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STD NMR 7 S5 S( v! a0 M- `9 W
STD NMR
- W* f7 w1 i; N experiments detect magnetization that is transferred from a receptor protein
1 i Z& Q1 R+ ]2 n" u3 A! |5 P to a bound ligand. Only bound ligands show STD effects. The experiment may be 4 S+ u, H w* L; r3 K/ y
combined with virtually any other NMR experiment, and therefore is well suitable 0 D8 L) x, s* K" k- v& d
to tackle even very complex problems. In particular, in combination with multidimensional 2 [& X% \6 G* t" \2 l' e2 u
NMR a full characterization of a bound ligand out of a mixture is straightforward. . K4 b' b2 W9 H' u
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
! C, I* H/ c% I. r6 R1 g greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 7 @0 t0 u$ s4 Y+ j1 F. L- K. e
for screening. With the availability of so called cryo probes it will be possible
8 x# O+ G4 Y1 a, H4 ]# M$ g% g to work with hundred pmol amounts of protein. The dissociation constant should % z& U: ]: j: [6 p
be in the range between nM and mM. Therefore, STD NMR covers at least two orders 9 \9 w- b" x, ?) g9 g
of magnitudes more for dissociation constants than trNOE experiments. From competitive . L( \ V, n# F! Q% Q% U) ^& P# ~
STD experiments dissociation constants may be derived.
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) R/ E% D# @5 @3 G* N% z: }, Q. m
3 i V. A1 H* r4 K! f4 [6 O
Schematic 5 r8 I1 O$ m! H; Z$ Z+ t
display of the STD NMR effect. Saturation of the protein leads to a direct saturation * Q2 A8 s+ ?$ A4 I0 K
of those parts of ligand(s) in direct contact to the protein. By exchange between 8 d- a. l5 M+ p, n
bound and free state the saturation is transported to solution and detected
) S8 n( S8 ~3 c4 h% y' h/ m' E by subtracting a spectrum with saturation from a normal spectrum.
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STD NMR gives precise information about the binding epitope of the ligand. This ( `- `4 ?( ?1 U
is very important information for the design of a potent drug. The optimal drug ' b ^* I9 O6 J: u
is of optimal size and optimal shape. The size is deduced from STD NMR, and
, \% f7 o) ~; f" b0 G( T the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
