共查询到20条相似文献,搜索用时 15 毫秒
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Rosanna Bonaccorsi Renzo Cimiraglia Eolo Scrocco Jacopo Tomasi 《Theoretical chemistry accounts》1974,33(2):97-103
Multipole expansions of the electrostatic molecular potential up to the hexadecapole terms are examined for H2O, NH3 and C2H4NH. A reasonable approximation to get unexpensive first order representations of the electrostatic potential for regions outside the van der Waals volume is found. 相似文献
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The overlap multipole expansion procedure is utilized for the evaluation of the component of the electrostatic molecular potential of the B-DNA helix due to its sugar-phosphate backbone. The overall shape of the potential, its extension in space, the location of the minima and the differences in the values of the potential in particularly significant regions (minor and major grooves, vicinity of the phosphates) are indicated. The isopotential surfaces are practically cylindrical at distances larger than 15 Å from the helix axis but exhibit a more complex structure at shorter distances.This paper is dedicated to Professor H. Hartmann on the occasion of his 65th birthday. 相似文献
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The influence of a single and double helical DNA environment on the molecular electrostatic potentials at the C8 and amino sites of guanine and adenine are studied. The results are employed in a tentative explanation of the variation in binding sites of N-acetoxy-N-2-acetylaminofluorene with DNA, following whether the nucleic acid is in a native or denatured state. 相似文献
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Alessandro Agresti Rosanna Bonaccorsi Jacopo Tomasi 《Theoretical chemistry accounts》1979,53(3):215-220
A method for getting approximate but realistic evaluations of the electrostatic molecular potential for benzene derivatives is presented and discussed. The method is based on a partition of the whole molecular observable into directly transferable contributions, which can be calculated without a previous knowledge of the molecular wavefunction. The algorithm, which probably is applicable also to other aromatic compounds, implements a preceding study concerning only unconjugated molecules. 相似文献
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Francesc Manaut Ferran Sanz Jaume José Massimo Milesi 《Journal of computer-aided molecular design》1991,5(4):371-380
Summary A new computer program has been developed to automatically obtain the relative position of two molecules in which the similarity between molecular electrostatic-potential distributions is greatest. These distributions are considered in a volume around the molecules, and the similarity is measured by the Spearman rank coefficient. The program has been tested using several pairs of molecules: water vs. water; phenylethylamine and phenylpropylamine vs. benzylamine; and methotrexate vs. dihydrofolic acid. 相似文献
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Gustav Peinel Horst Frischleder Frieder Birnstock 《Theoretical chemistry accounts》1980,57(3):245-253
Starting from the molecular potential we get, by using elementary electrostatics, information about energetically favoured regions for interaction with ions and dipoles around H2O and H2CO. The molecule-dipole interaction is represented by the electric field patterns. 相似文献
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The calculation of the molecular electrostatic potential from simplified models of the electron density is considered. Results are shown for water, hydrogen fluoride and ammonia. Little loss of accuracy is evident when the density is represented by a linear sum of well-chosen Gaussians. When these are further simplified into sets of point charges the inner parts of the molecule are poorly represented. More elaborate point moments make the representation worse. On the other hand a mixed representation with point charges and one diffuse Gaussian gives all the essential features of the potential of these molecules. 相似文献
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P. Politzer 《Theoretical chemistry accounts》2004,111(2-6):395-399
Starting from the Hohenberg–Kohn theorem, atomic and molecular energies have been expressed rigorously as functionals of the electronic electrostatic potential, Velec(r). Explicit formulations have been derived for the functionals representing the kinetic energy and electronic interaction contributions to the total energies.Acknowledgements. The assistance of Dr. Jane S. Murray is greatly appreciated.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
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Suresh CH Alexander P Vijayalakshmi KP Sajith PK Gadre SR 《Physical chemistry chemical physics : PCCP》2008,10(43):6492-6499
Density functional theory computations at the B3LYP/6-31G(d,p) level have been carried out for three types of model compounds, viz. (i) 4-substituted bicyclo[2.2.2]octane carboxylic acids, (ii) anions of 4-substituted bicyclo[2.2.2]octane carboxylic acids and (iii) 4-substituted quinuclidines where the substituents are NO(2), CN, Cl, Br, CF(3), F, CHO, CH(2)Cl, COOH, COCH(3), CONH(2), OH, OCH(3), C(6)H(5), NH(2), H, CH(3), CH(2)CH(3), CH(CH(3))(2), and C(CH(3))(3) to study the dependencies between molecular electrostatic potential minimum (V(min)) and the inductive substituent constant sigma(I). All the three model systems show excellent linear correlation between V(min) and sigma(I) suggesting that the calculation of V(min) parameter in these systems offers a simple and efficient computational approach for the evaluation of inductive substituent constants. The calculated linear equation for the models (i), (ii), and (iii) are V(min) = 12.982 sigma(I)- 48.867, V(min) = 13.444 sigma(I)- 182.760, and V(min) = 18.100 sigma(I)- 65.785, respectively. Considering the simplicity of the quinuclidine model, V(min) value at the nitrogen lone pair region of a 4-substituted quinuclidine system is recommended for the evaluation of sigma(I). Further, the additivity effect of sigma(I) is tested on multiply substituted quinuclidine and bicyclo[2.2.2]octane carboxylic acid derivatives using the V(min) approach and the results firmly supported the additivity rule of inductive effect. The systems showing considerable deviations from the additivity rule are easily recognized as those showing either steric effect or intramolecular hydrogen bond interactions at the V(min) response site. However, the distance relation of sigma(I) is not well represented in the caged molecular systems. 相似文献
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Victor M. Anisimov Nikolay Anikin Vladislav Bugaenko Vladimir Bobrikov Alexey Andreyev 《Theoretical chemistry accounts》2003,109(4):213-219
Accurate electrostatic maps of proteins are of great importance in research of protein interaction with ligands, solvent
media, drugs, and other biomolecules. The large size of real-life proteins imposes severe limitations on computational methods
one can use for obtaining the electrostatic map. Well-known accurate second-order M?ller–Plesset and density functional theory
methods are not routinely applicable to systems larger than several hundred atoms. Conventional semiempirical tools, as less
resource demanding ones, could be an attractive solution but they do not yield sufficiently accurate calculation results with
reference to protein systems, as our analysis demonstrates. The present work performs a thorough analysis of the accuracy
issues of the modified neglect of differential overlap type semiempirical Hamiltonians AM1 and PM3 on example of the calculation
of the molecular electrostatic potential and the dipole moment of natural amino acids. Real capabilities and limitations of
these methods with application to protein modeling are discussed.
Received: 26 April 2002 / Accepted: 19 September 2002 /
Published online: 14 February 2003 相似文献
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It has been rigorously established by means of classical electrostatic arguments, that molecular electrostatic potential maps
are devoid of local maxima. This forms a generalization of the earlier works of Politzer and co-workers which were restricted
to the case of atoms. 相似文献
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The molecular electrostatic potentials and steric accessibilities associated with reactive sites of C-DNA are calculated for the sequences poly(dG · dC) and poly(dA · dT). The distribution of potential on the surface envelopes of the double helices are also presented. The results are compared with those obtained for B-DNA. 相似文献
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Molecular electrostatic potentials (MESP) surrounding the pi-region of several substituted ethylenes (CH(2)CHR) have been characterized by locating the most negative-valued point (V(min)) in that region. The substituents have been classified as electron donating and withdrawing on the basis of the increase or decrease in the negative character of V(min) in these systems as compared to ethylene. The values of V(min) show a good linear correlation with the Hammett sigma(p) constants, suggesting that the substituent electronic effects in substituted ethylenes and substituted benzenes are basically similar. With electron-donating substituents, the position of MESP minimum is closer to the unsubstituted carbon facilitating the pi-complex formation of it with HCl at this site. Such a regiospecific pi-complex formation is found to favor the formation of Markovnikov-type transition state for the addition of HCl to CH(2)CHR. For the electron-withdrawing substituents, the V(min) location is almost equidistant and farther from the ethylenic carbon atoms. This and the less negative V(min) values account for the less regiospecific CH(2)CHR...HCl pi-complexes as well as the transition states for the HCl addition to CH(2)CHR when R is an electron-withdrawing group. The interaction energy (E(int)) between CH(2)CHR and HCl for the formation of the CH(2)CHR...HCl pi-complex shows a good linear correlation with the corresponding V(min) value. 相似文献
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Nesmeyanov Institute for Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturoi Khimii, Vol. 30, No. 2, pp. 178–181, March–April, 1989. 相似文献
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The electrostatic molecular potentials arising from ab initio MO LCAO GTO SCF wavefunctions for some five membered heterocycles are used to make evident differences in reactivity of some sites (tertiary nitrogen, carbon atoms) towards electrophilic reagents. Results are in general accordance with experiment. 相似文献
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A new method for generating atom-centered charges for use in condensed phase computer simulations is presented, which is based on a restrained electrostatic potential (RESP) procedure. Charges are calculated from a least-squares fit to the quantum mechanical electrostatic potential with a restraint applied to reduce their magnitude. The restraint developed here offers advantages over that used in RESP. The magnitude of the restraint is optimized to yield charges as close to the equivalent OPLS values as possible while still reproducing the molecule's electrostatic potential. A cross-validation analysis is used to show that the restraint is insensitive to the selection of OPLS molecules from which it is derived. Thus, with this method, OPLS-like charges may be produced from the electrostatic potential for atom types not in the OPLS force field. In addition, the restraint is shown to reduce the conformational dependence of the charges. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 483–498, 1999 相似文献
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Carlo Petrongolo Harry J. T. Preston Joyce J. Kaufman 《International journal of quantum chemistry》1978,13(4):457-468
The electrostatic potential V( r ) arising from the ab initio LCAO-MO-SCF wave functions of chlorpromazine (CPZ ) and promazine (PZ ) has been calculated and discussed. In this approximation, the most probable sites of attack and reaction paths of electrophilic reagents are pointed out and compared. The analysis of V( r ) shows that the phenothiazine group has strong nucleophilic properties which are influenced by the phenothiazine substituent and that the electrostatic reactivity of CPZ and PZ is decidedly different near the phenothiazine substituent and similar near the side chain N atom. The dependence of V( r ) on the accuracy of the wave function has also been discussed by comparing some ab initio results on pyrrole, pyrazole, and imidazole obtained with a large basis set with an ab initio minimum basis set and with CNDO calculations. 相似文献