While sire started as tool for prototyping, today, it is mostly used as a molecular information and interoperability engine. Its design, discussed below, supports reading, editing, searching and writing of molecular information from a variety of molecular input file formats and software. It has a highly extensible and flexible molecular information engine, and comes with converters that interconvert the information in this engine with molecular objects from packages such as RDKit 14 , OpenMM , Gemmi , and NGLView . This empowers researchers to use the sire application programming interface (API) to, for example, load molecules from PDBx/mmCIF files via Gemmi, perform SMARTS searches via RDKit, run GPU-accelerated molecular dynamics via OpenMM, and then view the resulting molecular trajectories in the NGLView Jupyter notebook 3D molecular viewer. This functionality is used by BioSimSpace 8 , which is built directly on sire and uses sire's molecular information engine to interconvert with programs such as GROMACS , NAMD , Amber and AmberTools , for automated molecular parameterisation and running of molecular dynamics, metadynamics and free energy workflows. Current developments are now integrating machine learning potentials via tools such as emle-engine and pytorch , thereby bringing