The embedded CCP4 Monomer Library subset grows from 62 to 84 compounds:
- the modified tRNA/rRNA nucleotides PSU, 5MC, 1MA, OMG, OMC, OMU, H2U, M2G, 7MG, 2MG, 5MU (RNA group,
joined by the library's backbone link "p");
- the cofactors NAD, NAI, NAP, NDP, FAD, FMN, HEM, HEC, SAM, SAH, and dioxygen (OXY). CMO is left out:
its dictionary has C-O at 1.25 A, where bound CO is near 1.15 A.
links_and_mods.cif gains the links these compounds use: HEC-CYS1/HEC-CYS2 (heme C thioethers),
CYS-HEMB/CYS-HEMC, CYS-FAD and HIS-FAD1/2, with their modifications.
AddMetalLinks now takes a metal atom of any residue, not only a one-atom ion, so a heme iron's LINK records
to His NE2 / Met SD / water become bonds at the library's metal-site distances; the site's coordination counts
the metal's bonds in its own dictionary (a heme's four pyrrole N) as well as the records. A metal within a
ligand is also a metal for the repulsions (1.9 A to N, O, S) and its dictionary bonds are kept with the metal
bonds. Note HEC.cif's own Fe-N(pyrrole) ideal is 1.90 A (HEM: 2.04 A), so a cytochrome c reports a metal-bond
rmsd near 0.1 A.
Test RefinementRestraints_deposited_ligands builds the topology of eleven deposited models cut down to the
ligand and its surroundings (tests/test_data/ligands, 66 KB, from PDB 1EHZ, 8BKH, 6K9I, 2W3V, 5VML, 6F3P,
8CON, 3TK0, 7TCD, 6W4H, 5EPE): every ligand restrained, bond rmsd < 0.03 A, the RNA backbone bonded to each
modified nucleotide, the heme Fe-His bonds, and the HEC thioethers. rugnux --mode refine on the full entries
against their deposited structure factors: R-free within +-0.003 of the build where these were held fixed,
ligand bond rmsd vs the dictionary from 0.004-0.058 A down to 0.002-0.042 A. rugnux grows by 425 KiB.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu
(cherry picked from commit f4d407c8de6cb462320edb21a70665350e436d28)
leonarski_f
00662c4110