Understanding the structure and assembly of nanoscale building blocks is vital for the development of biomaterials and is a well-known challenge across a wide range of scientific disciplines, such as pharmaceuticals, construction, and engineering. Scientists in the biological physics, organic and biochemistry communities are especially interested in their self-assembly of organic molecules due to interactions with the aqueous environment. To address this challenge, multiscale approaches are becoming increasingly used as they are often entirely simulation based and each method operates at a different resolution and informs the next scale method, either sequentially or in parallel.
Integrative approaches are also important to consider, as they use experimental data from techniques sensitive to nanoscale structure, such as cryo-EM, small-angle X-ray scattering, and nuclear magnetic resonance, which constrain these simulation approaches and employ machine learning-accelerated methods. One of the best and most powerful techniques for integrative nanoscale modelling is neutron scattering, as neutrons are deeply penetrating, cause no radiation damage and exhibit much greater sensitivity to hydrogen than X-rays.
In the current study, a collaborative team present an integrative small- and wide-angle neutron scattering (SANS/WANS) approach, coupled with computational modelling, to reveal the multiscale structure of the nanoscale β-hairpin, also known as the 'mini-protein,' CLN025. This builds on a continued collaboration between SANS and Disordered materials groups at ISIS and the research group of Professor Lorna Dougan at the University of Leeds. The first author of the paper is Dr Harrison Laurent, a former ISIS facility development student and recent awardee of the Don McKenzie Paul Thesis Prize (please see Related Content). The Don McKenzie Paul Thesis Prize is awarded in recognition of a successfully examined PhD thesis in which the use of neutrons plays a significant role in addressing a scientific challenge or, alternatively, the thesis describes notable development of neutron instrumentation or techniques.
CLN025 is a synthetic 10 residue peptide that was chosen due to its well-defined folded structure and high solubility. It is also of considerable interest, as its fast-folding time means it can be used for all-atom simulations and is rapidly becoming a benchmark for testing new force fields.
Using the instruments NIMROD and Zoom, the team used the data to determine the assembly of the β-hairpin into a hairpin stack. This assembled structure was then studied using the computational modelling technique, empirical potential structure refinement (EPSR) to reveal the hydration of the β-hairpin stack with atomic resolution. This method provided a detailed map of the hydrophobic and hydrophilic character of this model self-assembled biomolecular surface. The study demonstrates the power of a self-consistent cross-length scale approach which models both the large scale self-assembly and small-scale atomic interactions of a β-hairpin as a simple model protein system. This integrated SANS, WANS and EPSR approach could offer significant impact in the study of biomaterials, such as the increasing potential in protein and peptide hydrogels, which have featured in recent highlights here at ISIS. These exciting materials rely on the assembly of functional folded protein or short peptides to form soft materials that can retain large volumes (>90%) of water. Their biocompatibility makes them well suited for a range of applications, including cell culturing, drug delivery, disease modelling, bone regeneration and energy transport.
The project was supported by a grant from the Engineering and Physical Sciences Research Council (EPSRC) (EP/ P02288X/1) and a European Research Council Consolidator Fellowship/ UKRI Frontier Research Fellowship for the MESONET project UKRI (EP/X023524/1).
Visualization of Self-Assembly and Hydration of a β-Hairpin through Integrated Small and Wide-Angle Neutron Scattering | Biomacromolecules (acs.org)
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