Lifetime molecular probes

Bloch, S., Lesage, F., McIntosh, L., Gandjbakhche, A., Liang, K. and Achilefu, S. (2005). Whole-body fluorescence lifetime imaging of a tumor-targeted near-infrared molecular probe in mice. J. Biomed. Opt. 10, 054003. 

Figure Bll.1.1 represents a 3T3 cell stained with BODIPY FL C5-ceramide (from Molecular Probes), a specific stain for the Golgi apparatus The color coding for the lifetimes is from 0 to 5 ns. The lifetime is coded in color (right upper) and this color-coded lifetime information is mapped onto the intensity surface (upper left) to give the combined lifetime/intensity plot (lower right). The final combined image shows intensity contours (in white), and a lit intensity surface is employed to accentuate the information in a three-dimensional form.

Calcium Green (2c), Calcium Orange (2d), and Calcium Crimson (2e) have been developed by Molecular Probes, Inc. they are suitable for fluorescence lifetime imaging of calcium.(71)... 

The unimolecular micellar characteristics of this poly(ammonium carboxylate) 156 were demonstrated 179 by UV analysis of guest molecules, such as pinacyanol chloride, phenol blue, and naphthalene combined with fluorescence lifetime decay experiments employing diphenylhexatriene as a molecular probe. The monodispersity, or absence of intermolecular aggregation, and molecular size were determined by electron microscopy. 

The main focus of this study is to utilize excimer formation between pyrene groups attached to PEG chain ends as a molecular probe of intermolecular complex formation. The change upon complexation was monitored by UV-vlsible absorption, excitation, and fluorescence spectroscopies as well as by fluorescence lifetime measurements. 

A wide variety of fluorescent molecular probes have been demonstrated to be suitable for excitation by the He-Cd laser 4-bromomethyl-7-methoxycoumarln has been employed for the detection of carboxylic and phosphoric acids (44,55), 7-chlorocarbonyl-methoxy-4-methylcoumarln for hydroxyl compounds (42), 7-lsothlocya-nato-4-methylcoumarln for amines and amino acids (55), 7-dlazo-4-methyl-coumarln for a variety of aromatic compounds (55), and terbium chelate molecules with long fluorescence lifetimes ( 1 ms) for protein analysis (56). In this study, we examined the utility of l-dlmethylamlnonaphthalene-5-sulfonyl chloride (dansyl chloride) as a sensitive and selective reagent for the determination of biogenic amines and amino acids. 

Many of the fiindamental physical and chemical processes at surfaces and interfaces occur on extremely fast time scales. For example, atomic and molecular motions take place on time scales as short as 100 fs, while surface electronic states may have lifetimes as short as 10 fs. With the dramatic recent advances in laser tecluiology, however, such time scales have become increasingly accessible. Surface nonlinear optics provides an attractive approach to capture such events directly in the time domain. Some examples of application of the method include probing the dynamics of melting on the time scale of phonon vibrations [82], photoisomerization of molecules [88], molecular dynamics of adsorbates [89, 90], interfacial solvent dynamics [91], transient band-flattening in semiconductors [92] and laser-induced desorption [93]. A review article discussing such time-resolved studies in metals can be found in... 

Fig. 3.1.10 Molecular lifetimes xintra and. aii in H-ZSM-5 crystallites obtained using the NMR tracer desorption technique and calculated via Eq. (3.3.15), respectively. Tracing by probe molecules (methane, measurement at 296 K) after an H-ZSM-5 catalyst has been kept for different coking times in a stream of n-hexane (filled symbols) and mesitylene (open symbols) at elevated temperature. The inserts present the evidence provided by a comparison of xintra and r]1,]]], with respect to the distribu-...

In conclusion, we stress that the complementary NLO characterization techniques of pump-probe, Z-scan, and 2PF allow for the unambiguous determination of nonlinear optical processes in organic materials. The important molecular parameters of 2PA cross section, fluorescence efficiency, reorientation lifetimes, excited state cross sections, etc. can be determined. 

The lifetime of the excited state of fluorophores may be altered by physical and biochemical properties of its environment. Fluorescence lifetime imaging microscopy (FLIM) is thus a powerful analytical tool for the quantitative mapping of fluorescent molecules that reports, for instance, on local ion concentration, pH, and viscosity, the fluorescence lifetime of a donor fluorophore, Forster resonance energy transfer can be also imaged by FLIM. This provides a robust method for mapping protein-protein interactions and for probing the complexity of molecular interaction networks. 

---