phase,w may be due to slow insertion into the membrane or
dissociation of the complex before membrane insertion.
In summary, we have developed new cholate-based ion
channels that can be gated ‘‘open’’ or ‘‘closed’’ by the addition
or removal of palladium(II). The simple methodology devel-
oped to synthesise these cholate ion channels lends itself to the
creation of multifunctional channels that could be gated by
other ligands, such a biochemical messengers. Work is on-
going to create new ligand-gated channels that will also
mediate targeted vesicle–vesicle and vesicle–cell adhesion.
Notes and references
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Fig. 4 Change in fractional HPTS emission intensity after the addi-
tion of NaOH (base pulse at 180 s) to HPTS vesicles mixed with 1a and
PdCl2
(
,
). 18S6 was added to the samples (indicated by 18S6 at
). To one sample, addition of
240 s) resulting in closed channels (
,
further PdCl2 (at 480 s, indicated by Pd) re-opened the channels ( ).
smooth increase in the Na+ transport rate, giving a sigmoidal
profile to the Na+ transport rate (Fig. 4).
The structure of the active species formed by the combina-
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k = (12 Æ 2) Â 10À4 sÀ1 for Na+ and (6 Æ 2) Â 10À4 sÀ1 for
K+, yet it discharged less of the M+/H+ gradient than in situ
mixing of PdCl2 and 1a.
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21 0.19 mM of an aminocyclodextrin ion channel transported Na+
These observations suggest a membrane-spanning trans
complex is a potential active species. The lower activity of
preformed trans-Pd(1a)2Cl2, which does not exhibit a ‘‘burst’’
with a rate constant of 20 Â 10À4
s
À1. See: N. Madhavan, E. C.
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ꢀc
This journal is The Royal Society of Chemistry 2008
Chem. Commun., 2008, 4007–4009 | 4009