Low temperature infrared spectral study of iron(II) dioxygen complexes derived from a picket fence porphyrin

Collman, James P.; Gagné, Robert R.; Gray, Harry B.; Hare, Jeffrey W.

doi:10.1021/ja00827a050

Cited by 34 publications

(15 citation statements)

References 1 publication

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“…These results strongly support the MIn-02-formalism. The present data correct the preliminary report of an oxygen vibration at 1385 cm-' (3,13) which has since proved to be an artifact* (14). We are unaware of any previous reports of Po2 in model Fe and Co porphyrins.…”

supporting

confidence: 87%

Nature of O2 and CO binding to metalloporphyrins and heme proteins.

Collman¹,

Brauman²,

Halbert³

et al. 1976

Proc. Natl. Acad. Sci. U.S.A.

345

261

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The O2 vibration of dioxygen adducts of Fe and Co model complexes of a,a,ac,a-tetrapivalamidophenylporphyrin ("picket fence" porphyrin, TpivPP) with 1-methylimidazole and 1-tritylimidazole as axial bases are reported, obtained with difference techniques between 1'602,O180, 160-.80 A continuing controversy exists over the nature of ligand bonding to hemoproteins and metalloporphyrins. While it has been well established that both iron and cobalt bind dioxygen in a bent end-on fashion (1, 2), physical measurements (3-6) and theoretical calculations (7-10) have been used to support both the spin-paired dioxygen (M"1-02) (11) and the electron transfer superoxide (MIII-02-) (12) models. Here we present infrared data on dioxygen "picket-fence" porphyrin complexes of iron and cobalt. These results strongly support the MIn-02-formalism. The present data correct the preliminary report of an oxygen vibration at 1385 cm-' (3,13) which has since proved to be an artifact* (14). We are unaware of any previous reports of Po2 in model Fe and Co porphyrins. In addition, we discuss the nature of CO binding to ferrous porphyrins and the implication this has for the role of the apoprotein in biological oxygen carriers. It is our thesis that the distal binding site in hemoproteins functions to lower the carbon monoxide affinity.MATERIALS AND METHODS Benzene (spectroquality, Baker "Photrex") solutions of the "picket fence" porphyrin complexes (3, 14), FelImesotetra(a,a,a,a-o-pivalamidophenyl)porphyrinato (TpivPP) and Coll (aa,a,a-TpivPP), 17 mM and 19 mM containing 5 and 2 equivalents of 1-tritylimidazole (NTrIm), respectively, were Abbreviations: TpivPP, meso-tetra (a,a,a,a-o-pivalamidophenyl

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supporting

confidence: 87%

Nature of O2 and CO binding to metalloporphyrins and heme proteins.

Collman¹,

Brauman²,

Halbert³

et al. 1976

Proc. Natl. Acad. Sci. U.S.A.

345

261

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“…The determination of the exact nature of dioxygen binding to hemoglobin/myoglobin has been the subject of a considerable amount of research over the past few years (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13).…”

Section: Introductionmentioning

confidence: 99%

Resonance Raman Studies of Co—O2 and O—O Stretching Vibrations in Oxy-Cobalt Hemes

Mackin¹,

Tsubaki²,

Yu³

1983

Biophysical Journal

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Strong evidence suggests that the stretching vibration of the bound oxygen can be perturbed by an accidentally degenerate porphyrin ring mode, resulting in two split frequencies. In the Co(II)(TpivPP) (pyridine) (18)O(2) complex, we demonstrate that the nu((18)O-(18)O) mode, after being shifted from its nu((16)O-(16)O) value at 1,156 cm(-1), undergoes a resonance interaction with the 1,080 cm(-1) porphyrin mode, giving rise to two lines at 1,067 and 1,089 cm(-1). In the O(2) complex of Co(II) mesoporphyrin IX-substituted sperm whale myoglobin, we observed a dramatic intensity increase at 1,132 cm(-1) upon (16)O(2) --> (18)O(2) substitution, which is due to the reappearance of the 1,132-cm(-1) porphyrin mode after the removal of resonance conditions. A decrease in O(2) binding affinity, caused by the proximal base tension, corresponds to an increase in the Co-O(2) stretching frequency. The nu(Co-O(2)) at 527 cm(-1) for the low affinity Co(II)(TpivPP)(1,2-Me(2)Im) O(2) complex is 11 cm(-1) higher than the 516-cm(-1) value for the high affinity complex (with N-MeIm replacing 1,2-Me(2)Im). However, in the corresponding iron complexes the reverse behavior is observed, i.e., the nu(Fe-O(2)) decreases for the (1,2-Me(2)Im) complex. There is a 24-cm(-1) difference in the Co-O(2) stretching frequencies between Co(II)(TpivPP)(N-MeIm)O(2) (at 516 cm(-1)) and oxy meso CoMb (at 540 cm(-1)), suggesting a protein induced distortion of the Co-O-O linkage. However, the values for nu(Fe-O(2)) are nearly identical between Fe(II)(TpivPP)(N-MeIm)O(2) (at 571 cm(-1)) and oxy Mb (at 573 cm(-1)), indicating that O(2) binds to myoglobin in the same manner as in the sterically unhindered "picket fence" complex. Evidence is presented that suggests the presence of two dioxygen stretching frequencies due to two different conformers in each of the N-MeIm and 1,2-Me(2)Im complex of oxy Co(II)(TpivPP).

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“…The relatively short F e -0 distance in the complex is consistent with the relatively high F e -0 stretching frequency found in the 0 2Hb Ram an spectrum by Brunner (1974) and supports Pauling's (1964) suggestion of substantial multiple bonding (back-bonding) between low-spin Fe2+ and bound 0 2. Collman et al (1974) point out th a t the 1385 cm-1 0 -0 frequency is ca. 100 cm-1 lower than th a t of singlet 0 2, a decrease similar to th a t observed for CO on binding to Hb (Alben & Caughey 1968).…”

Section: ( D) Electron Distribution To Oxyhaemoglobinmentioning

confidence: 98%

“…Weiss pointed to the similarity of absorption spectra of 0 2Hb and low-spin methaemoglobin derivatives, and recently Barlow, Maxwell, Wallace & Caughey (1973) have reported the 0 2Hb 0 -0 stretching frequency a t 1104 cm-1, characteristic of superoxide ion, from 160 2-180 2 difference infrared spectra of packed red cells. On the other hand Collman, Gagne, Gray & Hare (1974) have reported an 0 -0 stretching frequency a t 1385 cm-1, again by using (low-temperature) 160 2-180 2 difference infrared spectroscopy, for a model haem -02 complex, whose X-ray structure shows a tilted 0 2 ligand, as in the 0 2Hb structure proposed by Pauling & Coryell (1936). The relatively short F e -0 distance in the complex is consistent with the relatively high F e -0 stretching frequency found in the 0 2Hb Ram an spectrum by Brunner (1974) and supports Pauling's (1964) suggestion of substantial multiple bonding (back-bonding) between low-spin Fe2+ and bound 0 2.…”

Section: ( D) Electron Distribution To Oxyhaemoglobinmentioning

confidence: 99%

Biological applications of resonance Raman spectroscopy: haem proteins

Spiro

1975

Proc. R. Soc. Lond. A

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Resonance Raman spectroscopy involves laser excitation within an absorption band of the sample. Certain vibrational modes, those which couple to the electronic transition, exhibit greatly increased Raman scattering in the resulting spectrum. Sensitivity approaches that of absorption spectrophotometry, while the high resolution characteristic of vibrational spectroscopy is preserved, even in solution at room temperature. If the resonant electronic transition is associated with a site of biological activity, then the technique offers a sensitive probe for structural features of the site. Haem proteins afford particularly informative resonance Raman spectra, with a rich assortment of porphyrin ring vibrations, which can be classified and analysed via their symmetry properties. Certain of these frequencies are sensitive to the structural concomitants of spin- and oxidation-state changes of the haem group. These can be used to monitor the structural consequences of ligation or electron transfer in haem proteins.

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Low temperature infrared spectral study of iron(II) dioxygen complexes derived from a picket fence porphyrin

Cited by 34 publications

References 1 publication

Nature of O2 and CO binding to metalloporphyrins and heme proteins.

Nature of O2 and CO binding to metalloporphyrins and heme proteins.

Resonance Raman Studies of Co—O2 and O—O Stretching Vibrations in Oxy-Cobalt Hemes

Biological applications of resonance Raman spectroscopy: haem proteins

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