Dear CCP4 members I have a confusion with molecular replacement. I wish to solve a monomeric protein in P21 where there are 2 monomers in asymmetric unit. I have a search model that also has 2 monomers in asymmetric unit.
First I try using Phaser. I use only one chain of the monomer model and search for 2 copies. This gives a good solution that refines with low R-factor but it shows many clashes. In other words, the 2 monomers are too close together and there are clashes where they meet. Then I try using Phaser and both chains of the model and search for 1 copy. This does not give a solution and says asymmetric unit is too full. Then I try using MolRep with the 2 chain search model. It gives solution that looks better because you can see that the 2 monomers do not physically clash but it refines very badly giving R factors of about 50% So I am confused. What am I doing wrong? Please help me with suggestions Many thanks Careina