Dear Colleagues,
We recently experienced the loss of lock during triple res Biopack
experiments, e.g. gNhsqc and other backbone assignment experiments. We start
with the lock as high as 95-100 and the gradients knock it down, fluctuating
between 50 and 70. At some point during the run the lock drops suddenly (not
gradually) and is lost.
This is an Inova 600 with a triple res HCN probe with xyz gradients, vintage
2003. The gradients connect to the probe though pins at the bottom of the
upper barrel.
The protein sample is 20 mM phosphate, 150 mM salt, 10% D2O, nothing unusual
about it.
The lock itself is stable, there is no problem with a locked sample over
time. Gradient shimming seems OK.
An overnight watergate run is fine, even with gradient strengths comparable
to the triple res ones.
I did not see any damaged/broken gradient connections in the upper barrel.
But I did not cut the heat shrinks for a better look.
I somehow think that the problem is related to a gradient problem, with
noise leaking out of the gradient amplifier affecting the lock. But I may be
wrong.
Please share any related experience and thoughts. I will summarize.
Thanks,
Lazaros Kakalis
Rutgers University at Newark
Department of Chemistry
Olson Laboratories
73 Warren Street
Newark, NJ 07102-1811
Tel: (973) 353-5040
Fax: (973) 353-1264
kakalis_at_andromeda.rutgers.edu
Received on Wed Dec 05 2012 - 07:03:35 MST