Responsive luminescent probes emitting in the near-infrared (NIR) are in high demand today for biological applications as they allow for the easy and unambiguous discrimination of autofluorescence. Due to their luminescence properties, lanthanide ions offer an interesting alternative to classical organic fluorescent dyes. This has stimulated the development of lanthanide-based responsive probes. Nevertheless, responsive probes that can operate in water with NIR-emitting lanthanide ions are scarce. In this communication, zinc fingers are shown to be versatile scaffolds to elaborate a variety of Zn -responsive probes based on lanthanide emission and featuring desirable properties for the selective detection of Zn in experimental conditions close to cellular. Of special interest is a NIR-emitting probe relying on Nd emission.

The interest in ratiometric luminescentp robes that detecta nd quantify as pecific analyte is growing. Owing to their special luminescence properties, lanthanide(III) cationso ffer attractive opportunities for the design of dual-color ratiometric probes. Here, the design principle of hetero-bis-lanthanide peptidec onjugates by using native chemical ligation is described for perfect control of the localization of each lanthanide cation within the molecule. Two zinc-responsive probes, r-LZF1 Tb j Cs124 j Eu and r-LZF1 Eu j Cs124 j Tb are described on the basis of az inc finger peptide andt wo DOTA(DOTA = 1,4,7,10-tetraaza-cyclododecane-1,4,7,10-tetra-acetic acid) complexes of terbium and europium.B oth display dual-color ratiometric emission in response to the presence of Zn 2 + .B yu sing as creening approach, anthracene was identified for the sensitization of the luminescence of two near-infrared-emitting lanthanides, Yb 3 + and Nd 3 +. Thus, two novel zinc-responsive hetero-bis-lanthanide probes, r-LZF3 Yb j Anthra j Nd and r-LZF3 Nd j Anthra j Yb were assembled, the former offeringaneat ratiometric response to Zn 2 + with emission in the near-infrared around1 000 nm, which is unprecedented.

Combination of complexes of trivalent lanthanide cations (Ln 3+) for their luminescent properties and peptides for their recognition properties or folding abilities is interesting in view of designing responsive luminescent probes. The octadentate DOTA chelate is the most popular chelate to design luminescent Ln 3+ complex-peptide conjugates. In this article, we describe a novel building block, DO3Apic-tris(allyl)ester, which provides access to peptides with a conjugated nonadentate chelate, namely DO3Apic, featuring a cyclen macrocycle functionalized by three acetate and one picolinamide arms, for improved luminescence properties. This building block, with allyl protecting groups, is readily obtained by solid phase synthesis. We show that it is superior to its analogue with tBu protecting groups for the preparation of peptide conjugates because of the difficult removal of the tBu protecting groups for the latter. Then, two Zn 2+-responsive luminescent probes, which rely on (i) a zinc finger scaffold for selective Zn 2+ binding, (ii) a Eu 3+ complex and (iii) an acridone antenna for long-wavelength sensitization of Eu 3+ luminescence, are compared. One of these probes, LZF3 ACD|Eu , incorporates a DOTA chelate whereas the other, LZF4 ACD|Eu , incorporates a DO3Apic chelate. We show that changing the octadentate DOTA for the nonadentate DO3Apic ligand results in a higher Eu 3+ luminescence lifetime and in a doubling of the quantum yield, confirming the interest of the DO3Apic chelate and the DO3Apic(tris(allyl)ester building block for the preparation of Ln 3+ complex-peptide conjugates. Additionally, the DO3Apic chelate provides self-calibration for LZF4 ACD|Eu luminescence upon excitation of its picolinamide chromophore, making LZF4 ACD|Eu a ratiometric sensor for Zn 2+ detection.

Selective and sensitive detection of Cu(I) is an ongoing challenge due to its important role in biological systems, for example. Herein, we describe a photoluminescent molecular chemosensor integrating two lanthanide ions (Tb 3+ and Eu 3+ ) and respective tryptophan and naphthalene antennas onto a polypeptide backbone. The latter was structurally inspired from copper-regulating biomacromolecules in Gram-negative bacteria and was found to bind Cu + effectively under pseudobiological conditions (log K Cu + = 9.7 ± 0.2). Ion regulated modulation of lanthanide luminescence in terms of intensity and long, millisecond lifetime offers perspectives in terms of ratiometric and timegated detection of Cu + . The role of the bound ion in determining the photophysical properties is discussed with the aid of additional model compounds.

Among non-covalent bonds, the host-guest interaction is an attractive way to attach biomolecules to solid surfaces since the binding strength can be tuned by the nature of host and guest partners or through the valency of the interaction. For that purpose, we synthesized cyclodecapeptide scaffolds exhibiting in a spatially controlled manner two independent domains enabling the multimeric presentation of guest molecules on one face and the other face enabling the potential grafting of a biomolecule of interest. In this work, we were interested in the β-cyclodextrin/ferrocene inclusion complex formed on β-CD monolayers functionalized surfaces. By using surface sensitive techniques such as quartz crystal microbalance and surface plasmon resonance, we quantified the influence of the guest valency on the stability of the inclusion complexes. The results show a drastic enhancement of the affinity with the gradual increase of guest valency. Considering that the sequential binding events are equal and independent, we applied the multivalent model developed by the Huskens group to extract intrinsic binding constants and an effective concentration of host.