The rotational mobility of the mitochondrial ADP/ATP carrier has been studied solubilized in Triton micelles, reincorporated in phospholipid liposomes, and in mitochondria. Spin-labeled analogues of the noncovalent inhibitors carboxyatractyloside and atractyloside were found to be strongly immobilized when bound to the carrier [Munding, A., Beyer, K., & Klingenberg, M. (1983) Biochemistry 22, 1...

The measurement of (1)H transverse paramagnetic relaxation enhancement (PRE) has been used in biomolecular systems to determine long-range distance restraints and to visualize sparsely-populated transient states. The intrinsic flexibility of most nitroxide and metal-chelating paramagnetic spin-labels, however, complicates the quantitative interpretation of PREs due to delocalization of the para...

A spin-labeled derivative of rabbit muscle creatine kinase has been prepared by reaction of the essential sulfhydryl group at the active sites with a stoichiometric amount of the nitroxide radical N-( I-oxyl-2,2,5,5-tetramethyl-d-pyrrolidinyl) iodoacetamide. The spin-labeled enzyme retains the ability to bind nucleotide substrates although it lacks the phosphotransferase and ATPase activities o...

A nitroxide spin-label probe was attached directly to a propionic acid group of heme in either the a or the P chain of hemoglobin. The electron paramagnetic resonance (EPR) spectrum of the spin label is altered by the spin-state change of the heme iron to which the spin label is attached. These hybrid hemoglobins showed normal optical and functional properties, indicating that the attachment of...

BACKGROUND Spin labels, which are chemically stable radicals attached at specific sites of a bio-molecule, enable investigations on structure and dynamics of proteins and nucleic acids using techniques such as site-directed spin labeling and paramagnetic NMR. Among spin labels developed, the class of rigid labels have limited or no independent motions between the radical bearing moiety and the ...

2,3-Bisphosphoglycerate, the predominant phosphorylated metaholite of the human red blood cell, binds tightly to human deoxyhemoglobin and weakly, yet significantly, to human oxyhemoglobin. To locate the binding site(s) for 2,3-bisphosphoglycerate in both oxyand deoxyhemoglobins in solution, we have measured the paramagnetic effects of hemoglobin spin-labeled with a nitroxide radical at each of...

The rotational mobility of spin-labeled bovine heart mitochondrial cytochrome e oxidase in purified form, and incorporated into lipid vesicles was studied. A rigidly attached short chain maleimide spin label permitted the measurement of the protein’s overall rotational mobility by saturation transfer electron paramagnetic resonance. A long chain maleimide spin label was used to detect he fluidi...

In electron paramagnetic resonance (EPR) distance distributions between site-directedly attached spin labels in soft matter are obtained by measuring their dipole-dipole interaction. The analysis of these distance distributions can be misleading particularly for broad distributions, because the most probable distance deviates from the distance between the most probable label positions. The curr...

Electron magnetic resonance experiments have demonstrated that spin-labeled myotonic erythrocyte membranes have spectra that are recognizably different from those of normal erythrocytes. The spin label incorporated in the erythrocyte membranes of patients having myotonic muscular dystrophy is apparently located in a less polar and somewhat more fluid region than the label in a normal membrane. ...