2D heteronuclear correlation experiments

Transcription

1 2D heteronuclear correlation experiments Assistant Professor Kenneth Kongstad Bioanalytical Chemistry and Metabolomics Research Group Section for Natural Products and Peptides Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences University of Copenhagen Phone: ; Fax: Bioanalytical Chemistry and Metabolomics Research Group

2 Slide 2 Outline Two dimensional correlation experiments Short review of experiments Example of HSQC, HMBC and H2BC Second dimension and how to optimize the results Choosing delays in HMQC/HSQC and HMBC H2BC

3 Slide 3 Two-dimensional correlation experiments Experiment review and type of information COSY H-H couplings NOESY, ROESY Through space HMQC,HSQC One bond HMBC Multiple bonds H2BC (COSY+HSQC) Two bonds

4 Slide 4 Two-dimensional correlation experiments Mark expected correlations (but not all HMBC-correlations) COSY, 3 J H,H NOESY HSQC, 1 J H,C HMBC, 2 J H,C HMBC, 3 J H,C H2BC, 2-bond H-C correlations

5 Slide 5 Two-dimensional correlation experiments Mark expected correlations COSY, 3 J H,H NOESY HSQC, 1 J H,C HMBC, 2 J H,C HMBC, 3 J H,C H2BC, 2-bond H-C correlations

6 Department of Drug Design and Pharmacology The second dimension Homonuclear Heteronuclear F 1 ( 1 H) F 1 ( 13 C) F 2 ( 1 H) F 2 ( 1 H) Through bond coupling Through space coupling Chemical exchange Dias 6

7 Slide 7 The second dimension in homonuclear experiments Prepare evolution mix detect t 1 t 2 Fourier transform Homonuclear F 1 ( 1 H) F 2 ( 1 H)

8 Slide 8 The second dimension in heteronuclear experiments Prepare evolution mix detect t 1 t 2 Fourier transform Heteronuclear F 1 ( 13 C) F 2 ( 1 H)

9 Slide 9 Design of experiments Double resonance experiment (with two different nuclei) Several channels on the spectrometer (at least two) 1 H and 13 C 1 H and 15 N 1 H and 31 P Probe with coils for all nuclei frequencies Single coil, doubly tuned Dual probes dedicated to e.g., 1 H + 13 C Broadband probes, 1 H + ( 109 Ag 31 P) Inverse configuration (inner coil 1 H) Normal configuration (inner coil X-nuclei)

10 Slide 10

11 Slide 11 Design of experiments The most sensitive experiments start with 1 H and detects the 1 H-signal. Inverse experiments 1 H 13 C: 32 times more sensitive 1 H 15 N: 300 times more sensitive

12 Slide 12 Resolution and time of 1 H-detected experiments Direct dimension, 1 H (= High resolution) Double number of scans => Double time Indirect dimension, 13 C (= Low resolution) Number of increments in second dimension Double resolution => Double time Heteronuclear F 2 ( 1 H) F 1 ( 13 C) 512 rows 240 ppm ( MHz) 70 Hz/row High dispersion, singlets, minimal overlap 1024 points (4 scans) 8 ppm ( MHz) ~5 Hz/point

13 Slide 13 Optimal use of experiment time Sample preparation High concentration (but not too high...) Particle free, easy to shim Optimize spectrometer Tune/match/pulse calibration Shimming Minimize spectral width in indirect dimension Favor high S/N instead of high resolution Post processing Window function (QSINE, ssb 2) Linear prediction (better version of zero filling)

14 Slide 14 Post processing of HMBC QSINE ssb 2 in both directions Linear prediction (128 -> 1024) XFB (pk in f1) + XF2m

15 Slide 15 Post processing of HMBC QSINE ssb 2 in both directions No linear prediction (zero filling, 128 -> 1024) XFB (pk in f1) + XF2m

16 Slide 16 Post processing of HMBC QSINE ssb 1 in both directions Zero-filling, No linear prediction XFB (mc in f1)

17 Slide 17 HMQC and HSQC Correlates 1 H to 13 C (or 31 P, 15 N,...) Identifies diasterotopic pairs Dispersion of signals in crowded regions in a second dimension HMQC HSQC Few pulses, robust, broadening in f1 due to passive couplings (H-H couplings) Less robust, need carfuly calibrated pulses, narrow peaks

18 Slide 18 HMQC and HSQC HMQC Optimal delay, Δ = (2 x 145) -1 ~3.3 ms Decoupling during acquistion HSQC

19 Slide 19 Removal of 1 H signals connected to 12 C A major obstacle of 1 H detected heteronuclear experiments is to filter all signals from 1 H bound to 13 C (1%) from 1 H bound to 12 C (99%) Phase cycling Pulsed field gradients (PFG) Coherence selection 13 C-satelites Difference Inverted by phase cycling

20 Slide 20 Choosing delays in HMBC HMBC is similar to HMQC, but with a longer delay in the preparation part to be more sensitive to long-range H-C couplings. Tune delay to expected coupling size [1/(2 x n J C,H )]. But too long delay => less signal due to relaxation ms ~7-8 Hz HMQC HMBC

21 Slide 21 Choosing delays in HMBC Green: 200 ms [2.5 Hz] Red: 65 ms [7.7 Hz]

22 Slide 22 H2BC two bond correlation HMBC H2BC = Heteronuclear Multiple Bond Correlation = Heteronuclear Two Bond Correlation Constant time experiment H,H coupling during T (COSY), H-C transfer during Tau (HMQC)

23 Slide 23 H2BC example Edited version different signals for CH 2 and CH/CH 3 Prednisolon

24 Slide 25 HSQC 1-bond H-C

25 Slide 26 HSQC + H2BC 1-bond H-C 2-bond H-C

26 Slide 27 HSQC + H2BC + HMBC 1-bond H-C 2-bond H-C n-bond H-C

27 Slide 28 HSQC + H2BC + HMBC

28 Slide 29 1 J H,C and n J H,C in HMBC