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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 (MS) analyses of Cu(I) binding to Zn$_7$-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 $^{63}$Cu(I) and $^{68}$Zn(II) allowed determination of the specific stoichiometries in the $^{68}$Zn,$^{63}$Cu-βα MT1A species formed following the stepwise addition of $^{63}$Cu(I) to $^{68}$Zn$_7$-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 Zn$_5$Cu$_5$-βα MT1A (λ = 684 nm), Zn$_4$Cu$_6$-βα MT1A (λ = 750 nm), Zn$_3$Cu$_9$-βα MT1A (λ = 750 nm), Zn$_2$Cu$_{10}$-βα MT1A (λ = 750 nm), and Zn$_1$Cu$_{14}$-βα MT1A (λ = 634 nm). The specific domain stoichiometry of each species was determined by assessing the species forming following $^{63}$Cu(I) addition to the $^{68}$Zn$_3$-β MT1A and $^{68}$Zn$_4$-α MT1A domain fragments. The domain fragment emission suggests that Zn$_5$Cu$_5$-βα MT1A contains a Zn$_1$Cu$_5$-β cluster and the Zn$_4$Cu$_6$-βα MT1A, Zn$_3$Cu$_9$-βα MT1A, and Zn$_2$Cu$_{10}$-βα MT1A each contain a Cu$_6$-β cluster. The species forming with >10 mol. eq. of $^{63}$Cu(I) in βα-MT1A exhibit emission from the Cu$_6$-β cluster and an α domain cluster. This high emission intensity is seen at the end of the titrations of $^{68}$Zn$_7$-βα MT1A and the $^{68}$Zn$_4$-α MT1A domain fragment suggesting that the initial presence of the Zn(II) results in clustered Cu(I) binding in the α domain.

The combination of π-conjugated organic compounds and Pt(II)-acetylides is a powerful strategy for the production of functional optoelectronic materials. The presence of the heavy element, Pt, in these compounds enhances electronic delocalization generally resulting in low-energy absorption and emission maxima and often leads to intersystem crossing, resulting in phosphorescence. When boron complexes of N-donor ligands, such as boron dipyrromethenes (BODIPYs), are involved the molecular and polymeric materials produced have properties that are advantageous for their use as oxygen-sensors, in triplet–triplet annihilation, and as the functional components of photovoltaics. Based on these exciting results, we endeavored to thoroughly examine the effect of Pt(II)-acetylide conjugation on the properties of BF2 formazanate dyes, which offer improved redox properties and red-shifted absorption and emission bands compared to many structurally related BODIPYs. The results showed that phosphine-supported Pt(II)-acetylide incorporation enhanced electronic conjugation, rendering the electrochemical reduction of the BF2 formazanate dyes more difficult, while also red-shifting their absorption and emission maxima. Unlike similar BODIPYs, the presence of Pt(II) did not facilitate phosphorescence, but rather quenched fluorescence. This study provides significant insights into structure–property relationships and guiding principles for the design of BF2 formazanate dyes, a rapidly emerging family of readily accessible optoelectronic materials.

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.

International audience; 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.

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 to chaperones and other metalloproteins. Metallothionein has been proposed as a storage location for Cu(i) and potentially as the donor of Cu(i) to copper-dependent enzymes. We report that the addition of Cu(i) to apo recombinant human metallothionein 1a cooperatively forms a sequential series of Cu(i)–cysteinyl thiolate complexes that have specific Cu(i) : MT stoichiometries of 6 : 1, 10 : 1, and finally 13 : 1. The individual domain Cu : SCys stoichiometries were determined as Cu6S9 (for 6 : 1), Cu6S9 + Cu4S6 (for 10 : 1), and Cu6S9 + Cu7S9 (for 13 : 1) based on the number of modified free cysteines not involved in Cu(i) binding. The stoichiometries are associated with Cu–SCys cluster formation involving bridging thiols in the manner similar to the clusters formed with Cd(ii) and Zn(ii). The locations of these clustered species within the 20 cysteine full protein were determined from the unique speciation profiles of Cu(i) binding to the β and α domain fragments of recombinant human metallothionein 1a with 9 and 11 cysteines, respectively. Competition reactions using these domain fragments challenged Cu(i) metallation of the βα protein, allowing the sequence of cluster formation in the full protein to be determined. Relative binding constants for each Cu(i) bound are reported. The emission spectra of the Cu4S6, Cu6S9, and Cu7S9 clusters have unique λmax and phosphorescent lifetime properties. These phosphorescent data provide unambiguous supporting evidence for the presence of solvent shielded clusters reported concurrently by ESI-MS. Simulated emission spectra based on the cluster specific emission profiles matched the experimental spectra and are used to confirm that the relative concentrations seen by ESI-MS are representative of the solution. Our results suggest that the availability of a series of sequential Cu(i)–thiolate clusters provides flexibility as a means of protecting the cell from toxicity while still allowing for homeostatic control of the total copper content in the cell. This mechanism provides a dynamic and reactive method of reducing the cellular free copper concentrations.

The combination of π-conjugated organic compounds and Pt(ii)-acetylides is a powerful strategy for the production of functional optoelectronic materials. The presence of the heavy element, Pt, in these compounds enhances electronic delocalization generally resulting in low-energy absorption and emission maxima and often leads to intersystem crossing, resulting in phosphorescence. When boron complexes of N-donor ligands, such as boron dipyrromethenes (BODIPYs), are involved the molecular and polymeric materials produced have properties that are advantageous for their use as oxygen-sensors, in triplet-triplet annihilation, and as the functional components of photovoltaics. Based on these exciting results, we endeavored to thoroughly examine the effect of Pt(ii)-acetylide conjugation on the properties of BF2 formazanate dyes, which offer improved redox properties and red-shifted absorption and emission bands compared to many structurally related BODIPYs. The results showed that phosphine-supported Pt(ii)-acetylide incorporation enhanced electronic conjugation, rendering the electrochemical reduction of the BF2 formazanate dyes more difficult, while also red-shifting their absorption and emission maxima. Unlike similar BODIPYs, the presence of Pt(ii) did not facilitate phosphorescence, but rather quenched fluorescence. This study provides significant insights into structure-property relationships and guiding principles for the design of BF2 formazanate dyes, a rapidly emerging family of readily accessible optoelectronic materials.