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** Ab initio calculations complexes **

** Ab initio quantum chemical calculations **

** Calculation quantum chemical calculations **

** Complex stabilization calculations **

An NMR study has shown that the amino form (419) is the predominant tautomer of 2-[arylamino(imino)]-4a,5,6,7,8,8a-hexahydro-(47f)-l,3,4-benzoxadiazines. The proton-transfer tautomerism of 4-azabenzimidazole, mediated by hydrogen-bonded complexes, has been studied in the ground and excited states by means of absorption and emission spectroscopy, and it has been shown that 6-nitro and 8-nitro groups in the tetrazolo[l,5-a]pyridine molecule exhibit completely different influences on the tetrazole-azide equilibrium. The solvent effect on the azo-hydrazone tautomeric equilibrium of l-phenylazo-4-naphthol has been modelled by using ab initio quantum-chemical calculations. The results have shown that the hydrazone form is more stable in water, while methanol stabilizes the azo form. [Pg.657]

A reaction looked at earlier simulates borate inhibition of serine proteinases. Resorufin acetate (234) is proposed as an attractive substrate to use with chymotrypsin since the absorbance of the product is several times more intense than that formed when the more usual /j-nitrophenyl acetate is used as a substrate. The steady-state kait values are the same for the two substrates, which is expected if the slow deacylation step involves a common intermediate. Experiments show that the acetate can bind to chymotrypsin other than at the active site. Brownian dynamics simulations of the encounter kinetics between the active site of an acetylcholinesterase and a charged substrate together with ab initio quantum chemical calculations using the 3-2IG set to probe the transformation of the Michaelis complex into a covalently bound tetrahedral intermediate have been carried out. " The Glu 199 residue located near the enzyme active triad boosts acetylcholinesterase activity by increasing the encounter rate due to the favourable modification of the electric field inside the enzyme and by stabilization of the TS for the first chemical step of catalysis. " [Pg.73]

** Ab initio calculations complexes **

** Ab initio quantum chemical calculations **

** Calculation quantum chemical calculations **

** Complex stabilization calculations **

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