Yearbook of the Max Planck Society

Sustainable raw materials are more in demand than ever – not least to save resources and reduce CO2 emissions. For this reason, we are seeking to utilise biogenic materials that have previously been regarded as waste from the timber industry for high-quality applications. In an interaction between basic scientific research and design, we are investigating how tree bark can be processed to create rigid boards and a flexible, leather-like material.

Emulsions are a central part of our daily lives. Dispersions of oil-in-water or water-in-oil are used in a variety of everyday products such as food, cosmetics and medical articles, paints and detergents. In addition to the investigation of classical single-component droplet systems, we are increasingly focusing on the production and investigation of emulsions consisting of multiphase droplets, so-called complex emulsions. Here we observed a unique chemically stimulable behaviour of such multi-component systems, which enable the development of new and improved applications of emulsions from biomimetics and biosensorics to the construction of autonomously acting, artificially intelligent microreactors.

Carbohydrates are abundant biopolymers with applications ranging from paper and textile manufacturing to pharmaceuticals. Still, their full potential remains untapped, because carbohydrates are not well understood at the molecular level. We synthesized well-defined samples for structural analysis. Imaging single carbohydrate molecules revealed that some polymers form helices while others adopt rod-like structures. These compounds assembled into materials with well-defined compositions, enabling applications in nanotechnology.

At the Max Planck Institute of Colloids and Interfaces in Potsdam we were able to show that growing bone tissue behaves like a viscous liquid on long time scales, thereby taking shapes with minimal surface area. This cell behavior determines the shape of the tissue when it grows on a scaffold. These findings could have far-reaching importance in terms of understanding healing processes and organ development but also for medical applications such as the development of implants.

Artemisinin, the basis of the currently most effective malaria drug, is derived from the annual wormwood plant (Artemisia annua). However, the purification is inefficient and expensive, so that half of the drug market is served with ineffective counterfeits. We have developed an environmentally friendly process whereby a waste product produced by the plant is rapidly and efficiently converted to the drug using light-activated oxygen. The very environmentally friendly, patented process is now being developed in the USA by the spin-off ArtemiFlow for industrial application.

Thin molecular layers such as biological lipid membranes have diverse functions in Nature. But molecular layers play important roles in technology and biotechnology as well, where they improve, for instance, the biocompatibility of surfaces, or serve as lubricants and reduce shear friction. Researchers at the Biomaterials department use advanced x-ray and neutron scattering methods to structurally characterize such layers in order to obtain new insights into their functioning.

The success of the vast majority of chemical transformations is reliant on the degree of control exhibited over a wide range of variables. Utilizing flow chemistry – where reagents are passed through a set of conditions via thin tubing as opposed to applying conditions to a round bottom flask – has allowed for achieving chemistries and efficiencies previously inaccessible. The modular nature of this technique has facilitated the development of a novel means of chemical synthesis, which targets core functionalities, allowing for multiple derivatives to be produced with a single flow system.

Smart materials are designed to convert an external stimulus into a pre-defined, programmed response. Only a limited number of materials has been developed to date that are able to report on mechanically induced defects by changing their optical properties. Of further interest are materials that are able to self-heal such defects. To obtain these unique properties, mechanoresponsive molecules are required, which respond to the applied force in a well-defined manner. The research goals are to develop such molecules, to understand the mechanisms and to integrate them into novel smart materials.

Nanoparticles are tiny particles with sizes between a millionth and a thousandth of a millimeter. They include natural viruses, as well as synthetic particles that are increasingly used for medical purposes. In order to enter a cell via endocytosis, a nanoparticle must first bind to the outer cell membrane. The membrane then spreads onto the particle surface until the particle is completely engulfed by the membrane. The key parameters that control this process on nanoscopic length scales have only recently been identified.

Today the sustainable generation of fine and platform chemicals from biomass is desirable but still involves many problems. The Biorefinery group of the institute develops efficient separation techniques in order to design new product flows from biomass. New efficient catalytic methodologies are synthesized which withstand the partly extreme conditions while biomass is transferred. Biorefinery and its novel successful strategies for the upgrade of biomass into an array of valuable chemicals is a chance for material science to create a new unconventional generation of polymers and colloids.

Biological organisms utilize a remarkable range of effective strategies for building high performance materials, many of which surpass the state-of-the-art in engineered materials. Researchers from the MPIKG have discovered that some organisms, including spiders and mussels, incorporate tiny amounts of metal ions into protein-based materials to vastly improve mechanical performance (e.g. high toughness, high hardness and even self-healing). Based on this work, researchers are now developing bio-inspired metallopolymers with enhanced performance.

Biomolecular systems are often challenging to model, because they are inherently multiscale, i.e. small differences in the molecular building blocks can result in significant changes of the larger scale properties. Natural Polysaccharides for instance are typically assembled from a small number of basic sugar types, yet they can display a wide range of exceptional material properties, which derive from their spatial organization. Suitable models need to combine atomistic resolution with coarser representations retaining as much of the characteristics of the highly resolved system as possible.

Different eukaryotic proteins are anchored to the cell membrane using Glycosylphosphatidyl-inositols (GPIs) and have diverse and essential biological functions. To date little is known about the functions of the glycolipid anchors, however by using synthetic methods, it is now possible to obtain these molecules in pure form and to gain details about their biological properties. Synthetic GPIs are useful for the differential diagnosis of acute and latent toxoplasmosis and open new fronts for the diagnosis and treatment of other diseases.

Bioinspired poly(amino acid)s with stimuli-responsive properties and the ability to recognize and selectively bind to biological systems (proteins) are readily available in rather large quantities through optimized methods of synthetic polymer chemistry. Partially glucosylated polyglutamate and poly(N-alkyl glycine) may be used as “intelligent” polymers for applications in the biomedical field, for instance for therapeutic and regenerative medicine or diagnostics, as well as for the fabrication of hierarchical structures.

Simple methods applicable in liquids enable the construction of surfaces with defined porosity. The processes also allow the incorporation of drugs into the surface and by suitable coating also the controlled release. This enables the design of the contact between the surface and adjacent cells. For perspective hard implant materials like Ti it is thus possible to stimulate the growth of osteoblasts, the dominant cells of bones.

Within any living organism sugars as part of many cellular building blocks regulate inter- and intra- cellular processes. To characterize glycosylation in full, computer models are becoming increasingly significant. The example of the Glycosylphosphatidylinositol anchor shows that classical structure analysis with molecular dynamics techniques must be combined with system representations at coarser levels. Only in this way, many unspecific but important functions of sugar residues may be uncovered.

A knowledge of the structure and properties of bone is fundamental for the understanding and treatment of bone fractures and bone diseases such as osteoporosis. Methodologies from materials science have been shown to be useful in evaluating current therapies as well as in the development of new treatments for bone disease. Bone is a complex hierarchically structured material with remarkable mechanical properties, consisting principally of mineralized collagen fibrils. A better understanding of growth, structure and mechanics will help answer clinical needs in the future.

With nearly 1 million people dying per year, malaria is a global health problem. Artemisinin combination therapies are regarded as first-line drugs. However, their supply is limited, as artemisinin is currently solely extracted from plants. Its precursor dihydroartemisinic acid on the other hand can be obtained by a biotechnological process. A continuous flow chemistry setup was developed to produce artemisinin from this precursor in high yield just using oxygen and light.

Interfacial properties influence the bulk phase behavior and often the bulk structure. For very small systems (nanoparticles, thin films) this is obvious. The relative amount of interfacial molecules is large. Yet, interfacial influences often are also important for macroscopically large systems because these typically originate from small nano size aggregates. In addition, the growth to macroscopic size always occurs at the interface. Local interfacial transport conditions affect the growth kinetics and thus also the structure and properties of the resulting macroscopic entity.

Synthetic sugars offer great potential e.g. for the development of new treatments or vaccines. Thus chemists have been searching for new molecules offering the same biological activity that can be synthesized more easily. One important class of such mimetics are sugar polymers, a combination of polymer chains with natural sugars. In order to understand how such sugar polymers mimic the activity of natural sugars and how to more effectively synthesize such sugar polymers, a new class of monodisperse polymers is currently developed at the MPICI and tested for their properties.

Bioorganic-synthetic polymers are readily available in rather large quantities through modern methods of metal-free polymer synthesis and modification. Polymers based on polypeptides and saccharides can form “smart” biofunctional membranes and also hierarchical structures. Current studies deal with the understanding of fundamental mechanisms of bioinspired structure formation and with possible applications in biomedicine and materials science.

Natural and synthetic genetic circuits are always coupled to the physiological state of the cell in which they reside. For example, the concentrations of RNA polymerases and ribosomes that are available for the readout of the genetic information depend on the cellular growth rate. Theoretical studies can help to investigate the coupling of regulatory mechanisms and growth and to uncover principles that underlie the efficient use of molecular machines.

Carbohydrates are complex molecules that are extremely difficult to synthesize by both chemical and enzymatic means. This is one of the main reasons why the entire field of glycomics is less prominent than genomics and proteomics. In the following report we discuss the introduction of the automatic chemical synthesis of carbohydrates and its impact on glycoscience.

Magnetic nanoparticles are key components in many novel bio- and nanotechnological applications. These applications require highly uniform particle dimensions. The available chemical processes are unable to produce such crystals. Magnetotactic bacteria have resolved the complicated equation of forming such perfect particles under physiological conditions. This performance is analyzed by determining the role that key biological determinants play in the control of the properties of the biological magnets. The Mms6 protein was shown to specifically control magnetite size in vitro .

Modern X-ray diffraction techniques using microbeam radiation from synchrotron sources allow the imaging of the hierarchical structure of biological materials on different length scales. Moreover, in-situ X-ray diffraction provides the possibility to follow nanostructural changes of materials as a consequence of external influences such as mechanical deformation or humidity changes. This article presents a novel scientific instrument developed by the Max Planck Society at the BESSY storage ring in Berlin, which permits such experiments to be conducted with high resolution.

The sequence of a protein determines, in which three-dimensional structure it folds. The structure in turn enables the biological function of the protein. During function, many proteins slightly change and adapt their three-dimensional structures. These structural changes, as well as the structure formation during folding, cannot be observed directly in experiments. However, combined with theoretical modeling, mutations of a protein provide indirect access to these dynamic processes.

The rational design of pores and channel systems within „soft materials“ such as polymers, carbonaceous materials, or carbon nitrides enables the generation of novel chemical systems with novel effects. This short overview deals with the resulting phenomena, such as metal free heterogeneous catalysis, membranes for the fuel cell, polymeric gas storage materials, but also with sustainable synthesis techniques such as the hydrothermal carbonization for the generation of sorption coals.

The characterization of molecular mechanisms of interactions between peptides and cell membranes is very important for the understanding of structure-function relations. These are studied with 2-dimensional monolayers at fluid interfaces using modern biophysical methods. This report shows how the interface influences the secondary structure of the peptides, and vice versa how the peptide adsorption leads to changes in the structure of phospholipid layers.

Biology and chemical synthesis provide various semiflexible polymers, which have a high bending rigidity. Important examples are filaments, which form the cytoskeleton of cells. Semiflexible polymers have unique material properties, which are relevant for biological structures. Theoretical models are presented for single polymer under external forces, filament bundles, and "active'' filaments, which are driven by motor proteins.

Biological systems inspire the design of new engineering materials due to their light weight structures and high adaptivity. A fist fundamental step in this biomimetic process is to understand and to extract the underlying structure-function relationships. Trees are particularly well suited for such “bio-inspired” studies since they develop high quality structures which may last for thousands of years and growing to 100 m height. This article provides an insight into recent research activities on the mechanical design of wood cell walls and emphasises how effectively trees control mechanical properties by adjusting the structural organisation of the cell wall.

Amphiphilic molecules contain a hydrophilic headgroup and a hydrophobic tail. The prevailing molecular asymmetry leads to a spontaneous adsorption of amphiphiles at the air-water or oil-water interface. As a result, the surface tension and the surface rheology are changed. We are using soluble amphiphiles as model systems to study fundamental interactions in colloid and interface science. An example is the distribution of ions at a charged interface. The puzzling ion specific effects are the result of a subtle balance of several competing evenly matched interactions consisting of a complex interplay of electrostatics, dispersion forces, thermal motion, fluctuations, hydration, ion size effects and the impact of interfacial water structure. Furthermore we try to identify correlations between observed macroscopic and the corresponding molecular properties of the adsorbed species. Surfactants enable phenomena such as foaming or emulsions. Foams can only be formed if surface active materials are present. The stability of foams is not yet completely understood and we believe that the surface rheology plays a decisive role. In the last years we developed several novel experiments to study surfactant dynamics and surface rheology.

Nanoparticles play a crucial role in the development of advanced materials and devices. The reason lies in the fact that particles just a few nanometres in size exhibit different chemical and physical properties compared to the bulk material. The wide variety of applications of metal oxides in catalysis, sensing, energy storage and conversion, optics and electronics moved this class of materials into the centre of interest of materials science. In order to obtain metal oxides in form of nanoparticles with well-defined shape, size and crystallinity, the traditional synthesis routes are hardly suited, and novel innovative strategies have to be developed. In comparison to the complex aqueous chemistry, the synthesis of metal oxide nanoparticles in organic solvents offers the possibility to better understand and to control the reaction pathways on a molecular level, enabling a rational synthesis design for inorganic nanoparticles based on organic chemistry.

Biomimetic systems with fine-tuned properties have many potential applications such as drug delivery systems or biosensors. In order to design such systems, one needs a detailed understanding of the underlying nanostructures and nanoprocesses. These structures are very thin and have a thickness of a few nanometers which makes them rather flexible and mobile. There is no experimental method by which one could directly image the dynamics of these structures. Therefore, it is rather appealing to use computer simulations in order to visualize these processes. A particularly powerful simulation method is provided by Dissipative Particle Dynamics which can be used to monitor supramolecular systems with a linear dimension of up to 50 nanometers over a time period of several microseconds. In this article, we discuss three examples for such systems: lipid membranes that contain several components and form different intramembrane domains; vesicles composed of diblock copolymers which could be used as drug delivery systems; and tension-induced fusion of bilayer membranes. The method of Dissipative-Particle-Dynamics can be used to optimize nanostructures and -processes in silico before one performs many costly experiments.

Living bone is continuously remodeled via resorption and deposition of small bone packets. This remodeling process is controlled by a mechanical feedback loop, which allows bone to adapt to varying mechanical requirements. Being experimentally difficult to access, the feedback loop is intensively studied using computer modeling. In the simulation it is possible to discriminate between changes in the bone structure due to either aging or disease. With a better understanding of the interrelation between the feedback loop and changes in the bone structure, there is hope that improved therapies act directly on the real reasons of bone diseases.

The investigation of crystallization processes is a long established field of science. Crystals have a smallest unit called the unit cell and all crystal forms can be related to it with the consequence that crystals always exhibit planar surfaces. Crystals are built from ions or molecules. Recently, the investigation of so-called biominerals has revealed that not all crystals fit the classical textbook picture. For example biominerals, which are minerals deposited by living organisms like skeletons of algae, exhibit crystal morphologies with complex form, which even show untypical curvature. Thus they deviate significantly from the classical planar crystal surfaces. Furthermore, biominerals are often highly optimised composite materials like bones, teeth or mussle shells. This is achieved by a control of the crystallization process by structure directing molecules. Furthermore, recent investigations have revealed that these crystals are not always formed according to the rules of classical crystallography e.g. via regular attachment of ions or molecules to a growing crystal. The project group "Biomimetic Mineralization" tries to mimic and understand the control of crystallization processes via structure directing additives or non-classical structuration processes. By this approach, not only biomineralization processes can be understood, but also new environmentally friendly ways of materials synthesis in water at ambient temperature with biocompatible components can be investigated and established.

The assembly of materials through weak competitive interactions and molecular modules provides fascinating opportunities for the development of key technologies for the 21st century. The utilization of weak intermolecular interactions for the controlled assembly of well-defined devices has become a central motive in nano-science and materials science. Here, several methods are presented that allow the spontaneous assembly of complex architectures. The integration of metal ions into the structures results in value adding functions, which are relevant for magnetic, optical and electronic applications. The modularity of this approach provides extensive control of structure and function from molecular to macroscopic length scales. In addition, the usage of structural and functional modules provides a maximum in flexibility and synthetic simplicity.