# From Solution to Surface: How the Catalytic Environment Modulates Peptide Bond Cleavage by Metal‐Oxo Cluster Nanozymes

## TL;DR

Researchers developed a metal-oxo cluster that can cleave peptide bonds in both solution and solid forms, helping to understand how catalyst solubility affects proteolytic reactions.

## Contribution

A tunable, structurally defined metal-oxo cluster enables direct comparison of homogeneous and heterogeneous catalytic behavior in proteolysis.

## Key findings

- Both soluble and insoluble forms of the Hf12 cluster efficiently cleave peptide bonds in glycylglycine and myoglobin.
- The soluble cluster allows mechanistic insights through direct coordination and cooperative binding, while the insoluble form is reusable and structurally stable.
- The study provides a platform to correlate molecular reactivity with macroscopic catalytic behavior across phases.

## Abstract

Nanozymes that selectively cleave proteins offer a promising alternative to natural proteases due to their superior stability, tunability, and scalability. However, they are either water‐soluble, preventing efficient recovery and limiting their practical application, or structurally ill‐defined and insoluble, hindering mechanistic understanding and rational catalyst design. To address this, we developed a structurally well‐defined dodecanuclear hafnium‐based metal‐oxo cluster with a tunable solubility that enables direct comparison of homogeneous and heterogeneous catalytic behavior in peptide bond hydrolysis. The soluble cluster, Hf12(sol), and its insoluble counterpart, Hf12(precip), share identical core structures according to pair distribution function analysis and possess highly similar ligand environments as indicated by solution‐ and solid‐state NMR as well as FT‐IR spectroscopy. We demonstrate that both forms efficiently cleave peptide bonds in the dipeptide glycylglycine and the more complex protein myoglobin. Solution‐based spectroscopic studies with Hf12(sol) show direct coordination of the peptide bond to Hf(IV) centers, with substrate stabilization via cooperative binding to the cluster, whereas Hf12(precip) shows reusability over multiple reaction cycles without loss of structural integrity. This highlights the potential of group IV metal‐oxo clusters as synthetic proteases and offers a rare platform to correlate molecular reactivity with macroscopic catalytic behavior across phases, thereby deepening our understanding of how proteolytic reactions can be modulated by catalyst structure and solubility.

Comparison of homogeneous Hf12(sol) and heterogeneous Hf12(precip) metal‐oxo clusters enables investigation of how solubility influences nanozymatic reactivity and selectivity toward proteolysis, without introducing confounding factors from differences in cluster identity. While the water‐soluble cluster allows performing detailed mechanistic studies, the insoluble cluster can be recycled as catalyst for proteolysis and is easier to implement as nanozyme in proteomics applications.