The relationship between the transverse and longitudinal nuclear magnetic resonance relaxation rates of muscle water.

Whole frog sartorius and gastrocnemius muscles were incubated in Ringer's solutions, either unenriched or enriched with H2 17Oor 2D2O. Subsequently, the rates of transverse (1/T2) and of longitudinal (1/T1) nuclear magnetic relaxation were measured for 17O, 2D, and 1H at room temperature and at 8.1 MHz. The ratio (T1/T2) for 17O was measured to be approximately 1.5-2.0, close to the value roughly estimated from the Larmor frequency dependence of 1/T1 alone over the range 4.3-8.1 MHz. On the other hand (T1/T2) for 2D and 1H were both measured to lie in the range 9-11. Insofar as the entire 17O signal was detected, the data indicate the presence of an exchange mechanism between the major fraction of intracellular water and a minor fraction characterized by enhanced rates of relaxation. Possible molecular mechanisms are presented.     

Nuclear magnetic resonance relaxation times and plasmalemma water exchange in ivy bark

Measurement of nuclear magnetic resonance (NMR) relaxation times (transverse [T₂] and longitudinal [T₁]) for Hedera helix L. cv. Thorndale (ivy) bark water indicates the presence of at least two populations of water with different relaxation characteristics. One population of water with short T₂ and T₁ was found to be composed of both hydration water and extracellular free water. The second population of water with long T₂ and T₁ was identified as intracellular bulk water.     

Study of anisotropy in nuclear magnetic resonance relaxation times of water protons in skeletal muscle.

The anisotropy of the spin-lattice relaxation time (T1) and the spin-spin relaxation times (T2) of water protons in skeletal muscle tissue have been studied by the spin-echo technique. Both T1 and T2 have been measured for the water protons of the tibialis anterior muscle of mature male rats for theta = 0, 55, and 90 degrees, where theta is the orientation of the muscle fiber with respect to the static field. The anisotropy in T1 and T2 has been measured at temperatures of 28, -5 and -10 degrees C. No significant anisotropy was observed in the T1 of the tissue water, while an average anisotropy of approximately 5% was observed in T2 at room temperature. The average anisotropy of T2 at -5 and -10 degrees C was found to be approximately 2 and 1.3%, respectively.     

Nuclear magnetic resonance study of muscle water protons in muscular dystrophy of chickens

Using the pulsed nuclear magnetic resonance (NMR) spectroscopy, the spin-lattice (T1) and the spin-spin (T2) relaxations times of water protons from samples of pectoralis major muscles of normal (line 412) and homozygous dystrophic (line 413) chickens were measured. Both the T1 and T2 were significantly increased (P less than 0.05) in the dystrophic muscles. The mean values of the relaxation times are given +/- S.D. The T1 values were 654 +/- 22 msec in normal and 692 +/- 41 msec in dystrophic muscles. The T2 values for normal and dystrophic muscles were 39 +/- 4 msec and 52 +/- 7 msec, respectively. Although the water content of dystrophic muscles (78.9 +/- 0.6%) determined by gravimetric methods was significantly higher than normal muscles (74.9 +/- 1.1%), this difference in tissue hydration could not explain quantitatively the increase of T1 and T2 values in the dystrophic muscles. The results of the measurements of the relaxation times seem to suggest that there are changes in the composition and/or conformational state of the proteins.     

Nuclear magnetic resonance study of spin relaxation and magnetic field gradients in maple leaves.

1H Nuclear magnetic resonance techniques were used to measure the distributions of spin-spin relaxation times, T2, and of magnetic field gradients in both the chloroplast and nonchloroplast water compartments of maple leaves (Acer platanoides). Results showed that encounters between water molecules and membranes inside chloroplasts provide an inefficient relaxation mechanism; i.e., chloroplast membranes interact weakly with water molecules. Gradient measurements indirectly measured the sizes of chloroplasts by showing that water in the chloroplasts is confined to small compartments a few microns in diameter. A comparison between measured gradients and gradients calculated for a model leaf indicated that chloroplasts are somewhat more likely to occupy positions along cell walls adjacent to air spaces, but also they may be found in the interiors of cells.     

Nuclear magnetic resonance studies of forearm muscle in Duchenne dystrophy.

The forearms of six patients with Duchenne dystrophy were examined by the painless and non-invasive technique of high-resolution nuclear magnetic resonance spectroscopy. The phosphorus spectrum was abnormal in that the ratios of phosphocreatine to adenosine triphosphate and to inorganic phosphate were reduced. Absolute quantification under the conditions of this experiment was not possible but it was probable that in dystrophy the concentration of phosphocreatine in muscle was appreciably reduced. A signal in the phosphodiester region of the spectrum was recorded consistently in patients with dystrophy but not in controls. The intracellular pH of the muscle in the dystrophic patients was abnormally alkaline. The clinical application of nuclear magnetic resonance spectroscopy remains to be proved, but it appears to be a promising non-invasive technique for investigating biochemical abnormalities of muscle disease.     

Nuclear magnetic resonance analysis of water in natural and deuterated mouse muscle above and below freezing.

Measurements of absolute proton signal intensities, free induction decays, spin-spin relaxation times, and local fields in the rotating frame in natural and fully deuterated mouse muscle at five temperatures in the range 293-170 K are reported. The analysis is carried out at three time windows on the free induction decay. The contribution to the magnetization from protons on large molecules and water are analyzed.     

Nuclear magnetic resonance relaxation in cross-linked lysozyme crystals: an isotope dilution experiment.

Nuclear magnetic resonance (nmr) relaxation times are measured for water protons in cross-linked lysozyme crystals below the freezing event as a function of the mole fraction of protons in the water phase. Proton longitudinal nmr relaxation in these samples is nonexponential and the slow longitudinal relaxation component becomes slower linearly with decreasing proton mole fraction in the water. The data are analyzed using a cross relaxation model that eliminates the necessity of postulating long residence times for water molecules in the domain of the protein. The observed isotope dilution behavior is consistent with the cross relaxation model. The deuterium nmr relaxation is also reported for deuterium oxide in the cross-linked protein crystal sample below the freezing event and the relaxation is shown to be accurately exponential.     

Nuclear magnetic resonance measurement of skeletal muscle: anisotrophy of the diffusion coefficient of the intracellular water.

The anisotropy of the spin-diffusion coefficient Ds of water protons in skeletal muscle has been studied by pulsed NMR methods. The mid-portion of the tibialis anterior muscle of mature male rats was placed in a special sample holder by means of which the muscle fiber orientation theta relative to the diffusion direction could be varied over the range 0 degrees less than or equal to theta less than or equal to 90 degrees. The value of Ds(theta) was determined for theta = 0 degrees, 45 degrees, and 90 degrees. The measured anisotropy Ds(0)/Ds(90) was 1.39, and the value of Ds(0) was 1.39 X 10(-5) cm2/s. These results are interpreted within the framework of a model calculation in which the diffusion equation is solved for a regular hexagonal network similar to the actin-myosin filament network. The large anisotropy, and the large reduction in the value of Ds measured parallel to the filament axes lead to two major conclusions: (a) interpretations in which the reduction in Ds is ascribed to the effect of geometrical obstructions on the diffusion of "free" water are ruled out; and, (b) there is a large fraction of the cellular water associated with the proteins in such a way that its diffusion coefficient is substantially reduced.     

Nuclear magnetic spin-lattice relaxation of water protons caused by metal cage compounds.

The nuclear magnetic spin-lattice relaxation rates of water protons are reported for solutions of manganese(II), copper(II), and chromium(III) cage complexes of the sarcophagine type. As simple aqueous solutions, the complexes are only modest magnetic relaxation agents, presumably because they lack protons on atoms in the first-coordination-sphere protons that are sufficiently labile to mix the large relaxation rate at the metal complex with that of the bulk solvent. The relaxation is approximately modeled using spectral density functions derived for translational diffusion of the interacting dipole moments with the modification that the electron spin relaxation rate is directly included as a contribution to the correlation time. In all cases studied, the electron spin relaxation rate is sufficiently large that it contributes directly to the water-proton spin relaxation process. The poor relaxation efficiency of the cage compound may, however, be improved dramatically by binding the complex to a protein. The efficiency is improved even further if the rotational motion of the protein is reduced drastically by an intermolecular cross-linking reaction. The relaxation efficiency of the cross-linked protein-cage complexes rivals that of the best first-coordination-sphere relaxation agents like [Gd(DTPA)(H2O)]2- and [Gd(DOTA)(H2O)]-.     

Nuclear magnetic resonance investigation of the state of water in protein solution.

The line width of the NMR signal of water protons in solutions of native actomyosin and actomyosin denatured by heat, acetone or urea was measured over the temperature range from -10 degrees to below the freezing point. The line widths of the water band which increased exponentially with decreasing temperature were compared with each other and also with those of the corresponding control solution without actomyosin. The line broadening observed for native actomyosin solution on lowering the temperature was significantly smaller than that for heat-denatured actomyosin solution. This difference implies that this signal is sensitive to conformational perturbations of the protein. In addition, the temperature dependence of the line width for heat-, acetone-, or urea-denatured actomyosin solution was similar to that for the corresponding control solution. These phenomena can be interpreted in terms of the state of water associated with the hydrophobic and hydrophilic residues. Similar NMR studies of actomyosin solution containing dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) showed that DMSO and DMF prevent the formation of ice crystals until about -70 degrees, suggesting that the cryoprotective effects of DMSO and DMF are due to the change in the state of water described above. These differences in temperature dependence between the sample and control solutions are well-correlated with the viscosity of the solution. This correlation is useful for elucidation of the mechanism of the protein denaturation.     

Nuclear magnetic resonance relaxation time and self-diffusion coefficient measurements of water in frog ovarian eggs (Rana pipiens)

Self-diffusion coefficient measurements of water in untreated ovarian eggs of Rana pipiens using nuclear magnetic resonance indicate that cytoplasmic water has reduced translational mobility compared with pure water. Using a simple two-state model, we find that ～67% is “relatively immobile.” Consideration of the nuclear magnetic resonance spin-lattice and spin-spin relaxation times indicates that the decreased mobility can largely be ascribed to hydration. Our value for the self-diffusion coefficient (6.8 × 10^?6 cm²/sec) is lower than those reported by other investigators using isotopic water exchange techniques on frog eggs chemically treated to remove the membrane. However, the results reported here are in agreement with unpublished data on untreated frog eggs implying that chemical treatment has modified the cytoplasm in some manner.