PubMed · 8753211
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Y Ohba. 1995. [Carboxyhemoglobin].. https://pubmed.ncbi.nlm.nih.gov/8753211/
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Human alpha-nitrosyl beta-deoxy hemoglobin A, alpha(NO)beta(deoxy), is considered to have a T (tense) structure with the low O(2) affinity extreme and the Fe-histidine (His87) (Fe-His) bond of alpha heme cleaved. The Fe-His bonding of alpha heme and the intersubunit interactions at the alpha 1-beta 2 contact of alpha(NO)-Hbs have been examined under various conditions with EPR and UV resonance Raman (UVRR) spectra excited at 235 nm, respectively. NOHb at pH 6.7 gave the UVRR spectrum of the R structure, but in the presence of inositol-hexakis-phosphate (IHP) for which the Fe-His bond of the alpha heme is broken, UVRR bands of Trp residues behaved half-T-like while Tyr bands remained R-like. The half-ligated nitrosylHb, alpha(NO)beta(deoxy), in the presence of IHP at pH 5.6, gave T-like UVRR spectra for both Tyr and Trp, but binding of CO to its beta heme (alpha(NO)beta(CO)) changed the UVRR spectrum to half-T-like. Binding of NO to its beta heme (NOHb) changed the UVRR spectrum to 70% T-type for Trp but almost R-type for Tyr. When the pH was raised to 8.2 in the presence of IHP, the UVRR spectrum of NOHb was the same as that of COHb. EPR spectra of these Hbs indicated that the Fe-His bond of alpha(NO) heme is partially cleaved. On the other hand, the UVRR spectra of alpha(NO)beta(deoxy) in the absence of IHP at pH 8.8 showed the T-like UVRR spectrum, but the EPR spectrum indicated that 40-50% of the Fe-His bond of alpha hemes was intact. Therefore, it became evident that there is a qualitative correlation between the cleavage of the Fe-His bond of alpha heme and T-like contact of Trp-beta 37. We note that the behaviors of Tyr and Trp residues at the alpha 1-beta 2 interface are not synchronous. It is likely that the behaviors of Tyr residues are controlled by the ligation of beta heme through His-beta 92(F8)-->Val-beta 98(FG5)-->Asp-beta 99(G1 )-->Tyr-alpha 42(C7) or Tyr-beta 145(HC2).
In order to obtain information on the structural aspects of hemoglobin (Hb), Fourier transform Raman (FT-R) measurements on various ferrous, ferric derivatives and nickel reconstituted Hb (NiHb) has been made. FT-R spectra for these derivatives were obtained by laser excitation in the near infrared region (NIR) (1064 nm) whereby the wave-number region (600-1700 cm-1) related to both porphyrin ring modes and some globin modes were monitored. Comparison of various modes was made based on previous resonance Raman (RR) results. The wave-number shifts with respect to changes in oxidation state and spin state are very similar to those observed by RR. Additional bands at 1654, 1459, and 1003 cm-1 for deoxyHb and at 1656, 1454, and 1004 cm-1 for oxy Hb can be correlated to globin modes. The shift in the position of these bands for the binding of oxygen can be related to changes in conformation during the transformation. The presence of two distinct sites in NiHb could be monitored by the use of FT-R technique.
Many people engage in physical activity to reduce their cardiovascular risk associated with smoking. These people should be made aware of the metabolic and cardiorespiratory changes induced by chronic and acute smoking and, in particular, the exercise ramifications of increased levels of blood carbon monoxide (CO). Smoking-induced elevations in the CO content of the blood can reduce exercise tolerance and maximal aerobic capacity. Smoking also increases the reliance upon glycolytic metabolism during exercise. Together, these factors contribute to earlier fatigue in smokers compared with nonsmokers who exercise. Similar effects upon exercise tolerance are noted in those who inhale environmental tobacco smoke.