Paramagnetism-based restraints for Xplor-NIH

Modules that use paramagnetism-based NMR restraints have been developed and integrated in the well known program for solution structure determinationXplor-NIH; the complete set of such modules is called PARArestraints for Xplor-NIH. Paramagnetism-based restraints are paramagnetic relaxation enhancements, pseudocontact shifts, residual dipolar couplings due to metal and overall magnetic anisotropy, and cross correlation between Curie relaxation and nuclear-nuclear dipolar relaxation. The complete program has been tested by back-calculatingNOEs and paramagnetism-based restraints from the X-ray structure of cytochrome c553 from B. pasteurii. Furthermore, the same experimental restraints previously used to determine the solution structure of cytochrome c553 itself, of cytochrome b5, and of calbindin D9k with the program PARAMAGNETIC DYANA, have been used for structure calculations by using PARArestraints for Xplor-NIH. The agreement between the two programs is quite satisfactory and validates both protocols.