| 1. |
- Paul, Jan, et al.
(författare)
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Spin and electron distributions in heme-cyanide models and hemeproteins
- 1985
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Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology. - : Elsevier BV. - 0167-4838 .- 1879-2588. ; 832:3, s. 265-273
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Tidskriftsartikel (refereegranskat)abstract
- Proton NMR spectra of low-spin Fe(III) cyanoprotoheme as prosthetic group in a number of proteins are presented. The diagonally positioned 1-, 5- and 3-, 8-methyl groups obey shifts proportional to the Fe(III)/(II) reduction potential Em7, which indicates a pseudo-contact interaction. The correlation with Em7 is understandable if one postulates an enhanced rhombic distortion, dominating the Fe-methyl dipolar interactions. Hatree-Fock-Slater quantum chemical calculations show no significant changes of spin density as a function of the Fe-L5 distance, except at the iron atom and predominantly in the 3dxz and 3dyz orbitals. 4p orbitals, on the other hand, uphold most of the changes of electron density. We also observe a principal difference in the amino acid sequences in the heme-accommodating pocket of oxygen carriers and two-electron transmitters.
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| 2. |
- Paul, Jan, et al.
(författare)
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The vibrational bands of carbon monoxide bound to hemes or metal surfaces
- 1985
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Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology. - : Elsevier BV. - 0167-4838 .- 1879-2588. ; 832:3, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Infrared spectra of imidazole carbonyl complexes of 2,4-substituted hemes are presented. An increased CO stretch frequency is accompanied by a lowered FeC vibrational energy. Hartree-Fock-Slater electron structure calculations discern π and σ contributions to the observed shifts of vibrational energies. We conclude that an enhanced electron availability manifests itself as (i) a lowered ferric/ferrous reduction potential, (ii) increased filling of the 2π orbital of liganded CO which in turn reduces νCO and increases νFec, and (iii) increased basicity of the liganded CO. Analogies between CO liganded to heme and CO adsorbed onto metal surfaces are discussed.
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| 3. |
- Lindgren, S.Å., et al.
(författare)
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Sodium induced structure in UPS spectra of Cu(111)/Na
- 1985
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 155:1, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- UPS Spectra of sodium monolayers evaporated onto Cu(111) are presented. We interpret sodium induced structure below the Cu d-band as due to photoemitted 3d electrons which have experienced an energy loss by exciting a sodium monolayer plasmon. An experimental difficulty is that even small amounts (<1/10 monolayers) of water contamination produces structure in the same energy range. This emission is due to the OH 1π orbital. Hydroxide groups may also origin from the alkali source if this is operated at too elevated temperatures.
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| 4. |
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