[ccp4bb] Problem with getting Rfree and Rf down

Hi every one I have some crystals in the space group P3121. I collect 180 frames of data. My crystals do not diffract better than at most 2.0 angstrom, but the Rf barely goes below 23%, and Rfree also remains somewhere between 28-33%. I have tried to refine my data as much as I can. I do not

[ccp4bb] How to tell Refmac it is a fixed double bond?

Hi every one I have made a Cif file for the restraints of my ligand with Jligand, which is attached to my protein via a lysine-aldehyde Schiff base formation. The problem is that whenever I run the refmac with the Cif file with torsions and link description, it changes the distance of the Lysine

[ccp4bb] Crystalization in low PH

Hi everyone I have a protein that is extraordinarily stable at PH=3.0 or even 2.0. I want to crystallize it in the low PH and compare the differences between the crystals in regular PH and low PH. I was wondering how people set up the boxes in low PH, as usual buffers are mostly less acidic.

[ccp4bb] Ligand Protein Connection

Hi every one I have a problem with docking my ligand into the electron density map and make the connections ( bonds ) with the protein. It is a Lysine residue that makes a Schiff Base with a long chain aldehyde. I do not know how to make the bonds and control the torsion angles of the ligand.