Composition and number of electrons of the different molecular components.

<p>Composition and number of electrons of the different molecular components.</p

List of all the samples prepared for this study and their molecular composition.

<p>The anionic lipid matrix was formed by a mixture of saturated DMPC and charged DMPS lipid molecules. The full length amyloid- peptide and the amyloid- segment were added at a concentration of 3 mol%. 30 mol% cholesterol and melatonin were added (separately) to study the interactions of these molecules with A peptides. denotes the position of the acyl chain correlation peak. is the corresponding hydrocarbon tail spacing. refers to the lamellar spacing, i.e., the distance between two neighboring membranes in the membrane stacks. The area per lipid for the gel state samples was determined from . Lipid areas in the fluid state can not be determined using this technique; therefore, we used a lipid area of 60.6 Å, as reported by Kučerka <i>et al.</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099124#pone.0099124-Kuerka1" target="_blank">[79]</a> for fluid DMPC membranes.</p

Parameters for the Gaussian fits to the A distributions for the melatonin-containing membrane.

<p>The number of electrons is calculated by integrating across the Gaussian peaks, and the fraction is calculated by dividing through by the total number of peptide electrons.</p

Measured and calculated electron distribution of the membrane-embedded A a) and A b) peptides and their position in the membrane.

<p>Good agreement between calculations and experiments is obtained for a position of A in the hydrocarbon membrane core. The peptide takes a slightly tilted orientation, in agreement with computer simulations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099124#pone.0099124-Tsai1" target="_blank">[85]</a>. The full length A peptide was also found to embed in anionic lipid exclude a membrane-spanning -sheet structure, as it was reported from molecular dynamics simulations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099124#pone.0099124-Strodel1" target="_blank">[82]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099124#pone.0099124-Poojari2" target="_blank">[84]</a>.</p

Reflectivity measurements for (a) DMPC/DMPS membrane, (b) DMPC/DMPS+3 mol% A, and (c) DMPC/DMPS+3 mol% A.

<p>Pronounced and equally spaced Bragg peaks were observed, which are indicative to a well ordered lamellar structure. Electron densities were calculated through Fourier transformation of the integrated peak intensities. The insets shows the function, which was used to assess the phases of the corresponding Fourier components.</p

Parameters for the Gaussian fits to the A and A distributions.

<p>The number of electrons is calculated by integrating across the Gaussian peaks, and the fraction is calculated by dividing by the total number of peptide electrons.</p

Two-dimensional data for (a) DMPC +3 DMPS membrane, (b) DMPC/DMPS+3 mol% A and (c) DMPC/DMPS+3 mol% A.

<p>The area per lipid is obtained from the position of the lipid acyl chain correlation peak at 1.5 Å⁻¹.</p

Two-dimensional X-ray scans for the a) DMPC +3 mol% DMPS +30 mol% cholesterol and b) DMPC +3 mol% DMPS 3 mol% A+30 mol% cholesterol membranes.

<p>Data were collected under full hydration of the membranes (100% RH), in their physiologically relevant fluid state.</p

Two-dimensional X-ray data for the a) DMPC/DMPS, b) DMPC/DMPS +30 mol% melatonin, and c) DMPC/DMPS +30 mol% melatonin +3 mol% A samples, with all scans done under full hydration.

<p>Corresponding reflectivities are shown in d), e) and f). The phases can be determined from the function (shown as insets to the plots) and were used to determine the electron densities plotted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099124#pone-0099124-g010" target="_blank">Figure 10</a>.</p

The materials and apparatus used for the experiment.

<p>(a) Schematic representations of DMPC, DMPS, cholesterol, melatonin, amyloid- and amyloid- molecules. (b) Diagram of the experimental setup used for the X-ray diffraction measurements. Two-dimensional data sets were collected to study molecular structure perpendicular to the solid supported membranes (out-of-plane) and parallel to the membranes (in-plane).</p