Before revision:  One component is responsible for the source and sink of the folding flows (representing, respectively, the unfolded states and the native state of the protein ) , and the other  accounts for the vorticity of the flow that is produced at the boundaries of the main flow by the contact of the moving folding "fluid" with the quiescent surroundings .
After revision:  One component is responsible for the source and sink of the folding flows (representing, respectively, the unfolded states and the native state of the protein ) , and the other , which accounts for the vorticity of the flow that is produced at the boundaries of the main flow by the contact of the moving folding "fluid" with the quiescent surroundings .