[FeFe]-hydrogenase oxygen inactivation is initiated at the H cluster 2Fe subcluster.

The [FeFe]-hydrogenase catalytic site H cluster is a complex iron sulfur cofactor that is sensitive to oxygen (O2). The O2 sensitivity is a significant barrier for production of hydrogen as an energy source in water-splitting, oxygenic systems. Oxygen reacts directly with the H cluster, which results in rapid enzyme inactivation and eventual degradation. To investigate the progression of O2-dependent [FeFe]-hydrogenase inactivation and the process of H cluster degradation, the highly O2-sensitive [FeFe]-hydrogenase HydA1 from the green algae Chlamydomonas reinhardtii was exposed to defined concentrations of O2 while monitoring the loss of activity and accompanying changes in H cluster spectroscopic properties. The results indicate that H cluster degradation proceeds through a series of reactions, the extent of which depend on the initial enzyme reduction/oxidation state. The degradation process begins with O2 interacting and reacting with the 2Fe subcluster, leading to degradation of the 2Fe subcluster and leaving an inactive [4Fe-4S] subcluster state. This final inactive degradation product could be reactivated in vitro by incubation with 2Fe subcluster maturation machinery, specifically HydF(EG), which was observed by recovery of enzyme activity.

Does the American College of Surgeons New Level I Children's Surgery Center Verification Affect Treatment Efficiency and Narcotic Administration in Treating Pediatric Trauma Patients with Femur Fracture?

BACKGROUND: In 2015, the American College of Surgeons (ACS) created a new hospital improvement program to enhance the performance of pediatric care in US hospitals. The Children's Surgery Verification (CSV) Quality Improvement Program is predicated on the idea that pediatric surgical patients have improved outcomes when treated at children's hospitals with optimal resources. Achieving ACS level I CSV designation at pediatric trauma centers may lead to greater benefits for pediatric trauma patients; however, the specific benefits have yet to be identified. We hypothesize that achieving the additional designation of ACS level I CSV is associated with decreased narcotic use perioperatively and improved efficiency when managing pediatric patients with femur fractures. STUDY DESIGN: This study is a retrospective analysis of traumatic pediatric orthopaedic femur fractures treated at a verified level I pediatric trauma center before and after CSV designation (2010 to 2014 vs 2015 to 2019). Efficiency parameters, defined as time from admission to surgery, duration of surgery, and duration of hospital stay, and narcotic administration in oral morphine equivalents (OMEs) were compared. RESULTS: Of 185 traumatic femur fractures analyzed, 80 occurred before meeting ACS level I CSV criteria, and 105 occurred after. Post-CSV, there was a significant decrease in mean wait time from admission to surgery (16.64 hours pre-CSV, 12.52 hours post-CSV [p < 0.01]) and duration of hospital stay (103.49 hours pre-CSV, 71.61 hours post-CSV [p < 0.01]). Narcotic usage was significantly decreased in both the preoperative period (40.61 OMEs pre-CSV, 23.77 OMEs post-CSV [p < 0.01]) and postoperative period (126.67 OMEs pre-CSV, 45.72 OMEs post-CSV [p < 0.01]). CONCLUSIONS: Achieving ACS level I CSV designation is associated with increased efficiency and decreased preoperative and postoperative narcotic use when treating pediatric trauma patients.

Biochemical and Structural Properties of a Thermostable Mercuric Ion Reductase from Metallosphaera sedula.

Mercuric ion reductase (MerA), a mercury detoxification enzyme, has been tuned by evolution to have high specificity for mercuric ions (Hg(2+)) and to catalyze their reduction to a more volatile, less toxic elemental form. Here, we present a biochemical and structural characterization of MerA from the thermophilic crenarchaeon Metallosphaera sedula. MerA from M. sedula is a thermostable enzyme, and remains active after extended incubation at 97°C. At 37°C, the NADPH oxidation-linked Hg(2+) reduction specific activity was found to be 1.9 µmol/min⋅mg, increasing to 3.1 µmol/min⋅mg at 70°C. M. sedula MerA crystals were obtained and the structure was solved to 1.6 Å, representing the first solved crystal structure of a thermophilic MerA. Comparison of both the crystal structure and amino acid sequence of MerA from M. sedula to mesophillic counterparts provides new insights into the structural determinants that underpin the thermal stability of the enzyme.

The volume of lung parenchyma as a function of age: a review of 1050 normal CT scans of the chest with three-dimensional volumetric reconstruction of the pulmonary system.

STUDY DESIGN: An Institutional Review Board-approved retrospective review of 3400 sequential CT scans of the thorax obtained at a single institution over a 3-year period from 2000 to 2003 was performed. OBJECTIVES: We determined values for the volume of the right lung, left lung, and total lung volume and plot these data as a function of age and sex. SUMMARY OF BACKGROUND DATA: To our knowledge, no normative data on CT determined lung volume as a function of age have been published. METHODS: All examinations with a report of a normal CT scan of the chest (1050 examinations) were identified. The volume of lung parenchyma in each normal examination was determined by performing a three-dimensional reconstruction of the pulmonary system. RESULTS: Predicted increases in pulmonary volume with age for the third to 97th percentiles of male and female children were calculated. CONCLUSIONS: Normal values for the volume of lung parenchyma as a function of age and sex increase the clinical utility of a standard CT scan of the thorax in evaluating children with complex spinal deformities. They are a useful adjunct to pulmonary function testing. These data can be used in the pre- and postoperative evaluation of patients who are at risk of thoracic insufficiency syndrome, particularly in patients younger than 5 years of age, when standard pulmonary function testing cannot be accomplished. The effects of nonoperative treatment, early spinal fusion, and new techniques for the fusionless management of spinal deformity on lung volume can be quantified and compared to normal values.