The development of bioscaffolds for cardiovascular medical applications, such as peripheral artery disease (PAD), remains to be a challenge for tissue engineering. PAD is an increasingly common and serious cardiovascular illness characterized by progressive atherosclerotic stenosis, resulting in decreased blood perfusion to the lower extremities. Percutaneous transluminal angioplasty and stent placement are routinely performed on these patients with suboptimal outcomes. Natural Vascular Scaffolding (NVS) is a novel treatment in the development for PAD, which offers an alternative to stenting by building on the natural structural constituents in the extracellular matrix (ECM) of the blood vessel wall. During NVS treatment, blood vessels are exposed to a photoactivatable small molecule (10-8-10 Dimer) delivered locally to the vessel wall via an angioplasty balloon. When activated with 450 nm wavelength light, this therapy induces the formation of covalent protein–protein crosslinks of the ECM proteins by a photochemical mechanism, creating a natural scaffold. This therapy has the potential to reduce the need for stent placement by maintaining a larger diameter post-angioplasty and minimizing elastic recoil. Experiments were conducted to elucidate the mechanism of action of NVS, including the molecular mechanism of light activation and the impact of NVS on the ECM.

The human protein histidine phosphatase PHPT1 is involved in several important cellular pathways and has been implicated in various cancers. However, the biological roles of this enzyme are not well understood due to a lack of chemical tools that enable its study. Herein we have identified phenylarsonic acids as general scaffolds which inhibit PHPT1 activity. Notably, phenylarsonic acids can be embedded into peptide sequences, providing the first known peptide-based inhibitors of PHPT1. In a counterscreen against a small panel of phosphatases, we demonstrate that these compounds exhibit some selectivity for PHPT1. Moreover, we show that these compounds exhibit mixed inhibition. We provide evidence that reduction of the phenylarsonic acids in situ by reducing agents like dithiothreitol (DTT) to provide phenylarsine species gives rise to the observed PHPT1 inhibition. These As(III) species are known to be thiophilic and can interact with solvent-exposed cysteine residues of proteins. Finally, we demonstrate that mutating the three cysteine residues of PHPT1 to alanine results in a significant decrease in enzyme inhibition by the phenylarsonic acids, suggesting that these compounds likely interact at least in part with Cys residues in PHPT1.

Inspired by Nature’s wide range of oxidation-induced modifications to install cross-links and cycles at tyrosine (Tyr) and other phenol-containing residue side chains, we report a Tyr-selective strategy for the preparation of Tyr-linked cyclic peptides. This approach leverages N4-substituted 1,2,4-triazoline-3,5-diones (TADs) as azo electrophiles that react chemoselectively with the phenolic side chain of Tyr residues to form stable C–N1-linked cyclic peptides. In the developed method, a precursor 1,2,4-triazolidine-3,5-dione moiety, also known as a urazole, is readily constructed at any free amine revealed on a solid-supported peptide. Once prepared, the N4-substituted urazole peptide is selectively oxidized using mild, peptide-compatible conditions to generate an electrophilic N4-substituted TAD peptide intermediate that reacts selectively under aqueous conditions with internal and terminal Tyr residues to furnish Tyr-linked cyclic peptides. The approach demonstrates good tolerance of native residue side chains and enables access to cyclic peptides ranging from 3- to 11-residues in size (16- to 38-atom-containing cycles). The identity of the installed Tyr-linkage, a stable covalent C–N1 bond, was characterized using NMR spectroscopy. Finally, we applied the developed method to prepare biologically active Tyr-linked cyclic pep-tides bearing the integrin-binding RGDf epitope.