The Molecular Simulation Grid (MoSGrid) science gateway developed on top of WS-PGRADE/gUSE targets the needs of the molecular simulation community in a virtual research environment. The existing science gateway infrastructure has been extended on several levels and layers to especially support the computing- and data-intensive research domains of quantum chemistry, molecular dynamics, and docking. On the security level, the MoSGrid project has implemented a granular security concept, which applies Security Assertion Markup Language (SAML) assertions for trust delegations. Support of the highly scalable grid middleware UNICORE has been added to the middleware layer as has the support of the object-based file system XtreemFS for distributed data management. Furthermore, developers are supported by the PortletAPI, which eases the creation of domain-specific portlets. The standardized data exchange format of Molecular Simulation Markup Language (MSML) which sets the stage for the MoSGrid metadata management features, is a main building block for the PortletAPI.