Kinetics of the formation of a phospholipid multilayer on a silica sol surface

Abstract

The ordering of a multilayer consisting of DSPC bilayers on a silica sol substrate is studied within the model-independent approach to the reconstruction of profiles of the electron density from X-ray reflectometry data. It is found that the electroporation of bilayers in the field of anion silica nanoparticles significantly accelerates the process of their saturation with Na + and H2O, which explains both a relatively small time of formation of the structure of the multilayer of (1 − 7) × 10 5 s and 13% excess of the electron density in it.

X-ray study of the structure of phospholipid monolayers on the water surface

“…Such a design of the instrument allows X-ray reflectometry studies of liquid samples. The possibility of studying the structure of phospholipid multilayers deposited on a liquid silica sol substrate with this instrument was demonstrated in our works [9,10]. However, it is noteworthy that the formation of phospholipid monolayers and their structure on the water surface (which possibly better simulates biological membranes) differ from those studied in our previous works.…”

“…DMPS phospholipid monolayer samples were prepared and studied at room temperature T ≈ 298 K in an air-tight cell with X-ray transparent windows according to the method described in [10,11]. A calibrated volume of the phospholipid solution in chloroform-methanol 5 : 1 mixture was deposited by means of a microsyringe on the surface of the liquid substrate (KCl solution in deionized water at pH≈ 7) placed in a Teflon dish with the diameter D = 100 mm.…”

Model-Independent X-Ray Scattering Study of a Silica Sol Surface

“…The polarizability profile δ(z) thus obtained unambiguously specifies the electron density distribution along the Oz axis ρ(z) ≈ 2πδ(z)/(r0λ 2 ) [22]. Using this approach, we previously studied the structure and formation kinetics of macroscopically flat lipid membranes on the hydrosol surface [23][24][25].…”

Study of DMPS Monolayers on a Water Substrate with Laboratory X-ray Reflectometer

“…The information about the surface structure in our experiment is averaged over a large illumination area A0 ≈ 0.5 cm 2 and, therefore, the structure of the near-surface layer of our samples may be considered in the approximation of an ideal layerinhomogeneous structure [19]. The electron density profile across the surface, ρ(z), was reconstructed from the reflectometry data by invoking two different approaches.…”

“…The deviation from a strict power law is apparently attributable to the scattering by sample surface roughnesses with an effective height σ. Its value can be estimated within the Nevot-Croce formalism from the requirements imposed on the asymptotics R(qz)q 6 z exp σ 2 qz q 2 z − 4k 2 0 δ+ → const when qz → ∞, where δ+ ≈ 7.5 × 10 6 is the water polarizability for λ ≈ 1.54 Å [19,35]. Thus, we obtain σ ≈ 3.2 Å, which agrees well with the calculated value of σ0 ≈ 3 Å given above.…”