Pseudosymmetry in cholesterol monohydrate

Craven, B. M.

doi:10.1107/s0567740879005719

Cited by 84 publications

(55 citation statements)

References 5 publications

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“…In helical ribbons, the in-plane dimensions of the unit cell (a, b) and the angles ␣, ␤, and ␥ are very close to those of ChM. Furthermore, in crystalline ChM, the molecules in the unit cell have translational pseudosymmetry in the ab plane (28). This pseudosymmetry results in the systematic absence of (h,k,l) reflections, where both h and k are odd.…”

Section: Discussionmentioning

confidence: 92%

Structure of cholesterol helical ribbons and self-assembling biological springs

Khaykovich

Hossain

McManus³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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We report the results of x-ray-scattering studies of individual helical ribbons formed in multicomponent solutions of cholesterol solubilized by various surfactants. The solutions were chemically defined lipid concentrate (CDLC) and model bile. In these and many analogous multicomponent surfactant-cholesterol solutions, helical ribbons of two well defined pitch angles, namely 11°and 54°, are formed. We have suggested previously that this remarkable stability results from an underlying crystalline structure of the sterol ribbon strips. Using a synchrotron x-ray source, we have indeed observed Bragg reflections from individual ribbons having 11°pitch angle. We have been able to deduce the parameters of the unit cell. The crystal structure of these ribbons is similar to that of cholesterol monohydrate, with the important difference that the length of the unit cell perpendicular to the cholesterol layers is tripled. We discuss possible origins for this triplication as well as the connection between the crystalline structure and the geometrical form of the helical ribbons.crystal structure ͉ x-ray diffraction ͉ crystallization ͉ surfactants S elf assembly of helical ribbons in complex fluids is an interesting phenomenon, which poses fundamental questions about the molecular structure, elastic properties, and kinetic evolution of these objects. In particular, quaternary solutions, which contain cholesterol, nonionic surfactants, and lipids, spontaneously form helical ribbons with characteristic pitch angles of 11°and 54°. These helical ribbons are long rectangular strips, which curl along a cylindrical surface. These objects were discovered in human gallbladder bile, where they form spontaneously upon the dilution of bile. This dilution produces a solution supersaturated with respect to cholesterol (1). Formation of similar helical ribbons has been later reported in Ͼ20 different solutions with various sterols analogous to cholesterol, surfactants, and phospholipids or fatty acids (2). These helical ribbons form in a variety of axial lengths, widths, and radii. Remarkably, however, almost all have pitch angles of either 11°o r 54°. Several theoretical models have been proposed to explain the formation and properties of helical ribbons, which sometimes form in complex fluids containing chiral amphiphilic molecules (3-10). These theories were designed to describe the helical ribbons in solutions containing a single species of phospholipids, which can form bilayers. Therefore, the ribbons were modeled theoretically as fluid bilayers, where hydrophobic carbon chains are sandwiched between hydrophilic head groups. Calculations of the properties of such membranes are usually based on the curvature elasticity model (11), which is founded on general physical arguments about the dependence of the fluid membrane elastic free energy on its curvature. Based on this model, subsequent theories attempted to explain the geometrical and elastic properties of the helical ribbons. For example, the formation of helices is attributed to b...

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Section: Discussionmentioning

confidence: 92%

Structure of cholesterol helical ribbons and self-assembling biological springs

Khaykovich

Hossain

McManus³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…The dehydroergosterol monohydrate symmetry of diffraction was found to be monoclinic [Note: the cholesterol monohydrate has an apparent monoclinic symmetry, but close inspection of the twinned crystals revealed triclinic symmetry; (81,82)]. The space group was thus P2 1 , with reduced cell parameters a = 9.9747(11) Å, b =7.4731 (9) Å, c =34.054(4) Å, α =90°, β = 92.970°(2), γ= 90°.…”

Section: Resultsmentioning

confidence: 99%

Structure of Dehydroergosterol Monohydrate and Interaction with Sterol Carrier Protein‐2

McIntosh¹,

Atshaves²,

Gallegos³

et al. 2008

Lipids

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Dehydroergosterol [ergosta-5,7,9(11),22-tetraen-3β-ol] is a naturally-occurring, fluorescent sterol utilized extensively to probe membrane cholesterol distribution, cholesterol-protein interactions, and intracellular cholesterol transport both in vitro and in vivo. In aqueous solutions, the low solubility of dehydroergosterol results in the formation of monohydrate crystals similar to cholesterol. Low temperature x-ray diffraction analysis reveals that dehydroergosterol monohydrate crystallizes in the space group P2 1 with 4 molecules in the unit cell and monoclinic crystal parameters a = 9.975(1)Å, b = 7.4731(9)Å, c = 34.054(4)Å, and β = 92.970(2)° somewhat similar to ergosterol monohydrate. The molecular arrangement is in a slightly closer packed bilayer structure resembling cholesterol monohydrate. Since dehydroergosterol fluorescence emission undergoes a quantum yield enhancement and red-shift of its maximum wavelength when crystallized, formation or disruption of microcrystals was monitored with high sensitivity using cuvette-based spectroscopy and multiphoton laser scanning imaging microscopy (MPLSM). This manuscript reports on the dynamical effect of sterol carrier protein-2 (SCP-2) interacting between aqueous dispersions of dehydroergosterol monohydrate microcrystal donors and acceptors consisting not only of model membranes but also vesicles derived from plasma membranes isolated by biochemical fractionation and affinity purification from Madin-Darby canine kidney cells. Furthermore, this study provides real-time measurements of the effect of increased SCP-2 levels on the rate of disappearance of dehydroergosterol microcrystals in living cells.

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“…Geometries of ergosterol and cholesterol were obtained from crystallographic data on cholesterol [7][8][9] and ergosterol [10]. Hydrogen atoms with standard geometry were assigned to X-ray structures.…”

Section: Methodsmentioning

confidence: 99%

“…The crystal data in the case of cholesterol indicates a few different conformations present in unit cell [7][8][9]. In addition, geometry and dynamics of molecules stacked in crystalline state may differ from that of molecules floating freely in water or in biological membranes.…”

Section: Introductionmentioning

confidence: 91%