General implementation of the ERETIC method for pulsed field gradient probe heads.

A capacitive coupling between a secondary radiofrequency (rf) channel and the gradient coil of a standard commercially available high resolution NMR spectrometer and probe head is described and used to introduce a low level exponentially damped rf signal near the frequency of the primary rf channel to serve as an external concentration standard, in analogy to the so-called ERETIC method. The stability of this inexpensive and simple to implement method, here referred to as the Pulse Into the Gradient (PIG) approach, is superb over a 14-h period and both gradient tailored water suppression and one-dimensional imaging applications are provided. Since the low level signal is introduced via the pulsed field gradient coil, the coupling is identical to that for a free induction signal and thus the method proves to be immune (within 5%) to sample ionic strength effects up to the 2M NaCl solutions explored here.

Towards rapid throughput NMR studies of full wine bottles.

A rapid throughput method for the quantitation of the oxidation level of intact full bottles of wine based on the 1331 water suppression pulse sequence is described. The ideal pulse sequence suppresses water in the (1)H nuclear magnetic resonance spectrum while uniformly and phase coherently exciting the resonances pertaining to ethyl alcohol at 1.1 ppm and oxidation products at 2.1 ppm. The anticipated results of the pulse sequence based on simulations are tested in small sample and full bottle standards and an application to the detection of wine spoilage in more than century old wine is provided.

Explaining the inhibition of glyoxalase II by 9-fluorenylmethoxycarbonyl-protected glutathione derivatives.

In an effort to probe the inhibition of glyoxalase II (GLX2-2) from Arabidopsis thaliana, a series of N- and S-blocked glutathione compounds containing 9-fluorenylmethoxycarbonyl (FMOC) and Cbz protecting groups were synthesized and tested. The di-FMOC and di-Cbz compounds were the best inhibitors of GLX2-2 with K(i) values of 0.89+/-0.05 and 2.3+/-0.5 microM, respectively. The removal of protecting groups from either position resulted in comparable, diminished binding affinities. Analyses of site-directed mutants of GLX2-2 demonstrated that tight binding of these inhibitors is not due to interactions of the protecting groups with hydrophobic amino acids on the surface of the enzyme. Instead, MM2 calculations predict that the lowest energy structures of the unbound, doubly substituted inhibitors are similar to those of a bound inhibitor. These studies represent the first systematic attempt to understand the peculiar inhibition of GLX2 by N- and S-blocked glutathiones.