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PubMed2005

Effects of processing on the structure of zein/oleic Acid films investigated by x-ray diffraction.

Zein films plasticized with oleic acid were formed by solution casting, by the stretching of moldable resins, and by blown film extrusion. The effects of the forming process on film structure were investigated by X-ray diffraction. Wide-angle X-ray scattering (WAXS) patterns showed d-spacings at 4.5 and 10 A, which were attributed to the zein alpha-helix backbone and inter-helix packing, respectively. The 4.5 A d-spacing remained stable under processing while the 10 A d-spacing varied with processing treatment. Small-angle X-ray scattering (SAXS) detected a long-range periodicity for the formed films but not for unprocessed zein, which suggests that the forming process-promoted film structure development is possibly aided by oleic acid. The SAXS d-spacing varied among the samples (130-238 A) according to zein origin and film-forming method. X-ray scattering data suggest that the zein molecular structure resists processing but the zein supramolecular arrangements in the formed films are dependent on processing methods. Structural model for a zein molecular aggregate (based on Matsushima et al.10). Rectangular prisms of individual zein molecules are hexagonally aligned parallel to each other.

Emulsifying Agents↗
PubMed1993

Pyroelectric current of oriented purple membrane films.

By applying an electric field(2 to 5.5 Volt/mm) to a suspension of purple membrane from Halobacterium halobium, oriented purple-, purple blue-, and blue-colored membrane films have been formed on conductive glasses. Pyroelectric currents have been found for these three types of oriented films at temperatures between 25 and 160 degrees C. The oriented purple-colored membrane (PM) film has positive current peaks at around 60, 80, and 115 degrees C and reverses its sign at around 130 degrees C, followed by a negative peak at 145 degrees C. (Instead of the positive peak at 80 degrees C, a negative peak has been found around 90 degrees C for purple blue- and blue-colored membrane films.) The current peak at 80 degrees C for the PM film could be due to a conformational change in the protein, which includes at least a change in the environment of the chromophore. The sign-reversal current at 130 degrees C for the PM film seems to be related to denaturation of the protein. These peak temperatures in the pyroelectric current of the PM films, i.e., 60, 80, and 115 degrees C, have been found to agree well with some characteristic temperatures observed by Shnyorov et al. (D-H exchange), Jackson et al. (DSC and absorption spectra of visible light), and Hiraki et al. (X-ray, absorption spectra).

Bacteriorhodopsins↗
PubMed1996

A Stray Field Magnetic Resonance Imaging Study of the Drying of Sodium Silicate Films.

Stray field magnetic resonance imaging (STRAFI) is shown to be highly suited to the study of drying processes in thin films. Sodium silicate films have been chosen as a model system exhibiting many of the properties of film drying in general. Films have been dried, as a function of temperature in the range 22 to 62 degrees C, down to water contents of order 28% by weight, at which stage the film is glassy. The experimental results have been quantitatively analyzed by treating the drying film as a colloidal solution. The results suggest that the localized hydrogen spin-spin relaxation time, and hence the mobility of the water in the films is independent of the drying regime and depends primarily on the local water concentration.

Journal Article↗
PubMed1998

Structural Characterization of an Octadecylamine Langmuir-Blodgett Film Adsorbed with Methyl Orange.

The adsorption characteristics of a Langmuir-Blodgett (LB) film of octadecylamine (ODA) transferred from the surface of an alkaline subphase were investigated by employing dye material of methyl orange (MO) as an adsorbate. As a result, specific adsorbability of the ODA LB film was observed, similarly to that of the LB film of long-chain quaternary alkylammonium salt. The structural characterizations of the ODA LB films before and after MO adsorption were also carried out by applying spectroscopic methods. It was found that the MO molecules took the specific molecular arrangements of edge-on orientation on the LB film and that the bilayer in the LB films had an interdigitated structure. Furthermore, the layer-layer distance of the LB film was fairly decreased by the MO adsorption, indicating the formation of another layer structure. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Polymerization of an Elaidic Acid Langmuir Film Prepared on a Terbium-Containing Subphase.

The UV-induced polymerization of an elaidic acid Langmuir film prepared on a terbium-containing subphase has been studied. The polymerization caused changes in pressure/area isotherms. The irradiated film in its more condensed state is in a liquid phase while the monomer film is in a solid phase. The dynamics of the irradiated films was investigated by following the evolution of the film area at a constant pressure. For the longer irradiation times, an expansion of the film area was observed. Scanning force microscopy and IR spectroscopy have been used to study the monolayer after its transfer onto a solid support. IR spectroscopic measurements indicated the presence of an oxygen-containing copolymer. Scanning force microscopy images revealed a modification of the structure of the film after irradiation. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Gravitational Drainage of a Tangentially-Immobile Thick Film.

We use lubrication theory to derive an evolution equation for the free surface of a draining thick free film with a zero tangential velocity component along the free surface. The films are "thick" because effects that are important in very thin films, such as intermolecular forces, do not play a role in the situation of interest. The evolution equation results from the balance of surface tension, gravity, and dynamic viscosity. Subregions of the film appear and they involve balancing these effects pairwise. Computations are performed on the full evolution equation and for various boundary conditions corresponding to different parts of the film. Matched asymptotics are developed that predict the behavior as the film enters the bath and these agree very well with the computed results. Comparison with experiment is favorable for the rate of decrease of the film thickness. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

Thickness Measurements of Thin Perfluoropolyether Polymer Films on Silicon and Amorphous-Hydrogenated Carbon with X-Ray Reflectivity, ESCA and Optical Ellipsometry.

Experimental techniques used to measure structural parameters of thin films such as thickness, density, and coverage provide important insights into the physical properties of these films. Structural parameters are also often used to predict the eventual performance of thin films. In this study, we use three different measurement techniques-X-ray reflectivity (XRR), electron spectroscopy for chemical analysis (ESCA), and optical ellipsometry-to measure the thickness of molecularly thin perfluoropolyether (PFPE) polymer films on silicon substrates and carbon overcoats. PFPE films are commonly used to lubricate surfaces in magnetic recording devices. Here, we use XRR to measure the absolute thickness of the films, which, in turn, is used to test the validity of ESCA and ellipsometry thickness measurements. Excellent agreement is found among the three methods, provided that a 25-Å electron mean-free path (MFP) is used for the PFPE film and the substrate in ESCA (single MFP model), that the bulk PFPE refractive index is used in ellipsometry, and that adventitiously adsorbed hydrocarbons are properly taken into account. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

The Molecular Spreading of Nonpolar Perfluoropolyether Films on Amorphous Carbon Surfaces.

The spreading mechanism of nonpolar perfluoropolyether films on carbon surfaces is examined in the mesoscopic regime, including both submonolayer and multilayer films. For the submonolayer film, adsorption-desorption is a main mechanism for spreading, and the surface diffusion coefficients increase as the film thickness increases. The driving force for the spreading in the submonolayer regime is the gradient of the disjoining pressure, which is described by the two-dimensional virial equation. For the multilayer film regime, the spreading characteristics are determined by the molecular weight and the disjoining pressure gradient, which is assumed to be purely van der Waals in nature. We adopt a partial slip boundary condition to analyze the multilayer film, which qualitatively explains the dependence of the surface diffusion coefficient on film thickness. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Structure Studies on Ion Coordination in 2,4-Dihydroxy-N-Octadecybenzylideneamine LB Films by UV-Vis Absorption and FTIR Spectroscopy.

The coordination reaction of Cu(2+) ions with the Schiff base amphiphile 2,4-dihydroxy-N-octadecylbenzylideneamine in ultrathin organic LB films was probed by Fourier transform infrared (FTIR) transmission spectroscopy and UV-Vis electronic absorption spectroscopy. FTIR spectral changes owing to LB films of 2,4-dihydroxy-N-octadecylbenzylideneamine contacting aqueous Cu(OAC)(2) solution suggest the formation of ion-coordination films, which is corroborated by UV-Vis absorption spectra. The coordination reaction of the annealing film at different temperatures suggests that the microstructure of LB films had an important effect on the reaction rate. Detailed analysis shows that ion-coordination films take an isotropic unaxial orientation and exhibit phase transition behavior, which is determined by the different complex structures of headgroups and of subphase and surface film. Copyright 2000 Academic Press.

Journal Article↗
PubMed2001

The Dynamics of Marangoni-Driven Local Film Drainage between Two Drops.

A study of Marangoni-driven local continuous film drainage between two drops induced by an initially nonuniform interfacial distribution of insoluble surfactant is reported. Using the lubrication approximation, a coupled system of fourth-order nonlinear partial differential equations was derived to describe the spatio-temporal evolution of the continuous film thickness and surfactant interfacial concentration. Numerical solutions of these governing equations were obtained using the Numerical Method of Lines with appropriate initial and boundary conditions. A full parametric study was undertaken to explore the effect of the viscosity ratio, background surfactant concentration, the surface Péclet number, and van der Waals interaction forces on the dynamics of the draining film for the case where surfactant is present in trace amounts. Marangoni stresses were found to cause large deformations in the liquid film: Thickening of the film at the surfactant leading edge was accompanied by rapid and severe thinning far upstream. Under certain conditions, this severe thinning leads directly to film rupture due to the influence of van der Waals forces. Time scales for rupture, promoted by Marangoni-driven local film drainage were compared with those associated with the dimpling effect, which accompanies the approach of two drops, and implications of the results of this study on drop coalescence are discussed. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

The interplay of diffusional and electrophoretic transport mechanisms of charged solutes in the liquid film surrounding charged nonporous adsorbent particles employed in finite bath adsorption systems.

A model that describes the diffusive and electrophoretic mass transport of the cation and anion species of a buffer electrolyte and of a charged adsorbate in the liquid film surrounding nonporous adsorbent particles in a finite bath adsorption system, in which adsorption of the charged adsorbate onto the charged surface of the nonporous particles occurs, is constructed and solved. The dynamic behavior of the mechanisms of this model explicitly demonstrates (a) the interplay between the diffusive and electrophoretic molar fluxes of the charged adsorbate and of the species of the buffer electrolyte in the liquid film surrounding the nonporous adsorbent particles, (b) the significant effect that the functioning of the electrical double layer has on the transport of the charged species and on the adsorption of the charged adsorbate, and (c) the substantial effect that the dynamic behavior of the surface charge density has on the functioning of the electrical double layer. It is found that at equilibrium, the value of the concentration of the charged adsorbate in the fluid layer adjacent to the surface of the adsorbent particles is significantly greater than the value of the concentration of the adsorbate in the finite bath, while, of course, the net molar flux of the charged adsorbate in the liquid film is equal to zero at equilibrium. This result is very different than that obtained from the conventional model that is currently used to describe the transport of a charged adsorbate in the liquid film for systems involving the adsorption of a charged adsorbate onto the charged surface of nonporous adsorbent particles; the conventional model (i) does not consider the existence of an electrical double layer, (ii) assumes that the transport of the charged adsorbate occurs only by diffusion in the liquid film, and (iii) causes at equilibrium the value of the charged adsorbate in the liquid layer adjacent to the surface of the particles to become equal to the value of the concentration of the charged adsorbate in the liquid of the finite bath. Furthermore, it was found that a maximum can occur in the dynamic behavior of the concentration of the adsorbate in the adsorbed phase when the value of the free molecular diffusion coefficient of the adsorbate is relatively large, because the increased magnitude of the synergistic interplay between the diffusive and electrophoretic molar fluxes of the adsorbate in the liquid film allows the adsorbate to accumulate (to be entrapped) in the liquid layer adjacent to the surface of the adsorbent particles faster than the concentrations of the electrolyte species, whose net molar fluxes are significantly hindered due to their opposing diffusive and electrophoretic molar fluxes, can adjust to account for the change in the surface charge density of the particles that arises from the adsorption of the charged adsorbate. The results presented in this work also have significant implications in finite bath adsorption systems involving the adsorption of a charged adsorbate onto the surface of the pores of charged porous adsorbent particles, because the diffusion and the electrophoretic migration of the charged solutes (cations, anions, and charged adsorbate) in the pores of the adsorbent particles will depend on the dynamic concentration profiles of the charged solutes in the liquid film surrounding the charged porous adsorbent particles. The results of the present work are also used to illustrate how the functioning of the electrical double layer could contribute to the development of inner radial humps (concentration rings) in the concentration of the adsorbate in the adsorbed phase of charged porous adsorbent particles.

Adsorption↗
PubMed2002

Organization and properties of a conjugated poly(heteroarylene methines) at the air-water interface and in the Langmuir-Blodgett films.

A poly(heteroarylene methine) derivative, poly[(2,5-thiophenediyl) (p-n-methyl, n-octylaminobenzylidene) (2,5-thiophenequinodimethaneiyl)] (PTABQ), has been synthesized and spread at the air-water interface. The influences of three kinds of solutions on PTABQ monolayer behavior at the air-water interface have been investigated via the measurements of the pi-A isotherm and film stability. The results show that all three kinds of PTABQ solutions are apt to form the stable and transferable monolayer film organized with the plane of its pi-system nearly perpendicular to the air-water interface. Moreover, the monolayer-forming ability of PTABQ can be improved by introducing a water-soluble amphiphilie as an extractable spread-aiding component, which is further proved by the AFM images and FTIR spectra of the transferred films. UV-visible absorption spectra indicate that the well-ordered layer-by-layer structure is successfully controlled in the LB films. The optical bandgap of PTABQ is reduced for the ordered arrangement of its molecules in LB films. The intrinsic electrical conductivity of PTABQ LB films is 8.1 x 10(-8) S/cm and the conductivity of iodine-doped films is 5.7 x 10(-7) S/cm.

Journal Article↗
PubMed2002

Latex film morphology and electrical potential pattern dependence on serum components: a scanning probe microscopy study.

Dry films formed by surfactant-stabilized, peroxide-initiated styrene-butyl acrylate latex were examined by atomic and electric force microscopy (AFM and EFM). The effects of latex serum components on the films were observed by subjecting the latex to extensive dialysis prior to film formation, and comparing the results to as-prepared latex. The films formed with the dialyzed latex are smoother (as evidenced by roughness and fractal dimension measurements) than the films from the as-prepared latex, but they display large electric force gradients between neighboring domains. The films made with the as-prepared latex have the highest electric uniformity, with a maximum potential variation lower than 80 mV, while this reaches 200 mV in the dialyzed latex film.

Dialysis↗
PubMed1977

Effects of neomycin on polyphosphoinositides in inner ear tissues and monomolecular films.

The effect of neomycin on polyphosphoinositides was studied in vivo and in vitro. In vivo, the incorporation of 32Pi into phosphatidylinositol phosphate and phosphatidylinositol diphosphate was measured in inner ear tissues. Concentrations of neomycin which decreased the electrophysiological response of the chochlea to sound stimulation also decreased labeling of phosphatidylinositol diphosphate. In vitro experiments with brain tissues and polyphosphoinositide extracts indicated a direct interaction between the lipids and neomycin. Neomycin interacts strongly with monomolecular films of polyphosphoinositides. The interaction appears to be complex and is a function of neomycin concentration in the subphase and surface pressure of the film. Condensation of the polyphosphoinositide film is favored at low neomycin concentrations and low film pressures while expansion of the film is favored at high neomycin concentrations and high film pressures. The interactions of neomycin with other negatively charged films (phosphatidyl inositol and phosphatidyl serine) are much weaker, particularly at low neomycin concentrations. The metabolic and physiological consequences of the neomycin/polyphosphoinositide interaction are discussed in regard to the ototoxicity of the drug.

Animals↗
PubMed1989

Impact of a television film on attitudes toward mental illness.

The possible impact of a prime time television film portraying a mentally ill killer was investigated. Groups of college students were shown the film with and without a film trailer reminding viewers that violence is not characteristic of mentally ill persons. A third group viewed a film not about mental illness. Postfilm responses to the Community Attitudes toward the Mentally Ill scale indicated that those who saw the target film expressed significantly less favorable attitudes toward mental illness and community care of mentally ill persons than did those who saw the control film, regardless of whether of not they received the trailer along with the target film. Results support concerns that media depictions add to mental illness stigma and also suggest that corrective information alone may be sufficient to counteract the stigmatizing impact of such audience-involving mass media portrayals.

Attitude↗
PubMed1981

Model film studies in enzyme histochemistry with special reference to glucose-6-phosphate dehydrogenase.

This paper deals with the progress made over the last few years in our understanding of enzyme cytochemical staining methods as studied using a fundamental approach with the aid of a model system of thin gel films. Although model films with a matrix of polyacrylamide have been mostly used, the properties and possible applications of other matrices are also reviewed. The chemical aspects of the entrapment of enzyme molecules into a matrix are summarized. Special attention has been paid in model film studies to the principles of the trapping reaction of a diffusable precursor resulting from the enzymatic conversion of a substrate. They are considered here as they concern the cytochemical demonstration of acid phosphatase activity with a lead salt. The effect of fixatives on different enzyme activities, the diffusion rate of substrates and chromogenic compounds to the enzyme site, and enzyme kinetics under cytochemical conditions are also discussed, since they are factors which influence the final results of the staining procedures. The advantage of model film studies in enabling the direct correlation of cytochemical and biochemical results is outlined with special reference to the cytochemical determination of glucose-6-phosphate dehydrogenase with Tetra Nitro BT. A method for determining enzyme activities in the soluble fraction of isolated cells after incorporation in model films is described for the first time. This method has proved to be highly appropriate for microscopical observations of glucose-6-phosphate dehydrogenase activity in single cells, because it results in a good morphology and no formazan precipitates outside the cells. On the other hand, this type of model film forms a bridge between fundamental model film studies using purified enzyme and quantitative enzyme cytochemistry performed in situ.

Acid Phosphatase↗
PubMed2000

Microstructure and dynamic surface properties of surfactant protein SP-B/dipalmitoylphosphatidylcholine interfacial films spread from lipid-protein bilayers.

Suspensions of dipalmitoylphosphatidylcholine (DPPC) bilayers containing 5, 10 or 20% (w/w) surfactant protein SP-B have been reconstituted and spread at air-liquid interfaces. Compression isotherms of DPPC/SP-B monolayers spread from these preparations were qualitatively comparable to the isotherms of the corresponding DPPC/SP-B monolayers spread from solvents. SP-B was squeezed-out at higher pressures from vesicle-spread films than from solvent-spread monolayers. SP-B caused a marked decrease on the rate of relaxation of DPPC collapse phases to equilibrium pressures in all the lipid/protein films assayed. This stabilizing effect was higher in vesicle-spread than in solvent-spread monolayers. Inclusion in the films of traces of the fluorescent probe NBD-PC (1 mol%) and use of a fluorescent derivative of SP-B labeled with a rhodamine derivative, Texas Red, allowed for direct observation of protein and lipid domains at the interface by epifluorescence microscopy. Upon compression, SP-B altered the packing of phospholipids in the bilayer-spread films, observed as a SP-B-induced reduction of the area of liquid-condensed domains, in a way similar to its effect in solvent-spread monolayers. SP-B was not associated with condensed regions of the films. Fluorescence images from vesicle-spread films showed discrete fluorescent aggregates that could be consistent with the existence of lipid-protein vesicles in close association with the monolayer. Both the retention of SP-B at higher surface pressures and the greater stability of collapse phases of DPPC/SP-B films prepared by spreading from liposomes in comparison to those spread from solvents can be interpreted as a consequence of formation of complex bilayer-monolayer interacting systems.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2005

Assembly of layer-by-layer films of heme proteins and single-walled carbon nanotubes: electrochemistry and electrocatalysis.

After being treated by mixed acids, single-walled carbon nanotubes (SWNTs) were shortened and had negatively charged groups on the surface. Positively charged hemoglobin or myoglobin at pH 5.0 was successfully assembled with SWNTs into layer-by-layer films on solid surfaces, designated as {SWNT/protein}n. While only those proteins in the first few bilayers closest to the electrode surface exhibited electroactivity, the {SWNT/protein}n films demonstrated a much higher fraction of electroactive proteins and better controllability in film construction compared with cast films of the proteins and carbon nanotubes. The proteins in the {SWNT/protein}n films retained their near-native structure at medium pH. The stable protein film electrode showed good electrocatalytic properties toward reduction of oxygen and hydrogen peroxide, demonstrating the potential application of the {SWNT/protein}n films as a new type of biosensor based on the direct electrochemistry of proteins without using mediators.

Acids↗