Restrained point-charge models for disaccharides
| Autor: | Bruce L. Bush, Ulf Ryde, Emma Sigfridsson |
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| Rok vydání: | 2002 |
| Předmět: |
Models
Molecular Sucrose rank-deficiency problems Point particle Static Electricity Disaccharides Molecular physics Ion Partial charge Computational chemistry conformational Linear form Static electricity Theoretical chemistry Molecule Computer Simulation Theoretical Chemistry Ions chemical transferability Chemistry transferability Water Charge (physics) General Chemistry Computational Mathematics restrained electrostatic potential charges atomic charges |
| Zdroj: | Journal of Computational Chemistry; 23(3), pp 351-364 (2002) |
| ISSN: | 0192-8651 1096-987X |
| Popis: | Various methods for deriving atomic partial charges from the quantum chemical electrostatic potential and moments have been tested for the sucrose molecule. We show that if no further information is used, the charges on some carbon atoms become large and charge patterns involving these atoms are badly determined and poorly transferable. Adding lone-pairs on the ether oxygen atoms or dividing the molecule into smaller fragments did not cure the instabilities. We develop a method, CHELP-BOW0, that restrains charges toward zero with different weights for different atoms. These harmonic restraints preserve the linear form of the least-squares equations, which are solved in a single step using singular-value decomposition. CHELP-BOW0 improves the chemical transferability of the charges compared to unrestrained methods, and slightly improves their conformational transferability. It introduces a modest degradation of the fit compared to unrestrained CHELP-BOW (mean average deviation of the potential 0.00016 vs. 0.00010 a.u.). A second new method, CHELP-BOWC, avoids the need for restraints by including several conformations in the fit, weighting each according to its estimated energy in solution. CHELP-BOWC charges are more transferable than CHELP-BOW or CHELP-BOW0 charges to conformations not included in the training set. Restraints to zero charge do not further improve transferability of the CHELP-BOWC charges. We, therefore, recommend CHELP-BOW charges for rigid molecules and CHELP-BOWC charges for flexible molecules. (C) 2002 John Wiley Sons, Inc. |
| Databáze: | OpenAIRE |
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