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STD NMR 0 s! i: E; {: `! `2 ^! T
STD NMR ; i8 T' l7 ?% U" Q( j: d1 `
experiments detect magnetization that is transferred from a receptor protein # G# V6 P5 t; h: o6 [/ k
to a bound ligand. Only bound ligands show STD effects. The experiment may be 5 I! o& }# s: V* A5 p8 I
combined with virtually any other NMR experiment, and therefore is well suitable
" v$ ]4 B) E* k to tackle even very complex problems. In particular, in combination with multidimensional + Q1 k3 V( P- Z
NMR a full characterization of a bound ligand out of a mixture is straightforward.
7 ?- d/ g" ^1 l/ }- y4 w. r. e STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
" Q, b; [$ R4 _2 k! @ greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
6 c4 u2 G& b6 N) \1 I# I3 t2 a for screening. With the availability of so called cryo probes it will be possible
( S9 g4 D7 s5 k to work with hundred pmol amounts of protein. The dissociation constant should
, S: o# e! C" O( I: X" a' X be in the range between nM and mM. Therefore, STD NMR covers at least two orders , W$ y9 t7 K1 I) o" f: @4 V
of magnitudes more for dissociation constants than trNOE experiments. From competitive
# v( G5 I, U- W. P STD experiments dissociation constants may be derived.
: }: H; o5 q1 |4 `2 K- O
5 K, C2 {! u, Z& I
* V s9 ]. h" y Schematic
) R0 G7 Y4 C1 @7 Q- e display of the STD NMR effect. Saturation of the protein leads to a direct saturation # }3 h/ c7 L4 x; k' I1 z/ W# f
of those parts of ligand(s) in direct contact to the protein. By exchange between 0 F$ r# r& s( x! a9 Q
bound and free state the saturation is transported to solution and detected
- W4 Y% ~. q l( C+ i' D 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
' U5 m6 D8 F, n$ i0 ^6 r is very important information for the design of a potent drug. The optimal drug
# s8 m1 k6 P5 u is of optimal size and optimal shape. The size is deduced from STD NMR, and # L3 S. K" K" w5 V
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
