Biomedical Engineering Reference
In-Depth Information
eight glucopyranose units (Figure 3.1). CDs form a truncated cone with a hydrophobic
cavity and hydrophilic outer surface. The three native CDs have the same depth but
different widths. The chiral recognition mechanism is based on inclusion of a bulky
hydrophobic moiety of an analyte into the cavity. A further prerequisite for chiral
recognition is the interaction of polar groups of the analyte close to the chiral center
with the hydroxy groups at positions 2 and 3 at the mouth of the CD (Figure 3.2).
A recent study combining capillary electrophoresis (CE) and nuclear magnetic reso-
nance (NMR) investigations gives more insight into the chiral recognition mech-
anisms of CDs [1]. Further articles dealing with theoretical aspects of the chiral
recognition mechanism have been published by Dodziuk et al. [2], Bikadi et al. [3],
and Zhang et al. [4]. Fanali and Bocek [5] developed a procedure for the determina-
tion of association constants of analyte-CD equilibria. The calculation is based on
the measurement of the effective mobility of an analyte at different concentrations of
chiral selector (zero and two different nonzero concentrations):
1
1[ ]
(
)
μ=
′
μ+ μ
KS
[]
′
(3.1)
A
0
AS
+
KS
′
′
′
′
μ
C
(
μ −μ −μ
)
C
(
μ −μ
)
⎡
⎤
⎣
⎦
1
1
0
1
2
2
0
1
μ=
′
(3.2)
AS
′
′
⎡
μ− μ μ
(
CC
)
C
C
⎤
⎣
⎦
01
2
12
21
μ−μ
′
1
μ−μ
′
1
0
1
0
2
K
=
=
(3.3)
μ−μ
′
′
C
μ−μ
′
′
C
1
S
1
2
S
2
μ
0
is the actual mobility of analyte A at zero concentration of CD
μ
AS
is the actual mobility of the complex CD-analyte
[
S
] is the concentration of the chiral selector;
S
= 0 and
C
1
and
C
2
μ′
are the corrected mobilities
Tökes et al. [6] applied computational molecular modeling approaches for the pre-
diction of the suitability of CDs for a certain compound class.
+
A
A
C
C
B
D
B
D
FIGURE 3.2
Inclusion mechanism of an analyte into a CD.
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