Fluorescence spectroscopy theory

The aim of this review was to summarize those aspects of fluorescence spectroscopy that may have value for solving problems in food science and technology. The techniques described, which are mainly based on front-face fluorescence spectroscopy coupled with multidimensional statistical methods, have been illustrated by examples taken from the literature and the work done in our laboratory. Although fluorescence spectroscopy is a technique whose theory and methodology have been extensively exploited for studies of both chemistry and biochemistry, the utility of fluorescence spectroscopy for molecular studies has not yet been fully recognized in food science. Fluorescence spectroscopy has the same potential to address molecular problems in food science as in the biochemical science field, because the scientific questions that need to be answered are closely related. We hope that this coverage will introduce a novel class of techniques in the emulsion and gel fields. 

Lakowicz, J. R. and Balter, A. (1982). Theory of phase-modulation fluorescence spectroscopy for excited-state processes. Biophys. Chem. 16, 99-115. 

Photosensitization of diaryliodonium salts by anthracene occurs by a photoredox reaction in which an electron is transferred from an excited singlet or triplet state of the anthracene to the diaryliodonium initiator.13"15,17 The lifetimes of the anthracene singlet and triplet states are on the order of nanoseconds and microseconds respectively, and the bimolecular electron transfer reactions between the anthracene and the initiator are limited by the rate of diffusion of reactants, which in turn depends upon the system viscosity. In this contribution, we have studied the effects of viscosity on the rate of the photosensitization reaction of diaryliodonium salts by anthracene. Using steady-state fluorescence spectroscopy, we have characterized the photosensitization rate in propanol/glycerol solutions of varying viscosities. The results were analyzed using numerical solutions of the photophysical kinetic equations in conjunction with the mathematical relationships provided by the Smoluchowski16 theory for the rate constants of the diffusion-controlled bimolecular reactions. 

Quenching Theory and Applications, in Lakowicz J. R. (Ed.), Topics in Fluorescence Spectroscopy, Vol. 2, Principles, Plenum Press, New York, pp. 53-126. 

Lipari G. and Szabo A. (1980) Effect of Vibrational Motion on Fluorescence Depolarization and Nuclear Magnetic Resonance Relaxation in Macromolecules and Membranes, Biophys. J. 30, 489—506. Steiner R. F. (1991) Fluorescence Anisotropy Theory and Applications, in Lakowicz J. R. (Ed.), Topics in Fluorescence Spectroscopy, Vol. 2, Principles, Plenum Press, New York, pp. 127-176. 

Thus, at present, fluorescence spectroscopy is capable of providing direct information on molecular dynamics on the nanosecond time scale and can estimate the results of dynamics occurring beyond this range. The present-day multiparametric fluorescence experiment gives new opportunities for interpretation of these data and construction of improved dynamic models. A further development of the theory which would provide an improved description of the dynamics in quantitative terms with allowance for the structural inhomogeneity of protein molecules and the hierarchy of their internal motions is required. 

TCLP TDB TDF THC TBP TEM TLM TM-AFM TOC TRLFS TRU TSP TST TVS Toxicity characteristics leaching procedure Thermodynamic database Tyre-derived fuel Total hydrocarbon Tri-n-butyl phosphate Transmission electron microscopy Triple layer model Tapping mode atomic force microscopy Total organic carbon Time-resolved laser fluorescence spectroscopy Transuranic Total suspended particles Transition state theory Transportable vitrification system... 

Atomic Absorption and Fluorescence Spectroscopy, Kirkbright, G.F. and Sargent, M., Academic Press, London, 1974. Now rather dated but nevertheless an unsurpassed treatment of theory. 

Fluorescence spectroscopy, of proteins basic theory and interpretation, 257-263 determination of fluorescence quenching, 253-255... 

Steady-state fluorescence spectroscopy has also been used to study solvation processes in supercritical fluids. For example, Okada et al. (29) and Kajimoto and co-workers (30) studied intramolecular excited-state complexation (exciplex) and charge-transfer formation, respectively, in supercritical CHF3. In the latter studies, the observed spectral shift was more than expected based on the McRae theory (56,57), this was attributed to cluster formation. In other studies, Brennecke and Eckert (5,31,44,45) examined the fluorescence of pyrene in supercritical CO2, C2HSteady-state emission spectra were used to show density augmentation near the critical point. Additional studies investigated the formation of the pyrene excimer (i.e., the reaction of excited- and ground-state pyrene monomers to form the excited-state dimer). These authors concluded that the observance of the pyrene excimer in the supercritical fluid medium was a consequence of increased solute-solute interactions. 

In fluorescence spectroscopy, however, diffuse reflectance correction of spectral distortions in biological media has been studied extensively. Analytical models based on photon migration theory,44 diffusion theory46,60,61 as well as empirical models,62 have been reported to obtain intrinsic fluorescence. In the following, we will review a particular correction method based on photon migration theory for fluorescence spectroscopy and introduce its Raman counterpart. 

Fluorescence spectroscopy and mass spectrometry have suggested that a ternary complex of iron-cyclodextrin-pollutant exists in solution. Such a complex is believed to play a key role in increasing pollutant degradation rates. Studies using added scavengers also support this theory [38]. A schematic illustration of such a theorized ternary complex is depicted in Figure 5. 

Elson, E.L. and Rigler, R. (2000) Fluorescence correlation spectroscopy. Theory and applications, (eds.), Springer, Heidelberg. 

R. Rigler and E. L. Elson (Eds.). Fluorescence Correlation Spectroscopy Theory and Applications. Springer-Verlag, Berlin, Heidelberg, 2001. 

In order to study interfacial phenomena at a liquid/liquid boundary at a microscopic level, surface-selective or depth-resolved measurements at an interface are absolutely necessary. Among several methods, TIR spectroscopy is a powerful means to obtain an inside look at an interfacial layer in several tens to several hundreds of nanometres. In this study, TIR fluorescence spectroscopy was employed to follow chemical and physical characteristics at liquid/liquid interfaces. Before discussing characteristic features of the structures at liquid/liquid interfaces, the basic theory of TIR of light is reviewed briefly in the following. 

The expression most commonly used in fluorescence spectroscopy is, however, the somewhat simphfied Eq. (6-5b), first developed by Lippert [47, 488] and Mataga [14, 489]. It is based on Onsager s reaction-field theory, which assumes that the fluorophore is a point dipole residing in the center of a spherical cavity with radius a in a homogeneous and isotropic dielectric with relative permittivity e,. The so-called Lippert-Mataga equation is as follows ... 

Widengren J, Schweinberger E, Berger S, Seidel CAM. Two new concepts to measure fluorescence resonance energy transfer via fluorescence correlation spectroscopy theory and experimental realizations. J. Phys. Chem. 2001 105 6851-6866. 106. 

U. Mets, in Fluorescence Correlation spectroscopy. Theory and Application, ed. by R. Rigler, E. Elson (Springer, New York, 2000) pp. 346-359... 

This experiment takes an investigative approach. Students need to become familiar with the theory and technique of fluorescence spectroscopy, solution preparation and experimental design. 

Heiftje GM, Vogelstein EE. A linear response theory approach to time-resolved fluorometry. In Wehry EL, ed. Modern fluorescence spectroscopy. New York Plenum Press, vol 4, 1981 25-50. 

Various other types of spectroscopy, such as acoustic spectroscopy and fluorescence spectroscopy, can also be employed for analysis of a sample. Since the characteristics of different materials vary in different respects and over different frequency ranges, a complete analysis of a sample may require the use of a number of spectroscopic (or other) techniques. Also, because information is available regarding the characteristics of various materials, it is not always necessary to understand the quantum mechanical theory behind spectroscopy in order to effectively use the equipment. To understand the fundamental operation of the equipment, however, a thorough knowledge of quantum theory is necessary. 

Z. Foldes-Papp and M. Kinjo, in Fluorescence Correlation Spectroscopy. Theory and Applications , p. 25, Springer, Berlin etc. (2001). 

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