Edward W. Randall

Betaine metabolism in human neonates and developing rats

Proton nuclear magnetic resonance spectroscopy has been used to demonstrate the presence of high concentrations of betaine (up to 0.75 mol/mol creatinine) in the urine of normal healthy human neonates. Betaine is not normally excreted in adults. Excretion of betaine from birth to 7 days old was monitored. The excretion of betaine in rats from 21 days after birth to 40-45 days old was also monitored. A peak in excretion in the rats of 1.5-3 mol/mol creatinine occurred between days 30-35. The presence of a high concentration of betaine in the urine is unlikely to be caused by a relative lack of betaine homocysteine methyl transferase activity compared with adults but may relate to the disposal of dietary choline during development.

The hardening of Portland cement studied by NMR stray-field imaging

Hydration and hardening processes of Portland cement (type I) were studied by analysis of the one-dimensional projections (profiles) obtained periodically with the stray-field imaging technique over two days. The influence of additives, such as gypsum, in Portland cement (type IA) was also investigated. The decay of the signal intensity as a function of time was found to be bi-exponential for type I and mono-exponential for type IA.

1 H and 13C nuclear magnetic resonance spectra and X-ray crystal structure of [1-methyl-3-ethyl-(σ-1,3-h2,π-1,2,3-h3)-allyl]nonacarbonyltriruthenium: the allyl group as a five-electron donor

The reaction of cis,trans- or trans,trans-hexa-2,4-diene and Ru3(CO)12 is shown, by 1H and 13C n.m.r. spectra and X-ray crystal structure to give a product in which the diene ligand has undergone a skeletal rearrangement producing a π-allyl group, a metal hydride bond, and two metal–carbon σ-bonds.

Heteronuclear double resonance: Theoretical description of intensity effects in A(X2) and A(X3) systems

Abstract The line intensities in an A(X n ) double-resonance spectrum appear anomalous, sometimes even with transitions in emission. These intensities are the result of the population distribution among the levels of the effective double-resonance Hamiltonian in rotating axes. Two factors determine these populations: the tilt effect (the result of the tilting of the effective field in the rotating axis) and the relaxation effect. These effects are demonstrated for various examples and it is shown how different relaxation mechanisms alter the line intensities.

Stray-field imaging of quadrupolar nuclei of half integer spin in solids.

A report is presented on the observation of Hahn echoes from the following quadrupolar nuclei of half integer spin (I) in polycrystalline solids in the large static magnetic field gradient (37.5 T/m) which exists in the fringe field of a superconducting solenoid: 7Li, 23Na, 11B, 65Cu (I = 3/2); 27Al (I = 5/2); 51V, 59Co (I = 7/2); and 115In (I = 9/2). 23Na echo-trains from NaCl (with non-selective excitation) and from Na2SO4 (with selective excitation) are compared quantitatively for two different RF pulse sequences: 90x-(tau-90y-tau-echo-)n and 90x-(tau-90x-tau-echo-)n. The signals obtained from RF pulses corresponding to non-selective 90 degrees pulses were shown to be quantitative, whereas in the selective case smaller signals were obtained since only the central transition contributed. The loss of signal from this cause can be distinguished from small signals resulting from low density of nuclei by use of the second sequence. A 7Li image obtained from LiF in a cylindrical glass-vial is shown.

The elimination of magnetic susceptibility distortions in the imaging of liquids in solids : the stray field imaging technique

The effects of magnetic susceptibility, X, and its variations within a host lattice on the NMR responses of a contained liquid are well known ( 2 ) . Examples of lattices that one may wish to investigate are wood, rocks and minerals, clays, and soil. The liquid of interest is usually water or oil. Local differences in x produce a spatially dependent BO, i.e., BO( r). The largest NMR effects naturally come from samples in which the range of BO( r) is greatest and most commonly this occurs when the lattice contains paramagnetic centers for which X is large. The effects are expected to be observable even when the lattice contains only diamagnetic centers for which the range of BO( Y) is very much smaller (2). BO( Y) results in a line broadening of the NMR response which is given by

Determination of some long-range carbon couplings from PMR spectra of 15N-pyrrole

Abstract The high resolution 100 MHz PMR spectrum of an 15 N-pyrrole sample has been analyzed. The spectrum contains transitions from species (I), with only 12 C as the carbon isotope, and species (II) and (III) each containing one 13 C in natural abundance in the α or β-positions, respectively. Iterative analyses of the AA′BB′CX spectrum with 109 assigned proton transition of (I) have produced values of the proton-proton and the nitrogen-proton couplings in good agreement with previous results. The use of both 13 CH satellites and several 12 CH lines of (II) has given the magnitudesof the carbon-proton couplings: 1 J(C 2 H 2 ) = 184.18 ± 0.02 Hz; 2 J (C 2 H 3 ) = 8.50 ± 0.08Hz; 3 J (C 2 H 4 ) = 7.46 ± 0.06 Hz; and 3 J (C 2 H 5 ) = 6.85 ± 0.10 Hz. The high-field 13 CH satellite and several 12 CH lines of (III) have produced the long-range carbon-proton couplings: 2 J (C 3 H 2 ) = 8.43 ± 0.08 Hz; 2 J (C 3 H 4 ) = 4.69 ± 0.10 Hz; and 3 J (C 3 H 5 ) = 7.31 ± 0.06 Hz. In addition, the isotope effect of 0.14 ± 0.02 Hz on the proton chemical shift in the α position.

A convenient method for calibration of the pulse-length in high field-gradients using Hahn echo-trains

A new method is presented for calibration of the pulse-length in the case that the sample, which can be either a liquid or a solid, is placed in a high field-gradient such as it experiences in the stray-, fringe-field of a solenoid. The method employs a pulse-train, with a constant phase, of the form alpha X-tau-(alpha X-tau-echo-tau-)n. This produces Hahn echoes which have variable phase in the form of phase-alternations along the echo-train. For alpha = 90 degrees the relative phase-sequence in degrees is (0, 0, 180, 180), and we may characterise this by m = 2, since there are two signals of one phase in each group. For other cases with these phase angles (0 and 180) but different numbers, m, of signals with opposite phase, we have alpha = 180/m, where m is an integer.

Magnetic susceptibility effects in imaging: Distortion-free images of plant tissue in soil

Magnetic susceptibility effects (MSE) in NMR spectra are well known, and indeed the NMR technique has frequently been applied to measure magnetic susceptibility. In the case of imaging, MSE can lead to image distortion when the sample is heterogeneous. We have performed experiments on a soil sample (iron content approximately 2%) containing plant tissue which gave a NMR signal that was spread over about 15 kHz in the 1H spectrum. We present some results from a 128 x 128 x 128 3D 1H image (voxel size = 150 x 150 x 150 micron3) generated by the stray field imaging (STRAFI) technique in which the use of a 5 kG cm-1 magnetic flux density gradient reduced the magnetic susceptibility distortion to less than 10 microns.

A 13C Nmr investigation of stereochemical non rigidity in hydrido olefinic carbonyl clusters of ruthenium

Abstract 13C n.m.r. spectra of hydrido olefinic carbonyl clusters of ruthenium show that localized scrambling of the carbonyls occurs with different energy barriers which depend on the nature of the bonding between the ligand and the metal cluster and on the nature of the substituents in the olefinic chain. Resonances of carbons “sigma” bonded to one ruthenium and “pi” bonded to a second one are in the lowfield region (198-162 ppm).