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STD NMR
6 r8 `" m1 E3 m3 Q/ cSTD NMR 8 k ~) f0 T+ ], q: l
experiments detect magnetization that is transferred from a receptor protein 5 y" z! H' Q) F% y( I9 r
to a bound ligand. Only bound ligands show STD effects. The experiment may be , C0 U# e9 @* Z. p6 Q
combined with virtually any other NMR experiment, and therefore is well suitable ' `' ]# b! v' e% I! s& T( ?
to tackle even very complex problems. In particular, in combination with multidimensional ' D& c+ P0 v* [( t' C- p: t4 ^
NMR a full characterization of a bound ligand out of a mixture is straightforward. ! m0 e6 [- g0 S
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
: e: z% Y7 ]6 d6 T4 b greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary , g! m6 B7 V( f; W9 q6 X
for screening. With the availability of so called cryo probes it will be possible 9 C W G& z3 `! U. ?2 v `- A
to work with hundred pmol amounts of protein. The dissociation constant should
; w7 T' i8 L9 ]7 h be in the range between nM and mM. Therefore, STD NMR covers at least two orders ( V) v! M, _# {' |4 w1 f
of magnitudes more for dissociation constants than trNOE experiments. From competitive
- A$ p+ U' [# G+ P0 M- d4 }. n STD experiments dissociation constants may be derived. ) ~0 B% ?' U, ?" V
3 o" z4 s c7 j1 R
, l$ a* L0 J: _& @ m2 c. I% l
Schematic
* M& f) r, Q# X0 W display of the STD NMR effect. Saturation of the protein leads to a direct saturation
" K5 r- E$ r0 l! } of those parts of ligand(s) in direct contact to the protein. By exchange between
7 z: H% B5 A* x. R& c3 K bound and free state the saturation is transported to solution and detected 8 t# h& \: O! t, N. f
by subtracting a spectrum with saturation from a normal spectrum.
; ]" G2 d+ S& }& q STD NMR gives precise information about the binding epitope of the ligand. This
, J+ s' Z" M' v. o is very important information for the design of a potent drug. The optimal drug
+ m, \& R4 M7 H' U" K4 Z is of optimal size and optimal shape. The size is deduced from STD NMR, and 5 o4 X; P5 m* c
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
