A number of interesting heterocycles were prepared through interaction of the intermediate 3-amino-8-hydroxy-4-imino-6-methyl-5-phenyl-4,5-dihydro-3H-chromeno-[2,3-d]pyrimidine (1) and reagents such as hydrazonyl halides 2 to furnish triazine derivatives 4a-l. Reaction of 1 with phenacyl bromide afforded compound 5. Moreover, the title compound 1 was subjected to condensation with active methyl...

The ammonia monooxygenase (AMO) of Nitrosomonas europaea is a metalloenzyme that catalyses the oxidation of ammonia to hydroxylamine. We have identified histidine 191 of AmoA as the binding site for the oxidized mechanism-based inactivator acetylene. Binding of acetylene changed the molecular mass of His-191 from 155.15 to 197.2 Da (+42.05), providing evidence that acetylene was oxidized to ket...

We have investigated, by means of ab initio and DFT calculations, the magnitude of through-space spin-spin couplings (JCH and JHH) in CH/π bonded van der Waals dimers involving acetylene, and in a structurally related covalent compound (4ethynylphenanthrene). Within regions where the interaction is stabilizing JHH couplings are very small (< 0.1 Hz) for all complexes. In the acetylene-methane c...

Acetylene-black paste without a light scattering layer was applied to meso-porous TiO2 photo-electrode films with a crystalline framework, a low residual carbon, and a tunable morphological pore size. The thermal-treated TiO2 photo-electrode films had an increased acetylene-black concentration with an increase in artificial pores and a decrease in residual carbon. The performance of dye-sensiti...

An ultra-high vacuum experimental study of acetylene chemisorption on Pt(111) and Pt(100) and of the reaction of hydrogen with the acetylene adsorbate has established distinguishing features of carbon-hydrogen bond breaking and making processes as a function of pressure, temperature, and surface crystallography. The rates for both processes are substantially higher on the Pt(100) surface. Net a...

A simple model is proposed for calculating the reaction yield of a surface reaction of molecules chemisorbed on regular surfaces. An application to benzene from acetylene tricyclization on Pd(111) is performed. The analysis relies on random adsorption of acetylene on the clean crystal surface. The benzene yield is calculated in terms of the acetylene coverage. Analytical results are compared wi...

Nitrogenase catalyzes the MgATP-dependent reduction of dinitrogen gas to ammonia. In addition to the physiological substrate, nitrogenase catalyzes reduction of a variety of other multiply bonded substrates, such as acetylene, nitrous oxide, and azide. Although carbon monoxide (CO) is not reduced by nitrogenase, it is a potent inhibitor of all nitrogenase catalyzed substrate reductions except p...

Examination of interactions among various substrates and inhibitors reacting with a partially purified nitrogenase from Azotobacter vinelandii has shown that: nitrous oxide is competitive with N2; carbon monixide and acetylene are noncompetitive with N2; carbon monoxide, cyanide, and nitrous oxide are noncompetitive with acetylene, whereas N2 is competitive with acetylene; carbon monoxide is no...

Acetylene brings about a progressive inactivation of ammonia mono-oxygenase, the ammonia-oxidizing enzyme in Nitrosomonas europaea. High NH4+ ion concentrations were protective. The inactivation followed first-order kinetics, with a rate constant of 1.5 min-1 at saturating concentrations of acetylene. If acetylene was added in the absence of O2, the cells remained active until O2 was re-introdu...

Endogenous ethylene production was evaluated as a source of ethylene during acetylene reduction assays with freshly collected roots of field-grown corn, Zea mays L. cv Funks G-4646, and sorghum, Sorghum bicolor (L.) Moench. cv CK-60A. Ethylene production was not detected when roots were incubated in air without acetylene. The presence of endogenous ethylene production was confirmed when roots w...