Rhodamine green

Figure 24 The pH-sensitive nature of the C-quadruplex in the presence of the complanentary 17-base sequence yields a YES gate that is easily reset. F = rhodamine green fluorophore (Xex = 504 nm A,em = 534 nm) and Q = dabcyl quencher.

Figure 3.14 Results obtained by stopped flow for a mixture of bovine serum albumin (BSA) labelled with a fluorescent probe (a rhodamine derivative) with a solution of BSA (without label) and rhodamine green at 35 °C. In the mixture there is energy transfer from the rhodamine green to the labelled protein, when it is irradiated at = 530 nm. The increase in fluorescence in the labelled protein is followed using >530 nm. Results were obtained (courtesy of Magda Abreu) in the Coimbra Chemistry Centre using a Hi-Tech SF-61 apparatus.

Xanthene Dyes. This class is best represented by Rhodamine B. It has high fluorescent brilliance but poor light and heat stabihty it may be used in phenohcs. Sulfo Rhodamine is stable and is useflil in nylon-6,6. Other xanthenes used in acryhcs, polystyrene, and rigid poly(vinyl chloride) are Solvent Green 4, Acid Red 52, Basic Red 1, and Solvent Orange 63 (see Xanthene dyes). 

In this work hybrid method is suggested to determine anionic surfactants in waters. It is based on preconcentration of anionic surfactants as their ion associates with cationic dyes on the membrane filter and measurement of colour intensity by solid-phase spectrophotometry method. Effect of different basic dyes, nature and hydrophobicity of anionic surfactants, size of membrane filter pores, filtration rate on sensitivity of their determination was studied. Various cationic dyes, such as Methylene Blue, Crystal Violet, Malachite Green, Rhodamine 6G, Safranin T, Acridine Yellow were used as counter ions. The difference in reflection between the blank and the sample was significant when Crystal Violet or Rhodamine 6G or Acridine Yellow were used. 

The results of the complexation study of Cu(II), Pb(II), Zn(II), Fe(III), Hg(II), Cd(II), Sn(IV), Zr(IV), Ti(IV) with arsenazo III, sulfonazo III, SPADNS, Eriochrome T, Acid Chrome Dai k Blue, Xylenol Orange, Methyl Thymol Blue, Pyrocatechol Violet, Chrome Azurol S, Eriochrome Cyanin R, Basic Blue K, Methyl Violet, Brilliant Green, Rhodamine C and Astraphoxin in solid phase. The obtained data ai e used for the working out of a new method of metal determination. 

Figure 13.2 Fluorescence micrographs of DOPC multi-layer patterns fabricated by dip-pen nanolithography, (a) An array of 25 contiguous line features. Red color is from doped rhodamine-labeled lipid, (b) A higher magnification of the region highlighted by the white square in (a), (c) Two-component patterns containing two different dyes. Green color is from doped NBD-labeled lipid.

Rhodamine differs from malachite green in the same way as fluorescein differs from phenolphthalein. The latter is known to be non-fluorescent. 

Fluorescent dyes. Immunofluorescence using fluorescein or rhodamine has been very successfully employed for immunohistochemistry. Fluorescein, when illuminated with UV light, emits a characteristic green fluorescence while rhodamine gives an orange colour. 

Fig. 3.172. Non-aqueous capillary electrophoresis with electrochemical detection of a dye mixture containing (a) 1.7 jUg/ml malachite green, (b) 0.70 jug/ml crystal violet, (c) 4.3 /ig/ml rhodamine B, and (d) 9.1 X 10-6 M ferrocene. Experimental conditions capillary dimensions, 95 cm X 75 pm i.d. running electrolyte, acetonitrile containing 1 M HAc and 10 mM NaAc electrokinetic injection, 20 s 5 kV separation voltage 20 kV applied detection potential, 1.55 V. Reprinted with permission from F.-M. Matysik [206].

Figure 14.2. Chemical structures of some commonly used organic fluorescent probes 1, fluorescein-5-isothiocyanate (FITC) 2, tetramethylrhodamine-5-isothiocyanate (TRITC) 3, 5-carboxyrhodamine B 4, rhodamine X isothiocyanate (XRITC) 5, malachite green isothiocyanate 6, eosin-5-isothiocyanate 7, 1-pyreneisothiocyanate 8, 7-dimethylaminocoumarin-4-acetic acid 9, CY5.180Su.

FIAs can be based on steady-state intensity measurements without probe amplification, owing to the sensitivity of detection that is possible with fluorescence instrumentation, which exceeds that of spectrophotometers by two or three orders of magnitude. A sensitive fluorometer has been described for an estradiol assay(36) in which the limit of estradiol detection is 3 x KT11 M. Estradiol antibody labeled with rhodamine B is reacted with estradiol samples. Unreacted labeled antibody is removed with Sepharose-estradiol-casein beads, and the remaining fluorescence is directly proportional to the analyte concentration. The detection limit of rhodamine B on the same fluorometer is 5 x 1(T12 M. This instrument uses a 0.75 mW green helium-neon (HeNe) laser to irradiate the sample from above, at the air-liquid interface, to increase the light path and to decrease surface reflections. The sample compartment has a top-mounted photon trap, and a mirror mounted on the side of the sample compartment opposite the PMT to enhance detection. 

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