Reaction pathways in the solid state and the Hubbard U correction.

We investigate how the Hubbard U correction influences vacancy defect migration barriers in transition metal oxide semiconductors. We show that, depending on the occupation of the transition metal d orbitals, the Hubbard U correction can cause severe instabilities in the migration barrier energies predicted using generalized gradient approximation density functional theory (GGA DFT). For the d0 oxide SrTiO3, applying a Hubbard correction to the Ti4+ 3d orbitals below 4-5 eV yields a migration barrier of ∼0.4 eV. However, above this threshold, the barrier increases suddenly to ∼2 eV. This sudden increase in the transition state barrier arises from the Hubbard U correction changing the Ti4+ t2g/eg orbital occupation, and hence electron density localization, along the migration pathway. Similar results are observed in the d10 oxide ZnO; however, significantly larger Hubbard U corrections must be applied to the Zn2+ 3d orbitals for the same instability to be observed. These results highlight important limitations to the application of the Hubbard U correction when modeling reactive pathways in solid state materials using GGA DFT.

The Hubbard-U correction and optical properties of d0 metal oxide photocatalysts.

We report a systematic investigation of individual and multisite Hubbard-U corrections for the electronic, structural, and optical properties of the metal titanate oxide d0 photocatalysts SrTiO3 and rutile/anatase TiO2. Accurate bandgaps for these materials can be reproduced with local density approximation and generalized gradient approximation exchange-correlation density functionals via a continuous series of empirically derived Ud and Up combinations, which are relatively insensitive to the choice of functional. On the other hand, lattice parameters are much more sensitive to the choice of Ud and Up, but in a systematic way that enables the Ud and Up corrections to be used to qualitatively gauge the extent of self-interaction error in the electron density. Modest Ud corrections (e.g., 4 eV-5 eV) yield the most reliable dielectric response functions for SrTiO3 and are comparable to the range of Ud values derived via linear response approaches. For r-TiO2 and a-TiO2, however, the Ud,p corrections that yield accurate bandgaps fail to accurately describe both the parallel and perpendicular components of the dielectric response function. Analysis of individual Ud and Up corrections on the optical properties of SrTiO3 suggests that the most consequential of the two individual corrections is Ud, as it predominately determines the accuracy of the dominant excitation from O-2p to the Ti-3d t2g/eg orbitals. Up, on the other hand, can be used to shift the entire optical response uniformly to higher frequencies. These results will assist high-throughput and machine learning approaches to screening photoactive materials based on d0 photocatalysts.

A multifactorial severity score for left congenital diaphragmatic hernia in a high-risk population using fetal magnetic resonance imaging.

BACKGROUND: Adverse outcomes for infants born with left congenital diaphragmatic hernia (CDH) have been correlated with fetal imaging findings. OBJECTIVE: We sought to corroborate these correlations in a high-risk cohort and describe a predictive mortality algorithm combining multiple imaging biomarkers for use in prenatal counseling. MATERIALS AND METHODS: We reviewed fetal MRI examinations at our institution from 2004 to 2016 demonstrating left-side CDH. MRI findings, hospital course and outcomes were recorded and analyzed using bivariate and multivariable analysis. We generated a receiver operating curve (ROC) to determine a cut-off relation for mortality. Finally, we created a predictive mortality calculator. RESULTS: Of 41 fetuses included in this high-risk cohort, 41% survived. Per bivariate analysis, observed-to-expected total fetal lung volume (P=0.007), intrathoracic position of the stomach (P=0.049), and extracorporeal membrane oxygenation (ECMO) requirement (P<0.001) were significantly associated with infant mortality. Youden J statistic optimized the ROC for mortality at 24% observed-to-expected total fetal lung volume (sensitivity 64%, specificity 82%, area under the curve 0.72). On multivariable analysis, observed-to-expected total fetal lung volume ± 24% was predictive of mortality (adjusted odds ratio, 95% confidence interval: 0.09 [0.02, 0.55]; P=0.008). We derived a novel mortality prediction calculator from this analysis. CONCLUSION: In this high-risk cohort, decreased observed-to-expected total fetal lung volume and stomach herniation were significantly associated with mortality. The novel predictive mortality calculator utilizes information from fetal MR imaging and provides prognostic information for health care providers. Creation of similar predictive tools by other institutions, using their distinct populations, might prove useful in family counseling, especially where there are discordant imaging findings.

Sensitised LnIII Emission and Excited-State Dynamics of Cofacial 'Pacman' Porphyrin Terpyridine Complexes.

An asymmetric 'Pacman' metalloligand, [Zn(PXT)], which features a cofacial ZnII -porphyrin unit (P) covalently attached to a terpyridine (T) chelating group via a rigid xanthene (X) moiety has been prepared, and its interactions with several different trivalent LnIII cations (NdIII , GdIII , YbIII and LuIII ) have been examined. The formation of 1:1 metal-ligand complexes was monitored by 1 H NMR spectroscopy and corroborated by HRMS data. Solution-stability constants were determined by UV/Vis titration, and the resulting complexes with NdIII or YbIII demonstrated sensitised emission in the NIR region due to energy transfer from the ZnII -porphyrin donor to LnIII acceptor. The energy transfer was investigated by transient absorption techniques, which provided insight into the kinetics and efficiency of the antenna effect.

Dehydration promotes phosphoramidate-linked amino acidyl and peptido adenosine conjugates.

Cyclic nucleoside phosphates have been shown previously to be adequately activated to oligomerise under dry conditions. Herein, it is demonstrated that 3',5'-cyclic adenosine monophosphate (3',5'-cAMP) and glycine when subjected to dehydration under alkaline conditions form phosphoramidate-linked conjugates. Solid-state reaction mechanisms investigated by DFT suggest why the reaction does not occur efficiently in the aqueous phase.

Dual Heterozygous Mutations in CYP21A2 and CYP11B1 in a Case of Nonclassic Congenital Adrenal Hyperplasia.

Background/Objective: Nonclassic congenital adrenal hyperplasia (NCCAH) may be overlooked or mistaken for polycystic ovarian syndrome. Unlike congenital adrenal hyperplasia (CAH), the enzymatic activities of 21-hydroxylase or 11ß-hydroxylase in NCCAH are not completely lost. In this case, NCCAH presented in a patient with CYP21A2 and CYP11B1 heterozygous mutations, one of which is a variant of unknown significance in CYP11B1. Case Report: A 30-year-old woman presented with a chief complaint of irregular menses and hirsutism. Previous medical history was significant for a prolactin level of 34.7 ng/mL (reference range, 2.0-23.0 ng/mL), a total serum testosterone level of 77 ng/dL (reference range, 25-125 ng/dL, not sex-specific), and a 2-mm × 3-mm pituitary lesion. An adrenocorticotrophic hormone stimulation test increased the 17-hydroxyprogesterone level from 444 ng/dL at baseline to 837 ng/dL at 60 minutes (baseline female reference range and stimulated reference ranges are 10-300 ng/dL and <1000 ng/dL, respectively). Gene sequencing revealed a heterozygous pathogenic CYP21A2 variant and a heterozygous, previously undescribed variant of unknown significance in CYP11B1. Discussion: Unlike CAH, NCCAH presents more subtly and later in life, and salt wasting and hypertension are not typically seen. Although mutations in CYP11B1 that cause steroid 11ß-hydroxylase deficiency more commonly lead to the CAH phenotype, cases have been reported of CYP11B1 mutations leading to NCCAH, depending on the location of the mutations. Conclusion: This patient's case demonstrates physical examination and laboratory findings suggestive of NCCAH. Our case adds to the database of described mutations in CYP11B1 and suggests that heterozygous mutations in 2 different genes may present phenotypically as NCCAH.

A three-dimensional cubic halogen-bonded network.

The rational, deliberate design of supramolecular architectures is of great importance for the discovery of complex materials. A three-dimensional cubic halogen-bonded network has been prepared by combination of an octahedral metal-containing halogen bond acceptor and a linear ditopic donor. This material displays α-Po pcu topology and is seven-fold interpenetrated. This is the first neutral, metal-containing three-dimensional halogen-bonded network to be reported.

Investigation of the identity of the nucleophile initiating the hydrolysis of phosphate esters catalyzed by dinuclear mimics of metallohydrolases.

di-Zinc(II) complexes of the ligands 2,6-bis((bis(2-methoxyethyl)amino)methyl)-4-methylphenol (HL1), 2,6-bis(bis(hydroxyethyl)aminomethyl)-4-methylphenol (HL2) and 2,6-bis((hydroxyethyl)(methoxyethyl)-aminomethyl)-4-methylphenol (HL3) have been prepared and characterized. The three ligands differ in their donor types, having ether donors (HL1), alkoxido donors (HL2) and both ether and alkoxido donors (HL3). These differences allowed an investigation into the role of the potential nucleophiles in the hydrolysis reaction with the phosphodiester substrate bis(2,4-dinitrophenyl)phosphate (BDNPP). In addition, the di-Mg(II) complex of ligand HL2 was prepared in order to examine the potential for Mg(II) to replace Zn(II) in these biomimetic systems. Kinetically relevant pKa values for the three di-Zn(II) complexes were determined to be 7.14 and 9.21 for [Zn2(L1)(CH3COO)2](PF6), 7.90 and 10.21 for [Zn2(L2)(CH3COO)2](BPh4) and 8.43 and 10.69 for [Zn2(L3)(CH3COO)2](BPh4). At the respective pH optima the relevant catalytic parameters are kcat=5.44(0.11)×10-5s-1 (Km=5.13(0.92) mM), 2.60(0.87)×10-4s-1 (Km=5.49(1.51) mM) and 1.53(0.27)×10-4s-1 (Km=2.14(0.50) mM) for [Zn2(L1)(CH3COO)2](PF6), [Zn2(L2)(CH3COO)2](BPh4) or [Zn2(L3)(CH3COO)2](BPh4), respectively. The di-Mg(II) complex was found to be unreactive in the hydrolysis reaction with BDNPP under the conditions employed. Computational methods using the [Zn2(L2)(CH3COO)2](BPh4) complex were used to discriminate between different possible mechanistic pathways. The DFT calculations indicate that an alkoxido-mediated pathway in the complexes formed with ligands L2 or L3 is unlikely, because it induces significant distortion of the Zn2(L) unit; a direct attack by a coordinated hydroxide is preferred in each of the three systems studied here. The calculations also revealed the important role of ligand structural rigidity.