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STD NMR
, E! B& E; n; B6 C0 WSTD NMR - _. M! v) K# X Z4 H3 N
experiments detect magnetization that is transferred from a receptor protein : `; x% M+ Y W$ j) B
to a bound ligand. Only bound ligands show STD effects. The experiment may be
2 Z. D$ p: _* j' I combined with virtually any other NMR experiment, and therefore is well suitable f; A+ A( `/ I* ^# d" F: e% |
to tackle even very complex problems. In particular, in combination with multidimensional
! l8 X" ?" w# ?+ }2 H NMR a full characterization of a bound ligand out of a mixture is straightforward.
: g s1 Z z, q% m& F STD NMR is extremely robust and gives maximal effects at protein to ligand ratios - A, G0 `7 o! U# {
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary % Y8 i7 C! @$ {1 P0 a8 Y
for screening. With the availability of so called cryo probes it will be possible $ L9 m* q& a& v1 x% \
to work with hundred pmol amounts of protein. The dissociation constant should
+ S a# X1 z+ G, i- E be in the range between nM and mM. Therefore, STD NMR covers at least two orders
& X" h' O' t' y& E+ U$ x w of magnitudes more for dissociation constants than trNOE experiments. From competitive
A) B* ]( [0 ?# ` STD experiments dissociation constants may be derived.
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! \! j0 s, K s; f. c7 Q0 R: N Schematic
8 ~. E4 a E' O+ D7 [1 j4 I display of the STD NMR effect. Saturation of the protein leads to a direct saturation * o; I0 v P4 A# q
of those parts of ligand(s) in direct contact to the protein. By exchange between
, a7 c% f, U. h$ x3 b0 `9 }. t$ v bound and free state the saturation is transported to solution and detected
4 j2 {1 p$ u" e9 y0 ~: \1 o% C& r by subtracting a spectrum with saturation from a normal spectrum.
& p- \5 Z7 g5 u. A: p0 Z STD NMR gives precise information about the binding epitope of the ligand. This
. E/ G% u5 E, O1 H9 t/ u# O is very important information for the design of a potent drug. The optimal drug 3 b h o7 X6 ^
is of optimal size and optimal shape. The size is deduced from STD NMR, and 6 k- W3 R; b* C
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
