Table 2.
Quantitative analysis of MalX binding toα-glucooligosaccharides.
| Ligand | UV Difference (at 20°C) |
Isothermal titration calorimetry (at 25°C) |
||||||
|---|---|---|---|---|---|---|---|---|
| Ka (μM−1) | ΔG (kcal mole−1) | n | Ka (μM−1) | ΔG(kcal mole−1) | n | ΔH(kcal mole−1) | ΔS (cal mole−1 K−1) | |
| Maltose | ~0.0005 | ~−3.6 | 1* | ND | ND | ND | ND | ND |
| Maltotriose | 1.27 (±0.20) | −8.18 (±0.09) | 0.96 (±0.02) | 0.51 (±0.06) | −7.65 (±0.07) | 0.90 (±0.01) | −6.32 (±0.23) | 4.94 (± 0.93) |
| Maltotetraose | 0.47 (±0.09) | −7.62 (±0.10) | 1.00 (±0.06) | 0.28 (±0.03) | −7.31 (±0.06) | 1.06 (±0.10) | −4.86 (±0.47) | 8.65 (±1.40) |
| Maltopentaose | 0.47 (±0.09) | −7.60 (±0.11) | 1.02 (±0.00) | 0.29 (±0.01) | −7.33 (±0.02) | 1.02 (±0.01) | −4.27 (±0.09) | 10.70 (±0.30) |
| Maltohexaose | 0.83 (±0.08) | −7.94 (±0.05) | 0.90 (±0.04) | 0.38 (±0.00) | −7.48 (±0.01) | 1.01 (±0.01) | −5.14 (±0.15) | 8.26 (±0.51) |
| Maltoheptaose | 0.83 (±0.09) | −7.94 (±0.06) | 0.91 (±0.02) | 0.38 (±0.03) | −7.47 (±0.06) | 0.97 (±0.03) | −4.48 (±0.30) | 10.49 (±1.07) |
| Maltooctaose | 0.40 (±0.06) | −7.63 (±0.08) | 0.95 (±0.04) | ND | ND | ND | ND | ND |
| Maltotetraitol | 0.005 (±0.000) | −5.12 (0.02) | 1* | ND | ND | ND | ND | ND |
*
the stoichiometry (n) was set constant at one during the non-linear regression analysis of the data.
ND, not determined.