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STD NMR
9 a5 d/ h; H6 S. ^4 s& w" @STD NMR 7 @* Y7 x1 f0 J Z! v
experiments detect magnetization that is transferred from a receptor protein
/ k# {; w2 Q2 ^7 w" s7 P to a bound ligand. Only bound ligands show STD effects. The experiment may be * w; u1 f( M" R/ F; ~9 U
combined with virtually any other NMR experiment, and therefore is well suitable * J( S/ o1 i+ L( Z
to tackle even very complex problems. In particular, in combination with multidimensional
% r% R: W; P' ?' b0 q( g; x NMR a full characterization of a bound ligand out of a mixture is straightforward.
" f$ @: y" d8 _2 s( r& m STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
4 n( O b& W. V% b" h greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 5 ]; z* X7 ~$ V" q, i
for screening. With the availability of so called cryo probes it will be possible
1 x: G/ O6 r. Q' y; V# X to work with hundred pmol amounts of protein. The dissociation constant should + \% N' Z& | n
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
9 o, U' b6 {/ Y9 d% P: h0 T# ~2 g! }# ] of magnitudes more for dissociation constants than trNOE experiments. From competitive + D5 p- s, L: X
STD experiments dissociation constants may be derived.
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& F3 q6 g! F1 D6 e/ u) s5 b Schematic & L3 I o' D; {; x2 [9 n
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
" D( v ^4 C/ P! n# S of those parts of ligand(s) in direct contact to the protein. By exchange between ! x8 j; X6 \0 x% d5 B
bound and free state the saturation is transported to solution and detected
9 \, s% ?5 b5 v' k' ~4 ~/ R9 J by subtracting a spectrum with saturation from a normal spectrum.
2 f$ a" G% z& h; m: v' q STD NMR gives precise information about the binding epitope of the ligand. This
; I& L+ g% K: @, M \ is very important information for the design of a potent drug. The optimal drug ' _4 Z- U: |& C. m: {7 S- z
is of optimal size and optimal shape. The size is deduced from STD NMR, and . R6 G8 D0 \( t: r5 |3 q7 g6 L' E
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
