Relationship between fluorescence and

Karabashev [469] devised a method to estimate the influence of dissolved oxygen on remote sensing measurements of chlorophyll a in seawater. The relationship between fluorescence and absorption was studied in this investigation. 

Long-lived luminescence from protein-containing materials was reported many years ago. Debye and Edwards reported that a bluish light was emitted from proteins at cryogenic temperatures after illumination/11 Work in the 1950s established the relationship between fluorescence and the long-lived phosphorescence for the aromatic amino acids in proteins/2-41 Konev in his classic work Fluorescence and Phosphorescence of Proteins and Nucleic Acids summarized this early history.1(5)... 

The relationship between fluorescence and concentration is virtually linear at very low concentrations where the absorbance is less than 0.02 and is approximated by... 

An intramolecular charge transfer excited state may be involved, and the inverse relationship between fluorescence and photoisomerisation suggests a singlet state mechanism. Irradiation of (Z)-urocanic acid, 3-(lH-imidazoI-4-yl)prop-2-enoic acid, in the presence of nitro blue tetrazolium and sodium azide promotes its photoisomerisation in a process which involves reversible addition of the azidyl radical to the double bond. ... 

Describe the processes of UV molecular fluorescence and phosphorescence. What is the relationship between fluorescence and excitation light intensity /q ... 

Stark and Steubing [2] in 1908 were the first to investigate the relationship between fluorescence and the photoelectric eflect (i.e. the external photoeffect), which a few years before had been explained by A. Einstein using the quantum hypothesis of light, i. e. the concept of photons. They carried out their experiments on a large number of different organic solids. This included benzene, naphthalene, and anthracene, but also many other aromatics with N- or OH-substituents. The following quote from one of their publications is still valid today ... 

The excitation light may be absorbed so strongly by the fluorophore that fluorescence is reduced along the excitation path, one aspect of the inner filter effect (1, 2). Such an effect should be suspected if dilution of a sample leads, initially, to a fluorescence increase. This could arise, for example, if the detector observes a part of the sample reached by the excitation beam only in dilute solutions. The expected linear relationship between fluorescence and concentration occurs only with dilute (<10 m) preparations (1). Remember that it is not only the fluorophore that may absorb the excitation and that it is the overall absorbance that must be kept low to avoid any inner filter effects. 

Relationship between fluorescence and concentration. The Beer-Lambert law is valid only in the absence of fluorescence a highly fluorescent compound will give erroneous absorption data when measured in the usual type of photometer. 

Burckhardt, G. Non-linear relationship between fluorescence and membrane potential. Biochim. Biophys. Acta, Biomembr. 1977,468, 227-237. 

Kowalczuk, R, Cooper, W.J., Durako, M J., Kahn, A.E., Gonsior, M., andYoung, H. (2010). Characterization of dissolved organic matter fluorescence in the South Atlantic Bight with use of PARAFAC model Relationships between fluorescence and its components, absorption coefficients and organic carbon concentrations. Mar. Chem., 118,... 

In this chapter, a range of chemometric models for exploring and visualizing CDOM fluorescence data sets and for predicting the relationship between fluorescence and other variables have been introduced. It is apparent that exploratory methods, particularly PARAFAC and PCA, have already been widely implemented. Conversely, calibration models and discriminant analyses have been attempted relatively rarely, yet have considerable potential... 

Fig. 27 Schematic representation of the relationship between absorption and fluorescence emission of the molecules — m and m are the terms involved in the vibrational quantum numbers [4],...

It is often experimentally convenient to use an analytical method that provides an instrumental signal that is proportional to concentration, rather than providing an absolute concentration, and such methods readily yield the ratio clc°. Solution absorbance, fluorescence intensity, and conductance are examples of this type of instrument response. The requirements are that the reactants and products both give a signal that is directly proportional to their concentrations and that there be an experimentally usable change in the observed property as the reactants are transformed into the products. We take absorption spectroscopy as an example, so that Beer s law is the functional relationship between absorbance and concentration. Let A be the reactant and Z the product. We then require that Ea ez, where e signifies a molar absorptivity. As initial conditions (t = 0) we set Ca = ca and cz = 0. The mass balance relationship Eq. (2-47) relates Ca and cz, where c is the product concentration at infinity time, that is, when the reaction is essentially complete. 

For analytical applications, when a linear relationship between fluorescence intensity and concentration is desirable, a correction curve must be built up under the same conditions as those that will be used for the actual experiment. 

Odetti P, Pronzato MA, Noberasco G, Cosso L, Traverso N, Cottalasso D and Marinari UM (1994) Relationships between glycation and oxidation related fluorescences in rat collagen during aging. Lab Invest 70, 61-67. 

Thus, it is not possible to show a direct relationship between fluorescence decrease and antitumor activity of the cyclophosphazenes studied, and the question arises as to... 

Figure 2. The relationship between fluorescence of ANS and concentration of LiFCB in 6ED-LiFCB mixed system. The fixed concentrations are ImM, 0.9mM, O.SmM, 0.6mM and 0.4mM.

In Strickler and Berg theory, it is assiuned that fluorescence occurs from the original excited state without taking into account possible solvent reorientation and subsequent formation of a new lower energy excited state. Hence, the relationships between absorption and emission spectra may be more complicated than simply following Strickler and Berg theory, and ti may differ from These results indicate the importance of considering the effect of medium on fluorescence properties for these compounds. 

A check on the consistency of the constants Kh K2, and K3 can be obtained from the measurements of the normal fluorescence quenching constant for the monomer (Table VII). By considering the stationary concentration of P for normal fluorescence, and applying the relationship between P2 and P given by eq. (43), it can be shown that... 

ANALYZER (Reagent-Tape). The key to chemical analysis by this method is a tape (paper or fabric) that has been impregnated with a chemical substance that reacts with the unknown to form a reaction product on the tape which lias some special characteristic, e.g., color, increased or decreased opacity, change in electrical conductance, or increased or lessened fluorescence. Small pieces of paper treated with lead acetate, for example, have, been used manually by chemists for many years to determine the presence of hydrogen sulfide in a solution or in the atmosphere. This basic concept forms the foundation for a number of sophisticated instruments that may pietreat a sample gas, pass it over a cyclically advanced tape, and, for example, photo-metrically sense the color of the exposed tape, to establish a relationship between color and gas concentration. Depending upon tile type uf reactiun involved, the tape may he wet or dry and it may be advanced continuously or periodically. Obviously, there are many possible variations within the framework of this general concept. 

Abnormal Stokes Shift.—The shift of an emission band to frequencies lower than those expected from the usual mirror image relationship between absorption and fluorescence bands (i.e., lack of a common 0-0 band). The phenomenon must always indicate that the emitting state is not the one produced by absorption. A number of processes may be responsible for example, the first formed excited state may undergo a chemical transformation, such as isomerization, so that emission involves a chemical species different from that which originally absorbed the light. 

The fluorescence properties of two fulvic acids, one derived from the soil and the other from river water, were studied. The maximum emission intensity occurred at 445-450 nm upon excitation at 350 nm, and the intensity varied with pH, reaching a maximum at pH 5.0 and decreasing rapidly as the pH dropped below 4. Neither oxygen nor electrolyte concentration affected the fluorescence of the fulvic acid derived from the soil. Complexes of fulvic acid with copper, lead, cobalt, nickel and manganese were examined and it was found that bound copper II ions quench fulvic acid fluorescence. Ion-selective electrode potentiometry was used to demonstrate the close relationship between fluorescence quenching and fulvic acid complexation of cupric ions. It is suggested that fluorescence and ion-selective electrode analysis may not be measuring the same complexation phenomenon in the cases of nickel and cobalt complexes with fulvic acid. 

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