Fluorescing agent

74) This was synthetic ultramarine. This strange chemical is discussed in Chapter 7. 

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Various workers have discussed the application of this technique [164,253-257], employing ninhydrin [218] and o-phthaldehyde as fluorescing agents [257]. 

Access to modified nucleosides. Base-modified nucleosides and nucleotides are very important for their biological properties. They can be found as antiviral agents (HBH, VZV, AIDS),93 95 in the study of DNA degradation,96,97 as fluorescent agents and as chemical probes of DNA structure.98 101 The access to nucleosides can be achieved by different methods ... 

Wiersma and Lee [164] determined selenium in lake sediments. The sample is digested with 4 1 concentrated nitric acid 6% perchloric acid and the residue treated with 6M hydrochloric acid then reduced with H PO. The fluorescing agent used was 2,3 diaminonaphthalene. 3 2... 

The excitation spectrum of a fluorescent material, i.e., the incident radiation spectrum required for the induction of fluorescence, is determined by the absorption spectrum of the fluorescent material, which it often closely resembles, and by the efficiency with which the absorbed energy is transformed into fluorescence. Normally, the excitation spectrum is of higher photon energy (shorter wavelength) than that of the corresponding fluorescence emission, and in sensor schemes this has an effect in the choice of preferred fluorescent agent, compatible with appropriate optical detection devices. 

A UV laser is needed for exciting the blue-fluorescing agents, 4, 6-diamidino-2-phenyhndole (DAPI) and Hoechst 33342, which are DNA-intercalating stains, and for indo-1, a fluorescent calcium chelator dye. Violet diode lasers that are offered in some newer instruments accommodate fluorochromes such as Cascade Blue, Pacific Blue, and cyan fluorescent protein, and are also capable of exciting DAPI (Shapiro and Perlmutter 2001 Telford et al., 2003). 

Both 2,8-dimethyl- and 3,7-dimethyldibenzothiophene have been reacted with a variety of aromatic aldehydes in DMF yielding distyryl compounds of type 79. Yields were best for 3,7-dimethyldibenzothiophene and in the case of its condensation with 3-p5T idinecarboxaldehyde the product was of value as a synthetic fiber fluorescent agent. ... 

The only modality which is in daily and widespread routine cHnical practice so far is the imaging of ocular diseases in ophthalmology. Fluorescein and ICG are established as fluorescent agents to enhance visuaHzation of chorioretinal diseases, such as vascular disorders, rethinopathies, neovascularization (age-related macular degeneration) or tumours [130,134,135]. 

Buffers should have low absorbance and low fluorescence in the regions of excitation and emission. Absorbance will usually be expected to be <0.1 and fluorescence close to zero. This will normally be the case for standard buffers made from analytical-grade reagents or materials of equivalent purity, but they should nevertheless be checked routinely for fluorescence. If a fluorescent component is added to the solution—e.g., as a ligand—it should be checked that the observed fluorescence arises solely from that component. The actual buffer solution used to dissolve or to dialyze the protein should be used for the fluorescence blank. Plastic containers (and stirring bars) may contribute fluorescent agents if these are used, appropriate blanks should be carefully monitored for fluorescence. 

Detection using a fluorescent agent is also applicable [4]. Infrared spectrometry using potassium bromide requires a modified technique because of the highly viscous state of branched PEI [5]. 

Figure 1.3 Thin-layer chromatography, (a) Thin-layer of adsorbent containing a binder so that it adheres to the glass plate, (b) Glass plate the plates ate made up by spreading a thidc slurry of adsorbent on the plate, followed by drying in an oven nowadays pre-ptepared plate may be bought with the adsorbent on a plastic backing, (c) In the early days of TLC, gas jars were used but nowadays customised TLC tanks are available the inside of the tank is lined with filter paper soaked in eluent in order that the atmosphere in the tank is saturated with eluent vapour, (d) Eluent the plate is "spotted at a point which will be just above the level of the eluent, (e) The TLC plate. Many means of visualisation are possible (absorption of iodine, use of fluorescent agent on the adsorbent, concentrated sulphuric acid spray etc.) here a mixture is run against a reference standard of a key component in the mixture however it is possible to run many samples simultaneously.

DNA-acoustic wave biosensors have been employed to study the duplex formation at the sensor surface and for monitoring a wide variety of processes involving nucleic acid chemistry at the soUd-liquid interface without the need of labels such as radiochemical or fluorescent agents. The theory and applications of acoustic wave technology were reviewed by Thompson [50,51], Ziegler [52] and co-workers. 

This phenomenon, as its name suggests, is a reduction in the intensity of light emitted during fluorescence. There are two types self-quenching and quenching by other, non-fluorescent agents. 

Very few ions are directly detectable by uv/vis absorption spectroscopy. However, if a postcolumn reaction is performed to chelate a cation with a chromophore (color producing group), to add a fluorescing agent, or to simply react the compound with another compound, such as using ninhydrin with amino acids, then uv/vis spectroscopy can be used. An example of such a system is the separation of lanthanides shown in the cation section. 

Reaction of 2-hydrazinopurine 293 with diethoxymethylacetate or preferentially with N,N-Aimethy 1 lbrmamide dineopentyl acetal produced [l,2,4]-triazolo[3,4-/>]purine 294. This compound is a strong UV-fluorescence agent (82H(17)405) (Scheme 85). 

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