Chemistry Reference
In-Depth Information
Figure 14.2
(a) Equilibrium between complex
and free forms of lectins and saccharides.
(b) Illustration of static equilibrium in the
equilibrium dialysis analysis. (c) Illustration of
dynamic equilibrium in the FAC analysis.
v
=
k
ass
Lectin free
[
(
)
]
[
Saccharide free
(
)
]
.
(14.5)
ass
[
(
)
]
v
=
k
dis
Lectin Saccharide complex
−
.
(14.6)
dis
Since
v
ass
equals
v
dis
at equilibrium, the following equation applies:
[
(
)
]
[
(
)
]
=
[
(
)
]
k
Lectin free
Saccharide free
k
Lectin Sacchari
−
de complex
.
(14.7)
ass
dis
Hence, affi nity constant (
K
a
) is a simple expression of
k
ass
/
k
dis
:
kk
ass
=
[
Lectin Saccharide complex
−
(
)
]
[
Lectin free
(
)
]
[
Sacch
aride free
(
)
]
=
K
.
(14.8)
dis
a
In SPR analysis, both association and dissociation processes are monitored in
terms of the 'resonance unit', and their rate constants,
k
ass
and
k
dis
, are determined
using various concentrations of analyte molecules (lectins
versus
immobilized sac-
charides or saccharides
versus
immobilized lectins) along with curve-fi t analysis.
