The dysregulation of protein–protein interactions (PPIs) in disease states is well established, yet they are challenging to target, owing to the large surface area and featureless nature of protein binding interfaces. For targeting helix-mediated interactions, α-helix mimetics present a promising strategy. These are versatile small molecule scaffolds, capable of mimicking the hotspot residues on an α-helix. A wide range of such scaffolds have been reported, yet their target protein selectivity in the context of a whole proteome requires further exploration. Here, we report the affinity-based protein profiling of three structurally distinct classes of α-helix mimetics, N-substituted oligobenzamides, pyrrolopyrimidines, and oxopiperazines. This represents the first direct cross-comparison of different helix mimetic scaffolds, revealing significant differences in proteome-wide selectivity.
Amrita Date, Archie Wall, Hannah Kiely-Collins et al.· RSC Chemical Biology· 0 citations
We probe the structural and rheological properties of ionically crosslinked alginate, a model biopolymer hydrogel, using microscopy, rheology and viscosity dependent molecular probes. This combination of techniques enables the quantification and correlation of microstructure, microviscosity, bulk viscoelasticity and yielding dynamics. By adjusting the stoichiometric ratio, R, between the alginate biopolymer and its cation crosslinks, we observe a transition from a homogeneous network-like structure to a coarse bundle-like structure at high (R>0.67) stoichiometric ratio. Intriguingly, these bundle-like structures have distinct and counter-intuitive rheological properties. Using molecular probes, we observe a continuous decrease in microviscosity that is correlated with a decrease in bulk elastic modulus and an increase in energy dissipation. This is accompanied by a transition in the hydrogel yielding under strain from a sharp, well-defined yield point to a continuous ductile-like yielding. We ascribe these surprising transitions to the looser intermolecular interaction between alginate biopolymers in the bundle-like state, as previously predicted by x-ray scattering experiments. These findings reveal new and counter-intuitive structure-property relations that demonstrate high crosslink concentration does not necessarily translate to optimal mechanical performance. Significance Alginate is a polysaccharide biopolymer naturally found in brown seaweed cell walls. Extracted alginate forms ionically crosslinked hydrogels that are strong, flexible and increasingly valuable in the biomedical, packaging and food industries. A large part of the utility of these hydrogels stems from the ease with which their mechanics can be tuned through adjusting the stoichiometry between alginate and its ionic crosslinks. However, little is known about how the material properties of alginate hydrogels, in particular their rheology and dynamics, are affected by microscale structural transitions at high stoichiometric ratios. Here, we use a multi-modal approach to describe and correlate hydrogel material properties and to demonstrate that increased polymer crosslinking can, counterintuitively, sometimes weaken hydrogel performance.
Vinay Kopnar, P. Sherin, Sarah P. Graham et al.· bioRxiv· 0 citations
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