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STD NMR
$ g/ F; L1 e* f# k1 W0 y) N5 JSTD NMR : Y, |# _7 ?4 ^3 d: X# J6 A
experiments detect magnetization that is transferred from a receptor protein 2 a9 J% W4 f/ P, c+ M" a
to a bound ligand. Only bound ligands show STD effects. The experiment may be - M8 n1 z/ ?- q/ W# A
combined with virtually any other NMR experiment, and therefore is well suitable
# b& m. m. r+ {% Y: ^ to tackle even very complex problems. In particular, in combination with multidimensional - v& y4 L" g3 z" {# D. R# |1 F
NMR a full characterization of a bound ligand out of a mixture is straightforward.
2 ~# j% J4 M0 F ^" H# y1 v( u STD NMR is extremely robust and gives maximal effects at protein to ligand ratios + b. W. r/ G$ P5 T' {+ Q- }
greater than ca. 1:100. It follows that less than 1 nmol of protein is necessary
1 J7 s6 V; \, ~& K9 g0 ~1 L for screening. With the availability of so called cryo probes it will be possible
H: |+ [ P) g! O/ d& D' T1 P to work with hundred pmol amounts of protein. The dissociation constant should
7 v- w4 N5 l. o% l( t, T6 k be in the range between nM and mM. Therefore, STD NMR covers at least two orders 0 c' @3 |* j( h0 N( m
of magnitudes more for dissociation constants than trNOE experiments. From competitive
8 O* F+ _/ O' t. @ STD experiments dissociation constants may be derived.
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5 U% b) m# S" k& G/ @$ k Schematic
- W/ u! E2 E7 G+ z. j3 a# h0 w9 d! d" ^4 z display of the STD NMR effect. Saturation of the protein leads to a direct saturation ( k! O( Y6 U) ~/ ?: p
of those parts of ligand(s) in direct contact to the protein. By exchange between
" I9 y/ f5 ?6 x" G" ]4 I bound and free state the saturation is transported to solution and detected & U3 g" w9 D( Q1 I0 l( B0 O4 y0 U* s- J& J. N
by subtracting a spectrum with saturation from a normal spectrum.
0 W2 H2 N* c$ v STD NMR gives precise information about the binding epitope of the ligand. This 4 O. m5 F: |; U/ c; E( g- ]5 j
is very important information for the design of a potent drug. The optimal drug
, z. J2 _' N7 }0 X4 S( j is of optimal size and optimal shape. The size is deduced from STD NMR, and " L" ]7 h7 Y' ~0 d
the shape is delivered by trNOE experiments.
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发表于 2010-10-18 18:42:26
