149 research outputs found
Isolation of beta2GPI by perchloric acid yields three proteins having different antigenic properties
Low temperature electron-spin relaxation in the crystalline and glassy states of solid ethanol
X-band electron paramagnetic resonance (EPR) spectroscopy was used to study
the spectral properties of a nitroxide spin probe in ethanol glass and
crystalline ethanol, at 5 - 11.5 K. The different anisotropy of molecular
packing in the two host matrices was evidenced by different rigid limit values
for maximal hyperfine splitting in the signal of the spin probe. The
significantly shorter phase memory time, , for the spin probe dissolved in
crystalline ethanol, as compared to ethanol glass, was discussed in terms of
contribution from spectral diffusion. The effect of low-frequency dynamics was
manifested in the temperature dependence of and in the difference between the
data measured at different spectral positions. This phenomenon was addressed
within the framework of the slow-motional isotropic diffusion model [S. Lee,
and S. Z. Tang, Phys. Rev. B 31, 1308 (1985)] predicting the spin probe
dynamics within the millisecond range, at very low temperatures. The shorter
spin-lattice relaxation time of the spin probe in ethanol glass was interpreted
in terms of enhanced energy exchange between the spin system and the lattice in
the glass matrix due to boson peak excitations.Comment: 16 pages, 4 figures, 36 reference
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