Competition of Hydrogen Bonds and Coordinate Bonds Induces a Reversible Crystal Transformation

Valorization of Salmo salar Skin Waste for the Synthesis of Angiotensin Converting Enzyme-1 (ACE1) Inhibitory Peptides

One of potential inhibitors which is widely used for the clinical treatment of COVID-19 in comorbid patients is Angiostensin Converting Enzyme-1 (ACE1) inhibitor. A safer peptide-based ACE1 inhibitor derived from salmon skin collagen, that is considered as the by-product of the fish processing industry have been investigated in this study. The inhibitory activity against ACE1 was examined using in vitro and in silico methods. In vitro analysis includes the extraction of acid-soluble collagen, characterization using FTIR, Raman, UV-Vis, XRD, cytotoxicity assay, and determination of inhibition against ACE1. In silico method visualizes binding affinity, molecular interaction, and inhibition type of intact collagen and active peptides derived from collagen against ACE1 using molecular docking. The results of FTIR spectra detected amide functional groups (A, B, I, II, III) and imine proline/hydroxyproline, while the results of Raman displayed peak absorption of amide I, amide III, proline/hydroxyproline ring, phenylalanine, and protein backbone. Furthermore, UV-Vis spectra showed typical collagen absorption at 230 nm and based on XRD data, the chain types in the samples were α-helix. ACE1 inhibition activity was obtained in a concentration-dependent manner where the highest was 82.83% and 85.84% at concentrations of 1000, and 2000 µg/mL, respectively, and showed very low cytotoxicity at the concentration less than 1000 µg/mL. In silico study showed an interaction between ACE1 and collagen outside the active site with the affinity of - 213.89 kcal/mol. Furthermore, the active peptides of collagen displayed greater affinity compared to lisinopril, namely HF (His-Phe), WYT (Trp-Tyr-Thr), and WF (Trp-Phe) of - 11.52; - 10.22; - 9.58 kcal/mol, respectively. The salmon skin-derived collagen demonstrated ACE1 inhibition activity with a non-competitive inhibition mechanism. In contrast, the active peptides were predicted as potent competitive inhibitors against ACE1. This study indicated that valorization of fish by-product can lead to the production of a promising bioactive compound to treat COVID-19 patient with diabetic comorbid.

Graphical Abstract

Elastic and bright assembly-induced luminescent crystals of platinum(II) complexes with near-unity emission quantum yield

Molecular crystals of Pt(II) complexes with metallophilic interactions can provide bright assembly-induced luminescence with colour tunability. However, the brittleness of many of these crystals makes their application in flexible optical materials difficult. Herein, we have achieved the elastic deformation of crystals of polyhalogenated Pt(II) complexes exhibiting bright assembly-induced luminescence. A crystal of [Pt(bpic)(dFppy)] (Hbpic = 5-bromopicolinic acid, HdFppy = 2-(2,4-difluorophenyl)pyridine) and a co-crystal of [Pt(bpic)(dFppy)] and [Pt(bpic)(ppy)] (Hppy = 2-phenylpyridine) were found to exhibit significant elastic deformation due to their highly anisotropic interaction topologies. While the crystal of [Pt(bpic)(dFppy)] exhibited monomer-based ligand-centred ³ππ* emission with an emission quantum yield of 0.40, the co-crystal exhibited bright, triplet metal-metal-to-ligand charge transfer (³MMLCT) emission owing to Pt⋯Pt interactions, thereby achieving a significantly higher emission quantum yield of 0.94.