Journal ArticleDOI
Resonance Raman studies of carbon monoxide binding to iron "picket fence" porphyrin with unhindered and hindered axial bases. An inverse relationship between binding affinity and the strength of iron-carbon bond.
Reads0
Chats0
TLDR
Comparisons of sterically hindered (1,2-Me2Im) and unhindered (N-MeIm) bases are of particular interest because of their implication in the phenomenon of hemoglobin cooperativity and the mechanisms of protein control of heme reactivity.Abstract:
The stretching frequency of the iron-carbon bond, v(Fe-CO), is a direct measure of the iron-carbon bond strength when there is no change in the Fe-C-O geometry. Here we report resonance Raman detection of v(Fe-CO) frequencies in the CO complexes of iron (II) alpha, alpha, alpha, alpha-mesotetrakis(o-pivalamidophenyl)porphyrin, FeII(TpivPP), with trans ligands of varying strength: N-methylimidazole (N-MeIm), 1,2-dimethylimidazole (1,2-Me2Im), pyridine (py), and tetrahydrofuran (THF). It was found that the weaker the iron-trans ligand bond, the stronger the iron-carbon bond. Comparisons of sterically hindered (1,2-Me2Im) and unhindered (N-MeIm) bases are of particular interest because of their implication in the phenomenon of hemoglobin cooperativity and the mechanisms of protein control of heme reactivity. While the CO binding affinity of FeII(TpivPP)(1,2-MeIm) is approximately 400 times lower than that of FeII(TpivPP)(N-MeIm), the v(Fe-CO) frequency for the former (at 496 cm-1) is higher than that for the latter (at 489 cm-1). This example shows that the CO binding affinity cannot be directly correlated with the strength of the iron-carbon bond. Comparison of the CO binding to FeII(TpivPP)(THF) and FeII(TpivPP)(N-MeIm) reveals a similar relationship; the v(Fe-CO) frequency (at 527 cm-1) in FeII(TpivPP)(THF)(CO) is 38 cm-1 higher than that in FeII(TpivPP)(N-MeIm)(CO), but the CO binding affinity is lower for the THF complex.read more
Citations
More filters
Book ChapterDOI
Use of chemical shifts in macromolecular structure determination.
David S. Wishart,David A. Case +1 more
Journal ArticleDOI
Cooperative CO2-to-ethanol conversion via enriched intermediates at molecule–metal catalyst interfaces
Fengwang Li,Yuguang C. Li,Ziyun Wang,Jun Li,Dae-Hyun Nam,Yanwei Lum,Mingchuan Luo,Xue Wang,Adnan Ozden,Sung Fu Hung,Bin Chen,Yuhang Wang,Joshua Wicks,Yi Xu,Yilin Li,Christine M. Gabardo,Cao-Thang Dinh,Ying Wang,Tao Tao Zhuang,David Sinton,Edward H. Sargent +20 more
TL;DR: Sargent et al. as discussed by the authors proposed a cooperative catalyst design of molecule-metal interfaces with the goal of producing a reaction-intermediate-rich local environment, which improves the electrosynthesis of ethanol from CO2 and H2O.
Journal ArticleDOI
NMR structure determination of protein - ligand complexes by lanthanide labeling
TL;DR: It is shown how the combination of pseudocontact shifts induced by a site-specifically bound lanthanide ion and prior knowledge of the 3D structure of the Lanthanide-labeled protein can be used to achieve rapid assignments of NMR spectra.
Journal ArticleDOI
Determinants of the FeXO (X = C, N, O) Vibrational Frequencies in Heme Adducts from Experiment and Density Functional Theory
TL;DR: In this paper, the resonance Raman spectra of all three classes of adducts, combining literature values with new data for FeIINO porphyrins having both electron-donating and electron-withdrawing substituents, were examined.
Journal ArticleDOI
Magnetic susceptibility tensor anisotropies for a lanthanide ion series in a fixed protein matrix.
TL;DR: This set of reliable magnetic data permits an experimental assessment of Bleaney's theory relative to the magnetic properties for an extended series of lanthanide complexes in solution as well as in excellent qualitative agreement with the observed pattern of axial anisotropies.
References
More filters
Journal ArticleDOI
Stereochemistry of cooperative effects in haemoglobin.
TL;DR: The oxygenation of haemoglobin is accompanied by structural changes in the subunits triggered by shifts of the iron atoms relative to the porphyrin and, in the β-subunits, also by the steric effect of oxygen itself.
Journal ArticleDOI
"Picket fence porphyrins." Synthetic models for oxygen binding hemoproteins.
James P. Collman,Robert R. Gagne,Christopher A. Reed,Thomas R. Halbert,George Lang,Ward T. Robinson +5 more
Journal ArticleDOI
Structure of erythrocruorin in different ligand states refined at 1.4 A resolution.
Wolfgang Steigemann,Ernst Weber +1 more
TL;DR: Spin state changes seem to have little influence on the porphyrin stereochemistry; it is determined primarily by the chemical properties of the ligand and its interaction with the haem and the globin.
Journal ArticleDOI
Nature of O2 and CO binding to metalloporphyrins and heme proteins.
TL;DR: The O2 vibration of dioxygen adducts of Fe and Co model complexes of alpha,alpha, alpha, alpha-tetrapivalamidophenylporphyrin ("picket fence" porphyrin, TpivPP) with 1-methylimidrazole and 1-tritylimidazole as axial bases are reported.
Related Papers (5)
Is bound carbonyl linear or bent in heme proteins? Evidence from resonance Raman and infrared spectroscopic data.
Xiaoyuan Li,Thomas G. Spiro +1 more