Thermodynamics on inclusion complexation of a-cyclodextrin-based molecular tube (MT) with sodium octyl-, decyl-, and dodecylsulfonates (C-8-, C-10-, and C12SO3Na) were measured by isothermal titration calorimetry (ITC) to evaluate the effects of alkyl chain length of CnSO3Na and temperature. It was found that CnSO3Na with a longer alkyl chain formed more stable inclusion complex with MT. The association constant of inclusion complexation between MT and C12SO3Na at 298 K was found to be on the order of 10(5). The stoichiometric number ([host]/[guest] ratio) was found to be 0.50 +/- 0.05. This result indicates that one MT forms an inclusion complex with two CnSO3Na molecules, regardless of the alkyl chain length of CnSO3Na. Enthalpy-entropy compensation was also observed in MT/CnSO3Na systems, and it was confirmed that the free energy change was not affected by the change in temperature (288-308 K). From the thermodynamic parameters, it was considered that both hydrophobic interaction and van der Waals interaction were mainly contributed to inclusion complexation of MT with CnSO3Na. The large and negative entropy change (T DeltaS) attributed to the strong binding of MT was observed. The strong T DeltaS dependence on the alkyl chain length of CnSO3Na was found to be a characteristic for inclusion complexation of MT.