The Streptavidin-biotin system was based on an engineered streptavidin-biotin structure (PDBID:4JNJ) (Figure ) . Although the biological assembly of the streptavidin-biotin complex structure is a tetramer, engineered streptavidin is known to exist as a monomer . A monomeric streptavidin-biotin complex structure was simulated in this study. For the streptavidin-biotin system, CHARMM22 with CMAP and SwissParam 45 were used.