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STD NMR
" ^8 B5 R3 @. v! g& O7 v: x0 n) SSTD NMR * R+ }& [* ? b+ @* W$ z, q- g, M9 c
experiments detect magnetization that is transferred from a receptor protein m: D9 F8 p3 h, ^7 {
to a bound ligand. Only bound ligands show STD effects. The experiment may be
9 R# J* @9 q$ E& X. Q5 X combined with virtually any other NMR experiment, and therefore is well suitable
- }3 b" R$ S4 O, u+ | m6 |% ^ to tackle even very complex problems. In particular, in combination with multidimensional
# }( h* U# p; e" Q+ O& C3 {$ D6 q NMR a full characterization of a bound ligand out of a mixture is straightforward. ) z: c' t1 ^- C/ R
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios # U4 e1 p' ^' ?, c8 x5 W- Z7 y
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
q: a; f& Q7 P% `+ w) T for screening. With the availability of so called cryo probes it will be possible
8 z6 S+ B- v, N! u; q to work with hundred pmol amounts of protein. The dissociation constant should : n4 b. q* q4 F0 W0 l# Y9 r
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
; L6 V( g/ h) g) {8 X of magnitudes more for dissociation constants than trNOE experiments. From competitive
! F. F' N5 [' [! I' e STD experiments dissociation constants may be derived. " v+ X3 M# o% Y" j
1 d) Y) s" T7 N0 f
' E3 b- r: ^- c( G8 t Schematic # @# E2 U; e. C" M! U# l
display of the STD NMR effect. Saturation of the protein leads to a direct saturation 1 n" P- m" O; M$ t1 p6 l/ H
of those parts of ligand(s) in direct contact to the protein. By exchange between " w# @9 J2 X! x4 \3 O: K; |
bound and free state the saturation is transported to solution and detected 4 F a- A7 ?/ v5 z: r6 L
by subtracting a spectrum with saturation from a normal spectrum.
/ f* K, Z8 r( w5 p5 b STD NMR gives precise information about the binding epitope of the ligand. This ; t! {) r5 ?4 W
is very important information for the design of a potent drug. The optimal drug
# `( M# p7 C9 G4 h0 g8 d2 m is of optimal size and optimal shape. The size is deduced from STD NMR, and
/ {$ ^! ~! J+ ?* D" @, l. x% _ the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
