Structure of C
 n
 C
 n+2C
 n
 -type (n = even) β′-triacylglycerols

Langevelde, A.J. van; Malssen, K.F. van; Driessen, R.A.J.; Goubitz, K.; Hollander, F. F. A.; Peschar, R.; Zwart, Peter H.; Schenk, H.

doi:10.1107/s0108768100009927

Cited by 61 publications

(32 citation statements)

References 23 publications

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“…In fact, the observed intensities of diffraction maxima are different from typical diffraction spectra registered for two-chain type packing of TAG molecules. Usually, structures formed by two-chain packing of triacylglycerols are characterized by a very intense first-order peak, a weak (or absent) second-order peak, an intense (or middle) third-order peak, and a weak (or absent) fourth-order peak 26-32 (a similar conclusion can be reached on the basis of calculated XRD patterns, using structural parameters reported for triacylglycerols 3,7,9,10,33 ). In contrast, the R 2 phase of StOSt has very intense first-and second-order, vanishingly small thirdorder, and intense fourth-order peaks (Table 2; Figure 6a).…”

Section: Discussionmentioning

confidence: 63%

“…(n + n 0 ) 2 c s sin τ t (9) essential background for a model of the crystal structure of the γ phase of StOSt. It has to be noted that the electron density within the middle of the γ-phase layer, associated with a sublayer of the oleoyl chains, is lower than the electron density at the interface of the layer associated with the stearoyl sublayers (Figure 8), which is not expected from modeling (Figure 1c).…”

Section: )mentioning

confidence: 99%

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The Packing of Triacylglycerols from SAXS Measurements: Application to the Structure of 1,3-Distearoyl-2-oleoyl-sn-glycerol Crystal Phases

Mykhaylyk

Hamley

2004

J. Phys. Chem. B

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An approach by which electron density profiles of triacylglycerols (TAGs) can be reconstructed from X-ray diffraction data has been applied to analyze lamellar structures formed by 1,3-distearoyl-2-oleoyl-sn-glycerol (StOSt). The method is analogous to one previously used to analyze lipid bilayer structures. Based on the structure of tristearin molecules crystallized in the phase, the projection of the electron density profile along the layer normal in structures with a lamellar packing of the TAG has been calculated for both tilted and nontilted arrangements of the molecules. This enables the position of glycerol groups to be identified in the electron density profile reconstructed from the first few 00l lamellar peaks measured by small-angle X-ray scattering (SAXS). It is demonstrated that structure amplitudes of both two-chain-and three-chainlength layers formed by the same equally tilted TAG molecules follow a unique curve on a plot of the structure amplitudes versus the scattering wave vector. The approach is applied to examine the complex polymorphism of StOSt during crystallization. Time-resolved SAXS/WAXS measurements have been performed during isothermal crystallization (from the liquid phase at 55°C) at different temperatures (0-22.5°C), followed by annealing at 30°C. It is concluded that six phases (R 2 , R 1 , γ, ′, 1 , and 2 ) and one metastable structure can be formed by StOSt molecules through polymorphic transformations. Fourier reconstructed projections of the electron density profile along the layer normal show that symmetry-related pairs of StOSt molecules adopt a two-chain packing motif in the R 1 phase and a three-chain packing motif in the more stable γ, ′, and phases of StOSt. In accordance with the electron density profile, the unstable R 2 phase appearing at the initial stage of the crystallization can be ascribed to three-chain packing, which is probably the result of the twisted acyl chains of StOSt molecules. A combination of structural parameters obtained in the study, together with models for terrace-like arrangements of terminal methyl groups developed by de Jong et al., allowed the structure of γ and phases to be clarified. The driving forces for the polymorphic transformations taking place during crystallization and a schematic diagram of phase transitions are discussed.

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Section: Discussionmentioning

confidence: 63%

Section: )mentioning

confidence: 99%

The Packing of Triacylglycerols from SAXS Measurements: Application to the Structure of 1,3-Distearoyl-2-oleoyl-sn-glycerol Crystal Phases

Mykhaylyk

Hamley

2004

J. Phys. Chem. B

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“…An alternative technique nowadays is to solve a crystal structure from powder diffraction data using direct-space search techniques. Helped by the existence of homologous, single-crystal-based crystal structures as start search models, several crystal structures of trisaturated TAGs were solved from synchrotron powder data (Van Langevelde et al, 2000, 2002Helmholdt et al, 2002). In recent years, the direct-space search techniques have been improved considerably and no longer require singlecrystal precursors.…”

Section: Introductionmentioning

confidence: 99%

Structures of mono-unsaturated triacylglycerols. I. The β₁ polymorph

Mechelen

Peschar

Schenk

2006

Acta Crystallogr Sect B

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The crystal structures of the beta1 polymorphs of mono-unsaturated triacylglycerols have been solved from high-resolution laboratory and synchrotron powder diffraction data for five pure compounds, the 1,3-dimyristoyl-2-oleoylglycerol (beta1-MOM), 1,3-dipalmitoyl-2-oleoylglycerol (beta1-POP), 1,3-distearoyl-2-oleoylglycerol (beta1-SOS), 1-palmitoyl-2-oleoyl-3-stearoylglycerol (beta1-POS), 1-stearoyl-2-oleoyl-3-arachidoylglycerol (beta1-SOA) and three mixtures: the co-crystallized 1:1 molar mixture of SOS and POP [beta1-SOS/POP (1:1)] and two cocoa butters from Bahia and Ivory Coast, both in their beta-VI (=beta1) polymorph. All eight beta1 structures crystallized in the space group (P2(1)/n) and have two short cell axes (5.44-5.46 and 8.18-8.22 A), as well as a very long b axis (112-135 A). The dominant-zone problem in the indexing of the powder patterns was solved with the special brute-force indexing routine LSQDETC from the POWSIM program. Structures were solved using the direct-space parallel-tempering method FOX and refined with GSAS. Along the b axis, alternations of inversion-centre-related ;three-packs' can be discerned. Each ;three-pack' has a central oleic zone, with oleic acyl chains of the molecules being packed together, that is sandwiched between two saturated-chain zones. The conformation of the triacylglycerol molecules is relatively ;flat' because the least-square planes through the saturated chains and those through the saturated parts of the olein chain are parallel. The solution of the beta1 structures is a step forward towards understanding the mechanism of fat-bloom formation in dark chocolate and has led to a reexamination of the beta2 structural model [see van Mechelen et al. (2006). Acta Cryst. B62, 1131-1138].

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“…Crystal structures of TAGs in the H polymorph are hardly available. A packing model and a crystal structure model at the atomic level for the H -stable C n C n + 2 C n -type (n = even) series have been proposed (Van Langevelde et al, 1999b;Van de Streek et al, 1999, respectively), but only recently for two members of this series a successful crystal structure determination and re®nement has been carried out (Van Langevelde et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Structure of β-trimyristin and β-tristearin from high-resolution X-ray powder diffraction data

Langevelde¹,

Peschar

Schenk

2001

Acta Crystallogr B Struct Sci

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The crystal structures of beta-1,2,3-tritetradecanoylglycerol (beta-trimyristin or beta-MMM) and beta-1,2,3-trioctadecanoylglycerol (beta-tristearin or beta-SSS) have been determined from high-resolution synchrotron X-ray powder diffraction data. Grid search and Rietveld refinement have been used to determine and refine the structure, respectively. Both substances crystallize in space group P1; with Z = 2. The unit-cell parameters for beta-MMM are a = 12.0626 (6), b = 41.714 (1), c = 5.4588 (3) A, alpha = 73.388 (4), beta = 100.408 (5) and gamma = 118.274 (4) degrees. For beta-SSS the unit-cell parameters are a = 12.0053 (7), b = 51.902 (2), c = 5.4450 (3) A, alpha = 73.752 (5), beta = 100.256 (6) and gamma = 117.691 (5) degrees. Soft-distance restraints have been applied to the molecules during refinement. For beta-MMM the final R(p) value obtained is 0.053 and for beta-SSS the final R(p) value is 0.041.

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Structure of C_nC_n+2C_n-type (n = even) β′-triacylglycerols

Cited by 61 publications

References 23 publications

The Packing of Triacylglycerols from SAXS Measurements: Application to the Structure of 1,3-Distearoyl-2-oleoyl-sn-glycerol Crystal Phases

The Packing of Triacylglycerols from SAXS Measurements: Application to the Structure of 1,3-Distearoyl-2-oleoyl-sn-glycerol Crystal Phases

Structures of mono-unsaturated triacylglycerols. I. The β₁ polymorph

Structure of β-trimyristin and β-tristearin from high-resolution X-ray powder diffraction data

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Structure of C n C n+2C n -type (n = even) β′-triacylglycerols

Cited by 61 publications

References 23 publications

The Packing of Triacylglycerols from SAXS Measurements: Application to the Structure of 1,3-Distearoyl-2-oleoyl-sn-glycerol Crystal Phases

The Packing of Triacylglycerols from SAXS Measurements: Application to the Structure of 1,3-Distearoyl-2-oleoyl-sn-glycerol Crystal Phases

Structures of mono-unsaturated triacylglycerols. I. The β1 polymorph

Structure of β-trimyristin and β-tristearin from high-resolution X-ray powder diffraction data

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Product

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Structure of C_nC_n+2C_n-type (n = even) β′-triacylglycerols

Structures of mono-unsaturated triacylglycerols. I. The β₁ polymorph