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SUMMARY:Structural parameters of macroscopically flat lipid multilayers on
  a silica sol substrates
DTSTART;VALUE=DATE-TIME:20160705T072000Z
DTEND;VALUE=DATE-TIME:20160705T074000Z
DTSTAMP;VALUE=DATE-TIME:20260814T152557Z
UID:indico-contribution-1243@indico.inp.nsk.su
DESCRIPTION:Speakers: Yuriy Volkov (Shubnikov Institute of Crystallography
 \, FSRC “Crystallography and Photonics” RAS)\nA phospholipid bilayer o
 n liquid substrate can be used as the simplest model of a cell membrane [1
 ]. Previously\, the method of preparation of macroscopically flat regular 
 lipid multilayers with the use of colloidal silica hydrosols as substrates
  has been proposed [2]. Due to the specific boundary conditions at air/sol
  interface\, polar lipid molecules exhibit a spontaneous ordering effect.\
 n\nIn this report we present the investigations of influence of hydrosol c
 ompound (i.e. size of silica nanoparticles\, pH level and concentration of
  alkali ions) on the structural parameters of phospholipid layers by the X
 -ray reflectometry method with the use of synchrotron radiation. Model pho
 sphatidylcholine lipids DSPC\, DPPC and SOPC have been used as samples. Ex
 periments have been carried at X19C beamline (radiation energy E = 15 keV)
  of NSLS facility\, Brookhaven. Depth-graded distributions of electron den
 sity have been extracted from the measured reflectivity curves by the mode
 l-independent reconstruction algorithm [3].\n\nAccording to the obtained r
 esults\, overall thickness of lipid film is consistent with the Debye leng
 th for the substrate sol and thus can be varied from the monolayer (d ~ 35
  Å) to the stack of bilayers (d ~ 450 Å) at pH $\\approx$ 11.5 and 9 res
 pectively. Separate mono- and bilayers exhibit high degree of structural p
 erfection\, with calculated lipid area $A = 45 \\pm 2$ and $49 \\pm 3$ Å$
 ^2$ being in agreement with the theoretical values for 2-dimensional phosp
 holipid crystal. Enrichment of the substrate with Na$^+$ and Cs$^+$ leads 
 to the absorption of alkali ions into the lipid membrane\, with the surfac
 e concentration of ions up to $2 \\times 10^{19}$ m$^{-2}$.\n\n[1] D. M. S
 mall\, "The Physical Chemistry of Lipids"\, Plenum Press\, NY (1986).\n\n[
 2] A. M. Tikhonov\, JETP Letters\, 2010\, 92:394.\n\n[3] I. V. Kozhevnikov
 \, Nucl. Instr. Meth. Phys. Res. A\, 2003\, 508:519.\n\nhttps://indico.inp
 .nsk.su/event/3/contributions/1243/
LOCATION:Budker INP Conference Hall
URL:https://indico.inp.nsk.su/event/3/contributions/1243/
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