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STD NMR
9 d+ g6 p4 m) Y |5 W4 h$ y$ A: r/ vSTD NMR 1 f+ I0 P U+ a% r- z2 ?& `
experiments detect magnetization that is transferred from a receptor protein
" T' _6 B# W- X4 a! J o: U2 C+ _ to a bound ligand. Only bound ligands show STD effects. The experiment may be 7 t4 |9 i: M8 C5 K! I% |
combined with virtually any other NMR experiment, and therefore is well suitable
) f+ W) v( ~) p4 l2 Y& v to tackle even very complex problems. In particular, in combination with multidimensional
* v5 R, j" r& [! x( P0 M4 S( ]0 f NMR a full characterization of a bound ligand out of a mixture is straightforward.
0 C1 L. u% Q8 @ STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
( J6 p$ X9 o" |9 S3 U greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 9 b* t, ]% [7 w. J3 U4 E' @0 s
for screening. With the availability of so called cryo probes it will be possible
) s3 l" J, d5 W# H+ k% o s to work with hundred pmol amounts of protein. The dissociation constant should / m1 B9 v5 w, v5 ~3 w$ K. E+ R
be in the range between nM and mM. Therefore, STD NMR covers at least two orders / y* U0 M( ]1 {) x4 K
of magnitudes more for dissociation constants than trNOE experiments. From competitive & @6 u, {* _) X; k3 x
STD experiments dissociation constants may be derived.
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6 U3 N8 c1 ]4 j& R( P! B
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Schematic
8 n. x! z5 r' r: L display of the STD NMR effect. Saturation of the protein leads to a direct saturation 4 x* U" } K, S. O5 C4 P& S% i( t% Q0 q
of those parts of ligand(s) in direct contact to the protein. By exchange between
" x* t9 T9 K" R; c" O) s bound and free state the saturation is transported to solution and detected ' R+ M. _) ^) C* ]2 ~ ~( R F2 z
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
0 f0 f9 | M6 Q( |: V is very important information for the design of a potent drug. The optimal drug
- }. f' S" N# v! e is of optimal size and optimal shape. The size is deduced from STD NMR, and " k3 I N9 [# J
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
