sentence: Crystal structures of the X. laevis nucleosome with Widom 601 sequence11 ( PDB code 3LZ0 ) , the S. cerevisiae Chd1 DNA-binding domains13 ( PDB code 3TED ) , and S. cerevisiae Chd1 core12 ( double chromodomain and ATPase motor , PDB code 3MWY ) were placed into the electron density using UCSF Chimera44 .