Naslov
Resonance Raman Studies of Nitric Oxide Binding to Ferric and Ferrous Hemoproteins: Detection of Fe(III)-NO Stretching, Fe(III)-N-O Bending and Fe(II)-N-O Bending Vibrations

Autori
Benko, Bojan ; Yu, Nai-Teng

Izvornik
Proceedings of the National Academy of Sciences of the United States of America (0027-8424) 80 (1983), 22; 7042-7046

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Haemoglobin ; Horseradish peroxidase ; Isotope shift ; Myoglobin ; Nitrosyl ; Resonance Raman

Sažetak
The nature of bonding interactions between Fe(III) and NO in the ferric nitrosyl complexes of myoglobin (Mb), hemoglobin A (HbA), and horseradish peroxidase (HRP) is investigated by Soret-excited resonance Raman spectroscopy. On the basis of 15NO and N18O isotope shifts, we clearly identified the Fe(III)– NO bond stretching frequencies at 595 cm-1 (ferric Mb• NO), 594 cm-1 (ferric HbA• NO), and 604 cm-1 (ferric HRP• NO). The Fe(III)– N– O bending vibrations are located at 573 cm-1 (ferric Mb• NO) and 574 cm-1 (ferric HRP• NO), which are very similar to the Fe(II)– C– O bending modes at 578 cm-1 in Mb• CO and HbA• CO. However, the Fe(III)– NO and Fe(II)– CO stretching frequencies differ by » ; ; 90 cm-1, indicating a much stronger iron-axial ligand bond for the [Fe(III) + NO] system, which is isoelectronic with the [Fe(II) + CO] system and, hence, presumably also has a linear Fe(III)– N– O linkage (in the absence of distal steric effect). The unusually strong Fe(III)– NO bond may be attributed to the π bonding involving the unpaired electron in the π * (NO) orbital. The N18O isotope shift data indicate that the widely accepted assignment of the Fe(II)– NO stretching vibration » ; ; 554 cm-1 in ferrous nitrosyl Mb/HbA is incorrect ; instead, we assign it to the Fe(II)– N– O bending mode. The validity of the assignment of Fe(II)– O2 stretch at 567 cm- 1 in oxy-HbA by Brunner [Brunner, H. (1974) Naturwissenschaften 61, 129-130] is now in doubt. Literature data are presented to suggest that it is the Fe(II)– O– O bending vibration.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija, Biologija

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