howdy All
i am hearing mixed stories on how well shigemi tubes
work on bruker 500MHz HCN cryoprobes.
we have a new cryoprobe which functions very nicely
here, and i've done some 15N hsqc's (water flipbacks and
fast hsqc's, etc) w/o any modification from our
regular HCN probe experiments at 500MHz and up, in a
normal 500uLiter volume protein sample in a normal tube.
i am having trouble with shimming the shigemi tube
(sample volume < 250uLiter), however, and consequently
seeing much worse water suppression for these hsqc
experiments even though the concentration isn't low.
this same tube/sample shimmed adequately on other machines
and gave great spectra, so either i am having a bad shim
day or there's something about the cryoprobe that makes
it more difficult to shim these. does the higher Q
make it more particular about possible magnetic susceptibility
differences between the sample and the glass inserts?
if anyone out there (including Bruker applab people)
have some info on this, i'd appreciate some feedback.
i've heard someone say shigemi tubes work fine in
cryoprobes if the volume is high, but that sort of
defeats the purpose of using shigemi tubes in the
first place, right?
thanks much in advance,
john chung
biomolecular nmr labs
the scripps research institute
Received on Thu Oct 25 2001 - 16:44:02 MST