Magnetic properties of oxyhemoglobin.

Cerdonio, M.; Congiu‐Castellano, A.; Mogno, F.; Pispisa, B.; Romani, Gian Luca; Vitale, S.

doi:10.1073/pnas.74.2.398

Cited by 82 publications

(40 citation statements)

References 14 publications

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“…Fully liganded human HbCO and HbO2 samples were frozen, by immersion in liquid nitrogen, and inserted in the precooled sample chamber of the susceptometer, and their susceptibility was measured at 190 K. We do not detect any difference between the oxy and carbonmonoxy samples, in contrast to the results of ref. 1. Taken all together the present data do not allow any low-lying triplet state with an energy less than 1100 cm-' above the singlet ground state.…”

mentioning

confidence: 57%

Reexamination of the evidence for paramagnetism in oxy- and carbonmonoxyhemoglobins.

Cerdonio¹,

Morante²,

Torresani³

et al. 1985

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

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Experiments have been carried out in an attempt to confirm previous reports of paramagnetism in the oxy-and carbonmonoxy derivatives of human and carp hemoglobin. When care is taken to ensure complete saturation of the hemoglobins with ligand and the diamagnetic contributions of all of the buffers are carefully evaluated, these hemoglobin derivatives are found to have the same gram susceptibilities as exhibited by a set of metal free proteins, suggesting that they are fully diamagnetic.In previous articles (1-5), we reported evidence of the existence of a paramagnetic contribution to the magnetic susceptibilities of the carbonmonoxy and oxy derivatives of human and carp hemoglobins. In response to the controversy surrounding our observations and the findings of others (6, 7), we have repeated the experiments with additional controls. We wish to report that there is no longer any reason to suspect that these derivatives are paramagnetic at room temperature. Using a few metal-free proteins we have been able to establish a diamagnetic reference for protein solutions. We find that the magnetic properties of oxy-and carbonmonoxyhemoglobins correspond to such a diamagnetic reference. This brings our observations into agreement with those of refs. 6 and 7.The methods of sample preparation, the instrumentation, the overall precision, and the data reduction were the same as in our most recent papers (see ref. 5). However, we took greater care to be certain that the hemoglobins were fully saturated with the ligand in the highly concentrated solutions used in those experiments. We did this after some observations of our own and discussions with Joe Savicki and George Lang aroused the suspicion that partial deoxygenation could have been the source of our previous findings. For every protein sample the diamagnetic contribution of the buffer was determined independently. These determinations led us to revise the values of the buffer corrections at high salt concentrations. Our results are shown in Fig. 1 Fig. 1. We obtain for the common Xg the value -(0.587 + 0.005) x 10-6 ml/g. We have also measured the susceptibilities of solutions of human HbO2 and HbCO and carp HbCO at high salt concentrations (-350 mM NaCl). The Xm. values for all of these derivatives fall, within error limits, on the same straight line when plotted as a function of molar heme concentration with the intercept at zero concentration equal to the solvent Xm., Using the same value for the partial volume of Hb as that used for the low-ionic- strength results, we calculate XHb to be -(0.593 + 0.006) x 10-6 ml/g. It is evident that no significant difference exists between XHb at low and high salt concentrations. This value is consistent with our earlier results obtained with human HbCO at low salt concentrations but not with the results we reported for this derivative at high ionic strength in ref. 3. Finally, we have also redone our studies in the frozen state. Fully liganded human HbCO and HbO2 samples were frozen, by immersion in liquid nitrogen, and...

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mentioning

confidence: 57%

Reexamination of the evidence for paramagnetism in oxy- and carbonmonoxyhemoglobins.

Cerdonio¹,

Morante²,

Torresani³

et al. 1985

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

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“…These values, being close to those of free superoxide ions (1100-1150 cm-'), have been taken as evidence of a substantial transfer of electron density from the iron (or cobalt) to the coordinated oxygen. The charge-transfer formulation of Fe(IJI)-02-or Co (III)-02 has, in fact, been proposed by many investigators (2,5,7,(11)(12)(13)(14), although there is not necessarily a transfer ofan electron from Fe (or Co) to 02 upon binding (4,15,16). The picture of single v(0-0) vibration is complicated by the discovery of an additional infrared band at 1156 cm-' in oxyHbA (17) after Collman et al (13) stretch at =570 cm-1 (originally reported at 567 cm'-) observed by Brunner (18), using resonance Raman spectroscopy.…”

Section: P(o-o) and V(fe-o) Stretching Vibrations The V(o-o)mentioning

confidence: 99%

Resonance Raman investigation of dioxygen bonding in oxycobaltmyoglobin and oxycobalthemoglobin: structural implication of splittings of the bound O--O stretching vibration.

Tsubaki¹,

Yu²

1981

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

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“…Oxyhemoglobin, HbO,, another low-spin ferrous derivative, was reported some time ago to be distinctly paramagnetic at room temperature [3,4] . The fact that P,-inositol reduces the paramagnetism of carp HbCO seemed to conflict with earlier observations on the relationship between the quaternary state of the hemoglobin molecule and the spinstate equilibria of ferric derivatives of carp hemoglobin [5,6].…”

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Magnetic and Spectral Properties of Carp Carbonmonoxyhemoglobin. Competitive Effects of Chloride Ions and Inositol Hexakisphosphate

Cerdonio

Morante

Vitale

et al. 1983

European Journal of Biochemistry

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We have extended our studies on the magnetic properties of carp carbonmonoxyhemoglobin and the dependence of these properties upon solution variables. Using an improved version of the superconducting magnetometer, we have found that the magnetic susceptibility of carp carbonmonoxyhemoglobin is sensitive to both inositol hexakisphosphate and chloride ion. The dependence upon chloride ion concentration is complex. At relatively low concentrations this anion reverses the effect of inositol hexakisphosphate, restoring paramagnetism. At higher chloride concentrations the protein is converted to a roughly diamagnetic state in the absence of inositol hexakisphosphate. Along with these susceptibility studies, we have examined the effects of these anions on other properties of carp carbonmonoxyhemoglobin. The positions of the Soret bands of human and carp methemoglobin derivatives are correlated with spin state ; changes in the magnetic susceptibility of carbonmonoxyhemoglobin are similarly associated with alterations in this spectral band. We have also examined the effects of these anions on the proton nuclear magnetic resonance spectrum of carp carbonmonoxyhemoglobin. Both chloride and inositol hexakisphosphate alter the position of the proton resonances in the ring-current-shifted region of the spectrum.Two years ago we reported an unexpected finding, that the carbon monoxide derivative of carp hemoglobin (HbCO) can exhibit paramagnetism [I J . This conclusion was the result of measurements of magnetic susceptibility and was based in large part on the observation that the addition of inositol hexakisphosphate (P,-inositol) increased the diamagnetism of carp HbCO as if a paramagnetic contribution had been quenched. The existence of paramagnetic states of HbCO has since been reported for human hemoglobin [2] and found to be related to the concentration of chloride ion.The paramagnetic properties of HbCO are of interest for several reasons. Oxyhemoglobin, HbO,, another low-spin ferrous derivative, was reported some time ago to be distinctly paramagnetic at room temperature [3,4] . The fact that P,-inositol reduces the paramagnetism of carp HbCO seemed to conflict with earlier observations on the relationship between the quaternary state of the hemoglobin molecule and the spinstate equilibria of ferric derivatives of carp hemoglobin [5,6]. In these studies it was persuasively shown that high-spin states favor the T state and reciprocally that the conversion of the molecule from the R to the T state shifts the spin-state equilibria of the iron atoms toward higher spin. The addition of P,-inositol to carp hemoglobin at pH 6 or below converts all derivatives of this hemoglobin to the T state [5,7,8]. Therefore, the fact that P,-inositol addition to carp HbCO reduced paramagnetism was puzzling. However, chloride has no effect Ahhrrviations. HbCO, carbonmonoxyhemoglobin; P,-inositol, inositol hexakisphosphate; NMR, nuclear magnetic resonance; Bistris, 2-[bis-(2-hydroxyethyl)amino]-2-(hydroxymethyl)-propane-l,3-diol; R, relaxe...

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Magnetic properties of oxyhemoglobin.

Cited by 82 publications

References 14 publications

Reexamination of the evidence for paramagnetism in oxy- and carbonmonoxyhemoglobins.

Reexamination of the evidence for paramagnetism in oxy- and carbonmonoxyhemoglobins.

Resonance Raman investigation of dioxygen bonding in oxycobaltmyoglobin and oxycobalthemoglobin: structural implication of splittings of the bound O--O stretching vibration.

Magnetic and Spectral Properties of Carp Carbonmonoxyhemoglobin. Competitive Effects of Chloride Ions and Inositol Hexakisphosphate

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