How Is a Protein Molecule Nearsighted?

The effect range of a local change of a protein molecule is calculated using a cluster method developed in this work based on the Gaussian software. This range is found to be about 8A, which gives a concrete estimation on the ``nearsightedness'' by Kohn for protein molecules. The cluster method can be applied to calculation of the electronic density of a large molecule such as a motor protein and can provide a basis for the dynamical analysis of a single protein molecule.