In the present work, the general liquid optimized boundary (GLOB) model, which is a discrete/continuum approach for molecular simulations of liquids and solutions, has been extended to include a pressure coupling algorithm based on an extended phase-space scheme. To this end, a definition of the instantaneous pressure for a microscopic system has been derived from the minimum energy principle for the Helmholtz free energy. Applications to a pure liquid, such as water, and an aqueous solution of myoglobin are presented and the results are compared to those obtained using standard periodic boundary conditions (PBC). (C) 2009 Elsevier B. V. All rights reserved.