Biology subjects

Farsheed, A. C.

Publications and source records attributed to Farsheed, A. C..

3 recordsLinked to original sources

bioRxiv2024

Covalent Stabilization of Collagen Mimetic Triple Helices and Assemblies by Dopa Crosslinking

Creating thermally stable collagen mimetic peptides (CMPs) is a persistent challenge. Nature leverages covalent crosslinkings to stabilize collagens signature triple helical tertiary structure and higher-order assemblies. Herein, we demonstrate that crosslinkings between levodopa (Dopa) and lysine, amino acids present in native collagen, can covalently stabilize the triple helix in collagen mimetic peptides. Since alkaline conditions catalyze the oxidation of the catechol on Dopa to a benzoquinone, while being in proximity to the nucleophilic lysine, we hypothesized that this reaction could be a facile method to covalently capture the supramolecular structure of CMPs by simply increasing the pH of the aqueous solvent with the addition of sodium hydroxide. This covalent capture strategy successfully stabilizes CMP homotrimers and a de novo designed ABC-type heterotrimer demonstrating that the Lysine-Dopa covalent bond is best templated by a supramolecular, axial cation-{pi} pairwise interaction. In nature, collagen can hierarchically assemble into fibers. This behavior can be mimicked with the self-assembly of CMPs, but the resulting nanofibers typically exhibit thermal stability below body temperature. In a final application, we demonstrate that Dopa-Lysine covalent capture also enhances the thermal stability of CMP nanofibers well above 37 {degrees}C. This biomimetic covalent capture strategy can stabilize a wide variety of CMP systems and potentially enable the biomedical application of these materials.

biochemistry↗

bioRxiv2024

Beyond the Triple Helix: Exploration of the Hierarchical Assembly Space of Collagen-like Peptides

The de novo design of self-assembling peptides has garnered significant attention in scientific research. While alpha-helical assemblies have been extensively studied, exploration of polyproline type II (PPII) helices, such as those found in collagen, remains relatively limited. In this study, we focused on understanding the sequence-structure relationship in hierarchical assemblies of collagen-like peptides, using defense collagen SP-A as a model. By dissecting the sequence derived from SP-A and synthesizing short collagen-like peptides, we successfully constructed a discrete bundle of hollow triple helices. Mutation studies pinpointed amino acid sequences, including hydrophobic and charged residues that are critical for oligomer formation. These insights guided the de novo design of collagen-like peptides, resulting in the formation of diverse quaternary structures, including discrete and heterogenous bundled oligomers, 2D nanosheets, and pH-responsive nanoribbons. Our study represents a significant advancement in the understanding and harnessing of collagen higher-order assemblies beyond the triple helix.

biophysics↗

bioRxiv2024

Tunable Macroscopic Alignment of Self-Assembling Peptide Nanofibers

Fibrous proteins that comprise the extracellular matrix (ECM) guide cellular growth and tissue organization. A lack of synthetic strategies able to generate aligned, ECM-mimetic biomaterials has hampered bottom-up tissue engineering of anisotropic tissues and led to a limited understanding of cell-matrix interactions. Here, we present a facile extrusion-based fabrication method to produce anisotropic, nanofibrous hydrogels using self-assembling peptides. The application of shear force coinciding with ion-triggered gelation is used to kinetically trap supramolecular nanofibers into aligned, hierarchical structures. We establish how modest changes in phosphate buffer concentration during peptide self-assembly can be used to tune their alignment and packing. In addition, increases in the nanostructural anisotropy of fabricated hydrogels are found to enhance their strength and stiffness under hydrated conditions. To demonstrate their utility as an ECM-mimetic biomaterial, aligned nanofibrous hydrogels are used to guide directional spreading of multiple cell types, but strikingly, increased matrix alignment is not always correlated with increased cellular alignment. Nanoscale observations reveal differences in cell-matrix interactions between variably aligned scaffolds and implicate the need for mechanical coupling for cells to understand nanofibrous alignment cues. In total, innovations in the supramolecular engineering of self-assembling peptides allow us to generate a gradient of anisotropic nanofibrous hydrogels, which are used to better understand directed cell growth.

bioengineering↗