Dear sir/madam, I would like to superimpose the two structures and compute the residue wise RMSD values. With Gui support in chimera, I opened the two structures and used Matchmaker to superimpose two structures. In Matchmaker, I checked the box 'Show pairwise alignment(s)' and click Apply, subsequently it displays MultAlignViewer dialogue box, where --> Headers --> RMSD : backbone --> Save --> filenamegiven. This process would give me residue wise RMSD score only for backbone atoms in .hdr format. I wants to write python script to do the same, so that I will compare large number of structures, and my script is able to perform till the procedure of superimposition using matchmaker and display MultAlignViewer dialogue box. I don't know the way to store the RMSD : backbone and RMSD : calpha in .hdr format using python script through chimera. Can some one please help me in this. The reason why I specifically want to do in this approach is, because among the two structures, some residues of one structure is missing. Since this approach will compute RMSD only for the matching residues, I am interested in this. Hope my question is not confusing. Thanks in advance. Best regards, Kamalesh D.