Fourier Transform Infrared Spectra and Molecular Orientation of Black Lipid Films in Air Interacting with Metal Ions

Abstract

Polarized Fourier transform infrared spectra of black lipid films in air withdrawn from aqueous dispersions of dimyristoylphosphatidylcholine (DMPC) have been recorded at various electrolyte concentrations. The spectra revealed that monovalent cations gave little effect, whereas polyvalent cations except Mg2+ gave remarkable effects on vibrational wavenumbers of both the acyl chain and phosphate ester group of DMPC in black lipid films. In the case of Mg2+, the effect was discerned only for the phosphate ester group. By use of thin film optics, molecular orientation of DMPC in the black lipid film in air was quantitatively evaluated as a function of electrolyte concentration. In the case of monovalent and Mg2+ cations, the orientation angle of the acyl chain axes from the surface normal was little affected by the electrolyte addition. On the other hand, the other polyvalent cations caused decrease of the average orientation angle from ca. 40° to 30°. The affinity of the cations for the DMPC lipid films in air are in the order of Zn2+ > La3+ ∼ Ca2+ ∼ Pb2+ > Mg2+ > Na+ ∼ Li+.

Raman spectroscopy of model membrane monolayers of dipalmitoylphosphatidic acid at the air-water interface using surface enhancement from buoyant thin silver films

“…Studies of phospholipid films in dispersions, Langmuir layers, and Langmuir–Blodgett layers are well documented as biological membrane models 1. These assemblies have been studied by a wide range of techniques including NMR spectroscopy,2–14 X‐ray and electron diffraction,15–17 fluorescence spectroscopy,18–32 optical and spectroscopic microscopy,20, 22, 24, 33 scanning probe microscopies,34–37 and the vibrational spectroscopies FTIR,38–51 Raman,42, 52–63 and vibrational sum‐frequency generation 64–66. The vibrational spectroscopies provide much needed data about molecular structure and interactions between lipid molecules in such assemblies, particularly for the alkyl chain.…”

Effect of dye molecules on black film stability and property of aqueous core phase

“…The polar groups of the stabilizing molecules are located towards the inner aqueous core. Black films are simple and well-defined chemical systems that involve most of basic physical interactions existing in more complex structures such as biological membranes [2][3][4], therefore, they are considered to be important mimetic systems for the studies of the structure and functions of biomembranes [3][4][5][6][7][8][9]. The film stability is crucial for the studies of black films.…”

“…Work directed towards soap films of cationic surfactants is lacking due to their instability [10,11]. Liang and coworkers first introduced anionic dye, methyl orange (MO), to an aqueous solution of cationic surfactant cetyltrimethylammonium bromide (CTAB) to obtain stable black films in air and studied the films using molecular spectroscopy [12], which is one of the most powerful techniques for investigating the structure and properties of freestanding black films in air at the molecular level [3,[5][6][7][8][12][13][14][15][16][17][18][19][20][21]. In the meanwhile, the added counterionic tral axis was used to support a soap film for spectrum measurements.…”

A Neutron Reflectivity Study of Drainage and Stratification of AOT Foam Films

“…Several structural studies using X-rays have been made in the past, − with a particularly prominent contribution by Benattar et al − It appears that most experimental difficulties regarding measurements on foam films with X-rays have been overcome, making it the preferred method for structural characterization of Newton black films, but the level of detail provided by X-ray reflectivity experiments will be limited for multicomponent mixtures or complex systems, because the contrast (i.e., the electron density variation) between different components of the film is often insufficient. IR − and Raman , spectroscopic methods have also contributed valuable information about structure and organization in foam films, but these methods lack the specificity to distinguish between contributions from different components in complex multilayer structures.…”