Small-angle X-ray Diffraction Patterns Research Articles

Structure of vitaminylated lipids in aqueous dispersion: X-ray diffraction and phosphorus-31 NMR studies of N-biotinylphosphatidylethanolamines

The structures of the phases formed in excess buffer (at pH 7.4) by a homologous series of saturated diacylphosphatidylethanolamines in which the headgroup is N-derivatized with biotin have been investigated for chain lengths of C(12:0) to C(20:0), using both 31P nuclear magnetic resonance (NMR) spectroscopy and small-angle X-ray diffraction. In 1 M NaCl, all lipids display 31P NMR spectra characteristic of a lamellar gel phase at low temperature. In the fluid phase, the lipids of C(12:0) and C(14:0) chain lengths display isotropic 31P NMR spectra, corresponding to aggregated phases with high surface curvature, whereas those with C(18:0) and C(20:0) chain lengths display sharp axial powder patterns characteristic of a lamellar (L alpha) phase. The lipid of intermediate C(16:0) chain length displays a more complex temperature dependence of the 31P NMR spectra in the fluid phase. The spectra convert from an axial powder pattern of unusually low chemical shift anisotropy to one characteristic of a fluid lamellar (L alpha) phase with increasing temperature. The small-angle X-ray diffraction patterns of the lipids in 1 M NaCl have lamellar repeat spacings in the gel phase which increase linearly with chain length and are consistently lower than those in the fluid phase [for chain lengths of C(16:0) to C(20:0)]. In addition, the gradient in long spacing with chain length in the gel phase is approximately half that expected for a gel phase with untilted, all-trans chains, indicating that the lipid chains are interdigitated in the gel phase (L beta i).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrostatic interaction of poly( l-lysine) with dipalmitoylphosphatidic acid studied by X-ray diffraction

Structure of dipalmitoylphosphatidic acid (DPPA) bilayers in the presence of poly( l-lysine) is proposed from the results of X-ray diffraction obtained by a storage phosphir detector with a high resolution called an imaging plate. The small-angle X-ray diffraction pattern exhibits that DPPA/poly( l-lysine) complex forms a highly ordered multilamellar structure. The electron density profile of the DPPA/poly( l-lysine) complex draws that only one poly( l-lysine) layer is intercalated betweenthe neighboring DPPA bilayers. The wide-angle X-ray diffraction pattern suggests that the presence of poly( l-lysine) hardly affects the nature of hydrocarbon chain packing in the DPPA bilayers. The X-ray reflection from the DPPA/poly( l-lysine) complex indicates that the poly( l-kysine) molecules adopt a β-sheet conformation on the surface of the DPPA bilayers. The both surface areas occupied by a headgroup of the DPPA and by a lysine residue in poly( l-lysine) are estimated from the observed spacings. The number ratio of lysine residues to DPPA headgroups per unit area is greaterthan unity. Therefore, one DPPA headgroup interacts with more than one lysine residue electrostatically, i.e., the electric charge distributions in both the surface of a DPPA bilayer and the poly( l-lysine) β-sheet are incommensurate.

Changes in the filament lattice of skeletal muscle fibres induced by changes in osmotic pressure, sarcomere length and the number of crossbridges

Equatorial small-angle X-ray diffraction patterns offer the possibility of obtaining detailed knowledge about interfilament distance and mass distribution of the myofilament lattice of skeletal muscle. These patterns of skinned frog-muscle fibres have been studied as a function of changes in the incubation solution using the Synchrotron Radiation Source in Daresbury (England). The results of these X-ray diffraction measurements and the results of measurements of the elastic properties of single muscle fibres, with microsecond time resolution, enabled an insight to be gained into the mechanism of muscle contraction. Interfilament distance decreased with increasing osmotic pressure in the absence of free calcium, whereas the mass distribution within the filament lattice did not change. Similar changes in the interfilament distance could be obtained either by decreasing the ionic strength in the absence of free calcium or by increasing the concentration of free calcium of the incubation solution. In both cases, however, mass distribution within the filament lattice also changed, which indicates that under these conditions the number of operating actomyosin complexes in the muscle fibre (crossbridges) tends to increase. The changes in interfilament distance and mass distribution that occur which depend on the free calcium concentration can be explained by a changed number of force-generating crossbridges. In the case of changes induced by ionic strength two effects interfere. Only part of the change in lattice spacing can be explained by an increased number of weakly attached crossbridges; the remaining part is caused by a process similar to that in the case of osmotic pressure. The effect of weakly attached crossbridges in the absence of free calcium under normal ionic strength conditions is small. Therefore, the large decrement in interfilament distance due to an increased sarcomere length, in the absence of free calcium, is not caused by weakly attached crossbridges. Changes in sacromere length, in the presence of free calcium, resulted in changes in the number of force-generating crossbridges. However, the observed effect on interfilament distance cannot be explained solely by the variation of the number of force-generating crossbridges. The results of X-ray diffraction patterns and stiffness measurements of fibres in rigor solutions [absence of ATP (adenosine triphosphate) and calcium] and fibres in calcium solutions indicated that the (force-generating) crossbridges in the latter differ from crossbridges in rigor fibres.

Rapid small-angle X-ray diffraction of a tonically contracting molluscan smooth muscle recorded with imaging plates

Small-angle X-ray diffraction patterns from the anterior byssus retractor muscles of Mytilus edulis contracting tonically in response to stimulation with acetylcholine were recorded in a 30 s exposure with synchrotron radiation and a high-sensitivity X-ray area detector called an imaging plate. The 190 Å layer line from the thin filaments increased in intensity with increase in tonic tension up to 6 x 104 kg m−2. Above this value, the layer-line intensity remained almost constant and comparable to that for a contracting skeletal muscle, indicating that the same structural changes of the thin filaments occur in both muscles.

INTERACTION OF A MODEL EPIDERMAL LIPID WITH A VEGETABLE OIL ADDUCT

Abstract A study of the interaction between a model epidermal lipid and 2(alkoyloxy)-1-[(alkoyloxy)methyl]-ethyl-7-(4 heptyl-5,6-dicarboxyl-2-cyclo-hexene-1-yl)heptanoate, (G2) was made by use of small angle X-ray diffraction. The small angle X-ray diffraction pattern of the epidermal lipid model was first compared to the X-ray pattern obtained from human stratum corneum. Increase in the water content of the model epidermal lipid from 32% to 35% caused a shift in the broad diffraction peak from 50-80A to 50-70A. No additional shift was found at further addition of water. The addition of G2 to the 32% water model also caused a shift toward smaller interlayer spacing. The effect of G2 was most dramatic for the model epidermal lipid at the lowest water content.

Structural modifications of air-dried tendon collagen on heating

The modification of collagen molecular packing as a function of the removal of bound and structural water have been investigated on air-dried rat tail tendon. Isothermal curves, dilatometric measurement, high and small angle X-ray diffraction patterns—recorded using conventional and synchrotron radiaiton sources respectively—have been obtained on samples heated in air at different temperatures up to 200°C. A shortening of collagen intermolecular distances and slight modifications of quaternary structure and fibre dimensions can be observed during the release of bound water. The removal of structural water is accompanied by disordering of the three polypeptide chains, a strong reduction of fibre length and d-axial spacing, and modifications of the electron density distribution inside the repeating period. The structural modifications observed during the removal of bound water and of most of the structural water, obtained on heating, are reversible. Release of the most lightly bound water, probably associated with the beginning of the depolymerization process, induces irreversible modification of the molecular packing.

Intensity increases of actin layer-lines on activation of the Limulus muscle

Small angle x-ray diffraction patterns were recorded from isometrically contracting Limulus (horseshoe crab) telson levator muscle using a multiwire proportional-area detector on the storage ring DORIS. In the pattern a substantial increase in intensity is observed on the thin-filament-associated layer-line at 1/38 nm-1 (the first actin layer-line) with a maximum increase at a radial spacing of R = 0.07 nm-1 but there is a much smaller change in the intensity of the 5.9-nm layer-line, which also arises from the thin filament structure. The results suggest that during contraction the myosin heads, presumably being attached to the thin filaments, are arranged along the long-stranded helical tracks of the thin filaments but that the spatial relationship between the heads and the actin monomers varies. Intensity increases have also been observed (Maéda et al., manuscript in preparation) in the part of the patterns from frog muscle and barnacle muscle, which are attributable to the first actin layer-line. It is thus likely that the intensity increase of the first actin layer-line on the Limulus pattern is associated not with structural features which are special to Limulus muscle, but with the tension generating processes that are shared by muscles in general.

Thermal Optical Analysis of Cholesteryl Methacrylate and Butyl Methacrylate Copolymers

As a side chain type of liquid crystalline polymer, the copolymers of cholesteryl methacrylate and butyl methacrylate were synthesized. When the mesomorphic behavior of the copolymers was examined with a polarized microscope, the observed transition temperatures were so much varied that the mesomorphic behavior had to be studied by thermal optical analysis (TOA). TOA curves with a single peak were obtained by a sandwich-type film prepared by interposing the casting solution between two cover glasses and drying sufficiently. The mesomorphic temperature region increased with increasing mole fraction of cholesteryl methacrylate (ChMA) in the copolymers. The appearing and clearing temperatures of birefringence shifted to the higher temperature side with increasing mole fraction. The effect of pretreatment of the cover glasses with trimethyl chlorosilane was examined. The relation between the maximum intensity of the TOA curve and the film thickness was studied for both films prepared with the treated and untreated glasses. The intensity remarkably increased with increasing film thickness for the treated glasses, but no such correlation was found for the untreated glasses. A sandwich cell was prepared by the same casting method of a TOA sample with tin coated glasses. The cell was heated up to the mesomorphic temperature under a dc field of 40 V. Although no electro-optical effect was observed in the first heating step, the apparent flow instability, similar to William’s domain, appeared in the cooling step from the isotropic state. Small angle X-ray diffraction patterns were obtained for the samples of both cast and annealed films. A sharp peak at 2θ=2.5° corresponding to 35.5 A of periodicity was observed only for annealed film.

The Influence of Solvent on Nonaqueous Lyotropic Liquid Crystalline Phase Formed by Triethanolammonium Oleate

The geometry of a lyotropic lamellar liquid crystalline phase formed by triethanolamine (TEA) and oleic acid (OLA) with solubilized igomers of polyethylene glycols and different types of oils was termined from small angle X-ray diffraction patterns. The region of ability of the lamellar liquid crystalline phase on addition of soluble ycols or oils was found to depend on the molar ratio of triethanolamine to oleic acid. A series of ethylene glycol oligomers, which were solubized in the polar part of the structure, showed maximum solubilization at the OLA–TEA mole ratio of 1.6. The organic oils, on the other hand, which are solubilized into the hydrophobic part of the structure, exhibited maximum solubilization at the OLA-TEA mole ratio of 0.8.

Small Angle X-Ray diffraction Patterns of Stratum Corneum and a Model Structure for Its Lip ids

ABSTRACT The structure of the lipid part of stratum corneum,was shown to be a lamellar liquid crystal in accordance with earlier suagestions by Elias et al. The main structure forming compound was found to be the fatly acids which when partially neutralized gave a lamellar liquid crystal over a wide range of water content. Small angle x-ray diffraction was used to estimate the location of the remaining lipid compounds showing localization to be between the methyl group layers of the hydrocarbon chains of some components while remaining compounds were intercalated between the acid/soap molecules.

Solid-state morphology and mechanical properties of Kevlar 29 fiber

Abstract Kevlar 29 is an aromatic polyamide fiber spun from the polymer poly(p-phenylene terephthalamide). It has a paracrystalline structure with a lattice distortion parameter g = 5.9% and an a∗ constant = 0.51. The equatorial x-ray “crystallinity” is 68%; the microparacrystal (mPC) sizes are D 002 = 50 nm, D 110 = 4.4 nm, and D 200 = 3.6 nm. The mPCs are well oriented; the orientation parameter = 0.047. The small-angle x-ray diffraction pattern indicated that the fiber has nc chain folding. It has high tenacity (2.81 GNm−2), close to the tenacity of steel; high Young's modulus (63.9 GNm−2); small breaking strain (3.8%); and a very high melting point (600°C). Wide- and small-angle x-ray diffraction techniques, differential scanning calorimetry (DSC), and an Amsler tensile tester have been used to characterize the fiber and to assess the effect of annealing on its morphology and mechanical properties.

X-ray structure analysis of thin filaments of a molluscan smooth muscle in the living relaxed state

In the small-angle x-ray diffraction pattern of the living relaxed anterior byssus retractor muscle of Mytilus edulis, the thin filaments showed the following features. The 59.8-A reflection was much stronger and a little farther from the meridian than the 51.9-A reflection, although they are both contributions of the first-order Bessel function and are comparable with each other in the height from the equator. The 381-A reflection, given by the second-order Bessel function, was weaker than the 59.8-A reflection by more than the difference between the peak values of the first- and second-order Bessel functions, and was not so distant radially from the latter as estimated from the amount of peak shift brought about by the alteration of the Bessel order. A model of the thin filament was made on the basis of inverse Fourier transformation of the scattering amplitude, and the above features were explained by the characteristic shape of actin shown in this model. The actin subunits are elongated along the genetic left-hand helix with a pitch of 59.8 A, and are bonded together along the genetic helix in the inner part of the filament.

Structure of myosin/paramyosin filaments from a molluscan smooth muscle

Small-angle X-ray diffraction patterns of chemically skinned pedal retractor muscles from Mytilus (PRM) in the relaxed state show a set of diffuse off-meridional reflections that arise from a helical array of myosin crossbridges with 8/3 screw symmetry. Experiments involving extraction of myosin as well as analysis of the rigor pattern have been used to confirm the origin of these reflections. The relatively high myosin/paramyosin molar ratio (1.3 to 1.6) in PRM compared to other molluscan smooth muscles may account for the observation of the relatively stronger diffraction from the myosin array. Thick filaments isolated from PRM and contrasted by negative staining for electron microscopy appear to be very long (up to 17 micron), and to have a rather small diameter (about 40 nm at the center); they taper gradually toward the ends. These filaments show a clear transverse band pattern repeating at 14.4 nm and elongated projections (crossbridges) at the surface except in the central bare zone. Optical diffraction patterns show reflections from crossbridges consistent with the X-ray patterns of the relaxed whole muscle. Filaments unidirectionally shadowed with platinum show diagonal striations running at an angle of about 17 degrees to the filament axis, revealing that the crossbridges are arrayed in a right-handed helix. The paramyosin core is clearly seen upon extraction of myosin. Observations on both negatively stained and sectioned material are consistent with the results of Elliott (1979) and Bennett & Elliott (1981) suggesting a layered structure of the core. Cores stripped of myosin, however, appear to undergo some distortion indicating that the three-dimensional structure is not yet completely solved. The assembly of these thick filaments presents intriguing structural problems since the myosin surface lattice does not appear to have the same symmetry as the underlying paramyosin core.

Hydroxyapatite crystals orientation during a pathological calcification of human tendons

The structural relationship between collagen fibers and apatite deposits in mineralized tissues has been widely investigated by electron microscopy and X-ray diffraction techniques [1]. For these studies oriented samples, such as osteons and turkey leg tendon at different degrees of calcification, have been particularly useful [2–4]. However many features of the problem are still obscure. The availability of oriented samples containing collagen fibers at low degrees of calcification is an essential condition to obtain information about the sites of the initial deposition of the apatite crystals in the collagen fibers structure using diffraction techniques. Tendon affected by diffuse idiopatic skeletal hyperostosis, which is a disease characterized by calcification and ossification of tendons and ligaments [5], is a suitable tissue because calcium hydroxyapatite is laid down within the tissue to different degrees along its length and to different degrees with the development of the disease. We have examined fragments of human tendons which showed radiographic evidence of this pathological calcification at the sites of attachment to olecranon by small and high angle X-ray diffraction techniques in order to investigate the inorganic deposits and their interaction with collagen fibers. X-ray diffractometric analysis carried out on powdered mineralized samples permitted the recognition of the mineral deposit present in the tissue as hydroxyapatite. This inorganic phase exhibits a good degree of crystallinity and cell parameters a = 9.40(1) Å, c = 6.89(1) Å very close to those of bone apatite. High angle X-ray diffraction analysis carried out by means of a flat camera on fragments dissected from several zones of the tendons revealed a different orientation of the apatite crystals as a function of the degree of calcification of the tissue. The apatite crystals appear to be preferentially oriented with their c-axis parallel to the tendon axis in the zones at a low degree of calcification. This orientation reduces progressively as the degree of calcification increases and no preferential orientation can be observed in the fully calcified zones. The X-ray reflections characteristic of collagen molecular structure appear superimposed on those of the inorganic phase and show that collagen fibers orientation is always coincident with that of the c-axis of the hydroxyapatite crystals. The small angle X-ray diffraction pattern recorded on fragments at a low degree of calcification shows the characteristic reflections of collagen fibrillar structure which appear oriented parallel to the tendon axis. No diffraction reflection due to collagen can be observed in the small angle X-ray diffraction pattern obtained from fully calcified fragments. These results show a clear relationship between apatite crystals deposition and collagen fibers distribution and orientation. In fact at a low degree of calcification apatite are aligned parallel to the collagen fibers of the tendon whereas at a high degree of calcification no orientation of collagen fibers as well as of apatite crystals could be revealed. This agrees with the morphological observations which show that at a high degree of calcification the collagen fibers lose their characteristic orientation parallel to the tendon axis and assume an isotropic distribution in a structure closely resembling that characteristic of cancellous bone. Furthermore it must be noted that the collagen molecular packing does not seem to be affected by the mineralization process, at least during the initial stage of the deposition.

Small-angle X-ray data processing for planar multilayered structures. 2. Experimental determination of the parameters for retinal photoreceptors and sarcoplasmic reticulum membranes

The Fourier-transform values are obtained by multiplying the integrated intensities of X-ray patterns by the correction factor C(h). The problem of determining C(h) for biological specimens which have a planar multi-layered structure and which remain stationary during the X-ray experiment is treated. Parameters for evaluating C(h) can be obtained from pinhole (limited slit) collimated small-angle X-ray diffraction patterns. Two biological structures, namely retinal photoreceptors and sarcoplasmic reticulum membranes have been studied. Correction factors for these structures have been experimentally measured.

Skin collagen has an unusual d-spacing

Small angle X-ray diffraction patterns show a d-spacing of 65 ± 0.5 nm for the collagen in wet intact skin of amphibian larvae (tadpole) as well as from that of mature frogs, chickens and mice. The collagen in these tissues is largely collagen I which exhibits a d-spacing of 67 ± 0.5 nm in wet intact unstretched tendons. The d-spacing of the skin collagen did not decrease on drying, while it is well known that that of tendon collagen does decrease on drying. The reasons for the decreased d-spacing in the normal skin are not known but we suggest that the different glycosaminoglycan content of skin may be an important factor.

水‐油‐非イオン界面活性剤‐アニオン界面活性剤四成分系の溶解状態

Phase diagrams have been determined as a function of temperature for the followihg systems; water-dodecane-surfactants (nonionic surfactant: anionic surfactant=80:20-95:5), water-surfactants (nonionic surfantant: anionic surfactant=90:10).By the effects of anionic surfactant, Phase Inversion Temperature (PIT) rised in these systems, and anisotropic liquid crystalline phase regions expanded as a function of temperature.Consequently, the translucent emulsion region and gel region were formed in O/W emulsion region.In order to understand the specific characteristic of the meso phase, polarizing microscopic patterns, viscosity, differential scanning calorimetery curves and small angle X-ray diffraction patterns were measured.These are important for the cosmetic chemists who are charged with developing a stable product.

Small angle X-ray scattering from the inner and outer membranes from Escherichia coli

Small angle X-ray data from purified forms of inner or cytoplasmic and outer membranes from Escherichia coli have been obtained and appear to be qualitatively similar. Transitory changes are apparent in the circularly averaged X-ray profiles from inner membrane. Such results could be due to the loss or denaturation of peripheral membrane proteins. Some partially dried forms of outer membrane are partly ordered and produce diffraction patterns which support an underlying bilayer structure. An extra light membrane fraction which results from membrane preparations utilizing a French pressure cell for spheroplast disruption has been characterized and shown to be similar to inner membrane. The purified membranes produce small angle X-ray diffraction patterns which are much different from those of lipid dispersions and the differences are attributable to the high protein content of the intact membranes. While the small angle X-ray region may be useful for characterizing the membrane preparations, the paucity of detail in the diffraction pattern suggest that it will be of little value in describing the complex underlying membrane structure.

Structure of collagen in cartilage of intervertebral disk.

Small-angle x-ray and neutron diffraction patterns have been obtained from the annulus fibrosus of porcine intervertebral disk. These show that the collagen in this tissue is modified compared with that in tendon.

Structural organization of collagen fibrils in media aortic wall.

Small-angle X-ray diffraction patterns of bovine, human and porcine media aortic wall show meridional reflections corresponding to a periodicity which suggest a molecular packing typical of tendon collagen. However the meridional intensity distribution of stretched air dried aortic samples appears different from that of air-dried tendon, probably because of the presence of a large amount of type III collagen with the environment, which are specific for aortic tissue. The stretched wet aortic samples show a marked decrease in intensity, revealing an extensive disorder in the axially-projected structure of the fibrils. When a loading system simulating the effect of blood pressure is applied to a ring of aorta, no evidence of orientation of collagen is seen by X-ray diffraction, as would be expected if collagen fibrils had an isotropic distribution inside the aorta media. Scanning electroni microscopy supports the existence of a network of collagen fibrils surrounding elastic lamellae.