Our research is focused on the physics and self-assembly of biomolecular soft matter. With the help of x-ray/neutron scattering and complementary methods we investigate soft matter of biological or biotechnological relevance, such as lipid membranes, (bio)polymers, or surface-adsorbed protein layers, in order to determine their structure on molecular and supramolecular (mesoscopic) length scales.

Such structural insight is prerequisite to understand important functional properties of biomolecular assemblies. Since biomolecules in nature are often organized as thin layers, most of our work concerns the study of planar interfaces. More recently, we have however extended our activities towards biomolecular assemblies in fiber geometries and in bulk.

Picture: AG Schneck

Colloidal interactions in biological soft matter

So far, colloidal interactions have been investigated almost exclusively in terms of pressure-distance relationships and continuum-theoretical models. We complement these classical approaches with two additional ones.

Schematic illustration of two interacting biomembranes

At first, with detailed structural insight in terms of molecular conformations and elemental distributions. And secondly, with the help of rigorous solvent-explicit computer simulations precisely accounting for the solvent chemical potential. The ultimate goal is the quantitative understanding and prediction of interfacial forces in biology and soft matter. Of special interest are biomembrane recognition and adhesion processes (see Figure above). Here, the long-term goal is to understand the structural and energetic context in which specific receptor/ligand recognition occurs and membrane adhesion is established or released.

Selected publications:

  • V. M. Latza, B. Demé, E. Schneck Membrane adhesion via glycolipids occurs for abundant saccharide chemistries Biophysical Journal, 118, 1602 (2020)
  • E. Schneck The Interaction between Soft Interfaces: Forces and Structural Aspects Advanced Materials Interfaces 4, 1600349 (2017)
  • E. Schneck, F. Sedlmeier, R. R. Netz Hydration Repulsion between Bio-Membranes Results from an Interplay of Dehydration and Depolarization Proc. Natl. Acad. Sci. USA, 109, 14405 (2012)
  • M. Kanduc, A. Schlaich, A. de Vries, B. Demé, J. Jouhet, E. Maréchal, R. R. Netz, E. Schneck Tight Cohesion between Glycolipid Membranes Results from Balanced Water-Headgroup Interactions Nature Communications, 8, 14899 (2017)
  • I. Rodriguez-Loureiro, E. Scoppola, L. Bertinetti, A. Barbetta, G. Fragneto, E. Schneck Neutron Reflectometry Yields Distance-Dependent Structures of Nanometric Polymer Brushes Interacting across Water Soft Matter, 13, 5767 (2017)
  • I. Rodriguez-Loureiro, V. M. Latza, G. Fragneto, E. Schneck Conformation of Single and Interacting Lipopolysaccharide Surfaces Bearing O-Side Chains Biophysical Journal, 114, 1 (2018)
Picture: AG Schneck

Protein adsorption to biological and technological interfaces

Protein adsorption to surfaces is at the heart of numerous technological and bio-analytical applications but sometimes also associated with medical risks.

Blood protein adsorption

End-grafted polymer brushes therefore are widely used in order to suppress undesired protein adsorption to surfaces exposed to blood or other biological fluids (Figure, left). We use neutron reflectometry and x-ray-based element-specific structural characterization techniques (Figure, middle) to determine protein distributions, orientations, and conformations (Figure, right) after adsorption to various types of (functionalized) interfaces. With this approach, we have provided the first structural insight into the highly-debated phenomenon of protein adsorption to surfaces passivated with end-grafted polymers.

Selected publications:

  • V. M. Latza, I. Rodriguez-Loureiro, I. Kiesel, A. Halperin, G. Fragneto, E. Schneck Neutron Reflectometry Elucidates Protein Adsorption from Human Blood Serum onto PEG Brushes Langmuir, 33, 12708 (2017)
  • E. Schneck, I. Berts, A. Halperin, J. Daillant, G. Fragneto Neutron Reflectometry from Poly (ethylene-glycol) Brushes Binding Anti-PEG Antibodies: Evidence of Ternary Adsorption Biomaterials, 46, 95 (2015)
  • E. Schneck, E. Scoppola, J. Drnec, C. Mocuta, R. Felici, D. Novikov, G. Fragneto, J. Daillant Atom-Scale Depth Localization of Biologically Important Chemical Elements in Molecular Layers Proc. Natl. Acad. Sci. USA, 113, 9521 (2016)
Picture: Alexander Baer & Ivo de Sena Oliveira

Native biological soft matter and biomolecular assemblies in bulk

Biomolecular assemblies are not always organized in the form of thin layers but often assume globular or fiber-like shapes. Over the last two years we have extended our research towards the structural investigation of such forms of biomolecular assemblies.

Velvet worm ejecting prey-capture slime containing protein/lipid nanoglobules.

For example, we use small-angle x-ray and neutron scattering (SAXS and SANS) to investigate the internal structure of globular nanometric protein/lipid complexes in the native prey-capture slime of the velvet worm (see Figure), which exhibits exceptional reversible rigidification properties. Similarly, we use x-ray diffraction to characterize the hierarchical structure of self-assembled collagen model peptides, and we use SANS, dynamic light scattering, and rheology to investigate the self-assembly of biopolyelectrolyte/surfactant complexes, which form highly viscous networks under certain conditions.

Selected publications:

  • G. R. Del Sorbo, V. Cristiglio, D. Clemens, I. Hoffmann, E. Schneck The Influence of the Surfactant Tail Length on the Viscosity of Oppositely Charged Polyelectrolyte/Surfactant Complexes Macromolecules, 54, 2529 (2021)
Picture: AG Schneck

Biological roles of osmotic pressures and biological liquids under tension (Content under construction)

Plants use negative pressure to draw water from the soil. Why the pressure value does not fall below minus 100 bar was previously an unsolved mystery…

An interdisciplinary and international research group with the participation of the Technical University of Darmstadt now reports in the journal Proceedings of the National Academy of Sciences (PNAS) that apparently so-called lipid aggregates in the plant saps are responsible for the phenomenon. Simulations and model calculations show how the lipids lead to the formation of expanding cavities that cause the fluid column to break off when the negative pressures become too great.

Selected publications:

  • M. Kanduc, E. Schneck, P. Loche, S. Jansen, H. J. Schenk, R. R. Netz Cavitation in lipid bilayers poses strict negative pressure stability limit in biological liquids Proc. Natl. Acad. Sci. USA, 117, 10733 (2020)
  • W. Zhang, L. Bertinetti, K. G. Blank, R. Dimova, C. Gao, E. Schneck, P. Fratzl Spatiotemporal Measurement of Osmotic Pressures by FRET Imaging Angewandte Chemie Int. Ed., 60, 6488 (2021)
Picture: AG Schneck

Rational design of functional liquid interfaces (Content under construction)

We intend to carry out research towards the purposeful functionalization of liquid/liquid interfaces.

Picture: AG Schneck

With the help of chemical crosslinking-reactions (which we have successfully used for lipid monolayers) and the concepts described above, it should be possible to rationally design and realize liquid/liquid interfaces with defined mechanical properties (dilation, shear, and bending moduli), transport properties (through pores), and interaction characteristics with solutes (adsorption) and other interfaces (colloidal stability). Such architectures can be used use as soft supports for lipid membranes and may serve as platforms for tailored biocatalysis applications involving enzymes.

With the help of tensiometry, x-ray reflectometry, and neutron reflectometry we demonstrated that we are able to functionalize oil-water interfaces with amphiphilic monolayers such that they promote the adsorption of lipid bilayers. The resulting trilayers are stabilized by electrostatic, polymer-steric, and solvophobic interactions. Our efforts are motivated by the great potential liquid/liquid interfaces have for membrane-biophysical investigations. These include studies of molecular transport through lipid membranes and the control of interfacial forces through the oil phase, without variation of the physiological aqueous environment (such as pH, temperature, or ionic strength).

Selected publications:

  • C. Stefaniu, C. Wölk, G. Brezesinski, E. Schneck Relationship between structure and molecular interactions in monolayers of specially designed aminolipids Nanoscale Advances, 1, 3529 (2019)
  • P. Mueller, D. J. Bonthuis, R. Miller, E. Schneck Ionic Surfactants at Air/Water and Oil/Water Interfaces: A Comparison Based on Molecular Dynamics Simulations J. Phys. Chem. B, 125, 406 (2021)