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| X-PLOR | |
|---|---|
| Name | X-PLOR |
| Developer | Yale University, Columbia University |
| Released | 1987 |
| Latest release version | (various legacy branches) |
| Operating system | Unix, Linux, macOS |
| Programming language | Fortran |
| Genre | Computational structural biology, Molecular dynamics, Crystallography |
| License | Academic / proprietary mix (historical) |
X-PLOR is a legacy computational package for macromolecular structure determination and simulation, originally developed in the late 1980s for researchers in structural biology, biophysics, and crystallography. It provided tools for crystallographic refinement, molecular dynamics, energy minimization, and simulated annealing, integrating methods used by practitioners working with protein, nucleic acid, and ligand structures. The software influenced later packages and workflows in fields spanning structural biology, computational chemistry, and bioinformatics.
X-PLOR emerged from collaborative work at Yale University and Columbia University in the 1980s, drawing on earlier programs and techniques from crystallographers and molecular modelers associated with institutions such as Brookhaven National Laboratory, Harvard University, Stanford University, Massachusetts Institute of Technology, and University of California, San Francisco. Key developers included researchers who had ties to projects like the Protein Data Bank and the development of molecular graphics systems used at Bell Labs and other centers. The package integrated ideas from predecessors such as programs developed at Brookhaven National Laboratory and methods taught at workshops at Cold Spring Harbor Laboratory, EMBO, and Gordon Research Conferences. Over time, X-PLOR was distributed to labs worldwide, used alongside software from groups at European Molecular Biology Laboratory and commercial packages produced by organizations like Schrödinger and Chemical Computing Group. Its development history intersected with advances at institutions such as NIH, Wellcome Trust, Scripps Research, and Max Planck Society.
X-PLOR bundled modules for tasks common to structural determination efforts pursued at facilities like Advanced Photon Source, Diamond Light Source, and Stanford Synchrotron Radiation Lightsource. Capabilities included restrained molecular dynamics used in protocols reminiscent of approaches described by groups at University of Cambridge and University of Oxford, energy functions influenced by parameter sets curated at IUPAC-related efforts, and refinement routines comparable to those later implemented in packages from University of California, Los Angeles and University of Washington. The package supported treatment of experimental input from diffraction experiments at beamlines operated by organizations such as Argonne National Laboratory and European Synchrotron Radiation Facility, and generated coordinate and map outputs compatible with analytical tools developed at Brookhaven National Laboratory, RCSB, and visualization programs from teams at University of California, San Diego.
Researchers at universities and institutes such as Yale University, Columbia University, Harvard Medical School, Stanford University School of Medicine, and Scripps Research Institute used X-PLOR for protein and nucleic acid structure refinement, model building in structural studies connected to projects at Protein Data Bank and validation tasks aligned with standards promoted by International Union of Crystallography. The software supported projects ranging from enzyme mechanism studies carried out at Max Planck Institute for Biochemistry and Pasteur Institute to drug-design-related modeling performed in collaboration with groups at GlaxoSmithKline, Pfizer, and academic medicinal chemistry groups at University of Oxford. It was also employed in synergy with electron microscopy efforts at EMBL-EBI and cryo-EM groups at MRC Laboratory of Molecular Biology.
X-PLOR operated primarily with coordinate and map files in formats interoperable with formats curated by Protein Data Bank, including coordinate records compatible with conventions used at Brookhaven National Laboratory and map representations analogous to density files exchanged among facilities such as European Synchrotron Radiation Facility and Advanced Light Source. Internal data structures mirrored atom lists, topology descriptions, and parameter tables similar to those maintained by consortia like IUPAC and groups affiliated with Cambridge Crystallographic Data Centre. The package read and wrote files compatible with visualization tools developed at University of California, San Diego and data repositories maintained by RCSB PDB and related archives.
X-PLOR implemented simulated annealing, restrained molecular dynamics, and least-squares refinement algorithms that reflected methodologies discussed in conferences at Gordon Research Conferences and in literature from groups at Massachusetts General Hospital and Johns Hopkins University. Force-field terms and restraint formulations were informed by parameterization work from communities around IUPAC and modeling efforts at Scripps Research, while optimization routines paralleled numerical methods championed at institutions such as Princeton University and California Institute of Technology. The package included protocols for stereochemical restraints, nonbonded interaction treatments, and density-targeted refinement that were comparable to algorithms later seen in programs from CCP4 and academic groups at UCSF.
Originally developed for academic researchers, X-PLOR’s distribution and licensing evolved through academic stewardship and collaborations with institutions like Yale University, Columbia University, and Brookhaven National Laboratory. Licensing models ranged from academic-use arrangements favored by labs at NIH to restricted commercial terms analogous to those used by vendors such as Schrödinger and Accelrys. Over time, stewardship shifted informally as code fragments and methodologies diffused into successor projects maintained by communities at EMBL-EBI, CCP4, and research groups in European and North American universities.
X-PLOR was influential in shaping practices in structural biology laboratories at institutions like Yale University, Harvard University, Stanford University, and Scripps Research Institute, informing workflows later formalized in packages from CCP4, Phenix, and REFMAC-related developments. Its methods were cited in studies emerging from organizations such as NIH, Wellcome Trust, and research collaborations with pharmaceutical firms like Merck and AstraZeneca. While superseded by newer software integrating modern force fields and graphical pipelines developed at Lawrence Berkeley National Laboratory and university consortia, X-PLOR remains part of the historical lineage of computational tools that advanced macromolecular crystallography and biomolecular simulation.
Category:Computational biology software