Electron paramagnetic resonance studies of the tungsten-containing formate dehydrogenase from Clostridium thermoaceticum

The redox centers in the tungsten-containing formate dehydrogenase from Clostridium thermoaceticum were examined by potentiometric titration and electron paramagnetic resonance spectroscopy. At low temperature two overlapping iron-sulfur signals which correlated with enzymatic activity were observed with formal potentials near -400 mV vs. SHE. Based on their temperature dependences, one signal is assigned to a reduced Fe2S2 cluster and one to a reduced Fe4S4 cluster. Quantitation of signal intensity suggests two Fe2S2 and two Fe4S4 clusters per formate dehydrogenase molecule. Another signal (g = 2.101, 1.980, 1.950) present in low concentrations at more negative potentials was observable up to 200 degrees K and is not attributed to any iron-sulfur cluster. The possible origin of this signal is analyzed using ligand field theory, and the redox behavior is considered with respect to possible ligation at the active site.     

Oxygen-derived free radicals and hemolysis during open heart surgery

Reperfusion injury occurs during open-heart surgery after prolonged cardioplegic arrest. Cardiopulmonary bypass also is known to cause hemolysis. Since reperfusion of ischemic myocardium is associated with the generation of oxygen free radicals, and since free radicals can attack a protein molecule, it seems reasonable to assume that hemolysis might be the consequence of free radical attack on hemoglobin protein. The results of this study demonstrated that reperfusion following ischemic arrest caused an increase in free hemoglobin and free heme concentrations, simultaneously releasing free iron and generating hydroxyl radicals. In vitro studies using pure hemoglobin indicated that superoxide anion generated by the action of xanthine oxidase on xanthine could release iron from the heme ring and cause deoxygenation of oxyhemoglobin into ferrihemoglobin. This study further demonstrated that before the release of iron from the heme nucleus, oxyhemoglobin underwent deoxygenation to ferrihemoglobin. The released iron can catalyze the Fenton reaction, leading to the formation of cytotoxic hydroxyl radical (OH·). In fact, the formation of OH. in conjunction with hemolysis occurs during cardiac surgery, and when viewed in the light of the in vitro results, it seems likely that oxygen-derived free radicals may cause hemolysis during cardiopulmonary bypass and simultaneously release iron from the heme ring, which can catalyze the formation of OH·.     

“Prey Play”: Learning about Predators and Prey through an Interactive,Role-Play Game

“Prey Play” is an interactive role-play activity that provides fifth-grade students with opportunities to examine predator–prey interactions. This four-part, role-play activity allows students to take on the role of a predator and prey as they reflect on the behaviors animals exhibit as they collect food and interact with one another, as well as limiting factors. Through this activity, students will enhance their communication and observation skills and showcase their creativity.     

Hyperosmotic volume regulation in the gills of the ribbed mussel, Geukensia demissa: rapid accumulation of betaine and alanine

The content of betaine and alanine in gills of the ribbed mussel Geukensia demissa increases rapidly following transfer of the tissues from 250 to 1000 mOsm seawater (SW). Increases in alanine, proline and glycine account for most of the increase in the amino acid pool. The betaine content increases from 45 to 150 μmol/g dry weight within 12 h. Transfer of isolated gills from 250 to 1000 mOsm SW results in a temporary cessation of all ciliary activity. Within 20–40 min following transfer, ciliary activity has recovered. Recovery of ciliary activity precedes recovery of tissue hydration. The uric acid content of gills is unchanged by exposure to hyperosmotic media, suggesting that uric acid is not a store of nitrogen for alanine synthesis from pyruvate. In other organisms, the accumulation of betaine in response to hyperosmotic stress is a slow (days to weeks) process that probably involves changes in gene expression. The rapid, large increases in betaine reported here suggest that gene expression is not a factor in volume recovery by euryhaline bivalve tissues exposed to acute hyperosmotic stress.     

Exploration of the P1 SAR of aldehyde cathepsin K inhibitors

The synthesis and biological activity of a series of aldehyde inhibitors of cathepsin K are reported. Exploration of the properties of the S(1) subsite with a series of alpha-amino aldehyde derivatives substituted at the P(1) position afforded compounds with cathepsin K IC(50)s between 52 microM and 15 nM.     

Efficacy of transgenic cotton containing a cry1Ac gene from Bacillus thuringiensis against Helicoverpa armigera (Lepidoptera: Noctuidae) in northern China

NuCOTN 33B, a Bt transgenic variety of upland cotton (Gossypium hirsutum L.) expressing the insecticidal protein Cry1Ac from Bacillus thuringiensis Berliner sp. kurstaki, was evaluated for resistance to Helicoverpa armigera (Hübner) during 1998-2000 in northern China. The results indicated that there was no significant difference in egg densities between NuCOTN 33B and three nontransgenic varieties (DP5415, Zhongmian12, and Shiyuan321) during the season, although the survival of larvae on NuCOTN 33B seemed significantly reduced. High larval densities observed on non-Bt cotton appeared in great contrast to the low larval populations observed on NuCOTN 33B plants during the seasons. In an environment without insecticide sprays, the annual ginned cotton yields in NuCOTN 33B plots, ranging from 1391.17 to 1511.35 kg/ha, were significantly higher than those in non-Bt cotton (340.34-359.58 kg/ha). These high levels of field efficacy for NuCOTN 33B against H. armigera in northern China may pave the way for reduced pesticide applications and an expansion of alternative pest-control strategies.     

Pulmonary bioavailability of ascorbic acid in an ascorbate-synthesising species,the horse

Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p < 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p < 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.     

Acyclic, orally bioavailable ketone-based cathepsin K inhibitors

Starting from a potent ketone-based inhibitor with poor drug properties, incorporation of P(2)-P(3) elements from a ketoamide-based inhibitor led to the identification of a hybrid series of ketone-based cathepsin K inhibitors with better oral bioavailability than the starting ketone.     

Ketoheterocycle-based inhibitors of cathepsin K: a novel entry into the synthesis of peptidic ketoheterocycles

Ketoheterocyclic inhibitors of cathepsin K have been disclosed. SAR of potency enhancing P2-P3 groups coupled with ketoheterocyclic warheads to provide cathepsin K inhibitors have been described. In addition, a novel route to access alpha-ketothiazoles using a key thioamide functionality has been disclosed. The mild method employed allows for the presence of diverse functional groups, such as amide and carbamate functionalities, commonly found in protease inhibitors that have peptidomimetic scaffolds. This new method should provide a quick entry into functionally diverse protease inhibitors.