Nitroxide free radicals proteins

Flavodoxins have a natural spin label, but, unlike the nitroxides, the flavin-free radical suffers from electron de-localisation, which interferes with distance calculations. The broadening of protein resonances in the spectra of the semiquinone forms of flavodoxins from Clostridium MP and Peptostreptococcus elsdenii is highly selective [99], and peaks from groups in the vicinity of the radical can be assigned. 

N-Hydroxyamino acids, similar in action to N-hydroxyurea, some N-hydroxyamides and some aromatic hydroxy acids, are inhibitors of ribonucleotide reductases 112), a unique group of metalloenzymes, essential for cell proliferation. Inhibition of substrate reduction in vitro (l5o = 2.3-10 ) is accompanied by decay of the tyrosyl radical but not the iron atom from the E. coli subunit B2 of this enzyme. Inhibitors of the above type donate an electron to the enzyme s free radical, producing an inactive protein-enzyme with a still intact binuclear iron complex and a new more stable free radical of the nitroxide type (52)... 

CRP LRP in Figure 1), ATRP or atom transfer (radical) polymn ( ATRP only , this search does not include terms such as metal mediated or metal catalyzed (living) radical polymerization), NMP or SFRP or nitroxide mediated polymn ot stable free polymn ( SFRP NMP ) and RAFT ox reversible addition transfer or degenerative transfer or catalytic chain transfer ( RAFT DT CT ). The latter two terms were refined with a term radical polymn since they coincide with other common chemical names such as N-methylpyrrolidone or raft-associated proteins. In summary, since 1995 over... 

To date, the most commonly used spin labels for membrane proteins are pyrroline-type nitroxide radicals. Several labeling strategies and spin labels are available at present. However, the extreme specificity for the free thiol of cysteines, a stoichiometric reaction at most sites, and the relatively small size and flexibility of the modified side chain make the (l-oxyl-2,2,5,5-tetramethyl-A3-p3Troline-3-methyl) methanethiosulfonate spin label (MTSSL) the most popular choice for SDSL applications. 3 -(2-lodoacetamido)-2,2,5,5-tetramethyl-1 -pyrrolidinyloxy radical labels (lAP) are also used in combination with cysteines. The advantage of LAP vs MTSSL is that the covalent bond with the cysteine is irreversibly formed and this may be more suitable for particular situations in which the MTSSL tends to be released from the labeled sites. 

Valentine and co-workers proposed merging the ODNP technology at 0.35 Tesla with encapsulating proteins in reverse micelles dispersed in low viscosity hydrocarbon solvents. Using these solvents rather than water greatly reduced the heating effects of microwaves. The nitroxide radicals were introduced in the reverse micelle system in three ways attached to the protein, embedded in the reverse micelle shell and free in the aqueous core. 

---