IMPEACH-MBC ~Improvement of wide nJCH range 1H-detected long-range shift correlation measurements~

  • Summary

NM060013E

In HMBC measurements, signal intensities of long-range correlation peaks depend on magnetization transfer time 1/2 nJCH. A basic HMBC pulse sequence, assuming a fixed value of nJCH, cannot give correlation peaks derived from various nJCH values at once (Fig.3 top). ACCORD-HMBC, incorporating variable delays, acquires a wider range of nJCH orrelations, but its spectrum may distort along the indirect axis (Fig.3 middle). IMPEACH-MBC (IMproved PErformance ACcordion HMBC) solves this problem, by adding cancelling inverse variable delays to ACCORD-HMBC to generate a constant-time sequence. IMPEACH-MBC measurements give spectra where long-range shift correlations can easily be analysed (Fig.3 bottom).

Pulse diagram of IMPEACH-MBC measurements.

Fig.1 Pulse diagram of IMPEACH-MBC measurements.

τ1 = 1/2{1JCHmax + 0.146(1JCHmax1JCHmin)}–1, τ2 = 1/2{1JCHmax – 0.146(1JCHmax1JCHmin)}–1
vd = 1/2(nJCHmin)–1 – y_point[{1/2(nJCHmin)–1 – 1/2(nJCHmax)–1}/(y_points – 1)]
D = initial_delay* + y_point[{1/2(nJCHmin)–1 – 1/2(nJCHmax)–1}/(y_points – 1)]
*initial_delay = 2(PFG + recovery time)

4IMPEACH-MBC spectrum of 4-methyl umbelliferone.

Fig.2 IMPEACH-MBC spectrum of 4-methyl umbelliferone.
nJCHmax = 10 Hz, nJCHmin = 2 Hz, 1JCHmax = 170 Hz, 1JCHmin = 120 Hz, y_points = 512

Spectrometer:JNM-ECX400

HMBC

hmbc_pfg.ex2
long_range_j = 8 Hz
j_constant = 140 Hz

HMBC

↓ cover a wide range of nJCH

ACCORD-HMBC

hmbc_accord_dec_pfg.ex2
y_points = 256
lr_j_min = 1 Hz
lr_j_max = 16 Hz
j_ch_min = 120 Hz
j_ch_max = 160 Hz

ACCORD-HMBC

remove JHH-modulation

IMPEACH-MBC

impeach_mbc_dec_pfg.ex2
y_points = 512
lr_j_min = 2 Hz
lr_j_max = 10 Hz
j_ch_min = 120 Hz
j_ch_max = 170 Hz

IMPEACH-MBC
Spectrometer:JNM-ECX400

Reference

C.E. Hadden, G.E. Martin and V.V. Krishnamurthy, J. Magn. Reson., 140, 274 (1999)

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