ScrewFit

ScrewFit is an Open Source program for the characterization of protein secondary structures. It provides an efficient description of structural motifs based on simple geometrical assumptions.

The algorithm implemented in ScrewFit determines the orientational distances of consecutive peptide planes using quaternion-based superposition fits combined with the Chasles' Theorem. This approach permits to describe structural elements in terms of screw motions parameters and local-helices.
Reference: Kneller, G.R., Calligari, P. Acta Crystallographica , D62, 302-311 --> link.

Current Release

The current release 0.9.2 of ScrewFit is under active development and it has been tested only on Linux and MacOS X 10.4 machines.

Downloading and Installing ScrewFit

ScrewFit is developed in Python and uses some modules from the Molecular Modelling Toolkit (MMTK) which implements the Chasles' Theorem and permits an easier interface with crystallographic data and the PDB file formats.

All Linux distributions and MacOS X 10.4

  tar xzf ScrewFit-X.X.X.tar.gz
  cd ScrewFit
  python setup.py install

Please see the list of prerequisites below. Python itself is part of all modern Linux distributions.
Numerical Python is provided as an optional package with most Linux versions (usually called python-numeric).

Prerequisites

The actual release of ScrewFit relies on several other software packages, which must be installed before ScrewFit itself:

• the Python interpreter (for MacOS X: MacPython 2.5 or later)
• the netCDF library
• Numerical Python (for MacOS X: release 23.8 or later)
• Scientific Python (for MacOS X: release 2.5.1 or later)
• MMTK (for MacOS X: release 2.5.14 or later)