All binding free energies are positive and increase with the number of water molecules in the cluster. This entails that the clusters become increasingly more thermodynamically unfavorable and thus increasingly unstable in the gas-phase when adding more water molecules. This is most pronounced for the (PA) 1 (w) 0-5 clusters as they are observed to be close to or even higher in free energy compared to the pure gas-phase water clusters. The higher free energy is caused by the internal H-bond present in the PA monomer. Hence, to form clusters with water, PA needs to break the internal H-bond, which thereby does not lead to a gain in free energy.