Insight into the Reactivity and Electronic Structure of Dinuclear Dinitrosyl Iron Complexes

A combination of N/S/Fe K-edge X-ray absorption spectroscopy (XAS), X-ray diffraction data, and density functional theory (DFT) calculations provides an efficient way to unambiguously delineate the electronic structures and bonding characters of Fe–S, N–O, and Fe–N bonds among the direduced-form Roussin’s red ester (RRE) [Fe₂(μ-SPh)₂(NO)₄]^2–(<b>1</b>) with {Fe­(NO)₂}¹⁰-{Fe­(NO)₂}¹⁰ core, the reduced-form RRE [Fe₂(μ-SPh)₂(NO)₄]⁻(<b>3</b>) with {Fe­(NO)₂}⁹-{Fe­(NO)₂}¹⁰ core, and RRE [Fe₂(μ-SPh)₂(NO)₄] (<b>4</b>) with {Fe­(NO)₂}⁹-{Fe­(NO)₂}⁹ core. The major contributions of highest occupied molecular orbital (HOMO) 113α/β in complex <b>1</b> is related to the antibonding character between Fe­(d) and Fe­(d), Fe­(d), and S atoms, and bonding character between Fe­(d) and NO­(π*). The effective nuclear charge (<i><i>Z</i></i>_eff) of Fe site can be increased by removing electrons from HOMO to shorten the distances of Fe···Fe and Fe–S from <b>1</b> to <b>3</b> to <b>4</b> or, in contrast, to increase the Fe–N bond lengths from <b>1</b> to <b>3</b> to <b>4</b>. The higher IR ν_NO stretching frequencies (1761, 1720 cm^–1 (<b>4</b>), 1680, 1665 cm^–1 (<b>3</b>), and 1646, 1611, 1603 cm^–1 (<b>1</b>)) associated with the higher transition energy of N_1s →σ*­(NO) (412.6 eV (<b>4</b>), 412.3 eV (<b>3</b>), and 412.2 eV (<b>1</b>)) and the higher <i><i>Z</i></i>_eff of Fe derived from the transition energy of Fe_1s → Fe_3d (7113.8 eV (<b>4</b>), 7113.5 eV (<b>3</b>), and 7113.3 eV (<b>1</b>)) indicate that the N–O bond distances of these complexes are in the order of <b>1 > 3 > 4</b>. The N/S/Fe K-edge XAS spectra as well as DFT computations reveal the reduction of complex <b>4</b> yielding complex <b>3</b> occurs at Fe, S, and NO; in contrast, reduction mainly occurs at Fe site from complex <b>3</b> to complex <b>1</b>

Insight into the Reactivity and Electronic Structure of Dinuclear Dinitrosyl Iron Complexes

A combination of N/S/Fe K-edge X-ray absorption spectroscopy (XAS), X-ray diffraction data, and density functional theory (DFT) calculations provides an efficient way to unambiguously delineate the electronic structures and bonding characters of Fe–S, N–O, and Fe–N bonds among the direduced-form Roussin’s red ester (RRE) [Fe₂(μ-SPh)₂(NO)₄]^2–(<b>1</b>) with {Fe­(NO)₂}¹⁰-{Fe­(NO)₂}¹⁰ core, the reduced-form RRE [Fe₂(μ-SPh)₂(NO)₄]⁻(<b>3</b>) with {Fe­(NO)₂}⁹-{Fe­(NO)₂}¹⁰ core, and RRE [Fe₂(μ-SPh)₂(NO)₄] (<b>4</b>) with {Fe­(NO)₂}⁹-{Fe­(NO)₂}⁹ core. The major contributions of highest occupied molecular orbital (HOMO) 113α/β in complex <b>1</b> is related to the antibonding character between Fe­(d) and Fe­(d), Fe­(d), and S atoms, and bonding character between Fe­(d) and NO­(π*). The effective nuclear charge (<i><i>Z</i></i>_eff) of Fe site can be increased by removing electrons from HOMO to shorten the distances of Fe···Fe and Fe–S from <b>1</b> to <b>3</b> to <b>4</b> or, in contrast, to increase the Fe–N bond lengths from <b>1</b> to <b>3</b> to <b>4</b>. The higher IR ν_NO stretching frequencies (1761, 1720 cm^–1 (<b>4</b>), 1680, 1665 cm^–1 (<b>3</b>), and 1646, 1611, 1603 cm^–1 (<b>1</b>)) associated with the higher transition energy of N_1s →σ*­(NO) (412.6 eV (<b>4</b>), 412.3 eV (<b>3</b>), and 412.2 eV (<b>1</b>)) and the higher <i><i>Z</i></i>_eff of Fe derived from the transition energy of Fe_1s → Fe_3d (7113.8 eV (<b>4</b>), 7113.5 eV (<b>3</b>), and 7113.3 eV (<b>1</b>)) indicate that the N–O bond distances of these complexes are in the order of <b>1 > 3 > 4</b>. The N/S/Fe K-edge XAS spectra as well as DFT computations reveal the reduction of complex <b>4</b> yielding complex <b>3</b> occurs at Fe, S, and NO; in contrast, reduction mainly occurs at Fe site from complex <b>3</b> to complex <b>1</b>

Bond Characterization of a Unique Thiathiophthene Derivative: Combined Charge Density Study and X‑ray Absorption Spectroscopy

Thiathiophthene (TTP), a planar molecule with two fused heterocyclic five-membered rings and an essentially linear S–S–S bond, is a molecule of great interest due to its unique chemical bondings. To elucidate the remarkable bonding nature, a combined experimental and theoretical study on the electron density distribution of 2,5-dimethyl-3,4-trimethylene-6a-TTP (<b>1</b>) is investigated based on a multipole model through high-resolution X-ray diffraction data experimentally and on the density functional calculations (DFT) theoretically. In addition, S K-edge X-ray absorption spectroscopy (XAS) is measured to verify the chemical bonding concerning the sulfur atoms. The molecule can be firmly described as 10π electron with aromatic character among the eight atoms, S₃C₅, of the two fused five-membered rings plus three-center four-electron σ character along the S–S–S bond. Such bonding description is verified with the calculated XAS spectrum, where the pre-edge absorption for transitions from S 1s to π* and σ* are located. The three-center four-electron S–S–S σ bond makes the terminal S atoms richer in electron density than the central one

Bond Characterization of a Unique Thiathiophthene Derivative: Combined Charge Density Study and X‑ray Absorption Spectroscopy

Thiathiophthene (TTP), a planar molecule with two fused heterocyclic five-membered rings and an essentially linear S–S–S bond, is a molecule of great interest due to its unique chemical bondings. To elucidate the remarkable bonding nature, a combined experimental and theoretical study on the electron density distribution of 2,5-dimethyl-3,4-trimethylene-6a-TTP (<b>1</b>) is investigated based on a multipole model through high-resolution X-ray diffraction data experimentally and on the density functional calculations (DFT) theoretically. In addition, S K-edge X-ray absorption spectroscopy (XAS) is measured to verify the chemical bonding concerning the sulfur atoms. The molecule can be firmly described as 10π electron with aromatic character among the eight atoms, S₃C₅, of the two fused five-membered rings plus three-center four-electron σ character along the S–S–S bond. Such bonding description is verified with the calculated XAS spectrum, where the pre-edge absorption for transitions from S 1s to π* and σ* are located. The three-center four-electron S–S–S σ bond makes the terminal S atoms richer in electron density than the central one

Bond Characterization of a Unique Thiathiophthene Derivative: Combined Charge Density Study and X‑ray Absorption Spectroscopy

Thiathiophthene (TTP), a planar molecule with two fused heterocyclic five-membered rings and an essentially linear S–S–S bond, is a molecule of great interest due to its unique chemical bondings. To elucidate the remarkable bonding nature, a combined experimental and theoretical study on the electron density distribution of 2,5-dimethyl-3,4-trimethylene-6a-TTP (<b>1</b>) is investigated based on a multipole model through high-resolution X-ray diffraction data experimentally and on the density functional calculations (DFT) theoretically. In addition, S K-edge X-ray absorption spectroscopy (XAS) is measured to verify the chemical bonding concerning the sulfur atoms. The molecule can be firmly described as 10π electron with aromatic character among the eight atoms, S₃C₅, of the two fused five-membered rings plus three-center four-electron σ character along the S–S–S bond. Such bonding description is verified with the calculated XAS spectrum, where the pre-edge absorption for transitions from S 1s to π* and σ* are located. The three-center four-electron S–S–S σ bond makes the terminal S atoms richer in electron density than the central one

MiR-145 mediates zebrafish hepatic outgrowth through progranulin A signaling

<div><p>MicroRNAs (miRs) are mRNA-regulatory molecules that fine-tune gene expression and modulate both processes of development and tumorigenesis. Our previous studies identified progranulin A (GrnA) as a growth factor which induces zebrafish hepatic outgrowth through MET signaling. We also found that miR-145 is one of potential fine-tuning regulators of GrnA involved in embryonic hepatic outgrowth. The low level of miR-145 seen in hepatocarinogenesis has been shown to promote pathological liver growth. However, little is known about the regulatory mechanism of miR-145 in embryonic liver development. In this study, we demonstrate a significant decrease in miR-145 expression during hepatogenesis. We modulate miR-145 expression in zebrafish embryos by injection with a miR-145 mimic or a miR-145 hairpin inhibitor. Altered embryonic liver outgrowth is observed in response to miR-145 expression modulation. We also confirm a critical role of miR-145 in hepatic outgrowth by using whole-mount in situ hybridization. Loss of miR-145 expression in embryos results in hepatic cell proliferation, and vice versa. Furthermore, we demonstrate that GrnA is a target of miR-145 and GrnA-induced MET signaling is also regulated by miR-145 as determined by luciferase reporter assay and gene expression analysis, respectively. In addition, co-injection of GrnA mRNA with miR-145 mimic or MO-GrnA with miR-145 inhibitor restores the liver defects caused by dysregulation of miR-145 expression. In conclusion, our findings suggest an important role of miR-145 in regulating GrnA-dependent hepatic outgrowth in zebrafish embryonic development.</p></div

GrnA rescues the hepatic outgrowth defect caused by miR-145 manipulation.

<p>Liver morphology was determined by EGFP expression at 4 dpf in <i>Tg (fabp10</i>:<i>EGFP)</i> embryos (A) or in embryos injected with control mimic (B), miR-145 inhibitor (C), miR-145 mimic (D), miR-145 inhibitor with <i>grnA</i> MO (0.25 ng/embryo) (E) and miR-145 mimic with <i>grnA</i> mRNA (0.4 ng/embryo) (F). Thirty embryos per experimental group were used and three independent replicates were performed. A 3D image of the liver was observed using Leica SP5 confocal microscope and Imaris software. The liver size was examined by measuring the volume of EGFP expression (G). Ten embryos per experimental group were used and three independent replicates were performed. Scale bars, 100 μm; EGFP, enhanced green fluorescent protein; *P < 0.05, t-test.</p

miR-145 and GrnA expression patterns are inversely correlated during liver development.

<p>(A,B) The expression patterns of miR-145 (A), <i>grnA</i> (B) and the hepatoblast-specific marker gene <i>prox1</i> at 30, 50, 72 and 96 hpf were examined using FISH in wild-type zebrafish embryos. Scale bars, 25 μm (at 30 and 50 hpf), 50 μm (at 72 and 96 hpf). The dotted circles indicate <i>prox1</i> positive cells that represent liver. Ten embryos per experimental group were used and three independent replicates were performed. (C) The fetal liver at 72 and 96 hpf were isolated to quantify liver specific expression patterns of miR-145 and <i>GrnA</i>. Fifteen fetal livers per experiment were used and three independent replicates were performed. The relative expression is normalized with internal control, U6 and <i>ef1a</i> expression.</p

miR-145 directly targets grnA as determined by luciferase assay.

<p>The predicted miR-145 target site on GrnA CDS is illustrated. WT and mutant forms of <i>GrnA</i> CDS were constructed in <i>psi-check2</i> reporter vector (A). miR-145 mimic and <i>psi</i>-grna-WT/<i>psi</i>-grna-mutant vector were co-transfected into ZFL cells for the luciferase assay. The luciferase activity of <i>psi</i>-grna-WT was suppressed approximately 45% in response to miR-145 mimic treatment. In contrast, the luciferase activity of <i>psi</i>-grna-mutant was unchanged in response to miR-145 mimic treatment (*P < 0.05, t-test) (B). Three independent replicates were performed.</p

miR-145 regulates GrnA and MET gene expression.

<p>The expression levels of the <i>grnA</i> and <i>met</i> genes were examined using qPCR after 24 hours of control, miR-145 mimic and miR-145 inhibitor treatment in ZFL cells (A). The protein levels of GrnA, MET and GAPDH were examined by Western blotting in ZFL cells at 48 hours after control, miR-145 mimic and miR-145 inhibitor treatments. The relative GrnA, MET and GAPDH protein levels were quantified as shown in the low panel (*P < 0.05, t-test) (B). Three independent replicates were performed.</p