|
STD NMR
4 h" t7 V1 R, T8 fSTD NMR 5 ^+ v6 f/ Z) F. J: r. ~. W8 t
experiments detect magnetization that is transferred from a receptor protein
w. R1 l1 L$ |, w' e) ]; i to a bound ligand. Only bound ligands show STD effects. The experiment may be 9 I- P% U9 Y% i3 J& E: f* Y
combined with virtually any other NMR experiment, and therefore is well suitable 7 _2 y+ w! ^) t6 K5 C" s
to tackle even very complex problems. In particular, in combination with multidimensional
2 {, Z- U# U! |+ A NMR a full characterization of a bound ligand out of a mixture is straightforward. " ^; m1 E3 ?) p- r6 s! @
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
: ]( d7 t$ c. q5 j greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary ; [3 [6 U! Y! s( _+ l" l: v
for screening. With the availability of so called cryo probes it will be possible 9 f& z" k( O" S) i
to work with hundred pmol amounts of protein. The dissociation constant should
) ]/ W% K% v/ v _# U9 E0 a be in the range between nM and mM. Therefore, STD NMR covers at least two orders - H' z+ i! p" m, G' `6 f
of magnitudes more for dissociation constants than trNOE experiments. From competitive
% a# C; b. [$ ^+ m9 p: i STD experiments dissociation constants may be derived. ( ?8 T/ {* V* O- _. T" r2 m5 F' U
5 g3 n8 Z3 {) u4 G* j
# W; R2 G7 o9 D% U. j* l Schematic / c8 }; V+ e' C
display of the STD NMR effect. Saturation of the protein leads to a direct saturation
) ^. K+ Y* z2 x. N& f9 v of those parts of ligand(s) in direct contact to the protein. By exchange between , ]1 K8 X8 q" A: O
bound and free state the saturation is transported to solution and detected 5 N& d0 H! \6 U1 \) _* _) A
by subtracting a spectrum with saturation from a normal spectrum.
* a& d8 D$ n1 R" V+ S3 l9 L
STD NMR gives precise information about the binding epitope of the ligand. This ' G1 V0 s. u1 `
is very important information for the design of a potent drug. The optimal drug
4 Y1 X1 p. G( A is of optimal size and optimal shape. The size is deduced from STD NMR, and $ ?$ i& [6 Q+ C" Y. E1 U: U; H, J a
the shape is delivered by trNOE experiments.
| 
发表于 2010-10-18 18:42:26
