Cuvettes fluorescence

The only way to improve the efficiency is to reduce the size of the excited spot in the sample or to match the shape of the source spot to the monochromator slit. In cuvette fluorescence systems with a horizontal excitation beam, a large improvement can be made by turning the monochromator 90°, so that the slit is horizontal and matches the orientation of the excited sample volume. 

For fluorescence excitation and emission spectra, cells from 1-5 day-old cultures suspended in the culture medium or isolated chlorosomes were diluted in 10 mM, pH 8 Tris Cl so that the absorbance at 730 nm was about 0.2 in a 1 cm fluorescence cuvette. Fluorescence spectra were measured on an instrument constructed as described previously (8) using an R 928 photomultiplier as the detector. Absorption spectra were measured on the same instmment, which incorporated an integrating sphere to avoid light-scattering artifacts. 

Fig. 3 The sheath-flow cuvette fluorescence detection chamber for an array of five capillaries. The chamber is tapered. A single laser beam is used to illuminate fluorescence from the five sample streams isolated by the sheath flow fluid.

Fig. 1. Fluorescence titration. Measurement of hGBPl/mant-nucleotide equilibrium dissociation constants K. (A) hGBPl is added stepwise to 0.5 pM mant-GppNHp in the cuvette. Fluorescence is excited at 366 nm and detected at 435 nm. The curve represents the fit...

Extremely low level detection work is being performed ia analytical chemistry laboratories. Detection of rhodamine 6G at 50 yoctomole (50 x lO " mol) has been reported usiag a sheath flow cuvette for fluorescence detection foUowiag capiUary electrophoresis (9). This represeats 30 molecules of rhodamine, a highly fluoresceat molecule (see Electhoseparations, electrophoresis Spectroscopy, optical). 

Figure 9. Typical fluorescence signals obtained from a suspension of isolated rat cardiac myocytes after the application of maitotoxin (MTX). The arrow indicates the addition of MTX (10 g/mL), a detergent Emulgen 810 (1%), which frees all vesicular Ca , or EGTA (3.5 mM), a chelator that removes all free Ca in the cuvette. The intensity of Quin 2 fluorescence is expressed in arbitrary units. (Reproduced with permission from Ref. 20. Copyright 1987 Elsevier)...

Isolated chromaffin cells were maintained in suspension culture and loaded with the fluorescent calcium indicator Fura 2 as previously described (28). 2 x 10 cells/ml were added into a cuvette containing standard buffer without (dotted line) or with (full line) 2 mM calcium. At the arrow, 10" M pardaxin was added. A rise in was... 

Porphyridium species are the sources of fluorescent pink color. The main Porphyridium phycobiliproteins are B-phycoerythrin and b-phycoerythrin. Maximum absorbance of a 1% solution of B-phycoerythrin in a 1-cm cuvette is at 545 inn, and the fluorescence emission peak is at 575 inn molecular weight is 240 kda. Batch culture of Porphyridium species outdoors yields approximately 2(X) mg of colorant per liter of culture after 3 days the phycoerythrin level in the colorant is about 15%. A higher concentration of phycoerythrin, up to 30%, can be achieved under optimal algal culture conditions. 

Fluorescence spectra were recorded using an SLM 4800 spectrofluorimeter (Bioritech, Chamarande, France) fitted with a thermostat-controlled (30°C) front-surface accessory. The incidence angle of the excitation radiation was 60°. Coagulation kinetics were performed in a quartz cuvette 1 cm x 1cm. All spectra were corrected for instrumental distortions in excitation using a rhodamine cell in the reference channel. 

After this prerun, the voltage is programmed to periodically pulse a plug of analyte into the interface. This fraction is then drawn into the second capillary for further separation. In our current configuration, the separation window in the CSE dimension is roughly 200 s in duration, and roughly 200 pulses of 1 s duration are required for the contents of the CSE capillary to be transferred to the second dimension. A constant potential is applied across the second dimension capillary, typically 10,000-20,000 V. Under this constant voltage, any analyte present within the interface is driven into the second dimension capillary for separation. Detection is by laser-induced fluorescence in a postcolumn sheath-flow cuvette. 

In order to determine the effect of air on fluorescence loss, free films of polymer 1 (15 ym thick) were placed in a quartz cuvette, which was evacuated prior to excitation in the fluorescence spectrophotometer. Although the initial loss constant was not determined accurately, both constants (entry 4) were substantially smaller in vacuo relative to air. Fluorescence loss from correspondingly thick films in air is provided in entry 5. 

In these sensors, the intrinsic absorption of the analyte is measured directly. No indicator chemistry is involved. Thus, it is more a kind of remote spectroscopy, except that the instrument comes to the sample (rather than the sample to the instrument or cuvette). Numerous geometries have been designed for plain fiber chemical sensors, all kinds of spectroscopies (from IR to mid-IR and visible to the UV from Raman to light scatter, and from fluorescence and phosphorescence intensity to the respective decay times) have been exploited, and more sophisticated methods including evanescent wave spectroscopy and surface plasmon resonance have been applied. 

Procedure The fluorescence spectra of the ethanol and water solutions of the allelochemicals 10 5 -10"7 M were recorded with spectrofluorimeter Perkin -Elmer 550 in 1-cm cuvettes. The excitation wavelength was 360 nm. LSCM images were analysed as in section 9.4. 

Quantum clusters are highly photostable when compared with organic fluorophores. A study was conducted to check the photostability of clusters in comparison to organic fluorophores and semiconductor quantum dots [12]. Photostability of a gold cluster capped with dihydrolipoic acid (AuNC DHLA) was compared with polymer coated CdSe/ZnS semiconductor quantum dots and two different organic fluorophores namely fluorescein and rhodamine 6G (Fig. 5). For the study, 20 pi of fluorescent AuNC DHLA was dissolved in sodium borate buffer of pH 9. The sample was loaded into a quartz cuvette and was exposed to blue-light (480 nm)... 

E. Amler, L. Mazzanti, E. Bertoli, and A. Kotyk, Lifetime distribution of low sample concentrations A new cuvette for highly accurate and sensitive fluorescence measurements, Biochem. Int. 27, 771-776 (1992). 

---