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Has anyone added a pulse scheme for cross saturation to their TROSY for Bruker platform?

Could you share a pulse sequence if you have one?

Thanks!

asked Aug 24 '09 at 16:46

roseyp's gravatar image

roseyp
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updated Aug 27 '09 at 00:16

Evgeny%20Fadeev's gravatar image

Evgeny Fadeev
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Hi roseyp,

STD based experiments are straightforward and easy to implement. Example, for a STD-HSCQ the basic blocks will be ,

1) Insert a loop for saturation pulse,

2) perform the HSQC/TROSY as usual

3) modify the receiver phase to subtract the 'on' resonance expt from the 'off' resonance experiment.

The following implementation assumes a Bruker pulse sequence,

Given an experiment with the receiver phase (ph31: 0 2 2 0 1 3 3 1 ) the following approach can be adopted,

1 zg

2 d1 fq2:f1 ; switch the frequency to on/off using a fqlist 2

20u pl2:f1 ; power level for gaussian saturation

3 (p11:sp1 ph20):f1

d15

lo to 3 times l7 ; decide saturation time by setting l7

4 20u fq1:f1 ; switch the on frequency back to water using a fqlist 1

20u pl1:f1

--- insert your sequence of interest ----

--- in the receiver phase cycle add another segment (highlighted in bold below) with phase incremented to 180 ----

--- e.g. ph31: 0 2 2 0 1 3 3 1 2 0 0 2 3 1 1 3 ---

--- perform the experiment with twice the number of scans, compared to the original sequence ( 2* NS) or set the NS equal to the number of entry in Ph31, i.e. 16 or its multiples in the above example.

The pulse sequence is ready to use after creating two frequency lists namely fq1list and fq2list, e.g. fq2list ( first line contains spectrometer base/carrier frequency with the letter O in front; second line to last lines contains on/off frequency in order)

O 900.00

90000

90000

90000

90000

90000

90000

90000

90000

-6030

-6030

-6030

-6030

-6030

-6030

-6030

-6030


as you can see the first 8 expt are off-resonance with irradiation at 100 ppm or 90k Hz, the following 8 expts are on resonance at -6030 Hz or -2 ppm. This sequel of off/on resonance has a correspondence with the receiver phase which we have modified such that the first eight expts are + ve and the last eight are -ve ( inverted by 180 phase shift ). When both the set (+:off and -ve:on) are added up as the scans are averaged, we end up with a STD difference spectra.

(The on-resonance is calculated with respect to the water resonance set at 0Hz. E.g if we want to irradiate at a on-resonance of -2ppm and if the water is set as 4.7ppm (o1p). Then the on-resonance value should be, -(4.7+|-2|)= -6.7 ppm = -6030 Hz). alternatively, if we want to set the on-resonance at 12 ppm, +(12-4.7)= 7.3 ppm = 6570 Hz ).

fq1list ; contains the water frequency at 0 Hz

O 900.00

0.0


you have to set the parameter o1p as 4.7 or the calibrated water resonance in ppm.

Best regards, Jana

link

answered May 17 '13 at 22:46

Jana's gravatar image

Jana
31

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