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Manon Isaac

Synthesis and characterization of peptidic luminescent probes for the biological imaging of copper(I) and zinc(II)

Published on 14 December 2015


Thesis presented 14 December​ 2015

Abstract:
Zinc and copper are essential and toxic for living organisms, so they are tightly regulated. To understand, at cellular level, the role of the kinetically exchangeable pool of these metals and their fluxes, we have designed peptidic luminescent probes based on the binding site of metalloproteins and on a lanthanide complex as time-resolved emitting moiety.
The copperI probe, which is inspired by the chaperone CusF, rely on the formation of a cation-
π interaction between copper and a tryptophan side chain to turn on the luminescence of a terbium ion. Detailed spectroscopic characterizations, including time-resolved spe​ctroscopy, have shown that the cation-π enhances intersystem crossing and thus population of the tryptophan triplet state, which transfers energy to the lanthanide. This probe is selective for Cu+ among physiological cations but is able to detect silverI also. This probe was modified to change its properties (binding constants, selectivity, contrast, emission wavelength). Among derived probes, one of them is able to discriminate between Cu+ and Ag+, a property that has not been reported so far for copper or silver probes.
The zinc probe is based on a zinc finger sequence and rely on the modulation of energy transfer between the lanthanide and its antenna by a distance change. It turns on upon zinc binding and is perfectly selective for zinc. The probe was then modified (i) to incorporate a second lanthanide complex and obtain a ratiometric probe and (ii) to shift the excitation and emission wavelength to the visible and near infrared, respectively. Concerning this last point, a new antenna was discovered for the sensitization of the neodymium ion.

Keywords:
Zinc finger, terbium, model peptide, probe, luminescence, cation-
π, copper

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