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STD NMR " {/ f6 c- W# R. h m
STD NMR , P. o9 H7 x J: Q: X9 k7 h* I, F
experiments detect magnetization that is transferred from a receptor protein
1 n* |7 o& i N" |. J to a bound ligand. Only bound ligands show STD effects. The experiment may be 1 V1 d3 j- A& B8 l) g
combined with virtually any other NMR experiment, and therefore is well suitable
2 H+ l2 A2 P' L9 e% F8 \0 j to tackle even very complex problems. In particular, in combination with multidimensional
0 m1 B3 ^; C" x0 c NMR a full characterization of a bound ligand out of a mixture is straightforward. ' v- Y1 j/ b# C5 |# Z4 ?
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios 1 t) E8 @% F/ e$ c7 h) [
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
3 s) A& N3 L( K: @, b; Y9 M for screening. With the availability of so called cryo probes it will be possible 4 p2 M# j, d0 w
to work with hundred pmol amounts of protein. The dissociation constant should
6 C" @# W0 i4 t8 U' X/ J be in the range between nM and mM. Therefore, STD NMR covers at least two orders + S; R. O9 W: E- [- c0 Z; J
of magnitudes more for dissociation constants than trNOE experiments. From competitive 0 r; g0 `# |8 }. m' _
STD experiments dissociation constants may be derived. 3 @) C6 I( ~ B6 F
5 E+ c& e' A/ P) V% p' S
$ M$ T* s; i) p8 J Schematic 4 ^0 g. \& Y2 K. d
display of the STD NMR effect. Saturation of the protein leads to a direct saturation 0 a7 Z7 q7 E: \2 H% B
of those parts of ligand(s) in direct contact to the protein. By exchange between
, p1 {; `2 y2 f3 a7 ^ bound and free state the saturation is transported to solution and detected
2 |4 }8 q/ n+ ~8 \1 C4 b$ _+ { by subtracting a spectrum with saturation from a normal spectrum.
+ O! q0 B. M8 `
STD NMR gives precise information about the binding epitope of the ligand. This
$ b& ~2 H/ s& g1 Z# {+ z is very important information for the design of a potent drug. The optimal drug
$ b1 `2 V, \! t% P5 f# }6 P. d# N3 M is of optimal size and optimal shape. The size is deduced from STD NMR, and
4 P% [9 [! e8 J the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
