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STD NMR ; m9 w0 L4 j- s3 s
STD NMR ! L6 u3 q* A G( [) n& T# m( R
experiments detect magnetization that is transferred from a receptor protein 7 }+ e* e/ J' r. h; e
to a bound ligand. Only bound ligands show STD effects. The experiment may be $ X# f9 U7 O! N$ V9 u% {
combined with virtually any other NMR experiment, and therefore is well suitable 4 |( G# B5 ~5 C* |7 ^. Z: M$ P
to tackle even very complex problems. In particular, in combination with multidimensional " ~& q5 ?9 u- r8 o, P1 }' T
NMR a full characterization of a bound ligand out of a mixture is straightforward.
$ l/ u) Y& P5 W2 W/ ` STD NMR is extremely robust and gives maximal effects at protein to ligand ratios + g& l) J: J* I# i6 \
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary p1 N! [/ w! y' D9 C1 w% q
for screening. With the availability of so called cryo probes it will be possible
N1 y' j) A2 C# {# L to work with hundred pmol amounts of protein. The dissociation constant should 3 I- G) O' c" L7 W1 J% j/ P' U
be in the range between nM and mM. Therefore, STD NMR covers at least two orders : Z) Z1 @( Q: f; H2 g* g
of magnitudes more for dissociation constants than trNOE experiments. From competitive
% m1 f' D r- H" e STD experiments dissociation constants may be derived.
: x# j; H1 d% ~3 l
1 R, Z3 \; s E- P0 [/ l, T1 R
) E* U8 g1 V6 w Schematic
) S4 m7 h& }* C) V display of the STD NMR effect. Saturation of the protein leads to a direct saturation 2 D3 C: k. A, w& K& Y, l
of those parts of ligand(s) in direct contact to the protein. By exchange between 6 E$ G0 B3 z }. c6 K, \( F' n% i
bound and free state the saturation is transported to solution and detected
' U7 P* P W6 q: U* Q, U1 v8 u' x by subtracting a spectrum with saturation from a normal spectrum.
% Q9 @7 l! ?( b& E( `! w# ?
STD NMR gives precise information about the binding epitope of the ligand. This 1 D7 j/ V6 I& M L! E
is very important information for the design of a potent drug. The optimal drug
) f! k) n* ~4 I6 {9 k7 W6 s is of optimal size and optimal shape. The size is deduced from STD NMR, and 2 f. [" \2 f; g, g. q
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
