Abstract:The surface pressure-area isotherm of a cysteinyl peptidolipid on a pure water subphase (pH 5.8) was compared with that on a water subphase saturated with oxygen and buffered with ammonium bicarbonate (pH 7.8). A reduction of the limiting molecular area was observed for the isotherm measured on the subphase saturated with oxygen. Hysteresis in the compression-decompression cycles of the Langmuir film was also observed. Taking into consideration the chemical structure of the peptidolipid, we rationalized that t… Show more
“…Through the use of a Langmuir trough with moveable barriers, the effect of mean molecular area on assembly can be studied. The flexibility of the monolayer system has prompted numerous studies of reactions within monolayer films that create stable polymeric films with varied two-dimensional structures and behaviors. − …”
An organo-soluble, peptide-polymer conjugate that combines poly(n-butyl acrylate) with a beta-sheet-forming peptide is spread at the water surface to investigate peptide-guided self-assembly in a two-dimensional environment. Single layers of the conjugate are studied to gain information on the packing, orientation, and structure of the conjugate molecules using standard monolayer techniques: isotherms, grazing incidence X-ray diffraction (GIXD), and infrared reflection absorption spectroscopy (IRRAS). At all conditions studied, the stabilizing beta-sheet network consists of antiparallel beta-sheets oriented parallel to the air/water interface. The incorporation of temporary switch defects in the peptide segment enables beta-sheet assembly to be triggered at different packing densities. Stable monolayers, with low compressibilities similar to peptide monolayers, form when beta-sheet assembly occurs in monolayers that contain closely packed conjugate molecules. Langmuir-Schaefer transfer of the switched monolayer seeded with 1/1000 part stearic acid results in a transferred monolayer containing ordered domains with 7 nm wide stripes, a width in agreement with the end-to-end distance of the conjugate molecule. In this interfacial system, high packing densities and a hydrophobic seed molecule play an important role in beta-sheet network and structure formation. Both effects likely direct the highly ordered beta-sheet structure because of beta-strand prealignment. Insights gained from self-assembly in this system can be applied to peptide aggregation mechanisms in more complex interfacial environments.
“…Through the use of a Langmuir trough with moveable barriers, the effect of mean molecular area on assembly can be studied. The flexibility of the monolayer system has prompted numerous studies of reactions within monolayer films that create stable polymeric films with varied two-dimensional structures and behaviors. − …”
An organo-soluble, peptide-polymer conjugate that combines poly(n-butyl acrylate) with a beta-sheet-forming peptide is spread at the water surface to investigate peptide-guided self-assembly in a two-dimensional environment. Single layers of the conjugate are studied to gain information on the packing, orientation, and structure of the conjugate molecules using standard monolayer techniques: isotherms, grazing incidence X-ray diffraction (GIXD), and infrared reflection absorption spectroscopy (IRRAS). At all conditions studied, the stabilizing beta-sheet network consists of antiparallel beta-sheets oriented parallel to the air/water interface. The incorporation of temporary switch defects in the peptide segment enables beta-sheet assembly to be triggered at different packing densities. Stable monolayers, with low compressibilities similar to peptide monolayers, form when beta-sheet assembly occurs in monolayers that contain closely packed conjugate molecules. Langmuir-Schaefer transfer of the switched monolayer seeded with 1/1000 part stearic acid results in a transferred monolayer containing ordered domains with 7 nm wide stripes, a width in agreement with the end-to-end distance of the conjugate molecule. In this interfacial system, high packing densities and a hydrophobic seed molecule play an important role in beta-sheet network and structure formation. Both effects likely direct the highly ordered beta-sheet structure because of beta-strand prealignment. Insights gained from self-assembly in this system can be applied to peptide aggregation mechanisms in more complex interfacial environments.
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