Iron-carbon bond lengths in carbonmonoxy and cyanomet complexes of the monomeric hemoglobin III from Chironomus thummi thummi: a critical comparison between resonance Raman and x-ray diffraction studies.

Yu, Nai‐Teng; Benko, Bojan; Kerr, Ellen A.; Gersonde, Klaus

doi:10.1073/pnas.81.16.5106

Cited by 52 publications

(48 citation statements)

References 29 publications

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“…('3C'5N). This line at 447 cm-' is very close to the 453-cm-' line in cyanomet insect hemoglobin CTT III, which has been assigned by Yu et al (24) as the Fe-CN stretching vibration. The results of our normal coordinate calculations (28) support this assignment.…”

Section: Methodssupporting

confidence: 76%

“…It is of interest to note that the Fe"'-C-N bending mode of cyanomet CTT III (24) has been detected at -410 cm'; yet the Fe"'-C-N linkage is essentially linear as indicated by the identical Fe-CN stretching frequencies for the '3C'4N and '2C'5N isotopes at 450 cm-'. The Fe"'-C-N bending mode has also been reported in cyanomet complexes of deuteroheme IX-substituted CTT IV (25) and mesoheme IX-substituted CTT IV (25), where the Fe-C-N linkage are linear.…”

Section: Discussionmentioning

confidence: 99%

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Resonance Raman studies of sterically hindered cyanomet "strapped" hemes. Effects of ligand distortion and base tension on iron-carbon bond

Tanaka

Chang

1987

Biophysical Journal

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We report resonance Raman studies of the iron-carbon bond stretching vibrations, nu(Fe-CN), in sterically hindered and unhindered heme (FeIII)-CN- complexes. The sterically hindred "strapped hemes" are equipped with a covalently linked 13-, 14-, or 15-atom hydrocarbon chain across one face of the heme; these are called FeSP-13, FeSP-14, and FeSP-15, respectively. These straps would presumably exert a sideway shearing strain to force the linear ligands (e.g., CN- and CO) to be tilted and/or bent. The shorter the chain length, the weaker the ligand binding affinity because of a greater steric hindrance. This study reveals that the nu(Fe-CN) frequency decreases as the chain length is decreased, in contrast with the CO complexes, where the nu(Fe-CO) frequency increases as the chain length is decreased. For the heme-CN- complexes (with N-methylimidazole as a base), the nu(Fe-CN) frequencies are: heme 5 (unhindered), 451 cm-1; FeSP-15, 447 cm-1; FeSP-14, 447 cm-1; FeSP-13, 445 cm-1. For the heme-CO complexes (with N-methylimidazole as a base), the nu(Fe-CO) frequencies are: heme 5, 495 cm-1; FeSP-15, 509 cm-1; FeSP-14, 512 cm-1; FeSP-13, 514 cm-1 (Yu, N.-T., E. A. Kerr, B. Ward, and C. K. Chang, 1983, Biochemistry, 22:4534-4540). We have also studied the cyanide complexes with three different bases (pyridine, N-methylimidazole and 1,2-dimethylimidazole), and found that the trans-effect of cyanide complex is different from that of CO complexes. The tension on Fe"'-base bond weakens the Fe"'-CN- bond, whereas the tension on Fe"-base bond strengthens the Fe"-CO bond. The origin of these differences may be attributed to different extents of the d7r(Fe)- wr*(ligand) back bonding between the CN- and CO heme complexes. The Fe-C-N bending vibrations in these cyanomet strapped hemes are not resonance-enhanced, although this bending mode has been detected at -410 cm-' via Soret excitation in cyanometinsect hemoglobins. It is suggested that the orientation of the tilted Fe-C-N unit may be important in determining the overlap between CN and porphyrin 7r* orbitals, which provide coupling of the Fe-C-N bending mode with the resonant Soret (r-7r*) transition.

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Section: Methodssupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Resonance Raman studies of sterically hindered cyanomet "strapped" hemes. Effects of ligand distortion and base tension on iron-carbon bond

Tanaka

Chang

1987

Biophysical Journal

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“…The direction of tilt for the -z axis coincides approximately with the direction of the off-axis placement of the N atom of the bound cyanide in the crystal structure [ll], suggesting some correlation between these observations. While the Fe-CN unit is reported as bent rather than tilted in the cyanomet HbIII crystal structure [ll], detailed analysis of isotope effects on resonance Raman spectra for the Fe-CN unit in solution have challenged the accuracy of the crystal data [38]. The potential for a direct correlation between the tilt of the major magnetic axis and the Fe-CN unit is being explored in a variety of cyanomet Mbs [18, 19, 351. Comparison of solution and crystal structures of C. thummi thummi HbIII.…”

Section: Discussionmentioning

confidence: 99%

Solution ¹H‐NMR Structure of the Heme Cavity in the Low‐Affinity State for the Allosteric Monomeric Cyano‐Met Hemoglobins from Chironomus thummi thummi

Zhang¹,

Mar²,

Gersonde³

1996

European Journal of Biochemistry

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Solution 1H‐NMR studies of the heme cavity were performed for the cyanomet complexes of monomeric hemoglobins III and IV from the insect Chironomus thummi thummi, each of which exhibit marked Bohr effects. The low pH 5, paramagnetic (S= 1/2) derivatives were selected for study because the large dipolar shifts provide improved resolution over diamagnetic forms and allow distinction between the two isomeric heme orientations [Peyton, D. H., La Mar, G. N. & Gersonde, K. (1988) Biochim. Biophys. Acta 954, 82–94]. The crystal structure for the low‐pH form of the hemoglobin III derivative, moreover, has been reported and showed that the functionally implicated distal His58 side chain adopts alternative orientations, either in or out of the pocket [Steigemann, W. & Weber, E. (1979) J. Mol. Biol. 127, 309–338]. All heme pocket residues for the low‐pH forms of the two hemoglobins were located, at least in part, and positioned in the heme cavity on the basis of nuclear Overhauser effects to the heme and each other, dipolar shifts, and paramagnetic‐induced relaxation. The resulting structure yielded the orientation of the major axis of the paramagnetic susceptibility tensor. The heme pocket structure of the cyanomet hemoglobins III and IV were found to be indistinguishable, with both exhibiting a distal His58 oriented solely into the heme cavity and in contact with the ligand, and with two residues, Phe100 and Phe38, exhibiting small but significant displacements in solution relative to hemoglobin III in the crystal.

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“…In the Fe N, stretching mode, all the atoms in the imidazole ring move more or less in-phase; the v(Fe NE) frequency depends on the effective mass of the imidazole. This is analogous to the Fe-C O moiety, where the v(Fe C) stretching frequency increases as the Fe C O bond angle decrease (23,24). This is because the effective mass of CO for Fe C stretching vibration decreases as the Fe-C-O bond angle decreases.…”

Section: Deoxy Heminsmentioning

confidence: 96%

Resonance Raman studies of dioxygen and carbon monoxide binding to imidazole-appended hemes

Yu¹,

Thompson²,

Chang³

1987

Biophysical Journal

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Resonance Raman spectroscopy has been employed to probe the effects of proximal base strain on the bonding of O2 and CO in three synthetic hemins with covalently linked imidazole ligands. The strain is introduced by varying the length of the imidazole-containing side chain and by restricting the side chain flexibility with a phenyl ring. These hemins are abbreviated as "long," "short," and "stiff" hemins, respectively. In the deoxy state, the iron-imidazole stretching frequencies [nu(Fe--N epsilon)] for long, short, and stiff hemins are detected at 200, 207, and 204 cm-1, respectively. The strain induced in the iron-imidazole bond by the short hemin results in a higher nu(Fe--N epsilon) frequency, in contrast to the strain induced by sterically hindered 2-methylimidazole or 1,2-dimethylimidazole complexes in which the Fe--N epsilon bond is tilted and lengthened, but the imidazole ring remains perpendicular to the heme plane. However, in the short hemin, the plane of the imidazole ring may not be perpendicular to the plane of the porphyrin, altering the amount of pi-interaction (hence the strength of Fe--N epsilon bond) and the nature of normal mode containing Fe--N epsilon bond stretching. Upon CO binding, we have observed the nu(Fe--CO) stretching frequencies at 497 (long), 499 (short), and 496 cm-1 (stiff), somewhat lower than those reported by Mitchell et al. (Inorg. Chem., 1985, 24:967) for the chelated-heme X CO complexes (i.e., 501-506 cm-1). This is the first report of an iron-oxygen-associated vibration observed in solution for an unprotected heme. The oxy complexes were formed by introducing dioxygen to the deoxy complexes at -700C. The isotope-sensitive line was detected at 576 cm- (1602) in oxy stiff hemin, which was shifted to 545 cm-1 upon 1802 substitution. This is perhaps the largest isotope shift (31 cm-') observed to date, compared with the usual 22-24 cm-'.For the long and short hemins, the iron-oxygen-associated vibration was detected at 574 and 573 cm-', respectively.These values are very similar to those observed(N-methylimidazole) and myoglobin/hemoglobin.

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Iron-carbon bond lengths in carbonmonoxy and cyanomet complexes of the monomeric hemoglobin III from Chironomus thummi thummi: a critical comparison between resonance Raman and x-ray diffraction studies.

Cited by 52 publications

References 29 publications

Resonance Raman studies of sterically hindered cyanomet "strapped" hemes. Effects of ligand distortion and base tension on iron-carbon bond

Resonance Raman studies of sterically hindered cyanomet "strapped" hemes. Effects of ligand distortion and base tension on iron-carbon bond

Solution ¹H‐NMR Structure of the Heme Cavity in the Low‐Affinity State for the Allosteric Monomeric Cyano‐Met Hemoglobins from Chironomus thummi thummi

Resonance Raman studies of dioxygen and carbon monoxide binding to imidazole-appended hemes

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Iron-carbon bond lengths in carbonmonoxy and cyanomet complexes of the monomeric hemoglobin III from Chironomus thummi thummi: a critical comparison between resonance Raman and x-ray diffraction studies.

Cited by 52 publications

References 29 publications

Resonance Raman studies of sterically hindered cyanomet "strapped" hemes. Effects of ligand distortion and base tension on iron-carbon bond

Resonance Raman studies of sterically hindered cyanomet "strapped" hemes. Effects of ligand distortion and base tension on iron-carbon bond

Solution 1H‐NMR Structure of the Heme Cavity in the Low‐Affinity State for the Allosteric Monomeric Cyano‐Met Hemoglobins from Chironomus thummi thummi

Resonance Raman studies of dioxygen and carbon monoxide binding to imidazole-appended hemes

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Solution ¹H‐NMR Structure of the Heme Cavity in the Low‐Affinity State for the Allosteric Monomeric Cyano‐Met Hemoglobins from Chironomus thummi thummi