Reference_Readme
The selective TOCSY experiment shows coupled proton spin systems that are connected thru J-coupling.
Whenever there is a quaternary carbon the spin-system is broken and no correlations are seen. For example,
in Ethyl Benzoate below the CO2 group breaks the spins between the ethyl and the aromatic protons.
When the aromatic proton "C" is selected we see correlations to all other protons in its spin system.
However, now the Ethyl peak is removed. This provides a useful way of delineating assignments. It also allows
for identification of peaks which are maybe overlapped in the standard 1D 1H.
be sure to lock, shim and wobb before starting the data acquisition
1st acquire a normal 1D 1H and then run the selnoe expts
must use 500s as 400 can't handle such expts!
- rpar h1.bbo all - read in the parameter file for proton expt and run as normal..
- o1 - write this number down eg)2753
- now hover cursor over peak of interest in normal 1D 1H and note the frequency in Hz! To activate the cursor display r.cl. in window and display cursor information. Maybe begin to make a table of values if mutiple peaks will be selected.
Take the difference between peak of interest and O1. eg) 4250-2753. This is the value 'spoffs1' which needs to be plugged into
the expt. See below diagram for more illustration..
- edc - now create new expt 2 etc. (can use iexpno as well)
- rpar seltoc.bbo all - read parameters for selective TOCSY
- spoffs1 - enter value of frequency difference determined above (peak1 - o1)
- rga - sets the receiver gain (rg) which depends on the sample concentration (wait)
- zg - zero memory buffer and go
Data Processing, see Chp 11 of Topspin 1.3 manual (page 143)
- tr - trace command allows to store current FID which can then be processed while the data is still acquiring
- efp - exponential line broadening, Fourier transform and phase (with current params in 'edp')
- lb - change the line broadening weight and run efp again if you like
- be sure to manually phase main peak up or down and have the little peaks pointing up..
- The selective 1D TOCSY experiment here uses a tocsy mix time of 80ms
- Note that the selected peak can be inverted in some cases (like in the NOE expt).