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STD NMR
" Y) R; R, X# i, L, ISTD NMR 8 z: \ W% c# n r
experiments detect magnetization that is transferred from a receptor protein
# |; k S! ?/ w1 X: F: p2 p1 e2 t to a bound ligand. Only bound ligands show STD effects. The experiment may be 9 q; Z6 Z8 F6 W
combined with virtually any other NMR experiment, and therefore is well suitable
. r" a6 t) Q8 S) _9 l8 d3 R9 O to tackle even very complex problems. In particular, in combination with multidimensional
0 {9 ]4 P7 i5 A, ^ NMR a full characterization of a bound ligand out of a mixture is straightforward.
9 h: g" ]" F; I5 a STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
; |. A$ x% m |8 U greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
5 n$ o+ w, P# w6 \ for screening. With the availability of so called cryo probes it will be possible
" v) f3 O7 L* O" f6 N to work with hundred pmol amounts of protein. The dissociation constant should
) a& c0 E. _/ w+ H& U8 N be in the range between nM and mM. Therefore, STD NMR covers at least two orders
) i0 X5 L2 I: c. T/ \ of magnitudes more for dissociation constants than trNOE experiments. From competitive
# J5 T6 m. l$ q1 k* }3 ?9 o STD experiments dissociation constants may be derived.
1 [4 k& `1 t8 A( |0 x$ ?
3 h, t& y9 K9 A _$ B. M4 H
6 ?% H; i6 i2 G( G Schematic - h+ w. ~) B8 _' B$ \* z4 t) J
display of the STD NMR effect. Saturation of the protein leads to a direct saturation ! B, Q8 w5 R2 K; y3 a, @
of those parts of ligand(s) in direct contact to the protein. By exchange between - `) w. O& w, ?# @3 q- X
bound and free state the saturation is transported to solution and detected
/ |0 ]2 V1 L% A6 h9 A" P2 a by subtracting a spectrum with saturation from a normal spectrum.
) P4 C. o7 U* I) ~6 v& ]
STD NMR gives precise information about the binding epitope of the ligand. This
0 h n- {" f) B* t+ v( d5 N is very important information for the design of a potent drug. The optimal drug
4 j; b5 o8 o8 ^3 F6 G is of optimal size and optimal shape. The size is deduced from STD NMR, and 8 M7 `4 U' C. [, d( u
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
