How do metalloenzymes propagate and control chemical reactions?

Enzymes control and propagate a dizzying array of chemical reactions, including radical reactions and reactions cleaving carbon-carbon bonds. Metalloenzymes, which contain a metal cofactor, are particularly adept at propagating these reactions. This thesis focuses on several metalloenzymes; each an example of a different unique reaction control strategy. Both experimental and computational methodologies have been employed in order to identify specific residues or features which contribute to each enzyme\u27s ability to control the reaction. Emphasis is made on special properties of the metal Manganese. Controlling residues include not only first shell or active site residues, but also residues more distant from the active-site. Further, manipulation of such residues can be used to alter reactivity at non -active-sites, or to alter the apparent electrostatics of the protein (in the case of substitution of hydrogen with fluorine). Electron Paramagnetic Resonance (EPR) and other forms of magnetic spectroscopy can be used to evaluate subtle differences imposed by substitution for controlling residues to a metal center, which gives further insight into the electronic contributions of given residues, as well as the electronic properties of metal cofactors. In summary, the catalysis by Mn-dependent and other metal-dependent metalloenzymes can be investigated through multiple kinetic and spectroscopic avenues, unveiling suprising and novel themes in enzymatic catalysis, such as mechano-chemical switches and super long-distance metallo-interactions

Evaluation of nebulised hypertonic saline (7%) as an adjunct to physiotherapy in patients with stable bronchiectasis

AbstractSputum clearance is of prime importance in the management of patients with bronchiectasis. While nebulised normal isotonic saline (0.9%) (IS) has been anecdotally used to treat patients with tenacious sputum, the use of hypertonic saline (7%) (HS) could have potential muco-protective and clearance properties.24 patients with bronchiectasis were randomised to receive four single treatment schedules in random order: (1) active cycle breathing technique (ACBT) alone, (2) nebulised terbutaline then ACBT, (3) nebulised terbutaline, nebulised IS then ACBT and (4) nebulised terbutaline, nebulised HS then ACBT.Sputum weights were significantly higher after HS than IS (P=0.002). Ease of expectoration also differed overall (P=<0.0001) and was significantly lower with HS than with IS (P=0.0005). Sputum viscosity differed between treatment phases, with a significant linear trend to reduced sputum viscosity with HS (P=0.0002). These changes were associated with small but statistically significant differences in FEV1 (P=0.043) and FVC (P=0.011) between treatment phases.Nebulised hypertonic saline can be used safely and effectively as an adjunct to physiotherapy in selected patients. A long-term prospective trial is now indicated to determine its effectiveness on long-term infection rate, quality of life and lung function

Predicting return to work from health related welfare following low intensity cognitive behaviour therapy

The aim of this study was to identify predictors of return to work in the short and long term following condition management cognitive-behavioural therapy (CM-CBT). All participants (N = 3794) were disability welfare claimants, unemployed due to the presence of a physical or mental health condition. CM-CBT consisted of a seven session group cognitive-behavioural psychoeducational programme, with participants followed-up at 3 and 12-30 months. The primary employment outcome measure was a categorical measure of either returned to work, made progress towards work or remained on welfare. Results index an incremental progress and return to work rate, increasing from 34.41 % at short-term follow-up to 53.07 % at long-term follow-up. Clinically, 17.40 % were classed as recovered following CM-CBT. Reliable psychological change during CM-CBT predicted successful return to work and remaining on welfare was associated with psychological regression over time. The results are discussed in terms of identified methodological weaknesses and the potential of CBT in enabling return to work for the health related unemployed

A Mechanochemical Switch to Control Radical Intermediates

B12-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB12-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch. When the switch is “off”, the 5′-deoxyadenosyl radical moiety is stabilized by releasing the internal strain of an enzyme-imposed conformation. Turning the switch “on,” the enzyme environment becomes the driving force to impose a distinct conformation of the 5′-deoxyadenosyl radical to avoid deleterious radical transfer. This mechanochemical switch illustrates the elaborate way in which enzymes attain selectivity of extremely chemically challenging reactions

A 3‐D Model of Gas Generation, Migration, and Gas Hydrate Formation at a Young Convergent Margin (Hikurangi Margin, New Zealand)

We present a three-dimensional gas hydrate systems model of the southern Hikurangi subduction margin in eastern New Zealand. The model integrates thermal and microbial gas generation, migration, and hydrate formation. Modeling these processes has improved the understanding of factors controlling hydrate distribution. Three spatial trends of concentrated hydrate occurrence are predicted. The first trend (I) is aligned with the principal deformation front in the overriding Australian plate. Concentrated hydrate deposits are predicted at or near the apexes of anticlines and to be mainly sourced from focused migration and recycling of microbial gas generated beneath the hydrate stability zone. A second predicted trend (II) is related to deformation in the subducting Pacific plate associated with former Mesozoic subduction beneath Gondwana and the modern Pacific-Australian plate boundary. This trend is enhanced by increased advection of thermogenic gas through permeable layers in the subducting plate and focused migration into the Neogene basin fill above Cretaceous-Paleogene structures. The third trend (III) follows the northern margin of the Hikurangi Channel and is related to the presence of buried strata of the Hikurangi Channel system. The predicted trends are consistent with pronounced seismic reflection anomalies related to free gas in the pore space and strength of the bottom-simulating reflection. However, only trend I is also associated with clear and widespread seismic indications of concentrated gas hydrate. Total predicted hydrate masses at the southern Hikurangi Margin are between 52,800 and 69,800 Mt. This equates to 3.4–4.5 Mt hydrate/km2, containing 6.33 × 108–8.38 × 108 m3/km2 of methane

Comparing self‐compassion versus body exposure for adult women with moderate to severe body dissatisfaction: A feasibility and pilot trial

This study assessed the feasibility and effectiveness of two brief online interventions for body shame for women with moderate to severe negative body image, to inform the design of a future randomized controlled trial. The primary feasibility outcomes were recruitment, measure completion rates, retention rates and internet connection failure rates. The secondary pilot outcomes were change on clinical measures and state shame ratings during the interventions. Participants were randomized to either online (40-min single session) body exposure or self-compassion interventions. Five validated nomothetic outcome measures (body dissatisfaction, appreciation, eating disorder, external shame and anxiety) were taken at three time points (preintervention, postintervention and 2-week follow-up). Subjective units of body shame (SUBS 0–100 scale) were rated every 5 min during the interventions. The target of recruiting 30 participants in 60 days was successfully achieved. The measure completion rate was high (100%), and retention rates (80% to 100%) showed moderate-to-high acceptability of the interventions. Online delivery was moderately viable with a 12.5% session disconnection rate. The self-compassion intervention significantly reduced SUBS ratings during the course of the intervention, but there was no significant improvement or difference between the interventions on nomothetic outcome measures. Findings suggest that a fully powered trial is viable, and sample size calculation and methodological requirements are provided

Determining the potential link of self-compassion with eating pathology and body image among women: a longitudinal mediational study

Purpose This longitudinal study aims to determine what factors mediate the previously established link between self-compassion and eating pathology/body image concerns, over a 6-month period. Methods A community sample of 274 adult women (M = 29.50 years) completed standardised validated measures of self-compassion (Self-Compassion Scale), rumination (Ruminative Thought Style Questionnaire), shame (Other as Shamer Scale), perfectionism (Short Form of the Revised Almost Perfect Scale), self-criticism (Levels of Self-Criticism Scale), eating pathology (Eating Disorder Examination Questionnaire) and body image (Body Shape Questionnaire). They reported levels of: self-compassion at Time 1, potential mediators (rumination, shame, self-criticism, perfectionism) at 3 months; and eating pathology and body dissatisfaction a further 3 months later. Missing data were handled using multiple imputation. Stepwise multiple regression showed that shame was the most consistent mediator. Results Shame acted as a full mediator of the self-compassion-eating/body image relationship {respectively, [B = .04, SE = .01, t(268) = 3.93, p < .001], [B = .33, SE = .15, t(268) = 2.25, p < .05]}. Discrepancy perfectionism also played a mediating role in the link between self-compassion and body image dissatisfaction [B = .59, SE = .28, t(268) = 2.10, p < .05]. Conclusion These results support the hypothesis that self-compassion is relevant to eating pathology and body image disturbance, and demonstrate that shame is an important mechanism in that relationship. This pattern suggests that interventions that reduce shame should be considered when addressing issues relating to self-compassion and its links to eating disorders. Level of evidence Level IV, multiple time series without intervention

Testing a low-intensity single-session self-compassion intervention for state body shame in adult women: a dismantling randomized controlled trial

State body shame is a risk factor for eating disorders, and self-compassion is emerging as a potentially effective treatment option in such cases. This study tested the efficacy of a brief (15-minute) self-compassion intervention in reducing state body shame. Using dismantling trial methodology, participants were randomly allocated to an active compassion condition (n = 23), an inactive control compassion condition (n = 23), or an educational control condition (n = 23). Measures of state body image and state shame were collected pre-intervention, immediately after the intervention, and a day after the intervention. Subjective units of state body shame (SUBS) were intensively measured during each invention. Self-compassion interventions were equally efficacious at protecting against deterioration of state body shame and were effective at reducing state shame compared to the educational control condition, with medium effect sizes (respectively – np2 =.07 and np2 =.08). Reductions in state shame were retained at follow-up. None of the interventions had an effect on body image (np2 =.04). Findings demonstrate the clinical promise of brief self-compassion interventions, particularly as evidenced-based “homework” exercises

Assigning the EPR fine structure parameters of the Mn(II) centers in bacillus subtilis oxalate decarboxylase by site-directed mutagenesis and DFT/MM calculations

Oxalate decarboxylase (OxDC) catalyzes the Mn-dependent conversion of the oxalate monoanion into CO2 and formate. EPR-based strategies for investigating the catalytic mechanism of decarboxylation are complicated by the difficulty of assigning the signals associated with the two Mn(II) centers located in the N- and C-terminal cupin domains of the enzyme. We now report a mutational strategy that has established the assignment of EPR fine structure parameters to each of these Mn(II) centers at pH 8.5. These experimental findings are also used to assess the performance of a multistep strategy for calculating the zero-field splitting parameters of protein-bound Mn(II) ions. Despite the known sensitivity of calculated D and E values to the computational approach, we demonstrate that good estimates of these parameters can be obtained using cluster models taken from carefully optimized DFT/MM structures. Overall, our results provide new insights into the strengths and limitations of theoretical methods for understanding electronic properties of protein-bound Mn(II) ions, thereby setting the stage for future EPR studies on the electronic properties of the Mn(II) centers in OxDC and site-specific variants