Table 1. Thermodynamics of binding for wild type RSL and its mutants with α-l-Me-fucoside by ITC at 293 K (standard deviations were calculated from three independent measurements).
| n | KA×106 (M−1) | KD×10−6 (M) | ΔG (kcal.mol−1) | ΔH (kcal.mol−1) | −TΔS (kcal.mol−1) | E Int (kcal.mol−1) | |
| RSL | 1.98 (±0.1) | 1.6 (±0.20) | 0.6 (±0.07) | −8.5(±0.07) | −11.1 (±0.01) | 2.7 (±0.1) | −8.85 |
| W31F | 1.97 (±0.1) | 1.1 (±0.03) | 0.9 (±0.02) | −8.3 (±0.01) | −9.9 (±0.13) | 1.7 (±0.14) | n.d. |
| W76F | 1.95 (±0.1) | 1.30 (±0.02) | 0.8 (±0.2) | −8.3 (±0.03) | −11.6 (±0.14) | 3.3 (±0.1) | n.d. |
| W31FW76F | 2.14 (±0.1) | 0.15 (±0.002) | 6.9 (±0.02) | −7.1 (±0.002) | −9.0 (±0.04) | 1.9 (±0.04) | −7.92 |
| W31AW76F | 0.92 (±0.1) | 0.08 (±0.001) | 13.1 (±0.02) | −6.7 (±0.00) | −9.2 (±0.34) | 2.6 (±0.3) | n.d. |
| W31AW76F [a] | 0.87 (±0.1) | 0.12 (±0.13) | 8.1 (±0.31) | −7.0 (±0.12) | −8.9 (±0.33) | 1.9 (±0.30) | n.d. |
| W31A | 0.91(±0.1) | 1.1(±0.03) | 0.9 (±0.02) | −8.2 (±0.01) | −9.9 (±0.34) | 1.7 (±0.10) | n.d. |
| W76A | 0.99 (±0.0) | 1.4 (±0.09) | 0.7 (±0.05) | −8.4 (±0.04) | −11.2 (±0.13) | 2.8 (±0.17) | n.d. |
| W31AW76A | 1.89 (±0.1) | 0.0011(±2E−5) | 926 (±32) | −4.1 (±0.23) | −7.8 (±0.21) | 3.7 (±0.13) | −0.91 |
The E Int represents calculated interaction energy for a specific binding site model, n stands for stochiometry. Single point alanine mutations clearly show the stoichiometry change.
[a]
fitted for two independent binding sites, parameters for W31A fixed.