The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
P. C. Mishra - One of the best experts on this subject based on the ideXlab platform.
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Molecular electrostatic potentials and Fields: Hydrogen bonding, recognition, reactivity and modelling
Theoretical and Computational Chemistry, 1996Co-Authors: P. C. Mishra, Anil KumarAbstract:This chapter discusses interMolecular interactions such as hydrogen bonding using a physically observable quantity, the Molecular electrostatic potential (MEP). Hydrogen bonding interaction plays a crucial role in the recognition of biomolecules and drugs. The study of MEP or Molecular Electric Field (MEF) maps helps to obtain reliable estimates of hydrogen bond strengths for a series of molecules and also suggests suitable Molecular modifications to achieve a specific objective in this respect. It can be greatly helpful in drug design. The utility of MEP in relation to several other Molecular properties of chemical interest; for example, nucleophilicity, surface local ionization energy, acidity and directional interMolecular interactions, are established. Using the extremal properties of MEP, sizes of atomic and Molecular anions are investigated. MEP is found to be very useful in analyzing Molecular similarity—a concept of vital importance in the area of drug design. The important developments relating to MEP and MEF, particularly those of the recent years, are reviewed in this chapter.
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A gas phase theoretical study of the hydrogen bonding properties of some androgen antagonists using Molecular orbital and Molecular Electric Field mapping methods
Journal of Molecular Structure-theochem, 1996Co-Authors: Anil Nair, P. C. MishraAbstract:Abstract A number of anilides, alkenes and an indole derivative which are known to be potent anti-androgens were studied using Molecular orbital (AM1) and Molecular Electric Field mapping (MEF) techniques. Linear correlation coefficients between the MEF values near the tertiary hydroxyl groups of these molecules and the corresponding experimentally observed hydrogen bond donating abilities (log K α values) were found to be satisfactory. The study illustrates the usefulness of MEF mapping in predicting the hydrogen bond donating abilities of these molecules.
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Molecular Electric Field mapping and structure-activity relationships for some human O6-alkylguanine-DNA alkyl transferase depleting agents
Journal of Molecular Structure-theochem, 1994Co-Authors: Anil Nair, P. C. MishraAbstract:Abstract Electric Field mapping has been carried out for certain O6- and S6-substituted purine derivatives, some of which are known to have the ability to deplete the human DNA guanine O6-alkylation damage repair enzyme called O6-alkylguanine-DNA alkyltransferase (AGT). Geometries of all the molecules are optimized using the latest semiempirical method, PM3. Point charges at different atomic sites are obtained using Mulliken population analysis. There exists a reasonably good correlation between the average Electric Field values near the N7 atom of the guanine moiety in these molecules and the observed AGT depleting activities. It indicates involvement of the N7 site of the guanine moiety in the reaction of these molecules with AGT, in agreement with earlier suggestions.
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Study of structure-activity relationships for neurotransmitters using Molecular Electric Field mapping: histamine and some of its H2-receptor agonists.
Indian Journal of Biochemistry & Biophysics, 1994Co-Authors: Anil Nair, P. C. MishraAbstract:Molecular Electric Field mapping has been carried out to study structure-activity relationships for neutral and cationic forms of histamine and some of its agonists which are thiazole derivatives. Optimised geometries and Mulliken charges at the atomic sites were obtained using the PM3 method. Electric Field values near the N3-H bond in histamine and those near substituents at the C2 position in the agonists have been found to correlate reasonably well with observed activities. Electric Fields near the sulphur atom in thiazoles indicate that involvement of this site in hydrogen bonding with the H2-receptor is unlikely.
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Molecular Electric Field mapping of some anions and cations of 2- aminopurine and 6- thioguanine
Proceedings of the Indian Academy of Sciences - Chemical Sciences, 1994Co-Authors: C. G. Mohan, P. C. MishraAbstract:Electric Fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed Electric Field patterns satisfactorily explain reactive sites and biological activity of the molecules.
Anil Nair - One of the best experts on this subject based on the ideXlab platform.
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A gas phase theoretical study of the hydrogen bonding properties of some androgen antagonists using Molecular orbital and Molecular Electric Field mapping methods
Journal of Molecular Structure-theochem, 1996Co-Authors: Anil Nair, P. C. MishraAbstract:Abstract A number of anilides, alkenes and an indole derivative which are known to be potent anti-androgens were studied using Molecular orbital (AM1) and Molecular Electric Field mapping (MEF) techniques. Linear correlation coefficients between the MEF values near the tertiary hydroxyl groups of these molecules and the corresponding experimentally observed hydrogen bond donating abilities (log K α values) were found to be satisfactory. The study illustrates the usefulness of MEF mapping in predicting the hydrogen bond donating abilities of these molecules.
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Molecular Electric Field mapping and structure-activity relationships for some human O6-alkylguanine-DNA alkyl transferase depleting agents
Journal of Molecular Structure-theochem, 1994Co-Authors: Anil Nair, P. C. MishraAbstract:Abstract Electric Field mapping has been carried out for certain O6- and S6-substituted purine derivatives, some of which are known to have the ability to deplete the human DNA guanine O6-alkylation damage repair enzyme called O6-alkylguanine-DNA alkyltransferase (AGT). Geometries of all the molecules are optimized using the latest semiempirical method, PM3. Point charges at different atomic sites are obtained using Mulliken population analysis. There exists a reasonably good correlation between the average Electric Field values near the N7 atom of the guanine moiety in these molecules and the observed AGT depleting activities. It indicates involvement of the N7 site of the guanine moiety in the reaction of these molecules with AGT, in agreement with earlier suggestions.
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Study of structure-activity relationships for neurotransmitters using Molecular Electric Field mapping: histamine and some of its H2-receptor agonists.
Indian Journal of Biochemistry & Biophysics, 1994Co-Authors: Anil Nair, P. C. MishraAbstract:Molecular Electric Field mapping has been carried out to study structure-activity relationships for neutral and cationic forms of histamine and some of its agonists which are thiazole derivatives. Optimised geometries and Mulliken charges at the atomic sites were obtained using the PM3 method. Electric Field values near the N3-H bond in histamine and those near substituents at the C2 position in the agonists have been found to correlate reasonably well with observed activities. Electric Fields near the sulphur atom in thiazoles indicate that involvement of this site in hydrogen bonding with the H2-receptor is unlikely.
Jeanphilippe Soumillion - One of the best experts on this subject based on the ideXlab platform.
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new fluorescent model compounds for the study of photoinduced electron transfer the influence of a Molecular Electric Field in the excited state
Angewandte Chemie, 1995Co-Authors: Prasanna A De Silva, H Nimal Q Gunaratne, Jeanlouis Habibjiwan, Colin P Mccoy, Terence E Rice, Jeanphilippe SoumillionAbstract:The location of the “spacer–receptor” unit in a 4-aminonaphthalimide fluorophore, which undergoes internal charge transfer in the excited state, is crucial for the suitability of the compound as a pH sensor. In studies of the pH dependence of the fluorescence of the regioisomers 1 and 2, only 1 displayed desirable properties.
P. F. Meier - One of the best experts on this subject based on the ideXlab platform.
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An ab initio Study of the Molecular Electric-Field Gradients of the Chlorsilanes
Zeitschrift für Naturforschung A, 1996Co-Authors: H. U. Suter, D. M. Maric, P. F. MeierAbstract:AbstractThe Electric Field gradient (EFG) of chlorine in the chlorine containing silanes (SiCl
Ludwik Adamowicz - One of the best experts on this subject based on the ideXlab platform.
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The correlated Molecular electrostatic potential and Electric Field of 2 (1H)-pyrimidone and 2-hydroxypyrimidine
Chemical Physics, 1991Co-Authors: Andrzej Leś, Ludwik AdamowiczAbstract:Abstract The Molecular electrostatic potential and Molecular Electric Field have been estimated by means of the expectation values of the respective one-electron operators. We used the Molecular density matrix that includes the electron correlation effects up to the second-order of the many body perturbation theory. The results show that around the 2(1H)-pyrimidone molecule one may distinguish the electrophilic and nucleophilic regions, the latter characterized by two potential minima of −2.9 V. In the tautomeric form, 2-hydroxypyrimidine, a third potential minimum of −2.1 V appears close to the N1 nitrogen atom. For both molecules strong orientational forces acting on polar solvents are predicted in the vicinity of oxygen (O7) and nitrogen (N3) atoms. The electron correlation effects do not significantly alter the SCF values of the electrostatic potential and Electric Field at the distances within the van der Waals envelope of the pyrimidine bases. At larger distances, however, the correlation correction is significant, particularly in the direction facing the proton transfer path.