Hugh L. Eaton

Rapid acquisition of NOE difference spectra. The relative merits of transient versus driven experimental protocols

Abstract The effect of substantial reduction in the preparatory waiting period employed in the collection of nuclear Overhauser effect spectra has been examined experimentally for systems near the extreme narrowing limit with particular emphasis on the truncated driven and selective inversion-recovery techniques which do not require a long evolution period. Over short evolution periods the NOE buildup rate should be directly proportional to the cross-relaxation rate by either method. The transient NOE experiment still provides accurate ratios of cross-relaxation rates even when the waiting time is less than T 1 . Comparisons of fractional enhancement data for prostaglandin F 2 α and four other prostanoids obtained by standard (long waiting time) and rapid acquisition protocols indicate that the rapid acquisition method can, with the proper choice of integration standards, be used for quantitative studies.

Time dependence of 13C-13C magnetization transfer in isotropic mixing experiments involving amino acid spin systems

Abstract The time dependence of 13 C- 13 C coherence transfer for the aliphatic portions of amino acid side chains has been examined by calculating ideal coherence-transfer functions. These results were compared to experimentally determined cross- and diagonal-peak intensities obtained from a series of 2D 13 C TOCSY experiments acquired with 12 mixing times ranging from 0.0 to 34.2 ms on a mixture of uniformly 13 C-labeled amino acids. In general, the calculated coherence-transfer functions agreed. Unlike 1 H- 1 H TOCSY experiments, the time dependence of 13 C- 13 C coherence transfer for these spin systems is simple and well characterized due to the large and conformationally independent 13 C- 13 C spin-spin couplings. Spectra obtained at mixing times of 8, 14, 20, and 28 ms cover most features of the coherence-transfer functions such as vanishingly small cross peaks and local maxima and minima. These features, along with the fact that 13 C- 13 C coherence transfer takes place in times which are short compared to relaxation times typical for small proteins, make this experiment ideal for the assignment of protein 13 C spectra, which in turn aids in the 1 H NMR assignment.

Computer simulation of transient NOE experiments with short preparatory delays

Abstract Computer simulations of the transient NOE experiment in the small-molecule correlation time domain which explicitly include cycle-to-cycle truncation effects due to incomplete relaxation during the preparatory delay period are reported. Fixed-delay (rather than fixed cycle time) protocols provide data that yield longitudinal relaxation rates mgt readily. Either protocol can be used to determine NOE growth rates accurately even when cycle times are on the order of the T1 values of the spins examined. Methods for correcting for truncation errors and calculating cross-relaxation rates are presented and justified.

Isolation and characterization of the major glycosphingolipids from the liver of the rainbow trout (Oncorhynchus mykiss): Identification of an abundant source of 9-O-acetyl GD3

The carbohydrate structures of the major glycosphingolipids from the liver of the rainbow trout Oncorhynchus mykiss have been examined. We have isolated and identified four major neutral (glucosylceramide, galactosylceramide, lactosylceramide, and globoside) and five acidic (sulfatide, GM3, GM2, GD1a, and 9-O-Acetyl GD3) glycosphingolipids from trout liver. They have been characterized by 1H nuclear magnetic resonance spectroscopy, methylation analysis, fast atom bombardment mass spectrometry, and specific monoclonal antibodies. Significantly, the relatively scarce ganglioside 9-O-acetyl GD3 was found to comprise approximately 23% of the total ganglioside content of normal rainbow trout liver. 9-O-Acetyl GD3 is, however, abundant in human melanoma and as such, trout liver may be a suitable source of this antigen.

Accentuated selective population transfer difference spectroscopy: a new method for revealing hidden NMR resonances.

Abstract Block difference FID accumulation with an initial selective decoupler pulse alternately placed at the high and low frequency lines of a multiples provides, upon transform, a difference spectrum that shows only those other multiplets that are scalar coupled to the probed resonance with full retention of all splittings for the multiplets so revealed.