DOSY Experiments - Emory University

Pulse sequences have been added to support experiments on biological samples in H2O/D2O
solvent at limited concentrations. They use either the well known watergate 3-9-19
(Dbppste_wg) or excitation sculpting (DgcsteSL_dpfgse) schemes for solvent suppression.
For best results they may be combined with solvent presaturation as well as with digital solvent
filtering during data processing.
There are pulse sequences that allow convection compensation (Dbppste_cc, DgsteSL_cc,
DgcsteSL_cc and Dpfgdste_cc) or can be used to experimentally verify whether convection
is present and might distort the diffusion data.
The Doneshot sequence has been modified to allow diffusion experiments in concentrated
samples or neat liquids. The flip angle of the first pulse has been made user enterable to
overcome problems associated with radiation damping.
The package contains pulse sequences that allow running phase sensitive 3D-DOSY
experiments (Dgcstehmqc_ps, Dbppste_ghsqcse, Dhmqcidosy). The first two sequences
were developed and tested on 15 N-labeled peptide/protein samples. The Dbppste_ghsqcse
sequence was taken over from the BioPack package and has been made VnmrJ 3.0 compatible.
A new approach of pulse sequence programming of diffusion sequences called inclusive-DOSY
or I-DOSY has recently been published by Gareth Morris and Matthias Nilsson. Instead of
concatenating the NMR and the diffusion pulse sequence, they share delays for magnetization
transfer and diffusion. They have higher inherent sensitivity than conventional sequences and
allow optional convection compensation with no sensitivity penalty. The Dcosyidosy and the
Dhom2djidosy are absolute value sequences, while the Dhmqcidosy sequence allows
acquiring phase sensitive data.
The Doneshot_nugmap pulse sequence is provided to accurately calibrate the gradient strength
of the probes used for diffusion experiments as well as to map the spatial non-linearity of the
gradient coil. The results of this calibration are stored in the corresponding probe file and are
activated at any consequent diffusion setup and may be taken into account at data processing.
Two macros showdosyfit and showdosyresidual provide graphical display of the quality of the fit
for each individual peak in DOSY processing. That allows identifying systematic errors or may
help to exclude erroneous data points from the analysis.
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