What Mixing Time Should I Use for My 2D-NOESY Measurements?

NOEs are often very small and the appropriate choice of mixing time is a critical factor in achieving good NOESY spectra. There are two opposing factors which must be considered when choosing the most appropriate mixing time. Firstly, you would like the NOE to build up for as long as possible during the mixing time and secondly, you want to loose as little signal as possible to relaxation during the mixing time. The best compromise is to choose a mixing time equal to the average T1 relaxation times for the signals in which you are interested. (See the BLOG entry for October 31, 2007, to learn how to estimate T1's.)

If the standard pulse programs are used, the mixing time is the "d8" parameter on a Bruker spectrometer and the "mix" parameter on a Varian spectrometer.