B08 Broadband dielectric and IR spectroscopy to study molecular dynamics and order in nanometer domains of endfixed polymers.

The project B08 went through some changes over time. The project investigated :

  1. Broadband dielectric spectroscopy to study molecular dynamics in nanometer thin layers of blockcopolymers in the first funding period:
    2011-2015

  2. Broadband dielectric and IR spectroscopy to study molecular dynamics and order in nanometer domains of endfixed polymers in the second funding period: 2015-2019

  3. Refined Infrared Spectroscopy to Study Molecular Orientation and Order in Heterogeneous Polymer Systems in the third funding period: 2019-2023
Kremer

The central finding from the previous funding period was that the dynamic glass transition (segmental fluctuations) of (block co)polymers in nanometric layers (≥ 5 nm) was not influenced by geometrical confinement, while the dynamics and conformation of the chain as a whole (Rouse modes, reptation) changed fundamentally depending on the details of internal and external constraints and their mutual interactions. The investigated block copolymers thus shared strong similarities to homopolymers in nanoconfinement studied in other contexts. Based on these insights, it was planned to widen the scope in the coming application period and to come to a more detailed general understanding of dynamics and conformation of endfixed polymers under internal or external constraints. This comprised grafting to glassy copolymer blocks, to surfaces, and to crystalline lamellae.

As experimental methods, broadband dielectric spectroscopy (BDS) in combination with nanostructured electrode arrangements and Fourier Transform Infrared (FTIR)-spectroscopy including the newly developed Infrared Transition Moment Orientational Analysis (IR-TMOA) would be employed. The former had proven to be a tool of extraordinary sensitivity enabling even measuring the dynamics of single isolated polymer coils. The latter had been extensively used in the terminated project B05 of the applicant and allowed determining the molecular order parameter tensor of the different moieties of any (IR translucent) polymer with respect to the sample coordinate frame. By that, both techniques were complementary in determining dynamics and conformational ordering of the system under study. This opened the chance to address a multitude of novel research topics as follows: (i) Glassy dynamics in macroscopically oriented vs. unoriented nanometric diblock-copolymer layers – a comparison, (ii) molecular dynamics in diblock-copolymers swollen in a selective solvent, (iii) molecular dynamics in grafted homopolymers of varying grafting density, (iv) segmental dynamics and orientation effects of amorphous chains in semicrystalline polymers. The tertium comparationis in all these topics was how internal and external constraints determined dynamics and conformation of polymeric systems under confinement, with a particular focus on chain endfixation as a specific internal constraint.

Highlighted Publications:
  1. Kipnusu, W.K., M.M. Elmahdy, E.U. Mapesa, J. Zhang, W. Böhlmann, D.-M. Smilgies, C.M. Papadakis, F. Kremer, Structure and Dynamics of Asymmetric Poly(styrene-b-1,4-isoprene) Diblock Copolymer under 1D and 2D Nanoconfinement, ACS Appl. Mater. Interfaces, 7, 12328–12338 (2015) 

  2. Griffin, P.J., A.P. Holt, K. Tsunashima, J.R. Sangoro, F. Kremer and A. P. Sokolov, Ion transport and structural dynamics in homologous ammonium and phosphonium-based room temperature ionic liquids,  The Journal of Chemical Physics 142, 084501 (2015) 

  3. Anton, A.M.,R. Steyrleuthner, W. Kossack, D. Neher, F. Kremer, Infrared transition moment orientational analysis (IR-TMOA) on the structural organization of the distinct molecular subunits in thin layers of a high mobility n-type copolymer, Am. Chem. Soc., 137 (18), 6034-6043 (2015) 

B08 Broadband dielectric spectroscopy to study molecular dynamics in nanometer thin layers of blockcopolymers.

The project B08 went through some changes over time. The project investigated :

  1. Broadband dielectric spectroscopy to study molecular dynamics in nanometer thin layers of blockcopolymers in the first funding period:
    2011-2015

  2. Broadband dielectric and IR spectroscopy to study molecular dynamics and order in nanometer domains of endfixed polymers in the second funding period: 2015-2019

  3. Refined Infrared Spectroscopy to Study Molecular Orientation and Order in Heterogeneous Polymer Systems in the third funding period: 2019-2023
Kremer

While the structure of block copolymers was well explored, knowledge concerning their molecular dynamics was sparse. Broadband Dielectric Spectroscopy (BDS) using nano-structured electrode arrangements had proven to be a versatile tool in studying the molecular dynamics in thin homogeneous polymer layers. In the proposed project, it was planned to extend these experiments to nanometer thin layers of block copolymers. By that, the effect of an internal constraint due to micro-phase separation but as well due to an external restriction of the one-dimensional confinement in nanometer thin layers would be unraveled. In the special case of poly(styrene)-blockpoly(isoprene), it was possible to study in the polyisoprene block two processes, the segmental relaxation and a fluctuation of the end-to-end vector. This offered an additional means for studying the molecular dynamics at two different length scales. Special emphasis was given to the interplay between structure and dynamics in the different mesophases of the block copolymers. Furthermore, the impact of appropriate (chemically patterned) surfaces was analyzed.

Highlighted Publications:
  1.  Mapesa, E.U., M. Tress, G. Schulz, H. Huth, C. Schick, M. Reiche, F. Kremer, Segmental and chain dynamics in nanometric layers of poly (cis-1,4-isoprene) as studied by Broadband Dielectric Spectroscopy and temperature-modulated Calorimetry, Soft Matter 9 (44), 10592–10598 (2013) 

  2.  Tress, M., E.U. Mapesa, W. Kossack, W.K. Kipnusu, M. Reiche, F. Kremer, Glassy Dynamics in Condensed Isolated Polymer Chains, Science 341 (6152) 1371-1374 (2013) 

  3. Neubauer, N., R. Winkler, M. Tress, P. Uhlmann, M. Reiche, W.K. Kipnusu, F. Kremer,  Glassy dynamics of Poly(2-Vinyl-Pyridine) brushes with varying grafting density, Soft Matter 11, 3062-62015 (2015) 

Z01 Synthesis of Labeled and Unlabeled Peptides with Difficult Sequences in Large Scales

Rothemund

The goal of our service project was the synthesis and supply of labeled and unlabeled peptides that bore the tendency to aggregate during the synthesis as well as in structural analysis investigations. We aimed for purities of ≤95% in the scale of 10 mg to 200 mg and reproducible conditions for subsequent biophysical studies. Generally, the peptides were analogs from biologically active peptides such as amyloid ß 1-40 and 1-42 (Aß1-40 and Aß1-42) and parathyroid hormone 1-84 (PTH1-84). In our Core Unit custom peptide synthesis, we performed the synthesis for peptides with a length between 3 and 80 residues using state-of-the-art fully automated instruments based on Fmoc solid-phase technology, employing a microwave-assisted peptide synthesizer. We had established the know-how to select and optimize the appropriate peptide synthesis method for the supply of challenging peptide sequences. All peptides were HPLC purified, analyzed by MALDI-TOF mass spectrometry, and delivered with detailed quality control documentation, including HPLC and MS spectra. In particular, we had optimized special protocols for the incorporation of expensive isotope-labeled amino acids (replacing 12C with 13C, 14N with 15N, and/or 1H with 2H) or other labels such as stable and hydrophilic fluorescence labels (ATTO dyes) to cost-effectively prepare peptides in large quantities (up to 200 mg) with high purities (95% or higher).

 

B17 Force-induced α-β transitions in coiled coil structures

Blank

Coiled coils (CCs) are α-helical structures that occurr in a large number of cytoskeleton and extracellular matrix proteins. Increasing evidence showed that CCs underwent a mechanically induced structural transition into β-sheet structures with possible amyloid-like character; however, the molecular determinants of this α-β transition (αβT) were unknown. This project aimed at unraveling the intrinsic and extrinsic factors that controlled the αβT when applying a shear force as the key constraint. Specifically, it would answer the question of if and how this force-induced αβT depended on CC sequence and length and how it compared to the temperature-induced αβT of CCs. The force-induced αβT would be studied at the single-molecule level using AFM-based single-molecule force spectroscopy (SMFS) and at the ensemble level, where the CCs would serve as physical crosslinks in poly(ethylene glycol)-based biohybrid hydrogels. In the latter case, the hydrogel would act as a force transducer, allowing for mechanically loading the CC crosslinks and observing the αβT in a standard rheology setup.

In the first two funding periods, several CRC projects had developed highly powerful methods for studying the formation of amyloid structures. These methods were now ready to be used for a new model system of high biological relevance, i.e., the force-induced αβT in CCs. Whereas SMFS and rheology would be used for determining the mechanical aspects of the αβT, NMR (Saalwächter, Balbach, Huster) as well as IR (Kremer) and fluorescence spectroscopy (Cichos, Ott) would provide structural and kinetic information. A particular focus would be placed on combining mechanical with structural techniques with the goal of observing the αβT in real-time. These methods would be applied to synthetic CCs with a well-defined and tunable sequence as well as recombinantly expressed natural CC sequences, which were known to undergo a force-induced αβT. This combination would allow for discriminating sequence-specific versus universal features that determined the αβT and its (ir)reversibility.

Highlighted Publications:
  1. Anna-Maria Tsirigoni, Melis Goktas, Zeynep Atris, Angelo Valleriani, Ana Vila Verde, Kerstin G. Blank. Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils. Macromolecular Bioscience (unser virtual issue), bisher early view. 

  2. Emilia M. Grad, Isabell Tunn, Dion Voerman, Alberto S. de Léon, Roel Hammink, and Kerstin G. Blank, Influence of Network Topology on the Viscoelastic Properties of Dynamically Crosslinked HydrogelsFront. Chem. 8, 536 (2020) 

B16 Crystallization of polymer chains under anisotropic confinement in liquid crystals

Mendes Ferreira

The behavior of crystallizable synthetic polymer chains confined in a liquid crystalline matrix had been scarcely investigated, and there were no investigations reported on the potential crystallization of such macromolecules under these conditions. Gaining a more thorough understanding was important, as one example in this context was the incorporation of crystallizable synthetic polymers in cell membranes, a highly relevant biophysical problem, considering the accumulation of plastic marine debris and the consequent potential inclusion of polymer nanoparticles into the food chain, as well as the increasing use of nanoparticles with hydrophobic polymers such as poly(ε-caprolactone) for medical use and other applications. Moreover, it was not known if by crystallizing synthetic polymer chains under confinement in a liquid crystalline matrix, one could control the polymer crystalline morphology by means of the confinement variables, which could potentially motivate technological applications.

The proposed project aimed, therefore, to investigate for the first time how the confinement of crystallizable synthetic polymer chains in anisotropic solvents affected crystallization with respect to nucleation, growth rate, and ultimately the final morphology of polymer crystals. In order to test confinement systems with a wide range of properties, such as spatial dimensions, geometry, and molecular ordering and dynamics, we used distinct liquid crystalline systems, such as phospholipids, surfactants, and amphiphilic block copolymers. For a detailed characterization of the systems, both prior to, during, and after crystallization of the polymer chains under confinement, we used a combination of different experimental and simulation techniques, namely nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), optical microscopy, small/wide-angle X-ray scattering, and molecular dynamics (MD) simulations.

Crystallization under these conditions should have been highly dependent on the conformation adopted and type of partitioning of the chains in the liquid crystalline structure. When the polymer chains aggregated into emulsified microdomain spherical or lens-shaped droplets, the physics of crystallization should have related to the thermodynamics of droplet confinement, while if the chains became dispersed in the liquid crystalline structure, the crystals may have related to solution-grown crystals which, for example, may have pre-crystallized into bundles. The main aim of this project was, therefore, to determine (1) which confinements were adopted by a number of different crystalline polymers, using both homopolymers and amphiphilic block copolymers, and (2) how the confinement types in the liquid crystalline structure affected crystallization.

Highlighted Publications:
  1. Anika Wurl, Maria Ott, Eric Plato, Annette Meister, Farzad Hamdi, Panagiotis L. Kastritis, Alfred Blume, Tiago M. Ferreira, Filling the Gap with Long n-Alkanes: Incorporation of C20 and C30 into Phospholipid Membranes, Langmuir 38, 8595–8606 (2022) 

  2. Anika Wurl, Kay Saalwächter, Tiago Mendes Ferreira, Time-domain R-PDLF NMR for molecular structure determination in complex lipid membranes, Magnetic Resonance, Preprint

B15 Dynamics and association in individualized macromolecules

Tress

Confining polymers to nanometric sizes often interferes with the characteristic length scales of structure formation and thus significantly alters crystallization or nucleation behavior at the nanoscale. To investigate such effects in nanometric samples, past studies relied either on heavily constraining environments like block copolymer mesophases or on deposited droplets that exhibit significant variation in size thus requiring extensive analysis to assign size classes.

In this project, we developed a novel experimental approach to investigate thermodynamic (and also dynamic) phenomena in aggregates of very small numbers of polymer chains with the potential to examine even individualized macromolecules. For that, a highly specialized setup in dielectric spectroscopy, a nanostructured electrode arrangement, is employed. Despite the tremendous increase in sensitivity that can be achieved, this technique does not enable the detection of single or even a few (macro-) molecules. Consequently, ensembles of individual macromolecules or small aggregates must be measured simultaneously; hence the results, representing the ensemble average, can be interpreted as a conformation average of a single macromolecule (or a small aggregate). To ensure the individual character of all molecules (or aggregates) in the ensemble, the approach is combined with three well-known methods of surface modification which keep each molecule (or aggregate) in its own position: First, gold nanoparticles are deposited on the supporting electrode in a pattern of well-defined size and separation by means of block copolymer micelle lithography (BCML). Second, these surfaces are coated with methyl groups by silanazation, which bond to the silica but not to the gold, to reduce the interaction and prevent chain adsorption. Third, the thus prepared surfaces are exposed to a solution of the macromolecule of interest, which carries a thiol end-group in order to bind chemically to the gold nanoparticles. Thereby, the particle size and the size of the macromolecule controls the average number of molecules attached to a single particle.

This enabled the measurement of poly-caprolactone droplets consisting of 10 chains on average for a relatively small molecular weight (Mw=15kg/mol). In contrast to droplets deposited by spin-casting which demonstrate the sensitivity of this method, the grafted droplets do not crystallize. Apparently, the grafted configuration introduces constraints which suppress crystallization entirely, though it is not clear whether limited chain motion or too wide chain spacing prevent crystallization in the grafted aggregates. In contrast, the results on the spin-cast droplets demonstrate the capability of this approach to examine dynamic and thermodynamic phenomena in droplets consisting of very few polymer chains with prospects nearby to study ensembles of individualized molecules.

Highlighted Publications:

 

  1. Wycliffe K. Kipnusu, Martin Tress, and Friedrich Kremer, Glassy Dynamics in Nanometric Confinement of Various Topologies, a Comparison for the Case of Poly(2-vinylpyridine). ACS Symposium Series Chapter 8, 185-201 (2021) 

  2. Martin Tress, Maximillian Vielhauer, Pierre Lutz, Rolf Mülhaupt, Friedrich Kremer, Kunyue Xing, Sirui Ge, Pengfei Cao, Tomonori Saito, and Alexei Sokolov, Polymer Dynamics in Nanostructured Environments: Structure-Property Relations Unraveled by Dielectric Spectroscopy. ACS Symposium Series Chapter 10, 223-238 (2021) 

  3. Jan Philipp Gabriel, Martin Tress, Wilhelm Kossack, Ludwig Popp, Friedrich Kremer, Molecular heterogeneities in the thermal expansivity of polyalcohols. J. Chem. Phys. 154, 024503 (2021) 

B14 Structure formation in linear precision and comb-like polymers under external constraints: Influence of shear fields and interfaces

Beiner

The interplay of ring-like subunits and long methylene sequences determined structural features, properties, and response to external constraints of various polymeric systems. This applied not only to comblike polymers with a rigid backbone and longer methylene units in the side groups, which were in the focus of our investigations in the funding period from 2015 to 2019, but also to linear precision polymers where longer methylene sequences were interrupted by ring-like defects in the main chain. In both cases, we observed the formation of long-range ordered layered structures characterized by alternating domains containing ring-like subunits and methylene sequences. Similar structures also formed in long-chain polyamides, polyesters, polyurethanes, and hybrid systems with linear architecture containing methylene sequences and strongly interacting amino acid units.

Our hypothesis was that in all these cases, different packing states/polymorphs could be formed since the individual subunits had different native lattices and crystallization ranges. We aimed to study the influence of shear fields and strongly interacting fiber surfaces (such as glass or carbon) in order to understand the structural features and properties of these materials. This knowledge would serve as the basis for a rational optimization of such polymers and related composite materials for special applications.

Following the strategy applied in the funding period from 2015 to 2019 to comb-like polymers with rigid backbones, we investigated the influence of constraints produced by shear fields and fiber surfaces on the structural features of linear precision polymers with ring-like defects and a series of long-chain polyamides, polyesters, or polyurethanes with 12-22 CH2 units and strongly interacting “defects” in the funding period from 2019 to 2023 in project B14. Our goal was to determine whether different polymorphic states and phase transitions could be achieved in such systems under constraints. An intrinsic part of this study was to find efficient ways to orient such polymers by shear, on fiber surfaces, or through a combination of both. This approach aimed to improve the mechanical performance of endless fiber reinforced composites based on such polymers perpendicular to the fiber direction. Our final aim was to understand common features and architecture-dependent differences in long-range ordered polymers with a nanolayered structure. We were particularly interested in the role of the independent packing tendencies of ring-like subunits or strongly interacting defects and methylene sequences in the occurrence of polymorphic states. We also incorporated a few hybrid systems combining methylene sequences and amino acids as defects to determine whether similar mechanisms were important for the occurrence of different packing states (misfolding phenomena) in linear biological systems.

Highlighted Publications:
  1. V. Danke, S. Reimann, W. Binder, G. Gupta, M. Beiner, Tuning layered superstructures in precision polymers. Sci. Rep. 10, 12119 (2020) 

  2. V. Danke, G. Gupta, S. Reimann, W. H. Binder, and M. Beiner, Structure formation in nanophase-separated systems with lamellar morphology: Comb- like vs. linear precision polymers. Eur. Polym. J. 103, 116 (2018) 

  3. G. Gupta, V. Danke, T. Babur, M. Beiner, Interrelations between side chain and main chain packing in different crystal modifications of alkoxylated polyesters. J. Phys Chem. B 121, 4583-4591 (2017) 

B13 Probing structural transitions of singlepolymer chains with mechanical stress

Seidel

In our research project, we conducted two distinct investigations. In the first part, we focused on studying structural transitions within single DNA molecules under external stress and negative supertwist. Using ethidium bromide (EtBr), we induced changes in DNA structure and observed an increase in contour length and untwisting of the helix. Through meticulous single-molecule mechanical experiments, we examined the effects of EtBr on DNA’s stretch and twist rigidity. Surprisingly, we discovered that force-induced intercalation played a dominant role in influencing the mechanical properties of the intercalator-complexed DNA. Our findings challenged existing models and pointed towards an anti-cooperative intercalation mechanism. We have submitted a manuscript detailing these exciting discoveries to The Biophysical Journal for review.

In the second part of our project, we aimed to establish mechanical experiments on single synthetic polymer chains to investigate their folding and crystallization behavior. Our objective was to bridge the gap between studies on biological and synthetic polymers by examining isolated polymer chains. To achieve this, we developed a DNA-PEO-DNA hybrid construct that allowed us to manipulate the length of the polymer chain and perform controlled experiments. However, we encountered challenges in establishing the experimental setup, particularly in achieving the desired stoichiometric attachment of PEO chains to DNA molecules. Additionally, finding suitable conditions that would keep DNA handles soluble while promoting polymer chain collapse or crystallization proved to be a complex task. Despite our efforts, we were unable to obtain publishable results in this part of the project. As a result, we decided not to extend project B13.

Throughout the research project, we collaborated with other research groups, including Prof. Jörg Kressler, Frank Cichos, and Maria Ott. These collaborations allowed us to exchange ideas, discuss challenges, and explore different experimental approaches. Their expertise in various aspects, such as coupling PEO chains to DNA and fabricating DNA constructs, greatly contributed to the project. We are grateful for their valuable insights and support.

Highlighted Publication:

J. Dikic and R. Seidel, Anticooperative Binding Governs the Mechanics of Ethidium-Complexed DNA Biophys. J. 116, 1394 (2019)

B12 Mechanisms of early amyloid formation and the confining influence of macromolecular crowding

Ott

The structural flexibility of amyloid peptides comprises the extraordinary property to self-assemble into extended fibrillar structures. Molecular insights into the structure and composition of prefibrillar aggregates were essential for understanding the overall aggregation process. This project aimed to gain a more detailed understanding of the early prefibrillar growth process and the influence of the contiguous environment through the use of single-molecule studies. The resulting distributions of small transient aggregates, called oligomers, along the time course of fibrillation were used to study the pathways of aggregation. Specific properties of the detected oligomers, such as the propensity to disassemble or interact with hydrophobic surfaces, were examined to study their thermodynamic stabilities and increased hydrophobicity. Furthermore, it was demonstrated that the photophysical properties of the fluorescence tags themselves, such as fluorescence lifetime, could distinguish between potentially unstructured oligomers and fibrillar assemblies. Additionally, aggregates that were not consumed by the fibrillation process indicated off-pathway processes and a reduced efficiency of fibrillation.

Methods of single-molecule and time-resolved fluorescence spectroscopy were established to study the early stages of amyloid self-assembly. The influence of commonly used fluorescence tags on the properties of oligomers and fibrils of N-terminal labeled Aβ(1-40) and Aβ(1-42) peptides, which are related to Alzheimer’s disease, was investigated. It was found that the solubility and size distributions of the formed oligomers were influenced not only by the length of the peptides but also by specific fluorophore-peptide interactions. Importantly, a fluorescence tag with the least impact on the peptide aggregation was identified for future work. In preparation for detailed investigations of the effects of macromolecular crowding on early aggregates and the overall fibrillation process, the properties of highly concentrated solutions of globular proteins were studied using a combined approach of small-angle X-ray scattering experiments, NMR, and fluorescence correlation spectroscopy.

The study aimed to be extended in two directions: Firstly, the methodological expertise would be applied to a new peptide, the human parathyroid hormone (PTH), which belongs to the family of functional amyloids. Secondly, the effects of external constraints on amyloid aggregation would be examined. Unlike Aβ peptides, the aggregation process of PTH was reversible, providing insights into the potential key for the non-toxicity of the aggregates – lower thermodynamic stability. Specifically, the size of the critical nucleus would be determined, and its relation to monomer concentration, aggregate size, and propensity for disassembly would be studied. The comparably high monomer concentrations required for PTH fibrillation indicated reduced stabilities of PTH oligomers. Complementary techniques such as fluorescence spectroscopy, small and wide-angle X-ray scattering (SAXS, WAXS), and imaging techniques (Transmission electron microscopy (TEM), atomic force microscopy (AFM)) would be used to characterize the size, structure, and morphology of the formed aggregates. In the second part of the project, the influence of external constraints and specific interactions would be addressed using different proteins and crowding agents. Binding and unbinding kinetics of the amyloid protein and its oligomers with protein crowders would be investigated using single-molecule Förster-resonance energy transfer (FRET) methods in solution. These experiments would help quantify specific interactions and excluded volume effects. Ultimately, comparing the aggregation mechanisms of Aβ peptides and PTH, as well as their potentially different response to external constraints, would deepen the general understanding of the complex interplay between amyloid aggregates and their close environment.

Highlighted Publications:
  1. Luca M. Lauth, Bruno Voigt, Twinkle Bhatia, Lisa Machner, Jochen Balbach, Maria Ott, Heparin promotes rapid fibrillation of the basic parathyroid hormone at physiological pH. FEBS Letters 596, 2928–2939 (2022) 

  2. J. Wägele, S. De Sio, B. Voigt, J. Balbach, and M. Ott, How Fluorescent Tags Modify Oligomer Size Distributions of the Alzheimer Peptide Biophys. J. 116, 227-238 (2019)

  3. De Sio, S, Wägele J, Bhatia, T.,Voigt, B, Lilie H, Ott M. Inherent Adaptivity of Alzheimer Peptides to Crowded Environments, Macromolecular Bioscience. 

B11 Characterization of the self-assembly process of hydrophobins at interfaces and in solution

Hinderberger

Hydrophobins are a class of fungal proteins with unique physical and biological properties. They are highly surface active and amphiphilic, making them the most surface-active proteins known. Hydrophobins play various roles in fungi, including coating/protective functions, adhesion, and surface modification. They are responsible for rendering fungal spores hydrophobic, allowing them to disperse in air and preventing drowning in water-soaked environments. The self-assembly process of hydrophobins is complex and involves interactions at interfaces and surfaces. Class I hydrophobins form rodlet structures, while class II hydrophobins form 2-D crystalline sheets. Understanding the structural rearrangements and self-assembly mechanisms of hydrophobins is an active area of research and has led to industrial applications in foam stabilization, emulsions, and dispersion of insoluble compounds.

Despite the fascinating properties of hydrophobins, their study has faced challenges in obtaining sufficient quantities of the proteins and achieving reproducibility in experiments. Obtaining larger amounts of hydrophobins for research purposes proved to be difficult and time-consuming. However, progress has been made in overcoming these challenges, allowing for the investigation of hydrophobins’ self-assembly using techniques like atomic force microscopy (AFM). The influence of external constraints, such as compression and expansion, on the morphology of hydrophobin films has been explored, shedding light on the importance of sample preparation and handling. In addition to studying hydrophobins at the air-water interface, efforts have been made to investigate their behavior at liquid-liquid interfaces using spin-labeled hydrophobins. Moreover, the genetic engineering of hydrophobins has opened up possibilities for tailoring their properties and creating novel functionalities. Although challenges persist, the study of hydrophobins holds promise for further understanding their unique properties and potential applications in various fields, including biotechnology, materials science, and nanotechnology.

Highlighted Publication:

M. Kordts, M. Kampe, A. Kerth, and D. Hinderberger, Structure Formation in Class I and Class II Hydrophobins at the Air-Water Interface under Multiple Compression/Expansion Cycles ChemistryOpen 7, 1005 (2018)