Research
Interests: Elizabeth Karnas
Polypyrrolic
Anion Receptors: Towards Kinetic
Studies of Binding Events
This
research seeks to provide a global
understanding of anion binding as a function of time by utilizing
stopped-flow
analysis in combination with thermodynamic data for a particular
system.
Binding events are frequently characterized solely by thermodynamic
terms or
equilibrium constants (Ka),
but as in work recently published by Sessler et al. on
a prodigiosin alkaloid and several analogues, it was
shown that chloride transport as a function of time was a better
predictor of
biological activity than the corresponding stability constant (Ka).[1]
While the previous studies
were based on the transport of chloride through a lipid membrane, we
sought new
methods such as stopped-flow for a more quantitative
measure of kinetics. The
pursuit of kinetic studies of our anion
binding systems will provide a greater understanding of mechanism as
well as
provide useful data for further applications in anion sensing and
catalysis.
The primary requirement for stopped-flow analysis using standard
equipment is
an optical change such as that in UV-Vis or fluorescence upon binding.
Accordingly, we are to investigating optically active anion receptors
developed
within the Sessler Group including the fluorescence based receptors
dipyrrolyl-functionalized bipyridine (1)
and dipyrrolylquinoxalines (2),
and the colourimetric displacement of p-nitrophenolate from
calix[4]pyrrole by
halides (3).[2],[3],[4]
[1] Sessler,
J.; Eller, L.; Cho, W.S.; Nicolau, S.; Aguilar, A.; Lee, J.T.; Lynch,
V.;
Magda, D. Angew. Chem. Int. Ed. 2005, 44, 5989-5992.
[2] Black, C.; Andrioletti, B.;
Try, A.; Ruiperez, C.; Sessler, J.L., J.
Am. Chem. Soc., 1999, 121,
10438-10439.
[3] Plitt, P; Gross, D.; Lynch,
V.; Sessler, J. Chem. Eur. J.,
2007,
1374-1381.
[4] Gale, P.; Twyman, L.; Handlin, C.; Sessler, J. Chem. Commun., 1999, 1851-1852.