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STD NMR
! b) j" m/ x; T/ u4 R4 o; kSTD NMR
0 ^2 ^) P- D1 a. t experiments detect magnetization that is transferred from a receptor protein
5 c7 S2 w) w0 {4 G' n1 `0 ^ to a bound ligand. Only bound ligands show STD effects. The experiment may be . _7 D. C1 s3 }9 u1 g7 s- z+ n, o3 `
combined with virtually any other NMR experiment, and therefore is well suitable
' J% X. ~1 Q, L% d to tackle even very complex problems. In particular, in combination with multidimensional
8 c9 a8 C0 [* H- c4 p- e NMR a full characterization of a bound ligand out of a mixture is straightforward.
8 F* Q/ l5 _3 ]: v& Z. p STD NMR is extremely robust and gives maximal effects at protein to ligand ratios
# u, p" S9 J. j0 g! {: W greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
$ U/ v0 y0 @; Y+ X# i' c5 s+ b for screening. With the availability of so called cryo probes it will be possible
4 m- m, Y: `4 U, K$ Z+ e to work with hundred pmol amounts of protein. The dissociation constant should
- n3 F' r7 D$ b) ^ be in the range between nM and mM. Therefore, STD NMR covers at least two orders + y$ n+ T+ H+ y
of magnitudes more for dissociation constants than trNOE experiments. From competitive ; r9 {) |+ ~% k/ @& [
STD experiments dissociation constants may be derived. 0 C" j Y( c( M% x
) m: d7 |5 \- T7 d
. \9 T- Q& b+ j7 U; M+ r+ U7 X
Schematic
1 L# h3 g$ t S* T/ W1 u display of the STD NMR effect. Saturation of the protein leads to a direct saturation
( }0 n+ k' v7 J9 n1 Y of those parts of ligand(s) in direct contact to the protein. By exchange between
" @1 S$ t0 y* [, w6 o) ?- h bound and free state the saturation is transported to solution and detected ! \9 g- Y" X, s
by subtracting a spectrum with saturation from a normal spectrum.
2 _0 r& \. \- H* Z) n5 I8 T9 F" N STD NMR gives precise information about the binding epitope of the ligand. This : `- W( e* w7 [$ O0 W/ b4 @. f. [
is very important information for the design of a potent drug. The optimal drug
! i5 x7 ^# \6 h" O& ` is of optimal size and optimal shape. The size is deduced from STD NMR, and
' r$ E, w& Z; a the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
