The host-guest interactions in AlPO4-11, AlPO4-31, SAPO-34, and AlPO4-41 molecular sieves prepared using the same organic structure-directing agent, i.e., dipropylamine, are investigated by a combination of Raman, C-13 and H-1 MAS NMR, and computer modeling studies. It was found that the organic molecules trapped within the pores of these four AlPO4-based materials exist as their protonated form and adopt distinct conformations in order to fit well with the pore structure of each host. In particular, the presence of two different types of conformations of protonated dipropylamine in the circular 12-ring channels of AlPO4-31 has been ascertained.