Procedure for Acquiring 2D Inverse Detection Spectra HMQC, HMBC and HSQC

Transcription

1 Procedure for Acquiring 2D Inverse Detection Spectra HMQC, HMBC and HSQC This protocol is for qualified users operating Bruker Avance 400 in IBC only. Dr. Jao STOP accepts no responsibility for actions taken as a result of using this protocol. Please see Dr. Chris Jao if you intend to use it. Acquisition: 1. Before you start, it is better to have 1D 1 H and 13 C spectrum available. 2. Eject the standard and insert your sample. 3. On the TOPSPIN command line, type "edc Enter" and choose 2dhcHMQC experiment (gradient enhanced HMQC). Make sure to choose correct solvent and give a title to describe your sample. 4. Type "wobb" to start tuning and matching process make sure that the bottom right corner shows "tune nucleus: 13C". TUNING 4 digits MATCHING 3 digits 5. Push and pull the last digit of the tuning and matching tabs on the probehead (above) until the wobble curve is exactly in the middle and its minimum reaches the zero line (see wobble pictures below) or until the tuning and matching lights on the HPPR preamplifier box all turn green (T~7984, M~895). HPPR 6. After tuning and matching 13 C, click on the top of the wobble window to switch to tuning and matching window of 1 H. The bottom right corner of the /NMR.asp -1-06/16/2005

2 screen shows "tune nucleus: 1H". 7. Tuning and matching 1 H by slowly rotating the tuning and matching rods on the probehead until the wobble curve is exactly in the middle and its minimum reaches the zero line or until the tuning and matching lights on the preamplifier box all turn green. NOTE: Never rotate the rods more than half turn. 8. Click to stop the wobble procedure. 9. Click to close the wobble window. 10. Lock and shim just like you normally will do for a 1 H spectrum (see document "Basic Instructions for Bruker NMR AVANCE 400 Running TOPSPIN") 11. Type "getprosol Enter" to get the standard parameters for your solvent. 12. Adjust "sw" for both F1 and F2 dimensions according to 1D 1 H and 13 C spectrum. You may have acquired the 1D spectrum before or you may acquire them now. Make sure to use different exp no. 13. Adjust "o1p" and "o2p" according to the 1D 1 H and 13 C spectrum. 14. If you have done proton pulse calibration, please adjust the pulse accordingly. Procedure for 1 H pulse calibration is described in the end of this protocol. 15. Type "rga Enter" to get receiver gain. 16. Type "rg Enter" to get the rg value and lower the value by 20%. 17. Set the ns. Please check the default ns value before you make any change. The number of scans should be the multiple of the default ns value. That is, if default ns value is 4, ns should be set to multiple of 4, i.e., 4, 8, 12,. 18. Type "expt Enter" to check the experimental time. 19. Type "zg Enter" to start acquisition. 20. For running HMBC and HSQC, choose "2dhcHMBC" and 2dhcHSQC", respectively. All other settings are the same. 21. When finished, transfer data to other PC for processing. 22. Eject your sample and insert standard (CDCl 3 ). 23. Tuning and matching according to step 3 to Lock on CDCl 3. Read in standard shim file, i.e. "rsh cdcl3.shm Enter". Push STD BY button and close all TOPSPIN related windows. 25. Log out. 26. Turn off the monitor while leaving the computer on /16/2005

3 Processing: 1. Type "xfb Enter" to perform Fourier transform for both dimensions. 2. Phase the spectrum if applicable by clicking to switch to 2D phase correction. 3. Choose two or more peaks in different part of the spectrum. When done, click to display the selected rows. Use and for phase correction like you normally will do for a 1D spectrum. Click to save and return. Finally, click to exit. 4. Type "abs2 Enter" to execute automatic baseline correction in F2. 5. To display projections alone the 2D spectrum, click and move the cursor to the projection area. Rightclick and choose External Projection to assign an existing spectrum as the projection. 6. Use to adjust the intensity scaling (contour levels). 7. Contour levels may also be edited by clicking. After editing, contour levels can be stored by clicking. 8. Click to calibrate (reference)for both dimensions. 9. Type "print Enter" or click the print tag to start XWINPLOT. For 2D inverse detection spectrum, choose Print with layout and use +/2D_inv2.xwp to print /16/2005

4 Proton Pulse Calibration: 1. Phenomenon: The figure below shows the intensity of the excited signals using 1µS increment of pulse width (p1=1, 2, 3, 4, 5 ) at fixed power level (pl =-2). The first, second and third null-points are where the flip angle is 180, 360 and 540, respectively. We usually measure the 360 pulse and divide the value by 4 to get the 90 pulse width (p1). By doing that, we avoid the long waiting time (T 1 ) for magnetization to come back to the Z axis. 360 pulse width 90 pulse width µs 2. Do NOT change the power level (pl) without notifying the manager. Wrong power level can damage the prohead or other hardware components. 3. This is how you may calibrate the pulse: a. Create a new experiment with edc and choose "1hcal". b. Acquire a proton spectrum as usual. c. From the spectrum, select one peak from your sample (not from solvent and better not from aromatic region) and set O1 to that peak. d. Change td to be 2k and si to be 1K by typing "td 2k Enter" and "si 1k Enter". e. Change sw to 2ppm by typing "sw 2 Enter" f. Acquire a spectrum (rga, zg), perform Fourier transform (efp)and phase it (apk). g. Now set p1 to ~ 40 us (p1 40), acquire a spectrum (zg), perform FT and applies phase params(fp). If a negative peak is observed, increase p1 and repeat until the null is found. If a positive peak is observed, decrease p1 instead. f. The p1 value gives the null point is the 360 pulse width. Therefore, dividing /16/2005

5 the value by 4 will give the 90 pulse width (p1). 360 pulse width is about 40μS on this machine. A positive peak shows up decrease p1. Almost there, but P1 is still a little bit too long. P1 has been reduced too much increase P /16/2005