X-PLOR 98.0 - NEW FEATURES AND ENHANCEMENT

Sándor Szalma, John Badger, R. Ajay Kumar and Ping Yip

Molecular Simulations Inc., 9685 Scranton Road, San Diego, CA 92121

X-PLOR 98.0 is a new release of the X-PLOR software from Molecular Simulations Inc. containing important new features for X-ray and NMR structure determination.

1. Maximum likelihood technology (Pannu & Read, Acta Cryst. A52, 659, 1996) for improved refinement of macromolecular structures against amplitude or intensity targets. A new maximum likelihood target, which incorporates phase probability distributions to make optimal use of all experimental information, is also available.
2. Andersen thermal coupling for temperature control during simulated annealing. This method of thermal coupling provides improved local conformational sampling, usually leading to lower final values of Rfree, when used on reasonably well-refined structures.
3. A new utility program for converting reflection data from a variety of arrangements to the X-PLOR format.
4. Validated scripts for structure determination using NMR distance restraints with torsion angle dynamics. Optimization of the original torsion angle dynamics code (Rice & Brünger, Proteins 19, 277, 1994) gives a speed-up of ~20% on these protocols for a ~120 amino acid structure.
5. Fast new code for Direct NOE Refinement. Matrix doubling and Gaussian quadratures methodologies (Yip, J. Biol. NMR, 3, 361, 1993) are implemented and enhanced to achieve a substantial performance improvement.
6. Methodologies for using ambiguous restraint information to perform automated iterative peak assignment and structure determination (ARIA, Nilges et al., J. Mol. Biol. 269, 408, 1997).

Graphical user interfaces to X-PLOR are provided through InsightII/Xsight 97.0 for X-ray refinement and InsightII/NMR_Refine and Felix 97.0 for NMR structure determination.