TY  - JOUR
AU  - Galstyan, AS
AU  - Zarić, Snežana D.
AU  - Knapp, EW
PY  - 2005
UR  - https://cherry.chem.bg.ac.rs/handle/123456789/708
AB  - Density functional theory computations of heme with ionized propionic acid groups, axially coordinated with two imidazoles, were performed for different mutual orientations of the imidazole planes. Environmental influences from water or protein were considered with a continuum dielectric medium by solving the Poisson equation. In vacuum, optimized geometries yielded imidazole - heme conformations where the NH groups of imidazoles are oriented toward the heme propionic groups in agreement with data from crystal structures of heme proteins. Conformational free-energy dependencies of the mutual orientation of axially ligated imidazoles calculated in protein ( epsilon = 10) and water (epsilon = 80) environments confirmed the vacuum results, albeit the energy difference between the preferred and the 180 degrees opposite orientations of the imidazole ligand decreased from 3.84 kcal/mol in vacuum to 2.35 and 2.40 kcal/mol in protein and water, respectively. Two main factors determine the imidazole orientation: ( 1) the direct intramolecular electrostatic interactions of propionic groups with the polar NH groups of imidazole and ( 2) the electrostatic interaction of the total dipole moment of the imidazole - heme complex with the reaction field. In vacuum, only the first type of interaction is present, while in a dielectric medium the latter effect becomes competitive at high dielectric constant, resulting in a decrease of the orientational preference. Interestingly, the orientational preference of the imidazole axially ligated to heme becomes even more pronounced, if the negatively charged propionates are neutralized by counter charges that mimic salt bridges or protonation of the propionates.
PB  - Springer, New York
T2  - Journal of Biological Inorganic Chemistry
T1  - Computational studies on imidazole heme conformations
VL  - 10
IS  - 4
SP  - 343
EP  - 354
DO  - 10.1007/s00775-005-0642-8
ER  - 

@article{
author = "Galstyan, AS and Zarić, Snežana D. and Knapp, EW",
year = "2005",
abstract = "Density functional theory computations of heme with ionized propionic acid groups, axially coordinated with two imidazoles, were performed for different mutual orientations of the imidazole planes. Environmental influences from water or protein were considered with a continuum dielectric medium by solving the Poisson equation. In vacuum, optimized geometries yielded imidazole - heme conformations where the NH groups of imidazoles are oriented toward the heme propionic groups in agreement with data from crystal structures of heme proteins. Conformational free-energy dependencies of the mutual orientation of axially ligated imidazoles calculated in protein ( epsilon = 10) and water (epsilon = 80) environments confirmed the vacuum results, albeit the energy difference between the preferred and the 180 degrees opposite orientations of the imidazole ligand decreased from 3.84 kcal/mol in vacuum to 2.35 and 2.40 kcal/mol in protein and water, respectively. Two main factors determine the imidazole orientation: ( 1) the direct intramolecular electrostatic interactions of propionic groups with the polar NH groups of imidazole and ( 2) the electrostatic interaction of the total dipole moment of the imidazole - heme complex with the reaction field. In vacuum, only the first type of interaction is present, while in a dielectric medium the latter effect becomes competitive at high dielectric constant, resulting in a decrease of the orientational preference. Interestingly, the orientational preference of the imidazole axially ligated to heme becomes even more pronounced, if the negatively charged propionates are neutralized by counter charges that mimic salt bridges or protonation of the propionates.",
publisher = "Springer, New York",
journal = "Journal of Biological Inorganic Chemistry",
title = "Computational studies on imidazole heme conformations",
volume = "10",
number = "4",
pages = "343-354",
doi = "10.1007/s00775-005-0642-8"
}

Galstyan, A., Zarić, S. D.,& Knapp, E.. (2005). Computational studies on imidazole heme conformations. in Journal of Biological Inorganic Chemistry
Springer, New York., 10(4), 343-354.
https://doi.org/10.1007/s00775-005-0642-8

Galstyan A, Zarić SD, Knapp E. Computational studies on imidazole heme conformations. in Journal of Biological Inorganic Chemistry. 2005;10(4):343-354.
doi:10.1007/s00775-005-0642-8 .

Galstyan, AS, Zarić, Snežana D., Knapp, EW, "Computational studies on imidazole heme conformations" in Journal of Biological Inorganic Chemistry, 10, no. 4 (2005):343-354,
https://doi.org/10.1007/s00775-005-0642-8 . .

TY  - JOUR
AU  - Han, LQ
AU  - Du, JL
AU  - Yang, HJ
AU  - Wang, HG
AU  - Leng, XB
AU  - Galstyan, A
AU  - Zarić, Snežana D.
AU  - Sun, WH
PY  - 2003
UR  - https://cherry.chem.bg.ac.rs/handle/123456789/533
AB  - Crystal structure of novel bis(imino)phenoxychloro-iron(III) chloride demonstrated a columnar helix through hydrogen bonding of anion-cation molecules and intermolecular pi-pi interactions, along with the syntheses and characterization of the new compounds. A quantum-chemical single point calculations of the interaction energies were performed on the basis of the X-ray structural data. (C) 2002 Elsevier Science B.V. All rights reserved.
PB  - Elsevier Science Bv, Amsterdam
T2  - Inorganic Chemistry Communications
T1  - Crystal structure and modeling calculation of the columnar helix 2,6-Bis(imino)phenoxy iron(III) chloride
VL  - 6
IS  - 1
SP  - 5
EP  - 9
DO  - 10.1016/S1387-7003(02)00670-6
ER  - 

@article{
author = "Han, LQ and Du, JL and Yang, HJ and Wang, HG and Leng, XB and Galstyan, A and Zarić, Snežana D. and Sun, WH",
year = "2003",
abstract = "Crystal structure of novel bis(imino)phenoxychloro-iron(III) chloride demonstrated a columnar helix through hydrogen bonding of anion-cation molecules and intermolecular pi-pi interactions, along with the syntheses and characterization of the new compounds. A quantum-chemical single point calculations of the interaction energies were performed on the basis of the X-ray structural data. (C) 2002 Elsevier Science B.V. All rights reserved.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Inorganic Chemistry Communications",
title = "Crystal structure and modeling calculation of the columnar helix 2,6-Bis(imino)phenoxy iron(III) chloride",
volume = "6",
number = "1",
pages = "5-9",
doi = "10.1016/S1387-7003(02)00670-6"
}

Han, L., Du, J., Yang, H., Wang, H., Leng, X., Galstyan, A., Zarić, S. D.,& Sun, W.. (2003). Crystal structure and modeling calculation of the columnar helix 2,6-Bis(imino)phenoxy iron(III) chloride. in Inorganic Chemistry Communications
Elsevier Science Bv, Amsterdam., 6(1), 5-9.
https://doi.org/10.1016/S1387-7003(02)00670-6

Han L, Du J, Yang H, Wang H, Leng X, Galstyan A, Zarić SD, Sun W. Crystal structure and modeling calculation of the columnar helix 2,6-Bis(imino)phenoxy iron(III) chloride. in Inorganic Chemistry Communications. 2003;6(1):5-9.
doi:10.1016/S1387-7003(02)00670-6 .

Han, LQ, Du, JL, Yang, HJ, Wang, HG, Leng, XB, Galstyan, A, Zarić, Snežana D., Sun, WH, "Crystal structure and modeling calculation of the columnar helix 2,6-Bis(imino)phenoxy iron(III) chloride" in Inorganic Chemistry Communications, 6, no. 1 (2003):5-9,
https://doi.org/10.1016/S1387-7003(02)00670-6 . .