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STD NMR
1 n* F+ r8 U* N6 j- mSTD NMR
3 z/ w. {2 t I4 k8 s2 C experiments detect magnetization that is transferred from a receptor protein
' n. c6 t! v7 G* h9 Q$ ?% h5 X1 A% Q to a bound ligand. Only bound ligands show STD effects. The experiment may be
4 k2 b7 r5 i j2 E9 P" B combined with virtually any other NMR experiment, and therefore is well suitable 2 K+ ?. o0 H$ U% f
to tackle even very complex problems. In particular, in combination with multidimensional ) p6 j/ J7 D0 p. B& B) C0 f
NMR a full characterization of a bound ligand out of a mixture is straightforward. 2 t8 E9 p, X6 u! X/ _4 R
STD NMR is extremely robust and gives maximal effects at protein to ligand ratios 6 L- N! F" \& Y- S
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary ( d; A* I$ R" a- L- F2 D
for screening. With the availability of so called cryo probes it will be possible
7 E( P* i) b/ M: B to work with hundred pmol amounts of protein. The dissociation constant should : l0 b2 `$ d3 c, N. b
be in the range between nM and mM. Therefore, STD NMR covers at least two orders ; `4 S/ L6 t) o5 j1 b# }
of magnitudes more for dissociation constants than trNOE experiments. From competitive
# R; |3 o0 `7 j- x- M2 L4 v, ^ STD experiments dissociation constants may be derived. - o, b1 J2 I" ]; t
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Schematic
: V/ {+ O8 T2 ]4 s6 E6 e display of the STD NMR effect. Saturation of the protein leads to a direct saturation
; r" R( Q8 Z4 E7 i$ r7 F, N of those parts of ligand(s) in direct contact to the protein. By exchange between 1 K8 C4 W k+ ~% |
bound and free state the saturation is transported to solution and detected 7 j: H1 W2 E4 b
by subtracting a spectrum with saturation from a normal spectrum.
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STD NMR gives precise information about the binding epitope of the ligand. This 9 @: G' ] e( G$ A v# H' c" u
is very important information for the design of a potent drug. The optimal drug
1 O+ z3 e, Q X; ` W, }" N is of optimal size and optimal shape. The size is deduced from STD NMR, and
- N" J ] n' S' {! x/ B the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
