Grazing-incidence small-angle scattering (GISAS) is a scattering technique used to study nanostructured surfaces and thin films. The scattered probe is either photons (grazing-incidence small-angle X-ray scattering, GISAXS) or neutrons (grazing-incidence small-angle neutron scattering, GISANS). GISAS combines the accessible length scales of small-angle scattering (SAS: SAXS or SANS) and the surface sensitivity of grazing incidence diffraction (GID). A typical application of GISAS is the characterisation of self-assembly and self-organization on the nanoscale in thin films. Systems studied by GISAS include quantum dot arrays, growth instabilities formed during in-situ growth, self-organized nanostructures in thin films of block copolymers, silica mesophases, and nanoparticles. GISAXS was introduced by Levine and Cohen to study the dewetting of gold deposited on a glass surface. The technique was further developed by Naudon and coworkers to study metal agglomerates on surfaces and in buried ...
The 5-untranslated region of the hepatitis C virus genome contains an internal ribosome entry site (IRES) that initiates cap-independent translation of the viral RNA. Until now, the structural characterization of the entire (IRES) remained limited to cryo-electron microscopy reconstructions of the (IRES) bound to different cellular partners. Here we report an atomic model of free full-length hepatitis C virus (IRES) refined by selection against small-angle X-ray scattering data that incorporates the known structures of different fragments. We found that an ensemble of conformers reproduces small-angle X-ray scattering data better than a single structure suggesting in combination with molecular dynamics simulations that the hepatitis C virus (IRES) is an articulated molecule made of rigid parts that move relative to each other. Principal component analysis on an ensemble of physically accessible conformers of hepatitis C virus (IRES) revealed dominant collective motions in the molecule, which may
Coating metal nanocrystals with responsive polymers provides a model case of smart, functional materials, where the optical properties can be modulated by external stimuli. However the optical response is highly sensitive to the polymer shell morphology, thickness and dielectric contrast. In this paper we study the nature of cross-linked, thermoresponsive polymer shells for the first time using four different scattering approaches to elucidate the density profile of the shells. Each scattering method provides unique information about the temperature-induced changes of shell thickness in terms of hydrodynamic radius and radius of gyration, the pair-distance distribution functions of the shells as well as the dynamic network fluctuations. Only a combination of these different scattering techniques allows to develop a morphological model of the core-shell particles. We further demonstrate control of the cross-linker distribution in core-shell synthesis by semi-batch precipitation copolymerization. ...
The THO complex participates during eukaryotic mRNA biogenesis in coupling transcription to formation and nuclear export of translation-competent messenger ribonucleoprotein particles. In Saccharomyces cerevisiae, THO has been defined as a heteropentamer composed of the Tho2p, Hpr1p, Tex1p, Mft1p, and Thp2p subunits and the overall three-dimensional shape of the complex has been established by negative stain electron microscopy. Here, we use small-angle X-ray scattering measured for isolated THO components (Mft1p and Thp2p) as well as THO subcomplexes (Mft1p-Thp2p and Mft1p-Thp2p-Tho2p) to construct structural building blocks that allow positioning of each subunit within the complex. To accomplish this, the individual envelopes determined for Mft1p and Thp2p are first fitted inside those of the Mft1p-Thp2p and Mft1p-Thp2p-Tho2p complexes. Next, the ternary complex structure is placed in the context of the five-component electron microscopy structure. Our model reveals not only the position of ...
SSRL Structural Molecular Biology Group hosts a 3-day comprehensive workshop on the use of non-crystalline small-angle x-ray scattering and diffraction techniques in structural biology research ...
Small-angle X-ray scattering tensor tomography: Model of the three-dimensional reciprocal-space map, reconstruction algorithm and angular sampling ...
Benecke, G.; Wagermaier, W.; Li, C.; Schwartzkopf, M.; Flucke, G.; Hörth, R. M.; Zizak, I.; Burghammer, M.; Metwalli, E.; Müller-Buschbaum, P. et al.; Trebbin, M.; Förster, S.; Paris, O.; Roth, S. V.; Fratzl, P.: A customizable software for fast reduction and analysis of large X-ray scattering data sets: applications of the new DPDAK package to small-angle X-ray scattering and grazing-incidence small-angle X-ray scattering. Journal of Applied Crystallography 47, pp. 1797 - 1803 (2014 ...
in Macromolecules (1998), 31(13), 4240-4252. Twenty seven samples of carboxylato- and sulfonato-telechelic polyisoprenes associated with various cations (Na, K, Rb, Cs, Mg, Ca, Sr, and Ba) have been investigated by small-angle X-ray scattering. The ... [more ▼]. Twenty seven samples of carboxylato- and sulfonato-telechelic polyisoprenes associated with various cations (Na, K, Rb, Cs, Mg, Ca, Sr, and Ba) have been investigated by small-angle X-ray scattering. The Bragg spacing characteristic of the ionic peak is directly proportional to the root-mean-square end-to-end distance (rrms) of the polyisoprene chain. In the series of sulfonato-telechelic polyisoprenes, the Bragg spacing is approximately equal to rrms, whereas in the series of carboxylato-telechelic polyisoprenes it amounts to 21/2 rrms. It also appears that the ionic aggregates are more likely distributed according to a planar hexagonal network. An original method has been used for the tail-end analysis of the SAXS profile, which is ...
How about X-ray small angle scattering?. X-ray small-angle scattering experiments are possible with any beam size, however the lower q-limit will depend upon the beam size selected. Please contact beamline staff for details of the different possibilities. For example, the first order of dry collagen (65 nm) can be resolved using a 5 µm beam. Combined SAXS/WAXS experiments are feasible by an appropriate choice of detector-to-sample distance.. What type of sample supports are used?. Scanning setup: samples can be fixed on capillaries which are then mounted on a eucentric Huber goniometer head. Sample supports can include electron microscopy grids or small metal washers. Nevertheless, there is a high degree of flexibility for sample mounting and special sample environments can be discussed with beamline staff. Custom built cells for studying the influence of deformation, hydration and temperature change are mounted as a matter of routine.. What is the positioning accuracy of the scanning ...
Journal Article: Triglyceride nanocrystal aggregation into polycrystalline colloidal networks: Ultra-small angle X-ray scattering, models and computer simulation ...
A complex of the three (αεθ) core subunits and the β2 sliding clamp is responsible for DNA synthesis by Pol III, the Escherichia coli chromosomal DNA replicase. The 1.7 Å crystal structure of a complex between the PHP domain of α (polymerase) and the C-terminal segment of ε (proofreading exonuclease) subunits shows that ε is attached to α at a site far from the polymerase active site. Both α and ε contain clamp-binding motifs (CBMs) that interact simultaneously with β2 in the polymerization mode of DNA replication by Pol III. Strengthening of both CBMs enables isolation of stable αεθ:β2 complexes. Nuclear magnetic resonance experiments with reconstituted αεθ:β2 demonstrate retention of high mobility of a segment of 22 residues in the linker that connects the exonuclease domain of ε with its α-binding segment. In spite of this, small-angle X-ray scattering data show that the isolated complex with strengthened CBMs has a compact, but still flexible, structure. Photo-crosslinking with
SAXS is an analytical technique that measures the intensities of X-rays scattered by a sample as a function of the scattering angle. Measurements are made at very small angles, typically in the range of 0.1 deg to 5 deg.
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Overview of SAXS data and analysis. (a) Scattering curves for fH12-13 (red), fH11-14 (blue), and fH10-15 (yellow). Continuous lines represent fits obtaine
The Woodlands TX (PRWEB) February 15 2013 Rigaku Corporation introduces the new BioSAXS-1000 AUTO a leap forward for experimental biological SAXS (small angle X-ray scattering) workflow for the home lab. The BioSAXS-1000 AUTO combines Rigakus proven BioSAXS-1000 system with automatic sample handling automatic data collection and automatic data analysis for,Rigaku,introduces,the,worlds,most,comprehensive,biological,SAXS,system,for,the,home,lab,biological,advanced biology technology,biology laboratory technology,biology device technology,latest biology technology
The Woodlands TX (PRWEB) February 15 2013 Rigaku Corporation introduces the new BioSAXS-1000 AUTO a leap forward for experimental biological SAXS (small angle X-ray scattering) workflow for the home lab. The BioSAXS-1000 AUTO combines Rigakus proven BioSAXS-1000 system with automatic sample handling automatic data collection and automatic data analysis for,Rigaku,introduces,the,worlds,most,comprehensive,biological,SAXS,system,for,the,home,lab,biological,advanced biology technology,biology laboratory technology,biology device technology,latest biology technology
The thesis presents work regarding amphiphilic molecules associated in aqueous solution or at the liquid/solid interface. Two main topics are included: the temperature-dependent behavior of micelles and the adsorption of dispersants on carbon nanotube (CNT) surfaces. Various NMR methods were used to analyze those systems, such as chemical shift detection, spectral intensity measurements, spin relaxation and, in particular, self-diffusion experiments. Besides this, small angle X-ray scattering (SAXS) was also applied for structural characterization.. A particular form of phase transition, core freezing, was detected as a function of temperature in micelles composed by a single sort of Brij-type surfactants. In mixed micelles, that phase transition still occurs accompanied by a reversible segregation of different surfactants into distinct aggregates. Adding a hydrophobic solubilizate shifts the core freezing point to a lower temperature. Upon lowering the temperature to the core freezing point, ...
Moger, CJ, Barrett, R, Bleuet, P, Bradley, DA, Ellis, RE, Green, EM, Knapp, KM, Muthuvelu, P and Winlove, CP (2007) Regional variations of collagen orientation in normal and diseased articular cartilage and subchondral bone determined using small angle X-ray scattering (SAXS) ...
Leveraging the capabilities and expertise across the beamlines is designed to optimize the chances of successful structure determination for routine and challenging problems, said Paul Adams, director of Berkeley Labs Molecular Biophysics & Integrated Bioimaging (MBIB) division and principal investigator on the grant.. ALS-ENABLE has three technology operations cores to address specific needs: rapid response crystallography; high quality and high throughput small angle X-ray scattering; and specialized crystallography. For X-ray crystallography projects that are relatively straightforward, such as determining the position of different small molecules bound to the same protein, a fully automated pipeline will be put in place. Users samples will be mounted at the beamline by robots, the diffraction data will be automatically collected and processed, and the researchers hope that the structure will be automatically solved. It will be completely hands-off, which will significantly increase ...
The fabrication of molecular gas sieving materials with specific affinities for a single gas species and able to store large quantities of materials at a low or atmospheric pressure is desperately required to reduce the adverse effects of coal and oil usage in carbon capture. Fundamental understanding of the dynamic adsorption of gas, the diffusion mechanisms across thin film membranes, and the impact of interfaces play a vital role in developing these materials. In this work, single gas permeation tests across micro-porous membrane materials, based on metal organic framework crystals grown on the surface of carbon nanotubes ([email protected]), were performed for the first time in-situ at the Australian Synchrotron on the small angle X-ray scattering beamline in order to reveal molecular sieving mechanisms and gas adsorption within the material. The results show that specific chemi-sorption of CO2 across the ZiF-8 crystal lattices affected the morphology and unit cell parameters, while the sieving of other
The domain structure and miscibility in the solid state of a series of blends of styrene-butadiene-styrene (SBS) block copolymers and styrene-glycidyl methacrylate (PS-GMA) statistical copolymers with varying molecular weights and compositions were studied using small angle X-ray scattering and dynamic mechanical thermal analysis. Depending on the molecular characteristics of each component, different types and degrees of solubilization of PS-GMA in SBS were found which, in addition to the initially SBS phase morphology, lead to materials with multiphase domain morphologies with differences in size and structure. The degree of solubilization of PS-GMA into the PS domains of SBS was found to be higher for blends containing PS-GMA with lower molecular weight (M-w = IS 100 g mol(-1)) and lower GMA content (I wt%) and/or for SBS with higher PS content (39 wt%) and longer PS blocks (Mw = 19 600 g mol(-1)). Localized solubilization of PS-GMA in the middle of PS domains of SBS was found to be the most ...
The research group determines crystal structures of large single proteins, protein-protein complexes, and protein-RNA complexes, and we have determined several structures in the 60-350 kDa range. We validate our structures with biophysical and functional experiments. In addition we also use small angle x-ray scattering to study the molecules in solution. Our projects are focused on studying innate immunity, in particular how it recognizes danger signal on pathogens or damaged self-tissue and the response to the perception of such danger signals. An important component in the innate immune system is the complement system, formed by more than 50 soluble and membrane bound proteins. The soluble proteins are present in extracellular fluids, while the membrane proteins are located in membranes surrounding many of our cells, where they transmit the extracellular danger signal into intracellular signaling, protect our own cells from complement, and contributes to clearance of pathogens and host cells ...
Aiming to gain in-depth knowledge about the mechanisms involved in ABL control in normal cells, a group led by Dr. Jerson Silva at the Federal University of Rio de Janeiro, Brazil, used small angle X-ray scattering, nuclear magnetic resonance, and confocal microscopy to investigate the dynamics of the entire ABL regulatory unit. The study, published in The Journal of Biological Chemistry, shows that activation of the protein releases intramolecular interactions between a regulatory unit found in the N-terminal region of the ABL, the so-called N Cap, and a number of molecular modules, and pushes ABL to anchor on the cell membrane. The whole complex undergoes motions lasting micro- to milliseconds that ultimately result in the death of the cell ...
Type 1 plant metallothioneins (MTs) are low molecular weight (7-8 kDa), sulphydryl-rich, aromatic residue lacking, metal-binding proteins with two terminal metal-binding clusters separated by a long hinge region of about 50 amino acids. The length and conserved sequences in the hinge region distinguish type 1 MTs from their mammalian counterparts, suggesting additional roles other than metal binding and detoxification. Homology modeling of a Cd-binding durum wheat MT (dMT) indicates mammalian-like folds for the metal-binding domains, and ab initio calculations yield a DNA-binding like structural motif for the hinge region. Here, we study the structural features of full-length dMT in metal-free (apo) and metal-bound (holo) states using various biophysical and biochemical techniques. Cd-bound dMT is expressed in Escherichia coli as a GST fusion protein and cleaved from this tag for further analyses. Small angle X-ray solution scattering measurements and gel-filtration chromatography revealed ...
The SIBYLS beamline has recently been awarded 50,000 hours on the NERSC (National Energy Research Scientific Computing Center) to perform solution structure modeling using experimental SAXS data. Besides the usual ab-initio reconstructions programs a new approach in rigid body modeling BILBOMD has been parallelized on the NERSC supercomputer. It is commonly acknowledged that flexibility between domains of proteins is often critical for function. These motions, and proteins with large scale flexibility in general, are often not readily amenable to conventional structural analysis such as X-ray crystallography, NMR, or electron microscopy. We have developed an analysis tool using experimental SAXS measurements to identify flexibility and validate a constructed minimal ensemble of models which represent highly populated conformations in solution. The resolution is sufficient to address questions about the extent of the domain conformational sampling in solution? In our rigid body modeling strategy ...
A 2-year post-doctoral position funded by the EpiGenMed Labex program is available to work in the "Highly Flexible Proteins" group lead by Pau Bernadó at the Centre de Biochime Structurale (CBS) in Montpellier (France).. Project: The project focuses in deciphering the structural bases of the regulation of Nuclear Receptor gene transcription by Intrinsically Disordered co-regulator proteins. This is an interdisciplinary project that will be performed in collaboration with other groups at the CBS including the crystallography of Nuclear Receptors (William Bourguet) and molecular simulations (Alessandro Barducci) groups. Nuclear Magnetic Resonance (NMR) will be the main experimental technique used to develop the project. NMR will be combined with Small-Angle X-ray Scattering (SAXS), computational approaches and other biophysical techniques.. Candidate: The successful candidate should have a PhD in chemistry, biology or physics and a solid background in solution state biomolecular NMR spectroscopy. ...
Naturally occurring proteins-chains of amino acids that fold into functional, three-dimensional shapes-are believed to represent just a small fraction of the universe of all possible permutations of amino-acid sequences and folds. How can we begin to systematically sift through those permutations to find and engineer from scratch (de novo) proteins with the characteristics desired for medical, environmental, and industrial purposes? To address this question, a team led by researchers from the Institute for Protein Design at the University of Washington have published a landmark study that used both protein crystallography and small-angle x-ray scattering (SAXS) at the ALS to validate the computationally designed structures of novel proteins with repeated motifs. The results show that the protein-folding universe is far larger than realized, opening up a wide array of new possibilities for biomolecular engineering.. ...
DNA in vivo is principally found in a highly condensed state within chromosomes, viruses, and bacterial nucleoids often packaged via multivalent cations. Despite the critical role that the condensed DNA in chromosomes plays on gene expression and DNA replication within eukaryotic cells, the dominant molecular forces which drive this condensation are not fully understood. In recent years, new theories have been proposed to explain DNA-DNA attractive forces which lead to condensation but experimental data capable of distinguishing between these theories has been sorely lacking. We have used osmotic stress coupled with small-angle X-ray scattering (SAXS) to probe the magnitude and dependence of the thermodynamic forces between condensed DNA helices.\\\\ This talk will be divided between two topics. In the first part, I will discuss force measurements on condensed DNA arrays in the presence of cations ranging from simple ions to complex real proteins. Using homologous polycations, we have measured ...
Aichmayer, B.; Margolis, H. C.; Sigel, R.; Yamakoshi, Y.; Simmer, J. P.; Fratzl, P.: The onset of amelogenin nanosphere aggregation studied by small-angle X-ray scattering and dynamic light scattering. Journal of Structural Biology 151 (3), S. 239 - 249 (2005 ...
(2018) Lutz-Bueno et al. Journal of Applied Crystallography. In most cases, the analysis of small-angle and wide-angle X-ray scattering (SAXS and WAXS, respectively) requires a theoretical model to describe the samples scattering, complicating the interpretation of the scattering resulting from ...
The Coherent X-ray Scattering (CXS) group develops techniques in scanning- and time-resolved SAXS and high-resolution scanning X-ray microscopy at the cSAXS beamline. In collaboration with research groups, within PSI and international universities and research institutes, we apply these techniques to a wide range of problems in the fields of biology, biomedical research and materials science.
We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the [equation]cross section, generalizing...
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小角度和大角度X射线散射(SAXS和WAXS) X射线衍射(XRD)与小角度和大角度的X射线散射(SAXS和WAXS)是高科技、非破坏性分析法。可以分析范围广泛的材料,包括液体、金属、矿产品、聚合物、催化剂、塑料、陶瓷、医药、涂料薄膜和半导体。这些技术对于材料检测、表征和品质管理(QC)是不可或缺的。示例应用程序包括相分析、晶体结构和宽松分析、纹理分析和残余应力研究、纳米材料的研发和晶体多形筛选。不管在研究方面还是生产品质管理与工程方面,理学公司提供了与学术界用户和产业界用户合作开发的一系列的文书,这些文书是提供了最先进和性价比最高的X射线解决方案。 仪器 1288978522
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At first glance and at distance, the Surface Pro (2017) doesnt look different compared to the Surface Pro 3. The new 2-1 hybrid has the same form factor, overall design, and styling. Close-up is when one starts noticing the most obvious difference: smaller screen bezels all round, and therefore allowing for a screen with slightly larger display area: 12.0″ vs 12.3″. The significant differences thereafter are all under the hood and not visible to the naked eye.. The model I picked up was the i5/8GB RAM/256SSD - what many reviewers also note is the sweet spot for price-performance. And after 4 days of fairly intense use, my comments follow. Its mostly good with a few duhs?!?!.. The larger 12.3″ screen enjoys a beefier resolution of 2736×1824 vs 2160×144 in the SP3. But the latters screen was already dense enough at 216ppi. You really cant see the difference in the higher 267ppi in the SP (2017) unless you have eyes capable of seeing microscopic detail, nor are most people I reckon ...
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Ab inito reconstruction of a protein structure *** *** by a chain-like ensemble of dummy residues *** *** Version 2.2i build 21.06.06 *** *** Last modified --- 21/06/06 12:00 *** *** Please reference: D.I.Svergun, M.V.Petoukhov & *** *** M.H.J.Koch (2001) Biophys. J. 80, 2946-2953 *** *** Copyright (c) ATSAS Team *** *** EMBL, Hamburg Outstation, 2000 - 2005 *** Type gasbori /help for batch mode use === GASBOR Version 2.2i build 21.06.06 started on 06-Oct-2009 16:42:28 Computation mode (User or Expert) ...... , User ,: Log file name .......................... , .log ,: log Input data, GNOM output file name ...... , .out ,: 1trk.out Project identificator .................................. : log Enter project description .............. : project Random sequence initialized from ....................... : 164228 ** Information read from the GNOM file ** Data set title: Transketolase collated from n85, o14+o16 6-11-98 Raw data file name: trkexp.dat Maximum diameter of the particle ...
Small‑angle X‑ray scattering (SAXS) is a powerful method to gather quantitative nanoscale information from a diverse range of samples from liquids to pastes, powders, and films. The typical length scales probed range from ~1‑100 nm, corresponding well to the typical feature sizes of nanoparticles, block copolymers, and proteins. This versatility enables characterizations of diverse samples including nanoparticle solutions, nanocomposites, block copolymers, mesoporous materials, and protein solutions. Most SAXS experiments are carried out in transmission mode with the incident X--ray beam pointed directly at the sample. The scattered beam is then detected on the other side using a 2D area detector. The beam is sensitive to spatial variations in electron density and can scatter from any interface that has a change in electron density, such as polymer‑polymer, polymer‑solvent, protein‑solvent, or solid‑pore interfaces. The higher the contrast in electron density, the greater is the ...
Anne-Marie Caminade. 2.1 Introduction 35. 2.2 Spectroscopy and Spectrometry 36. 2.2.1 Nuclear Magnetic Resonance (NMR) 36. 2.2.2 Mass Spectrometry 40. 2.2.3 X-ray Diffraction 41. 2.2.4 Infrared (IR) and Raman Spectroscopy 42. 2.2.5 Ultraviolet-Visible (UV-vis) Spectroscopy 43. 2.2.6 Fluorescence 44. 2.2.7 Chirality, Optical Rotation, and Circular Dichroism (CD) 45. 2.2.8 Electron Paramagnetic Resonance (EPR) 45. 2.2.9 Electrochemistry 46. 2.2.10 Magnetometry 46. 2.2.11 Mössbauer Spectroscopy 46. 2.2.12 X-ray Spectroscopies 47. 2.3 Scattering Techniques 47. 2.3.1 Laser Light Scattering (LLS) 47. 2.3.2 Small-Angle Neutron Scattering (SANS) 47. 2.3.3 Small-Angle X-ray Scattering (SAXS) and. Wide-Angle X-ray Scattering (WAXS) 48. 2.4 Microscopy 48. 2.4.1 Transmission Electron Microscopy (TEM) 49. 2.4.2 Atomic Force Microscopy (AFM) 49. 2.4.3 Polarizing Optical Microscopy (POM) 50. 2.5 Rheology and Physical Characterizations 50. 2.5.1 Intrinsic Viscosity 50. 2.5.2 Differential Scanning Calorimetry ...
for magnetic scattering. Since these orbitals are typically of a comparable size to the wavelength of the free neutrons, the resulting form factor resembles that of the X-ray form factor. However, this neutron-magnetic scattering is only from the outer electrons, rather than being heavily weighted by the core electrons, which is the case for X-ray scattering. Hence, in strong contrast to the case for nuclear scattering, the scattering object for magnetic scattering is far from a point source; it is still more diffuse than the effective size of the source for X-ray scattering, and the resulting Fourier transform (the magnetic form factor) decays more rapidly than the X-ray form factor.[6] Also, in contrast to nuclear scattering, the magnetic form factor is not isotope dependent, but is dependent on the oxidation state of the atom. ...
Insulin-degrading enzyme (IDE) is a protease that cleaves insulin and other bioactive peptides such as amyloid-β. Knockout and genetic studies have linked IDE to Alzheimers disease and type-2 diabetes. As the major insulin-degrading protease, IDE is a candidate drug target in diabetes. Here we have used kinetic target-guided synthesis to design the first catalytic site inhibitor of IDE suitable for in vivo studies (BDM44768). Crystallographic and small angle X-ray scattering analyses show that it locks IDE in a closed conformation. Among a panel of metalloproteases, BDM44768 selectively inhibits IDE. Acute treatment of mice with BDM44768 increases insulin signalling and surprisingly impairs glucose tolerance in an IDE-dependent manner. These results confirm that IDE is involved in pathways that modulate short-term glucose homeostasis, but casts doubt on the general usefulness of the inhibition of IDE catalytic activity to treat diabetes. ...
Dr Chai Lor successfully defended his PhD thesis in the BEST (Bioengineering and small scale technologies) program on October 26th. Chai was a bioengineering undergraduate at UC Merced and a member of the first graduating class.. "Phase Behavior and Nanotube Formation in Lipid Membranes". Biological cells are protected by a complex barrier called the lipid membrane. The lipid membrane is a soft material structure consisting of many lipid molecules held together by hydrophobic forces in an aqueous solution. Two simple experimental models were employed to investigate the role of specific lipid molecules in biological membranes. The first model investigated the phase behavior of the binary lipid mixture, 1-dipalmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (DHA-PE) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), using small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS). Our results shows that DHA-PE induces phase separation into a DHA rich liquid ...
Dr Chai Lor successfully defended his PhD thesis in the BEST (Bioengineering and small scale technologies) program on October 26th. Chai was a bioengineering undergraduate at UC Merced and a member of the first graduating class.. "Phase Behavior and Nanotube Formation in Lipid Membranes". Biological cells are protected by a complex barrier called the lipid membrane. The lipid membrane is a soft material structure consisting of many lipid molecules held together by hydrophobic forces in an aqueous solution. Two simple experimental models were employed to investigate the role of specific lipid molecules in biological membranes. The first model investigated the phase behavior of the binary lipid mixture, 1-dipalmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (DHA-PE) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), using small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS). Our results shows that DHA-PE induces phase separation into a DHA rich liquid ...
The pH (Low) Insertion Peptides (pHLIP® peptides) find application in studies of membrane-associated folding, since spontaneous insertion of these peptides is conveniently triggered by varying pH. Here we employed small angle X-ray scattering (SAXS) to investigate WT pHLIP® peptide oligomeric state in solution at high concentrations and monitor changes in liposome structure upon peptide insertion into the bilayer. We established that even at high concentrations (up to 300 μM) WT pHLIP® peptide at pH 8.0 does not form oligomers higher than tetramers (which exhibit concentration-dependent transfer to monomeric state as it was shown previously). This finding has significance for medical applications, when high concentration of the peptide is injected into blood and diluted in blood circulation. The interaction of WT pHLIP® peptide with liposomes does not alter the unilamellar vesicle structure upon peptide adsorption by lipid bilayer at high pH or upon insertion across the bilayer at low pH. At the
article{d17966db-786f-4d12-a5f5-3a25a837ce80, abstract = {,p,Small-angle X-ray scattering (SAXS) measurements reveal a striking difference in intermolecular interactions between two short highly charged peptides - deca-arginine (R10) and deca-lysine (K10). Comparison of SAXS curves at high and low salt concentration shows that R10 self-associates, while interactions between K10 chains are purely repulsive. The self-association of R10 is stronger at lower ionic strengths, indicating that the attraction between R10 molecules has an important electrostatic component. SAXS data are complemented by NMR measurements and potentials of mean force between the peptides, calculated by means of umbrella-sampling molecular dynamics (MD) simulations. All-atom MD simulations elucidate the origin of the R10- R10 attraction by providing structural information on the dimeric state. The last two C-terminal residues of R10 constitute an adhesive patch formed by stacking of the side chains of two arginine residues ...