Behavior of rigid macromolecules in self-assembly at an interface

Abstract

Self-assembly (SA) on gold substrates of α-helical poly(γ-benzyl-L-glutamate) [(PBLG); molecular weight ∼20 000 kd] with a disulfide moiety attached at its N-terminus (PBLGSS) was investigated. The SA films were compared with control experiments using unlabeled physisorbed (PS) PBLG and Langmuir–Blodgett (LB) deposited PBLG monolayers. Characterization of the films included angle-dependent x-ray photoelectron spectroscopy, reflection–absorption Fourier transform infrared spectroscopy, ellipsometry, and contact angle measurements. For PBLGSS, a SA monolayer was formed wherein the α-helical conformation was retained and the polypeptides were preferentially bound to gold through the disulfide moiety. This terminal bond to the substrate results in a nonplanar distribution of helix axes (i.e., on average tilted up from the gold surface). This is different from the unlabeled PBLG controls, PS film and LB monolayers, wherein, respectively, less polymer was adsorbed and the helices lie in the plane of the gold substrate. Furthermore, polypeptide aggregation in the solution (e.g., in dichloromethane or 1,4-dioxane) appears to have an influence on the self-assembling behavior of these macromolecules relative to known nonaggregating solvents (N,N-dimethylformamide).

Vapor Deposition−Polymerization of α-Amino Acid N-Carboxy Anhydride on the Silicon(100) Native Oxide Surface

“…Recently, polypeptide thin films covalently grafted on solid substrates have attracted considerable attention in the interfacial polymer science community. − In particular, many attempts have been made to obtain polyglutamates (PGs), such as poly(γ-benzyl- l -glutamate) (PBLG) and poly(γ-methyl- l -glutamate) (PMLG), by grafting on solid substrates. The advantage of utilizing PGs is not only because of their liquid crystalline, amphiphilic properties but also because their ester side chain may be easily modified, which provides the flexibility to further engineer the film structure and behavior at the molecular level.…”

“…Many surface chemistry routes have been suggested for grafting the preformed PG onto the solid substrates. − However, as a result of the strong physical interaction between PG molecules and the surface, the reacted PG molecules tend to lie parallel to the surface, thus blocking other surface binding sites and hindering subsequent adsorption. Therefore, the resulting film thickness changes are small regardless of the variation of the molecular length of the adsorbed PG.…”

Protein Sensing Device with Multi-Recognition Ability Composed of Self-Organized Glycopeptide Bundle

“…The helicity of peptide in the glycopeptide bundle was estimated to be 76% from the ratio of peak intensity at 1645 cm −1 assigned to α-helical conformation to that of β-sheet (1620 cm −1 ) conformation [ 31 ], which was obtained by peak deconvolution of amide I band. The tilt angle of the α-helical axis of the peptide from the surface normal was estimated to be 7.4° from the ratio of the individual intensities of amide I to amide II absorption bands, D = A I/ A II [ 32 ].…”

“…The 1900–1300 cm −1 region of difference spectra between the glycopeptide bundle/DPPC bilayer membranes and the pure DPPC bilayer membranes were analyzed as a sum of Gaussian/Lorentzian (9:1) composition of individual bands. The tilt angle, < θ >, of the α-helical axis of the glycopeptide from the surface normal was estimated from the ratio of the individual intensities of amide I to amide II absorption bands using Equation (1), proposed by Samulski et al [ 32 ], where the angles of the transition moment (amide I and amide II) from the helix axis were supposed to be 39° and 75°, respectively, and K is a proportionality constant that related the intrinsic oscillator strengths of the amide I and amide II vibrational modes. The value of K has been calculated for a poly(L-Leu) in a KBr pellet to be 1.49.…”

Ultrathin Layers of Substituted Poly(styrene)s on Gold and Copper

“…Often, specific functional groups promote adsorption. On gold, the adsorbed amount of poly(benzyl glutamate) can be enhanced by introduction of an end group with a disulfide moiety . In addition, the affinity of polymers or copolymers based on acrylates or methacrylates can be increased by introduction of disulfide or thioether functionalities, yielding layers with 15−35 Å thickness. − Some of the resulting layers are very hydrophobic, and advancing contact angles of water above 90° were measured .…”