Fast cytochrome bo from Escherichia coli binds two molecules of nitric oxide at CuB

The reaction of nitric oxide (NO) with fast cytochrome bo from Escherichia coli has been studied by electronic absorption, MCD, and EPR spectroscopy. Titration of the enzyme with NO showed the formation of two distinct species, consistent with NO binding stoichiometries of 1:1 and 2:1 with observed dissociation constants at pH 7.5 of approximately 2.3 x 10(-)6 and 3.3 x 10(-)5 M. Monitoring the titration by EPR spectroscopy revealed that the broad EPR signals at g approximately 7.3, 3.7, and 2.8 due to magnetic interaction between high-spin heme o (S = 5/2) and CuBII (S = 1/2) are lost. A high-spin heme o signal at g = 6.0 appears as the 1:1 complex is formed but is lost again on formation of the 2:1 complex, which is EPR silent. The absorption spectrum shows that heme o remains in the high-spin FeIII state throughout the titration. These results are consistent with the binding of up to two NO molecules at CuBII. This has been confirmed by studies with the Cl- adduct of fast cytochrome bo. MCD evidence shows that heme o remains ligated by histidine and water. Addition of excess NO to the Cl- adduct leads to the appearance of a high-spin FeIII heme EPR signal. Hence chloride ion binds to CuB, blocking the binding of a second NO molecule. These results suggest a mechanism for the reduction of NO to nitrous oxide by cytochrome bo and cytochrome c oxidase in which the binding of two cis NO molecules at CuB permits the formation of an N-N bond and the abstraction of oxygen by the heme group.     

College student employment and drinking: A daily study of work stressors, alcohol expectancies, and alcohol consumption.

We examined the within-person relationships between daily work stressors and alcohol consumption over 14 consecutive days in a sample of 106 employed college students. Using a tension reduction theoretical framework, we predicted that exposure to work stressors would increase alcohol consumption by employed college students, particularly for men and those with stronger daily expectancies about the tension reducing properties of alcohol. After controlling for day of the week, we found that hours worked were positively related to number of drinks consumed. Workload was unrelated to alcohol consumption, and work-school conflict was negatively related to consumption, particularly when students expressed strong beliefs in the tension reducing properties of alcohol. There was no evidence that the effects of work stressors were moderated by sex. The results illustrate that employment during the academic year plays a significant role in college student drinking and suggest that the employment context may be an appropriate intervention site to address the problem of student drinking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neocuproine, a selective Cu(I) chelator, and the relaxation of rat vascular smooth muscle by S-nitrosothiols

1. A study has been made of the effect of neocuproine, a specific Cu(I) chelator, on vasodilator responses of rat isolated perfused tail artery to two nitrosothiols: S-nitroso-N-acetyl-D,L-penicillamine (SNAP) and S-nitroso-glutathione (GSNO). 2. Bolus injections (10 microl) of SNAP or GSNO (10(-7)-10(-3) M) were delivered into the lumen of perfused vessels pre-contracted with sufficient phenylephrine (1-7 microM) to develop pressures of 100-120 mmHg. Two kinds of experiment were made: SNAP and GSNO were either (a) pre-mixed with neocuproine (10(-4) M) and then injected into arteries; or (b) vessels were continuously perfused with neocuproine (10(-5) M) and then injected with either pure SNAP or GSNO. 3. In each case, neocuproine significantly attenuated vasodilator responses to both nitrosothiols, although the nature of the inhibitory effect differed in the two types of experiment. We conclude that the ability of exogenous nitrosothiols to relax vascular smooth muscle in our ex vivo model is dependent upon a Cu(I) catalyzed process. Evidence is presented which suggests that a similar Cu(I)-dependent mechanism is responsible for the release of NO from endogenous nitrosothiols and that this process may assist in maintaining vasodilator tone in vivo.     

'Le roi le veult'

Following the fiftieth anniversary of the National Health Service Act 1946, I make the case in this article that professional provision of health care must remain the property of the citizen under common law and must not become a commodity that is bought and sold by third parties, including the state.     

Investigation of steel containment buckling under dynamic loads

Buckling of freestanding nuclear steel containment buildings from dynamic base excitation was investigated in a combined experimental/numerical program. A polycarbonate scale model of a containment building was excited with scaled earthquake transients and single-frequency harmonic transients to determine the peak base acceleration levels required to induce buckling. Buckling was identified using recorded signals from strain gages and accelerometers, with high-speed video records, and by audibility. Experimental results are compared with numerical results obtained by using a freezing-in-time technique. The results are preliminary, since several more tests are to be performed. However, the limited data obtained indicate that the freezing-in-time technique approximates the required acceleration levels reasonably well, although not conservatively. Additional experiments are described that will take containment asymmetries into account, as well as use instrumentation that will provide more accurate measures of the occurrence of buckling.     

General solutions of the narrow strip (and slot) integral equations

Analytic solutions of the integral equations for the current induced on a narrow conducting strip are obtained by two methods. One method follows from an expansion of the strip current in a series of Chebyshev polynomials while the other is based on a special power series expansion. In the former, Fourier-type coefficients, depending on integrals of the excitation, are derived while in the latter the coefficients depend upon derivatives of the excitation. From knowledge of the strip current simple expressions for the far-zone scattered field are derived. Explicit results are given for plane wave excitation. The solution methods apply to the equations for the narrow slot in a planar conducting screen.     

The integrated multiscale modeling of diamond chemical vapor deposition

The fundamental mechanisms of diamond growth occur on the atomic scale; however, the geometry of the deposition reactor and the other operating parameters directly affect the chemical composition of the gas and the temperature at the growth surface. The properties are, in turn, controlled by both atomic- and microstructural-scale features. By developing diamond-growth models at each length scale and coupling the output of one model into the next, a comprehensive simulation scheme for diamond deposition is realized. This approach provides the missing link between chemical vapor deposition reactor design/operating conditions and the material structure/properties.     

Mechanisms of Hydroquinone-Induced Growth Reduction in Leafy Spurge

Field observations indicate leafy spurge (Euphorbia esula) is inhibited by the presence of Antennaria microphylla. Hydroquinone (HQ), one of several compounds isolated from A. microphylla has been shown to inhibit leafy spurge seed germination, root elongation, and callus culture growth. The present study was designed to analyze the effects of HQ on water relations and photosynthesis of leafy spurge. Plants grown in 0.25 mM HQ had consistently higher leaf diffusive resistance and lower transpiration rates than control plants (P < 0.05). Chlorophyll fluorescence was significantly lower than controls (P < 0.05) towards the end of the treatment period. At the end of the treatment, tissue from 0.25 mM HQ plants had higher levels of ¹³C, indicating there had been a sustained interference with stomatal function. These data suggest that a disruption of the plant water balance is one mechanism of leafy spurge inhibition by A. microphylla.