J Chem Phys 2013 Feb;138(7):074705
Department of Physics, University of Puerto Rico, Rio Piedras, P.O. Box 23343, San Juan, Puerto Rico.
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Biochemistry 1992 Jan;31(2):532-41
Department of Chemistry, Yale University, New Haven, Connecticut 06511.
The stable tyrosine radical YD. (tyrosine 160 in the D2 polypeptide) in photosystem II (PSII) exhibits nonexponential electron spin-lattice relaxation transients at low temperature. As previously reported, the tetranuclear Mn complex in PSII significantly enhances the spin-lattice relaxation of YD. Read More
J Chem Phys 2012 Aug;137(5):054503
Biophysical Chemistry, Lund University, POB 124, SE-22100 Lund, Sweden.
The frequency dependence of the longitudinal relaxation rate, known as the magnetic relaxation dispersion (MRD), can provide a frequency-resolved characterization of molecular motions in complex biological and colloidal systems on time scales ranging from 1 ns to 100 μs. The conformational dynamics of immobilized proteins and other biopolymers can thus be probed in vitro or in vivo by exploiting internal water molecules or labile hydrogens that exchange with a dominant bulk water pool. Numerous water (1)H and (2)H MRD studies of such systems have been reported, but the widely different theoretical models currently used to analyze the MRD data have resulted in divergent views of the underlying molecular motions. Read More
J Chem Phys 2004 Dec;121(23):11927-41
Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, x5016LAE Córdoba, Argentina.
By means of the Jeener-Broekaert nuclear magnetic resonance pulse sequence, the proton spin system of a liquid crystal can be prepared in quasiequilibrium states of high dipolar order, which relax to thermal equilibrium with the molecular environment with a characteristic time (T1D). Previous studies of the Larmor frequency and temperature dependence of T1D in thermotropic liquid crystals, that included field cycling and conventional high-field experiments, showed that the slow hydrodynamic modes dominate the behavior of T1D, even at high Larmor frequencies. This noticeable predominance of the cooperative fluctuations (known as order fluctuations of the director, OFD) could not be explained by standard models based on the spin-lattice relaxation theory in the limit of high temperature (weak order). Read More
J Magn Reson B 1994 Oct;105(2):129-36
Department of Chemistry and Biochemistry, Sinsheimer Laboratories, University of California, Santa Cruz 95064.
The validity of the formalism for the off-resonance rotating-frame spin-lattice relaxation experiment applicable to spin-1 quadrupolar nuclei was experimentally examined by considering two model systems, deuterated glycerol and deuterated benzene in castor oil, at different temperatures. When appropriately implemented, the deuterium off-resonance rotating-frame spin-lattice relaxation experiment provides spectral-intensity-ratio-dispersion data which agree remarkably well with those predicted by the theoretical formalism. The assumption of quadrupolar relaxation as the dominant relaxation mechanism, and rigid-rotor isotropic tumbling, permits the assessment of rotational diffusion behavior, i. Read More