Curriculum Vitae of Remco Tuinier

1971:	born March 3 in Soest, The Netherlands (NL)
1989-1994:	Food Science study at Wageningen University (NL) ; graduated with main subjects in Food Physics (Professor A. Prins), and in Colloid and Interfacial Chemistry (Professors Martien Cohen Stuart and Gerard Fleer)
1994-1999:	PhD work at NIZO food research and the Physical Chemistry and Colloid Science group of Wageningen University. This resulted in a PhD thesis entitled 'An exocellular polysaccharide and its interactions with proteins' which I defended on June 4, 1999. The PhD work was performed at NIZO food research (NL) with Dr. Nel Zoon and Professor Kees de Kruif, Ede, as supervisors. We collaborated with Professors Gerard Fleer and Martien Cohen Stuart of the Laboratory for Physical Chemistry and Colloid Science of Wageningen University.
1999-2001:	Postdoc work supervised by Professor H.N.W. Lekkerkerker at the Van 't Hoff Laboratory (NL) ..The work focused on theoretical and experimental work on depletion interaction between small colloids (proteins) due to long polymer chains (polysaccharides). Besides that I gave two lecture series on Physical Chemistry for the second year M.Sc. chemistry students.
* 2000-2001:	Project leader at NIZO food research on polysaccharide-protein interactions.
Since November 2001:	: Project Leader in the Soft Condensed Matter Group of Professor J.K.G. Dhont at the IFF, Germany.

Research Interests of R. Tuinier

My interests are the physical properties of colloids, and polymers, and their biological analogues: polysaccharides and proteins, their interactions and properties such as phase behavior. The experimental techniques that have my main interest are scattering techniques, both dynamic and static, using light, X-Rays or neutrons. Theoretically, I am attracted to depletion type of interactions (see refs 1,4,6,9,11,13). These types of interactions play an important role in mixed biopolymer systems. My Project is briefly described below:

Project 'Biomacromolecular systems'

In this project the focus is on understanding the physical properties of biomacromolecular dispersions, such as proteins and polysaccharides. In living materials biomacromolecules are ubiquitous. In derived products of living materials, such as food products, biomacromolecules are essential contributors to the structure and stability, and they determine the material's flow properties. The aim of the project is to increase the understanding of how biomacromolecules provide structure, determine stability and affect flow properties. In order to achieve this, knowledge from soft condensed matter physics is transferred to the field of biomacromolecules. For instance, several aspects of biopolymers can be explained by using classical polymer physics. In the same line of reasoning many proteins, as well as aggregated protein particles can be treated as colloidal particles, and can therefore be termed 'biocolloids'. The main subjects of the project are 'Phase behavior and interactions,' 'Aggregation, gelation, influence of (bio)polymers,' and 'Dynamic properties of biomacromolecules in and out of equilibrium.' Two concrete subjects within the project are explained below.

Segregative interaction in dispersions with charged particles

Mixing biomacromolecules may lead to instability due to segregative or associative interactions. If proteins are mixed with polysaccharides, often a segregative interaction occurs and the resulting properties can be explained in terms of depletion interaction. The depletion mechanism has been used successfully over the last decades to describe the phase behavior of polymer-colloid mixtures of which protein-polysaccharide mixtures are a specific example. So far, theories mainly consider uncharged mixed colloids and polymers. Proteins (and polysaccharides) however are (often) charged and the effect of these charges together with depletion is not well understood. Therefore, theories have to be developed in order to describe polyelectrolyte depletion. These theories can be tested with total internal reflection microscopy (TIRM) (in collaboration with Dr. P. Lang), which allows a direct measurement of the force between a sphere and a plate. A thorough understanding of polyelectrolyte depletion and the effects of charges on the biocolloids will make it possible to describe the phase behavior of charged polysaccharides mixed with biocolloids.

Aggregation, gelation, and influence of attractions in lysozyme dispersions

The aggregation of proteins is relevant in several practical systems. For instance food products, often containing proteins, undergo a heat treatment when sterilized or pasteurized. During those treatments proteins tend to denature and subsequently aggregate. This process affects the final properties of a product. The aggregation of proteins may, in the later stages, also result in gelation. The aggregation process can thus be used to build structures. The aggregation process of lysozyme will be studied as a function of pH and temperature and the aggregated particles will be analyzed with scattering techniques. The transition from a dispersion of aggregated particles toward gelation will be studied and compared with theory and computer simulation results. The effect of non-adsorbing polymer on dispersions with aggregated lysozyme, and on gelation is another point of interest. Adding non-adsorbing polymer leads to phase separation and the kinetics of phase separation will be investigated. The effect of non-adsorbing polymer on protein gelation still poorly understood. Scattering techniques will be important tools in order to understand lysozyme aggregation and gelation (in presence of polymers).

Monte Carlo simulation snapshot: colloidal sphere close to a flat wall in the presence of ideal non-adsorbing polymer chains. The grey scale corresponds to the polymer segment density (black= no polymer, white = bulk segment density) (from a collaboration with A.V. Petukhov, Van't Hoff Laboratory, University of Utrecht, NL).