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  • 1
    Electronic Resource
    Electronic Resource
    Classification of auxin plant hormones by interaction property similarity indices (1998)
    Springer
    Journal of computer aided molecular design 12 (1998), S. 63-79 
    Details
    ISSN: 1573-4951
    Keywords: auxins ; molecular alignment ; molecular interaction field ; molecular modeling ; QSAR ; similarity index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Although auxins were the first type of plant hormone to be identified, little is known about the molecular mechanism of this important class of plant hormones. We present a classification of a set of about 50 compounds with measured auxin activities, according to their interaction properties. Four classes of compounds were defined: strongly active, weakly active with weak antiauxin behaviour, inactive and inhibitory. All compounds were modeled in two low-energy conformations, ‘P’ and ‘T’, so as to obtain the best match to the ‘planar’ and ‘tilted’ conformations, respectively, of indole 3-acetic acid. Each set of conformers was superimposed separately using several different alignment schemes. Molecular interaction energy fields were computed for each molecule with five different chemical probes and then compared by computing similarity indices. Similarity analysis showed that the classes are on average distinguishable, with better differentiation achieved for the T conformers than the P conformers. This indicates that the T conformation might be the active one. Further, a screening was developed which could distinguish compounds with auxin activity from inactive compounds and most antiauxins using the T conformers. The classifications rationalize ambiguities in activity data found in the literature and should be of value in predicting the activities of new plant growth substances and herbicides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007973008558
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative ab initio SCF conformational study of 4-chloro-indole-3-acetic acid and indole-3-acetic acid phytohormones (auxins) (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1727-1733 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio conformational analysis of 4-chloroindole-3-acetic acid was performed at the RHF/6-311G * * level. The mirror symmetrical conformer (in which the indole ring is coplanar with the COOH group) is most stable; next in energy are the two conformers with the C - COOH fragment perpendicular to the indole ring with relative energies of 2.72 and 6.69 kJ/mol. H(SINGLEBOND)Cl hydrogen bonding results in only a minor stabilization. The results are combined with those obtained earlier for indole-3-acetic acid and recent biological data regarding auxin (growth hormone) activity. From this, assumptions concerning the biologically active conformation are drawn. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    RHF conformational analysis of the auxin phytohormones n-ethyl-indole-3-acetic acid (n=4, 5, 6) (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 1169-1175 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: RHF/6-31G* investigations of 4-, 5-, and 6-ethyl(Et)-indole-3-acetic acid (IAA) yielded 11 symmetry-unique local minima with syn-periplanar orientation of the —COOH group for each of these compounds. The global minima are of C1 symmetry in all cases. Comparison with earlier results shows that ethylation or chlorination in position 5 or 6 introduces only minor changes on the orientation of the acetic acid side group, with no effect on the reaction paths related to this group. For 4-Et-IAA, the deviations from unsubstituted IAA are larger but preserve the pattern of reaction paths that is present in unsubstituted IAA, which is in contrast to 4-Cl-IAA, where local minima and reaction paths are completely different.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1169-1175, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Systematic ab initioSCF conformational analysis of indol-3-ylacetic acid phytohormone (auxin): Comparison with experiment and molecular mechanics calculationsDedicated to Prof. Dieter Klämbt on the occasion of his 65th birthday. (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 75-81 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Indol-3-ylacetic acid (IAA) is a plant growth hormone (auxin) which controls a number of physiological functions in higher plants. Molecular recognition approaches based on structure/activity correlations include the conformational properties of the substrate. Thus a detailed ab initio SCF (RHF) conformational analysis of IAA has been performed with the basis sets STO-3G, 3-21G, 4-31G, 6-31G* and 6-311G**. A significant basis set dependence occurs for the two smallest basis sets; the results obtained with the largest basis sets agree well with experimental gas phase, and solid state data. Comparison of the ab initio results with those obtained from MM calculations with MM2(87), MM3, CVFF, and cff91 shows considerable differences: MM calculations are unable to locate two of the four different ab initio conformers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560708
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