Hi David,
Many thanks for your reply but maybe I didn't state the problem clearly, actually the problem is in Bruker's pulse program not in the NMRFAM's. Those of NMRFAM's didn't give me trouble.
And for bruker's pulse program, in principle they don't require phase correction along 13C dimension, but on the base the delays are correctly calculated ( to 0 dwell time delay here). What I'm not sure is whether their pulse program actually calculate the correct delay and take into account the evolution of magnetization during the flanking 90 dgr pulses ( as in page 122 of Cavanagh J et al.'s Protein NMR Spectroscopy). I'm afraid they didn't.
I checked the setting of delays, actually they are hard-wired into the pulse programs in Bruker's.
My speculation is that the miscalculation of Bruker pulse program leads to these phase problems and it's not easy to correct because they appear to require phase correction of different signs for different peaks, please take your time to have a look at
http://mbalster.cwru.edu/questions/phasing.jpg (1D slices not to the same scale)
the phase distortion of the peak around 65ppm(13C) at the left side is different from the phase distortion of the peak around 55ppm(13C) at the right side. They require phase correction parameters of different signs. How can this be compromised?
Yufeng
======= At 2004-02-17 15:32:00 you wrote =======
>
>One possibility is a first delay time difference between the two sequences. You may have to linear predict the first point (or first couple points) in the 13C dimension. Alternatively, you may need 90,-180 (or -90,180, or x, -180 or x, 180) phase correction in 13C if there is a half-dwell delay. (the important thing is +/- 180 first order phase correction; the zero order doesn't matter much). Judging from your picture, it looks like you need some first order phase correction. Are you using LP or 90, -180 phase correction in your processing of NMRFAM sequences? most of them, if cnst0>0, will use 90-180 phase corrections, while the bruker sequence might not.
>
>Is it possible that you've mis-set one of the delays or increments (esp. in20)?
>
>Phasing indirect dimensions is usually not too hard in NMRPipe; read in Y or Z strips at locations where there is a peak at either end, and adjust zero and first order phases to get absorption.
>
>Regards,
>David Horita
>
>> -----Original Message-----
>> From: Yufeng [mailto:CrystalAtom@yahoo.com]
>> Sent: Tuesday, February 17, 2004 1:53 PM
>> To: BUM
>> Subject: Bruker pulse program phasing problem
>>
>>
>> Dear Bruker Users,
>>
>> Sorry for possible cross-posting, I'm just eager to know the
>> answer soon.
>>
>> I was using pulse program for Bruker from Wiscosin for a long
>> time, recently I tried the Bruker standard pulse program in
>> XwinNMR V3.5 but got some trouble in processing, especially
>> the phasing of 13C dimension. For example, the hncocacbgp2h3d
>> spectra gives some dispersive tail along 13C dimension that
>> can not be corrected easily. This has not been a problem for
>> me when I use
>> pulse program from Wiscosin.
>>
>> To show how it looks, please have a look at the H-C
>> projection plane at
>> http://mbalster.cwru.edu/questions/hncocacb2d3h_hc.jpg
>> No phase correction was carried out along 13C dimension.
>>
>> I tried to process in both Felix 2002 and nmrPipe and the
>> results are the same.
>>
>> I looked up into the hncocacbgp2h3d then found the phasing
>> evolution during the pulses bracing the 13C evolution is not
>> corrected during delay calculation, (p13:sp8 ph2):f2 and
>> (p13:sp2 ph9):f2 in this case, though they used time-reversed
>> shaped pulse to revert the magnetization.
>>
>> I was just wondering whether this is the cause for the
>> additional phase correction required (which is actually not
>> easy to complish) and if this is the case, did you people
>> seldom use pulse programs from
>> XwinNMR rather from other sources, or use modified versions
>> of the Bruker pulse programs?
>>
>> And I noticed several other pulse programs were written in
>> the similar way and gave similar results.
>>
>>
>> Sincerely yours
>>
>> Yufeng
>> 2004-02-17
>> ????????????????CrystalAtom@yahoo.com
>>
>>
= = = = = = = = = = = = = = = = = = = =
Yufeng Tong
Dept. Physiol. & Biophys.
Case Western Reserve Univ.
Cleveland, Ohio 44106
Tel: (216)368-8654 (O)
_______________________________________________________________________________
Life is an everlasting game of Weiqi(igo, baduk).
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