Lateral diffusion of lipid probes in the surface membrane of human platelets. An electron-electron double resonance (ELDOR) study

Autobiography of James S. Hyde

The papers, book chapters, reviews, and patents by James S. Hyde in the bibliography of this document have been separated into EPR and MRI sections, and within each section by topics. Within each topic, publications are listed chronologically. A brief summary is provided for each patent listed. A few publications and patents that do not fit this schema have been omitted. This list of publications is preceded by a scientific autobiography that focuses on selected topics that are judged to have been of most scientific importance. References to many of the publications and patents in the bibliography are made in the autobiography.

Use of electron spin resonance spectroscopy of spin labels for studying drug-induced membrane perturbation

The use of electron spin resonance spectroscopy of spin labels is reviewed in the context of drug-induced membrane perturbation. The correlation between membrane perturbation and biological effects is also considered.

The effects of cholesterol on lateral diffusion and vertical fluctuations in lipid bilayers. An electron-electron double resonance (ELDOR) study

Electron-electron double resonance (ELDOR) and saturation-recovery spectroscopy employing 14N:15N stearic acid spin-label pairs have been used to study the effects of cholesterol on lateral diffusion and vertical fluctuations in lipid bilayers. The 14N:15N continuous wave electron-electron double resonance (CW ELDOR) theory has been developed using rate equations based on the relaxation model. The collision frequency between 14N-16 doxyl stearate and 15N-16 doxyl stearate, WHex (16:16), is indicative of lateral diffusion of the spin probes, while the collision frequency between 14N-16 doxyl stearate and 15N-5 doxyl stearate, WHex (16:5), provides information on vertical fluctuations of the 14N-16 doxyl stearate spin probe toward the membrane surface. Our results show that: (a) cholesterol decreases the electron spin-lattice relaxation time Tle of 14N-16 doxyl stearate spin label in dimyristoylphosphatidylcholine (DMPC) and egg yolk phosphatidylcholine (egg PC). (b) Cholesterol increases the biomolecular collision frequency WHex (16:16) and decreases WHex (16:5), suggesting that incorporation of cholesterol significantly orders the part of the bilayer that it occupies and disorders the interior region of the bilayer. (c) Alkyl chain unsaturation of the host lipid moderates the effect of cholesterol on both vertical fluctuations and lateral diffusion of 14N-16 doxyl stearate. And (d), there are marked differences in the effects of cholesterol on lateral diffusion and vertical fluctuations between 0-30 mol% and 30-50 mol% of cholesterol that suggest an inhomogeneous distribution of cholesterol in the membrane.

Lateral diffusion of lipids in membranes by pulse saturation recovery electron spin resonance

Short-pulse saturation recovery electron spin resonance methods have been used to measure lateral diffusion of nitroxide-labeled lipids in multilamellar liposomal dispersions. Nitroxides with 14N and 15N isotopes introduced both separately and together were used. Differential equations have been written and solved for complex saturation recovery signals involving several superimposed exponentials. The time constants contain various combinations of the spin-lattice relaxation time (T1e) for both isotopes, Heisenberg exchange rates, and nuclear spin-lattice relaxation times (T1n). Signals of high quality were fitted by Monte Carlo variation of the amplitudes and time constants. The reliability of the approach was tested extensively by verifying that (i) the predicted number of exponentials agreed with the experimental number, (ii) relaxation parameters that were determined were independent of the observed hyperfine transition, (iii) the time constants were independent of saturating pulse length, (iv) T1e and T1n do not change when Heisenberg exchange is changed by varying the concentration, and (v) Heisenberg exchange is indeed proportional to the concentration. It has been established that bimolecular collision rates over a wide range of conditions can be reliably measured using the methodology described here. The methods depend on the favorable match of bimolecular collision rates at micromolar concentrations to nitroxide spin-lattice relaxation probabilities.