[en] We report the first characterization of the in vivo porphyrin scavenging abilities of two components of a newly discovered heme scavenging system involving iron-regulated surface determinant (Isd) proteins. These proteins are present within the cell envelope of the Gram-positive human pathogen Staphylococcus aureus. IsdC and IsdE, when expressed heterologously in Escherichia coli, efficiently scavenged intracellular heme and resulted in de novo heme synthesis in excess of 100-fold above background. Magnetic circular dichroism analyses showed that the heme-binding properties of the two proteins differ significantly from one another. IsdC bound almost exclusively free-base protoporphyrin IX, whereas the IsdE protein was associated with low spin Fe(III) and Fe(II) heme. These properties provide important insight into the possible mechanisms of iron scavenging from bound heme by Isd proteins

[en] The two-domain (βα) mammalian metallothionein binds seven divalent metals, however, the binding mechanism is not well characterized and recent reports require the presence of the partially metallated protein. In this paper, step-wise metallation of the metal-free, two-domain βα-rhMT and the isolated β-rhMT using Cd(II) is shown to proceed in a noncooperative manner by analysis of electrospray ionization mass spectrometric data. Under limiting amounts of Cd(II), all intermediate metallation states up to the fully metallated Cd₃-β-rhMT and Cd₇-βα-rhMT were observed. Addition of excess Cd(II), resulted in formation of the supermetallated (metallation in excess of normal levels) Cd₄-β- and Cd₈-βα-metallothionein species. These data establish that noncooperative cadmium metallation is a property of each isolated domain and the complete two-domain protein. Our data now also establish that supermetallation is a property that may provide information about the mechanism of metal transfer to other proteins

[en] The earthworm Lumbricus rubellus has been found to inhabit cadmium-rich soils and accumulate cadmium within its tissues. Two metallothionein (MT) isoforms (1 and 2) have been identified and cloned from L. rubellus. In this study, we address the metalation status, metal coordination, and structure of recombinant MT-2 from L. rubellus using electrospray ionization mass spectrometry (ESI-MS), UV absorption, and circular dichroism (CD) spectroscopy. This is the first study to show the detailed mass and CD spectral properties for the important cadmium-containing earthworm MT. We report that the 20-cysteine L. rubellus MT-2 binds seven Cd²⁺ ions. UV absorption and CD spectroscopy and ESI-MS pH titrations show a distinct biphasic demetalation reaction, which we propose results from the presence of two metal-thiolate binding domains. We propose stoichiometries of Cd₃Cys₉ and Cd₄Cys₁₁ based on the presence of 20 cysteines split into two isolated regions of the sequence with 11 cysteines in the N-terminal and 9 cysteines in the C-terminal. The CD spectrum reported is distinctly different from any other metallothionein known suggesting quite different binding site structure for the peptide

[en] Boron difluoride (BF${}_2$) 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 S${}_1$ but highly distorted in S${}_2$. 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. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

[en] Cadmium-metallothioneins (Cd-MT) are small proteins containing seven cadmium atoms in a tetrahedral arrangement of sulfur atoms. Comparison of experimental X-ray absorption fine structure (XAFS) with theoretical full multiple-scattering XAFS spectra have been used as a tool for verification of the structural models generated using both available experimental NMR data and theoretical simulations on the basis of molecule mechanics/molecular dynamics (MM/MD) and density functional theory (DFT)

[en] Metallothioneins are the proteins containing seven Cd atoms in tetrahedral arrangement of S atoms. For this compound full multiple scattering XAFS calculations have been used as a tool for verification of structural models generated using molecular dynamic. To determine the sensitivity of the spectrum to different structural parameters and to check does the best-fit XANES spectrum correspond to the correct structure of the complex we have tested method for Cd(SPh)₄ model compound