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STD NMR
% M. w7 U" [' Z/ KSTD NMR - U: |9 A* x6 n, J! X) `, p
experiments detect magnetization that is transferred from a receptor protein
+ N" {6 p w7 p$ W- O to a bound ligand. Only bound ligands show STD effects. The experiment may be
6 ^6 ~) }4 T3 h8 ]" X combined with virtually any other NMR experiment, and therefore is well suitable 7 }* k/ C! U% D+ M2 O7 u
to tackle even very complex problems. In particular, in combination with multidimensional
! D$ B' {5 h+ H- X" h$ M3 } NMR a full characterization of a bound ligand out of a mixture is straightforward. ! [$ I% }- b- s: B7 f% J! k
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios ; W# P, }% G* x* j* X2 h& X
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 8 {: d8 R% T; f5 X$ p0 _: T$ `
for screening. With the availability of so called cryo probes it will be possible & q% ~4 [7 k& l" k- L
to work with hundred pmol amounts of protein. The dissociation constant should / C* `: U& L" H: z* S, G* T3 A
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
! `! H' [( Q: |* m( \ A! P, f of magnitudes more for dissociation constants than trNOE experiments. From competitive
- o+ @- A8 _- _' U) V STD experiments dissociation constants may be derived. ; Y! ] B- f8 t% }! i
2 t+ f1 Y1 b% h
9 O( ?" F- d- G Schematic $ ?& H" }% d7 a
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
1 `" ]' U9 U8 a* k6 W; e$ \ of those parts of ligand(s) in direct contact to the protein. By exchange between ' m4 I/ r3 F3 M0 {& ?# J' G
bound and free state the saturation is transported to solution and detected 5 B ~0 h7 J, H7 c4 ?+ E
by subtracting a spectrum with saturation from a normal spectrum.
$ S. e0 Y, H: i o0 y" l; b: D( O STD NMR gives precise information about the binding epitope of the ligand. This % D9 c/ \; N' O+ ?% s8 I$ h
is very important information for the design of a potent drug. The optimal drug # T; X' t) @/ X( Q# P
is of optimal size and optimal shape. The size is deduced from STD NMR, and 3 t k4 E0 w7 c @+ X
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
