Bridged isotopic substitution

The resonance Raman spectmm of RRB2 shows symmetric and asymmetric Fe-O-Fe stretching noodes which have been assigned by isotopic substitution (66,67), In solution at room temperature these resonances are observed at 492 cm and ca. 756 cm-. These values are very similar to the values for oxylfr (486 and 753 cm l). In D2O, shifts to 495 cm l, which suggests a hydrogen bond to the 0x0 bridge (as in oxyHr). 

Analysis of the vibrational spectra of the junctions before exposure to hydrogen ( Fig. 14 ) ( including isotopic substitutions ) showed the presence of at least three different CO species on the surface, two different linear-bonded species and at least one bridge bonded species. 

Resonance Raman spectra of [Fe2S2(Cys)4] proteins, illustrated in Fig. 21 for adrenodoxin and a plant ferredoxin, are substantially more complex, as might be expected. With the aid of isotope substitution and model compound data, it has nevertheless been possible to characterize the modes completely and to assign them to vibrations involving primarily the bridging or terminal sulfur atoms (superscripts b and t, respectively. 

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