Pulse electron paramagnetic resonance studies of the interaction of methanol with the S2 state of the Mn4O5Ca cluster of photosystem II.

The binding of the substrate analogue methanol to the catalytic Mn4CaO5 cluster of the water-oxidizing enzyme photosystem II is known to alter the electronic structure properties of the oxygen-evolving complex without retarding O2-evolution under steady-state illumination conditions. We report the binding mode of (13)C-labeled methanol determined using 9.4 GHz (X-band) hyperfine sublevel-correlation (HYSCORE) and 34 GHz (Q-band) electron spin-echo electron nuclear double resonance (ESE-ENDOR) spectroscopies.

Vitamin D attenuates cytokine-induced remodeling in human fetal airway smooth muscle cells.

Asthma in the pediatric population remains a significant contributor to morbidity and increasing healthcare costs. Vitamin D3 insufficiency and deficiency have been associated with development of asthma. Recent studies in models of adult airway diseases suggest that the bioactive Vitamin D3 metabolite, calcitriol (1,25-dihydroxyvitamin D3 ; 1,25(OH)2 D3 ), modulates responses to inflammation; however, this concept has not been explored in developing airways in the context of pediatric asthma.

Procalcitonin elevation suggests a septic source.

Procalcitonin is used as a marker for sepsis but there is little known about the correlation of the procalcitonin elevation with the causative organism in sepsis. All patients aged 18 to 80 years who were admitted to the surgery service from June 2010 to May 2012 and who had a procalcitonin drawn were evaluated. Culture data were reviewed to determine the causative organism.

The cyanide ligands of [FeFe] hydrogenase: pulse EPR studies of (13)C and (15)N-labeled H-cluster.

The two cyanide ligands in the assembled cluster of [FeFe] hydrogenase originate from exogenous l-tyrosine. Using selectively labeled tyrosine substrates, the cyanides were isotopically labeled via a recently developed in vitro maturation procedure allowing advanced electron paramagnetic resonance techniques to probe the electronic structure of the catalytic core of the enzyme. The ratio of the isotropic (13)C hyperfine interactions for the two CN(-) ligands-a reporter of spin density on their respective coordinating iron ions-collapses from ≈5.

Withdrawal of care in a trauma intensive care unit: the impact on mortality rate.

Withdrawal of care has increased in recent years as the population older than 65 years of age has increased. We sought to investigate the impact of this decision on our mortality rate. We retrospectively reviewed a prospectively collected database to determine the percentage of cases in which care was actively withdrawn.

Interaction of iron deficiency anemia and hemoglobinopathies among college students and pregnant women: a multi center evaluation in India.

Although iron deficiency anemia is very common in India, systematic large studies on the prevalence and hematological consequences of iron deficiency among carriers of β-thalassemia (β-thal) and other hemoglobinopathies are lacking. A multi center project was undertaken to screen college/university students and pregnant women for iron deficiency anemia and various hemoglobinopathies. Fifty-six thousand, seven hundred and seventy-two subjects from six states, Maharashtra, Gujarat, Karnataka, West Bengal, Assam and Punjab, were studied.

Paramagnetic intermediates generated by radical S-adenosylmethionine (SAM) enzymes.

A [4Fe-4S](+) cluster reduces a bound S-adenosylmethionine (SAM) molecule, cleaving it into methionine and a 5'-deoxyadenosyl radical (5'-dA(•)). This step initiates the varied chemistry catalyzed by each of the so-called radical SAM enzymes. The strongly oxidizing 5'-dA(•) is quenched by abstracting a H-atom from a target species.

The HydG enzyme generates an Fe(CO)2(CN) synthon in assembly of the FeFe hydrogenase H-cluster.

Three iron-sulfur proteins--HydE, HydF, and HydG--play a key role in the synthesis of the [2Fe](H) component of the catalytic H-cluster of FeFe hydrogenase. The radical S-adenosyl-L-methionine enzyme HydG lyses free tyrosine to produce p-cresol and the CO and CN(-) ligands of the [2Fe](H) cluster. Here, we applied stopped-flow Fourier transform infrared and electron-nuclear double resonance spectroscopies to probe the formation of HydG-bound Fe-containing species bearing CO and CN(-) ligands with spectroscopic signatures that evolve on the 1- to 1000-second time scale.

Maternal dietary docosahexaenoic acid supplementation attenuates fetal growth restriction and enhances pulmonary function in a newborn mouse model of perinatal inflammation.

The preterm infant is often exposed to maternal and neonatal inflammatory stimuli and is born with immature lungs, resulting in a need for oxygen therapy. Nutritional intervention with docosahexaenoic acid (DHA; 6.3 g/kg of diet) has been shown to attenuate inflammation in various human diseases.

Perceived behavioral control, intention to get vaccinated, and usage of online information about the human papillomavirus vaccine.

Human papillomavirus (HPV) and the HPV vaccine have been examined through multiple lenses over the past several years, though there is little work examining the role of perceived behavioral control (PBC) and its impact on potential recipients retrieving, understanding, and using online information with regard to the vaccine. This study used survey data to examine the role of PBC as a moderator between attitudes and intention, and subjective norms (SN) and intention to get the HPV vaccine; and PBC as a moderator when seeking out Facebook, YouTube, and Twitter as information sources about HPV. Support was found for each prediction.

The thioredoxin reductase-1 inhibitor aurothioglucose attenuates lung injury and improves survival in a murine model of acute respiratory distress syndrome.

Aims: Inflammation and oxygen toxicity increase free radical production and contribute to the development of acute respiratory distress syndrome (ARDS), which is a significant cause of morbidity and mortality in intensive care patients. We have previously reported increased glutathione (GSH) levels in lung epithelial cells in vitro and attenuated adult murine hyperoxic lung injury in vivo after pharmacological thioredoxin reductase-1 (TrxR1) inhibition. Using a murine ARDS model, we tested the hypothesis that aurothioglucose (ATG) treatment increases pulmonary GSH levels, attenuates lung injury, and decreases mortality in a GSH-dependent manner.

Role of Oxido Incorporation and Ligand Lability in Expanding Redox Accessibility of Structurally Related Mn Clusters.

Photosystem II supports four manganese centers through nine oxidation states from manganese(II) during assembly through to the most oxidized state before O formation and release. The protein-based carboxylate and imidazole ligands allow for significant changes of the coordination environment during the incorporation of hydroxido and oxido ligands upon oxidation of the metal centers. We report the synthesis and characterization of a series of tetramanganese complexes in four of the six oxidation states from MnMn to Mn Mn with the same ligand framework () by incorporating four oxido ligands.

A radical intermediate in tyrosine scission to the CO and CN- ligands of FeFe hydrogenase.

The radical S-adenosylmethionine (SAM) enzyme HydG lyses free l-tyrosine to produce CO and CN(-) for the assembly of the catalytic H cluster of FeFe hydrogenase. We used electron paramagnetic resonance spectroscopy to detect and characterize HydG reaction intermediates generated with a set of (2)H, (13)C, and (15)N nuclear spin-labeled tyrosine substrates. We propose a detailed reaction mechanism in which the radical SAM reaction, initiated at an N-terminal 4Fe-4S cluster, generates a tyrosine radical bound to a C-terminal 4Fe-4S cluster.

Perinatal factors in neonatal and pediatric lung diseases.

Wheezing and asthma are significant clinical problems for infants and young children, particularly following premature birth. Recurrent wheezing in infants can progress to persistent asthma. As in adults, altered airway structure (remodeling) and function (increased bronchoconstriction) are also important in neonatal and pediatric airway diseases.

Mechanism, decomposition pathway and new evidence for self-healing of manganese oxides as efficient water oxidizing catalysts: new insights.

The electrochemical water-oxidation reaction usually requires a catalyst to reduce the overpotential and Earth-abundant catalysts, like MnO2, are attracting much attention. Here we use chemometric analysis, EPR and UV-Vis spectroscopies to track Mn(II) and MnO4(-) byproducts to the reaction of a MnO2 film in the presence of cerium(IV) ammonium nitrate. Permanganate ion is involved in at least two key reactions: it may oxidize water to O2 or can combine with Mn(II) to remake MnO2 solid.

Double electron-electron resonance probes Ca²⁺-induced conformational changes and dimerization of recoverin.

Recoverin, a member of the neuronal calcium sensor (NCS) branch of the calmodulin superfamily, is expressed in retinal photoreceptor cells and serves as a calcium sensor in vision. Ca²⁺-induced conformational changes in recoverin cause extrusion of its covalently attached myristate (termed Ca²⁺-myristoyl switch) that promotes translocation of recoverin to disk membranes during phototransduction in retinal rod cells. Here we report double electron-electron resonance (DEER) experiments on recoverin that probe Ca²⁺-induced changes in distance as measured by the dipolar coupling between spin-labels strategically positioned at engineered cysteine residues on the protein surface.

The conformation of P450cam in complex with putidaredoxin is dependent on oxidation state.

Double electron-electron resonance (DEER) spectroscopy was used to determine the conformational state in solution for the heme monooxygenase P450cam when bound to its natural redox partner, putidaredoxin (Pdx). When oxidized Pdx was titrated into substrate-bound ferric P450cam, the enzyme shifted from the closed to the open conformation. In sharp contrast, however, the enzyme remained in the closed conformation when ferrous-CO P450cam was titrated with reduced Pdx.

Formation of MgO-supported manganese carbonyl complexes by chemisorption of Mn(CO)5CH3.

MgO-supported manganese carbonyl complexes were prepared by chemical vapor deposition of Mn(CO)5CH3 on partially dehydroxylated, high-area MgO powder. X-ray absorption spectra identify the resultant surface species, on average, as Mn(CO)4(Os)2 (where the two oxygen ligands are part of the MgO surface), and infrared spectra show that the chemisorption results from the reaction of Mn(CO)5CH3 with OH groups of the MgO surface. Electron paramagnetic resonance and X-ray absorption near edge data indicate that the manganese was in a positive oxidation state other than +2, but the value is not determined, and the IR spectra indicate the presence of a mixture of manganese carbonyls.

Cyclooxygenase-2 in newborn hyperoxic lung injury.

Supraphysiological O2 concentrations, mechanical ventilation, and inflammation significantly contribute to the development of bronchopulmonary dysplasia (BPD).Exposure of newborn mice to hyperoxia causes inflammation and impaired alveolarization similar to that seen in infants with BPD.Previously, we demonstrated that pulmonary cyclooxygenase-2 (COX-2) protein expression is increased in hyperoxia-exposed newborn mice.

Electron paramagnetic resonance analysis of a transient species formed during water oxidation catalyzed by the complex ion [(bpy)2Ru(OH2)]2O(4+).

The ruthenium "blue dimer" [(bpy)2Ru(OH2)]2O(4+)--the first well-defined molecular complex able to catalyze water oxidation at low overpotentials--has been the subject of numerous experimental and computational studies. However, elements of the reaction mechanism remain controversial. Of particular interest is the nature of the O-O bond-forming step.

Mechanism of assembly of the dimanganese-tyrosyl radical cofactor of class Ib ribonucleotide reductase: enzymatic generation of superoxide is required for tyrosine oxidation via a Mn(III)Mn(IV) intermediate.

Ribonucleotide reductases (RNRs) utilize radical chemistry to reduce nucleotides to deoxynucleotides in all organisms. In the class Ia and Ib RNRs, this reaction requires a stable tyrosyl radical (Y(•)) generated by oxidation of a reduced dinuclear metal cluster. The Fe(III)2-Y(•) cofactor in the NrdB subunit of the class Ia RNRs can be generated by self-assembly from Fe(II)2-NrdB, O2, and a reducing equivalent.

Nuclear resonance vibrational spectroscopy and electron paramagnetic resonance spectroscopy of 57Fe-enriched [FeFe] hydrogenase indicate stepwise assembly of the H-cluster.

The [FeFe] hydrogenase from Clostridium pasteurianum (CpI) harbors four Fe-S clusters that facilitate the transfer of an electron to the H-cluster, a ligand-coordinated six-iron prosthetic group that catalyzes the redox interconversion of protons and H(2). Here, we have used (57)Fe nuclear resonance vibrational spectroscopy (NRVS) to study the iron centers in CpI, and we compare our data to that for a [4Fe-4S] ferredoxin as well as a model complex resembling the [2Fe](H) catalytic domain of the H-cluster. To enrich the hydrogenase with (57)Fe nuclei, we used cell-free methods to post-translationally mature the enzyme.