Luminescence molecular probes

We have discussed how to make highly luminescent species, but we have left unaddressed the more difficult question of how to incorporate specific sensitivity into molecular probes. There are two basic problems. First, one must develop a moiety with the desired specific sensitivity. Second, in doing so, one must not violate the basic criteria established earlier and inadvertently turn off the luminescence or introduce unacceptable photochemical sensitivity. 

E Sacksteder, M. Lee, J. N. Demas, and B. A. DeGraff, Long lived, highly luminescent rhenium(I) complexes as molecular probes Intra- and intermolecular excited state interactions, J Am. Chem. Soc. 115, 8230-8238 (1993). 

Baker and coworkers [16] reported on a self-referencing luminescent thermometer designed around the temperature-dependent intramolecular excimer formation/dissociation of the molecular probe l,3-Ws(l-pyrenyl)pro-pane (BPP) dissolved in 1-butyl-l-methylpyrrolidinium bjs(trifluoromethyl-sulfonyl)imide, [C4Cipyr][Tf2N]. Upon an increase in temperature, and hence a decrease in the IL s bulk viscosity, the excimer-to-monomer fluorescence... 

Our motivation for offering a further consideration of excimer fluorescence is that it is a significant feature of the luminescence behavior of virtually all aryl vinyl polymers. Although early research was almost entirely devoted to understanding the intrinsic properties of the excimer complex, more recent efforts have been directed at application of the phenomenon to solution of problems in polymer physics and chemistry. Thus, it seems an appropriate time to evaluate existing information about the photophysical processes and structural considerations which may influence excimer formation and stability. This should help clarify both the power and limitations of the excimer as a molecular probe of polymer structure and dynamics. 

Chiral ruthenium complexes, with luminescence characteristics indicative of binding modes, and stereoselectivities that may be tuned to the helix topology, may be useful molecular probes in solution for nucleic acid secondary structure36). 

Another hydrazine derivative of fluorescein, 5-(((2-(Carbohydrazino)methyl)thio)-acetyl)-aminofluorescein, contains a longer spacer arm off its No. 5 carbon atom of its lower ring than fluorescein-5-thiosemicarbazide, described previously (Molecular Probes). The reagent can be used to react spontaneously with aldehyde- or ketone-containing molecules forming a hydrazone linkage (Fig. 209). It also can be used to label cytosine residues in DNA or RNA by use of the bisulfite activation procedure (Chapter 17, Section 2.1). The resulting fluorescent derivative exhibits a maximal excitation at 490 nm and a maximal luminescence emission peak at 516 nm when dissolved in buffer at pH 8. In the same buffered environment, the compound has an extinction coefficient of approximately 75,000 M-1cm 1 at 490 nm. 

Texas Red hydrazide is a derivative of Texas Red sulfonyl chloride made by reaction with hydrazine (Molecular Probes, Pierce). The result is a sulfonyl hydrazine group on the No. 5 carbon position of the lower ring structure of sulforhodamine 101. The intense Texas Red fluorophore has a quantum yield that is inherently higher than either the tetramethylrhodamine or the Lissamine rhodamine B derivatives of the basic rhodamine molecule. Texas Red s luminescence is shifted maximally into the red region of the spectrum, and its emission peak only minimally overlaps with that of fluorescein. This makes derivatives of this fluorescent probe among the best choices of labels for use in double staining techniques. 

Steve Comby and Jean-Claude G. Biinzli, Lanthanide near-infrared luminescence in molecular probes and devices 217... 

LANTHANIDE NEAR-INFRARED LUMINESCENCE IN MOLECULAR PROBES AND DEVICES... 

---