HZQC/HDQC for Bruker (hdqc Zex.rp)

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Basic facts about hdqc_Zex.rp

Synopsis: HZQC and HDQC pulse sequence - allows to measure kon and koff in slow chemial exchange process

Family: HZQC/HDQC

Code authors:  Robert Peterson,  Robert Clubb,  Scott Robson,  Valerie Villareal,  Louis-S Bouchard

Copyright: UCLA, Clubb Lab

Introduction

HZQC and HDQC pulse sequences allow to measure rates of association and dissociation in molecular complexes, when chemical exchange is slow.

Please see HZQC/HDQC for more details.

Pulse sequence is switched between HZQC and HDQC by changing strengths of gradients gp4 and gp5 as described below.

General setup

• ns - number of scans - multiple of 4, because phase cycle has four steps - [160]

Delays

• d1 - recycling delay - [1s]
• d16 - gradient recovery delay - [200μs] (hardware dependent)
• d21 - ¹H-¹⁵N INEPT delay when ¹H is transverse - [2.25ms]
• d22 - ¹H-¹⁵N INEPT delay when ¹H is transverse - [2.72ms]

Constants

• L3 - loop counter for mixing time. The length of the Nz period = 10msec*L3 + 3.2msec. - [8]

RF channels

• O1p - offset for ¹H transmitter - on water resonance - [4.7]
• O2p - offset for ¹³C transmitter - center of Cα region - [50]
• O3p - offset for ¹⁵N transmitter - center of amide region - [115]

¹H channel

• p1 - length of hard ¹H 90^o pulse

sp1

• p11 - length of sp1 pulse - [1.2ms]
• sp1 - power level for sp1 pulse
• pl11 - 120dB
• spnam1 - waveforum for sp1 pulse - [Sinc1.1000]
• phcor1 - phase correction for sp1 pulse - [0]

sp2

Selective 90^{o 1}H pulse for water resonance.

• p12 - length of pulse sp2 - [1.2ms]
• sp2 - power level for sp2 pulse
• pl12 - 120dB
• spnam2 - waveform for sp2 - [Sinc1.1000]

sp4

Selective 180^{o 1}H for amides, that does not perturb H₂O.

• p14 - length of pulse sp4. p14 should invert amide protons, but not excite water - [1.5ms]
• sp4 - power level for sp4 pulse
• pl14 - 120dB
• spnam4 - waveform for sp4 pulse - [Ipurp2.1000]
• spoffs4 - offset of pulse sp4 - center of amide region

sp3

• p13 - length of pulse sp3 - [1ms]
• sp3 - power level of sp3 pulse
• pl13 - 120dB
• spnam3 - waveform of pulse sp3 - [gauss]
• phcor5 - phase correction for pulse sp3 - [95]

¹³C channel

• p3 - hard 90^o for ¹³C
• pl2 - power level for ¹³C 90^o

¹⁵N channel

• p12 - hard 90^o for ¹⁵N
• pl3 - power level for hard ¹⁵N 90^o pulse

¹⁵N decoupling

Broadband ¹⁵N decoupling is performed during acquisition.

• pcpd3 - length of 90^o pulse for waltz16 - [200]
• pl16 - power level for the 90^o pulse within the waltz16 decoupling
• cpdprg3 - program for composite pulse decoupling - [waltz16]

Gradients

All gradients are of sine bell shape, i.e.spnamN is SINE.100, where N = [1...7]

In addition all gradients are along z axis, so all gpxN and gpyN should be zero.

Values of gradient strength are give in percent, assuming that 100% corresponds to about 50G/cm.

Related parameter is d16 - gradient recovery delay.

gp1

• p16 - length of gradient gp1 - [1ms]
• gpz1 - strength of Z gradient gp1 - [23]

gp2

Gradient gp2 is used for the echo-antiecho method of quadrature detection.

• p17 - length of gradient gp2 - [0.5ms]
• gpz2 - strength of gradient gp2 - [-35]

gp3

• p20 - length of gradient gp3 - [2ms]
• gpz3 - strength of gradient gp3 - [63]

gp4 and gp5

• p18 - length of gradient gp4 - [0.5ms]
• p19 - length of gradient gp5 - [1ms]

Note: Gradients gp4 and gp5 are used to select type of coherence for the indirect dimension and switch the pulse sequence from HZQC to HDQC as shown below:

For HZQC option

• gpz4 - strength of gradient gp4 - [62.9]
• gpz5 - strength of gradieng gp5 - [62.9]

For HDQC option

• gpz4 - strength of gradient gp4 - [77.1]
• gpz5 - strength of gradieng gp5 - [77.1]