Determination of the elastic constants of a polymeric Langmuir-Blodgett film by Brillouin spectroscopy

Nizzoli, F.; Hillebrands, B.; Lee, S; Stegeman, George I.; Duda, Gisela; Wegner, Gerhard; Knoll, Wolfgang

doi:10.1016/0921-5107(90)90050-l

Cited by 12 publications

(4 citation statements)

References 8 publications

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“…In recent decades, there has been an increased interest in thin films of nano-oriented structures, both in terms of fundamental science and technical applications. − A variety of different nanosized structure elements, for example, wires, rods, and tubes, have been studied. − ,,− Among others, nanorods arranged parallel to the substrate are useful for creating patterned arrays in sensor technology . The potential technological importance of ultrathin films of synthetic polypeptides has recently been highlighted from the perspective of advanced materials, for example, optical waveguides, photo- and electron-beam resists, chemical sensors, and nonlinear optics. − Synthetic, α-helix forming polypeptides may also be a viable alternative to solid nanorods, ,, considering the fact that they display a well-defined, rigid and linear structure. α-Helical peptides are therefore interesting for their collective optical, magnetic, and electronic properties. ,, Advantages of using polypeptides as nanorods are that they are easy to synthesize and have already, as peptide models, been extensively studied and characterized at the air−water interface. , In addition, α-helices have well-defined length and width.…”

Section: Introductionmentioning

confidence: 99%

Effects of pH, Ionic Strength, Calcium, and Molecular Mass on the Arrangement of Hydrophobic Peptide Helices at the Air−Water Interface

Sjögren

Ulvenlund

2004

J. Phys. Chem. B

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The influence of subphase characteristics (ionic strength, pH, and the presence of bridging cations) on the conformation and lateral orientation of the hydrophobic polypeptide poly-l-leucine (p-leu) has been investigated at the air−water interface with the surface film balance technique as well as with Brewster angle microscopy (BAM). In addition, Langmuir−Blodgett films of p-leu deposited on quartz and mica from different subphases have been studied by circular dichroism (CD) spectroscopy and atomic force microscopy (AFM). P-leu forms α-helices at the interface regardless of subphase characteristics. Long-range lateral orientation of the α-helical strands in the p-leu monolayer was obtained under conditions where attractive interpeptide end-group interactions prevail. These interactions were obtained under conditions where (1) end-group charges lend a zwitterionic character to the peptide, thus enabling strong electrostatic attraction between adjacent strands, (2) there is a possibility for formation of carboxylic acid dimers, or (3) calcium bridges form between carboxylate end groups. These three cases correspond to an increase of the effective molecular mass of the peptide. It was concluded that such an increase, and thereby an increased long-range lateral orientation, can be obtained by enabling peptide end group attraction, but not by screening peptide end group repulsion. Kinetic studies of monolayer relaxation strongly suggest that the end-group effects influence the thermodynamic, as well as the kinetic, properties of peptide monolayers.

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Section: Introductionmentioning

confidence: 99%

Effects of pH, Ionic Strength, Calcium, and Molecular Mass on the Arrangement of Hydrophobic Peptide Helices at the Air−Water Interface

Sjögren

Ulvenlund

2004

J. Phys. Chem. B

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“…Therefore, manifold investigations of the surface properties of such polymers have been undertaken in order to understand the fundamental principles of more complex systems of direct biological and pharmaceutical relevance. Many studies have been focused on the propensity of α-helices to align themselves parallel to surfaces and the implications of this phenomenon for the interfacial denaturation of proteins. − However, the surface properties of the homopolyamino acids are of relevance also for the understanding of peptide and protein adsorption. ,,− In addition, the potential technological importance of ultrathin films of synthetic polypeptides has recently been highlighted from the perspective of advanced materials, e.g., optical waveguides, photo- and electron-beam resists, chemical sensors, and nonlinear optics. − …”

Section: Introductionmentioning

confidence: 99%

Morphology and Molecular Conformation in Thin Films of Poly-γ-methyl-l-glutamate at the Air−Water Interface

et al. 2001

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The behavior of poly-γ-methyl-l-glutamate (pMeE) at the air−water interface has been studied with the surface film balance technique. In addition, Langmuir−Blodgett (LB) films of pMeE deposited on mica and quartz have been studied by atomic force microscopy (AFM) and circular and linear dichroism (CD and LD) spectroscopy. Depending on the spreading solvent, pMeE displays strikingly different compression isotherms. When spread from chloroform or trifluoroacetic acid (TFA) the surface pressure isotherms are consistent with that of a peptide in α-helix conformation. However, the latter solvent gives rise to isotherms with a considerably smaller apparent mean molecular area, A 0. When spread from pyridine, on the other hand, pMeE yields an isotherm that is expanded and inconsistent with the presence of a monolayer consisting entirely of α-helical peptides. Isotherms and AFM images strongly suggest that peptide aggregation and solvent retention are the main factors behind the isotherm differences. When the water-soluble spreading solvent TFA is used, pMeE forms discrete wormlike aggregates embedded in a monolayer matrix. In the pyridine case, aggregation in the spreading solvent and retention of pyridine in the film result in a rough aggregate network coexisting with discrete aggregates. No aggregation takes place when chloroform is used as spreading solvent. CD and LD spectra of the LB films reveal a pronounced lateral orientation of the α-helices in films spread from chloroform and TFA, while spectra of films spread from pyridine are consistent with unordered peptide strands in β-sheet conformation. In conclusion, the results show that if water-soluble and/or low-volatile solvents are used as spreading media, hydrophobic peptides cannot, a priori, be assumed to form proper monolayers.

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“…In recent years, various ␣-helical poly͑L-glutamates͒ have been studied both as LMs on water 23,25,26,[34][35][36][37] and as LB films on solid substrates. 26,34,[37][38][39][40][41][42][43][44][45][46][47][48][49] In most of these studies the primary objective has been to achieve good-quality LB films that possess technologically important properties, 50 such as lateral homogeneity, 23,45 thermal 37,44,47,49 and mechanical 45,48 stability, low defect density, 38,45 and optical anisotropy; 38,39,42 in addition, potential applications, 50,51 for example, as optical wave guides, 38,41,42 optical data storage media, 43,44 and photoresists, 37 have also been suggested. However, despite the high activity in this research area, direct structural characterizations at the intermolecular level have been limited mostly to transferred LB films, as opposed to their LM counterparts, partly due to experimental difficulties invol...…”

Section: Introductionmentioning

confidence: 99%

Structure of poly(γ-benzyl-L-glutamate) monolayers at the gas–water interface: A Brewster angle microscopy and x-ray scattering study

Fukuto

Heilmann

Pershan

et al. 1999

The Journal of Chemical Physics

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. 1999. Structure of poly(\(\gamma\)-benzyl-L-glutamate) monolayers at the gas-water interface: A Brewster angle microscopy and x-ray scattering study. Journal of Chemical Physics 111 (21) This paper reports Brewster angle microscopy ͑BAM͒, x-ray specular reflectivity ͑XR͒, grazing incidence diffraction ͑GID͒ and off-specular diffuse scattering ͑XOSDS͒ measurements of Langmuir monolayers formed on water by both mono-and polydisperse samples of ␣-helical poly͑␥-benzyl L-glutamate͒ ͑PBLG͒ as a function of area/monomer A. The microscopic behavior does not exhibit any discernible effects due to differing dispersity. At low surface densities ͑A Ͼϳ21 Å 2 /monomer, surface pressure ⌸ϭ0͒, BAM images reveal partial surface coverage by solidlike monolayer islands. GID measurements show an interhelix peak corresponding to a local parallel alignment of rodlike PBLG molecules, indicating their tendency to aggregate laterally without external pressure. Compression to AϽ21 Å 2 /monomer first leads to full and uniform surface coverage by the monolayer, followed by a steep rise in ⌸ that is accompanied by a decrease in the interhelix distance. Further compression results in a plateau of constant ⌸ in the ⌸-A isotherm ͑ϳ11.5ϽAϽϳ18.5 Å 2 /monomer, ⌸ϳ9 dyn/cm͒, which has previously been attributed to a first-order monolayer-bilayer transition. The interfacial electron density profiles determined by the XR measurements on both sides of the coexistence plateau provide direct evidence for this transition. On the basis of x-ray scattering results, the film on the high-density side of the plateau is shown to consist of a newly formed incomplete and incommensurate second layer that sits on top of and has lower average density than a homogeneous first layer. GID measurements indicate that the second layer can be characterized by larger interhelix d-spacing than the first layer, while XOSDS measurements on the bilayer suggest that the second layer is microscopically inhomogeneous. For both mono-and bilayers, the analysis of observed GID peak widths indicates that the extent of lateral positional correlations between parallel PBLG rods ranges from a few to no more than ϳ15 interhelix distances, implying short-range order.

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Determination of the elastic constants of a polymeric Langmuir-Blodgett film by Brillouin spectroscopy

Cited by 12 publications

References 8 publications

Effects of pH, Ionic Strength, Calcium, and Molecular Mass on the Arrangement of Hydrophobic Peptide Helices at the Air−Water Interface

Effects of pH, Ionic Strength, Calcium, and Molecular Mass on the Arrangement of Hydrophobic Peptide Helices at the Air−Water Interface

Morphology and Molecular Conformation in Thin Films of Poly-γ-methyl-l-glutamate at the Air−Water Interface

Structure of poly(γ-benzyl-L-glutamate) monolayers at the gas–water interface: A Brewster angle microscopy and x-ray scattering study

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