Distributions of alkyl chain tilt angle θ of various glycolipids for one layer.

<p>Shows the current results for 160<i>β</i>Mal-C₁₂, black for <i>β</i>BCMal-C₁₂C₁₀ (<i>sn-1</i>), deep sky blue for <i>β</i>BCMal-C₁₂C₁₀(<i>sn-2</i>), green for <i>β</i>Cel-C₁₂ and dark blue for <i>β</i>IsoMal-C₁₂.</p

Fractional <i>gauche</i> population in, <i>P</i>(<i>gauche</i>), for dihedral angles between carbons in the alkyl chains.

<p>The dihedral angle label, for example C71–C74 represent C71–C72–C73–C4 following alkyl chain numbering in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101110#pone-0101110-g001" target="_blank">Figure 1</a>. (a) <i>β</i>Mal-C₁₂, (b) <i>β</i>Cel-C₁₂, (c) <i>β</i>IsoMal-C₁₂, (d) <i>β</i>BCMal-C₁₂C₁₀(<i>sn-1</i>), and (e) <i>β</i>BCMal-C₁₂C₁₀(<i>sn-2</i>). First lipid layer (□), second layer (×), third layer (+), and fourth layer (*).</p

Some lipids' conformations and bilayer snapshots from the simulation.

<p>(a) Three possible lipid conformations with the chain tilt angle, θ of 24° and 156°. (b) The dispersion interaction observed from two viewing angles, between the C–H from the sugar face and those of the alkyl chain by a representative lipid (enlarged) from the third layer. (c) A characteristic example of the sugar headgroup region (t = 140 ns) from the third leaflet showing the hydrophobic cavity (top-view). (d) The time evolution of a typical side-view of the second and third leaflets. The lipid (drawn fully with VDW model) is seen to work itself into the hydrophilic region.</p

Correlation times as a function of each C–H vector along lipid alkyl chains are shown.

<p>The labeling of carbon atoms follows the naming convention as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101110#pone-0101110-g001" target="_blank">Figure 1</a>. (a) shows the correlation times for monoalkylated glycolipids, <i>β</i>Mal-C₁₂ (<b>+</b>), <i>β</i>Cel-C₁₂ (<b>×</b>), and <i>β</i>IsoMal-C₁₂ (*). (b) and (c) show correlation times for chains <i>sn-1</i> and <i>sn-2</i> respectively for <i>β</i>BCMal-C₁₂C₁₀.</p

Radial distribution function for three carbon atoms along the alkyl chain for monoalkylated lipids: (a) βMal-C₁₂ (b) βCel-C₁₂ and (c) βIsoMal-C₁₂.

<p>Radial distribution function for three carbon atoms along the alkyl chain for monoalkylated lipids: (a) βMal-C₁₂ (b) βCel-C₁₂ and (c) βIsoMal-C₁₂.</p

Average correlation time of sugar headgroup of lipids: reducing sugar (<i>ring1</i>); non-reducing sugar <i>(ring2)</i>; and combination of <i>ring1</i> and <i>ring2</i> (<i>ring12</i>).

<p>Average correlation time of sugar headgroup of lipids: reducing sugar (<i>ring1</i>); non-reducing sugar <i>(ring2)</i>; and combination of <i>ring1</i> and <i>ring2</i> (<i>ring12</i>).</p

Glycosides used in the simulation: (a) <i>β</i>Mal-C₁₂ (b) <i>β</i>Cel-C₁₂ and (c) <i>β</i>IsoMal-C₁₂ (d) <i>β</i>BCMal-C₁₂C₁₀.

<p>Starting from glycosidic oxygen, each glycolipid's main alkyl chain (<i>sn-1</i>) is labeled from C71 to C82 and the branched chain (<i>sn-2</i>) from C83 to C92. Here, for clarity we have reduced the atoms' labels on the sugar, a slight modification from the standard nomenclature according to IUPAC given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101110#pone-0101110-g001" target="_blank">Figure 1</a> of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101110#pone.0101110-ManickamAchari1" target="_blank">[22]</a>.</p

Snapshot of chain vectors between midpoints of C71–C72 and C80–C81 for monoalkylated lipids and chain <i>sn-1</i>.

<p>For chain <i>sn-2</i>, the vector is defined between midpoints of C71–C72 and C90–C91.</p

Self-Assembly, Thermotropic, and Lyotropic Phase Behavior of Guerbet Branched-Chain Maltosides

Five synthetic β-d-maltosides derived from Guerbet branched alcohols, whose total hydrocarbon chain length ranged from C₈ to C₂₄, were synthesized to a high anomeric purity, and their thermal properties, liquid-crystalline phases, and structures were characterized using differential scanning calorimetry, optical polarizing microscopy, and small-angle X-ray scattering. Thermal investigations of all anhydrous Guerbet maltosides showed that they do not form solid crystals but undergo a glass transition upon temperature change in the range of 35–53 °C. The glassy crystalline structure turns into the liquid-crystalline structure upon heating or addition of water. In thermotropic studies, the lamellar phase formation is prominent in shorter-chain-length analogues, whereas the longer-chain compounds exhibit a more frustrated form of self-assembly in the formation of a metastable state, polymorphism, and inverse bicontinuous cubic structure (<i>Ia</i>3<i>d</i>). The excess water conditions show that the phase formation is dominated by the lamellar phase for the longer-chain compounds. Normal micellar solution was observed in the shortest-chain-length maltosides because of the enlargement of hydrated maltose headgroups. The self-assembly of both dry and fully hydrated Guerbet maltosides, which exhibited glass-forming abilities and showed surface activity and also the ability to act as membrane-stabilizing compounds, makes them ideal candidates for practical use in industry as well as biomedical research

Molecular Dynamics Study of Anhydrous Lamellar Structures of Synthetic Glycolipids: Effects of Chain Branching and Disaccharide Headgroup

Glycolipids form materials of considerable potential for a wide range of surfactant and thin film applications. Understanding the effect of glycolipid covalent structure on the properties of their thermotropic and lyotropic assemblies is a key step toward rational design of new glycolipid-based materials. Here, we perform molecular dynamics simulations of anhydrous bilayers of dodecyl β-maltoside, dodecyl β-cellobioside, dodecyl <i>β-</i>isomaltoside, and a C₁₂C₁₀ branched β-maltoside. Specifically, we examine the consequences of chain branching and headgroup identity on the structure and dynamics of the lamellar assemblies. Chain branching of the glycolipid leads to measurable differences in the dimensions and interactions of the lamellar assembly, as well as a more fluid-like hydrophobic chain region. Substitution of the maltosyl headgroup of βMal-C₁₂ by an isomaltosyl moiety leads to a significant decrease in bilayer spacing as well as a markedly altered pattern of inter-headgroup hydrogen bonding. The distinctive simulated structures of the two regioisomers provide insight into the difference of ∼90 °C in their observed clearing temperatures. For all four simulated glycolipid systems, with the exception of the <i>sn-</i>2 chain of the branched maltoside, the alkyl chains are ordered and exhibit a distinct tilt, consistent with recent crystallographic analysis of a branched chain Guerbet glycoside. These insights into structure–property relationships from simulation provide an important molecular basis for future design of synthetic glycolipid materials