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Université de Fribourg

Hard sphere-like glass transition in eye lens α-crystallin solutions

Foffi, Giuseppe ; Savin, Gabriela ; Bucciarelli, Saskia ; Dorsaz, Nicolas ; Thurston, George M. ; Stradner, Anna ; Schurtenberger, Peter

In: Proceedings of the National Academy of Sciences, 2014, vol. 111, no. 47, p. 16748–16753

We study the equilibrium liquid structure and dynamics of dilute and concentrated bovine eye lens α-crystallin solutions, using small-angle X-ray scattering, static and dynamic light scattering, viscometry, molecular dynamics simulations, and mode-coupling theory. We find that a polydisperse Percus–Yevick hard-sphere liquid-structure model accurately reproduces both static light scattering...

Université de Fribourg

Phase behaviour of colloids with short-range repulsions plus nonadsorbing polymer chains

Gruijthuijsen, Kitty van ; Tuinier, Remco ; Brader, Joseph M. ; Stradner, Anna

In: Soft Matter, 2014, vol. 9, no. 42, p. 9977–9982

The colloidal gas–liquid phase behaviour has been studied for aqueous mixtures of well-defined spherical particles with short-ranged repulsions mixed with relatively monodisperse poly(ethylene oxide) polymers. We show that our set of experimental phase diagrams are in quantitative agreement with theoretical predictions using generalized free volume theory [G. J. Fleer and R. Tuinier, Phys. Rev....

Université de Fribourg

Origin of suppressed demixing in casein/xanthan mixtures

Gruijthuijsen, Kitty van ; Herle, Vishweshwara ; Tuinier, Remco ; Schurtenberger, Peter ; Stradner, Anna

In: Soft Matter, 2012, vol. 8, no. 5, p. 1547-1555

We explore the properties of casein/xanthan mixtures for xanthan concentrations beyond those inducing phase separation. Previous work has successfully described the onset of demixing by depletion theory in the protein limit, where the xanthan polysaccharides , the polymers , are larger than the caseins from skim milk powder, the colloids (S. Bhat et al., J. Phys.: Condens. Matter, 2006, L339). We...

Université de Fribourg

Cluster-Driven dynamical arrest in concentrated lysozyme solutions

Cardinaux, Frédéric ; Zaccarelli, Emanuela ; Stradner, Anna ; Bucciarelli, Saskia ; Farago, Bela ; Egelhaaf, Stefan U. ; Sciortino, Francesco ; Schurtenberger, Peter

In: The Journal of Physical Chemistry B, 2011, vol. 115, no. 22, p. 7227–7237

We present a detailed experimental and numerical study of the structural and dynamical properties of salt-free lysozyme solutions. In particular, by combining small-angle X-ray scattering (SAXS) data with neutron spin echo (NSE) and rheology experiments, we are able to identify that an arrest transition takes place at intermediate densities, driven by the slowing down of the cluster motion. Using...

Université de Fribourg

Structure of β-lactoglobulin microgels formed during heating as revealed by small-angle X-ray scattering and light scattering

Moitzi, Christian ; Donato, Laurence ; Schmitt, Christophe ; Bovetto, Lionel ; Gillies, Graeme ; Stradner, Anna

In: Food Hydrocolloids, 2011, vol. 25, no. 7, p. 1766-1774

We have investigated the structure of microgels formed during heating of demineralized β-lactoglobulin (βlg) solutions at pH 5.9 by small-angle X-ray scattering (SAXS) and light scattering. First, unheated βlg solutions were characterized at different pH values between 2.0 and 7.0. At pH 5.9, βlg solutions contain mainly dimers (with a radius of approx. 2 nm), which coexist with a small...

Université de Fribourg

Simple transmission measurements discriminate instability processes in multiple emulsions

Vincent, Romaric R. R. ; Gillies, Graeme ; Stradner, Anna

In: Soft Matter, 2011, vol. 7, p. 2697-2704

Water-in-oil-in-water double emulsions (W1/O/W2) consist of water droplets (W1) dispersed in oil globules (O), which are then redispersed in an external aqueous phase (W2). This paper reports multiple light scattering investigations on W1/O/W2 double emulsions, the inner W1/O emulsion being a concentrated micron sized inverse emulsion, and the outer O/W2 emulsion being a dense direct emulsion....

Université de Fribourg

The pH induced sol-gel transition in skim milk revisited. a detailed study using time-resolved light and X-ray scattering experiments

Moitzi, Christian ; Menzel, Andreas ; Schurtenberger, Peter ; Stradner, Anna

In: Langmuir, 2011, vol. 27, no. 6, p. 2195–2203

We present a detailed study of the evolution of the size, structure and stability of casein micelles upon acidification of skim milk typically applied in yogurt-making processes using a combination of time-resolved light and small-angle X-ray scattering experiments. While most of the available light scattering studies on casein acidification have been restricted to transparent and therefore...

Université de Fribourg

Phase separation and dynamical arrest for particles interacting with mixed potentials—the case of globular proteins revisited

Gibaud, Thomas ; Cardinaux, Frédéric ; Bergenholtz, Johan ; Stradner, Anna ; Schurtenberger, Peter

In: Soft Matter, 2011, vol. 7, no. 3, p. 857

We examine the applicability of the extended law of corresponding states (ELCS) to equilibrium and non equilibrium features of the state diagram of the globular protein lysozyme. We provide compelling evidence that the ELCS correctly reproduces the location of the binodal for different ionic strengths, but fails in describing the location of the arrest line. We subsequently use Mode Coupling...

Université de Fribourg

Internal structure and colloidal behaviour of covalent whey protein microgels obtained by heat treatment

Schmitt, Christophe ; Moitzi, Christian ; Bovay, Claudine ; Rouvet, Martine ; Bovetto, Lionel ; Donato, Laurence ; Leser, Martin E. ; Schurtenberger, Peter ; Stradner, Anna

In: Soft Matter, 2010, vol. 6, no. 19, p. 4876-4884

Covalently cross-linked whey protein microgels (WPM) were produced without the use of a chemical cross-linking agent. The hierarchical structure of WPM is formed by a complex interplay of heat denaturation, aggregation, electrostatic repulsion, and formation of disulfide bonds. Therefore, well-defined spherical particles with a diameter of several hundreds of nanometers and with relatively low...

Université de Fribourg

A new instrument for time-resolved static and dynamic light-scattering experiments in turbid media

Moitzi, Christian ; Vavrin, Ronny ; Bhat, Suresh Kumar ; Stradner, Anna ; Schurtenberger, Peter

In: Journal of Colloid and Interface Science, 2009, vol. 336, no. 2, p. 565-574

We present a new 3D cross-correlation instrument that not only allows for static and dynamic scattering experiments with turbid samples but measures at four angles simultaneously. It thus extends the application of cross-correlation light scattering to time-resolved studies where we can, for example, efficiently investigate the temporal evolution of aggregating or phase separating turbid...