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STD NMR
* w3 j6 \' L: G7 J" ]- X: J. |& d, YSTD NMR
5 S0 W5 ~3 n5 t, [7 J experiments detect magnetization that is transferred from a receptor protein
: J# p! K2 Y: G/ E# e+ A+ ~6 m6 e/ E to a bound ligand. Only bound ligands show STD effects. The experiment may be
- e e) c8 G0 P6 f+ ^: M combined with virtually any other NMR experiment, and therefore is well suitable
5 K, Q8 i9 f( u+ R2 {# \ to tackle even very complex problems. In particular, in combination with multidimensional 7 B" U9 }+ d* m+ B
NMR a full characterization of a bound ligand out of a mixture is straightforward. 9 p" N8 O) ^- B6 q2 A
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios 7 b6 G/ | d, C% e0 c
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary & S4 p% p: k5 H" ~
for screening. With the availability of so called cryo probes it will be possible
" k- i1 C3 K/ p5 m$ y1 c to work with hundred pmol amounts of protein. The dissociation constant should
0 O1 x9 V: z; i1 ^ be in the range between nM and mM. Therefore, STD NMR covers at least two orders & ^. a" W/ @* U) P7 _2 e
of magnitudes more for dissociation constants than trNOE experiments. From competitive : i h4 E& z2 L# m
STD experiments dissociation constants may be derived. / W4 N) H3 ?5 j! f, X5 F2 q
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4 f$ H5 o% O% ] Schematic
& O5 d! I+ _9 J7 N4 } U1 Z display of the STD NMR effect. Saturation of the protein leads to a direct saturation ( P( {/ p' ^! O, \$ Q+ M- v; f: P
of those parts of ligand(s) in direct contact to the protein. By exchange between
$ p V, q- o- K2 D* X5 f7 R bound and free state the saturation is transported to solution and detected % Z5 X& X4 j% u; k( Q& z/ f
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
9 A& U0 E+ X" T* [' C" s is very important information for the design of a potent drug. The optimal drug ' F6 w! ^1 N, s5 g* f X+ a3 }- P2 Y
is of optimal size and optimal shape. The size is deduced from STD NMR, and ) ~) `5 X6 D4 M
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
