Small-angle X-ray Diffraction Studies Research Articles

Physical-Chemical Characterization of Bilayer Membranes Derived from (±) α-Tocopherol-Based Gemini Lipids and Their Interaction with Phosphatidylcholine Bilayers and Lipoplex Formation with Plasmid DNA.

Membrane formation and aggregation properties of two series of (±) α-tocopherol-based cationic gemini lipids without and with hydroxyl functionalities at the headgroup region (TnS n = 3, 4, 5, 6, 8, and 12; THnS n = 4, 5, 6, 8, and 12) with varying polymethylene spacer lengths were investigated extensively while comparing with the corresponding properties of the monomeric counterparts (TM and THM). Liposomal suspensions of each cationic lipid were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), zeta potential measurements, and small-angle X-ray diffraction studies. The length of the spacer and the presence of hydroxyl functionalities at the headgroup region strongly contribute to the aggregation behavior of these gemini lipids in water. The interaction of each tocopherol lipid with a model phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC)-derived vesicles, was thoroughly examined by differential scanning calorimetry (DSC) and 1,6-diphenyl-1,3,5-hexatriene (DPH)-doped fluorescence anisotropy measurements. The binding efficiency of the cationic tocopherol liposomes with plasmid DNA (pDNA) was followed by an ethidium bromide (EB) exclusion assay and zeta potential measurements, whereas negatively charged micellar sodium dodecyl sulfate (SDS)-mediated release of the pDNA from various preformed pDNA-liposomal complexes (lipoplex) was studied by an ethidium bromide (EB) reintercalation assay. The structural transformation of pDNA upon complexation with liposome was characterized using circular dichroism (CD) spectroscopic measurements. Gemini lipid-pDNA interactions depend on both the presence of hydroxyl functionalities at the headgroups and the length of the spacer chain between the headgroups. Succinctly, we performed a detailed physical-chemical characterization of the membranes formed from cationic monomeric and gemini lipids bearing tocopherol as their hydrophobic backbone and describe the role of inserting the -OH group at the headgroup of such lipids.

Discotic liquid crystals of transition metal complexes 58 : Novel phthalocyanine-based mesogenic monomers and polymers exhibiting spontaneous homeotropic alignment and helical tetragonal columnar structure

Two synthetizations of a novel series of phthalocyanine-based discotic liquid crystals substituted by a polymerizable group, acryloyl group or a norbornene group: 2-(12-acryloyloxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexakis (3,4-dialkoxyphenoxy)phthalocyaninato copper(II) [abbreviated as (n,12)PcCu(OCH[Formula: see text])(Acryloyl) (7: e ([Formula: see text] = 10), f ([Formula: see text] = 12), g ([Formula: see text] = 14))] and 2-(12-norborn-2-ene carbonyloxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexakis(3,4-dialkoxyphenoxy)-phthalocyaninato copper(II): [abbreviated as (n, 12)PcCu(OCH[Formula: see text])(Norb) (9e, f, g)]. Their liquid crystalline properties and homeotropic alignment were investigated using a polarizing microscope, a differential scanning calorimetry (DSC), and a temperature-variable X-ray diffractometer. As a result, each of the derivatives gave a Col[Formula: see text] mesophase in the higher temperature region, displaying perfect homeotropic alignment between the two glass plates. In order to obtain the thin film while keeping their homeotropic alignment at room temperature, attempts to polymerize the monomers, 7 and 9, in the Col[Formula: see text] phase showed homeotropic alignment. The polymerization of the acryloyl-substituted monomers (7) was not successful in any of the methods, whereas the polymerization of norbornene-substituted monomers (9) was quite successful by ring-opening metathesis polymerization with a Grubbs catalyst to obtain the novel polymers, poly-(n, 12)PcCu(OCH[Formula: see text])(Norb) (10e, f, g). Each of the polymers (10) were found to show a perfect homeotropic alignment from room temperature to ca. 200[Formula: see text]C of the decomposition temperature. Moreover, it was also revealed from temperature-variable small-angle X-ray diffraction studies that each of the polymers 10 showed a helical Col[Formula: see text] (helical tetragonal columnar) structure. The helical Col[Formula: see text] phase structure may be able for use in organic electroluminescent devices and solar cells in the future.

Thermomechanically controlled fluorescence anisotropy in thin films of InP/ZnS quantum dots.

Macroscopic scale sources of polarized light play a fundamental role in designing light-emitting devices. In this communication we report the formation of nano- and macro-scale ordered, layered assemblies of InP/ZnS quantum dots (QDs) exhibiting fluorescence anisotropy (FA), as well as thermo- and mechano-responsive properties. The long-range organization of small, quasi-isotropic nanoparticles was achieved by introducing liquid crystal molecules to the surface of QDs, without the need to use an organic matrix. Melting/crystallization of the ligand at 95 deg. C translated to a reversible reconfiguration of QDs thin film between 2D layered and body-centered cubic structures, characteristic for a temperature range below and above the melting point, respectively. The low-temperature, layered structure exhibited mechano-responsiveness which was key to introduce and control the sample alignment. Interestingly, transverse and parallel alignment modes of QDs layers were achieved, depending on the temperature of mechanical shearing. As prepared QD samples exhibited fluorescence anisotropy strongly correlated to the macroscopic orientation of the layers. Correlated small-angle X-ray diffraction (SAXRD) and fluorescence spectroscopy studies confirmed the mm-scale alignment of the thin films of QDs. Such films may be advantageous for developing efficient, densely packed, and uniform macro-scale FA sources.

Microstructural Changes during Degradation of Biobased Poly(4-hydroxybutyrate) Sutures.

Fibers of poly(4-hydroxybutyrate) (P4HB) have been submitted to both hydrolytic and enzymatic degradation media in order to generate samples with different types and degrees of chain breakage. Random chain hydrolysis is clearly enhanced by varying temperatures from 37 to 55 °C and is slightly dependent on the pH of the medium. Enzymatic attack is a surface erosion process with significant solubilization as a consequence of a preferent stepwise degradation. Small angle X-ray diffraction studies revealed a peculiar supramolecular structure with two different types of lamellar stacks. These were caused by the distinct shear stresses that the core and the shell of the fiber suffered during the severe annealing process. External lamellae were characterized by surfaces tilted 45° with respect to the stretching direction and a higher thickness, while the inner lamellae were more imperfect and had their surfaces perpendicularly oriented to the fiber axis. In all cases, WAXD data indicated that the chain molecular axis was aligned with the fiber axis and molecules were arranged according to a single orthorhombic structure. A gradual change of the microstructure was observed as a function of the progress of hydrolysis while changes were not evident under an enzymatic attack. Hydrolysis mainly affected the inner lamellar stacks as revealed by the direct SAXS patterns and the analysis of correlation functions. Both lamellar crystalline and amorphous thicknesses slightly increased as well as the electronic contrast between amorphous and crystalline regions. Thermal treatments of samples exposed to the hydrolytic media revealed microstructural changes caused by degradation, with the inner lamellae being those that melted faster.

Penetration Process of a Hydrated Deep Eutectic Solvent Through the Stratum Corneum and its Application as a Protein Penetration Enhancer.

The penetration mechanism of choline chloride‐glycerol deep eutectic solvent (DES) through the stratum corneum (SC) as a potential solvent for a novel enhancer of protein penetration into the skin was investigated in a wide and small angle X‐ray diffraction study. We found that DES penetrated through intercellular lipids but not the corneocytes. DES seemed to extract a portion of lipids of the short lamellae in the SC. Hydrated DES with a DES to water weight ratio of 9 to 1 (9DES‐1H2O) showed the strongest interaction with the lipids in the SC compared with water, DES, and hydrated DESs with another weight ratio of DES to water (DES : water=8 : 2). In a skin penetration test with a fluorescently labelled lysozyme, 9DES‐1H2O increased the amount of penetration through the SC by two‐fold compared with HEPES buffer.

Development of lecithin and stearic acid based oleogels and oleogel emulsions for edible semisolid applications

The objective of this study was to characterize a novel soy lecithin (SL) based oleogel (LOG) and oleogel emulsion (LOGE) prepared with different proportions of stearic acid (SA). Oleogels were developed with 1 wt% of water, and two gelator concentrations (20 wt% and 30 wt%) with SL:SA ratios (0:10, 3:7, 5:5, 7:3, 10:0). The same SL:SA proportions were used to prepare LOGE with 10 wt% and 20 wt% of water. Small (SAXD) and wide (WAXD) angle x-ray diffraction studies and polarized light microscopy were conducted to determine the nano- and microstructure of the samples. The hardness of the samples was analyzed using a texture analyzer and the thermal properties with a differential scanning calorimeter. The results indicate that LOG were primarily formed through the entanglement of bundles of reverse worm-like micelles of SL; however, LOGE were structured mainly through SA crystals that interacted in a synergistic fashion with the SL reverse micelles network to stabilize the three dimensional network. The hardness of the LOG and LOGE increased with an increase in SA, however, in samples containing both SL and SA, LOGE were harder than LOG, demonstrating that the oleogelators have a synergistic effect. The novel hybrid LOG and LOGE formulated with SA can be used as a more stable alternative to SL oleogels particularly when the objective is to achieve semi-solid characteristics.

Sarcomeric perturbations of myosin motors lead to dilated cardiomyopathy in genetically modified MYL2 mice

Dilated cardiomyopathy (DCM) is a devastating heart disease that affects about 1 million people in the United States, but the underlying mechanisms remain poorly understood. In this study, we aimed to determine the biomechanical and structural causes of DCM in transgenic mice carrying a novel mutation in the MYL2 gene, encoding the cardiac myosin regulatory light chain. Transgenic D94A (aspartic acid-to-alanine) mice were created and investigated by echocardiography and invasive hemodynamic and molecular structural and functional assessments. Consistent with the DCM phenotype, a significant reduction of the ejection fraction (EF) was observed in ∼5- and ∼12-mo-old male and female D94A lines compared with respective WT controls. Younger male D94A mice showed a more pronounced left ventricular (LV) chamber dilation compared with female counterparts, but both sexes of D94A lines developed DCM by 12 mo of age. The hypocontractile activity of D94A myosin motors resulted in the rightward shift of the force-pCa dependence and decreased actin-activated myosin ATPase activity. Consistent with a decreased Ca2+ sensitivity of contractile force, a small-angle X-ray diffraction study, performed in D94A fibers at submaximal Ca2+ concentrations, revealed repositioning of the D94A cross-bridge mass toward the thick-filament backbone supporting the hypocontractile state of D94A myosin motors. Our data suggest that structural perturbations at the level of sarcomeres result in aberrant cardiomyocyte cytoarchitecture and lead to LV chamber dilation and decreased EF, manifesting in systolic dysfunction of D94A hearts. The D94A-induced development of DCM in mice closely follows the clinical phenotype and suggests that MYL2 may serve as a new therapeutic target for dilated cardiomyopathy.

MCM-41-supported NNO type Schiff base complexes: a highly selective heterogeneous nanocatalyst for esterification, Diels–Alder and aldol condensation

Solid catalysts have been synthesized by anchoring transition metal complexes into organically modified MCM-41. First, the surface of Si-MCM-41 was modified with 3-aminopropyl-triethoxysilane (3-APTES), the imine group of which upon condensation with DFP (4-methyl-2,6-diformylphenol) affords a N2O-type Schiff base moiety in the mesoporous matrix. The Schiff base moieties were used to anchor Ni (II) and Cu (II) ions. The prepared catalyst have been characterized by DRS (Diffuse Reflectance Spectroscopy), FTIR (Fourier transform infrared) spectroscopy, small-angle X-ray diffraction (SAX), FESEM (Field Emission Scanning Electron Microscope), EDX (Energy-dispersive X-ray spectroscopy) and nitrogen sorption studies. The decrease of crystallinity in the multistep synthesis procedure, as evidenced by SAX (Small-angle X-ray) measurements, was observed. The prepared materials proved to be efficient catalysts for organic transformations such as esterification, Diels–Alder and Aldol condensation at ambient conditions. The immobilized complex does not leach or decompose during the catalytic reactions, showing practical advantages over the free metal complex.

Structural properties of paeonol encapsulated liposomes at physiological temperature: Synchrotron small-angle and wide-angle X-ray diffraction studies

Structural properties of paeonol encapsulated liposomes at physiological temperature: Synchrotron small-angle and wide-angle X-ray diffraction studies

Thickness Effect On Nano-multilayered Sb/As2S3 Chalcogenide Thin Films

The nano multilayered thin films of Sb/As2S3 metal chalcogenide were prepared by thermal evaporation technique under high vacuum. The optical parameters such as optical band gap, tauc parameter, urbach energy were determined from the transmission spectra using Fourier Transform Infrared Spectroscopy. These properties are greatly influenced by the thickness of the nano layered Sb/As2S3 thin film. The Small Angle X-ray diffraction study reveals the amorphous nature of these films. The analysis reveals that the optical band gap decreases with increase in thickness due to Sb metal. The tauc parameter and urbach energy supports the optical property change. Such type of dependence is attributed to quantum size effect in semiconductors.

Dimer conformation of soluble PECAM-1, an endothelial marker

Platelet endothelial cell adhesion molecule 1 (PECAM-1) is a cell surface receptor widely distributed on endothelium and hematopoietic-derived cells, and maintain the integrity of the blood vessels. PECAM-1 is widely recognized as an endothelial cell marker. The homophilic interaction through its extracellular domain of PECAM-1 (soluble PECAM-1, or sPECAM-1) is important to its functions. However, structural details for such dimerization are not fully understood. Here we report the production of recombinant sPECAM-1 in large quantity by Drosophila expression system and the small-angle X-ray diffraction (SAXS) study. The recombinant sPECAM-1 was found to form one population of dimer, but not oligomer, and was able to bind to heparin immobilized on a chip in surface plasmon resonance imaging (SPRi) binding experiments. The results of SAXS demonstrated that sPECAM-1 formed a symmetric homodimer of Ω-shape in solution, and each protomer adopted an extended conformation. The dimer is mediated through the intermolecular interactions through the first N-terminal domain (D1) of sPECAM-1. This model provides new structural information for its homophilic interaction mechanism.

DOPC-DOPE composition dependent Lα-HII thermotropic phase transition: SAXD study

The structural polymorphism and parameters of lyotropic phases formed in the mixed dioleoylphosphatidylcholine-dioleoylphosphatidylethanolamine (DOPC-DOPE) system upon heating and varying DOPC:DOPE composition were studied by means of small-angle X-ray diffraction (SAXD). In the temperature range 5–80°C a sequence of fluid lamellar Lα – inverse hexagonal HII – inverse cubic QII phases was detected at DOPE mole fractions XDOPE≥0.65. A superposition of two bicontinuous cubic QII phases of Pn3m and Ia3d space groups was identified. The Lα to HII phase transition temperature, the onset of the QII phase formation, as well as the lattice spacings of the Lα and HII phases were found to decrease with rising DOPE content. Moreover, evidence of structural rearrangement during the Lα to HII phase transition is given and change of transition mechanism with varying XDOPE is suggested.

Development of Physiologic versus Pathologic Hypertrophy in Mouse Models Expressing Mutations in Myosin Essential Light Chain

Mechanisms and signaling pathways underlying physiologic vs. pathological cardiac remodeling were investigated using transgenic Δ43, A57G and E143K mice expressing mutations in myosin essential light chain (ELC). In Δ43-hearts, the endogenous mouse ventricular-ELC is partially replaced with the N-terminal 43-amino-acid truncated human-ELC. The A57G (Alanine→Glycine) mutation was found to cause hypertrophic (HCM), while E143K (Glutamate→Lysine), restrictive cardiomyopathy (RCM). The hearts of Δ43-mice hypertrophy with age, but the ventricles do not show pathological remodeling or morphology vs. WT mice. In contrary, severe phenotypes were observed in Masson's trichrome-stained heart sections of HCM- and RCM-models. EM evaluation revealed abundant mitochondria in A57G-HCM and profound sarcomere defects (distorted Z- and M- lines) in E143K-RCM hearts. Normal in vivo function was recorded in Δ43-mice, but systolic and diastolic abnormalities were noted in HCM and RCM hearts. Functional studies showed elevated (E143K) or reduced (A57G) contractile force and increased Ca2+-sensitivity in RCM/HCM models vs. WT, but no change in Δ43-mice. Small-angle X-ray diffraction study showed decreased lattice spacing in pathological models of hypertrophy, but no changes in the physiological phenotype. Proteomic investigation using tandem-mass-tag-labeling showed changes in metabolic and cellular processes in all three phenotypes vs. WT and differential protein expression between physiologic and pathologic heart models. Compared with Δ43, E143K-RCM hearts showed upregulation of structural proteins, myomesin-1 and LIM-protein2, while Ca2+-binding proteins, sarcalumenin and mitochondrial protein Aralar1 were upregulated in A57G-HCM. Comparison of RCM and HCM hearts revealed upregulation of L-lactate dehydrogenase-B and isocitrate dehydrogenase-[NAD]-alpha, and downregulation of inorganic pyrophosphatase-2 in E143K vs. A57G hearts. In conclusion, in contrast to the physiologic model of hypertrophy, HCM and RCM mice show severe structural and metabolic abnormalities that trigger development of pathological hypertrophy and alter function. Supported by NIH-HL108343 (DSC).

Reversible switching of structural and plasmonic properties of liquid-crystalline gold nanoparticle assemblies.

Hybrid materials built of spherical gold nanoparticles with three different sizes covered with (pro)mesogenic molecules have been prepared. Small-angle X-ray diffraction studies showed that after thermal annealing most of the obtained materials formed long-range ordered assemblies. Variation of the (pro)mesogenic ligand architecture enabled us to achieve a switchable material, which could be reversibly reconfigured between 3D long-range ordered structures with tetragonal and face centred cubic symmetries. This structural reconfiguration induces changes to the plasmonic response of the material. This work demonstrates that it is possible to use LC-based self-assembling phenomena to prepare dynamic materials with structural properties important for the development of active plasmonic metamaterials.

The location of coenzyme Q10 in phospholipid membranes made of POPE: a small-angle synchrotron X-ray diffraction study.

The location of coenzyme Q10 (Q10) inside the inner mitochondrial membrane is a topic of research aiming at a deeper understanding of the function of the mitochondrial respiratory chain. We investigated the location of Q10 inside model membranes made of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine by means of small-angle synchrotron X-ray diffraction. Q10, which stands for ubiquinone-10 (UQ) or ubihydroquinone-10 (UH), did not remarkably influence the main phase transition temperature, but significantly decreased the lamellar-inverse hexagonal phase transition temperature (T(h)). The effect of UH on T(h) was stronger than the effect of UQ and the effect of liquid Q10 on T(h) was stronger than the effect of crystalline Q10. In the presence of Q10, the lattice parameters of the lamellar phases remained unchanged, whereas the H II lattice parameter was clearly influenced: While UQ had an increasing effect, UH had a decreasing effect. Furthermore, Q10 prevented the formation of cubic phases. The results give new evidence that the headgroup of Q10 is distant from the center of the membrane, which might be important for the function of the mitochondrial respiratory chain.

Liposome-based gene delivery systems containing a steroid derivative: computational and small angle X-ray diffraction study

The structural properties and the phase behaviour of mixed composition liposomes containing a functionalized lipid are investigated with the aim to design neutral liposomes able to coordinate metals and to complex DNA.

The effect of preliminary delamination of silicate filler on its exfoliation degree in polyvinyl alcohol/montmorillonite nanocomposites

It is found that the preliminary delamination of the silicate filler allows one to achieve its high degree of exfoliation in the process of preparing polymer/layered silicate nanocomposites. It is shown using the example of various forms of montmorillonite, such as natural, intercalated with large [A113O4(OH)24(H2O)12]7+ Keggin ions, and pillared, that polyvinyl alcohol/montmorillonite nanocomposite films show much higher strength characteristics in the case of using a delaminated silicate component. According to the data of small angle X-ray diffraction studies, the almost complete exfoliation of silicate layers is observed, particularly for delaminated forms of montmorillonite. The thermal stability of the composites slightly decreases in comparison with pure PVA.

Size Limit on the Formation of Periodic Mesoporous Organosilicas (PMOs)

The decrease of the lattice size of periodic mesoporous organosilicas (PMOs) is one important goal in obtaining a microporous material for storage or adsorption of small molecules. To determine the influence of different synthesis parameters in the lattice size, here we performed in situ small-angle X-ray diffraction studies and show that a variation of the surfactant's headgroup size is not directly followed by the lattice parameter of the resulting structure. We show that in the surfactant series of penta-, hexa-, hepta-, octa-, nona-, and decaethylene glycol monododecyl ether (C12(EO)n, n = 5, 6, 7, 8, 9, 10) the lattice size decreases between n = 5 and n = 8 and then increases, while the ordering of the materials is always cubic (space group Fd3m). This size effect is due to the ethylene oxide (EO) chain conformation that changes as the number of EO groups increases. Short ethylene oxide chains tend to have a so-called "zigzag" conformation while an increase of the chain length leads to a "Mäander" (coiling) conformation. Although this phenomenon is most commonly observed for chains consisting of more than 10 ethylene oxide units, we found a minimum PMO lattice size for 8 EO units and intermediate values for 6 and 7 EO units. The increase of the lattice parameter for more than 9 EO units is attributed to the increasing number of "Mäander" configurated EO units.

Surfactant Gel Extraction of Metal Ammine Complexes using SDS and KCl at Room Temperature, and a Small-angle X-ray Diffraction Study of the Surfactant Phase

Micellar solutions of sodium dodecylsulfate (SDS) exhibit the property of being separated into two phases as a result of a temperature change or the addition of salts. Upon addition of KCl to an SDS solution, the surfactant phase of Na+DS- changed to the potassium dodecylsulfate phase of K+DS- (KDS) at room temperature around 25°C. The ammine complexes of metal ions such as copper reacted with the dodecylsulfate anion (DS-) to form the corresponding ion pair, and were separated from the solution as the surfactant phase. After the phase separation of the solution containing SDS, KCl, ammonia, and copper, the surfactant phase consisted of KDS and the ion pair of [Cu(NH3)42＋](DS-)2 (abbreviated CuDS). The structures of the surfactant phases were investigated by small-angle X-ray diffraction (SAXRD) and differential scanning calorimetric measurements. The surfactant phases had lamellar structures with layer distances (d(001)) of 3.4 nm for KDS and 2.4 nm for CuDS. This surfactant gel extraction method was applied to the mutual separation of copper and zinc in a brass alloy. The extractability of the metals was regulated by the initial metal concentration in the sample solution. The percent extraction was (98.7 ± 0.6)% and (6.8 ± 1.4)% for copper and zinc, respectively.

Entanglement-based shape memory polyurethanes: Synthesis and characterization

In this paper, we report on the shape memory behavior of a family of hardblock-free multiblock thermoplastic polyurethanes (TPUs) consisting of poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG). Due to high molecular weight (Mn > 200 kDa), high degrees of entanglement were achieved. Instead of conventional “hard” blocks, entanglements served as the physical crosslinks in this system, slowing stress relaxation (suspending flow) above the melting temperatures of the soft blocks long enough to allow facile elastic deformation for shape fixing. Moreover, highly deformed samples (>800%) imparted by plastic deformation at room temperature completely recovered their as-cast shape within 1 min when heating above the transition temperature. Upon tensile deformation, the constituent chains and domains of both PCL and PEG phases became oriented, while heating-induced recovery reversed this orientation, as evidenced by wide-angle and small-angle X-ray diffraction studies. The observed large recoverable deformation and fast actuation make these materials strong candidates for applications in such medical devices as self-tightening sutures.