AMMRL: intermittent streaks

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Hello Everyone;
   
    Recently an intermittent problem has raised its ugly head--vertical 
noise streaks.
Curiously, in both an HNCACB and in a CPMG Relaxation Dispersion experiment
(by different users on different protein samples) the most intense 
streak appears at
about 7.7 ppm; in the first case there is a less intense band at about 
6.25 ppm, and in
the second case a less intense band at about 8.1 ppm.  In a series of 
experiments run
this weekend (by a  yet different user on a different sample) there is 
a  strong band
at about 6.4 ppm and a weaker one at about 7.5 ppm in a  CBCA(CO)NH; 
there is
also streaking in an HNCACB, but not in a methyl tocsy.  I have NOT been 
able to
duplicate it in 2D faces of a CBCA(CO)NH by lowering the legs (thinking 
it might
be due to vibrations) or by increasing the cooling air and/or VT gas 
flow (when high
enough there IS noise in the amide region, but not the streaks 
previously observed).
    I am not sure, of course, but my guess is that it is not related to 
the lock or temperature
fluctuations (although I certainly could be wrong).  Any suggestions for 
troubleshooting
would be most welcome!

    Thanks,
    Karl Koshlap
    School of Pharmacy
    University of North Carolina

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