The nitroxide spin label 1-oxyl-2,2,5,5-tetramethylpyrroline-3-methyl-methanethiosulfonate (MTSSL), commonly used in site-directed spin labeling of proteins, is studied with molecular dynamics (MD) simulations. After developing force field parameters for the nitroxide moiety and the spin label linker, we simulate MTSSL attached to a polyalanine alpha-helix in explicit solvent to elucidate the f...

14 S W Y : The incorporation of [ C ] N-ethylmaleimide reveals fast and slowreacting sulfhydryl groups in sarcoplasmic reticulum. Two proteins react with the label: a fast-reacting glycoprotein recently isolate$+(Ikemoto, Cucchiaro and Garcia (1976) J. Cell Biol. 10, 290a), and the Ca -ATPase. Labeling sarcoplasmic reticulum with a maleimide spin label gives a similar pattern. The spectra of ma...

Long-range distance measurements based on paramagnetic relaxation enhancement (PRE) in NMR, quantification of surface water dynamics near biomacromolecules by Overhauser dynamic nuclear polarization (DNP) and sensitivity enhancement by solid-state DNP all depend on introducing paramagnetic species into an otherwise diamagnetic NMR sample. The species can be introduced by site-directed spin labe...

Multifrequency electron spin resonance (ESR) spectra provide a wealth of structural and dynamic information about the local environment of the spin label and, indirectly, about the spin-labeled protein. Relating the features of the observed spectra to the underlying molecular motions and interactions is, however, challenging. To make progress toward a rigorous interpretation of ESR spectra, we ...

The influence of spin-orbit coupling in two-dimensional systems is investigated within the framework of the Landauer-Büttiker coherent scattering formalism. After a short review of the features of spin-orbit coupling in two-dimensional electron gases, we define the creation and annihilation operators for the stationary states of the Rashba spin-orbit coupling Hamiltonian and use them to calcula...

was chemically bonded to poly-L-lysine and to bovine serum albumin (BSA) and showed a paramagnetic resonance spectrum that was sensitive to known structural changes in these molecules, such as those produced by changes in pH.2 This nitroxide-isocyanate is unfortunately not an ideal spin-labeling reagent since it is unstable and thus difficult to purify, and moreover the isocyanate group is rapi...

The pulse DEER (Double Electron–Electron Resonance) technique is frequently applied for measuring nanometer distances between specific sites in biological macromolecules. In this work we extend the applicability of this method to high field distance measurements in a protein assembly with mixed spin labels, i.e. a nitroxide spin label and a Gd tag.We demonstrate the possibility of spectroscopic...

The modification of avian phosphoenolpyruvate carboxykinase by a variety of sulfhydryl reagents leads to inhibition. The inhibition is related to the loss of 1 highly reactive cysteine residue of the 13 cysteines present in the enzyme. Inhibition by reagents which yield a mixed disulfide was rapidly reversed by thiols. Reagents specific for vicinal sulfhydryl configurations were not potent inhi...

EPR/DEER spectroscopy is playing an increasingly important role in the characterization of the conformational states of proteins. In this study, force field parameters for the bifunctional spin-label (RX) used in EPR/DEER are parametrized and tested with molecular dynamics (MD) simulations. The dihedral angles connecting the Cα atom of the backbone to the nitroxide ring moiety of the RX spin-la...