The structures of monolayers and multilayers of poly-1-benzyl-L-histidine (PBLH)-stearic acid (StA) mixtures have been investigated. The force-area (FA) curves of the monolayer had a plateau region which can be attributed to a transition from the liquid to the solid phase rather than that from a monolayer to a bilayer, as reported for α-helical polypeptides such as poly-γ-benzyl-L-glutamate. The cyclic FA curve measurements, i.e. the cycles of compression and successive expansion of the monolayer, showed that the structural change in the monolayer from the liquid to the solid phase was practically reversible. The FA curves of the mixed monolayer showed a strong dependence on the cation species in the subphase. The mixed multilayers prepared by a horizontal lifting method gave X-ray diffraction patterns which suggested that they had a Y-type structure, despite the fact that this method would lead one to expect the formation of an X-type structure. Studies on the relationship between the UV absorption spectra of the Langmuir-Blodgett films and the surface pressure for deposition suggested that a change in the orientation of PBLH chromophores occured at the plateau region in the FA curves.
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