Basic 1D carbon with braodband proton decoupling July 29, 2009 NMR facility, School of Pharmacy, Univ. of Maryland, Baltimore Kellie Hom The following is a guideline to set up for a 1D direct-observe carbon experiment with broadband proton decoupling, I assume the user is already proficient in acquiring a 1D proton spectrm. Contact me ahead of your start time to set up the hardware. If you are planning to run C13, whether using the command mode or the push-button mode. let me know ahead of time, preferably, in your weekly request; I will need to tune the probe for optimal proton decoupling. Do not tune the probe on your own without my permission. 1) After probe tuning, you may proceed: find the lock, shim and acquire a proton spectrum. Inspect your the 1D proton to judge the quality of field homogeneity. If satisfied, proceeed. 2) c13_local('solvent') run the macro called c13_local and enter your solvent as an argument; note the use of the single quotes around the solvent name. The above macro sets up the parameters, which are included below as a checklist. You will need to change some of the parameters to suit your needs, but DO NOT change these: tpwr, dpwr, dmf without first talking with me. parameters description Warnings and notes seqfil = 's2pul' Pulse seq is s2pul tn = 'C13' transmitter nucleus is set to C13 dn = 'H1' the nucleus on the second channel (decoupler) is set to proton d1 = 1 Delay between scans; it is set to 1 sec. Change it if needed. solvent = 'xxx' xxx is your solvent name sw=25000 the spectral width is set to 200 ppm, change it if you need to. 25000 Hz/125 MHz = 200 *10 -6 Hz= 200 ppm. See tof below. Change it if needed. tof=0 The offest of middle of the spectral window is set at 0 Hz, about 97 ppm. With a sw of 25000 and a tof of 0, the spectral window is 197 pm at the left edge and -3 ppm at the right edge. See sw above. Change it if needed. tpwr=58 the power is set to 58, DO NOT INCREASE this. DO NOT INCREASE without my permission pw=9 Pulse width; this is about 70 deg, which allows one to pulse faster (with a shorter delay, d1, between scans). nt=64 number of transients is set 64 for initial inspection; you may need to increase this for the final run on your sample. bs=4 block size =4: the fid is available every 4 scans for inspection gain=30 set gain of the receiver alock='n' turn off autolock ashim='n' turn off autoshim dm = 'yyy' proton decoupling is set to be on throughout the pulse sequence. If you want proton decoupling from C13, but not the enhancement from the 'nOe' effects from proton, then set dm to 'nny'. dpwr = 40 the decoupling power is set to 40 (gammaH1 is about 3000 Hz). DO NOT INCREASE this. dmf = 10000 this specifies the 90 deg pulse width for the decoupling sequence. DO NOT CHANGE. dmm='w' assign 'waltz16' as the decoupling pulse sequence lb=5 wft when a multiple of 4 scans have been accumulated, transform, inspect the spectrum, set ppm reference, and optimize parameters, such as nt, d1, sw nt=xxx increase nt to improve signal-to-noise d1=yy d1 can be shortened to get in more scans in the time slot you have sw=zzzzz is the current sw wide enough, too wide? go svf at the end of the experiment, save your data:the program will prompt you for a filename, which should NOT contain a space, nor special characters, such as: #, $, !, *, % , (, ) The advantages of a broadband proton decoupled C13 spectrum, as compared to a C13 spectrum with no proton decoupling, are: -very much simpler to interpret, the carbon signals are not split by C13-1H coupling; -increase in sensitivity by gathering the multiplet intensity into a single line; -introduce a significant nuclear Overhauser enhancement from proton (maximal theoretical enhanement is by a factor of 4).