The Molecular Modelling Toolkit (MMTK) is an open-source software package written in Python, which performs common tasks in molecular modelling. , MMTK consists of about 18,000 lines of Python code, 12,000 lines of hand-written C code, and some machine-generated C code. Features construction of molecular systems, with special support for proteins and nucleic acids infinite systems or periodic boundary conditions (orthorhombic elementary cells) common geometrical operations on coordinates rigid-body fits visualization using external PDB and VRML viewers; animation of dynamics trajectories and normal modes the AMBER 94 force field, with several options for handling electrostatic interactions a deformation force field for fast normal mode calculations on proteins energy minimization (steepest descent and conjugate gradient) molecular dynamics (with optional thermostat, barostat, and distance constraints) normal mode analysis trajectory operations point charge fits molecular surface calculations interfaces to other programs See also Software for molecular mechanics modelling References External links Background information Molecular modelling software Molecular dynamics software Python (programming language) software