An optimized approach to compute hybridization displacement charge and a study of its effects on electrostatic potentials of some biologically important molecules

Abstract

mElectrostatic potential maps of certain biologically important molecules (guanine, adenine, cytosine, thymine, and two conformers of glycine) were studied employing a "hybridization displacement charge (HDC)" correction to Lowdin charge distributions and using the conventional Mulliken charge distributions of the molecules. In these calculations, the magnitude of each of the point charges was distributed in 3-dimension in a spherically symmetric manner. The method of computing HDC using MNDO wave functions was optimized by introducing two adjustable parameters. It has been clearly demonstrated that HDC-corrected Lowdin charge distributions of the molecules mentioned above are able to reproduce most of the important features of their ab initio MEP maps, while the conventional Mulliken charge distributions fail in many respects. Thus, HDC-corrected Lowdin charge distributions are shown to be quite reliable for the study of molecular electrostatic properties, particularly for molecules with more than one competing electrophilic site. 0 1996 John Wiley & Sons, Inc.properties and function. Some examples of this type are drug-receptor interaction, substrateenzyme interaction, antigen-antibody interaction, and harmone-receptor interaction [ 1-61. Moleculectrostatic interactions of molecules, e.g., hylar electrostatic potentials (MEP) and electric fields (MEF) have been found to be quite useful for studying such problems and for obtaining structure-activity relationships (SARs) [7-lo]. It is

A comparison between experimental and theoretical aspherical-atom scattering factors for charge-density refinement of large molecules

“…As most experimental charge-density analyses of peptides (Pichon-Pesme et al, 2000; lead to a negative potential of approximately À0.3 e A Ê À1 around the carbonyl O atom, the experimental values clearly reproduce the peptide environment on average. On the other hand, the theoretical potentials obtained for molecules in vacuo are similar for the KVC database and in a semi-empirical molecular-orbital calculation (Gopi Mohan et al, 1996) around O C oxygen atoms in thymine and glycine molecules (À0.15 and À0.18 e A Ê À1 , respectively).…”

Relationship of hydrogen bonding energy with electrostatic and polarization energies and molecular electrostatic potentials for amino acids: An evaluation of the lock and key model

“…The AM1 method 22 was used to optimize molecular geometries and compute hydrogen bonding interaction energies and charge distributions including HDC. The method of computing HDC has been described in the literature 20, 23, 27, and so is not repeated here. During an interaction of two molecules A and B via hydrogen bonding, three different important interaction energy terms would be involved which may be defined as follows:…”

“…Therefore, study of hydrogen bonding in relation to the amino acids which constitute proteins and enzymes is of great importance. The available experimental and theoretical results suggest that hydrogen bonding mainly involves electrostatic interactions, and molecular electrostatic potentials (MEP) and molecular electric fields (MEF) serve as good descriptors of the same 7–20. The various approximate methods of computing MEP and their usefulness in relation to the different physical and chemical properties have been discussed in the literature 16–18.…”

“…The important question as to what extent and under which circumstances MEP can be used as a reliable descriptor of hydrogen bonding with amino acids also needs to be addressed in depth using a suitable theoretical tool. It has recently been shown that using hybridization displacement charges (HDC) combined with Löwdin charges computed using the AM1 method 22, one can obtain near ab initio quality MEP maps 20, 23. The AM1 method usually, though not always, provides a satisfactory description of hydrogen bonding 24, 25, and the HDC model within the framework of the AM1 method has been shown to reproduce near ab initio quality MEP maps for a variety of molecules 20 including the amino acids 26.…”