Dear all, we are wondering how the mask and unmasked values of the FSC model-map have been computed and how the mask is defined when the phenix tool phenix.validation_cryoem ("Comprenhensive Validation (cryo-EM)") is used. The motivation of this question comes from the results that we get when we have big maps (e.g. some viruses) and the atomic structure is determined only for the asymmetric subunit. We usually compute the validation considering both the whole map, and a fraction of the map that only contains the atomic structure of the asymmetric subunit (the atomic model is the same in both cases, the asymmetric subunit). We would expect the same results, as it happens for the validation statistics, but the FSC model-map values are different, especially when we talk about masked values. Recently we have checked that we have the same kind of results when we use small maps, so it doesn't seem to be due to the size of the map. Can you kindly explain the reason of these results and what we should expect in general. Is there any restriction when a fraction of the whole volume is selected? Thank you very much in advance. Regards, MARTA -- Marta Martinez Gonzalez Biocomputing Unit (Lab B13) National Center for Biotechnology-CSIC Darwin, 3. Campus de la Universidad Autonoma de Madrid 28049 Madrid. Spain Tel:+34 915854510 Fax:+34 913720112 E-mail: [email protected]