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Title: Chiral Three-Dimensional Microporous Nickel Aspartate with Extended Ni-O-Ni Bonding

Abstract

In the course of our investigation aimed at the preparation of homochiral coordination polymers using readily available in optically pure form ligands and building blocks of condensed metal polyhedra, we recently reported a one-dimensional nickel aspartate compound [Ni{sub 2}O(L-Asp)(H{sub 2}O){sub 2}]{center_dot}4H{sub 2}O (1) based on helical chains with extended Ni-O-Ni bonding. Here we report a new nickel aspartate [Ni{sub 2.5}(OH)(L-Asp){sub 2}]{center_dot}6.55H{sub 2}O (2) with a three-dimensional Ni-O-Ni connectivity that forms at a higher pH and is based on the same helices as in 1 which are connected by additional nickel octahedra to generate a chiral open framework with one-dimensional channels with minimum van der Waals dimensions of 8 x 5 Angstroms. The crystal structure of 2 was determined by synchrotron single-crystal X-ray diffraction on a 10 x 10 x 240 {micro}m crystal.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914039
Report Number(s):
BNL-78607-2007-JA
Journal ID: ISSN 0002-7863; JACSAT; TRN: US0801494
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Am. Chem. Soc.; Journal Volume: 128
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 36 MATERIALS SCIENCE; BONDING; CHAINS; CRYSTAL STRUCTURE; DIMENSIONS; NICKEL; POLYMERS; SYNCHROTRONS; X-RAY DIFFRACTION; NSLS; national synchrotron light source

Citation Formats

Anokhina,E., Go, Y., Lee, Y., Vogt, T., and Jacobson, A. Chiral Three-Dimensional Microporous Nickel Aspartate with Extended Ni-O-Ni Bonding. United States: N. p., 2006. Web. doi:10.1021/ja062743b.
Anokhina,E., Go, Y., Lee, Y., Vogt, T., & Jacobson, A. Chiral Three-Dimensional Microporous Nickel Aspartate with Extended Ni-O-Ni Bonding. United States. doi:10.1021/ja062743b.
Anokhina,E., Go, Y., Lee, Y., Vogt, T., and Jacobson, A. Sun . "Chiral Three-Dimensional Microporous Nickel Aspartate with Extended Ni-O-Ni Bonding". United States. doi:10.1021/ja062743b.
@article{osti_914039,
title = {Chiral Three-Dimensional Microporous Nickel Aspartate with Extended Ni-O-Ni Bonding},
author = {Anokhina,E. and Go, Y. and Lee, Y. and Vogt, T. and Jacobson, A.},
abstractNote = {In the course of our investigation aimed at the preparation of homochiral coordination polymers using readily available in optically pure form ligands and building blocks of condensed metal polyhedra, we recently reported a one-dimensional nickel aspartate compound [Ni{sub 2}O(L-Asp)(H{sub 2}O){sub 2}]{center_dot}4H{sub 2}O (1) based on helical chains with extended Ni-O-Ni bonding. Here we report a new nickel aspartate [Ni{sub 2.5}(OH)(L-Asp){sub 2}]{center_dot}6.55H{sub 2}O (2) with a three-dimensional Ni-O-Ni connectivity that forms at a higher pH and is based on the same helices as in 1 which are connected by additional nickel octahedra to generate a chiral open framework with one-dimensional channels with minimum van der Waals dimensions of 8 x 5 Angstroms. The crystal structure of 2 was determined by synchrotron single-crystal X-ray diffraction on a 10 x 10 x 240 {micro}m crystal.},
doi = {10.1021/ja062743b},
journal = {J. Am. Chem. Soc.},
number = ,
volume = 128,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • We used pyridoxal 5'-phosphate (PLP) is a fundamental, multifunctional enzyme cofactor to catalyze a wide variety of chemical reactions involved in amino acid metabolism. PLP-dependent enzymes optimize specific chemical reactions by modulating the electronic states of PLP through distinct active site environments. In aspartate aminotransferase (AAT), an extended hydrogen bond network is coupled to the pyridinyl nitrogen of the PLP, influencing the electrophilicity of the cofactor. This network, which involves residues Asp-222, His-143, Thr-139, His-189, and structural waters, is located at the edge of PLP opposite the reactive Schiff base. We demonstrate that this hydrogen bond network directly influences themore » protonation state of the pyridine nitrogen of PLP, which affects the rates of catalysis. We analyzed perturbations caused by single- and double-mutant variants using steady-state kinetics, high resolution X-ray crystallography, and quantum chemical calculations. Protonation of the pyridinyl nitrogen to form a pyridinium cation induces electronic delocalization in the PLP, which correlates with the enhancement in catalytic rate in AAT. Therefore, PLP activation is controlled by the proximity of the pyridinyl nitrogen to the hydrogen bond microenvironment. Quantum chemical calculations indicate that Asp-222, which is directly coupled to the pyridinyl nitrogen, increases the pKa of the pyridine nitrogen and stabilizes the pyridinium cation. His-143 and His-189 also increase the pKa of the pyridine nitrogen but, more significantly, influence the position of the proton that resides between Asp-222 and the pyridinyl nitrogen. Our findings indicate that the second shell residues directly enhance the rate of catalysis in AAT.« less
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