Mdssbauer spectrum quadrupole splitting

Fig. 10. Mdssbauer spectra of reduced (left panels) and oxidized (right panels) PS-I core complex at 80 K (top panels) and 4.2 K (bottom panels), The lower spectrum in each of the left panels was corrected for the unreduced component. The table at top right lists the experimentally determined isomer-shift (IS) and quadrupole-splitting (QS) parameters for oxidized and reduced core complexes at 77 K lower table lists isomer-shift values reported in the literature for other [4Fe 4S] and [2Fe 2S] clusters. Data source Petrouleas, Brand, Parrett and Golbeck (1989) A Mossbauer analysis of the low-potential iron-sulfur center in photosystem I Spectroscopic evidence that Fx is a [4Fe-4S] cluster. Biochemistry 28 8982.

The hydroxylase component of methane monooxygenase (MMO) contains the diiron active site (11, 12, 30, 31). The properties of the diferric form of MMO differ from those of metHr and RRB2. This enzyme is essentially colorless with an electronic spectrum that exhibits a weak absorption tail in the region of 300-400 nm (Fig. 10). It exhibits only one quadrupole doublet in the Mdssbauer spectrum with a splitting of 1.07 mm s a value that is intermediate between (p.-oxo)diiron complexes... 

A quadrupole split Mdssbauer spectrum results from a nucleus... 

An electric quadrupole transition is a y-ray transition between the hyperfine multi-plets of the nucleus in its ground and excited states. Only those nuclear states with 7 > 1 /2 have a nuclear quadrupole moment and hence show quadrupole hyper-flne splitting. Thus, it is often possible to observe a quadrupole interaction in the Mdssbauer spectrum that derives from the excited nuclear state. 

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