Fluorescent probe, definition

Fig. 1.6. Strategy for the choice of a fluorescent probe. Av, , and t are the Stokes shift, quantum yield and lifetime, respectively (see definitions in Chapter 3).

A Judicious use of CO sensing fluorescent probes (Section 1.4) may provide more sohd clues on the chemical biology of these CORMs. Indeed, a first test with COP-1 proves that CORM-3 delivers CO to cells in vitro [54]. It is plausible to speculate that, in vitro, a complex of the type [Ru(CO)2(CO(Y))L3] (Y = nucleophile), hke those in Ref. [38], enters the cell, reverts to [Ru(CO)3Ls], and releases CO, and that similar alternatives operate in vivo eventually mediated by plasma proteins. The existing ESI-MS and FTIR evidence presented earlier should not be taken as definitive due to the nonbiological conditions in which it was obtained. 

Feng J., Huo Q., Petroff P.M., Stucky G.D. Morphology definition by disclinations and dislocations in a mesostructured silicate crystal. Appl. Phys. Lett. 1997 71 1887-1889 Ferrer M., Lianos P. Study of silica-surfactant composite films with fluorescent probes. Langmuir... 

The fluorescent molecule, CigRBH+, can be used as an alternative probe in the measurement of the interfacial viscosity of microparticles (about 0.5 mm in size) or rotating disks (several, 10 cm in radius) [29,30]. In comparison with the microparticles, the molecular probe has definite advantages. One of those is that the interference of the bulk viscosity is negligibly small and that information about the nano-environment around the probe can be obtained. 

Different biological questions can be addressed using different ON probe structures conveniently labeled with a selected F that exploits the main characteristics of fluorescence, which is the most sensitive spectroscopic technique (10). Their definitions are widely reported in companion articles and will not be discussed here. The applications can be divided into different series. One application concerns synthetic FONs that mimic the different structures found in living systems and aims at structural, dynamics, and interaction studies in vitro. Another... 

Extension of our technique described here is of course limited by various factors. The laser intensity cannot be increased greatly because of the damage of lenses and mirrors of the microscope. Therefore, the concentration of a fluorophore to be bonded as a probe must be rather high, especially when its fluorescence quantum yield is low. Thus, it is difficult to say definitely the smallest size of a particle which is amenable to the decay measurement, but in a fortunate case, a particle as small as 1 um can be examined (8). When a particle is larger than a few tens ym, it is also possible to examine spatially heterogeneous decays within the particle (see Fig.2). 

This definition also clarifies what is not a chemical sensor or biosensor for purposes of market projections and commercialization. Passive assays such as, for example, colorimetric chemical reactions, immunoassays, and nucleic acid probes are not sensors. While such assays do result in a quantifiable entity (such as color production, fluorescence, etc), the assay itself does not provide the means to quantify the response. Rather, a separate quantification system is required. 

The steady-state fluorescence anisotropy/polarization method is also simple and relies on the fact that the probe molecule will tumble rapidly in solution when free, but will have restricted motion upon binding to a macromolecule. Optical excitation of the probe by polarized light will result in preferential absorption by those molecules whose absorption transition dipole is parallel to the electric field vector direction of the light. The subsequent fluorescence will be partially polarized. The definitions of anisotropy (r) and polarization (P) are [188]... 

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