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{{clubb-pulse-sequence
|name=hdqc_Zex.rp
|synopsis=HZQC and HDQC pulse sequence - allows to measure k<sub>on</sub> and k<sub>off</sub> in slow chemial exchange process
|family=[[HZQC/HDQC]]
|authors=rp,rtc,sr,vv,lsb
|dim=2
|nuclei=HCN
|observe=H
}}
==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==
* {{par|ns|number of scans - multiple of 4, because phase cycle has four steps|160}}

==Delays==
* {{par|d1|recycling delay|1s}}
* {{par|d16|gradient recovery delay|200&mu;s|hardware_dependent=True}}
* {{par|d21|{{1H}}-{{15N}} INEPT delay when {{1H}} is transverse|2.25ms}}
* {{par|d22|{{1H}}-{{15N}} INEPT delay when {{1H}} is transverse|2.72ms}}

==Constants==
* {{par|L3|loop counter for mixing time. The length of the Nz period <nowiki>=</nowiki> 10msec*L3 + 3.2msec.|8}}

==RF channels==

* {{par|O1p|offset for {{1H}} transmitter - on water resonance|4.7|calibrate=True}}
* {{par|O2p|offset for {{13C}} transmitter - center of C&alpha; region|50|calibrate=True}}
* {{par|O3p|offset for {{15N}} transmitter - center of amide region|115|calibrate=True}}

==={{1H}} channel===
* {{par|p1|length of hard {{1H}} {{90}} pulse|calibrate=True}}
====sp1====
* {{par|p11|length of sp1 pulse|1.2ms}}
* {{par|sp1|power level for sp1 pulse|calibrate=True}}
* {{par|pl11|120dB}}
* {{par|spnam1|waveforum for sp1 pulse|Sinc1.1000}}
* {{par|phcor1|phase correction for sp1 pulse|0}}

====sp2====
Selective {{90}} {{1H}} pulse for water resonance.

* {{par|p12|length of pulse sp2|1.2ms}}
* {{par|sp2|power level for sp2 pulse|calibrate=True}}
* {{par|pl12|120dB}}
* {{par|spnam2|waveform for sp2|Sinc1.1000}}

====sp4====
Selective {{180}} {{1H}} for amides, that does not perturb {{H2O}}.

* {{par|p14|length of pulse sp4. p14 should invert amide protons, but not excite water|1.5ms}}
* {{par|sp4|power level for sp4 pulse|calibrate=True}}
* {{par|pl14|120dB}}
* {{par|spnam4|waveform for sp4 pulse|Ipurp2.1000|calibrate=True}}
* {{par|spoffs4|offset of pulse sp4 - center of amide region|calibrate=True}}

====sp3====

* {{par|p13|length of pulse sp3|1ms}}
* {{par|sp3|power level of sp3 pulse|calibrate=True}}
* {{par|pl13|120dB}}
* {{par|spnam3|waveform of pulse sp3|gauss}}
* {{par|phcor5|phase correction for pulse sp3|95}}

=={{13C}} channel==

* {{par|p3|hard {{90}} for {{13C}}|calibrate=True}}
* {{par|pl2|power level for {{13C}} {{90}}|calibrate=True}}

=={{15N}} channel==

* {{par|p12|hard {{90}} for {{15N}}|calibrate=True}}
* {{par|pl3|power level for hard {{15N}} {{90}} pulse|calibrate=True}}

==={{15N}} decoupling===

Broadband {{15N}} decoupling is performed during acquisition.

* {{par|pcpd3|length of {{90}} pulse for [[waltz16]]|200|calibrate=True}}
* {{par|pl16|power level for the {{90}} pulse within the [[waltz16]] decoupling|calibrate=True}}
* {{par|cpdprg3|program for composite pulse decoupling|waltz16}}

==Gradients==
All gradients are of sine bell shape, i.e.'''spnamN''' is '''SINE.100''', where N = <nowiki>[1...7]</nowiki>

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===
* {{par|p16|length of gradient gp1|1ms}}
* {{par|gpz1|strength of Z gradient gp1|23}}

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

* {{par|p17|length of gradient gp2|0.5ms}}
* {{par|gpz2|strength of gradient gp2|-35}}

===gp3===
* {{par|p20|length of gradient gp3|2ms}}
* {{par|gpz3|strength of gradient gp3|63}}

===gp4 and gp5===

* {{par|p18|length of gradient gp4|0.5ms}}
* {{par|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====
* {{par|gpz4|strength of gradient gp4|62.9}}
* {{par|gpz5|strength of gradieng gp5|62.9}}

====For HDQC option====
* {{par|gpz4|strength of gradient gp4|77.1}}
* {{par|gpz5|strength of gradieng gp5|77.1}}

[[Category:Chemical exchange]]
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