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STD NMR
o7 P+ }: \$ H! O& @* lSTD NMR
$ x6 h! T4 I( f. q8 l8 ? experiments detect magnetization that is transferred from a receptor protein
. B% \9 I4 }. y. G5 V* G to a bound ligand. Only bound ligands show STD effects. The experiment may be
+ s6 p a- @: Z+ I combined with virtually any other NMR experiment, and therefore is well suitable
v R4 c# v2 B8 I, B+ f to tackle even very complex problems. In particular, in combination with multidimensional
, I! Q8 g3 o- N- ]8 V8 b3 Z p, M NMR a full characterization of a bound ligand out of a mixture is straightforward.
- X+ n7 A. P1 X' J$ U+ ` STD NMR is extremely robust and gives maximal effects at protein to ligand ratios 1 I/ I; _$ l5 U( V; [: y1 z
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 9 M" t$ Y6 W" ^# r
for screening. With the availability of so called cryo probes it will be possible
# W$ Q* [* u* F to work with hundred pmol amounts of protein. The dissociation constant should % X( Y0 d- Q- B1 A K2 z
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
* h2 M8 ?; b+ s" s8 L of magnitudes more for dissociation constants than trNOE experiments. From competitive 6 y S! H. _ u7 Q8 W: R3 b
STD experiments dissociation constants may be derived.
+ X& N$ W$ }5 I3 R0 ^. H# z
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Schematic
, B; _9 ]& m4 I; S% c Q; s' M5 ^ display of the STD NMR effect. Saturation of the protein leads to a direct saturation
. f, I3 I* x4 Z- r, f of those parts of ligand(s) in direct contact to the protein. By exchange between . C( s+ u* y- b# i0 r* P
bound and free state the saturation is transported to solution and detected " l% Y5 x! X- m( u, k3 Z x
by subtracting a spectrum with saturation from a normal spectrum.
# E1 u+ o2 a! ?: b2 C+ _ STD NMR gives precise information about the binding epitope of the ligand. This 6 z4 {% t' q) z- ^
is very important information for the design of a potent drug. The optimal drug 9 A y9 k Y# T1 W" c+ z& e
is of optimal size and optimal shape. The size is deduced from STD NMR, and
c3 s' l) i. s: M# d the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
