Research

Protein materials

The de Vries Lab investigates materials made out of proteins. The materials can be natural protein materials such as silk, man-made materials in which natural proteins are a key component such as in cheese, but also entirely new protein materials made from newly designed proteins such as tiny protein containers that can contain medicines. The key question we aim to answer is: how does the nature of a protein (sequence), together with the way we treat a protein (processing) determine the properties of protein materials? Answering this question helps us to make new and better protein materials with applications in processed foods, biomedical technology, the personal care industry and much more.

Our current research roughly falls in one of these categories:

  • food materials
  • non-food materials made from natural proteins
  • materials made from de-novo designed proteins

For food materials, we not only investigate proteins as building blocks but also polysaccharides.

Food materials

Impact of oat beta-glucan on plant protein-stabilized emulsions

Cereal β-glucans are present in e.g. oat and barley. These soluble fibers form highly viscous solutions in water. Because of this, they reduce the uptake of glucose and cholesterol in the intestine, and thus have a positive effect on health. This makes them a desirable food ingredient. β-glucans can also improve the texture of foods, for example in low-fat dairy products.

Like with any polymer, adding β-glucan to a food product will have physical effects, such as an increase in viscosity and depletion interaction. This can change the structure or stability of the product. These effects need to be characterized before we can use β-glucan as a food ingredient.

Using pure β-glucan, we have shown that adding β-glucan to emulsions can induce instability by depletion flocculation. But it can also slow down destabilization. We try to explain these differences in macroscopic behaviour by studying the phase separation kinetics and rheological properties. Similar studies will be performed with mildly purified oat fractions instead of pure β-glucan. A challenge here is to take into account the effects of other (fiber) components of the material. We study the chemical properties and contents of the oat fractions in order to explain the observed physical effects.

Contact
Dana te Brinke – dana.tebrinke@wur.nl

Molecular structure of cereal β-glucan
Macroscopic phase stability of emultions containing 0-12 mg/mL β-glucan after 7 days
Dry fractionation of seeds for high protein drinks

Due to the shift of people’s dietary pattern, the plant protein have drew more attention these years. However, the plant protein ingredient has not been developed to fulfil consumer wishes. In order to control the viscosity, thickness etc. which are generally contributed by an increased protein concentration, a plant-based native protein ingredient would be favoured. The Mung bean protein ingredient project consists of three subunits. To initiate the project, a more sustainable dry fractionation technique is employed to extract protein bodies from Mung beans, then the aqueous phase separation method is applied to study the extract efficiency of proteins at their native states. Afterwards, mung bean protein colloids are formulated and investigated. Meanwhile, with assistance of microscopy techniques such as light microscopy, SEM and CLSM, it would be possible to track protein bodies during the whole process quantitatively. We expect that the present ingredient is stable and enriched in protein, have promise to be added in high-protein drinks.

Contact
Qiuhuizi Yang – qiuhuizi.yang@wur.nl

Scanning Electron Microscope image of the dry fractionated Mung bean cell. Protein bodies (PB), pieces of non-protein cell components (NP) and starch granules (SG) can be distinguished.
Light Microscope image of mung bean protein colloids

Non-food materials from natural proteins

Encapsulation using plant proteins

In this research, we are aiming at using plant proteins as ingredients for replacing synthetic polymers and animal-based materials in encapsulation applications. We use a classical but efficient technique, coacervate encapsulation, to encapsulate functional payloads. For example, think of the fragrances in washing powders: these are enclosed in little plastic shells that break when you rub your towel and then release a “fresh” smell. Right now synthetic polymers made from fossil fuels are used for such shells, but together with an industry partner, Firmenich, we are looking for ways to use plant proteins to make such capsules.

Contact
Xiufeng Li – xiufeng.li@wur.nl

Oil droplets in water with protein coarcervates on the surface

Smart cellulose colloids using Natural Deep Eutectic Solvents

There is an increasing awareness that our future materials must be made sustainably using renewable resources. cellulose is an outstanding candidate starting material, being one of the most abundant natural biopolymers available on earth, and being both biodegradable and environmental-friendly. However, solution processing of cellulose is often unsustainable due to the lack of cheap and environmentally friendly solvents that can break the strong intramolecular and intermolecular hydrogen bonding networks of natural cellulose materials. In this project, we propose to explore and develop a novel alternative class of solvent for cellulose, so-called Natural Deep Eutectic Solvents (NADES). In the next coming stages, we propose to produce various types of “smart” colloids (e.g. nanoparticles, fibres, gels etc.) from biomass products by using an anti-solvent precipitation method.

Contact
Huy Nguyen – vu1.nguyen@wur.nl

Confocal microscopy image of regenerated cellulose precipitated by an anti-solvent

Materials from de-novo designed proteins

Design of self-assembling protein-DNA hybrid nanomaterials

Currently DNA nanotechnology is the only way of creating truly nm-scale addressable nanostructures, but these structures are fundamentally limited in size, currently <100 nm or smaller. We believe that by combining it with proteins we can make higher order biocompatible and addressable nanomaterials of arbitrary shapes and sizes >100 nm. In this project we are computationally designing de-novo repetitive proteins that fully cover and protect template DNA, while still allowing for addressable sites by using sequence specific binders. Ultimately design of such DNA-protein hybrid materials will allow us to create addressable nanomaterials with various applications in nanotechnology and biomedicine. For example, in collaboration with the King lab (University of Washington), we intend to explore the ability to program antigens on the surface of these new nanomaterials for antigen display.

Contact
Rob de Haas – rob.dehaas@wur.nl

Templated assembly of DNA by proteins. Binding occurs through electrostatic interactions in the major groove of DNA. Proteins self-assemble on the DNA template through DNA-protein and protein-protein interaction to form tightly packed fibers.
Atomic Force Microscopy image of dried protein-DNA fibers

pH fluorescent sensors for nanoparticle tracking

Nanomedicine is thought to have great potential to improve disease treatment by using nanoparticles to deliver for example chemotherapeutic drugs to specific target sites to reduce treatment side-effects. However, its complex interactions with cells and tissues of the human body often are poorly understood. It is thought that systems biology-based models may increase our fundamental understanding of nanoparticle-cell interactions, but developing such models requires data on the absolute numbers of nanoparticles in various subcellular compartments during their processing. In this project, we design fluorescent sensors that switch ON/OFF at pre-defined pH values. Using these molecular sensors aim to detect the subtle pH difference between acidic organelles (e.g. endosomes and lysosomes), and the cytosol during nanoparticle processing. Ultimately we aim to apply these sensors on nanoparticles to generate high-throughput and absolute quantitation of nanoparticle numbers in live cells and their sub-compartments using calibrated flow cytometry in collaboration with the Salvati and Aberg lab (University of Groningen).

Contact
Rob de Haas – rob.dehaas@wur.nl

Example of sensor design where fluorescence is quenched upon aggregation of a pH-sensitive (red) elastin-like polypeptide (ELP) domain through micelle formation and subsequent fluorescent quenching.
Computationally designed two-component protein nanoparticles (Bale et al. Science 2016). pH sensors constructs are genetically fused to the trimeric component to create atomically-defined nanoparticles with pH sensors on the inside for tracking in enodyctic vessles inside cells.

Design of structural surface binders

In this project we are (re)-designing flat structural proteins that bind to various surfaces (silica, polystyrene, gold). These binders can then be employed to create molecularly defined protein coatings with anti-fouling properties, which is useful for various biomedical applications.

Another aim is to re-design ice-binding proteins. These are proteins that are present in some artic plants and bacteria to prevent nucleation of ice crystals. Binding of these proteins to ice lowers the freezing point, which allows these organims to survive in sub-zero temperatures. We are attempting to re-engineer natural ice-binding proteins to increase ice-affinity and stabilize the protein structures. Ultimately these improved ice-binding proteins have applications cryo-surgery, organ transplantation and the food industry.

Contact
Rob de Haas – rob.dehaas@wur.nl

A pdb model of a de-novo designed protein where one side contains only positively charged (arginine) amino acids, that can bind negatively charged surfaces like silica through electrostatic interactions.
A pdb model of an idealized ice-binding protein. Each repeat contains 2 threonine’s, which bind the basal and primary-prism planes of ice crystals.

Polypeptide linkers for biosensor surface functionalization

Biosensors are becoming increasingly relevant both in research and diagnostics. Most biosensing tools exploit antibodies adsorbed on a surface like silica or plastic, in order to detect an analyte of interest. Although cheap and fast, this process is unfortunately also very inefficient. The current alternatives require expensive and complicated treatments of the biosensor surface. In this project, we focus on the design of polypeptide linkers to functionalize biosensor surfaces. In fact, naturally-occurring protein polymers can be easily engineered and tuned in their physical properties. The polypeptide linkers should be able to provide a stable and anti-fouling polymer brush, on which antibodies can be covalently attached. In collaboration with the department of Organic Chemistry, many polypeptide designs are screened and tested in order to find a suitable candidate. The linkers can be directly applied to newly designed biosensors from our collaborators at the Eindhoven University of Technology (de Jong lab).

Contact
Nicolò Alvisi – nicolo.alvisi@wur.nl

Schematic representation of the polymer brush monomers