TABLE 1.
IgG-binding capacity of native and DMP-cross-linked monolayers, obtained by oriented recrystallization of S-layer fusion protein rSbpA31-1068/ZZ on SCWP-coated SPR gold chips or SCWP-coated cellulose-based microbeadsa
| Parameter | Result for:
|
|||
|---|---|---|---|---|
| SPR
|
Microbeads
|
|||
| Native | DMP-treated | Native | DMP-treated | |
| Bound S-layer fusion protein | 4.3 × 10−5 nM/mm2b | 4.3 × 10−5 nM/mm2b | 620 μg/mg of microbead dry wt | 620 μg/mg of microbead dry wt |
| Bound IgG | 2.9 × 10−5 nM/mm2b | 2.8 × 10−5 nM/mm2b | 1,065 μg of IgG/mg of S-layer fusion protein | 870 μg of IgG/mg of S-layer fusion protein |
| nmol of IgG/nmol of S-layer fusion protein | 2.9/4.3 | 2.8/4.3 | 7.1/8.1 | 5.8/8.1 |
| Molar ratio (IgG/S-layer subunit) | 0.67 | 0.65 | 0.88 | 0.72 |
| No. of IgG molecules attached/morphological unit | 2.7 | 2.6 | 3.5 | 2.9 |
| nmol of IgG/mm2 | 2.9 × 10−5 | 2.8 × 10−5 | 3.4 × 10−5 | 2.8 × 10−5 |
| ng of IgG/mm2 | 4.35 | 4.20 | 5.10 | 4.20 |
| % of theoretical saturation capacity (6.5 ng/mm2) | 67 | 65 | 78 | 65 |
a
According to the center to center spacing of the morphological units of 13.1 nm, the area occupied by 1 cell unit is 171.61 nm2. Derived from this value and the molecular mass of the S-layer fusion protein of 123,000 Da, 1 mg (8.1 nmol) covers an area of 2.1 × 1017 nm2.
b
The binding capacity of the gold chip for the S-layer fusion protein and of the rSbpA31-1068/ZZ monolayer for human IgG was derived from RU values obtained by SPR measurements.