Structure of mono-acid even-numbered β-triacylglycerols

Generation of frustrated liquid crystal phases by mixing an achiral nematic-smectic-C mesogen with an antiferroelectric chiral smectic liquid crystal J. Chem. Phys. 122, 144906 (2005) Suspensions of platelet-like shaped tripalmitin nanocrystals stabilized by the pure lecithin DLPC and the lecithin blend S100, respectively, have been studied by small-angle x-ray scattering (SAXS) and optical observation of their birefringence at different tripalmitin (PPP) concentrations ϕ PPP . It could be demonstrated that the platelets of these potential drug delivery systems start to form a liquid crystalline phase already at pharmaceutically relevant concentrations ϕ PPP of less than 10 wt. %. The details of this liquid crystalline phase are described here for the first time. As in a previous study [A. Illing et al., Pharm. Res. 21, 592 (2004)] some platelets are found to self-assemble into lamellar stacks above a critical tripalmitin concentration ϕ st P P P of 4 wt. %. In this study another critical concentration ϕ lc P P P ≈ 7 wt. % for DLPC and ϕ lc P P P ≈ 9 wt. % for S100 stabilized dispersions, respectively, has been observed. ϕ lc P P P describes the transition from a phase of randomly oriented stacked lamellae and remaining non-assembled individual platelets to a phase in which the stacks and nonassembled platelets exhibit an overall preferred orientation. A careful analysis of the experimental data indicates that for concentrations above ϕ lc P P P the stacked lamellae start to coalesce to rather small liquid crystalline domains of nematically ordered stacks. These liquid crystalline domains can be individually very differently oriented but possess an overall preferred orientation over macroscopic length scales which becomes successively more expressed when further increasing ϕ PPP . The lower critical concentration for the formation of liquid crystalline domains of the DLPC-stabilized suspension compared to ϕ lc P P P of the S100-stabilized suspension can be explained by a larger aspect ratio of the corresponding tripalmitin platelets. A geometrical model based on the excluded volumes of individual platelets and stacked lamellae has been developed and successfully applied to reproduce the critical volume fractions for both, the onset of stack formation and the appearance of the liquid crystalline phase.

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“…The triclinic unit cell parameters of β-tripalmitin and the atomic positions of the tripalmitin molecules are taken from Ref. 33.…”

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confidence: 99%

Formation of liquid crystalline phases in aqueous suspensions of platelet-like tripalmitin nanoparticles

Schmiele

Gehrer

Westermann

et al. 2014

The Journal of Chemical Physics

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“…In the s-range between 0.12 and 0.34 nm À1 the SAXS patterns feature a broadened 001 Bragg reflection of the PPP nanocrystals. 27 Since the platelets possess a thickness of only a few molecular layers of PPP and their large faces coincide with the (001) lattice planes (the reciprocal lattice vector G 001 is parallel to the platelet directors, cf. Fig.…”

Section: Preliminary Investigationsmentioning

confidence: 99%

Analysis of the structure of nanocomposites of triglyceride platelets and DNA

Schmiele

Knittel

Unruh

et al. 2015

Phys. Chem. Chem. Phys.

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DNA-complexes with platelet-like, cationically modified lipid nanoparticles (cLNPs) are studied with regard to the formation of nanocomposite structures with a sandwich-like arrangement of the DNA and platelets. For this purpose suspensions of platelet-like triglyceride nanocrystals, stabilized by a mixture of two nonionic (lecithin plus polysorbate 80 or poloxamer 188) and one cationic stabilizer dimethyldioctadecylammonium (DODAB), are used. The structure of the platelets in the native suspensions and their DNA-complexes, ranging from the sub-nano to the micron scale, is investigated with small-and wideangle scattering (SAXS, SANS, WAXS), calorimetry, photon correlation spectroscopy, transmission electron microscopy and computer simulations. The appearance of strong, lamellarly ordered peaks in the SAXS patterns of the DNA-complexes suggests a stacked arrangement of the nanocrystals, with the DNA being partially condensed between the platelets. This finding is supported with computer simulated small-angle scattering patterns of nanocrystal stacks, which can reproduce the measured small-angle scattering patterns on an absolute scale. The influence of the choice of the nonionic stabilizers and the amount of the cationic stabilizer DODAB on the structure of the native suspensions and the inner structure of their DNA-complexes is studied, too. Using high amounts of DODAB, lecithins with saturated acyl chains and polysorbate 80 instead of poloxamer 188 produces thinner nanocrystals, and thus decreases their repeat distances in the nanocomposites. Such nanocomposites could be of interest as DNA carriers, where the triglyceride platelets protect the sandwiched DNA from degradation.

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“…In accordance with published -phase structures of trisaturated TAGs (van Langevelde et al, 1999, and references therein), molecular models in the Z-matrix description were built as [1-3] models. The starting conformation of the elaidoyl chain at the trans double bond was taken from the crystal structure of -2 EEE (Culot et al, 2000).…”

Section: Indexing Model Building Structure Determination and Refinementioning

confidence: 99%

“…Datapoints of the same subgroup of TAGs have been connected to visualize the trend. The c axes of the (n n n) class of TAGs have been taken from the literature (van Langevelde et al, 1999) and subjected to the transformation matrix (001\100\ " 2 2 " 1 12 the chain enough to modify the molecular conformation in the -2 packing.…”

Section: Tag Subgroupmentioning

confidence: 99%

“…The monoacid (n n n) class of TAGs has been studied in most detail, using single-crystal data (n = 10, Jensen & Mabis, 1966;n = 12, Larsson, 1965;Gibon et al, 1984; n = 16, van Langevelde et al, 1999) as well as high-resolution synchrotron powder diffraction (HR-SPD) data (n = 14, 18; van Langevelde et al, 2001a; n = 13, van Langevelde et al, 2001b;n = 15, 17, 19;Helmholdt et al, 2002) and confirmed earlier postulations of the packing of this type of polymorph (Lutton, 1971(Lutton, , 1972de Jong & van Soest, 1978). The singlecrystal packing of the (n n n) analogue EEE 1 (Culot et al, 2000) is also in accordance with this result.…”

Section: Introductionmentioning

confidence: 99%

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Structures of mono-unsaturated triacylglycerols. III. The β-2 polymorphs of trans-mono-unsaturated triacylglycerols and related fully saturated triacylglycerols

Mechelen

Peschar

Schenk

2008

Acta Crystallogr Sect B

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Structures of mono-unsaturated triacylglycerols. III. The -2 polymorphs of trans-monounsaturated triacylglycerols and related fully saturated triacylglycerols van Mechelen, J.B.; Peschar, R.; Schenk, H. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The -2 crystal structures of a series of saturated and transmono-unsaturated triacylglycerols (TAGs) have been solved from high-resolution powder synchrotron diffraction data. The series comprises symmetric as well as asymmetric evennumbered TAGs and the trans-mono-unsaturated ones all have a single elaidoyl chain. The structures have been solved with the direct-space parallel-tempering program FOX and refined with the Rietveld program GSAS. The -2 structures all crystallized in the space group P " 1 1 with the same molecular conformation. Within the resolution of the data no significant difference in packing or conformation is observed between trans-mono-unsaturated TAGs and saturated (stearoyl or palmitoyl) chain-containing analogues, in spite of the lower melting points of the former. An analysis of the position of the stepped methyl end-plane in the various subgroups of TAGs confirms most but not all suppositions found in the literature.

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Structure of mono-acid even-numbered β-triacylglycerols

Cited by 74 publications

References 9 publications

Formation of liquid crystalline phases in aqueous suspensions of platelet-like tripalmitin nanoparticles

Formation of liquid crystalline phases in aqueous suspensions of platelet-like tripalmitin nanoparticles

Analysis of the structure of nanocomposites of triglyceride platelets and DNA

Structures of mono-unsaturated triacylglycerols. III. The β-2 polymorphs of trans-mono-unsaturated triacylglycerols and related fully saturated triacylglycerols

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