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STD NMR 3 F) M, K1 j9 v0 ^* J" U
STD NMR : T( ?+ {3 A! m! G/ e( A! D
experiments detect magnetization that is transferred from a receptor protein
& H1 v ^) J5 C- r, p, B to a bound ligand. Only bound ligands show STD effects. The experiment may be 1 ]4 M6 I$ i w, _
combined with virtually any other NMR experiment, and therefore is well suitable 9 @7 k6 M2 j+ d, f2 w% K
to tackle even very complex problems. In particular, in combination with multidimensional a: d8 D) s, P" C! w8 D
NMR a full characterization of a bound ligand out of a mixture is straightforward. 5 f* V: D9 k' P. d
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
7 v* q- x( _% I w3 z greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
7 O+ z- h, r X- \ for screening. With the availability of so called cryo probes it will be possible
6 g5 p% n1 s0 Q) K0 _8 Q9 Q to work with hundred pmol amounts of protein. The dissociation constant should 3 O. m6 d- F5 }5 l/ @% v
be in the range between nM and mM. Therefore, STD NMR covers at least two orders ! A1 N+ k$ s J+ u' L
of magnitudes more for dissociation constants than trNOE experiments. From competitive
/ g) L1 w/ s9 N% F STD experiments dissociation constants may be derived.
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Schematic 0 P% H( _- w( V% _ W8 j# u- @
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
+ p7 r7 }6 b5 h+ c of those parts of ligand(s) in direct contact to the protein. By exchange between
: M3 }0 \$ a2 T; M9 W bound and free state the saturation is transported to solution and detected ) V. r, e0 v6 J
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
6 e& J6 n; v5 m is very important information for the design of a potent drug. The optimal drug + V6 ]! d, u! @% G" X" b
is of optimal size and optimal shape. The size is deduced from STD NMR, and 5 ?3 ~, R B8 y( o7 X4 X
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
