We are happy to announce the release of ARP/wARP version 7.1. Please visit http://www.arp-warp.org for details and software download. The major implementations and improvements are: • A prototype of the molecular graphics ARP/wARP front-end, allowing the display of molecules and electron densities. • A prototype version of the new module for building poly-nucleotides (DNA or RNA). • Improved and faster protein chain tracing with higher performance at lower resolution. • The loop building as well as helix/strand building are now also inherent parts of protein model building, resulting in enhanced model completeness. • Refinement procedures during automated model building have been enhanced in the new versions of our preferred refinement engine, REFMAC, notably including the implementation of 'conditional restraints'. • Direct use of experimental single-wavelength anomalous diffraction data (SAD) during model building is now also possible. • Improved performance of automated ligand building. • Supported computer platforms are Mac powerpc, Mac Intel and Linux (including 32 and 64-bit versions and itanium).
