ▶ for an example). Uncertainties represent the standard error of the mean (σ, n=10). δM values were calculated as expected mass subtracted from the measured value, and the expected values were calculated from the protein sequences.