The affinity of small ligands including O2, Xe, NO, CO, H 2S, and H2O to myoglobin is studied based on the Three-dimensional Reference Interaction Site Model (3D-RISM) theory, the statistical mechanics of molecular liquids. The affinity is evaluated in terms of the coordination number of ligands in cavities in the protein, or the "Xe site," which can be obtained from the radial distribution function of ligand molecules inside the cavities. It is found that NO, CO, and H 2S show greater affinity to the Xe sites than O2 does, while the affinity of Xe is lower than that of O2. A relevance of the results to the physiological activity of the protein is speculated. The physical origin of the difference in affinity among the ligands is discussed.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Materials Chemistry