The biomembrane is postulated as the initial target when Platinum(II) complexes attack cells. In this work, a spin-labeling ESR technique has been used to study the effects of cis-DCDP, cis-DBDP, cis-DIDP, trans-DCDP, and cis-DADP on the permeability of human erythrocyte membrane. We monitored the reduction processes of the ESR signal of a nitroxide spin label, (TEMPO), which leaks out through ...

The interaction between gbcolgnorin and a spin-labeled cholesterol analogue has been tmestigated ~ EPR spee4recopy. In vesicles which were ¢econsti~ted by the freeze and thaw teelmique, ditcher evidenee was obtalned for a reorgamsatlon el the membcane at low protein content {protein/lipid ratio le~ than ! ,300). From the sign exchange interaction we were able to show a ~otem-indneed clustering ...

Electron paramagnetic resonance employing a lipid-specific spin label has been used to investigate the molecular effects of endotoxin on the physical state of bilayer lipids in rat erythrocyte membranes. When added at a concentration as low as 40 micrograms/ml to whole blood (plasma plus leukocytes present), decreased membrane lipid motion was found in subsequently washed and spin-labeled intac...

The orientation of a-helices or b-strands, e.g., in membranes, can be determined from EPR order parameters of (2,2,6,6-tetramethylpiperidine-1-oxy-4-amino-4-carboxylic acid) TOAC amino-acid spin labels incorporated in the polypeptide backbone. This requires knowledge of the inclination of the nitroxide axes, relative to the a-helix or b-strand axis. Crystal structures of TOAC-containing peptide...

Spin-label electron paramagnetic resonance (SL-EPR) spectroscopy has become a powerful and useful tool for studying structure and dynamics of biomacromolecules. However, utilizing these methods at physiological temperatures for in-cell studies is hampered by reduction of the nitroxide spin labels and thus short half-lives in the cellular environment. Consequently, reduction kinetics of two stru...

Rigid spinning: Site-directed spin-labeling studies using a rigid nitroxide spin label (Ç) reveal that both length and sequence of a single-stranded junction (J1/2) modulate nanosecond motional ordering of the substrate-recognition duplex (P1) of the 120 kD group I ribozyme. The studies demonstrate an approach for experimental measurements of nanosecond dynamics in high-molecular-weight RNA com...

Thermal lability of bovine erythrocyte membrane proteins was studied by electron spin resonance using maleimide spin label. The temperature of the sample during measurements could be varied for the first time between 0 and 60 degrees C with an accuracy of +/- 0.1 degrees C. Our results show that "old" erythrocyte membrane proteins are less stable against thermal denaturation then "young" cells.

An isoindoline-nitroxide derivative of guanine (Ǵ, "G-spin") was shown to bind specifically and effectively to abasic sites in duplex RNAs. Distance measurements on a Ǵ-labeled duplex RNA with PELDOR (DEER) showed a strong orientation dependence. Thus, Ǵ is a readily synthesized, orientation-selective spin label for "mix and measure" PELDOR experiments.

The electron spin resonance spectra of 1-myristoyl-2-[n-(4,4-dimethyloxazolidine-N-oxyl)myristoyl]-sn- glycero-3-phosphocholine spin-label positional isomers (n = 6, 10, and 13) have been studied in oriented, fully hydrated bilayers of dimyristoylphosphatidylcholine, as a function of temperature and magnetic field orientation. The spectra have been simulated using a line-shape model which incor...

To test models for the pentameric structure of phospholamban (PLB) and study its structure and molecular dynamics in SDS solution, we characterized recombinant PLB and several of its mutants by (a) reactivity of cysteine residues toward DTNB [5, 5'-dithiobis(2-nitrobenzoic acid)] and a thiol-reactive spin label, (b) oligomeric state on SDS-PAGE, and (c) EPR of the spin-labeled proteins. WT-PLB ...