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STD NMR
2 h* _/ {$ a& q1 ISTD NMR
0 u) @. F# {6 M1 g. y experiments detect magnetization that is transferred from a receptor protein & v% g" B* S8 k7 D
to a bound ligand. Only bound ligands show STD effects. The experiment may be
; |! @ F3 u& b) n. H combined with virtually any other NMR experiment, and therefore is well suitable 6 m* k' P" D/ K; O
to tackle even very complex problems. In particular, in combination with multidimensional * g+ x4 Y$ n4 N, P+ P6 Y" c
NMR a full characterization of a bound ligand out of a mixture is straightforward.
8 o5 Q8 g- ?/ [0 [' X STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
2 t7 W. s$ B: e8 N greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary & \5 K! b8 {- X/ p e9 u8 n" v' J
for screening. With the availability of so called cryo probes it will be possible
% Y! a# Y3 J4 \% t+ ] to work with hundred pmol amounts of protein. The dissociation constant should % f4 _ \" t1 h. V* k( K
be in the range between nM and mM. Therefore, STD NMR covers at least two orders 5 Y/ E8 y3 ^( S4 g7 w- h
of magnitudes more for dissociation constants than trNOE experiments. From competitive ! Y" B B2 }5 l( X0 x
STD experiments dissociation constants may be derived.
) b% I# L! V3 [* |( k
; l( ~9 a8 y3 P; v% c
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Schematic
! u9 B2 Y3 u! l$ i display of the STD NMR effect. Saturation of the protein leads to a direct saturation
/ _3 D6 K3 n' v3 Z1 G, ^ of those parts of ligand(s) in direct contact to the protein. By exchange between
: d# a# d* v x; Q# c bound and free state the saturation is transported to solution and detected / L+ N+ [- h% u
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
( g* f ^; x6 T2 [3 i& k is very important information for the design of a potent drug. The optimal drug 4 i1 }& O: D7 L+ \+ M* i r' G
is of optimal size and optimal shape. The size is deduced from STD NMR, and
- Q. v" }3 `$ P, S u the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
