CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides ino-terphenyl glass: Dynamical transition, dynamical heterogeneity and β-relaxation

Dzuba, Sergei A.; Salnikov, Evgeniy S.; Кулик, Л. В.

doi:10.1007/bf03166223

Cited by 21 publications

(8 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To ensure that echo decays indeed originate from nanosecond stochastic molecular librations, a three-pulse stimulated spin echo 23,29,30 technique was employed. Nanosecond stochastic librations most likely 31,32 have the same nature as anharmonic motions detected in biological substances by neutron scattering and Mossbauer spectroscopy. 33−39 In these techniques, the mean-squared displacement (MSD), <r 2 >, of hydrogen atoms experiencing vibrational motion is obtained.…”

Section: ■ Introductionmentioning

confidence: 79%

Low-Temperature Molecular Motions in Lipid Bilayers in the Presence of Sugars: Insights into Cryoprotective Mechanisms

2014

View full text Add to dashboard Cite

Sugars and sugar alcohols can stabilize biological systems under extreme conditions of desiccation and freezing. Phospholipid bilayers solvated by aqueous solutions of sucrose, trehalose, and sorbitol at concentrations of 0.2 and 1 M and containing incorporated spin-labeled stearic acids were studied by electron spin echo (ESE) spectroscopy, a pulsed version of electron paramagnetic resonance (EPR). The phospholipids were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and the stearic acids were labeled with nitroxide 4,4-dimethyl-oxazolidine-1-oxyl (DOXYL) attached rigidly at either the 5th or 16th carbon positions. The ratio of the echo time traces for the two field positions in the EPR spectrum possessing the largest and smallest anisotropies gave the anisotropic contribution to the echo decay, which obeys exponential time dependence with good accuracy. At low temperatures, the anisotropic contribution is induced by stochastic (or diffusive) orientational vibrations of the molecule as a whole (i.e., stochastic molecular librations), with the exponential decay rate Wanis proportional to <α(2)>τc, where <α(2)> is the mean angular amplitude of the motion and τc is the correlation time. In all cases, it was found that Wanis begins to increase sharply above 170-200 K, which was ascribed to the dynamical transition known for biological systems at these temperatures. For hydration by the sucrose and trehalose solutions, Wanis was found to increase noticeably also above ∼120 K, which was explained by bilayer expansion due to direct bonding of sugar molecules to the bilayer surface. The Wanis temperature dependencies were found to be close to those obtained for the simple systems of the nitroxide spin probe TEMPONE in aqueous sorbitol and sugar 1 M solutions. This correlation suggests a possible mechanism of cryoprotective action of sorbitol and sugars due to the similarity of low-temperature motions in the membrane and in the cryoprotectant-containing surrounding liquid.

show abstract

Section: ■ Introductionmentioning

confidence: 79%

Low-Temperature Molecular Motions in Lipid Bilayers in the Presence of Sugars: Insights into Cryoprotective Mechanisms

2014

View full text Add to dashboard Cite

show abstract

“…5). Another implication of the temperature-dependent out-of-plane motion of the nitroxide label for EPR studies of multi-mode molecular motion under the constraints of the guestmatrix system is the suggestion to disentangle this complex motion at a fixed temperature by using a multi-frequency EPR approach [19,63,65,66] rather than at a fixed EPR frequency and varying the temperature [64,[67][68][69][70][71].…”

Section: Discussionmentioning

confidence: 99%

The Temperature Dependence of Nitroxide Spin–Label Interaction Parameters: a High-Field EPR Study of Intramolecular Motional Contributions

Savitsky¹,

Plato

Möbius

2009

Appl Magn Reson

View full text Add to dashboard Cite

High-field W-band electron paramagnetic resonance (EPR) spectroscopy was utilized to study the temperature dependence of the magnetic interaction parameters (g-, hyperfine-, quadrupole tensors) of two types of doublet-state nitroxide spin probes in glass-forming ortho-terphenyl solution: a five-membered ring system of pyrroline type (model for the commonly used methane thiosulfonate spin label) and a six-membered ring system of piperidine type (model for the commonly used TOAC spin label). The analysis of the g-and hyperfine tensors in terms of their isotropic and anisotropic parts reveals at least two mechanisms of motion that are responsible for the temperature dependence of the interaction parameters. The first mechanism is attributed to the overall small-angle motion of the nitroxide molecule in the glassy matrix; it leads to an averaging of the anisotropies of the EPR parameters. The second mechanism originates in an intramolecular out-of-plane motion of oxygen in the nitroxide group. This type of motion is evidenced by comparing the experimental findings for the spin-interaction parameters with the results of density functional theory calculations. The harmonic oxygen out-of-plane vibrations result in a variation of both the isotropic and anisotropic parts of the g-and hyperfine tensors. In contrast, the quadrupole tensor is not influenced by this vibration mechanism in the temperature range under study (90-240 K). Consequences of the applicability of such typical nitroxide radicals for probing details of their protein environment and for studying librational dynamics in frozen solutions are discussed.

show abstract

“…The principal g-and A-tensor values of g = [2.0083; 2.0060; 2.0022] and A = [0.54; 0.54; 3.79] mT differ slightly from the room-temperature values. This deviation is probably due to the restriction of the nitroxide librational motion 75 and a reduced out-of-plane motion of the nitroxide oxygen 76 at 150 K as compared to that at room temperature. The g-and A-tensor values are in good agreement with those obtained previously for the same nitroxide spin probe in frozen glycerol solution at 180 K. 59 This shows the close similarity of both matrices in terms of polarity and proticity of the nitroxide microenvironments.…”

Section: W-band Epr Of Dehydrated Matricesmentioning

confidence: 97%

Structural and dynamical characteristics of trehalose and sucrose matrices at different hydration levels as probed by FTIR and high-field EPR

Malferrari

Nalepa

Venturoli

et al. 2014

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Some organisms can survive complete dehydration and high temperatures by adopting an anhydrobiotic state in which the intracellular medium contains large amounts of disaccharides, particularly trehalose and sucrose. Trehalose is most effective also in protecting isolated in vitro biostructures. In an attempt to clarify the molecular mechanisms of disaccharide bioprotection, we compared the structure and dynamics of sucrose and trehalose matrices at different hydration levels by means of high-field W-band EPR and FTIR spectroscopy. The hydration state of the samples was characterized by FTIR spectroscopy and the structural organization was probed by EPR using a nitroxide radical dissolved in the respective matrices. Analysis of the EPR spectra showed that the structure and dynamics of the dehydrated matrices as well as their evolution upon re-hydration differ substantially between trehalose and sucrose. The dehydrated trehalose matrix is homogeneous in terms of distribution of the residual water and spin-probe molecules. In contrast, dehydrated sucrose forms a heterogeneous matrix. It is comprised of sucrose polycrystalline clusters and several bulk water domains. The amorphous form was found only in 30% (volume) of the sucrose matrix. Re-hydration leads to a structural homogenization of the sucrose matrix, whilst in the trehalose matrix several domains develop differing in the local water/radical content and radical mobility. The molecular model of the matrices provides an explanation for the different protein-matrix dynamical coupling observed in dried ternary sucrose and trehalose matrices, and accounts for the superior efficacy of trehalose as a bioprotectant. Furthermore, for bacterial photosynthetic reaction centers it is shown that at low water content the protein-matrix coupling is modulated by the sugar/protein molar ratio in sucrose matrices only. This effect is suggested to be related to the preference for sucrose, rather than trehalose, as a bioprotective disaccharide in some anhydrobiotic organisms.

show abstract

CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides ino-terphenyl glass: Dynamical transition, dynamical heterogeneity and β-relaxation

Cited by 21 publications

References 44 publications

Low-Temperature Molecular Motions in Lipid Bilayers in the Presence of Sugars: Insights into Cryoprotective Mechanisms

Low-Temperature Molecular Motions in Lipid Bilayers in the Presence of Sugars: Insights into Cryoprotective Mechanisms

The Temperature Dependence of Nitroxide Spin–Label Interaction Parameters: a High-Field EPR Study of Intramolecular Motional Contributions

Structural and dynamical characteristics of trehalose and sucrose matrices at different hydration levels as probed by FTIR and high-field EPR

Contact Info

Product

Resources

About