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Many bacteria secrete metallophores, low-molecular-weight organic compounds that bind ions with high selectivity and affinity, in order to access essential metals from the environment. Previous work has elucidated the structures and biosynthetic machinery of metallophores specific for iron, zinc, nickel, molybdenum, and copper. No physiologically relevant lanthanide-binding metallophore has been discovered despite the knowledge that lanthanide metals (Ln) have been revealed to be essential cofactors for certain alcohol dehydrogenases across a diverse range of phyla. Here, we report the biosynthetic machinery, the structure, and the physiological relevance of a lanthanophore, methylolanthanin. The structure of methylolanthanin exhibits a unique 4-hydroxybenzoate moiety which has not previously been described in other metallophores. We find that production of methylolanthanin is required for normal levels of Ln accumulation in the methylotrophic bacterium Methylobacterium extorquens AM1, while overexpression of the molecule greatly increases bioaccumulation and adsorption. Our results provide a clearer understanding of how Ln-utilizing bacteria sense, scavenge, and store Ln; essential processes in the environment where Ln are poorly bioavailable. More broadly, the identification of this lanthanophore opens doors for study of how biosynthetic gene clusters are repurposed for additional functions and the complex relationship between metal homeostasis and fitness. [ABSTRACT FROM AUTHOR]

The synthesis of a series of octadentate ligands containing the 1-hydroxypyridin-2-one (1,2-HOPO) group in complex with europium(III) is reported. Within this series, the central bridge connecting two diethylenetriamine units linked to two 1,2-HOPO chromophores at the extremities (5-LIN-1,2-HOPO) is varied from a short ethylene chain (H(2,2)-1,2-HOPO) to a long pentaethylene oxide chain (H(17O5,2)-1,2-HOPO). The thermodynamic stability of the europium complexes has been studied and reveals these complexes may be effective for biological measurements. Extension of the central bridge results in exclusion of the inner-sphere water molecule observed for [Eu(H(2,2)-1,2-HOPO)](-) going from a nonacoordinated to an octacoordinated Eu(III) ion. With the longer chain length ligands, the complexes display increased luminescence properties in aqueous medium with an optimum of 20% luminescence quantum yield for the [Eu(H(17O5,2)-1,2-HOPO)](-) complex. The luminescence properties for [Eu(H(14O4,2)-1,2-HOPO)](-) and [Eu(H(17O5,2)-1,2-HOPO)](-) are better than that of the model bis-tetradentate [Eu(5LIN(Me)-1,2-HOPO)2](-) complex, suggesting a different geometry around the metal center despite the geometric freedom allowed by the longer central chain in the H(mOn,2) scaffold. These differences are also evidenced by examining the luminescence spectra at room temperature and at 77 K and by calculating the luminescence kinetic parameters of the europium complexes.

The synthesis of a series of octadentate ligands containing the 1-hydroxypyridin-2-one (1,2-HOPO) group in complex with europium(III) is reported. Within this series, the central bridge connecting two diethylenetriamine units linked to two 1,2-HOPO chromophores at the extremities (5-LIN-1,2-HOPO) is varied from a short ethylene chain (H(2,2)-1,2-HOPO) to a long pentaethylene oxide chain (H(17O5,2)-1,2-HOPO). The thermodynamic stability of the europium complexes has been studied and reveals these complexes may be effective for biological measurements. Extension of the central bridge results in exclusion of the inner-sphere water molecule observed for [Eu(H(2,2)-1,2-HOPO)](-) going from a nonacoordinated to an octacoordinated Eu(III) ion. With the longer chain length ligands, the complexes display increased luminescence properties in aqueous medium with an optimum of 20% luminescence quantum yield for the [Eu(H(17O5,2)-1,2-HOPO)](-) complex. The luminescence properties for [Eu(H(14O4,2)-1,2-HOPO)](-) and [Eu(H(17O5,2)-1,2-HOPO)](-) are better than that of the model bis-tetradentate [Eu(5LIN(Me)-1,2-HOPO)2](-) complex, suggesting a different geometry around the metal center despite the geometric freedom allowed by the longer central chain in the H(mOn,2) scaffold. These differences are also evidenced by examining the luminescence spectra at room temperature and at 77 K and by calculating the luminescence kinetic parameters of the europium complexes.

We report the preparation and new insight into photophysical properties of luminescent hydroxypyridonate complexes [M(III)L](-) (M = Eu or Sm) of the versatile 3,4,3-LI(1,2-HOPO) ligand (L). We report the crystal structure of this ligand with Eu(III) as well as insights into the coordination behavior and geometry in solution by using magnetic circular dichroism. In addition TD-DFT calculations were used to examine the excited states of the two different chromophores present in the 3,4,3-LI(1,2-HOPO) ligand. We find that the Eu(III) and Sm(III) complexes of this ligand undergo a transformation after in situ preparation to yield complexes with higher quantum yield (QY) over time. It is proposed that the lower QY in the in situ complexes is not only due to water quenching but could also be due to a lower degree of f-orbital overlap (in a kinetic isomer) as indicated by magnetic circular dichroism measurements.

As a symbol of the power and majesty of science, the periodic table has inspired many scientists-to-be to investigate the deep secrets of nature through the study of chemistry. In the spirit of inclusion, blind students too deserve and need to have their curiosity about the inner workings of nature stimulated through greater exposure to this symbol and tool of science. To this end, the authors have designed two accessible electronic periodic tables that are available for immediate download without charge: One version, the Cal Poly DAISY Periodic Table (CP-DPT), is in the DAISY format and is designed to be used on digital audio devices and electronic Braille note takers; the other version, the Cal Poly Excel Periodic Table (CP-EPT), is an Excel workbook and is accessed with a screen reader-equipped personal computer. Both versions contain data and descriptive information about the elements. We believe that distribution of these tables will aid the dissemination of chemical knowledge, and support STEM education for blind students. This report also evaluates periodic tables presented in Braille and audio-tactile formats. In addition, periodic tables available on the Web are evaluated in relation to screen reader access. HTML tables created according to standard Web content accessibility guidelines can be entirely accessible, whereas PDF and FLASH formatted tables were found to be largely inaccessible. Hence, HTML is the preferred format for accessible tables.

Pyrroloquinoline quinone (PQQ) is an important cofactor of methanol dehydrogenases and glycose dehydrogenases. In addition, isolated PQQ is used as a central component in sensors and biomimetic complexes. The synthesis of PQQ derivatives is of interest for developing new alcohol oxidation catalysts and redox sensors. This work describes a modular synthesis for derivatives of PQQ bearing methyl and ketone groups instead of carboxylic acid moieties. These modifications reduce the possible coordination sites of PQQ for metal ions outside the protein environment. [ABSTRACT FROM AUTHOR]

Because of their use in high technologies like computers, smartphones and renewable energy applications, lanthanides (belonging to the group of rare earth elements) are essential for our daily lives. A range of applications in medicine and biochemical research made use of their photo-physical properties. The discovery of a biological role for lanthanides has boosted research in this new field. Several methanotrophs and methylotrophs are strictly dependent on the presence of lanthanides in the growth medium while others show a regulatory response. After the first demonstration of a lanthanide in the active site of the XoxF-type pyrroloquinoline quinone methanol dehydrogenases, follow-up studies showed the same for other pyrroloquinoline quinone-containing enzymes. In addition, research focused on the effect of lanthanides on regulation of gene expression and uptake mechanism into bacterial cells. This review briefly describes the discovery of the role of lanthanides in biology and focuses on open questions in biological lanthanide research and possible application of lanthanide-containing bacteria and enzymes in recovery of these special elements. [ABSTRACT FROM AUTHOR]