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STD NMR
) _% E1 y7 x. G1 DSTD NMR 0 |: D7 f/ k/ w: O: [0 s$ c' K6 t
experiments detect magnetization that is transferred from a receptor protein
. [% B# }1 X8 R/ R( c% M) i5 s to a bound ligand. Only bound ligands show STD effects. The experiment may be
: O( P. S! f& i/ }+ s6 h+ Y combined with virtually any other NMR experiment, and therefore is well suitable ) {! ]9 r; V$ r& U! U/ g
to tackle even very complex problems. In particular, in combination with multidimensional & |% |2 z6 u! J
NMR a full characterization of a bound ligand out of a mixture is straightforward. " g( `* o1 {! {
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios 6 r$ m# R' h. _2 V6 [* L6 @
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary E8 g1 |* d+ E( I0 W. o
for screening. With the availability of so called cryo probes it will be possible 4 m/ a3 r, i$ n
to work with hundred pmol amounts of protein. The dissociation constant should 3 R4 R1 ^8 m. m+ l2 {( M
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
. t/ k- `) }* n( t6 x$ y, c( k of magnitudes more for dissociation constants than trNOE experiments. From competitive
4 i6 Q( G0 k* ~- k$ \7 W3 S& ` STD experiments dissociation constants may be derived.
3 Z; W, o8 ]3 x5 t/ [
6 n' [2 \, d$ l/ S; I" ]
. P1 ?$ a: h* X6 G" v
Schematic ' Q9 Z9 E" i) q- o# G, q
display of the STD NMR effect. Saturation of the protein leads to a direct saturation ( x! _7 Q4 }+ g) o
of those parts of ligand(s) in direct contact to the protein. By exchange between 4 r* b/ v7 |) C8 |3 [ {8 B( U
bound and free state the saturation is transported to solution and detected
- F& c: s0 a% w by subtracting a spectrum with saturation from a normal spectrum.
0 U; \3 O" m7 d STD NMR gives precise information about the binding epitope of the ligand. This
, D7 e' h+ P8 E is very important information for the design of a potent drug. The optimal drug 3 P f& q# d8 @& ]8 J2 G; z6 n( T
is of optimal size and optimal shape. The size is deduced from STD NMR, and ! l; }7 s' J: r" n
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
