Peter Laggner - Academia.edu (original) (raw)

Papers by Peter Laggner

ABSTRACT Thermoplastic natural rubber sample is found isotropic based on SAXS pattern. Morphologi... more ABSTRACT Thermoplastic natural rubber sample is found isotropic based on SAXS pattern. Morphological parameter was obtained based on ideal lamellar morphology using 1-D correlation function. The fitting was carried out using Porod tail model and Vonk for back-extrapolated model. It is found that the long period value is 15.7nm which is comparable to results obtained from Lorents corrected profile, 20nm. Crystalline thickness and amorphous thickness was found as 13.4 and 2.31nm respectively. ABSTRAK Sampel getah asli termoplastik didapati isotropi berdasarkan corak SAXS. Parameter mofologikal diperolehi berdasarkan morfologi lamela unggul dengan menggunakan rangkap korelasi 1-D. Pemadanan dijalankan menggunakan ekor Porod model dan Vonk untuk belakang mengekstrapolasikan model. Ia didapati bahawa nilai jangka masa yang panjang ialah 15.7nm keputusan-keputusan setanding dengan yang mana diperolehi dari Lorents membetulkan profil, 20nm. Ketebalan berhablur dan ketebalan amorfus didapati kerana 13.4 dan 2.31nm masing-masing.

Biochemical Journal, 1984

$Research paper thumbnail of Time-Resolved X-Ray Diffraction on Lipid Bilayer Interactions Using Synchrotron Radiation$

Springer Series in Biophysics, 1987

The equilibrium properties of phospholipid phases have been extensively studied and are well docu... more The equilibrium properties of phospholipid phases have been extensively studied and are well documented (1). However, the present knowledge on mechanisms and rates of the transitions between the phases is relatively scarce. Conventional techniques for X-ray structure analysis operate the time scale of seconds and above, and thus are generally too slow to follow the transition processes in real-time.

Progress in Colloid & Polymer Science

The changes in inner structure of hydrating Portland cement paste during the process of hardening... more The changes in inner structure of hydrating Portland cement paste during the process of hardening were studied by small-angle x-ray scattering. The scattering curves taken at different times between 1 and 28 days after preparation showed two different decay exponents as demonstrated by the linear slopes in their log-log plots, related to the mass and surface fractal structure, respectively, of Portland cement. The time-course of the mass fractal dimension changes from an inkial value ofl.9 (day 1) to 2.8 (day 28); that of the surface fractal dimension remains almost constant around 2.8. This may indicate the development from a very ramified and porous structure to a more compact and homogeneous one by interlinking and space-filling the loose initial gel-network with solid calcium silicate hydrate and calcium hydroxide.

Proceedings of the National Academy of Sciences, 2000

In many biological membranes, the major lipids are “non-bilayer lipids,” which in purified form c... more In many biological membranes, the major lipids are “non-bilayer lipids,” which in purified form cannot be arranged in a lamellar structure. The structural and functional roles of these lipids are poorly understood. This work demonstrates that the in vitro association of the two main components of a membrane, the non-bilayer lipid monogalactosyldiacylglycerol (MGDG) and the chlorophyll-a/b light-harvesting antenna protein of photosystem II (LHCII) of pea thylakoids, leads to the formation of large, ordered lamellar structures: ( i ) thin-section electron microscopy and circular dichroism spectroscopy reveal that the addition of MGDG induces the transformation of isolated, disordered macroaggregates of LHCII into stacked lamellar aggregates with a long-range chiral order of the complexes; ( ii ) small-angle x-ray scattering discloses that LHCII perturbs the structure of the pure lipid and destroys the inverted hexagonal phase; and ( iii ) an analysis of electron micrographs of negativ...

Physica B: Condensed Matter, 2000

ABSTRACT An attempt is made to fit simultaneously SAXS and SANS patterns from ionic micellar solu... more ABSTRACT An attempt is made to fit simultaneously SAXS and SANS patterns from ionic micellar solutions. The results of the distinct SANS evaluation and that of the simultaneous one are in good agreement.

Molecular Biology Reports, 1992

X-ray small-angle diffraction, differential scanning calorimetry (DSC), and temperature scanning ... more X-ray small-angle diffraction, differential scanning calorimetry (DSC), and temperature scanning densitometry (TSD) were used to study the effect of b-lysin on the phase transitions of lipid assemblies from 1,2-0-dixehadecyl-sn-glycero-3-phosphoholine (DHPC). The experiments were carried out in excess of water in a temperature range of 0-55 ~ and at low peptide concentrations between 10-4 and 10-2 moles peptide per mole phospholipid. The incorporation of b-lysin into lipid assemblies alters the lipid structure without significant changes on the temperatures of phase transition from gel to liquid crystalline phase. The temperature of the main transition was nearly unaffected. A reduction in the transition volume of the lipids with increasing concentrations of b-lysin was observed. The minor changes in these parameters were interpreted as long-range structural changes caused by the peptide incorporation. The results are discussed in terms of the concept of cooperative phase transition of entire clusters occurring within a membrane implying that relative stable domains of gel phase, and liquid crystalline phase co-exist.

Journal of Membrane Biology, 2009

The currently accepted model of biological membranes involves a heterogeneous, highly dynamic org... more The currently accepted model of biological membranes involves a heterogeneous, highly dynamic organization, where certain lipids and proteins associate to form cooperative platforms (''rafts'') for cellular signaling or transport processes. Ceramides, a lipid species occurring under conditions of cellular stress and apoptosis, are considered to stabilize these platforms, thus modulating cellular function. The present study focuses on a previously unrecognized effect of ceramide generation. In agreement with previous studies, we find that ceramide leads to a depletion of sphingomyelin from mixtures with palmitoyl oleoyl phosphatidylcholine bilayers, forming a ceramide-sphingomyelin-rich gel phase that coexists with a fluid phase rich in palmitoyl oleoyl phosphatidylcholine. Interestingly, however, this latter phase has an almost fourfold smaller bending rigidity compared to a sphingomyelin-palmitoyl oleoyl phosphatidylcholine mixture lacking ceramide. The significant change of membrane bulk properties can have severe consequences for conformational equilibria of membrane proteins. We discuss these effects in terms of the lateral pressure profile concept for a simple geometric model of an ion channel and find a significant inhibition of its activity.

Journal of Macromolecular Science, Part B, 2002

Journal of Applied Crystallography, 1974

A high-density lipoprotein (HDL3) from porcine plasma was studied by small-angle X-ray scattering... more A high-density lipoprotein (HDL3) from porcine plasma was studied by small-angle X-ray scattering techniques. Experiments were conducted in the presence of different concentrations of sucrose, which was employed to raise the electron density of the solvent. The form of the scattering curves, and the well-resolved secondary maxima indicated a high degree of symmetry and/or particle homogeneity. Wide-angle studies confirmed the presence of highly mobile liquid-like hydrocarbon chains. The data allowed a calculation of the spherically-averaged electron-density distribution by Fourier inversion techniques. The range of experimentally determined scattering curves observed can be accounted for by a model for porcine HDL3 structure with the following features: a particle of radius of gyration 55 ~, comprising a central low electron density (lipid) core (radius 42/~) and an outer electron dense polar annulus (thickness 12 ~). By combining the X-ray data, and results from other studies, the probable location of the constituent molecular species can be suggested.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1993

Small-angle X-ray scattering was employed to show that the surface of soil particles is rough and... more Small-angle X-ray scattering was employed to show that the surface of soil particles is rough and scales as A cc rD= where A is the surface area of a given size fraction of radius r and D, is the surface fractal dimension (D, = 2.4 5 0.1). This relation has been confirmed by independent surface-area measurements on fractionated soil samples using nitrogen-gas adsorption and Methylene Blue adsorption from solution. These results bear an interesting relationship to recent size-distribution measurements of soil particles. The number of particles per unit volume with a radius larger than r has been shown to follow a power law N(r) CT reD where the exponent D is the fragmentation fractal dimension (D = 2.8 + 0.1). The power law is typically valid between two cutoff radii rl <<r-x rz with values around rr z 10-100 nm and r 2 z 10-5000 urn. The specific surface area of the unfractionated soil sample depends critically upon the position of the lower cutoff rl and can be accurately estimated from sizedistribution data and the knowledge of D,. These features can be related to a class of fragmented fractals which are characterized by the two fractal dimensions D and D,. These fractal dimensions obey the inequalities 2 < D, < D c 3 and 20,-D $2 which are also satisfied by the present experimental estimates, Keywords; Size distribution; soil particle; surface area. Recently, small-angle X-ray or neutron scattering techniques have revolutionized the study of inner surfaces in disordered and porous materials such as aerogels, silica gels, metallic glasses, polymer blends and cements [6-9). Such techniques often permit a decisive distinction between smooth and rough surfaces in such materials and, in favorable cases, even allow for direct specific surfacearea measurements [lo]. These methods seem likewise most attractive for the study of surface properties of natural submicroscopic colloids. A few exploratory applications on environmental

Biochimica et Biophysica Acta (BBA) - Biomembranes, 1991

The thermotropic phase behavior of mixtures between diradylphosphatidylethanolamines and diacylph... more The thermotropic phase behavior of mixtures between diradylphosphatidylethanolamines and diacylphosphatidylcholine was studied using polarized light microscopy, al P-NMR spectroscopy and synchrotron X-ray diffraction. Multilamellar liposomes composed of alkenylacylphosphatidylethanolamine (ethanolamine plasmalogen) undergo a phase transition from a lamellar to an inverse hexagonal lipid structure at 30°C, which is about 20 C ° and 30 C ° lower as compared to i~s alkyJacyl-and diacyl-analog, respectively. These results indicate a higher affinity to non-bilayer structures for the ether lipids. In the presence of the bilayer stabilizing pbospholipid, palmitoyloleoylphosphatidylcholine, the transition is shifted to higher temperature without any significant changes in the overall structural parameters as revealed by X-ray dilfraction experiments. Again, ethanolamine plasmalogen stabilizes the inverted hexagonal phase to the highest extent, i.e. even in the presence of 40 tool% palmitoyloleoylphosphatidyicholine a pure inverse hexagonal phase is formed at 60 o C. Such a result was not reported so far for a diacylphosphatidylethanolamine. This property of ethanulamine plasmalogen might be predominantly explained by an optimized packing of the hydrocarbon chains in the comers and interface region of the hexagonal tubes, owing to a different conformation of the sn-2 chain, which was deduced from

Aerosol Science and Technology, 2011

... 200518. Hampsey, EJ, Arsenault, S., Hu, Q. and Lu, Y. 2005. One-Step Synthesis of Mesoporous ... more ... 200518. Hampsey, EJ, Arsenault, S., Hu, Q. and Lu, Y. 2005. One-Step Synthesis of Mesoporous Metal-SiO2 Particles by an Aerosol-Assisted Self-Assembly Process. Chem. Mater. , 17: 2475–2480. [CrossRef], [Web of Science ®] View all references; Alonso et al. ...

Lipoproteins - Role in Health and Diseases, 2012

Biochemical Journal, 1976

The abnormal lipoproteins of the density range 1.019-1.063g/cm3 occurring in the plasma of patien... more The abnormal lipoproteins of the density range 1.019-1.063g/cm3 occurring in the plasma of patients with obstructive jaundice were studied. Subfractionation of this density class by combined sodium phosphotungstate precipitation, ultracentrifugation, and column chromatography on hydroxyapatite and agarose gel yielded essentially three fractions: (1) lipoprotein-X, (2) A triglyceride-rich lipoprotein for which we propose the term lipoprotein-Y and (3) an abnormal lipoprotein, lipoprotein-B. Marked differences between these fractions with respect to electron-microscopic appearance, hydrated densities, chemical composition and immunochemical characteristics were observed. The protein moiety of lipoprotein-X consisted primarily of apolipoprotein-C and albumin. Lipoprotein-Y showed, in addition to apolipoprotein-C, the presence of apolipoprotein-B. The ‘lipoprotein-B’ fraction isolated from sera of these patients had higher triglyceride and free cholesterol contents than that of normal i...

$Research paper thumbnail of Combing laser tweezer and micro-diffraction: new possibilities for in situ manipulation$

Acta Crystallographica Section A Foundations of Crystallography, 2007

Biophysical Journal, 1993

Amorphous state is intentionally (eg. amorphous solid dispersion) or unintentionally (induced by ... more Amorphous state is intentionally (eg. amorphous solid dispersion) or unintentionally (induced by processing) present in solid pharmaceutical intermediates and/or finished dosage forms.1 In either case, in-depth characterization of the structural properties of amorphous states is an important step towards prediction and control of the quality of final products such as dissolution performance and physical and chemical stability. Likewise, a thorough structural analysis of inherently amorphous macromolecule drugs (eg. protein) and polymeric excipients is inevitable to ensure their desired functionality.

Journal of Synchrotron Radiation, 1998

A new high-flux wiggler beamline for fast time-resolved small-angle X-ray scattering (SAXS) based... more A new high-flux wiggler beamline for fast time-resolved small-angle X-ray scattering (SAXS) based on double-focusing optics has recently commenced operation at the 2 GeV third-generation storage ring ELETTRA at Trieste, Italy. Its non-dispersive double-crystal monochromator contains three pairs of interchangeable asymmetrically cut flat Si(111)-crystal pairs, each of which is optimized for high throughput at one of the three fixed energies 5.4, 8 and 16 keV. To cope with the severe thermal power load produced by a 57-pole wiggler on the first crystal of each pair (up to 5.4 W mm−2 and 700 W under normal incidence, for 400 mA), grazing angles of 2° and optimized back-cooling have been chosen. This solution allows simultaneously a gain of 2.5–3.0 in throughput and, accordingly, in flux density. Finite-element analysis as well as commissioning tests showed that the cooling layout functions very satisfactorily, and that up to 5 × 1012 photons s−1 are available at the sample (at 8 keV an...

European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft für Pharmazeutische Verfahrenstechnik e.V, 2015

The purpose of this work was to investigate the influence of residual water in freeze-dried prote... more The purpose of this work was to investigate the influence of residual water in freeze-dried protein powders on the dissolution behavior of the solid-state proteins. To that end, six freeze-dried fibrinogen powder lots were stored at four levels of relative humidity and analyzed with regard to the particle size and shape, the specific surface area, the solid state of protein and the inner surface. Furthermore, the dissolution behavior of the powders was investigated. We clearly identified differences in the specific surface area, specific inner surface area, crystallinity, particle size and shape, which we were able to correlate to the dissolution behavior. These differences were triggered due to the different levels of residual moisture during two weeks of storage. Thus, we were able to show that the storage conditions have significant impact on the processing of pharmaceutical protein materials.