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STD NMR
: Q9 U" f# m. B5 C3 G0 V |STD NMR . i; l/ _( D9 s) K
experiments detect magnetization that is transferred from a receptor protein
' T/ X1 r- B3 u1 _, B0 V9 V to a bound ligand. Only bound ligands show STD effects. The experiment may be 3 ~6 u5 N, Y I3 k* V! J
combined with virtually any other NMR experiment, and therefore is well suitable 7 B3 [& [' \- `4 s" E: r# z' h; E
to tackle even very complex problems. In particular, in combination with multidimensional ; E) s0 a) L# \/ S1 V% S
NMR a full characterization of a bound ligand out of a mixture is straightforward.
1 ?! V N: v8 {( G0 x STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
+ M+ t4 r7 k/ v k greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
+ P# p: F* b2 n" {/ ^8 V for screening. With the availability of so called cryo probes it will be possible % b f* M& Y. i# Q2 l
to work with hundred pmol amounts of protein. The dissociation constant should
* G8 N3 K8 E5 K4 i; i( A be in the range between nM and mM. Therefore, STD NMR covers at least two orders 8 n- H \0 A; X( P7 S9 ^, L
of magnitudes more for dissociation constants than trNOE experiments. From competitive
- b$ f4 r9 ]1 s. o STD experiments dissociation constants may be derived. 4 R6 L2 \) ~2 D( ?+ X
6 f( D7 F" k" R7 b
% Q6 A" Q: Q7 k Schematic 4 J4 L% H" ~0 w' C* ^5 _, s' Q
display of the STD NMR effect. Saturation of the protein leads to a direct saturation 4 k3 x; H8 p2 I, \* T
of those parts of ligand(s) in direct contact to the protein. By exchange between + S2 i" I( X! ]6 ^: U) l
bound and free state the saturation is transported to solution and detected
( ]8 X! s; G2 Y+ C by subtracting a spectrum with saturation from a normal spectrum.
1 P, c; X$ }4 W3 H* x
STD NMR gives precise information about the binding epitope of the ligand. This
' D' b* g$ Q; S; _4 m: E; N is very important information for the design of a potent drug. The optimal drug
9 v8 E; ?+ {, t is of optimal size and optimal shape. The size is deduced from STD NMR, and
) d, b$ _0 X9 X! l Y A$ G the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
