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STD NMR
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experiments detect magnetization that is transferred from a receptor protein
' i8 A; R% c& w$ ?1 i& l to a bound ligand. Only bound ligands show STD effects. The experiment may be " b* ^6 d, \3 q0 j; \ B; M
combined with virtually any other NMR experiment, and therefore is well suitable
9 S1 ?; _8 j6 f$ B# y6 W, l: ~3 h. } to tackle even very complex problems. In particular, in combination with multidimensional
: X1 F2 e2 P2 P3 H$ I NMR a full characterization of a bound ligand out of a mixture is straightforward.
2 Z9 r/ Y) a, C0 a STD NMR is extremely robust and gives maximal effects at protein to ligand ratios + w9 I+ |5 g1 F: Q/ ]
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary ; t6 {3 a: ~# T& z: q( g
for screening. With the availability of so called cryo probes it will be possible
% B! f& h! i) A$ F- w to work with hundred pmol amounts of protein. The dissociation constant should
. s" o% X" ]" h0 T8 J/ [ be in the range between nM and mM. Therefore, STD NMR covers at least two orders # R/ h% @8 k2 E: ]+ a
of magnitudes more for dissociation constants than trNOE experiments. From competitive 4 ^9 m& A2 o3 ^3 v0 h2 `
STD experiments dissociation constants may be derived.
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display of the STD NMR effect. Saturation of the protein leads to a direct saturation % j- |1 W; M* p" v4 r, G
of those parts of ligand(s) in direct contact to the protein. By exchange between
' z7 ]. E0 m, x: o2 |6 ?/ [$ E bound and free state the saturation is transported to solution and detected
3 A# c: [" G w/ v by subtracting a spectrum with saturation from a normal spectrum.
2 D6 p+ m5 ^( f$ k6 V: s STD NMR gives precise information about the binding epitope of the ligand. This , H, R. u$ Q$ \( P! f" P
is very important information for the design of a potent drug. The optimal drug
# T" {, s. I: b$ D1 \: H' F; b' J is of optimal size and optimal shape. The size is deduced from STD NMR, and 0 [; _/ k6 u4 u& t; q5 M, D
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
