(EN) Crown ether chelators are provided of the formula
[wherein
P and Q are independently O, S, or NR3 (where Râ is independently H or C1-C6 alkyl);
Y is O, S, or NR4;
L is independently a covalent bond or a link which comprises one or more atoms interconnected by covalent bonds;
RX is independently a reactive functional group;
each SC is independently a conjugated substance;
DYE is a chemical moiety with an absorption maximum beyond 320 nm, eg a chromophoric or fluorescent derivative;
E1, E2, and E3 are independently -(CR52)n-, or -(C(O)CH2)n- (where n = 2-4, and R5 is independently H or CH3, or two R5 moieties on adjacent carbons of one or more of E1, Eé or E3, when taken in combination, form a 5- or 6-membered aliphatic ring);
and wherein the remaining subsituents are as defined in claim 1 and any two adjacent substituents R7-R14, taken in combination with each other, and with the aromatic ring they are bound to, may also form a fused DYE;
provided that said compound is substituted by at least one -L-DYE, -L-RX, or -L-SC at R1, R2, R4 or R7-R14; or at least two of R7-R14, taken in combination, form a fused DYE]. SC may be an amino acid, a peptide, a protein, a polysaccharide, a nucleoside, a nucleotide, an oligonucleotide, a nucleic acid, a hapten, a psoralen, a drug, a hormone, a lipid, a lipid assembly, a synthetic polymer, a polymeric microparticle, a biological cell or a virus, and includes a biotin or a silica. Chelators that are substituted by fluorescent dyes are particularly useful as indicators for metal cations, particularly Na+ and K+ions, and particularly where binding of the target ion results in a change in the fluorescence properties of the indicator that can be correlated with the ion concentration. Methods are provided for utilizing reactive groups on the chelators for conjugation to dyes, lipids and polymers and methods for enhancing entry of the indicators into living cells. The chelators can be used to detect and quantify metal ions. They can also discriminate between metal ions under physiological conditions. This selectivity can be tailored by selection of the crown ether substituents. They can also be useful as ionophores, to transport target ions across cell membranes.