Thank you very much for you answer. My english is not very well,Because I just come from china. My major subject is gene structure,So I am not good at protein structure. But ,I think this is very useful for me to analyze protein structure and asure their structure. So,I must thank for you first! You means: If I get a homologous model structure from swissmodel which I just align with PDB stucture,i must minimize structure ,at first。 But before i do minimization,I should add water or not.so this is a question.Which condition should I add water? Secondly,I get a stable structure after minimization.If I want to do mutation, I should do minimization for every time mutation about this structure. Thank you very much! Thank you very much! BEST WISHES FOR YOU!