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STD NMR
$ y+ @/ K6 J4 O, bSTD NMR ' W6 K9 l3 T, { }+ n8 O% p8 ~
experiments detect magnetization that is transferred from a receptor protein
C9 e: d, i1 E) c( E$ w ]& I to a bound ligand. Only bound ligands show STD effects. The experiment may be
; S0 a$ W9 O- z2 k% C3 k combined with virtually any other NMR experiment, and therefore is well suitable
7 W) O+ A9 b+ T% b Y# `7 [ to tackle even very complex problems. In particular, in combination with multidimensional ) e) Z4 e1 F7 A! W) k. _
NMR a full characterization of a bound ligand out of a mixture is straightforward.
2 j5 i. [' Z" A8 s STD NMR is extremely robust and gives maximal effects at protein to ligand ratios ) d/ F9 u1 H$ c1 \
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary j- _5 n2 O! I' Y; o
for screening. With the availability of so called cryo probes it will be possible ' W" L! e- B. R6 I7 r. D
to work with hundred pmol amounts of protein. The dissociation constant should & N4 ~3 u, Z: F. X" `! M
be in the range between nM and mM. Therefore, STD NMR covers at least two orders 2 y* i7 V- ?2 V7 i9 y- R4 U+ p
of magnitudes more for dissociation constants than trNOE experiments. From competitive 7 l: i" e% U5 u, G5 \6 u
STD experiments dissociation constants may be derived.
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# R* B' L% u2 \4 w% F) B$ F Schematic
% y+ Q+ k4 v p( D0 j display of the STD NMR effect. Saturation of the protein leads to a direct saturation $ q3 c6 x, `- o% a% R. m. C
of those parts of ligand(s) in direct contact to the protein. By exchange between
1 Z! _) B% O6 l bound and free state the saturation is transported to solution and detected + ?& u8 a2 A1 D8 h2 w- K" A, l
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
4 b. S$ G5 _/ O3 s( c r! _" b, v- m is very important information for the design of a potent drug. The optimal drug
' K! [$ c4 ?) i5 }6 C' Q is of optimal size and optimal shape. The size is deduced from STD NMR, and k3 w0 } n2 d% W" _" P# B! T' ^
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
