Table I.
Overview of the Physicochemical Characteristics of Untreated (Untreated), Metal-Catalyzed Oxidized (MCO), Hydrogen Peroxide Treated (H2O2), and Guanidine Treated (Guanidine) rhIFNβ-1a
| Method | Parameter | Untreated | MCO | H2O2 | Guanidine |
|---|---|---|---|---|---|
| DLS | Z-ave (μm) | 3.2 | 1.6 | 3.9 | 0.35 |
| Z-ave with SDSa(μm) | 0.21 | 0.54 | 0.12 | 0.14 | |
| PDI | 1.0 | 1.0 | 1.0 | 0.4 | |
| PDI with SDSa | 0.5 | 0.7 | 0.5 | 0.5 | |
| UV | OD280/OD260 | 1.03 | 0.99 | 0.95 | 0.94 |
| OD280/OD260 with SDSa | 1.58 | 1.02 | 1.89 | 1.85 | |
| OD350 nm | 0.13 | 0.21 | 0.25 | 0.28 | |
| OD350 nm with SDSa | 0.01 | 0.16 | −0.01 | −0.01 | |
| HP-SECb | Monomer fraction (%) | 71 | 13 | 61 | 18 |
| Dimer fraction (%) | 14 | 8 | 10 | 42 | |
| Oligomer fraction (%) | 2 | 68 | 9 | 28 | |
| Unrecovered fraction (%) | 13 | 11 | 20 | 12 | |
| RP-HPLCc | “Native” fraction (%) | 94 | 2 | 0 | 7 |
| Oxidized fraction (%) | 0 | 0 | 63 | 0 | |
| Aggregated fraction (%) | 6 | 0 | 0 | 62 | |
| Unrecovered fraction (%) | 0 | 98 | 37 | 31 |
a0.01% (w/v) SDS was added to the rhIFNβ-1a preparations before analysis.
bFractions were calculated from the area under the curve (AUC) for each peak and an extinction coefficient 
of 1.5 for rhIFNβ-1a at λ = 280 nm (32). The range of each fraction is shown in Fig. 2
cPercentages were based on the AUC of each peak relative to the total AUC for untreated rhIFNβ-1a. The different RP-HPLC peaks are shown in Fig. 3