Towards tailoring hydrophobic interaction with uranyl(VI) oxygen for C-H activation.

Bovine serum albumin (BSA) has a uranyl(VI) binding hotspot where uranium is tightly bound by three carboxylates. Uranyl oxygen is "soaked" into the hydrophobic core of BSA. Isopropyl hydrogen of Val is trapped near UO22+ and upon photoexcitation, C-H bond cleavage is initiated. A unique hydrophobic contact with "yl"-oxygen, as observed here, can be used to induce C-H activation.

Preliminary studies of XANES and DFT calculation of Ru extraction by imino-diacetamide and related compounds.

We connected three research fields on Ru extraction, XANES, and DFT calculation and elucidate the sequence of distribution ratio (D) and their reactions. The magnitude order of the distribution ratio, D(Ru), from acids, HCl > H2SO4 > HNO3 > HClO4, by IDOA indicates to extract readily the stable Ru-Cl ions. The XANES signals, which suggests the electrical charge of Ru(III) extracted into the organic phase, supports the ion-pairing extraction of the anionic Ru-Cl complex with an extractant protonated. Ru(III) in other acids might be extracted by solvation of extractant, thus ion-pair extraction is stronger than solvation in Ru extraction. According to the D(Ru), the same extractant trend, NTAamide > MIDOA > IDOA, as the energy gap of HOMO and LUMO by DFT calculation is found, which suggests that DFT calculation can give the relative magnitude of each D(M) value when extractant and metal in an extraction are determined.

Extraction of Rh(III) from hydrochloric acid by protonated NTAamide(C6) and analogous compounds and understanding of extraction equilibria by using UV spectroscopy and DFT calculations.

Extraction of Rh from hydrochloric acid is conducted using NTAamide(C6) (N,N,N´,N´,N´´,N´´-hexahexyl-nitrilotriacetamide) and other related compounds. We use the ion-pair extraction of anionic species of Rh-chloride and protonated extractant. Rh ions exist as Rh(Cl)n(H2O)6-n (n ≤ 5) and the tertiary nitrogen atom in an extractant are protonated to produce a quaternary amine in acidic condition. The D(Rh) values are changeable because the Rh-Cl-H2O complex forms from + 3 to - 2 valency. Rh-chloride ion with a peak of spectrum at 504 nm can be extracted effectively, where RhCl4(H2O)- and RhCl5(H2O)2- exist from Density functional theory calculation and UV spectrum. The maximum distribution ratio (D) of Rh(III) is 16, and 85 mM Rh can be extracted from 1 M HCl dissolving 96 mM, due to less third phase formation. Approximate 80% of Rh can be stripped by the water-soluble reagents having the activities of neutralization and solvation. The figure for the Graphical Index saved in the JPEG, PNG or TIFF format at 300 dpi should be pasted with the size adjusted to the frame below (5 cm long and 8 cm wide).

Conformation, hydration, and ligand exchange process of ruthenium nitrosyl complexes in aqueous solution: Free-energy calculations by a combination of molecular-orbital theories and different solvent models.

Distribution of solvent molecules near transition-metal complex is key information to comprehend the functionality, reactivity, and so forth. However, polarizable continuum solvent models still are the standard and conventional partner of molecular-orbital (MO) calculations in the solution system including transition-metal complex. In this study, we investigate the conformation, hydration, and ligand substitution reaction between NO2 - and H2 O in aqueous solution for [Ru(NO)(OH)(NO2 )4 ]2- (A), [Ru(NO)(OH)(NO2 )3 (ONO)]2- (B), and [Ru(NO)(OH)(NO2 )3 (H2 O)]- (C) using a combination method of MO theories and a state-of-the-art molecular solvation technique (NI-MC-MOZ-SCF). A dominant species is found in the complex B conformers and, as expected, different between the solvent models, which reveals that molecular solvation beyond continuum media treatment are required for a reliable description of solvation near transition-metal complex. In the stability constant evaluation of ligand substitution reaction, an assumption that considers the direct association between the dissociated NO2 - and complex C is useful to obtain a reliable stability constant.

Fully Chelating N3O2-Pentadentate Planar Ligands Designed for the Strongest and Selective Capture of Uranium from Seawater.

Based on the unique fivefold equatorial coordination of UO22+, water-compatible pentadentate planar ligands, H2saldian and its derivatives, were designed for the strong and selective capture of UO22+ in seawater. In the simulated seawater condition (0.5 M NaCl + 2.3 mM HCO3-/CO32-, pH 8), saldian2- shows the strongest complexation with UO22+ to form UO2(saldian) (log ß11 = 28.05 ± 0.07), which is more than 10 order of magnitude greater than amidoxime-based or -inspired ligand systems most commonly employed for U capture from seawater. Good selectivity for UO22+ from other metal ions coexisting in seawater was also demonstrated.

Density Functional Theory Study on the 193Ir Mössbauer Spectroscopic Parameters of Vaska's Complexes and Their Oxidative Adducts.

In the present study, density functional theory (DFT) calculation was applied to Vaska's complexes of formula trans-[IrIX(CO)(PPh3)2] and their oxidative adducts with small molecules (YZ) including H2, i.e., trans-[IrIIIClYZ(CO)(PPh3)2], to successfully correlate the electronic states of the complexes with the corresponding 193Ir Mössbauer spectroscopic parameters. After confirming the reproducibility of the DFT methods for elucidating the equilibrium structures and 193Ir Mössbauer isomer shifts of the octahedral Ir complexes, the isomer shifts and quadrupole splitting values of Vaska's complexes and their oxidative adducts were calculated. A bond critical point analysis revealed that the tendency in the isomer shifts was correlated with the strength of the covalent interaction in the coordination bonds. In an electric field gradient (EFG) analysis of the oxidative adducts, the sign of the principal axis was found to be positive for the complex with YZ = Cl2 and negative for the complex with YZ = H2. This reversal of the sign of the EFG principal axis was caused by the difference in the electron density distribution for the coordination bonds between Ir and YZ, according to a density of states analysis.

Effect of Oxygen-Donor Charge on Adjacent Nitrogen-Donor Interactions in Eu3+ Complexes of Mixed N,O-Donor Ligands Demonstrated on a 10-Fold [Eu(TPAMEN)]3+ Chelate Complex.

To reduce high-level radiotoxic waste generated by nuclear power plants, highly selective separation agents for minor actinides are mandatory. The mixed N,O-donor ligand N,N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H4TPAEN; 1) has shown good performance as a masking agent in Am3+/Eu3+ separation studies. Adjustments on the pyridyl backbone to raise the hydrophilicity led to a decrease in selectivity and a decrease in M3+-Nam interactions. An enhanced basicity of the pyridyl N-donors was given as a cause. In this work, we examine whether a decrease in O-donor basicity can promote the M3+-Nam interactions. Therefore, we replace the deprotonated "charged" carboxylic acid groups of TPAEN4- by neutral amide groups and introduce N,N,N',N'-tetrakis[(6-N″,N''-diethylcarbamoylpyridin-2-yl)methyl]ethylenediamine (TPAMEN; 2) as a new ligand. TPAMEN was crystallized with Eu(OTf)3 and Eu(NO3)3·6H2O to form positively charged 1:1 [Eu(TPAMEN)]3+ complexes in the solid state. Alterations in the M-O/N bond distances are compared to [Eu(TPAEN)]- and investigated by DFT calculations to expose the differences in charge/energy density distributions at europium(III) and the donor functionalities of the TPAEN4- and TPAMEN. On the basis of estimations of the bond orders, atomic charges spin populations, and density of states in the Eu and potential Am and Cm complexes, the specific contributions of the donor-metal interaction are analyzed. The prediction of complex formation energy differences for the [M(TPAEN)]- and [M(TPAMEN)]3+ (M3+ = Eu3+, Am3+) complexes provide an outlook on the potential performance of TPAMEN in Am3+/Eu3+ separation.

The ER-associated protease Ste24 prevents N-terminal signal peptide-independent translocation into the endoplasmic reticulum in Saccharomyces cerevisiae.

Soluble proteins destined for the secretory pathway contain an N-terminal signal peptide that induces their translocation into the endoplasmic reticulum (ER). The importance of N-terminal signal peptides for ER translocation has been extensively examined over the past few decades. However, in the budding yeast Saccharomyces cerevisiae, a few proteins devoid of a signal peptide are still translocated into the ER and then N-glycosyl-ated. Using signal peptide-truncated reporter proteins, here we report the detection of significant translocation of N-terminal signal peptide-truncated proteins in a yeast mutant strain (ste24Δ) that lacks the endopeptidase Ste24 at the ER membrane. Furthermore, several ER/cytosolic proteins, including Sec61, Sec66, and Sec72, were identified as being involved in the translocation process. On the basis of screening for 20 soluble proteins that may be N-glycosylated in the ER in the ste24Δ strain, we identified the transcription factor Rme1 as a protein that is partially N-glycosylated despite the lack of a signal peptide. These results clearly indicate that some proteins lacking a signal peptide can be translocated into the ER and that Ste24 typically suppresses this process.

Complexation and bonding studies on [Ru(NO)(H2O)5]3+ with nitrate ions by using density functional theory calculation.

Complexation reactions of ruthenium-nitrosyl complexes in HNO3 solution were investigated by density functional theory (DFT) calculations in order to predict the stability of Ru species in high-level radioactive liquid waste (HLLW) solution. The equilibrium structure of [Ru(NO)(NO3)3(H2O)2] obtained by DFT calculations reproduced the experimental Ru-ligand bond lengths and IR frequencies reported previously. Comparison of the Gibbs energies among the geometrical isomers for [Ru(NO)(NO3) x (H2O)5-x ](3-x)+/- revealed that the complexation reactions of the ruthenium-nitrosyl complexes with NO3 - proceed via the NO3 - coordination to the equatorial plane toward the Ru-NO axis. We also estimated Gibbs energy differences on the stepwise complexation reactions to succeed in reproducing the fraction of Ru-NO species in 6 M HNO3 solution, such as in HLLW, by considering the association energy between the Ru-NO species and the substituting ligands. Electron density analyses of the complexes indicated that the strength of the Ru-ligand coordination bonds depends on the stability of the Ru species and the Ru complex without NO3 - at the axial position is more stable than that with NO3 -, which might be attributed to the difference in the trans influence between H2O and NO3 -. Finally, we demonstrated the complexation kinetics in the reactions x = 1 → x = 2. The present study is expected to enable us to model the precise complexation reactions of platinum-group metals in HNO3 solution.

Density Functional Theory (DFT)-Based Bonding Analysis Correlates Ligand Field Strength with 99Ru Mössbauer Parameters of Ruthenium-Nitrosyl Complexes.

We applied density functional theory calculations to ruthenium-nitrosyl complexes, which are known to exist in high-level radioactive waste generating during reprocessing of spent nuclear fuel, to give a theoretical correlation between 99Ru Mössbauer spectroscopic parameters and ligand field strength for the first time. The structures of the series of complexes, [Ru(NO)L5] (L = Br-, Cl-, NH3, CN-), were modeled based on the corresponding single-crystal X-ray coordinates. The comparisons of the geometries and total energies between the different spin states suggested that the singlet spin state of [Ru(II)(NO+)L5] complexes were the most stable. This result was supported by the benchmark calculations of the 99Ru Mössbauer isomer shift (δ) and quadrupole splitting (ΔEQ) values. The calculated results of both the δ and ΔEQ values reproduced the experimental results by reported previously and increased in the order of L = Br-, Cl-, NH3, CN-. Finally, we estimated the ligand field strength (Δo) based on molecular orbitals, assuming C4v symmetry and showed the increase of Δo values in that order, being consistent with well-known spectrochemical series of ligands. The increase attributes to the strengthening of the abilities of σ-donor and π-acceptor of the L-ligands to the Ru atom, resulting in the increase of the δ values. Furthermore, the increase of the σ-type donation into Ru dx2-y2 orbital and the π-type back-donation from Ru dxz, dyz orbitals in that order caused the decrease of the electron density along the Ru-NO axis, resulting in the increase of the ΔEQ values. This study is expected to contribute to the ligand design for the ruthenium-nitrosyl complexes, leading to the drug design for NO carrier and the decontamination of radioactive ruthenium from the ecological system, as well as the recovery of platinum-group metals from high-level radioactive waste.

Theoretical Elucidation of Am(III)/Cm(III) Separation Mechanism with Diamide-type Ligands Using Relativistic Density Functional Theory Calculation.

We elucidated the separation mechanism between Am(III) and Cm(III) ions by using two different types of diamide ligands, diglycolamide (DGA) and alkylated diamide amine (ADAAM), by means of the density functional theory technique and electron density analysis. The molecular geometries and formation reactions of the metal-ligand complexes were modeled by using [M(DGA)3]3+ and [M(ADAAM)(NO3)3(H2O)]. We successfully reproduced Cm(III) selectivity over Am(III) with DGA and Am(III) selectivity over Cm(III) with ADAAM. Furthermore, we analyzed the bonding properties between the metal ion and the diamide-type ligands by using model complexes, [M(DGA)3]3+ and [M(ADAAM)(NO3)3(H2O)], and revealed the differences in terms of the bond dissociation energy and the metal 5f orbital participation in the covalency between the Am(III) and the Cm(III) complexes. It was suggested that the differences were key factors to understand the Am(III)/Cm(III) selectivity.

Computational chemical analysis of Eu(iii) and Am(iii) complexes with pnictogen-donor ligands using DFT calculations.

We demonstrated density functional calculations of Eu(iii) and Am(iii) complexes with pnictogen-donor (X) ligands, (CH3)2X-CH2-CH2-X(CH3)2 (X = N, P, As and Sb). We investigated the optimized structures of the complexes and the Gibbs energy differences in the complex formation reactions. The results indicated that the N- and P-donor ligands exhibit Am(iii) ion selectivity over Eu(iii) ions; especially, the P-donor ligand showed the highest selectivity. The tendency of the Am(iii)/Eu(iii) selectivity by the pnictogen-donor ligands was found to be comparable to that of the soft acid classification in the hard and soft acids and bases rule. Mulliken's spin population analysis indicated that the bonding properties between the metal ion and the pnictogen atoms correlated with the Am(iii)/Eu(iii) selectivity. In particular, the participation of f-orbital electrons of the metal ion in the covalency was indicated to play an important role in the selectivity.

UV and IR Spectroscopy of Cryogenically Cooled, Lanthanide-Containing Ions in the Gas Phase.

We measure UV and IR spectra in the gas phase for EuOH+, EuCl+, and TbO+ ions, which are produced by an electrospray ionization source and cooled to ∼10 K in a cold, 22-pole ion trap. The UV photodissociation (UVPD) spectra of these ions show a number of sharp, well-resolved bands in the 30000-38000 cm-1 region, although a definite assignment of the spectra is difficult because of a high degree of congestion. We also measure an IR spectrum of the EuOH+ ion in the 3500-3800 cm-1 region by IR-UV double-resonance spectroscopy, which reveals an OH stretching band at 3732 cm-1. We perform density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations of these ions in order to examine the nature of the transitions. The DFT results indicate that the states of highest-spin multiplicity (octet for EuOH+ and EuCl+ and septet for TbO+) are substantially more stable than other states of lower-spin multiplicity. The TD-DFT calculations suggest that UV absorption of the EuOH+ and EuCl+ ions arises from Eu(4f) → Eu(5d,6p) transitions, whereas electronic transitions of the TbO+ ion are mainly due to the electron promotion of O(2p) → Tb(4f,6s). The UVPD results of the lanthanide-containing ions in this study suggest the possibility of using lanthanide ions as "conformation reporters" for gas-phase spectroscopy for large molecules.

The separation mechanism of Am(iii) from Eu(iii) by diglycolamide and nitrilotriacetamide extraction reagents using DFT calculations.

Relativistic density functional calculations were applied to study the separation behaviors of the Am(iii) ion from the Eu(iii) ion by diglycolamide (DGA) and nitrilotriacetamide (NTA) ligands in order to understand the difference in the separation mechanism of their reagents. The complexation reaction was modeled on the basis of previous experimental studies. The calculated energies based on stabilization by complex formation at the ZORA-B2PLYP/SARC level predicted that the DGA reagent preferably coordinated to the Eu(iii) ion when compared with the Am(iii) ion. In contrast, the NTA reagent selectively coordinated to the Am(iii) ion when compared with the Eu(iii) ion. These results reproduced the experimental selectivity of DGA and NTA ligands toward Eu(iii) and Am(iii) ions. Mulliken's population analyses implied that the difference in the contribution of the bonding property between the f-orbital of Am and donor atoms determined the comparative stability of Eu and Am complexes.

Bonding Study on the Chemical Separation of Am(III) from Eu(III) by S-, N-, and O-Donor Ligands by Means of All-Electron ZORA-DFT Calculation.

We performed a theoretical investigation for the selectivity of Eu(III)/Am(III) ions depending on the donor atoms by means of all-electron ZORA-DFT calculation. We estimated their selectivity as the relative stability in the complex formation reaction. The B2PLYP functional reproduced the experimental selectivity in which S- and N-donor ligands favor Am(III) ion, but O-donor ligand favors Eu(III) ion. Mulliken's bond overlap population analysis revealed that the contribution of the f orbital to the bonding was small or zero for Eu complex, whereas it was large for Am complex. The bonding nature of the f orbital for Am ion was the bonding type to S- and N-donor ligands, while it was the antibonding type to O-donor ligand. It was suggested that the difference in the bonding nature between the f orbital in the metal and the donor atoms determines the selectivity of Eu(III)/Am(III) by donor ligands.

Benchmark study of the Mössbauer isomer shifts of Eu and Np complexes by relativistic DFT calculations for understanding the bonding nature of f-block compounds.

We have performed benchmark investigations into the bonding properties in lanthanide and actinide complexes to quantitatively estimate the covalency of f-block compounds. Three different density functionals including BP86 (pure-GGA), B3LYP (hybrid-GGA) and B2PLYP (double hybrid-GGA) were employed for all-electron self-consistent field calculations compensated by the scalar-relativistic zero-order regular approximation (ZORA) Hamiltonian with a relativistically contracted all-electron basis set. Ten Eu and ten Np complexes were employed as benchmark sets for the calculation of Mössbauer parameters for (151)Eu and (237)Np compounds. As a result of the linear fitting between the calculated electron densities at the nucleus (ρ) and the experimental isomer shifts (δ(exp)), the calculations performed using the all-electron ZORA-B2PLYP level reproduced a change of electron density at the Mössbauer nucleus for both Eu and Np complexes with high correlation coefficients (R(2) > 0.90). Mulliken's population analyses indicated that the BP86 and B3LYP methods overestimated the covalency of both Eu and Np complexes due to the smaller amount of the exact Hartree-Fock exchange admixture included in BP86 and B3PLYP compared to that in the B2PLYP functional. By comparing Mulliken's electronic structure analyses with the experimental isomer shifts, we found that Mulliken's spin population values were good parameters to quantitatively estimate the bonding natures of Eu and Np complexes.

[A CR case of colorectal cancer given 39 courses of FOLFOX].

We report a CR case of advanced rectal cancer successfully treated with 39 courses of mFOLFOX6. The patient was a 29-year-old female with Stage IV rectal cancer. At first she was given IFL together with radiotherapy. It took effect for three months, and the therapeutic effect was PR, but interstitial pneumonia developed. Therefore, we shifted to mFOLFOX6, and she was treated with 39 courses. Grade 1 appeared several times for peripheral neuropathy, but recovered immediately. If we could control peripheral neuropathy with FOLFOX, it was thought that long-term survival could / be expected.

Promotion of carcinogenesis and oxidative stress by dietary cholesterol in rat prostate.

The association between prostate cancer risk and dietary fat consumption is well documented and explained partly by accelerated lipid peroxidation. We explored the possible effects of high dietary cholesterol on carcinogenesis and oxidative stress in the prostate of ACI/Seg rats. The rats develop prostate cancer spontaneously late in the life, providing an appropriate model to explore prolonged dietary conditions. Two groups of 20-week-old male rats, 28 each, were fed either a basal diet or a basal diet supplemented with 1% cholesterol (high cholesterol diet), and killed at 100 weeks of age. Rats on the high cholesterol diet developed adenocarcinoma in the ventral prostate more frequently (26 versus 4%, P = 0.023). In the repeat study, 26 rats each were treated similarly and killed at 80 weeks for histology and oxidative stress assay. Oxidative stress was assessed by measuring the plasma and intra-prostatic levels of vitamin E, vitamin C, uric acid and the oxidized and reduced forms of coenzyme Q(9). The relative amount of oxidized form of coenzyme Q(9) is a sensitive marker of oxidative stress. Rats on the high cholesterol diet demonstrated a higher incidence of atypical prostatic hyperplasia (24 versus 4%, P = 0.049). Also, the prostate showed a 2-fold increase (203% of the control) in the relative amounts of the oxidized form of coenzyme Q(9) and reciprocal reduction of vitamin C (9.5% of the control) and uric acid (46% of the control) levels (P < 0.01), with a minimal change in vitamin E. The plasma levels of these compounds were not affected by dietary conditions. These results indicated that long-term feeding of a 1% cholesterol diet promoted carcinogenesis and tissue oxidative stress in rat prostate. The role of dietary fat and oxidative stress in prostate carcinogenesis needs further investigation.