Do Rhodium(III) Complexes Behave as Biocompatible Materials for α-Chymotrypsin Structural Stability and Activity?

In this research study, a series of four acyl thiourea ligands and their corresponding rhodium(III) pentamethylcyclopentadienyl complexes, designated as Rh1, Rh2, Rh3, and Rh4, were successfully used to explore their suitability for a biological macromolecule, i.e., α-chymotrypsin (α-CT). Through meticulous analysis of the spectroscopic data, it was convincingly established that the acyl thiourea ligands served as neutral and monodentate ligands in their interaction with the Rh(III) ions. Specifically, the spectroscopic evidence confirmed that the sulfur (S) atoms within the acyl thiourea ligands formed coordinated bonds with the Rh(III) ions. This crucial finding elucidates the specific coordination mode and binding interactions between the ligands and the central Rh(III) metal ion, which have seldom been investigated. Importantly, various biophysical studies and enzymatic activity results suggested that the structural stability of α-CT was maintained in these Rh(III) complexes. Interestingly, the metal complexes enhanced the thermal stability of α-CT, as indicated by an increase in the transition temperature (<i>T</i>_m) of α-CT. This study unveils the promising role of Rh(III) metal complexes in the stabilization and activation of the biological macromolecule, which further holds potential in industrial and biomedical applications.