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STD NMR 5 ~. E& `2 R$ x; C2 ?) q# N
STD NMR ; s: _) \: _) r, @5 B ~! k. K( H
experiments detect magnetization that is transferred from a receptor protein 8 X" j' F8 o8 }* Z. I; `+ L" E7 p! {
to a bound ligand. Only bound ligands show STD effects. The experiment may be
" g, |; q! S: [: E0 F combined with virtually any other NMR experiment, and therefore is well suitable
8 `& }% p1 J8 a( v; i to tackle even very complex problems. In particular, in combination with multidimensional ( l9 D/ e9 M+ w& ^2 g5 s8 N
NMR a full characterization of a bound ligand out of a mixture is straightforward. 7 L5 v1 Q+ V# W f6 |
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
/ S! @( [/ v# r8 M3 H# r; s greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
# a9 |2 W. q. @# P# F& _9 O% P for screening. With the availability of so called cryo probes it will be possible
. y/ y* t9 ~7 D: G V% ] to work with hundred pmol amounts of protein. The dissociation constant should
9 t# Q. }) H# J, } be in the range between nM and mM. Therefore, STD NMR covers at least two orders
X% W: M; z5 y6 ] of magnitudes more for dissociation constants than trNOE experiments. From competitive * V$ H9 D. V4 f& k+ o
STD experiments dissociation constants may be derived.
: H5 A8 X0 c: @) m0 I
/ X; c! a$ S3 P" Z: d0 B6 }/ g5 f
5 m6 {! |/ X, C5 v Schematic 0 e3 H; g6 i1 }% _* B4 `- ~: [" V
display of the STD NMR effect. Saturation of the protein leads to a direct saturation 8 ~+ ^8 C% W, |! m5 G) Z
of those parts of ligand(s) in direct contact to the protein. By exchange between 8 T* B# |7 E! E( ]: M# @- u
bound and free state the saturation is transported to solution and detected " a; W) S8 I, I8 I
by subtracting a spectrum with saturation from a normal spectrum.
2 ]( i# E+ o- v& n/ R8 ?
STD NMR gives precise information about the binding epitope of the ligand. This
/ h: F3 d( t6 `4 p is very important information for the design of a potent drug. The optimal drug , w, p* q$ A! J( x0 U, e) y) @
is of optimal size and optimal shape. The size is deduced from STD NMR, and
' d5 w% `$ q5 k/ G the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
