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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

Single step hybrid coating process to enhance the electrosteric stabilization of inorganic particles

Rufier, Chantal ; Reufer, Mathias ; Dietsch, Hervé ; Schurtenberger, Peter

In: Langmuir, 2011, vol. 27, no. 11, p. 6622-6627

We report on a single-step coating process and the resulting colloidal stability of silica-coated spindle-type hematite nanoparticles (NPs) decorated with a layer of poly(acrylic acid) (PAA) polyelectrolyte chains that are partially incorporated into the silica shell. The stability of PAA coated NPs as a function of pH and salt concentration in water was compared to bare hematite particles...

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

Catalytic hydrogenation using abnormal N-heterocyclic carbene palladium complexes: catalytic scope and mechanistic insights

Heckenroth, Marion ; Khlebnikov, Vsevolod ; Neels, Antonia ; Schurtenberger, Peter ; Albrecht, Martin

In: ChemCatChem, 2011, vol. 3, no. 1, p. 167-173

Palladium complexes containing abnormally bound C4-bound dicarbene ligands have been exploited for catalytic alkene hydrogenation. Comparison to normally C2-bound homologues indicates that the carbene bonding mode critically influences the catalytic activity. Good catalytic performance in the hydrogenation of cis-disubstituted olefins and non-isomerizable terminal olefins under mild...

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

Magnetic properties of silica coated spindle-type hematite particles

Reufer, Mathias ; Dietsch, Hervé ; Gasser, Urs ; Grobéty, Bernard ; Hirt, A. M. ; Malik, Vivek Kumar ; Schurtenberger, Peter

In: Journal of Physics: Condensed Matter, 2011, vol. 23, no. 6, p. 065102

Magnetic properties of particles are generally determined from randomly oriented ensembles and the influence of the particle orientation on the magnetic response is neglected. Here, we report on the magnetic characterization of anisotropic spindle- type hematite particles. The easy axis of magnetization is within the basal plane of hematite, which is oriented perpendicular to the spindle axis....

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

DMSO-induced denaturation of hen egg white lysozyme

Voets, Ilja K. ; Cruz, Willemberg A. ; Moitzi, Christian ; Lindner, Peter ; Arêas, Elizabeth P. G. ; Schurtenberger, Peter

In: The Journal of Physical Chemistry B, 2010, vol. 114, p. 11875–11883

We report on the size, shape, structure, and interactions of lysozyme in the ternary system lysozyme/DMSO/water at low protein concentrations. Three structural regimes have been identified, which we term the “folded” (0 DMSO DMSO DMSO < 1.0) regime. Lysozyme resides in a...