|
STD NMR 0 `, L7 T8 Z O
STD NMR , V0 V) u. k9 h: ~9 X( a& O$ |" e9 \
experiments detect magnetization that is transferred from a receptor protein 3 s7 e1 \2 ?' c3 w* y4 _! o/ K
to a bound ligand. Only bound ligands show STD effects. The experiment may be - g$ m) I1 q) Z! g$ v! f
combined with virtually any other NMR experiment, and therefore is well suitable
: f7 a( s) {$ Q( p' g& y# _' } to tackle even very complex problems. In particular, in combination with multidimensional
4 t4 c# I2 l2 R3 [1 S NMR a full characterization of a bound ligand out of a mixture is straightforward. & s1 ^% v* ?- x4 z) V) |* j
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
* y: c3 \& `8 R! | greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
5 k6 @. b3 T* d for screening. With the availability of so called cryo probes it will be possible
9 |, b6 g% E! @5 D6 p: n9 { to work with hundred pmol amounts of protein. The dissociation constant should
# j8 s7 J; u& {9 Q+ Q be in the range between nM and mM. Therefore, STD NMR covers at least two orders
) ~/ L+ [* q6 W# \6 C of magnitudes more for dissociation constants than trNOE experiments. From competitive
0 d2 J4 K2 U# Z. L& _; ]3 ] STD experiments dissociation constants may be derived.
& `8 L& w" H( W* U3 K
$ a# s& b6 ~& Q4 F3 @
4 ]* l; T3 e7 X
Schematic 3 E' G0 r. `; D- }2 O
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
l4 Y$ q+ \8 e! P( l# R8 d of those parts of ligand(s) in direct contact to the protein. By exchange between ) x k8 J4 W* {! U& Y
bound and free state the saturation is transported to solution and detected
- f4 f7 R( G( F# `2 g7 f by subtracting a spectrum with saturation from a normal spectrum.
5 V0 M& ^8 x3 P5 l+ ]8 f
STD NMR gives precise information about the binding epitope of the ligand. This
; S: q8 l* O& Z+ s is very important information for the design of a potent drug. The optimal drug % s- F) w ?3 Q5 F
is of optimal size and optimal shape. The size is deduced from STD NMR, and * `2 D4 @7 n8 }6 r. w/ @
the shape is delivered by trNOE experiments.
| 
发表于 2010-10-18 18:42:26
