Oxygen molecular centers

All protein atoms except hydrogens bonded to carbon were explicitly represented. Positions of polar hydrogens were calculated on the basis of coordinates of the heavier atoms (5) and standard geometric constraints (14). The non-bonded energy for the interaction of the water molecule and the protein was calculated as a sum of electrostatic and 6-12 Lennard-Jones attractive and repulsive contributions for the three atoms of the water molecule and all atoms of the protein within 6 X of the water oxygen s center. Empirical parameters were used for the 6-12 potentials (15,16,17), partial atomic charges were values obtained with molecular orbital calculations (1 ) for hydrogen-bonded interactions modified 6-12 parameters were used (18). 

With the grab sampling technique, a samphng probe is placed at the center of the stack, and a sample is drawn direcfly into an Orsat analyzer or a Fyrite-type combustion-gas analyzer. The sample is then analyzed for carbon dioxide and oxygen content. With these data, the diy molecular weight of the gas stream can then be calculated. 

The fragmentation/cyclization ratio is determined by the relative orientation of the respective molecular orbitals, and thus by the conformation of diradical species 2. The quantum yield with respect to formation of the above products is generally low the photochemically initiated 1,5-hydrogen shift from the y-carbon to the carbonyl oxygen is a reversible process, and may as well proceed back to the starting material. This has been shown to be the case with optically active ketones 7, containing a chiral y-carbon center an optically active ketone 7 racemizes upon irradiation to a mixture of 7 and 9 ... 

Zeolite is sometimes called molecular sieve. It has a well defined lattice structure. Its basic building blocks are silica and alumina tetrahedra (pyramids). Each tetrahedron (Figure 3-1) consists of a silicon or aluminum atom at the center of the tetrahedron, with oxygen atoms at the four comers. 

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