|
STD NMR 2 `9 u; A' h) s9 x: p
STD NMR
1 R2 P8 L% ^1 I experiments detect magnetization that is transferred from a receptor protein * v7 B2 H7 T, x' Y" Q7 R( `. o
to a bound ligand. Only bound ligands show STD effects. The experiment may be
$ x+ @4 f$ M2 W4 G& d I combined with virtually any other NMR experiment, and therefore is well suitable . S/ Z/ h* p/ t5 N9 M* v
to tackle even very complex problems. In particular, in combination with multidimensional / r; a) [8 |, e: F$ k7 }' ~
NMR a full characterization of a bound ligand out of a mixture is straightforward. " X6 }* J, o7 C: O" K
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
) {9 g' K' h$ M% b4 l$ ?3 r greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
0 A; _. L/ J+ G for screening. With the availability of so called cryo probes it will be possible ! j6 a, H7 @( ^9 b9 C
to work with hundred pmol amounts of protein. The dissociation constant should ; c& W4 |6 `- h: |: t
be in the range between nM and mM. Therefore, STD NMR covers at least two orders $ \+ c' X, h5 t6 @5 [( D% A+ K* ^
of magnitudes more for dissociation constants than trNOE experiments. From competitive " w( y) ?2 v$ z& ?: Q5 d
STD experiments dissociation constants may be derived.
, V8 z) H% \% i( ]$ v0 d
% H9 u8 `- s: U& G1 `
8 L) L* F5 A. e4 L
Schematic , p0 I( Q8 r9 Y* B
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
; M2 ]8 E5 `; b3 t A3 ` of those parts of ligand(s) in direct contact to the protein. By exchange between 5 H0 z# y# f- l/ T
bound and free state the saturation is transported to solution and detected
% K& G* r0 U. Q& q/ s5 v" ? by subtracting a spectrum with saturation from a normal spectrum.
5 d6 c& U* f4 f STD NMR gives precise information about the binding epitope of the ligand. This
; Z1 f7 o5 J) {9 U! l* C! U. E is very important information for the design of a potent drug. The optimal drug 1 j5 J% U: u+ B1 y Y, T
is of optimal size and optimal shape. The size is deduced from STD NMR, and % y* I# ~' X3 T* x- C4 z
the shape is delivered by trNOE experiments.
| 
发表于 2010-10-18 18:42:26
