NMR Constraints
The paramagnetic pseudo-contact shift (PCS) occurs in molecules containing tighly bound rapidly
relaxing paramagnetic metal ions such as lanthanides
(
00JACS4154
and
02EJIC2121
) or certain transition
metals such as iron and cobalt. Usually, two components can contribute to the paramagnetic shift,
a scalar contact shift (through bond), which
propagates about five to six bonds from the paramagnetic center, and a dipolar
pseudocontact shift (through space).
Inclusion of paramagnetic shifts as
constraints in structure determination
(
95PSC296-4
,
97BIO9867
,
97EJB721-244
,
98JB553-12
,
99JACS9276
,
00BIO5355
). Use of the site-directed spin-labeling.
Examples of PCS on paramagnetic proteins:
The use of chemical shift temperatures
(
00JB167
)
Measurement of dipolar couplings in paramagnetic proteins
(
98JACS12903
, 00JPCB2559;
00JB295,
00JB347
and
02JACS5581) to determine the magnetic susceptibility anisotropy.
Use of PCS and RDCs or other NMR restraints after introduction of a paramagnet binding site
(04JB205-28 and 04JACS2963)
A comparative study of the paramagnetism-based constraints vs classical restraints in solution structure determinations of paramagnetic metalloproteins has been described. These constraints are presudocontacts shifts, residual dipolar couplings and nuclear relaxation enhancements.
(
01JB85-21
and
02JB123-22
)
Introduction of a paramagnetic probe to disrupt the symmetry of symmetric protein dimers
(
02JB143-24
).
Relaxation:
Incorporation of NMR restraints in Xplor-NIH
(
04JB249
)