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STD NMR
) ]' F" u) j; n- ZSTD NMR . |2 @8 u2 A9 \0 \& m8 p7 T
experiments detect magnetization that is transferred from a receptor protein : o! _* g+ l* o1 Z- V1 s, c4 P9 U3 h
to a bound ligand. Only bound ligands show STD effects. The experiment may be 7 _: e+ ~) H: R' v
combined with virtually any other NMR experiment, and therefore is well suitable
" I3 U- W; Z; m$ @ to tackle even very complex problems. In particular, in combination with multidimensional
_, \" Y0 d0 R( P M NMR a full characterization of a bound ligand out of a mixture is straightforward. 2 S3 c( i5 N( w2 S
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
; w$ E: m' W* e- ` greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
4 W. B" Z) R+ B1 I2 c+ h for screening. With the availability of so called cryo probes it will be possible
^; ^* F3 L, Z" |# d# Y to work with hundred pmol amounts of protein. The dissociation constant should
* f1 @1 e7 M7 s4 H be in the range between nM and mM. Therefore, STD NMR covers at least two orders " m# B) `% h4 M6 v: M4 x5 e
of magnitudes more for dissociation constants than trNOE experiments. From competitive 2 Q A* W6 [4 s l
STD experiments dissociation constants may be derived.
m0 }3 t, i& E
; a5 a( X+ [5 Q4 g. U
+ {, I1 T8 K3 z/ a
Schematic
L$ p4 E2 r* A" R$ |# v: w display of the STD NMR effect. Saturation of the protein leads to a direct saturation 9 K, u) u% m6 M/ T C
of those parts of ligand(s) in direct contact to the protein. By exchange between 5 z: E. h" @: ?' i6 {: @
bound and free state the saturation is transported to solution and detected & v6 ?: P- r' B2 e
by subtracting a spectrum with saturation from a normal spectrum.
( p ~; C8 G$ {: r) T% g' G STD NMR gives precise information about the binding epitope of the ligand. This
i5 s. n4 I( u$ m' m. _- D is very important information for the design of a potent drug. The optimal drug
1 a( L9 h. \4 T1 r is of optimal size and optimal shape. The size is deduced from STD NMR, and : H2 M) G& }+ B. j
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
