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STD NMR
# a$ k+ n3 m: }0 V& i$ XSTD NMR 0 u5 Q6 j( }) u% \1 E) J7 t$ D
experiments detect magnetization that is transferred from a receptor protein 9 [: [- N" p! N
to a bound ligand. Only bound ligands show STD effects. The experiment may be J9 v! A1 O- g, q: }
combined with virtually any other NMR experiment, and therefore is well suitable
% z2 _7 D" |* Z; ^! n& G$ j to tackle even very complex problems. In particular, in combination with multidimensional
, ?3 G, A Q0 L/ L; V" w0 D NMR a full characterization of a bound ligand out of a mixture is straightforward.
0 y( C8 f7 E! h9 a" g T1 t STD NMR is extremely robust and gives maximal effects at protein to ligand ratios # B8 l1 N" `1 ^( U
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
- |' _9 z1 O( _ for screening. With the availability of so called cryo probes it will be possible
# ]# w$ R- [; m1 c# D to work with hundred pmol amounts of protein. The dissociation constant should
: {. f, i1 |; A+ A3 w, \0 c be in the range between nM and mM. Therefore, STD NMR covers at least two orders # ?* i% U- [1 L M3 y% I+ ~; J! s
of magnitudes more for dissociation constants than trNOE experiments. From competitive % o7 b: v: Q6 A4 ~& K
STD experiments dissociation constants may be derived.
8 l0 s, n: Z% D- l9 L
- f- c2 d4 g3 U0 ]% q
* y0 |8 n" M Y) J1 ^7 ^! K& j3 O. r9 x
Schematic y6 I5 O- ^6 c; m! x5 T! i5 W
display of the STD NMR effect. Saturation of the protein leads to a direct saturation 1 [" h$ h( J, J K
of those parts of ligand(s) in direct contact to the protein. By exchange between 8 g" F$ N1 g+ M6 L' @
bound and free state the saturation is transported to solution and detected 9 i! z* r' V% d# D7 `! e
by subtracting a spectrum with saturation from a normal spectrum.
3 @9 M. m, Q; I STD NMR gives precise information about the binding epitope of the ligand. This
! A0 d* {0 K; @' \! ^2 l( _ is very important information for the design of a potent drug. The optimal drug
+ \) g; V' b0 x, A is of optimal size and optimal shape. The size is deduced from STD NMR, and ' ?/ W6 y( v* b8 [- ^
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
