Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes: The Role of Oxygen

Recently, it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photoexcitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), and analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes’ activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step, followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC toward the oxidation of TMB is very high and shows direct two-electron oxidation when the surface of the PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent, but only with appropriate drug delivery system

EPR, ENDOR, and Electronic Structure Studies of the Jahn–Teller Distortion in an Fe^V Nitride

The recently synthesized and isolated low-coordinate Fe^V nitride complex has numerous implications as a model for high-oxidation states in biological and industrial systems. The trigonal [PhB­(^<i>t</i>BuIm)₃Fe^VN]⁺ (where (PhB­(^<i>t</i>BuIm)₃^– = phenyltris­(3-<i>tert</i>-butylimidazol-2-ylidene)), (<b>1</b>) low-spin <i>d</i>³ (<i>S</i> = 1/2) coordination compound is subject to a Jahn–Teller (JT) distortion of its doubly degenerate ²E ground state. The electronic structure of this complex is analyzed by a combination of extended versions of the formal two-orbital pseudo Jahn–Teller (PJT) treatment and of quantum chemical computations of the PJT effect. The formal treatment is extended to incorporate mixing of the two <i>e</i> orbital doublets (30%) that results from a lowering of the idealized molecular symmetry from <i>D</i>_3<i>h</i> to <i>C</i>_3<i>v</i> through strong “doming” of the Fe–C₃ core. Correspondingly we introduce novel DFT/CASSCF computational methods in the computation of electronic structure, which reveal a quadratic JT distortion and significant <i>e</i>–<i>e</i> mixing, thus reaching a new level of synergism between computational and formal treatments. Hyperfine and quadrupole tensors are obtained by pulsed 35 GHz ENDOR measurements for the ^14/15N-nitride and the ¹¹B axial ligands, and spectra are obtained from the imidazole-2-ylidene ¹³C atoms that are not bound to Fe. Analysis of the nitride ENDOR tensors surprisingly reveals an essentially spherical nitride trianion bound to Fe, with negative spin density and minimal charge density anisotropy. The four-coordinate ¹¹B, as expected, exhibits negligible bonding to Fe. A detailed analysis of the frontier orbitals provided by the electronic structure calculations provides insight into the reactivity of <b>1</b>: JT-induced symmetry lowering provides an orbital selection mechanism for proton or H atom transfer reactivity

Flowchart summarizing method to measure craniad muscles cross-sectional areas.

<p>Flowchart summarizing method to measure craniad muscles cross-sectional areas.</p

Intra-class correlation coefficients for the second technique trialled in the feasibility study (Study 1).

<p>Intra-class correlation coefficients for the second technique trialled in the feasibility study (Study 1).</p

Plot of MR slice chosen as representing the mid-point of C2 for both raters.

<p>Plot of MR slice chosen as representing the mid-point of C2 for both raters.</p

Steric and Electronic Control of the Spin State in Three-Fold Symmetric, Four-Coordinate Iron(II) Complexes

The three-fold symmetric, four-coordinate iron­(II) phosphoraminimato complexes PhB­(MesIm)₃Fe–NPRR′R″ (PRR′R″ = PMePh₂, PMe₂Ph, PMe₃, and PⁿPr₃) undergo a thermally induced <i>S</i> = 0 to <i>S</i> = 2 spin-crossover in fluid solution. Smaller phosphoraminimato ligands stabilize the low-spin state, and an excellent correlation is observed between the characteristic temperature of the spin-crossover (<i>T</i>_1/2) and the Tolman cone angle (θ). Complexes with <i>para</i>-substituted triaryl phosphoraminimato ligands (<i>p</i>-XC₆H₄)₃PN^– (X = H, Me and OMe) also undergo spin-crossover in solution. These isosteric phosphoraminimato ligands reveal that the low-spin state is stabilized by more strongly donating ligands. This control over the spin state provides important insights for modulating the magnetic properties of four-coordinate iron­(II) complexes

Between scanner intra-class correlation coefficients for the repeatability study (Study 3).

<p>Between scanner intra-class correlation coefficients for the repeatability study (Study 3).</p

Bland-Altman plots for total neck muscle CSA and SCM+combined CSA measured by 2 raters.

<p>Bias of measurement between 2 different raters (mean of the ordinate) and limits of agreement (2sd) are represented by a solid and two dashed lines respectively. A. Bland-Altman plot for measurements of total neck muscle CSA by 2 different raters. B. Bland-Altman plot for measurements of SCM+combined CSA by 2 different raters.</p

Mean cross-sectional areas (CSAs) as measured by each rater summed for left and right, together with absolute mean difference and mean difference as percentage of CSA between raters (Study 2).

<p>Mean cross-sectional areas (CSAs) as measured by each rater summed for left and right, together with absolute mean difference and mean difference as percentage of CSA between raters (Study 2).</p

Intra-class correlation coefficients with 95% confidence intervals for the reliability study (Study 2).

<p>Intra-class correlation coefficients with 95% confidence intervals for the reliability study (Study 2).</p