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Can the interaction density be measured? The example of the non-standard amino acid sarcosine

Can the interaction density be measured? The example of the non-standard amino acid sarcosine The experimental charge density (r) of the non-standard amino acid sarcosine has been determined based on an extensive and complete data set measured at 100 K to high resolution (sin / = 1.18 A-1) by single-crystal X-ray diffraction. Anisotropic thermal motion of the H atoms, obtained from TLS + ONIOM cluster methods, was included in the structural model. Based on the multipole-model geometry, the theoretical Hartree-Fock interaction density of a molecule in the crystal has been calculated with CRYSTAL98. It manifests itself in local rearrangements of (r) and can be reproduced with a multipole projection via simulated structure factors. An attempt has also been made to obtain the interaction density from a combination of experimental and theoretical charge densities using either a whole-molecular calculation or the invariom database. Agreement with the periodic Hartree-Fock interaction density is qualitative. It is shown that invarioms reproduce the features of the theoretical multipole-projected whole-molecular electron density, and can be used to approximate it. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Acta Crystallographica Section A: Foundations of Crystallography International Union of Crystallography

Can the interaction density be measured? The example of the non-standard amino acid sarcosine

Can the interaction density be measured? The example of the non-standard amino acid sarcosine


Abstract

The experimental charge density (r) of the non-standard amino acid sarcosine has been determined based on an extensive and complete data set measured at 100 K to high resolution (sin / = 1.18 A-1) by single-crystal X-ray diffraction. Anisotropic thermal motion of the H atoms, obtained from TLS + ONIOM cluster methods, was included in the structural model. Based on the multipole-model geometry, the theoretical Hartree-Fock interaction density of a molecule in the crystal has been calculated with CRYSTAL98. It manifests itself in local rearrangements of (r) and can be reproduced with a multipole projection via simulated structure factors. An attempt has also been made to obtain the interaction density from a combination of experimental and theoretical charge densities using either a whole-molecular calculation or the invariom database. Agreement with the periodic Hartree-Fock interaction density is qualitative. It is shown that invarioms reproduce the features of the theoretical multipole-projected whole-molecular electron density, and can be used to approximate it.

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References (38)

Publisher
International Union of Crystallography
Copyright
Copyright (c) 2007 International Union of Crystallography
Subject
crystal-field effect, interaction density, sarcosine
ISSN
0108-7673
eISSN
1600-5724
DOI
10.1107/S0108767307039116
pmid
17703077
Publisher site
See Article on Publisher Site

Abstract

The experimental charge density (r) of the non-standard amino acid sarcosine has been determined based on an extensive and complete data set measured at 100 K to high resolution (sin / = 1.18 A-1) by single-crystal X-ray diffraction. Anisotropic thermal motion of the H atoms, obtained from TLS + ONIOM cluster methods, was included in the structural model. Based on the multipole-model geometry, the theoretical Hartree-Fock interaction density of a molecule in the crystal has been calculated with CRYSTAL98. It manifests itself in local rearrangements of (r) and can be reproduced with a multipole projection via simulated structure factors. An attempt has also been made to obtain the interaction density from a combination of experimental and theoretical charge densities using either a whole-molecular calculation or the invariom database. Agreement with the periodic Hartree-Fock interaction density is qualitative. It is shown that invarioms reproduce the features of the theoretical multipole-projected whole-molecular electron density, and can be used to approximate it.

Journal

Acta Crystallographica Section A: Foundations of CrystallographyInternational Union of Crystallography

Published: Aug 17, 2007

Keywords: crystal-field effect ; interaction density ; sarcosine .

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