X-ray studies using synchrotron radiation

Ungar, Goran

doi:10.1007/978-94-011-1262-8_3

Cited by 5 publications

(3 citation statements)

References 101 publications

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“…These results show that C 246 H 494 chains form tight folds which comprise a surprisingly small segment of the alkane chain, an observation which agrees with data obtained from other experimental techniques. For example, SAXS measurements of the electron density profile normal to the lamella surface show that the width of the disordered interlayer increases only slightly between the E and F2 forms of C 246 H 494 . Similarly, infrared spectra of C 198 H 398 recorded at 110 K suggest a tight fold containing a significant proportion of gtg defects.…”

Section: Resultsmentioning

confidence: 99%

Chain Folding and Diffusion in Monodisperse Long n-Alkanes by Solid-State NMR

Grasso

Titman

2009

Macromolecules

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The size of the folded segment of the alkane chain in the integer-folded F2 form of C 246 H 494 has been measured directly by NMR and shown to contain an average of 8 ( 2 carbon atoms at 293 K. This tight fold is in contrast to the looser fold obtained indirectly for similar samples in earlier NMR work but in good agreement with the picture provided by SAXS and LAM Raman spectroscopy studies. The recovery after saturation of the carbon-13 magnetization associated with the all-trans carbon-13 peak has also been measured for recovery times as long as 4000 s. The behavior as a function of recovery time has been compared with simple simulations which model the combined effects of chain diffusion and spin-lattice relaxation. These results suggest that at short times the mechanism for the magnetization recovery involves the alkane chain diffusing around the fold with the methyl groups constrained from entering the crystal through the opposite surface of the lamella. Hence, only small fluctuations in the length of the fold segment occur, and the two linked stems move in a loosely co-operative fashion. Despite the tight fold, the rate of magnetization recovery is compatible with a frequency for the underlying chain jump process similar to that responsible for the R-relaxation in polyethylene.

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Section: Resultsmentioning

confidence: 99%

Chain Folding and Diffusion in Monodisperse Long n-Alkanes by Solid-State NMR

Grasso

Titman

2009

Macromolecules

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“…All SAXS experiments were performed on Station 2.1 at the Synchrotron Radiation Source (SRS) at the Daresbury Laboratory in the United Kingdom. The details of the storage ring, radiation and camera geometry, and data‐collection electronics have been described elsewhere 17, 18. The high‐intensity low‐divergence beam has a wavelength approximately that of Cu Kα radiation (λ = 1.52 Å) and is made monochromatic with a bent single crystal.…”

Section: Methodsmentioning

confidence: 99%

Dean Vortex Membrane Microfiltration and Diafiltration of rBDNF E.coliInclusion Bodies

Schutyser

Rupp

Wideman

et al. 2002

Biotechnology Progress

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Cross-flow microfiltration (CMF) and diafiltration were used to concentrate and purify recombinant Brain-Derived Neutrophic Factor (rBDNF) inclusion bodies from an E. coli cell suspension and a homogenized E. coli cell suspension (homogenate/lysate). Although these processes have been tested industrially in pilot scale with conventional linear membrane microfiltration modules, their performances were severely limited due to membrane fouling. The purpose of this work was to determine whether Dean vortex microfiltration with controlled centrifugal instabilities (Dean vortices produced in helical flow) could be used to improve filtration performance over that observed with conventional linear cross-flow microfiltration (CMF). For the microfiltration experiments with the feeds containing cell and homogenate suspensions, improvements in flux of about 50 and 70%, respectively, were obtained with the helical module as compared with that obtained with the linear module. For diafiltration with the homogenate suspension as feed, solute transport (as measured by mass) was from 100 to 40% higher after 40 and 100 min, respectively, with the helical module as compared with that obtained with the linear module. In the presence of the neutral surfactant, Tween 20, solute transport for diafiltration was at least 25 times higher during the first 10 min of operation and 100% higher after 300 min with the helical module as compared with that obtained with the linear module. Clearly, improved filtration performance, a purer and more concentrated product, and substantial savings can be expected with the new Dean vortex filters.

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“…For some time now, it has been demonstrated that SAXS data with a reasonable signal-to-noise ratio can be collected in subsecond frames (time slices) using synchrotron radiation sources. This makes real-time SAXS suitable for studies of the crystallization process in polymers and other materials . It would be ideal if similar real-time experiments could be carried out with SANS to supplement the information obtained by SAXS.…”

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confidence: 99%