On flip-flop membrane systems with proteins

We consider once again the membrane systems with proteins on membranes. This model is bridging the membrane systems and brane calculi areas together, thus it is interesting to study it in more depth. We improve previous results in the area and also define a new variant of these systems based on time as the output of the computation. The new model allows (due to its flexibility) even stronger improvements with respect to the number of proteins needed to perform the computation.