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STD NMR
8 z2 f" w0 l$ RSTD NMR
7 l8 b2 ]' l8 L: c8 s% a experiments detect magnetization that is transferred from a receptor protein 0 p( t) B# H2 J) i; C _
to a bound ligand. Only bound ligands show STD effects. The experiment may be / M* }& X0 w( s( D" J$ U
combined with virtually any other NMR experiment, and therefore is well suitable / Q+ M( K; I5 t$ C# F M3 H6 {! Z
to tackle even very complex problems. In particular, in combination with multidimensional
8 g% z9 {' U; D% t2 V+ e& N4 w5 h NMR a full characterization of a bound ligand out of a mixture is straightforward.
: Q' J' `' _4 r, ] X+ @ STD NMR is extremely robust and gives maximal effects at protein to ligand ratios : P- Y' P( Q2 @' [. B
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary 4 b2 o" d+ U- Y
for screening. With the availability of so called cryo probes it will be possible
/ A- G& N9 X" V) i: Z to work with hundred pmol amounts of protein. The dissociation constant should + E7 W K$ ^- t8 z$ o; W
be in the range between nM and mM. Therefore, STD NMR covers at least two orders . g; B0 \( \" s3 c
of magnitudes more for dissociation constants than trNOE experiments. From competitive
# b1 V0 c' j. q% S+ P STD experiments dissociation constants may be derived. 8 n- ]9 ?; h3 d
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Schematic
2 Z2 b' b( I5 b6 \( F3 | display of the STD NMR effect. Saturation of the protein leads to a direct saturation / [8 }+ m9 G5 _ O+ H' U( {- z
of those parts of ligand(s) in direct contact to the protein. By exchange between " q2 r! U, O K+ D% h
bound and free state the saturation is transported to solution and detected
' ~! z7 p; O% f7 Y 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
: b$ \7 @6 t. `0 O# J is very important information for the design of a potent drug. The optimal drug
3 B% [# C* m0 F% l5 y4 x4 F, k! F& _0 `2 ? is of optimal size and optimal shape. The size is deduced from STD NMR, and ; Z) a4 c6 a6 R( [; z
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
