Dyes, fluorescent

Fluorescent molecules span the entire region from the ultraviolet, through the visible, to the near infrared. Many dyes exhibit fluorescence, but to be of practical use, fluorescent dyes must satisfy certain requirements they must produce a pure color dictated by their absorption and emission spectra, they must have a high molar extinction, and most important, they must have a high quantum yield. These requirements are met by very few dyes. A disadvantage shared by many fluorescent dyes is their poor lightfastness, but there are some exceptions. 

Colourless molecules with blue fluorescence are optical brightening agents that are used as blue whiteners in paper production and washing powders (see Chapter 7). The two main classes are heterocylics such as pyrazolines and particularly stilbenes (1). 

Yellow Dyes with Blue/Green Fluorescence. Fluorescein, C.I. Solvent Yellow 94, 45350 1 [518-45-6] (2), is perhaps the best known example, but equally important are coumarins, such as C.I. Basic Yellow40 [12221-86-2], and especially naphtha-limides such as C.I. Solvent Yellow44, 56200 [2478-20-8] (3). 

Red Dyes with Yellow/Orange/Red Fluorescence. The best known dyes of this type are the rhodamines (xanthenes), such as C.I. Solvent Red 49 [509-34-2] (4). Another type are hemicyanines, e.g. C.I. Basic Red 12, 48070 [6320-14-5] (Astraphloxine). 

Blue Dyes with Red or Near-Infrared Fluorescence. These are less important than the above types and are of little importance industrially. Indeed, whilst the blue-green fluorescence of a yellow dye and the red fluorescence of a red dye increase the visual attractiveness of the dyes by making them brighter, a blue dye with red fluorescence is visually weird. 

---

The ability to image lateral heterogeneity in Langmuir monolayers dates back to Zocher and Stiebel s 1930 study with divergent light illumination [166]. More recently the focus shifted toward the use of fluorescence microscopy of mono-layers containing a small amount of fluorescent dye [167]. Even in single-corn-... 

Fluorescent dyes Fluorescent lamps Fluorescent lights Fluorescent pigments... 

Many hydrazones and azines are colored and useful as dyestuffs. Examples are 2-hydroxynaphthazine, a yellow fluorescent dye (Lumogen LT Bright Yellow), and the pyridon—azino—quinone class of red-violet dyes. Numerous hydrazine derivatives are antioxidants and stabilizers by virtue of their reducing and chelating powers. 

Liquid crystal polymers are also used in electrooptic displays. Side-chain polymers are quite suitable for this purpose, but usually involve much larger elastic and viscous constants, which slow the response of the device (33). The chiral smectic C phase is perhaps best suited for a polymer field effect device. The abiHty to attach dichroic or fluorescent dyes as a proportion of the side groups opens the door to appHcations not easily achieved with low molecular weight Hquid crystals. Polymers with smectic phases have also been used to create laser writable devices (30). The laser can address areas a few micrometers wide, changing a clear state to a strong scattering state or vice versa. Future uses of Hquid crystal polymers may include data storage devices. Polymers with nonlinear optical properties may also become important for device appHcations. 

Table 3. Donor and Acceptor Groups in Fluorescent Dye Molecules...

The effect of forming a more rigid structure in fluorescent dyes of the rhodamine series has been clearly demonstrated (18) with the remarkable dye designated Rhodamine 101 [41175A3-3] (19). This dye has its terminal nitrogen atoms each held in two rings and has a fluorescence quantum yield of virtually 100% independent of the temperature. 

A high concentration of the fluorescent dye itself in a solvent or matrix causes concentration quenching. Rhodamine dyes exhibit appreciable concentration quenching above 1.0%. Yellow dyes, on the other hand, can be carried to 5 or even 10% in a suitable matrix before an excessive dulling effect, characteristic of this type of quenching, occurs. Dimerization of some dyes, particularly those with ionic charges on the molecules, can produce nonfluorescent species. 

A nearby molecule with a conjugated system may rob the dye molecule of its electronic energy. On the other hand, a fluorescent dye can pick up electronic energy from such a substance, called a sensitizer, with increased fluorescence. 

Whereas the eadiest fluorescent-dye pigments would last only 20 days outdoors in a screen-ink film, fade resistance has been improved to such an extent that some modem daylight-fluorescent coated panels stiU have useful color after nine months or mote in Florida sunlight in a 45° exposure tack facing south. The fluorescent layer is usually coated with an acrylic film containing a uv absorber. Indoor-accelerated exposure equipment is, of course, invaluable in the development of such systems. Better dyes and resins very likely will make possible fat mote stable coatings in the future. 

MONITORING WATER CONCENTRATION IN ORGANIC SOLVENT WITH FLUORESCENT DYES IN A SOL-GEL MEMBRANE... 

In recent years, automated DNA sequencing machines capable of identifying about 10 bases per day have become commercially available. One clever innovation has been the use of fluorescent dyes of different colors to uniquely label the primer DNA introduced into the four sequencing reactions for example, red for the A reaction, blue for T, green for G, and yellow for C. Then, all four reaction mixtures can be combined and run together on one electrophoretic... 

Though pyrjdium salts have had until recently a purely academic interest, some practical applications are beginning to emerge fluorescent dyes, photosensitizers for silver halides "or color photo-... 

I Very small amounts of the four 2, 3 -dicleoxyrtbonucleoside triphosphates (ddNTPs), each of which is labeled with a fluorescent dye of a different color (A 2 ,3 -d/ fco.Yyribonucleoside triphosphate is one in which both 2 and 3 -OH groups are missing from ribose.)... 

The fluorescence color converter technique [32] can, in principle, overcome much of this power loss by replacing the white light emitter with a blue-emitting organic stack, and the absorbing filters with green and red fluorescent dyes. Thus when a green pixel is desired, the OLED underneath is turned on and the blui... 

A diagnostic method using fluorescence labeled DNA probes to detect and quantify the number complementary chromosomal sequences on a cellular resolution. A related technique that also allows assessment of gene amplifications, but without precise quantification of copy numbers is the chromogenic in situ hybridization (CISH). Here, instead of a fluorescent dye an enzyme that can generate a colored precipitate in the tissue samples is coupled to the DNA probe. 

A relatively large amount of RNA needs to be labeled with fluorescent dyes in order to obtain satisfactoiy results (20-100 pg of total RNA or 1-2 pg of mRNA). These requirements could make microarrays incompatible with the very limited RNA yields obtained from some... 

Somatostatin. Figure 1 Somatostatin-like im mu noreactivity in neurons of the periventricular hypothalamic nucleus of the rat. Coronal brain cryostat sections have been processed for im mu nohistochemistry and sequentially incubated with a primary monoclonal mouse anti human somatostatin antibody and secondary antimouse antibody conjugated with the fluorescence-dye Cy-3. Images have been taken with a Zeiss Axioplan fluorescence microscope. Scale bar, 100 pM. 

Some laundry detergents contain optical brighteners. These are fluorescent dyes that glow blue-white in ultraviolet light. The blue-white color makes yellowed fabrics appear white. 

What is the main advantage of using a fluorescent dye to trace the function of biomolecules in a living cell ... 

Fluorescent dyes allow much smaller concentrations of biomolecules to be detected than is normally possible. 

Reliable micro-scale measurement and control of the temperature are required in developing thermal micro-devices. Available measurement techniques can be largely classified into contact and non-contact groups. While the resistance thermometer, thermocouples, thermodiodes, and thermotransistors measure temperature at specific points in contact with them, infrared thermography, thermochromic liquid crystals (TLC), and temperature-sensitive fluorescent dyes cover the whole temperature field (Yoo 2006). 

Ross D, Gaitan M, Locascio LE (2001) Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. Anal Chem 73 4117-4123 Sammarco TS, Bums MA (1999) ThermocapiUary pumping of discrete drops in microfabricated analysis devices. AlChE J 45 350-366... 

Several other techniques for have evolved for biochemical assays. In chapter 2 of this book, Omann and Sklar report on a method of fluoroimmunoassay where the bound and unbound antigen are separated by the quenching of fluorescence that accompanies antibody binding. Then, in chapter 3, Holl and Webb show how they achieved a sensitive measurement of nucleic acids by the enhancement in fluorescence that accompanies the binding of fluorescent dyes to nucleic acids. Chandler et al, also used fluorescence enhancement to monitor calcium mobility in neutrophil cells. 

Regulatory agencies currently set stringent standards on the quantities of nucleic acids allowed in recombinant biological products. In the pharmaceutical industry these requirements necessitate the quantification of trace amounts of nucleic acids in the presence of large quantities of protein and other excipients. Flourescence methods offer advantages for such analyses, but also have limitations. The use of a variety of fluorescent dyes and techniques is described here, and practical examples of such use are presented. 

---