SAXS experiments on absolute scale with Kratky systems using water as a secondary standard

Orthaber, Doris; Bergmann, Alexander; Glatter, Otto

doi:10.1107/s0021889899015216

Cited by 587 publications

(614 citation statements)

References 36 publications

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“…Scattering data were first averaged and corrected for the solvent scattering and finally put on absolute scale using water as a secondary standard. 27 The SAXS data obtained in this way were still experimentally smeared because of the finite dimensions of the primary beam. 28 For further evaluation, the indirect Fourier transformation software package IFT 29 was used.…”

Section: Methodsmentioning

confidence: 99%

Solubilization of Poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} in Water by Nonionic Amphiphiles

et al. 2009

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In the presence of the nonionic alkyloxyethylene surfactant n-dodecylpentaoxyethylene glycol ether (C 12 E 5 ), the anionic conjugated polyelectrolyte (CPE) poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) dissolves in water, leading to a blue shift in fluorescence and dramatic increases in fluorescence quantum yields above the surfactant critical micelle concentration (cmc). No significant changes were seen with a poly(ethylene oxide) of similar size to the surfactant headgroup, confirming that specific surfactant-polyelectrolyte interactions are important. From UV-visible and fluorescence spectroscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), cryogenic transmission electron microscopy (cryo-TEM), and electrical conductivity, together with our published NMR and small-angle neutron scattering (SANS) results, we provide a coherent model for this behavior in terms of breakup of PBS-PFP clusters through polymer-surfactant association leading to cylindrical aggregates containing isolated polymer chains. This is supported by molecular dynamics simulations, which indicate stable polymer-surfactant structures and also provide indications of the tendency of C 12 E 5 to break up polymer clusters to form these mixed polymer-surfactant aggregates. Radial electron density profiles of the cylindrical cross section obtained from SAXS results reveal the internal structure of such inhomogeneous species. DLS and cryo-TEM results show that at higher surfactant concentrations the micelles start to grow, possibly partially due to formation of long, threadlike species. Other alkyloxyethylene surfactants, together with poly(propylene glycol) and hydrophobically modified poly(ethylene glycol), also solubilize this polymer in water, and it is suggested that this results from a balance between electrostatic (or ion-dipole), hydrophilic, and hydrophobic interactions. There is a small, but significant, dependence of the emission maximum on the local environment.

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Section: Methodsmentioning

confidence: 99%

Solubilization of Poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} in Water by Nonionic Amphiphiles

et al. 2009

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“…Data analysis was done with Fit2D [38] and Igor Pro (Version 6.22A, WaveMetrics Inc., Portland, OR, USA). Experimental intensities were background corrected, and absolute calibration was performed with water as the secondary standard using the method described by Orthaber [39].…”

Section: Saxsmentioning

confidence: 99%

Peptide self-assembly into lamellar phases and the formation of lipid-peptide nanostructures

et al. 2017

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Lipids exhibit an extraordinary polymorphism in self-assembled mesophases, with lamellar phases as the most relevant biological representative. To mimic lipid lamellar phases with amphiphilic designer peptides, seven systematically varied short peptides were engineered. Indeed, four peptide candidates (V 4 D, V 4 WD, V 4 WD 2 , I 4 WD 2 ) readily self-assembled into lamellae in aqueous solution. Small-angle X-ray scattering (SAXS) patterns revealed ordered lamellar structures with a repeat distance of ~ 4-5 nm. Transmission electron microscopy (TEM) images confirmed the presence of stacked sheets. Two derivatives (V 3 D and V 4 D 2 ) remained as loose aggregates dispersed in solution; one peptide (L 4 WD 2 ) formed twisted tapes with internal lamellae and an antiparallel β-type monomer alignment. To understand the interaction of peptides with lipids, they were mixed with phosphatidylcholines. Low peptide concentrations (1.1 mM) induced the formation of a heterogeneous mixture of vesicular structures. Large multilamellar vesicles (MLV, d-spacing ~ 6.3 nm) coexisted with oligo-or unilamellar vesicles (~ 50 nm in diameter) and bicelle-like structures (~ 45 nm length, ~ 18 nm width). High peptide concentrations (11 mM) led to unilamellar vesicles (ULV, diameter ~ 260-280 nm) with a homogeneous mixing of lipids and peptides. SAXS revealed the temperature-dependent fine structure of these ULVs. At 25 °C the bilayer is in a fully interdigitated state (headgroup-to-headgroup distance d HH ~ 2.9 nm), whereas at 50 °C this interdigitation opens up (d HH ~ 3.6 nm). Our results highlight the versatility of self-assembled peptide superstructures. Subtle changes in the amino acid composition are key design elements in creating peptide-or lipidpeptide nanostructures with richness in morphology similar to that of naturally occurring lipids.

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“…48. The SAXS pattern of pure double-distilled deionized water (Barnestead Nanopure, Thermoscientific, Waltham, MA) was measured by taking SAXS profiles of pure water and subtraction of a similarly normalized background curve (an empty clean sample holder).…”

Section: Absolute Calibration Using Water As Referencementioning

confidence: 99%

Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids

Nguyên

Pabit

Meisburger

et al. 2014

The Journal of Chemical Physics

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A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb + and Sr 2+ ) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein-Zernike equations, with results from the Kovalenko-Hirata closure being closest to experiment for the cases studied here. © 2014 AIP Publishing LLC. [http://dx

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SAXS experiments on absolute scale with Kratky systems using water as a secondary standard

Cited by 587 publications

References 36 publications

Solubilization of Poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} in Water by Nonionic Amphiphiles

Solubilization of Poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} in Water by Nonionic Amphiphiles

Peptide self-assembly into lamellar phases and the formation of lipid-peptide nanostructures

Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids

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