Figure 5.

Mass histograms for AAV9 measured from an ammonium acetate solution (a), 1x PBS buffer (b) or a column elution buffer (c) containing high concentrations of non-volatile solutes (~150 mM and ~300 mM, respectively). Ammonium acetate results in the highest resolution and the measured full and empty capsids are close to the theoretical values (3.72 and 4.72 MDa, respectively). Ions formed from 1x PBS buffer and column elution buffer are highly adducted, leading to mass shifts of ~120 and ~520 kDa, respectively, but the difference in mass between the empty and full capsids remains constant in all solutions, indicating that the mass of the genome contents can be accurately measured from these solutions.