The next molecule we consider is the tetramine N,N'bis(3-aminopropyl)-1,3-diaminopropane, henceforth called norspermine for succinctness. Norspermine has many conformations in the gaseous phase. We choose to study two main parent conformations, as show in Figure . These conformations are a subset of a large number of possible configurations, primarily owing to the flexibility of the alkyl chains and at the amine sites. The linear conformation of the molecule is what one would obtain were they to download the coordinates from ChemSpider 45 , and so was explicitly considered here. Although one would not expect the tetramine to stay purely linear in the pore, due to energetic and geometric constraints, the nature of the bound norspermine in this conformation remains mostly linear, hence the terminology.