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STD NMR " u" x! n; h4 n C0 f; o
STD NMR
3 G& O2 |& l% _ experiments detect magnetization that is transferred from a receptor protein 8 g9 k7 Z, v8 T
to a bound ligand. Only bound ligands show STD effects. The experiment may be
5 w x$ o9 q1 K/ @3 ?0 x combined with virtually any other NMR experiment, and therefore is well suitable ( D' w h- |6 I: |. U0 [- i
to tackle even very complex problems. In particular, in combination with multidimensional
{: O; d6 o5 Y, w P5 f1 z' }0 ~3 E NMR a full characterization of a bound ligand out of a mixture is straightforward.
* ^ o& @; d, h& g/ g o' g6 }' L STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
* \$ ?; o' k5 ? greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
% e! h# u. ^9 ~9 l: F. o( W3 A- ` for screening. With the availability of so called cryo probes it will be possible % S% K3 ?6 Z) B
to work with hundred pmol amounts of protein. The dissociation constant should
# @2 D" S3 j5 f( e ~ be in the range between nM and mM. Therefore, STD NMR covers at least two orders
8 v2 s; }6 Q0 f3 j6 c+ [% k' E of magnitudes more for dissociation constants than trNOE experiments. From competitive
# y) B% J$ r' r \: ]" F STD experiments dissociation constants may be derived. , U2 k, Q( f" M' {/ P \
2 @! Q @! p3 B" \. h
; X! i, l# x6 V: \3 z Schematic
' p0 U/ g- }0 H3 U* v display of the STD NMR effect. Saturation of the protein leads to a direct saturation * y! w' J. l( p4 h5 n
of those parts of ligand(s) in direct contact to the protein. By exchange between * t/ Q. z7 F" u* o: L
bound and free state the saturation is transported to solution and detected ; `/ i" [& f) Z- z9 q# U
by subtracting a spectrum with saturation from a normal spectrum.
$ Z3 G% s8 f# ? ?7 G+ u# Z
STD NMR gives precise information about the binding epitope of the ligand. This
' Z4 c( ]; f+ a. R- J is very important information for the design of a potent drug. The optimal drug ' d1 p1 p5 `& l. q
is of optimal size and optimal shape. The size is deduced from STD NMR, and ' B* H! l6 M5 i
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
