scholarly journals Effective intermediate-spin iron in O2-transporting heme proteins

2017 ◽  
Vol 114 (32) ◽  
pp. 8556-8561 ◽  
Author(s):  
Nils Schuth ◽  
Stefan Mebs ◽  
Dennis Huwald ◽  
Pierre Wrzolek ◽  
Matthias Schwalbe ◽  
...  
Keyword(s):  
Density Functional ◽  
Line Emission ◽  
Emission Spectra ◽  
X Ray ◽  
Complete Active Space ◽  
Intermediate Spin ◽  
Self Consistent Field ◽  
Classical Models ◽  
Heme Cofactor ◽  
Iron Center

Proteins carrying an iron-porphyrin (heme) cofactor are essential for biological O2 management. The nature of Fe-O2 bonding in hemoproteins is debated for decades. We used energy-sampling and rapid-scan X-ray Kβ emission and K-edge absorption spectroscopy as well as quantum chemistry to determine molecular and electronic structures of unligated (deoxy), CO-inhibited (carboxy), and O2-bound (oxy) hemes in myoglobin (MB) and hemoglobin (HB) solutions and in porphyrin compounds at 20–260 K. Similar metrical and spectral features revealed analogous heme sites in MB and HB and the absence of low-spin (LS) to high-spin (HS) conversion. Amplitudes of Kβ main-line emission spectra were directly related to the formal unpaired Fe(d) spin count, indicating HS Fe(II) in deoxy and LS Fe(II) in carboxy. For oxy, two unpaired Fe(d) spins and, thus by definition, an intermediate-spin iron center, were revealed by our static and kinetic X-ray data, as supported by (time-dependent) density functional theory and complete-active-space self-consistent-field calculations. The emerging Fe-O2 bonding situation includes in essence a ferrous iron center, minor superoxide character of the noninnocent ligand, significant double-bond properties of the interaction, and three-center electron delocalization as in ozone. It resolves the apparently contradictory classical models of Pauling, Weiss, and McClure/Goddard into a unifying view of O2 bonding, tuned toward reversible oxygen transport.

A THEORETICAL STUDY ON DUAL FLUORESCENCE OF 4-DIMETHYLAMINOPYRIDINE BY POLARIZABLE CONTINUUM MODEL

2008 ◽  
Vol 07 (04) ◽  
pp. 821-832 ◽  
Author(s):  
JUAN-QIN LI ◽  
XIANG-YUAN LI ◽  
FENG WANG
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Emission Spectra ◽  
Polarizable Continuum Model ◽  
Transfer Model ◽  
Dual Fluorescence ◽  
Field Methods ◽  
Complete Active Space ◽  
Self Consistent Field

Dual fluorescence spectra of 4-dimethylaminopyridine (DMAP) is investigated using time-dependent density functional theory and complete active space self-consistent field methods. Electronic absorption and emission spectra of DMAP have been investigated in three solvents, that is, cyclohexane, chloroform, and acetonitrile. The present study reveals that the dual fluorescence phenomena of DMAP appear in the cases of acetonitrile and chloroform, but not in cyclohexane. The electronic structures of the ground state and the intramolecular charge transfer states are, therefore, studied in order to reveal the insight of dual fluorescence. Our theoretical results suggest that the twisting of dimethylamino moiety in DMAP is necessary for the intramolecular charge transfer. The mechanism of the dual fluorescence of DMAP is discussed based on the twisted intramolecular charge transfer model and the dual fluorescence phenomenon is explained theoretically.

Self-Consistent Field Calculations of X-Ray Emission Spectra of Surface Adsorbates and Polymers

1997 ◽  
Vol 7 (C2) ◽  
pp. C2-515-C2-516
Author(s):  
H. Agren ◽  
L. G.M. Pettersson ◽  
V. Carravetta ◽  
Y. Luo ◽  
L. Yang ◽  
...  
Keyword(s):  
Emission Spectra ◽  
X Ray ◽  
Consistent Field ◽  
Self Consistent ◽  
Surface Adsorbates ◽  
Self Consistent Field

scholarly journals Redox-Active Dysprosium Single-Molecule Magnet: Spectro-Electrochemistry and Theoretical Investigations

2019 ◽  
Vol 5 (3) ◽  
pp. 46 ◽  
Author(s):  
Guglielmo Fernandez Garcia ◽  
Vincent Montigaud ◽  
Lucie Norel ◽  
Olivier Cador ◽  
Boris Le Guennic ◽  
...  
Keyword(s):  
Single Molecule ◽  
Density Functional ◽  
Functional Theory ◽  
Single Molecule Magnet ◽  
Complete Active Space ◽  
Consistent Field ◽  
Redox Active ◽  
Theoretical Investigations ◽  
Td Dft ◽  
Self Consistent Field

The mononuclear single-molecule magnet (SMM) [Dy(tta)3(L)]⋅C6H14 (1) (where tta− = 2-thenoyltrifluoroacetonate and L = 4,5-bis(propylthio)-tetrathiafulvalene-2-(2-pyridyl)benzimidazole-methyl-2-pyridine) was studied by spectro-electrochemistry. The resulting electronic spectra of the three oxidation states 1, 1+∙, and 12+ were rationalized by time-dependent density functional theory (TD-DFT) calculations starting from the DFT optimized structures. The modulation of the magnetic anisotropy of the DyIII center upon oxidation was also inspected at the Complete Active Space Self-Consistent Field (CASSCF) level of calculation.

Complete active space self‐consistent field and density functional study of FNO

1994 ◽  
Vol 100 (1) ◽  
pp. 459-463 ◽  
Author(s):  
Theodore S. Dibble ◽  
Joseph S. Francisco ◽  
Robert J. Deeth ◽  
Michael R. Hand ◽  
Ian H. Williams
Keyword(s):  
Density Functional ◽  
Functional Study ◽  
Density Functional Study ◽  
Complete Active Space ◽  
Active Space ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field

scholarly journals Formation of the X-ray line emission spectrum of excimer laser-produced plasmas

1998 ◽  
Vol 16 (1) ◽  
pp. 61-70 ◽  
Author(s):  
A. Magunov ◽  
A. Faenov ◽  
I. Skobelev ◽  
T. Pikuz ◽  
D. Batani ◽  
...  
Keyword(s):  
Experimental Data ◽  
Laser Radiation ◽  
Laser Pulse ◽  
Emission Spectrum ◽  
Pulse Train ◽  
Line Emission ◽  
Emission Spectra ◽  
Theoretical Modelling ◽  
Xecl Laser ◽  
X Ray

Time- and space-integrated emission spectra measurements have been performed in plasma produced by 308 nm wavelength XeCl laser radiation (IL = (4–10)·1012 W/cm2, τ = 10 ns) and by 248 nm wavelength KrF laser pulse train radiation (IL = 5·1015 W/cm2, τ = 7 ps, 16 pulses in train) on CF2 plane target. Theoretical modelling of Lyman series and He-like ion resonance series of fluorine and its fit of experimental data show considerable differences in the absorption of laser radiation in the two plasmas.

scholarly journals A multiconfigurational approach to the electronic structure of trichromium extended metal atom chains

2017 ◽  
Vol 46 (19) ◽  
pp. 6202-6211 ◽  
Author(s):  
M. Spivak ◽  
V. Arcisauskaite ◽  
X. López ◽  
J. E. McGrady ◽  
C. de Graaf
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Metal Atom ◽  
Density Functional ◽  
Functional Theory ◽  
Complete Active Space ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Capping Ligands

Density functional theory, Complete Active Space Self-Consistent Field (CASSCF) and perturbation theory (CASPT2) methodologies have been used to explore the electronic structure of a series of trichromium Extended Metal Atom Chains (EMACS) with different capping ligands.

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