Experimental investigation of the reversible collapse of a capped amphiphile Langmuir monolayer

Haycraft, James J.; DeVries, Christine A.; Flores, Harry G García; Lech, Angelika; Hagen, James P.; Eckhardt, Craig J.

doi:10.1016/j.tsf.2006.09.014

Cited by 12 publications

(18 citation statements)

References 46 publications

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“…The reversible collapse mechanism describing the TPSE series, therefore, must include a description of amphiphile rearrangement to account for the increase in entropy with compression. This result is in agreement with the bulge amphiphile collapse mechanism proposed by Haycraft et al [5] in which they suggest an increase in disorder as the film is compressed from the close-packed monolayer to the three-dimensional post-collapse structure, as summarized below.…”

Section: Entropy Of the Reversible Collapse Transitionsupporting

confidence: 91%

“…The BAM images support this conclusion, displaying similarity among compression and expansion images and identical BAM images with subsequent isothermal cycles. Such reversible collapse Langmuir film behavior is similar to that observed by Rolandi et al [29] for a glycerol diether as well as Haycraft et al [5] for the bulge amphiphile 4BPO11. Overall, the isotherms and BAM images demonstrate that the TPSE series (and bulge amphiphiles in general) exhibit a reversible collapse mechanism.…”

Section: Tpse Series Isotherms and Bam Imagessupporting

confidence: 87%

“…Visual evidence of the Langmuir film phase behavior was obtained through Brewster angle microscopy with a HeNe laser, polarizer, focusing lens, and CCD digital video camera. The experimental instrumentation used was the same as previously described [5], with minor changes: a Millipore Direct Q-3 system was used to obtain ultrapure water (18.2 MΩ · cm resistivity); BAM images captured on VHS tapes were transferred to digital media through a Canon ZR200 Digital Video Camera; and individual frames were subsequently obtained with the iMovie program (Apple Computers) and individually processed with Adobe Photoshop Elements 5.0 software to adjust brightness and contrast to improve discrimination of features.…”

Section: Instrumentationmentioning

confidence: 99%

“…Haycraft et al name this type of molecule a bulge amphiphile and suggest its Langmuir film properties best fit the liquid-crystal model because collapse into the third dimension is reversible, with Brewster angle microscopy (BAM) images displaying bright spots ascribed to reversed cybotactic clusters, structures similar to the cybotactic clusters found for some liquid crystals at the smectic-nematic transition [6][7][8][9]. This argument is used to define the 4BPO11 monolayer as smectic-like and the final collapsed structure as a more disordered nematic-like multilayer film [5].…”

Section: Introductionmentioning

confidence: 98%

“…Haycraft et al studied benzo[c]phenanthrene-4-oxyundecanol (4BPO11), a surface-active molecule with an alcohol head group, a flexible hydrocarbon chain, and a fused-ring terminus (see Figure 1a) [5]. Haycraft et al name this type of molecule a bulge amphiphile and suggest its Langmuir film properties best fit the liquid-crystal model because collapse into the third dimension is reversible, with Brewster angle microscopy (BAM) images displaying bright spots ascribed to reversed cybotactic clusters, structures similar to the cybotactic clusters found for some liquid crystals at the smectic-nematic transition [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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Reversible collapse of the Langmuir films of a series of triphenylsilyl ether-terminated amphiphiles

et al. 2011

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Section: Entropy Of the Reversible Collapse Transitionsupporting

confidence: 91%

Section: Tpse Series Isotherms and Bam Imagessupporting

confidence: 87%

Section: Instrumentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Reversible collapse of the Langmuir films of a series of triphenylsilyl ether-terminated amphiphiles

et al. 2011

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Self‐Assembly at Different Length Scales: Polyphilic Star‐Branched Liquid Crystals and Miktoarm Star Copolymers

Ungar

Tschierske

Abetz

et al. 2011

Adv Funct Materials

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of the original manuscript:Ungar, G.; Tschierske, C.; Abetz, V.; Holyst, R.; Bates, M.A.; Lui, F.; Prehm, M.; Kieffer, R.; Zeng, X.; Walker, M.; Glettner, B.; Zywocinski, A.: Keywords: columnar liquid crystals, polygonal honeycombs, polyphiles, miktoarm star terpolymers, simulation, Langmuir films, rod-coil molecules, surface alignment Abstract: This article reviews the diversity of phase morphologies observed recently in starbranched liquid crystalline and polymeric compounds containing at least three immiscible segments. Bolaamphiphiles and facial amphiphiles with a rod-like aromatic core, two endgroups and one (T-shape) or two chains (X-shape) attached laterally to the core form numerous honeycomb-like liquid crystal phases, as well as a variety of novel lamellar and 3D-ordered mesophases. Molecular self-organization is described in bulk phases and in thin films on solid and liquid surfaces, as well as in Langmuir-Blodgett films. The remarkably reversible formation of mono-and tri-layer films is highlighted. In the bulk, T-shaped "rod-coil" molecules without the appended end-groups form predominantly lamellar phases if the core is a straight rod, but the bent-core variety forms hexagonal honeycombs. Furthermore, selfassembly of "Janus"-type molecules, such as those with Y-shaped star mesogens bearing different mutually incompatible side-groups, is discussed. Also covered is the diversity of morphologies observed in miktoarm star terpolymers i.e. polymers with three different and 3 incompatible arms of well-defined lengths. A range of bulk phases with 3D or 2D order are observed, combining layers, cylinders and cocontinuous networks. Similarities and differences are highlighted between the liquid crystal morphologies on the 3-15 nm scale and the polymer morphologies on the scale 10-100 nm. A separate section is dedicated to computer simulations of such systems, particularly those using dissipative particle and molecular dynamics. Of special interest are the recently synthesised X-shaped tetraphilic molecules, where two different and incompatible side-chains are attached at opposite sides of the rod-like core. The tendency for their phase separation produces LC honeycombs with cells of different compositions that can be represented as paving a plane with different color tiles. Self-Assembly at Different Length Scales: Polyphilic StarBranched Liquid Crystals and Miktoarm Star CopolymersThe independent variation of chain length and "color" creates the potential for developing a considerable range of complex new 2d-and 3d soft nanostructures. Analogous X-shaped rodcoil compounds with unequal side groups are also of considerable interest, forming tubular lyotropic structures capable of confining strings of guest molecules.

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Fluorescent, Synthetic Amphiphilic Heptapeptide Anion Transporters: Evidence for Self‐Assembly and Membrane Localization in Liposomes

You

Gokel

2008

Chemistry A European J

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Synthetic anion transporters (SATs) of the general type (n-C18H37)2N-COCH2OCH2CO-(Gly)3-Pro-(Gly)3-O-n-C7H15, 1, are amphiphilic peptides that form anion-conducting pores in bilayer membranes. To better understand membrane insertion, assembly and aggregation dynamics, and membrane penetration, four novel fluorescent structures were prepared for use in both aqueous buffer and phospholipid bilayers. The fluorescent residues pyrene, indole, dansyl, and NBD were incorporated into 1 to give 2, 3, 4, and 5, respectively. Assembly of peptide amphiphiles in buffer was confirmed by monitoring changes in the pyrene monomer/excimer peaks observed for 2. Solvent-dependent fluorescence changes that were observed for indole (3) and dansyl (4) side-chained SATs in bilayers showed that these residues experienced an environment between epsilon=9 (CH2Cl2) and epsilon=24 (EtOH) in polarity. Fluorescence resonance energy transfer (FRET) between 2 and 3 demonstrated aggregation of SAT monomers within the bilayer. This self-assembly led to pore formation, which was detected as Cl(-) release from the liposomes. The results of acrylamide quenching of fluorescent SATs supported membrane insertion. Studies with NBD-labeled SAT 5 showed that peptide partition into the bilayer is relatively slow. Dithionite quenching of NBD-SATs suggests that the amphiphilic peptides are primarily in the bilayer's outer leaflet. Images obtained by using a fluorescence microscope revealed membrane localization of a fluorescent SAT. Taken together, this study helps define the insertion, membrane localization, and aggregation behavior of this family of synthetic anion transporters in liposomal bilayers.

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Experimental investigation of the reversible collapse of a capped amphiphile Langmuir monolayer

Cited by 12 publications

References 46 publications

Reversible collapse of the Langmuir films of a series of triphenylsilyl ether-terminated amphiphiles

Reversible collapse of the Langmuir films of a series of triphenylsilyl ether-terminated amphiphiles

Self‐Assembly at Different Length Scales: Polyphilic Star‐Branched Liquid Crystals and Miktoarm Star Copolymers

Fluorescent, Synthetic Amphiphilic Heptapeptide Anion Transporters: Evidence for Self‐Assembly and Membrane Localization in Liposomes

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