  The modeling of complex reaction-diffusion processes in, for instance,
cellular biochemical networks or self-assembling soft matter can be
tremendously sped up by employing a multiscale algorithm which combines the
mesoscopic Green's Function Reaction Dynamics (GFRD) method with explicit
stochastic Brownian, Langevin, or deterministic Molecular Dynamics to treat
reactants at the microscopic scale [A. Vijaykumar, P.G. Bolhuis and P.R. ten
Wolde, J. Chem. Phys. {\bf 43}, 21: 214102 (2015)]. Here we extend this
multiscale BD-GFRD approach to include the orientational dynamics that is
crucial to describe the anisotropic interactions often prevalent in
biomolecular systems. We illustrate the novel algorithm using a simple patchy
particle model. After validation of the algorithm we discuss its performance.
The rotational BD-GFRD multiscale method will open up the possibility for large
scale simulations of e.g. protein signalling networks.
