Dipping-Induced Azimuthal Helix Orientation in Langmuir−Blodgett Monolayers of α-Helical Amphiphilic Diblock Copolypeptides

Abstract

The azimuthal helix orientation of the rigid-rod amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and poly(gamma-methyl-L-glutamate-ran-gamma-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) in Langmuir-Blodgett (LB) monolayers was investigated using polarized transmission Fourier transform infrared spectroscopy. The relative position of dipping with respect to the previous transfer position can be used to manipulate the azimuthal orientation of the helices parallel to or tilted by an angle of 45 degrees with respect to the dipping direction in the transferred films. The study of the azimuthal order for the LB monolayers of PLGA-b-PMLGSLGs of various block lengths revealed that the observed effect arises mainly from the deformation of the PMLGSLG top brush layer, induced by the flow orientation around the transfer region. In those cases where the PMLGSLG block is tilted by a sufficiently large angle with respect to the surface normal, high azimuthal order parameters of 0.5-0.75 were obtained.

Annealing-Induced Changes in Double-Brush Langmuir−Blodgett Films of α-Helical Diblock Copolypeptides

“…In our previous study, ,, the LB monolayers of the PLGA- b -PMLGSLG diblock copolymers after deposition were determined to be uniform and exhibit the α-helical double-brush structure (Scheme ) with an average helix tilt angle (θ, Scheme ) and a preferential azimuthal helix orientation (φ, Scheme ). The average helix tilt angle between the helix axis and the surface normal (θ) can be detected both by transmission FT-IR and from the brush thickness determined by XRR .…”

Self-assembly of non-linear polymers at the air/water interface: the effect of molecular architecture

“…8). [107][108][109][110] The monolayers of these diblock copolypeptides exhibited a brush structure composed of densely packed parallel a-helices that were tilted at an angle with respect to the water surface normal (Fig. 8).…”

“…107 The influence of the dipping position relative to the previous transfer position on the azimuthal helix orientation was also investigated. 110 The dipping position can be manipulated, yielding an azimuthal alignment of a-helices in the transferred films parallel to or tilted by an angle of 45 with respect to the dipping direction. 110 In addition, the effects of annealing on the structure and helix orientation in the monolayer were also explored.…”

“…110 The dipping position can be manipulated, yielding an azimuthal alignment of a-helices in the transferred films parallel to or tilted by an angle of 45 with respect to the dipping direction. 110 In addition, the effects of annealing on the structure and helix orientation in the monolayer were also explored. 108 Upon annealing at 100 C for 24 h, a-helices became less tilted toward the surface normal, and the surface area reduced, forming more compact and uniform films.…”

Vertically Oriented α-Helical Peptides in Langmuir-Blodgett Films

“…To introduce such self-organization ability of the polypeptides into the Langmuir (L) and Langmuir-Blodgett (LB) films, various kinds of "amphiphilic peptides" (APs) have been introduced [8]. Most peptidebased L and LB films were fabricated by helical peptides designed to orient their helical axes parallel to the film plane [8], modified peptides with an alkyl chain [9][10][11] and an ionic group [12], peptides composed of the same sequences of the amino acids (AAs) to the TM domains of existing proteins [13,14], or the artificial peptides con-sisting of non-natural AAs [15].…”