Fluorescence monitor

The dye is excited by light suppHed through the optical fiber (see Fiber optics), and its fluorescence monitored, also via the optical fiber. Because molecular oxygen, O2, quenches the fluorescence of the dyes employed, the iatensity of the fluorescence is related to the concentration of O2 at the surface of the optical fiber. Any glucose present ia the test solution reduces the local O2 concentration because of the immobilized enzyme resulting ia an iacrease ia fluorescence iatensity. This biosensor has a detection limit for glucose of approximately 100 ]lM , response times are on the order of a miaute. 

Bosch P, Peinado C, Martin V, Catalina F, Corrales T (2006) Fluorescence monitoring of photoinitiated polymerization reactions synthesis, photochemical study and behaviour as fluorescent probes of new derivatives of 4-dimethylaminostyryldiazines. J Photochem Photobiol A Chem 180(1-2) 118-129... 

Grinvald A, Fine A, Farber IC, Hildesheim R (1983) Fluorescence monitoring of electrical responses from small neurons and their processes. Biophys J 42(2) 195-198... 

W. Muller, G. Wehnert, and T. Scheper, Fluorescence monitoring of immobilized microorganisms in cultures, Analytica Chim. Acta 213, 47-53 (1988). 

K. F. Reardon, T. Scheper, and J. E. Bailey, In situ fluorescence monitoring of immobilized Clostridium actabutylicum, Biotechnol Lett. 8, 817-822(1986). 

A discussion on steady state fluorescent monitoring necessitates a distinction between spectroscopic and photometric measurements. The former involves a grating-based spectrofluorometer where full spectrum excitation and emission multivariate spectra are acquired. In contrast a filter photometer involves optical elements (e.g., optical Alters) to isolate excitation and emission bands thereby resulting in a univariate output emission response. 

Schnerr, H., Niessen, L., and Vogel, R. F. (2001). Real time detection of the triS gene in Fusarium species by LigthCycler-PCR using SYBR Green 1 for continuous fluorescence monitoring. Int. J. Food Microbiol. 71, 53-61. 

Based on these devices, different biomass estimation experiments were performed based on the culture fluorescence monitoring and feeding strategy studies were developed as well as bioreactor characterizations via mixing time experiments. During the next years smaller fluorescence probes were developed which could be interfaced with bioreactors via standard electrode ports. These open end detector systems measured the fluorescence fight in the backward di-... 

While most appfications were performed in suspended cell cultures some authors showed that the application of NADH-dependent fluorescence monitoring is also possible in immobifized cell systems. Here the growth of Clostridium acetobutylicum and the Saccharomyces cerevisiae immobilized in different calcium alginate structures was studied. However, calibration of the culture fluorescence signal with the biomass concentration was not possible but qualitatively an increasing biomass also led to an increase in the fluorescence signals. 

In conclusion it can be stated that accurate biomass estimation based on the culture fluorescence monitoring is possible, when the NAD(P)H-pool per cell is... 

The dynamic behavior of the cell metabolism initiated by different external effects (addition of substrates or inhibiting reagents) can be followed via this instantaneous method. These effects can be used to control the overall process and optimize the bioprocess. Meyer and Beyeler [50] developed a control system for a continuous yeast cultivation process. Here the increase up to the optimal dilution rate was controlled via fluorescence monitoring. The dilution rate was only increased when no negative effect on the metabolic state of the cells was observed. During the cultivation of Candida utilis the fluorescence signal was used for the addition of substrate ethanol. The addition was started when... 

Blanco et al. 209 have studied the thermodynamic stability of another P-hairpin model sequence by use of NMR spectroscopy. This work was extended by Munoz et al. 201 by analysis of the T-jump-induced unfolding kinetics (with fluorescence monitoring) which revealed significantly longer time scales (ps) for bringing the two arms of the hairpin together than had previously been found for zipping the a-helix (180 ns). 

Fluorescence monitoring of enzymatic ATP hydrolysis by an anthrylpolyammonium ion is described in Van Arman SA, Czarnik AW (1993) Supramol Chem 1 99... 

Figure 7. The decay curves obtained from pulse radiolysis of polystyrene solution in cyclohexane (a) monomer and (b) excimer fluorescence monitored at 287 nm and 360 nm, respectively.

Fluorescence monitoring was used for depicting the concentration changes due to the mixing process [112]. 

By fluorescence monitoring of the concentration profile along the channel width in a special microfluidic chip, it could be shown that mixing times may be of the order of several tens of seconds for low molecular weight molecules and of several hundred seconds for high molecular weight molecules in aqueous solutions [161], This fits expectations from simple calculations on the rate of diffusion. Therefore, a micro mixer is required. 

Schematic of a fluorescence monitor in series with an absorbance detector in HPLC... 

Pesticides Separated on a CN-Bonded Polar Phase. Figures 3 and 4 contain the chromatograms obtained for several of the pesticides listed in Table 2. Various mobile phases were used to facilitate separation on the CN-bonded polar phase. Detection is shown in both absorbance and fluorescence modes. It would appear that fluorescence detection is more sensitive for some pesticides, while absorbance detection is more sensitive for others. However, comparisons of one manufacturer s absorbance monitor with another manufacturer s fluorescence monitor could be misleading. (I will refer to this under Instrumental Parameters.) Furthermore, the ultimate useful comparison is obtained when practical samples are chromatographed since these... 

Several Instrumental Parameters. In a dynamic flow system such as HPLC, the signal generated by the fluorescence monitor is proportional to several variables in addition to the two (pesticide concentration and solvent used as the mobile phase) already discussed. These variables include ... 

Many pesticides fluoresce sufficiently when excited at 254 nm to permit the advantageous use of the intense 253.7 nm emission from a mercury light source for excitation in a HPLC fluorescence monitor. 

A fluorescence monitor can conveniently confirm and support data obtained with an absorbance detector. However, any comparison of the relative sensitivity/selectivity of the absorbance mode vs the fluorescence mode depends on the spectrochemical nature of both the pesticide itself, and the co-extracted co-elutants found in the agricultural product extracted. A judicious selection of mobile phase is required to optimize separation of the pesticide and co-extractives on a CN-bonded polar stationary phase. 

Species Exciting Wavelength, nm Absorbing Level Excited Level Fluorescence Monitored, nm T... 

One way in which this can be accomplished is through the use of selective monitors Selective UV detection has been demonstrated by, among others, Krstulovic and Brown (2.) at the University of Rhode Island Wheals (12) utilized selective fluorescence monitoring to differentiate peaks Neither of these techniques actually improves resolution they merely simplify the chromatogram either by eliminating peaks or by changing the ratios of overlapping peaks so that they may be determined mathematically The drawback to such a procedure is that either multiple detectors must be used or multiple runs be made to obtain a complete analysis ... 

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