Resonance Raman Studies of Hemoglobin with Selectively Deuterated Hemes. A New Perspective on the Controversial Assignment of the Fe-CO Bending Mode
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- 作者：Cynthia Rajani and James R. Kincaid
- 刊名：Journal of the American Chemical Society
- 出版年：1998
- 出版时间：July 29, 1998
- 年：1998
- 卷：120
- 期：29
- 页码：7278 - 7285
- 全文大小：161K
- 年卷期：v.120,no.29(July 29, 1998)
- ISSN：1520-5126
文摘
In an effort to resolve an existing controversy involving the assignment of the bending fundamental[
(FeCO)] of CO-ligated heme proteins, resonance Raman studies of the CO adducts of native hemoglobin(Hb), together with Hb containing selectively deuterated hemes, have been conducted. Hemes were utilizedwhich were deuterated at the peripheral methyl positions (d12) or at the methine carbon positions (d4). SeveralCO isotope sensitive modes were observed in the low-frequency region (300-400 cm-1) by generating differencespectra from the absolute spectra of the natural abundance (NA) and doubly labeled 13C18O (DI) CO-Hb.These features included one at ~370 cm-1. Deconvolution of the low-frequency region revealed that a 1-2cm-1 shift of a heme mode at 367 cm-1 is responsible for this difference feature. In the mid-frequency spectralregion (650-1300 cm-1), features which were previously suggested to be ascribable to combination bandsand overtones involving the proposed ~370 cm-1 (FeCO) fundamental showed sensitivity to heme deuteration,a fact which suggests that these modes are combinations involving heme modes rather than two internalfundamentals of the FeCO fragment. These results imply, therefore, that the observation of weak isotope-sensitive features in the 700-900 cm-1 region does not support the assignment of the ~370 cm-1 feature tothe (FeCO) fundamental, but these features are more reasonably interpreted to arise from combinationsinvolving the relatively strong 
(Fe-CO) and lower frequency heme modes, an interpretation that is consistentwith the long-standing assignment of the weak band near 580 cm-1 to the (FeCO) fundamental.
(FeCO)] of CO-ligated heme proteins, resonance Raman studies of the CO adducts of native hemoglobin(Hb), together with Hb containing selectively deuterated hemes, have been conducted. Hemes were utilizedwhich were deuterated at the peripheral methyl positions (d12) or at the methine carbon positions (d4). SeveralCO isotope sensitive modes were observed in the low-frequency region (300-400 cm-1) by generating differencespectra from the absolute spectra of the natural abundance (NA) and doubly labeled 13C18O (DI) CO-Hb.These features included one at ~370 cm-1. Deconvolution of the low-frequency region revealed that a 1-2cm-1 shift of a heme mode at 367 cm-1 is responsible for this difference feature. In the mid-frequency spectralregion (650-1300 cm-1), features which were previously suggested to be ascribable to combination bandsand overtones involving the proposed ~370 cm-1 (FeCO) fundamental showed sensitivity to heme deuteration,a fact which suggests that these modes are combinations involving heme modes rather than two internalfundamentals of the FeCO fragment. These results imply, therefore, that the observation of weak isotope-sensitive features in the 700-900 cm-1 region does not support the assignment of the ~370 cm-1 feature tothe (FeCO) fundamental, but these features are more reasonably interpreted to arise from combinationsinvolving the relatively strong (Fe-CO) and lower frequency heme modes, an interpretation that is consistentwith the long-standing assignment of the weak band near 580 cm-1 to the (FeCO) fundamental.