Brian J. Cook

Can Exercise Treat Eating Disorders

Exercise is not a standard intervention for patients with eating disorders. In this article, six studies are reviewed that examined exercise interventions in populations with eating disorders. The key conclusion is that exercise may improve a range of biopsychosocial outcomes in patients with eating disorders, but more research is needed.

The Role of Exercise Dependence for the Relationship between Exercise Behavior and Eating Pathology Mediator or Moderator

Our study examined the potential mediating or moderating effect of exercise dependence on the exercise—eating pathology relationship. Female university students (N = 330) completed Internet-based self-report measures of exercise behavior, exercise dependence, and eating pathology. Exercise dependence served as a mediator for the relationship between exercise and eating pathology. This unidirectional causal model suggests that an individuals pathological motivation or compulsion to exercise is the critical mediating component in the exercise—eating pathology relationship. The best target for removing the link between exercise behavior and eating pathology may be reformulating exercise dependence symptoms.

A multilevel examination of exercise intention and behavior during pregnancy.

Research examining exercising in pregnancy is limited by non-theoretical and cross-sectional assessments that fail to capture the specific physical and psychological demands of the pregnancy trimesters. Drawing on a population in Gainesville, Florida, USA we prospectively examined, within a multilevel design, 61 pregnant womens first and second trimester exercise intention and behavior, and the potential moderating effect of past exercise behavior using the framework of the Theory of Planned Behavior (TPB). Significant cross-sectional associations were found with exercise intention, although the only significant longitudinal effect was the relation between first trimester intention and second trimester changes in exercise behavior. Implications of our findings for study design and exercise intervention development during pregnancy are discussed.

Examination of muscularity and body fat depictions in magazines that target heterosexual and gay men.

Previous content analyses of magazine images have typically examined within genres but failed to include comparisons between publications intended for various populations. The purpose of this study was to examine depictions of muscularity and thinness of male images in several widely distributed magazines that target male audiences from a variety of genres. Twenty-three magazine titles with the highest circulation rates that targeted heterosexual men, gay men, and general audiences were selected for image analyses. We found that magazines that target gay male audiences depicted images of men who were thinner in comparison to magazines targeting heterosexual men. Both gay and heterosexual magazines depicted male images with greater muscularity than magazines intended for general audiences. Differences in male image depictions in magazines may contribute to the promotion of an unattainable body ideal in some subgroups of gay culture.

Two- and Three-Electron Oxidation of Single-Site Vanadium Centers at Surfaces by Ligand Design

Rational, systematic tuning of single-site metal centers on surfaces offers a new approach to increase selectivity in heterogeneous catalysis reactions. Although such metal centers of uniform oxidation states have been achieved, the ability to control their oxidation states through the use of carefully designed ligands had not been shown. To this end, tetrazine ligands functionalized by two pyridinyl or pyrimidinyl substituents were deposited, along with vanadium metal, on the Au(100) surface. The greater oxidizing power of the bis-pyrimidinyltetrazine facilitates the on-surface redox formation of V(3+), compared to V(2+) when paired with the bis-pyridinyltetrazine, as determined by X-ray photoelectron spectroscopy. This demonstrates the ability to control metal oxidation states in surface coordination architectures by altering the redox properties of organic ligands. The metal-ligand complexes take the form of one-dimensional polymeric chains, resolved by scanning tunneling microscopy. The chain structures in the first layer are very uniform and are based on the same quasi-square-planar coordination geometry around single-site V with either ligand. Formation of a different, dimer structure is observed in the early stages of the second layer formation. These systems offer new opportunities in controlling the oxidation state of single-site transition metal atoms at a surface for new advances in heterogeneous catalysts.

Transition Metal Chlorides Are Lewis Acids toward Terminal Chloride Attached to Late Transition Metals

Two different neutral tridentate imine-donor pincer ligands interact with excess MCl2 (M = Co or Cu) to form compounds of the same stoichiometry, (LMCl2)2·MCl2, where the assembling force is the electron richness of the terminal chlorides on the LMCl2 unit. Finite aggregation occurs for M = Co, but for M = Cu, an infinite polymeric structure is adopted, all because MCl2 is bifunctional, which thus bridges multiple MCl units. The bis-pyrazolylpyridine ligand has two acidic NH protons, and both of these are involved in intramolecular hydrogen bonds. The generality of this Lewis acid aggregation is discussed.

Countercations and Solvent Influence CO2 Reduction to Oxalate by Chalcogen-Bridged Tricopper Cyclophanates

One-electron reduction of Cu3EL (L3- = tris(β-diketiminate)cyclophane, and E = S, Se) affords [Cu3EL]-, which reacts with CO2 to yield exclusively C2O42- (95% yield, TON = 24) and regenerate Cu3EL. Stopped-flow UV/visible data support an A→B mechanism under pseudo-first-order conditions ( kobs, 298K = 115(2) s-1), which is 106 larger than those for reported copper complexes. The kobs values are dependent on the countercation and solvent (e.g., kobs is greater for [K(18-crown-6)]+ vs (Ph3P)2N+, and there is a 20-fold decrease in kobs in THF vs DMF). Our results suggest a mechanism in which cations and solvent influence the stability of the transition state.

Catalytic Silylation of Dinitrogen by a Family of Triiron Complexes

A series of triiron complexes supported by a tris(β-diketiminate)cyclophane (L 3- ) catalyze the reduction of dinitrogen to tris(trimethylsilyl)amine using KC8 and Me3SiCl. Employing Fe3Br3 L affords 83 ± 7 equiv. NH4 +/complex after protonolysis, which is a 50% yield based on reducing equivalents. The series of triiron compounds tested evidences the subtle effects of ancillary donors, including halides, hydrides, sulfides, and carbonyl ligands, and metal oxidation state on N(SiMe3)3 yield, and highlight Fe3(μ3-N)L as a common species in product mixtures. These results suggest that ancillary ligands can be abstracted with Lewis acids under reducing conditions.

Chalcogen Impact on Covalency within Molecular [Cu3(μ3-E)]3+ Clusters (E = O, S, Se): A Synthetic, Spectroscopic, and Computational Study

Reaction of the tricopper(I)-dinitrogen tris(β-diketiminate) cyclophane, Cu3(N2)L, with O-atom-transfer reagents or elemental Se affords the oxido-bridged tricopper complex Cu3(μ3-O)L (2) or the corresponding Cu3(μ3-Se)L (4), respectively. For 2 and 4, incorporation of the bridging chalcogen donor was supported by electrospray ionization mass spectrometry and K-edge X-ray absorption spectroscopy (XAS) data. Cu L2,3-edge X-ray absorption data quantify 49.5% Cu 3d character in the lowest unoccupied molecular orbital of 2, with Cu 3d participation decreasing to 33.0% in 4 and 40.8% in the related sulfide cluster Cu3(μ3-S)L (3). Multiedge XAS and UV/visible/near-IR spectra are employed to benchmark density functional theory calculations, which describe the copper-chalcogen interactions as highly covalent across the series of [Cu3(μ-E)]3+ clusters. This result highlights that the metal-ligand covalency is not reserved for more formally oxidized metal centers (i.e., CuIII + O2- vs CuII + O-) but rather is a significant contributor even at more typical ligand-field cases (i.e., Cu3II/II/I + E2-). This bonding is reminiscent of that observed in p-block elements rather than in early-transition-metal complexes.

A Tricopper(I) Complex Competent for O Atom Transfer, C–H Bond Activation, and Multiple O2 Activation Steps

Oxygenation of a tricopper(I) cyclophanate (1) affords reactive transients competent for C-H bond activation and O atom transfer to various substrates (including toluene, dihydroanthracene, and ethylmethylsulfide) based on 1H NMR, gas chromatography/mass spectrometry (MS), and electrospray ionization (ESI)/MS data. Low product yields (<1%) are determined for C-H activation substrates (e.g, toluene, ethylbenzene), which we attribute to competitive ligand oxidation. The combined stopped-flow UV/visible, electron paramagnetic resonance, ESI/MS, 1H NMR, and density functional theory (DFT) results for reaction of 1 with O2 are consistent with transient peroxo- and di(oxo)-bridged intermediates. DFT calculations elucidate a concerted proton-coupled electron transfer from toluene to the di(μ-oxo) intermediate and subsequent radical rebound as the C-H activation mechanism. Our results support a multicopper oxidase-like mechanism for O2 activation by 1, traversing species similar to the coplanar Cu3O2 unit in the peroxy and native intermediates.