NaCl , monolayer

Fig. XV-14. Surface pressure-area isotherms at 298 K for a DPPC monolayer on phos-photungstic acid (10 Af) at the pH values shown with 10 A/ NaCl added. (From Ref. 123.)...

Infrared Spectroscopy. The infrared spectroscopy of adsorbates has been studied for many years, especially for chemisorbed species (see Section XVIII-2C). In the case of physisorption, where the molecule remains intact, one is interested in how the molecular symmetry is altered on adsorption. Perhaps the conceptually simplest case is that of H2 on NaCl(lOO). Being homo-polar, Ha by itself has no allowed vibrational absorption (except for some weak collision-induced transitions) but when adsorbed, the reduced symmetry allows a vibrational spectrum to be observed. Fig. XVII-16 shows the infrared spectrum at 30 K for various degrees of monolayer coverage [96] (the adsorption is Langmuirian with half-coverage at about 10 atm). The bands labeled sf are for transitions of H2 on a smooth face and are from the 7 = 0 and J = 1 rotational states Q /fR) is assigned as a combination band. The bands labeled... 

Therefore, the following method was suggested and realized (the scheme is shown in Fig. 17). A 1.5 M solution of KCl or NaCl (the effect of preventing BR solubility of these salts is practically the same) was used as a subphase. A platinum electrode was placed in the subphase. A flat metal electrode, with an area of about 70% of the open barriered area, was placed about 1.5-2 mm above the subphase surface. A positive potential of +50 -60 V was applied to this electrode with respect to the platinum one. Then BR solution was injected with a syringe into the water subphase in dark conditions. The system was left in the same conditions for electric field-induced self-assembly of the membrane fragments for 1 hour. After this, the monolayer was compressed to 25 mN/m surface pressure and transferred onto the substrate (porous membrane). The residual salt was washed with water. The water was removed with a nitrogen jet. 

We studied the surface pressure area isotherms of PS II core complex at different concentrations of NaCl in the subphase (Fig. 2). Addition of NaCl solution greatly enhanced the stability of monolayer of PS II core complex particles at the air-water interface. The n-A curves at subphases of 100 mM and 200 mM NaCl clearly demonstrated that PS II core complexes can be compressed to a relatively high surface pressure (40mN/m), before the monolayer collapses under our experimental conditions. Moreover, the average particle size calculated from tt-A curves using the total amount of protein complex is about 320 nm. This observation agrees well with the particle size directly observed using atomic force microscopy [8], and indicates that nearly all the protein complexes stay at the water surface and form a well-structured monolayer. 

Ewing GE (2005) H2O on NaCl From Single Molecule, to Clusters, to Monolayer, to Thin Film, to Deliquescence 116 1-25... 

Fig. 2.5. p- and j-polarized vs transmittance spectra of the monolayer l2Cl[Pg.9]

Fig. 2.6. p- and -polarized vt transmittance spectra of the monolayer 12C1602/NaCl(100) at T- 80 K (C02 pressure lxlO 9 mbar, instrumental resolution 0.05 cm-1).40... 

Fig. 2.8. Monolayer transmittance spectra of the adsorbate 12C160/NaCl(100) for different temperatures. Angle of incidence 50 1°.27,28...

A theoretical treatment of the effect caused by the competition between the sine-like angular-dependent component of the adsorption potential and dipole lateral interaction demonstrated that the values 6 are the same in the ground state and at the phase transition temperature.81 Study of the structure and dynamics for the CO monolayer adsorbed on the NaCl(lOO) surface using the molecular dynamics method has also led to the inference that angles 0j are practically equalized in a wide temperature range.82 That is why the following consideration of orientational structures and excitations in a system of adsorbed molecules will imply, for the sake of simplicity, the constant value of the inclination angle ty =0(see Fig. 2.14) which is due to the adsorption potential u pj,q>j). 

We now turn to a more complex instance of the Davydov-split spectral lines corresponding to the bending vibrations of C02 molecules in a monolayer adsorbed on the NaCl(100) surface. A molecule C02 in gaseous phase exhibits two degenerate bending vibrations in the plane perpendicular to the long molecular axis. 

In Figure 2 the ir-A and AV-A plots for SODS on O.OIM NaCl sub-solutions having different pH values are shown. In all cases, phase transitions from liquid-expanded to liquid-condensed state are evident ( ). Acidification of the subsolution Increases the transition pressure but the transition is less pronounced at the lowest pH studied. This is also accompanied by an expansion of the condensed part of the curve. Small negative surface potentials are observed over most areas. The highest potential is obtained for film spread on the pH 2.2 subsolution. For small areas, the surface potential attains a positive value. This may be related to reorientation of the dipole moments of the molecules which occur once a threshold surface concentration is exceeded (O. Mlnglns and Pethlca (7) studied the monolayer properties of SODS on various sodium chloride solutions (0.1, 0.01 and O.OOIM) at 9.5 C, and they showed that the monolayer is only stable on the more concentrated salt solutions (0.1 and O.OIM). In this work, no noticeable... 

Cadmium sulfide particulate films, generated in thicknesses of 300 50 A at arachidic acid (AA) monolayer interfaces, have been characterized in situ by STM under potentiostatic control [644], Electrical contact was made between the tip of the STM, acting as the working electrode (WE), which was in contact with the CdS particulate film floating on aqueous 0.30 M NaCl, and the reference (RE) and counter (CE) electrodes, placed in the subphase (Fig. 112) [644]. A well-defined single-reduction wave at about — 1.15 V was observed. Prolonged exposure to room light shifted the reduction peak to — 0.85 V. Electrical and photoelectrical characterizations have also been performed on Ti-foil-supported, 5000-A-thick CdS particulate films in an electrochemical cell (Fig. 113) [644]. The Ti foil was used as the WE, while the RE and CE were placed into 0.50 M... 

Likewise, if surface concentrations (in weight per area) are measured as a function of it, the molecular weight of a solute that forms an insoluble monolayer may be determined. Romeo and Rosano obtained the following data for a monolayer of acetyl lipopolysac-charide on 0.2 M NaCl at 20° C ... 

Phosphatidic Acid Monolayers. Phosphatidic acid, prepared from egg lecithin by the action of phospholipase D, forms considerably more expanded monolayers than egg lecithin, presumably because of ionic repulsion between the phosphate groups in the phosphatidic acid mono-layers (42). Phosphatidic acid monolayers showed about four times more increase in surface potential when CaCl2 is substituted for NaCl in the subsolution than did egg lecithin monolayers (43). This again supports the conclusion that the trimethylammonium group competes with Ca2+ for the anionic phosphate group in egg lecithin monolayers (Figure 1A). 

Figure 8.6. Fluorescence micrographs of a monolayer of L-a-dimyristoyl phosphatidic acid containing 2.5 mM of an NBD dye on increasing the surface pressure from the point of inflection on the isotherm, a, to about half way along the two-phase region. These results were obtained at a temperature of 10.5°C at pH 11.3 over a subphase containing 1 mM NaOH, 10 pM Na2HP04, 100 mM NaCl, 2 pM CaCI2 and 1 pm EDTA. (Reproduced from Losche, M., Duwe, H.-P. and Mohwald, H. 1988 J. Colloid Interface Sci. 126 432-44 by kind permission of the publishers and authors.)...

Cell Culture. Human neuroblastoma IMR-32 (passaged through nude mice the cells were donated by Dr. Steven E. Brooks, Kingsbrook Jewish Medical Center, Brooklyn) and mouse neuroblastoma clones NIE-115, NS-20, and N-18) (donated by Dr. Shraga Makover, Hoffmann LaRoche, Inc., Nutley, New Jersey) were maintained in our laboratory as described previously (30,31). Confluent monolayers (6 to 8 x 10 cells per 250-ml Falcon plastic flask) were harvested for enzymatic studies with phosphate-buffered saline [7.0 mM potassium phosphate/0.14 M NaCl - buffer, pH 7.2 (Pi/NaCl)] containing 0.1% EDTA. 

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