I've tried several ways to get an Rfree flag into my mtz file...converting from a CNS to mtz (with existing flags) and scalepack to mtz and etc etc...with the same result, i.e. that the "bin number" that the reflection is in (0-19) is put in mtz file as the Rfree flag and not 0 or 1. I was wondering if this has to do with array size or something. This is a 1.42A dataset with 125982 reflections. In addition, I am trying to get refmac to recognize a 5MC as a DNA base with proper links in the backbone etc...what is the best way to do this? ------------------------------------------------------------------------------------------------------------------ John R. Horton, Ph.D. Assistant Professor (Research) E- mail: [log in to unmask] Emory University School of Medicine Voice- mail: 404-727-8492 Department of Biochemistry FAX: 404-727-3746 Rollins Research Center, Suite G239 1510 Clifton Road Atlanta, GA 30322 ------------------------------------------------------------------------------------------------------------------