The binding behavior of 2-10Gly (peptides with between 2 and 10 glycine residues) to cathepsin K was investigated by molecular dynamics and docking simulations. 3Gly, 6-7Gly, and 9-10Gly was distributed on sites near the active center, although 2Gly, 4-5Gly, and 8Gly were not. The percentage of highly flexible residues was relatively lower in the distribution area of 2-10Gly, although the percentage of rigid residues was larger. Furthermore, the percentages varied significantly among the distribution areas. Delicate modification of the thermal fluctuations in proteins would enable regulation of peptide binding, and, in turn, the ability to control their functions. (C) 2015 Elsevier B.V. All rights reserved.