Fluorescence characteristics

Fig. 5.4 Chemical mechanism of light emission in the bio- and chemiluminescence reactions of coelenterazine. The bottom row shows some of the fluorescence emitters of coelenteramide. The fluorescence characteristics of the dianion are unknown.

The purple protein is reddish in solutions and purple in the ammonium sulfate precipitate. The molecular weight is 39,000 by the sedimentation equilibrium method. The purple protein is brightly red-fluorescent, but the fluorescence characteristics cannot be related to the luminescence of Latia (Fig. 6.1.5 Shimomura and Johnson, 1968c). 

Hori, K., and Cormier, M. J. (1965). Studies on the bioluminescence of Renilla reniformis. V. Absorption and fluorescence characteristics of chromatographically pure luciferin. Biochim. Biophys. Acta 102 386-396. 

Inouye, S., and Tsuji, F. I. (1994a). Aequorea green fluorescence protein. Expression of the gene and fluorescence characteristics of the recombinant protein. FEBS Lett. 341 277-280. 

Bjorkman, O. Demmig, B. (1987). Photon yield of oxygen evolution and chlorophyll fluorescence characteristics at 77 K among vascular plants of diverse origins. Planta, 170, 489-504. 

The fluorescence characteristics of dannomycin, doxornbicin, and other anthracy-cline drngs solubilized in the water/AOT/n-heptane system were used to monitor their localization [121],... 

Takadate A, Masuda T, Murata C, Tanaka T, Irikura M, Goya S (1995) Fluorescence characteristics of methoxycoumarins as novel fluorophores. Anal Sci 11 97-101... 

Fabian WMF, Schuppler S, Wolfbeis OS (1996) Effects of annulation on absorption and fluorescence characteristics of fluorescein derivatives a computational study. J Chem Soc Perkin Trans 2(5) 853-856... 

It is necessary to note that fluorescence characteristics demonstrate remarkable sensitivity to variations of physicochemical parameters of the environment. Therefore, such parameters as polarity, viscosity, temperature, electric potential, local electric field, pressure, pH, etc., can be registered successfully using the modem sensitive apparatus for fluorescence detection [1, 4—12]. As a consequence, fluorescent molecules are used successfully as molecular probes to study the local characteristics of physicochemical, biochemical and biological systems. 

In addition to the described above methods, there are computational QM-MM (quantum mechanics-classic mechanics) methods in progress of development. They allow prediction and understanding of solvatochromism and fluorescence characteristics of dyes that are situated in various molecular structures changing electrical properties on nanoscale. Their electronic transitions and according microscopic structures are calculated using QM coupled to the point charges with Coulombic potentials. It is very important that in typical QM-MM simulations, no dielectric constant is involved Orientational dielectric effects come naturally from reorientation and translation of the elements of the system on the pathway of attaining the equilibrium. Dynamics of such complex systems as proteins embedded in natural environment may be revealed with femtosecond time resolution. In more detail, this topic is analyzed in this volume [76]. 

Apparatus to investigate the fluorescence characteristics of microscopic objects. Patent of England 2.039.03 R5R.CHI. 

NHS-rhodamine is an amine-reactive fluorescent probe that contains a carboxy-succinimidyl ester group off the No. 5 or 6 carbons on rhodamine s lower-ring structure (Kellogg et al., 1988). The 5- and 6-isomers are virtually identical in their reactivity and fluorescent characteristics. Similar to TRITC (described previously), NHS-rhodamine can be used to label proteins and other macromolecules that contain primary amine groups. The isomeric forms of the fluorescent probe are available in mixed and purified forms (Invitrogen, Thermo Fisher). The pure forms are... 

Silica particles have been exploited in virtually every assay or detection strategy that polymer particles have been used in for bioapplication purposes. Recently, fluorescent dye-doped silica nanoparticles have been developed by a number of groups that have similar fluorescence characteristics to quantum dot nanocrystals (Chapter 9, Section 10). Fluorescent silica nanoparticles can be synthesized less expensively than quantum dots due to the fact that the silica particles incorporate standard organic dyes (Ow et al., 2005 Wang et al., 2006) and are not dependent on making reproducible populations of semiconductor particles with precise diameters to tune emission wavelengths. 

The effect of substituents on the fluorescence characteristics of aromatic hydrocarbons is quite complex and generalizations should be made with caution. Both the nature and position of a substituent can alter these characteristics. 

The solubility in water of many fluorophores is achieved by grafting sulfonate groups. Fortunately, these groups only slightly affect the fluorescence characteristics of the parent molecule. In general, there is a small red-shift of the fluorescence spectrum, whose vibrational structure is somewhat blurred, and the fluorescence quantum yield is slightly decreased. 

Finally, it should be emphasized that the fluorescence characteristics of aromatic hydrocarbons containing more than one substituent are difficult to predict. These effects cannot be simply extrapolated from those of individual substituents. For instance, in spite of the presence of a nitro group, o- and m-nitroaniline and 3-nitro-N,N-dimethylaniline exhibit fluorescence. 

However, the fluorescence characteristics of these compounds are strongly solvent-dependent. In protic solvents such as alcohols, hydrogen bonds can be formed between the nitrogen atoms and the solvent molecules. This results in an inversion of the lowest-lying rt-n and n-n states. As the lowest-lying transition becomes of n —> n character in these solvents, the fluorescence quantum yield is much higher than in hydrocarbon solvents. 

The second family ofxanthene dyes is fluorescein and its derivatives. Fluorescein itself is only slightly fluorescent in alcohol solution. In contrast, the alkali salt obtained by addition of alkali exhibits the well-known yellow-green fluorescence characteristic of the fluorescein dianion (uranin). Fluorescein and its derivatives, e.g. eosin Yand erythrosin Y, are known to be very sensitive to pH and can thus be used as pH fluorescent probes (see Chapter 10). 

The twisting assumption can be demonstrated by comparing the fluorescence characteristics of the bridged model compounds 2 and 3 with those of DMABN (1) in a polar solvent no twist is possible in compound 2 and LE fluorescence is solely... 

In Section 3.4, structural effects were often discussed in conjunction with the nature of the solvent. As emphasized in the introduction to this book, the fluorescence emitted by most molecules is indeed extremely sensitive to their microenvironment (see Figure 1.3), which explains the extensive use of fluorescent probes. The effects of solvent polarity, viscosity and acidity deserves much attention because these effects are the basis of fluorescence probing of these microenvironmental characteristics and so, later chapters of this book are devoted to these aspects. The effects of polarity and viscosity on fluorescence characteristics in fluid media and the relevant applications are presented in Chapters 7 and 8, respectively. The effect of acidity is discussed in Sections 4.5 and 10.2. This section is thus mainly devoted to rigid matrices or very viscous media, and gases. 

The fluorescence characteristics (decay time and/or fluorescence quantum yield) of M are affected by the presence of Q as a result of competition between the intrinsic de-excitation and these intermolecular processes ... 

This chapter is restricted to intermolecular photophysical processes2). Intramolecular excited-state processes will not be considered here, but it should be noted that they can also affect the fluorescence characteristics intramolecular charge transfer, internal rotation (e.g. formation of twisted charge transfer states), intramolecular proton transfer, etc. 

Case C is illustrated in Scheme 4.2, where Iq is the diffusional second-order rate constant for the formation of the pair (M. .. Q) from separated M and Q, k i is the first-order backward rate constant for this step, kR is the first-order rate constant for the reaction of (M. .. Q) to form products 3, and km (= 1/%) is the rate constant for intrinsic de-excitation of M. If the interaction between M and Q is weak, the fluorescence characteristics of the pair M. .. Q are the same as those of M (Scheme 4.2). 

Tab. 4.5. Effect of energy transfer on the fluorescence characteristics of the donor in the case of a heterotransfer (D + A —> D + A )...

Technique Measured fluorescence characteristics Phenomenon Comments... 

The fluorescent molecular sensors will be presented with a classification according to the nature of the photoinduced process (mainly photoinduced electron or charge transfer, and excimer formation) that is responsible for photophysical changes upon cation binding. Such a classification should help the reader to understand the various effects of cation binding on the fluorescence characteristics reported in many papers. In most of these papers, little attention is often paid to the origin of cation-induced photophysical changes. 

In the passive mode, the optical device measures the variation in fluorescence characteristics (intensity, lifetime, polarization) of an intrinsically fluorescent analyte. The optical device can have different optical configurations involving in most cases an optical fiber (passive optode) (Figure 10.44). 

In the active mode, the optical device uses for optical transduction the changes in the fluorescence characteristics of a fluorescent molecular sensor (as described in the preceding sections) resulting from the interaction with an analyte3. The two main optical configurations are ... 

In the design of a fluoroionophore, much attention is to be paid to the characteristics of the ionophore moiety and to the expected changes in fluorescence characteristics of the fluorophore moiety on binding. The complexing ability of the ionophore will be considered first. 

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