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STD NMR & E" K$ U2 ~% c1 A$ {1 X
STD NMR # x& @! c! m/ W& M
experiments detect magnetization that is transferred from a receptor protein * }# b' Q R/ t; L" F: R7 P( T, A
to a bound ligand. Only bound ligands show STD effects. The experiment may be
6 v: k4 g* c4 @) y combined with virtually any other NMR experiment, and therefore is well suitable : R7 J/ g' [: h6 O R
to tackle even very complex problems. In particular, in combination with multidimensional 7 u8 D$ t# |* U9 a8 \9 Y
NMR a full characterization of a bound ligand out of a mixture is straightforward.
Y4 w* ~ ?0 @ STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
1 J+ G" a) I5 W; U2 C1 i greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
1 q' H5 f/ W2 S/ d, ?! f; P for screening. With the availability of so called cryo probes it will be possible 3 u9 I. ~$ E( C N
to work with hundred pmol amounts of protein. The dissociation constant should . V5 P( e; G2 G+ q( |
be in the range between nM and mM. Therefore, STD NMR covers at least two orders " b: J; e9 y. F9 w4 ^6 B
of magnitudes more for dissociation constants than trNOE experiments. From competitive 6 j. e# E. q7 D! S: Y# M! i6 n
STD experiments dissociation constants may be derived.
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) J* z9 T! K" @/ R
7 I) b7 ?) N3 a5 U/ g; X Schematic " d( R: ?6 a2 l, e8 e3 [! ]7 Z9 S0 R
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
: {4 A! ?0 i( \$ U" w0 r2 ^ of those parts of ligand(s) in direct contact to the protein. By exchange between
' ?2 u; S1 v$ H- e A2 A1 F/ f bound and free state the saturation is transported to solution and detected x4 R% s7 J# x# W* @" Y7 n& k v
by subtracting a spectrum with saturation from a normal spectrum.
8 Z" j$ A) X" n# x1 F1 R STD NMR gives precise information about the binding epitope of the ligand. This
; V" N9 a+ \2 j: ?! V1 s, e. U6 `* L is very important information for the design of a potent drug. The optimal drug
& S# t8 O" h7 T is of optimal size and optimal shape. The size is deduced from STD NMR, and - ^. i$ U( D& D0 J. [9 }
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
