Phenix: providing high quality software to the research community for crystallography and cryo-EM Knowledge of the structure of macromolecules, i.e. how the atoms are arranged in space and also how they change shape over time or in response to external factors, is necessary to understand their function. This information is also routinely exploited to aid in the development of new therapeutics. Crystallography and electron cryo-microscopy (cryo-EM) are powerful methods for determining three- dimensional macromolecular structures. Of the 160,000+ 3D structures available at the Protein Data Bank more than 150,000 have been arrived at using either crystallographic or cryo-EM methods. In both cases, the analysis of the experimental data is a computationally complex problem that relies on sophisticated software. Phenix is a software suite that uses reduced data from X-ray diffraction, electron diffraction, neutron diffraction or cryo-EM 3D reconstructions to determine macromolecular structures and has become widely used over the past 15 years. The Phenix software and associated activities such as outreach and training have become a national and international resource. Based on an analysis of publications, patents, and wwPDB depositions we observe that Phenix resource is of high impact and this is growing, as measured by increasing researcher demand and use. Phenix also plays a very significant role in supporting NIH funded research within the US. Therefore, we formally establish the Phenix Resource, which will: a) support the continued maintenance and optimization the code base to ensure that it keeps pace with current computing paradigms and scientific data standards, b) improve program usability and integration with other community software resources, c) maintain the software and hardware infrastructure for broad, efficient dissemination of the resource, and d) undertake outreach, training and user support to help grow the community of trained researchers who can make best use of the Phenix software.

Project Narrative By establishing the Phenix R24 Resource we will maintain and disseminate the Phenix software and cctbx library for crystallographic and cryo-EM structure determination. This we enable researchers to generate better, more chemically reasonable atomic models, which will help improve their fundamental understanding of biological systems. Better models will also enable scientists to develop improved therapeutics for human health.