Ii

340 344 343

340 344 343

Fig. 20. EPR spectra from 1 mM solutions of apo-metallothionein (apo-Mt) from horse kidney after the addition of 1 mM DNIC with phosphate (curve a) with following addition of 1% dodecyl sulfate (SDS) (curve b) or after 1 h exposure of the solution (a) in air (c). Recordings were made at ambient temperature [73].

Fig. 21. Shape of the EPR signal of DNIC with undiscolored or discolored rhodopsin (curves a,d and b,e, respectively). (Curves c,f) the EPR signal of DNIC with rhodopsin which was discolored after DNIC formation. Recordings were made at 77 K (curves a-c) or at ambient temperature (curves d-f), respectively [82].

Fig. 21. Shape of the EPR signal of DNIC with undiscolored or discolored rhodopsin (curves a,d and b,e, respectively). (Curves c,f) the EPR signal of DNIC with rhodopsin which was discolored after DNIC formation. Recordings were made at 77 K (curves a-c) or at ambient temperature (curves d-f), respectively [82].

when raising the temperature from 77 K to ambient, which indicated a bond between DNIC and protein globule. Similar signal was recorded for DNIC bound with apo-Mt from rabbit liver [23,75]. On addition of 1% of DDS to the protein solution, the component at g|| decreased and the spectrum became very similar to that of DNIC-BSA in the presence of SDS [71] (Fig. 20, curves b,c). By now, several publications document the formation of DNIC anchored on other proteins like FNR [67,76,77] flavorubredoxin [78], ferritin [79], glutathione reductase [80] or glutathione-transferase [81].

The formation of DNIC with rhodopsin was described in the preparation of the protein treated with NO gas in the presence of ferrous iron [82]. The shape of the EPR signals from rhodopsin-bound DNIC slightly differs from that of frozen solution of DNIC with cysteine and varies depending on illuminating or aging of the rhodopsin suspensions. Prolonged illumination induces bleaching and discoloration of the preparations (Fig. 21).

Protein-bound DNICs can appear in various iron-sulfur proteins treated with NO [59,66,83]. The formation of DNIC in the latter is considered in the Chapters 5 and 6 of this book.

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