The interaction between gelatin and sodium dodecyl sulfate (SDS) is investigated by calorimetry and photometric spectrum. The conformational change in gelatin chains upon binding of SDS, the morphology development of gelatin-SDS complex, and the nature of the interaction are studied by isothermal titration calorimetry (ITC), circular dichroism (CD), fluorescence, and freeze-fracture transmission electronic microscope micrograph (FF-TEM). The results show that the exothermic binding process is driven by both electrostatic and hydrophobic interaction. The triple helix structure of gelatin is decomposed to random coil upon the binding of SDS. The morphology of complex transfers from branch-like to "necklace-and-bead". The interaction can be controlled by the concentration of SDS, the pH value of the solution, and the ionic strength of the system. (C) 2012 Elsevier Inc. All rights reserved.