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STD NMR % p3 b9 F( s: Q; o5 O* w1 J
STD NMR
/ N7 R3 l/ J! C( k! h) F3 ^ experiments detect magnetization that is transferred from a receptor protein
) q1 T# J# o$ ^$ y8 W to a bound ligand. Only bound ligands show STD effects. The experiment may be ! N( B' s* h& j4 w
combined with virtually any other NMR experiment, and therefore is well suitable 6 G; C* D7 R5 K
to tackle even very complex problems. In particular, in combination with multidimensional 8 K/ f Y$ S/ x( Y; j( t3 P
NMR a full characterization of a bound ligand out of a mixture is straightforward. $ u$ K; Y9 M: O& Y% ?7 s
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
^2 B i- ]9 L9 S. \) f) l greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 8 q. q8 O; Q6 T9 F- u! H" j- c
for screening. With the availability of so called cryo probes it will be possible " C4 o7 l% i" c
to work with hundred pmol amounts of protein. The dissociation constant should 9 j3 i/ v7 o, O" v; n
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
# H0 i6 m \7 Q3 M& M4 |* h$ a of magnitudes more for dissociation constants than trNOE experiments. From competitive : Q- H* Z J1 w
STD experiments dissociation constants may be derived. , N$ `- G! }0 c% b9 w9 `) g. v
3 w0 [+ }, h6 H- O3 [
6 W0 Y: q J g; P( D Schematic
7 w$ e/ a3 d a5 J display of the STD NMR effect. Saturation of the protein leads to a direct saturation , ?% a& T/ m. v) C' S. D0 u3 |6 E
of those parts of ligand(s) in direct contact to the protein. By exchange between
?& U7 ` k1 }. [ bound and free state the saturation is transported to solution and detected 4 T. t: N. X8 Z" @- l( i2 ~% n
by subtracting a spectrum with saturation from a normal spectrum.
% N- C) h& h, K STD NMR gives precise information about the binding epitope of the ligand. This - l4 _# E& ^" g- S1 W8 W
is very important information for the design of a potent drug. The optimal drug : {8 ~3 W+ h$ w; i& Y; z$ q
is of optimal size and optimal shape. The size is deduced from STD NMR, and
8 j+ K0 Z9 E) O# e* u( V the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
