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STD NMR
5 F. V- F* D9 ^STD NMR / Z6 X( o( f6 @" x O
experiments detect magnetization that is transferred from a receptor protein 1 i6 @3 x3 f1 q8 R/ I
to a bound ligand. Only bound ligands show STD effects. The experiment may be + I! G+ ]" e2 {1 ?
combined with virtually any other NMR experiment, and therefore is well suitable
% f* F% g2 k: s to tackle even very complex problems. In particular, in combination with multidimensional
- _! y/ T i0 F3 E, i NMR a full characterization of a bound ligand out of a mixture is straightforward. k8 N& N G7 Y, J+ ~2 ]5 X- A
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
3 N! c" r3 }' e4 n/ J0 h greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
; e# w! a+ k: n! n for screening. With the availability of so called cryo probes it will be possible # i) F t; i: N# W8 ~
to work with hundred pmol amounts of protein. The dissociation constant should
' X& q; | X4 E8 h9 }4 Z" W be in the range between nM and mM. Therefore, STD NMR covers at least two orders 7 K5 o. u1 c' |4 `
of magnitudes more for dissociation constants than trNOE experiments. From competitive
O7 ^/ f- B- u% Y STD experiments dissociation constants may be derived. / i% \0 |+ F$ G
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" w& o, r" } Z- C/ w8 N: V* s Schematic
k' ?. A: n* y0 |+ }7 V# O display of the STD NMR effect. Saturation of the protein leads to a direct saturation 6 m% `6 V' V/ l& ]
of those parts of ligand(s) in direct contact to the protein. By exchange between
2 ]$ g. M$ }, j0 g bound and free state the saturation is transported to solution and detected
6 e; |# S1 U9 F% 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 ) C' ?5 H) X3 x* `$ n# l0 \
is very important information for the design of a potent drug. The optimal drug
! Z8 q! o0 _7 `$ J) ?" K is of optimal size and optimal shape. The size is deduced from STD NMR, and
! U4 [9 _6 T5 t$ C( }, @ the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
