Hi, We are conducting a study to figure out the best amino acid mutation for increased affinity for a particular metal ion. I'm pretty novice in this field so I wanted to get suggestions as to my approach makes sense or not. I'll write a demo script (more probably python script) to substitute certain amino acids with all standard amino acids and then minimize the structure. As far as I know, Chimera can not calculate free energy, so I will save the PDB files and then use another program to calculate the free energy. My first question is, whether the commands below are appropriate for my purpose or not? The sample below is a snippet from an exhaustive list. I preferred to save the information regarding clashes before the minimization just to keep record. swapaa ala :22.a findclash :22.a log true saveFile clash_report_22ala minimize nogui true write #0 test_22ala swapaa val :22.a findclash :22.a log true saveFile clash_report_22val minimize nogui true write #0 test_22val swapaa ile :22.a findclash :22.a log true saveFile clash_report_22ile minimize nogui true write #0 test_22ile ... My second question is, when I have many PDB files, which software is suitable for calculating the free energy for each. Thanks, Assist.Prof.Dr. Alper YILMAZ Department of Bioengineering Faculty of Chemical and Metallurgical Engineering Yildiz Technical University Esenler, Istanbul/TURKEY 34210 Phone: +90.212.383-4657 (office) Fax: +90.212.383-4625