GROMACS 4.5 is a high-throughput and highly parallel open-source molecular simulation toolkit. It supports a wide range of biomolecules, including proteins, nucleic acids, and lipids, and includes all commonly used force fields. The software now uses multithreading for efficient parallelization on low-end systems, including Windows-based workstations. It also supports several implicit solvent models and new free-energy algorithms. GROMACS 4.5 provides extremely high performance and cost efficiency for high-throughput and massively parallel simulations. It is available as open-source software from http://www.gromacs.org. The software has been improved to support a wide range of molecular simulation tasks, including high-throughput simulation, modeling, and free-energy calculations. It also supports automated topology generation for wide classes of molecules and force fields. GROMACS 4.5 includes a range of new simulation algorithms and features, including a state-of-the-art free-energy calculation toolbox. It also supports strong scaling on massively parallel clusters and has improved performance for large systems. The software is now available on a wide range of platforms, including Microsoft Windows. GROMACS 4.5 has been optimized for performance and efficiency, and it supports a variety of computing environments, including cloud computing. The software is now used in a wide range of applications, including structural bioinformatics, molecular dynamics, and biomolecular simulations. It is also used in distributed computing projects and has been shown to scale to over 150,000 cores. GROMACS 4.5 provides a range of new features and improvements that have significantly improved both performance and efficiency for throughput as well as massively parallel applications. The software is now used in a wide range of applications, including structural bioinformatics, molecular dynamics, and biomolecular simulations. It is also used in distributed computing projects and has been shown to scale to over 150,000 cores.GROMACS 4.5 is a high-throughput and highly parallel open-source molecular simulation toolkit. It supports a wide range of biomolecules, including proteins, nucleic acids, and lipids, and includes all commonly used force fields. The software now uses multithreading for efficient parallelization on low-end systems, including Windows-based workstations. It also supports several implicit solvent models and new free-energy algorithms. GROMACS 4.5 provides extremely high performance and cost efficiency for high-throughput and massively parallel simulations. It is available as open-source software from http://www.gromacs.org. The software has been improved to support a wide range of molecular simulation tasks, including high-throughput simulation, modeling, and free-energy calculations. It also supports automated topology generation for wide classes of molecules and force fields. GROMACS 4.5 includes a range of new simulation algorithms and features, including a state-of-the-art free-energy calculation toolbox. It also supports strong scaling on massively parallel clusters and has improved performance for large systems. The software is now available on a wide range of platforms, including Microsoft Windows. GROMACS 4.5 has been optimized for performance and efficiency, and it supports a variety of computing environments, including cloud computing. The software is now used in a wide range of applications, including structural bioinformatics, molecular dynamics, and biomolecular simulations. It is also used in distributed computing projects and has been shown to scale to over 150,000 cores. GROMACS 4.5 provides a range of new features and improvements that have significantly improved both performance and efficiency for throughput as well as massively parallel applications. The software is now used in a wide range of applications, including structural bioinformatics, molecular dynamics, and biomolecular simulations. It is also used in distributed computing projects and has been shown to scale to over 150,000 cores.