CSSF-TOCSY for Bruker (Dusan Uhrín et al.)

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Basic facts about CSSF-TOCSY

Synopsis: CSSF - selective 1D TOCSY pulse sequence

Family: TOCSY

Code authors:  Dusan Uhrín,  Tran Nghia,  Philip T. Robinson

Copyright: University of Edinburgh, Biomolecular NMR group

Introduction

The CSSF-TOCSY is a pulse sequence developed by Dusan Uhrín et al. It is a improved 1D version of 1D TOCSY for Bruker (selmlgp.2) using excitation sculpting technique with pulsed field gradients (PFG) and a chemical shift selective filter (CSSF) with constant time (CT).

This pulse sequence allows to selectively excite overlapping signals of hydrogens with chemical shift difference from 2 Hz. the CSSF can be used as a building block for others 1D experiments that need excitation of overlaped signals.

Delays

d1 - recycling delay (1-5 x T1) - [2 s]

d9 - mixing time (the value depends on how many step of magnetization transfer will desire. For 1D COSY type spectra, use 20-30 ms. For further steps can be used to transfer up to 200 ms.) - [120 ms]

d16 - gradient recovery delay (depends on the probe) may be on the order of 100-500 μs. - [120 ms]

d23 - CSSF delay - [5 μs]

d24 - maximum duration of the CT-CSSF (optional. use if -DCT is enable)

Carrier frequencies

O1 (or O1P for the value in ppm) is the carrier frequency used for the hard pulses.

Hard RF pulses

p1 - ¹H 90^o pulse at power level pl1. p2 is calculed automatically based in p1

Hard pulses are applied at O1 (or O1p) carrier frequency.

Selective RF pulse

There is one shaped selective pulse with the following adjustible parameters:

Note: pl0 must be at 120.

• p13 - length (default 50 ms, but generally length should be chosen according to desired selectivity)
• sp2 - power level
• spnam2 - waveform file name (default Crp40.1000 - gaussian pulse with 1000 steps.

Gradient pulses

• p16 (default 1 ms) - length used for the gradient pulses gp1 and gp2
• gp1, gp2, gp3 and gp4 strengths of the two gradient pulses.
• gpnam1, gpnam2, gpnam3 and gpnam4- shapes of gradient pulses (default - SINE.100)

Suggested ratio of gp1/gp2/gp3/gp4 - 20/6/4/30

Processing Parameters

• EM - Exponential multiplication to reduce the noise from spectrum (usually 0.3)

Process the FID with command EM and FP (or use EFP - a combination of EM and FP command).

References

1. Robinson PT, Pham TN, Uhrín D. In phase selective excitation of overlapping multiplets by gradient-enhanced chemical shift selective filters. Journal of Magnetic Resonance 170(1):97-103, 2004. BibTeX [dusan2004]