CONSTRUCTION OF A SHEAR CELL FOR SAXS AND FREEZE FRACTURE STUDIES

Two variants of a sample holder were constructed for SAXS (small angle X-ray scattering) and freeze fracture studies of colloid systems during shear stress. The detailed construction of both variants is described. The SAXS investigations give information about the structural changes in the range of nm´s, and the freeze fracture technique makes possible the imaging of the \mum-scale morphology. Combining these methods the origin of certain macroscopical features, e.g. shear induced structural formations (like tixotropy) can be examined in a wide size range of the colloid dimensions

PREPARATION OF ACTIVATED CARBON FROM APRICOT PITS

The preparation of activated carbons from an ideal precursor is described in this paper. Activation was carried out with H2O in a rotating reactor or with a mixture of H2O and CO2 in a fluid reactor. The use of the fluid reactor has several industrial aspects. Adsorp- tion properties and the mesoporosity of the samples activated in the different apparatus are correlated with each other

Development of powder diffraction apparatus for small-angle X-ray scattering measurements

A novel type of X-ray collimation system attached to commercial powder diffractometers makes the structural characterization of nanomaterials possible in a wide size range from <0.1 to 100 nm by combination of the small- and wide-angle X-ray scattering techniques. There is no dead interval in the detection between the small- and wide-angle regimes. This device can be attached to any existing 'θ/θ' powder diffractometer, providing a multi-functional small- and wide-angle X-ray scattering/diffraction (SWAXS) apparatus. After proper alignment and adjustment, the device can be removed and re-attached at any time to switch between normal and SWAXS functions. Copyright © International Union of Crystallography 2013

Osmotic shrinkage of sterically stabilized liposomes as revealed by time-resolved small-angle X-ray scattering

Time-resolved synchrotron small-angle X-ray scattering (SAXS) was used to study the structural changes during the osmotic shrinkage of a pharmacologi- cally relevant liposomal drug delivery system. Sterically stabilized liposomes (SSLs) with a diameter of 100nm and composed of hydrogenated soy phosphocholine, cholesterol and distearoyl-phosphoethanolamine-PEG 2000 prepared in a salt-free buffer were mixed with a buffered 0.3 M NaCl solution using a stopped flow apparatus. The changes in the liposome size and the bilayer structure were followed by using SAXS with a time resolution of 20 ms. A linear decrease in liposome size is observed during the firs

Lytic and mechanical stability of clots composed of fibrin and blood vessel wall components.

Background Proteases expressed in atherosclerotic plaque lesions generate collagen fragments, release glycosaminoglycans (chondroitin sulfate [CS] and dermatan sulfate [DS]) and expose extracellular matrix (ECM) proteins (e.g. decorin) at sites of fibrin formation. Objective Here we address the effect of these vessel wall components on the lysis of fibrin by the tissue plasminogen activator (tPA)/plasminogen system and on the mechanical stability of clots. Methods and results MMP-8-digested collagen fragments, isolated CS, DS, glycosylated decorin and its core protein were used to prepare mixed matrices with fibrin (additives present at a 50-fold lower mass concentration than fibrinogen). Scanning electron microscopy (SEM) showed that the presence of ECM components resulted in a coarse fibrin structure, most pronounced for glycosylated decorin causing an increase in the median fiber diameter from 85 to 187 nm. Rheological measurements indicated that these structural alterations were coupled to decreased shear resistance (1.8-fold lower shear stress needed for gel/fluid transition of the clots containing glycosylated decorin) and rigidity (reduction of the storage modulus from 54.3 to 33.2 Pa). The lytic susceptibility of the modified fibrin structures was increased. The time to 50% lysis by plasmin was reduced approximately 2-fold for all investigated ECM components (apart from the core protein of decorin which produced a moderate reduction of the lysis time by 25%), whereas fibrin-dependent plasminogen activation by tPA was inhibited by up to 30%. Conclusion ECM components compromise the chemical and mechanical stability of fibrin as a result of changes in its ultrastructure

Effects of ursolic acid on the structural and morphological behaviours of dipalmitoyl lecithin vesicles.

Effects of ursolic acid on the structural and morphological characteristics of dipalmitoyl lecithin(DPPC)-water system was studied by using differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SWAXS), freeze-fracture method combined with transmission electron-microscopy (FF-TEM) and infrared spectroscopy (FT-IR). The surface of the uncorrelated lipid system is rippled or grained and a huge number of small, presumably unilamellar vesicles are present if the UA/DPPC molar ratio is 0.1mol/mol or higher. Besides the destroyed layer packing of regular multilamellar vesicles, non-bilayer (e.g. cubic or hexagonal) local structures are evidenced by SAXS and FF-TEM methods. The ability of UA to induce non-bilayer structures in hydrated DPPC system originates from the actual geometry form of associated lipid and UA molecules as concluded from the FT-IR measurements and theoretical calculations. Beside numerous beneficial e.g. chemopreventive and chemotherapeutic effect of ursolic acid against cancer, their impact to modify the lipid bilayers can be utilized in liposomal formulations

Toxikus és nehézfém ionok hatása modellmembrán rendszerekre = Effects of toxic molecules and heavy metal ions on modelmembran systems

A szerves és toxikus hatással rendelkező molekulák közül a diklór- és dibrómfenol, szulfadiazin, szteptomicin, tobramicin, spektinomicin, a Salmonella minnesota Re 595 mutáns törzséből előállított endotoxin, valamint a fémionok közül a Cu, Zn és Cd ionok szerkezetmódosító és szerkezetromboló hatását tanulmányoztuk a humán valamint a baktérimok membránjának lipidösszetételét megközelítő liposzómákban valamint szintén réteges szerkezetű nemionos/víz rendszerű modellrendszerekben. A vizsgálatok során kis és nagyszögű röntgenszórást, anomális röntgenszórást, kalorimetriát (DSC), fagyasztva törést követő transzmissziós elektronmikroszkópiát, valamint az eredmények interpretálásához kvantumkémiai, molekuladinamikai és szóráselméleti számításokat használtunk fel. Azonosítottuk a fenntiekben felsorolt molekulák koncentrációjának és a hőmérsékletnek a függvényében indukált, a vezikulák természetes kettősrétegétől való eltérő szerkezeti formáit (interdigitated =''egymásba tolt '' fázis, köbös és hexagonális, vagy ezek keverékeit, amorf formáit). Az anomális kisszögű szórás adta kivételes lehetőséget kihasználva megállapítottuk a fémionok liposzómákon belüli inhomogén eloszlását, valamint új típusú, a liposzómák interlamelláris terében való nanorészecske előállítási módot fedtünk fel. | The effects of the toxic 2,4-dichlorophenol, 2,4-dibromophenol, sulfadiazine, streptomycin, tobramycin, spectinomycin, LPS prepared from the rough mutant Salmonella minnesota Re 595 and the bivalent copper, zinc and cadmium ions on the different vesicle system consisting of phospholipids corresponding to the natural biomembranes were studies by means of small and wide angle X-ray scattering, anomalous small angle X-ray scattering , calorimetry (DSC), and freeze-fracture combined by transmission electronmicroscopy. Moreover, the interpretation of the results were completed with quantumchemical, molecular dynamical and scattering theoretical calculations. The different non-bilayer structures of lipids induced by LPS were identified. Using the unique possibility of the anomalous small angle X-ray scattering the inhomogeneous location of the bivalent metal ions was described and characterized. Applying the knowledge of the special location of the metal ions a new pathway of preparation for nanoparticles was revealed and proposed