|
STD NMR
$ K. ]+ d: a7 n4 W( ~STD NMR
) w& B% U# P: E8 x, K# z$ { experiments detect magnetization that is transferred from a receptor protein ' M9 Q* b: y8 S: T
to a bound ligand. Only bound ligands show STD effects. The experiment may be + G; D9 ?& o& @% x
combined with virtually any other NMR experiment, and therefore is well suitable 6 R; Y" s! i' x9 O. A0 ?
to tackle even very complex problems. In particular, in combination with multidimensional - x: X% I( D' {& Z
NMR a full characterization of a bound ligand out of a mixture is straightforward. F6 `: _3 `4 N( ?( L" ?# d! ^) G
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
- J: M. o/ ~$ ] greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary ) o% P) N3 j0 i
for screening. With the availability of so called cryo probes it will be possible
! C4 Y0 k8 _4 x3 Y8 E' S5 _, f to work with hundred pmol amounts of protein. The dissociation constant should $ ~. G5 o( j$ P- I/ p* @) S: i- P
be in the range between nM and mM. Therefore, STD NMR covers at least two orders
9 g, c5 ~# x7 A/ O ~ of magnitudes more for dissociation constants than trNOE experiments. From competitive & ~2 X/ p! a$ a9 ` p6 E5 [
STD experiments dissociation constants may be derived. ; s9 c Y4 Y* p: ?! j& e
/ o p+ t5 k% ~1 T- F) N$ J
y% z) l/ b- Y6 @
Schematic
( c2 s- k0 B3 @8 }2 x5 q display of the STD NMR effect. Saturation of the protein leads to a direct saturation
8 M+ l. C% v( Y* E! w( I% ~ of those parts of ligand(s) in direct contact to the protein. By exchange between
" Z9 a8 o4 q* M% ^1 C* n bound and free state the saturation is transported to solution and detected % x# J! ? i6 ` |
by subtracting a spectrum with saturation from a normal spectrum.
7 M+ Y W2 S4 `
STD NMR gives precise information about the binding epitope of the ligand. This
& I# ~$ Q" r" T2 H1 q: T Z is very important information for the design of a potent drug. The optimal drug
! \# u- d- B/ @6 `" ^ is of optimal size and optimal shape. The size is deduced from STD NMR, and
0 Z6 G1 C) V7 x& p4 Z' U2 o, F0 j the shape is delivered by trNOE experiments.
| 
发表于 2010-10-18 18:42:26
