The Phase Diagram of Charged Colloidal Lipid A-Diphosphate Dispersions

Reichelt, Hendrik; Faunce, Chester A.; Paradies, Henrich H.

doi:10.1021/jp711720j

Cited by 11 publications

(26 citation statements)

References 25 publications

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“…This was shown by Revier and Aste 55 for tetrahedrally close-packed ͑tcp͒ ensembles, as well and in a study of lipid A-diphosphate. 56 For the structure reported by Revier and Aste, 55 face and edge angles were close to the ideal values of 120°and 109.47°. In the Pm3n and Fd3m cellular networks there are two examples of 24 tcp structures.…”

Section: Shape and Structure Of The Lipid A-monophosphate In The Csupporting

confidence: 67%

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Two new colloidal crystal phases of lipid A-monophosphate: Order-to-order transition in colloidal crystals

Faunce

Paradies

2009

The Journal of Chemical Physics

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A study of the structure of stable regular-shaped nanocrystals of hexa-acylated (C(14)) lipid A-monophosphate from Escherichia coli was carried out using dilute electrostatically stabilized aqueous dispersions at low ionic strength (I=1.0x10(-5)M NaCl). An order-to-order transition of colloidal clusters of lipid A-monophosphate was found at two volume fractions: phi=5.9x10(-4) and phi=11.5x10(-4). The clusters belonged to the cubic space groups Pm3n and Ia3d with unit-cell dimensions of a=4.55 nm and a=6.35 nm, respectively, as revealed by small-angle x-ray diffraction and electron-diffraction results of thin nanocrystals of lipid A-monophosphate. When viewed in the scanning electron microscope these fragile clusters displayed a number of shapes: cubic, cylindrical, and sometimes-rounded hexagons, which were extremely sensitive when exposed to an electron beam. The smallest and most numerous of the clusters appeared as approximately 7 nm cubes. Crystalline cluster formation occurred over a wide volume-fraction range, between 1.5x10(-4) and 40.0x10(-4), and at temperatures of 20 and 35 degrees C. The crystalline networks of the lipid A-monophosphate clusters may be represented by space-filling models of two pentagonal dodecahedra with six tetrakaidecahedra arrangements of lipid A-"micelles" in the cubic space group Pm3n. The simulated electron density profiles are in accord with spherical clusters of lipid A-monophosphate at the corners and at the body centers of the cubic Pm3n unit cell. The profiles are rounded tetrahedrally at distances of 1/4 and 3/4 along one of the bisectors of each face of the cubic unit cell. These nanocrystalline systems provide examples of "cellular" crystalline networks, which rearrange themselves spontaneously into three-dimensional polyhedral structures. It appears that a closely related analogy exists between the tetrahedrally close-packed networks as revealed for the lipid A-mono- and diphosphates [C. A. Faunce, H. Reichelt, H. H. Paradies, et al., J. Chem. Phys. 122, 214727 (2005); C. A. Faunce, H. Reichelt, P. Quitschau, et al., J. Chem. Phys. 127, 115103 (2007)]. However, the cubic Ia3d phase consists of two three-dimensional networks of rods, mutually intertwined but not connected. For this cubic Ia3d phase each junction involves three coplanar rods at an angle of 120 degrees, showing an interwoven labyrinth of lipid A-monophosphate rods which are connected three by three. The rod diameter is approximately 2.2 nm, which is similar in diameter to the disk-shaped aliphatic chiral core of lipid A-monophosphate (2.14 nm) with an ellipticity of 0.62 seen for the "c" position of the tetrakaidecahedra in the Pm3n cubic unit cell. An epitaxial relationship appears to exist between the {211} planes of the cubic Ia3d phase and the (001) planes of the lamellar phase as well as with the {10} planes of the hexagonal phase. The transformation of the cubic into the hexagonal phase can be reconciled by the growth of a cylinderlike assembly of lipid A-monophosphate molecules of the hexagonal pha...

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Section: Shape and Structure Of The Lipid A-monophosphate In The Csupporting

confidence: 67%

“…35,56 This would require the presence of diffusive planes in reciprocal space, however, this was not observed. The transverse extension, l −1 , of the diffusive planes was smaller than the resolution; hence under the given con- ditions it was very small compared to 1 / a.…”

Section: F Cubic-hexagonal Transformationmentioning

confidence: 97%

Two new colloidal crystal phases of lipid A-monophosphate: Order-to-order transition in colloidal crystals

Faunce

Paradies

2009

The Journal of Chemical Physics

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“…The phase transitions were a correlated liquid phase, a cubic FCC and a body-centered cubic crystalline phase [35]. These phases were detected in the presence of mM NaCl for different volume fractions, ; and various crystal forms (BCC and FCC) could be obtained.…”

Section: Freezing and Meltingmentioning

confidence: 93%

“…However, a mixture of equimolar concentrations of the two antagonistic molecules revealed a SAXS-powder diffraction pattern a light scattering profile for crystals of sizes of 1 m that could be indexed for a much larger face-centered (Fd3m) unit cell, with a = 58.0 nm. However, when employing the similar conditions for colloidal Lipid A-diphosphate dispersions but through addition of M NaOH rather than by removing NaCl [35] a very different phase behavior was observed (Fig. 2).…”

Section: Freezing and Meltingmentioning

confidence: 99%

“…The influence of polydispersity in charge, size and mass has been elucidated and included in all further experiments and simulations [7][8][9][10][11][12][13]. The most compelling observations of the colloidal crystallization and also of Lipid A-diphosphates in aqueous solutions at very low ionic strength conditions ( 10 -6 M) are the order-disorder transition and the structural transition from a body-centered cubic (BCC) to a face-centered (FCC) structure [34,35]. In these dispersions it is essential to consider the co-occurrence of phase separation and crystalline ordering, where it has been suggested that the crystalline phase is a supercooled liquid phase with some liquid retained in a metastabile state for a certain period of time, even at   0.58.…”

Section: Fluid-solid Phase Transition Of Self-assembled Lipid A-diphomentioning

confidence: 99%

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Mineralization of Lipid A-Phosphates in Three- and Two-Dimensional Colloidal Dispersions

Paradies¹,

Quitschau²,

Reichelt³

et al. 2012

Recent Advances in Crystallography

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Endotoxins: Relationship Between Structure, Function, and Activity

Brandenburg

Schromm

Gutsmann

2010

Subcellular Biochemistry

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Endotoxins as amphiphilic components of the outer layer of the outer membrane of Gram-negative bacteria exert their immunostimulatory activity after release from bacterial cells. Thus, the characterization of the physicochemical properties of this glycolipid in physiological fluids is of utmost importance for an understanding of cell activation processes. Here, the essential physicochemical parameters describing endotoxins such as critical micellar concentration, acyl chain fluidity, intramolecular conformation, supramolecular structures, and size as well as morphology of the aggregates are discussed and assessed with respect to their importance for an understanding of the interaction mechanisms with immunorelevant cells. The reviewed data clearly indicate that knowledge of these parameters is essential for understanding the bioactivity of not only endotoxins, but also endotoxin-like amphiphiles.

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The Phase Diagram of Charged Colloidal Lipid A-Diphosphate Dispersions

Cited by 11 publications

References 25 publications

Two new colloidal crystal phases of lipid A-monophosphate: Order-to-order transition in colloidal crystals

Two new colloidal crystal phases of lipid A-monophosphate: Order-to-order transition in colloidal crystals

Mineralization of Lipid A-Phosphates in Three- and Two-Dimensional Colloidal Dispersions

Endotoxins: Relationship Between Structure, Function, and Activity

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