Ab initio calculations on imine-carboxyl complexes and neurotransmitters.
Item
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Title
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Ab initio calculations on imine-carboxyl complexes and neurotransmitters.
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Identifier
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AAI9009733
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identifier
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9009733
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Creator
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Fugler-Domenico, Lillian M.
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Contributor
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Advisers: C. S. Russell | A. M. Sapse
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Date
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1989
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry
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Abstract
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Ab initio calculations are performed in order to investigate the methylene-imine complexes with formic acid using STO-3G and 6-31G basis sets. It is found, for the methylenimine-formic acid and N-methylmethylenimine-formic acid complexes, that (1) species found in the gas phase will exist as a neutral-neutral complex, (2) the STO-3G basis set is not adequate for the description of the charge-pair complex but predicts the correct trend in energy and (3) even though the allyl group stabilizes somewhat the charge-pair complex, the differences between the allylimine-carboxyl and methylenimine-carboxyl interaction are minimal.;Ab initio calculations are also used in order to determine the most stable conformations for {dollar}\gamma{dollar}-aminobutyric acid (GABA), GABA imine, aminooxyacetic acid (AOAA), taurine, hypotaurine and L-2,4-diaminobutyric acid (L-DABA). Structural characteristics are obtained and related to the abilities of the compounds to cross the blood-brain barrier (BBB). It is found that AOAA, which penetrates the BBB, features an intramolecular hydrogen bond. GABA which does not cross the BBB, does not have an intramolecular hydrogen bond. Taurine, features an intramolecular hydrogen bond and has a lower proton affinity at the NH{dollar}\sb2{dollar} group than GABA and therefore can penetrate the BBB, however, slowly. GABA imine and hypotaurine which exhibited properties similar to GABA are predicted not to cross the BBB. The energies for the different conformations of L-DABA are so similar that it is postulated that L-DABA adopts a conformation complementary to a binding site due to its structural flexibility. The proton affinity predicts that L-DABA is a cation when GABA is a neutral molecule. This result correlates well with the experimental data, in that, in high-affinity transport, DABA requires one Na{dollar}\sp+{dollar} while GABA requires two. As such, L-DABA is transported on the GABA carrier with a net charge of +2, where one charge is provided by the cotransported Na{dollar}\sp+{dollar} and the second charge is contributed by the amino acid itself (L-DABA cation). Moreover, a similarity between the most stable cations of L-DABA (cycle) and GABA (partially-folded) are found and there is a possibility that the L-DABA cations are the species which may bind to the synaptosomal receptor.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
