Copper is an essential element, but as a result of numerous adverse reactions, it is also a cellular toxin. Nature protects itself from these toxic reactions by binding cuprous copper...

Mammalian metallothioneins (MTs) are important proteins in Zn(II) and Cu(I) homeostasis with the Zn(II) and Cu(I) binding to the 20 cysteines in metal-thiolate clusters. Previous electrospray ionization (ESI) mass spectrometric analyses of Cu(I) binding to Zn7-MT were complicated by significant overlap of the natural abundance isotopic patterns for Zn(II) and Cu(I) leading to impossibly ambiguous stoichiometries. In this paper, isotopically pure 63Cu(I) and 68Zn(II) allowed determination of the specific stoichiometries in the 68Zn,63Cu-βα MT1A species formed following the stepwise addition of 63Cu(I) to 68Zn7-βα MT1A. These species were characterized by ESI-MS and room temperature emission spectroscopy. The key species that form and their emission band centres are Zn5Cu5-βα MT1A (λ = 684 nm), Zn4Cu6-βα MT1A (λ = 750 nm), Zn3Cu9-βα MT1A (λ = 750 nm), Zn2Cu10-βα MT1A (λ = 750 nm), and Zn1Cu14-βα MT1A (λ = 634 nm). The specific domain stoichiometry of each species was determined by assessing the species forming following 63Cu(I) addition to the 68Zn3-β MT1A and 68Zn4-α MT1A domain fragments. The domain fragment emission suggests that Zn5Cu5-βα MT1A contains a Zn1Cu5-β cluster and the Zn4Cu6-βα MT1A, Zn3Cu9-βα MT1A, and Zn2Cu10-βα MT1A each contain a Cu6-β cluster. The species forming with >10 mol. eq. of 63Cu(I) in βα-MT1A exhibit emission from the Cu6-β cluster and an α domain cluster. This high emission intensity is seen at the end of the titrations of 68Zn7-βα MT1A and the 68Zn4-α MT1A domain fragment suggesting that the initial presence of the Zn(II) results in clustered Cu(I) binding in the α domain.

Catalases (CAT) are antioxidant metalloenzymes necessary for life in oxygen-metabolizing cells to regulate H 2 O 2 concentration by accelerating its dismutation. Many physio-pathological situations are associated with oxidative stress resulting from H 2 O 2 overproduction during which antioxidant defenses are overwhelmed. We have used a combinatorial approach associated with an activity-based screening to discover a first peptidyl di copper complex mimicking CAT. The complex was studied in detail and characterized for its CAT activity both in solution and in cells using different analytical methods. The complex exhibited CAT activity in solution and, more interestingly, on HyPer HeLa cells which possess a genetically encoded ratiometric fluorescent sensors of H 2 O 2 . These results highlight the efficiency of a combinatorial approach for the discovery of peptidyl complexes that exhibit catalytic activity.affording the two electrons exchange required for the dismutation reaction. 20,22,23 Small molecular complexes mimicking CAT have been developed to reduce oxidative stress in pathological conditions. [28][29][30] These bioinspired mimics are thus mainly mononuclear (Mn or Fe) porphyrin derivatives or dinuclear manganese complexes analogous to the active site of HemeCAT or MnCAT, respectively. 29 Dinuclear Mn complexes bioinspired from MnCAT are alkoxo, phenoxo, or oxo/carboxylato bridged complexes. In an excellent review, Signorella and Hureau have reported that besides the redox potentials of the metal ions key to catalytic H 2 O 2 dismutation, the efficacy of the complexes is associated with the presence of an intramolecular base to assist in deprotonation. In addition, the presence of a vacant site on the Mn ion is required to coordinate H 2 O 2 , but the complex stability is reduced by the protonation of the bridging ligand. 31 Few mononuclear copper complexes 30,[32][33][34][35][36] have been reported as CAT mimics as well but examples of dinculear copper complexes are very rare. [37][38][39][40] Generally, CAT mimics have been studied in organic solvents or have exhibited activity only at pH above 8. So far, contrarily to SOD mimics, no peptidyl complexes mimicking CAT have been reported, whatever the metal ion. [41][42][43][44] This may be explained by the difficulty to rationally design short peptides able to bind two metal cations (to afford the two required electrons) with appropriate redox potentials and affinities. However, peptidyl ligands are of great interest since their synthesis is very versatile, they are biocompatible and water soluble. But it seems highly complicated to design Mn-based peptidyl complexes since peptide affinity for Mn(II) is usually in the 10 3 -10 6 range at physiological pH even for quite long sequences. [45][46][47] In contrast, short peptide sequences have been described to bind Cu(II) with high affinities (ca. 10 12 -10 15 ). 42,48,49 In this manuscript, we describe implementation of a combinatorial approach to synthesize a library of copper complexes, associated with an ...

Boron difluoride (BF2) formazanate dyes are contenders for molecular species that exhibit a large Stokes shift and bright red emission. Excitation of 3‐cyanoformazanate complexes with 10 μs wide pulses of specific wavelengths resulted in strong luminescence at 663 nm at both room temperature in solution and at 77 K in a frozen solution. Analysis of the short‐lived excitation spectrum from this luminescence shows that it arises from a vibronic manifold of a higher‐lying excited state. This dark state relaxes to the emitting state over 10 μs. TD‐DFT calculations of the two lowest‐energy excited states show that the relaxed geometries are planar for S1 but highly distorted in S2. The specific time‐ and wavelength‐dependence of the excitation profile provides a unique optical encryption capability through the comparison of emission intensities between adjacent vibronic bands only accessible in the 0–12 μs time domain.

The absorption, emission, and electrochemical properties of conjugates of boron difluoride formazanate dyes and Pt(ii)-acetylides are systematically studied.