Luminescent Ruthenium(II) Polypyridyl Functionalized Gold Nanoparticles; Their DNA Binding Abilities and Application As Cellular Imaging Agents

The synthesis and photophysical and biological investigation of Ru(II)-polypyridyl stabilized watersoluble, luminescent gold nanoparticles (AuNPs) are described. These structures bind to DNA and undergo rapid cellular uptake, being localized within the cell cytoplasm and nucleus within 4 h

A Major Role of the RecFOR Pathway in DNA Double-Strand-Break Repair through ESDSA in Deinococcus radiodurans

In Deinococcus radiodurans, the extreme resistance to DNA–shattering treatments such as ionizing radiation or desiccation is correlated with its ability to reconstruct a functional genome from hundreds of chromosomal fragments. The rapid reconstitution of an intact genome is thought to occur through an extended synthesis-dependent strand annealing process (ESDSA) followed by DNA recombination. Here, we investigated the role of key components of the RecF pathway in ESDSA in this organism naturally devoid of RecB and RecC proteins. We demonstrate that inactivation of RecJ exonuclease results in cell lethality, indicating that this protein plays a key role in genome maintenance. Cells devoid of RecF, RecO, or RecR proteins also display greatly impaired growth and an important lethal sectoring as bacteria devoid of RecA protein. Other aspects of the phenotype of recFOR knock-out mutants paralleled that of a ΔrecA mutant: ΔrecFOR mutants are extremely radiosensitive and show a slow assembly of radiation-induced chromosomal fragments, not accompanied by DNA synthesis, and reduced DNA degradation. Cells devoid of RecQ, the major helicase implicated in repair through the RecF pathway in E. coli, are resistant to γ-irradiation and have a wild-type DNA repair capacity as also shown for cells devoid of the RecD helicase; in contrast, ΔuvrD mutants show a markedly decreased radioresistance, an increased latent period in the kinetics of DNA double-strand-break repair, and a slow rate of fragment assembly correlated with a slow rate of DNA synthesis. Combining RecQ or RecD deficiency with UvrD deficiency did not significantly accentuate the phenotype of ΔuvrD mutants. In conclusion, RecFOR proteins are essential for DNA double-strand-break repair through ESDSA whereas RecJ protein is essential for cell viability and UvrD helicase might be involved in the processing of double stranded DNA ends and/or in the DNA synthesis step of ESDSA

“Oxidative Addition” of Halogens to Uranium(IV) Bis(amidophenolate) Complexes

A series of U­(IV) complexes, (^Rap)₂U­(THF)₂ [R = <i>tert-</i>butyl (<i>t</i>-Bu) (<b>1</b>), adamantyl (Ad) (<b>2</b>), diisopropylphenyl (dipp) (<b>3</b>)], supported by the redox-active 4,6-di-<i>tert</i>-butyl-2-(R)­amidophenolate ligand, have been synthesized by salt metathesis of 2 equiv of the alkali metal salt of the ligand, M₂[^Rap] [M = K (<b>1</b> and <b>2</b>), Na (<b>3</b>)], with UCl₄. Exposure of these uranium complexes to 1 equiv of PhICl₂ results in oxidative addition to uranium, forming the bis-(4,6-di-<i>tert</i>-butyl-2-(R)­iminosemiquinone) ([^Risq]^1–) uranium­(IV) dichloride dimer, [(^Risq)₂UCl]₂(μ²-Cl)₂ [R = <i>t</i>-Bu (<b>4</b>), Ad (<b>5</b>), dipp (<b>6</b>)]. The addition of iodine to <b>1</b> forms (^tBuisq)₂UI₂(THF) (<b>7</b>), while the reactivity of I₂ with <b>2</b> and <b>3</b> results in decomposition. Complexes <b>1</b>–<b>7</b> have been characterized by ¹H NMR and electronic absorption spectroscopies. X-ray crystallography was employed to elucidate structural parameters of <b>2</b>, <b>3</b>, <b>5</b>, and <b>7</b>

“Oxidative Addition” of Halogens to Uranium(IV) Bis(amidophenolate) Complexes

A series of U­(IV) complexes, (^Rap)₂U­(THF)₂ [R = <i>tert-</i>butyl (<i>t</i>-Bu) (<b>1</b>), adamantyl (Ad) (<b>2</b>), diisopropylphenyl (dipp) (<b>3</b>)], supported by the redox-active 4,6-di-<i>tert</i>-butyl-2-(R)­amidophenolate ligand, have been synthesized by salt metathesis of 2 equiv of the alkali metal salt of the ligand, M₂[^Rap] [M = K (<b>1</b> and <b>2</b>), Na (<b>3</b>)], with UCl₄. Exposure of these uranium complexes to 1 equiv of PhICl₂ results in oxidative addition to uranium, forming the bis-(4,6-di-<i>tert</i>-butyl-2-(R)­iminosemiquinone) ([^Risq]^1–) uranium­(IV) dichloride dimer, [(^Risq)₂UCl]₂(μ²-Cl)₂ [R = <i>t</i>-Bu (<b>4</b>), Ad (<b>5</b>), dipp (<b>6</b>)]. The addition of iodine to <b>1</b> forms (^tBuisq)₂UI₂(THF) (<b>7</b>), while the reactivity of I₂ with <b>2</b> and <b>3</b> results in decomposition. Complexes <b>1</b>–<b>7</b> have been characterized by ¹H NMR and electronic absorption spectroscopies. X-ray crystallography was employed to elucidate structural parameters of <b>2</b>, <b>3</b>, <b>5</b>, and <b>7</b>

Synthesis and Reactivity of Trivalent Tp*U(CH₂Ph)₂(THF): Insertion vs Oxidation at Low-Valent Uranium–Carbon Bonds

The synthesis of a rare uranium­(III) bis­(benzyl), Tp*U­(CH₂Ph)₂(THF) (<b>2</b>), was achieved by salt metathesis of Tp*UI₂(THF)₂ with 2 equiv of KCH₂Ph at low temperature. This was characterized by ¹H NMR, infrared, and electronic absorption spectroscopy as well as X-ray crystallography. Addition of benzophenone to <b>2</b> forms the uranium­(IV) radical coupling product Tp*U­(CH₂Ph)₂(OC­(Ph)₂CH₂Ph) (<b>3</b>), whereas N₃Mes produces the imido derivative Tp*U­(NMes)­(CH₂Ph)­(THF) (<b>4</b>). Adding a further 1 equiv of N₃Mes to tetravalent <b>4</b> results in U–C insertion to form the U­(IV) triazenido species Tp*U­(NMes)­[(CH₂Ph)­N₃(Mes)-κ²<i>N</i>^1,2]­(THF) (<b>5</b>). Compound <b>2</b> also reacts with the redox-active 4,6-di-<i>tert</i>-butyl-2-[(2,6-diisopropylphenyl)­imino]­quinone (^DIPPiq) to form the oxidized amido­(phenolate) Tp*U­(CH₂Ph)­(^DIPPap) (<b>6</b>)

Use of Alkylsodium Reagents for the Synthesis of Trivalent Uranium Alkyl Complexes

A family of rare uranium­(III) alkyl complexes, Tp*₂UR (R = CH₂SiMe₃ (<b>3-CH</b>_<b>2</b><b>SiMe</b>_<b>3</b>), CH₃ (<b>4-CH</b>_<b>3</b>), (CH₂)₃CH₃ (<b>5-(CH</b>_<b>2</b><b>)</b>_<b>3</b><b>CH</b>_<b>3</b>); Tp* = hydrotris­(3,5-dimethylpyrazolyl)­borate), was synthesized by salt metathesis with alkylsodium reagents and Tp*₂UI (<b>2</b>). All compounds were fully characterized using ¹H NMR, infrared, and electronic absorption spectroscopies. Compounds <b>3-CH</b>_<b>2</b><b>SiMe</b>_<b>3</b> and <b>4-CH</b>_<b>3</b> were structurally characterized using X-ray crystallography and have U–C bond distances of 2.601(9) and 2.54(3) Å, respectively