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STD NMR
2 N* U. G4 y5 kSTD NMR $ v# v( v- I7 p% f" l: s
experiments detect magnetization that is transferred from a receptor protein
3 N% T7 {0 `( q) u& v6 w to a bound ligand. Only bound ligands show STD effects. The experiment may be 0 q2 u1 g; b! _+ d5 n
combined with virtually any other NMR experiment, and therefore is well suitable 3 N1 `" s( d2 ^
to tackle even very complex problems. In particular, in combination with multidimensional |, Y: P" T* Y6 b4 u
NMR a full characterization of a bound ligand out of a mixture is straightforward. & ^& j8 @; G7 \% F
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
$ r! K5 V6 e7 \- T# @ greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
# g. f" z+ ?/ w" B3 i: M2 | q! ? for screening. With the availability of so called cryo probes it will be possible B0 _4 v/ J! g) O) h. t. b) {: V
to work with hundred pmol amounts of protein. The dissociation constant should
& n. G, r' o7 F0 }' I be in the range between nM and mM. Therefore, STD NMR covers at least two orders
3 b- `0 F$ p6 P% X5 R of magnitudes more for dissociation constants than trNOE experiments. From competitive ; `! q: _( I7 h; I% P9 F
STD experiments dissociation constants may be derived.
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5 u( @% K, m5 `. {- N$ q. N
1 a6 |( K! T a1 @ Schematic
4 l Z1 N/ Y- _; Y, b display of the STD NMR effect. Saturation of the protein leads to a direct saturation
) u- H* Y4 y: j5 V, e# _1 O' u of those parts of ligand(s) in direct contact to the protein. By exchange between 1 m: e( @3 O: v7 n/ v
bound and free state the saturation is transported to solution and detected
. t6 n: E( `2 \" R- @ 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
# `6 D3 p& G: }' k is very important information for the design of a potent drug. The optimal drug
7 [3 m4 A* F" T/ x- J is of optimal size and optimal shape. The size is deduced from STD NMR, and
: Z1 R$ N4 m/ J7 W( \" O5 }; ~. A the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
