Simulated electron spin resonance spectra of nitroxide spin labels in slowly reorienting rod shaped molecules

1975 ◽  
Vol 71 ◽  
pp. 807
Author(s):  
J. E. Benton ◽  
R. M. Lynden-Bell
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Labels ◽  
Spin Resonance ◽  
Nitroxide Spin Labels

scholarly journals High-field electron spin resonance of spin labels in membranes

2002 ◽  
Vol 116 (1-2) ◽  
pp. 93-114 ◽  
Author(s):  
Derek Marsh ◽  
Dieter Kurad ◽  
Vsevolod A. Livshits
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
High Field ◽  
Spin Labels ◽  
Field Electron ◽  
Spin Resonance

Electron Spin Resonance Studies on Conformational Changes of the Sarcoplasmic Reticulum Ca2+ – ATPase Induced by Synergistic Action of Calcium and ATP

1981 ◽  
Vol 36 (9) ◽  
pp. 1136-1143 ◽  
Author(s):  
Peter Laggner ◽  
Josef Suko ◽  
Christian Punzengruber ◽  
Rudolf Prager
Keyword(s):  
Electron Spin Resonance ◽  
Sarcoplasmic Reticulum ◽  
Electron Spin ◽  
Conformational Changes ◽  
Environmental Changes ◽  
Adenine Nucleotides ◽  
Membrane Vesicles ◽  
Heterocyclic Ring ◽  
Spin Labels ◽  
Spin Resonance

Abstract Changes in motional properties of the -SH group environment in sarcoplasmic reticulum ATPase [1] induced by addition of specific ligands to sarcoplasmic reticulum membrane vesicles were investigated systematically by electron spin resonance (e.p.r.) spectroscopy. Alternatively, two kinds of iodoacetamide analog spin labels, 4-(2-iodoacetamido)- 2,2,5,5-tetramethyl-1-pyrrolidinyl-N-oxyl (label I) and 4-(2-iodoacetamido)-2,2,6,6-tetramethyl- 1-piperidinyl-N-oxyl (label II) were used. The labeling conditions were chosen such that less than three moles of -SH groups per mole of ATPase reacted with the spin labels. A marked increase in isotropic motion of either spin label was observed on addition of calcium in millimolar concentrations plus ATP or β-γ-methylene ATP. Qualitatively similar but smaller changes were also observed with inosine 5'-triphosphate (ITP), acetylphosphate, or ADP in the presence of calcium. These effects were independent of added magnesium. The spectral changes induced by β-γ-methylene ATP, which binds to the ATPase but is not hydrolyzed, and those of calcium plus ADP suggest a conformational change due to simultaneous binding of these ligands in the absence of enzyme phosphorylation. These changes in e.p.r. spectra were different in quality and magnitude from those observed upon separate binding of calcium or adenine nucleotides. The two spin labels, differing only in their numbers of heterocyclic ring atoms, were found to reflect environmental changes in different ways. This demonstrates the usefulness of employing different spin labels to detect and interpret structural transitions in macromolecular assemblies.

A Spin Label Study of the Influence of Cholesterol on Egg Lecithin Multibilayers

1972 ◽  
Vol 50 (9) ◽  
pp. 969-981 ◽  
Author(s):  
Roy D. Lapper ◽  
Sabina J. Paterson ◽  
Ian C. P. Smith
Keyword(s):  
Electron Spin Resonance ◽  
Random Walk ◽  
Electron Spin ◽  
Spin Label ◽  
Theoretical Models ◽  
Cholesterol Content ◽  
Electron Spin Resonance Study ◽  
Spin Labels ◽  
Spin Resonance ◽  
Egg Lecithin

A detailed electron spin resonance study of a cholestane spin label in hydrated egg lecithin multibilayers of variable cholesterol content is presented. Several theoretical models are proposed in an attempt to explain the observed electron spin resonance spectra for the egg lecithin–cholesterol multibilayer system; we conclude that the most probable model is that of restricted random walk of individual spin labels where the amplitude of the random walk decreases from about 46° at 0 mol% cholesterol content to a minimum of 17° at 55 mol% cholesterol. Also, as the cholesterol content of the multibilayers increases, so the rate of random walk decreases from rapid to intermediate on the electron spin resonance time scale. The results clearly indicate that cholesterol is able to order egg lecithin films, orientating all molecules towards a normal to the surface of the film and decreasing their mobility. The condensing and stiffening influence of cholesterol in phospholipids is undoubtedly one of its major roles in biological membranes.

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