The 3D HMQC-NOESY experiment is specifically designed
to obtain X-edited NOESY spectra of X-labeled biomolecules from which homonuclear
1H-1H NOEs can be clearly assigned even in overcrowded
regions (the mechanism involves an heteronuclear transfer via 1J(XH)
followed by a 1H-1H NOE step). Similar results can
be obtained from an analog 3D HSQC-NOESY experiment.
REQUIREMENTS
Implementation on AVANCE spectrometers is feasible. Improved
versions using pulsed field gradients (PFGs) are also available and, therefore,
gradient technology is required. The 1H-13C HMQC-NOESY
experiment is usually applied on 13C-labeled proteins in D20
and at natural abundance on concentrated samples. On the other hand, the
1H-15N HMQC-NOESY is usually applied on 15N-labeled
molecules in H2O.
VERSIONS
The original 3D HMQC-NOESY pulse sequence
(
88JMR588-78
,
89JMR426-85
, and
90JMR433-90
)
basically consists of a 2D 1H-X HMQC pulse sequence followed
by an homonuclear 2D NOESY pulse sequence.
Related experiments are:
The starting HSQC block could be replaced with other heteronuclear schemes:
decoupled HSQC, CT-HSQC, HSMQC
(
90JMR210-86
,
90JACS5370
, and
94JMRB193-104
),
HSQC ...(see, for instance, the 3D HSQC-NOESY experiment).
The NOESY block can be replaced by a COSY, ROESY or a TOCSY block (see,
for instance, the 3D HMQC-TOCSY experiment).
The two building blocks can be reversed (see 3D
NOESY-HMQC experiment)
A 2D version can be designed by fixing the variable 13C evolution
period in the HMQC block (2D w1-X-filtered NOESY experiment) or
by fixing the variable 1H evolution period (see 2D
HMQC-NOESY experiment). In addition, a 13C-selective 1D
HMQC-NOESY could be obtained by fixing both variable evolution delays.
1H-13C HMQC-NOESY sequence using WATERGATE for 13C,15N-labeled proteins
in water
(
01JB261-19
)
Several improved versions have been proposed incorporating the following
modifications:
Use of PFGs
(
94FEBS87-350
).
Use of a w2-12C-filter prior to acquisition and PFGs
(
94JACS9207
).
In the absence of X-decoupling, the 3D HMQC-NOESY experiment exhibits ECOSY
type cross-peaks, allowing the measurement of direct and long-range heteronuclear
oupling constants
(
94JACS5823
).
EXPERIMENTAL DETAILS
The 3D HMQC-NOESY experiment can be recorded in automation
mode. Both blocks are usually optimized as in their 2D counterparts. The
following pulse programs are available:
More details on practical implementation of the 3D HMQC-NOESY experiment
on AVANCE spectrometers can be found in the corresponding Tutorial 3D
HMQC-NOESY experiment
SPECTRA
The HMQC-NOESY experiment affords a 3D spectrum in which X,
1H and 1H chemical shifts are displayed in three
independent dimensions. Thus, the F2(1H)-F3(1H)
plane of a 1H-15N HMQC-NOESY spectrum will show a
typical 2D F1(NH)-F2(1H) NOESY map. On
the other hand, the F2(1H)-F3(1H)
plane of a 1H-13C HMQC-NOESY spectrum will show a
typical 2D F1(1H aliphatic)-F2(1H)
NOESY map while the F1(13C)-F2(1H)
plane will correspond to a conventional 2D 1H-13C
HMQC spectrum.
