Rhodamine molecules

The Lissamine form of rhodamine B consists of diethyl modifications on the two nitrogens of the upper rings of the basic rhodamine molecule as well as two sulfonate groups added at the... 

Texas Red hydrazide is a derivative of Texas Red sulfonyl chloride made by reaction with hydrazine (Invitrogen). The result is a sulfonyl hydrazine group on the No. 5 carbon position of the lower-ring structure of sulforhodamine 101. The intense Texas Red fluorophore has a QY that is inherently higher than either the tetramethylrhodamine or Lissamine rhodamine B derivatives of the basic rhodamine molecule. Texas Red s luminescence is shifted maximally into the red region of the spectrum, and its emission peak only minimally overlaps with that of fluorescein. This makes derivatives of this fluorescent probe among the best choices of labels for use in double-staining techniques. 

The spectral properties of four major phycobiliproteins used as fluorescent labels can be found in Tables 9.1 and 9.2. The bilin content of these proteins ranges from a low of four prosthetic groups in C-phycocyanin to the 34 groups of B- and R-phycoerythrin. Phycoerythrin derivatives, therefore, can be used to create the most intensely fluorescent probes possible using these proteins. The fluorescent yield of the most luminescent phycobiliprotein molecule is equivalent to about 30 fluoresceins or 100 rhodamine molecules. Streptavidin-phycoerythrin conjugates, for example, have been used to detect as little as 100 biotinylated antibodies bound to receptor proteins per cell (Zola et al., 1990). 

The fluorescent properties of TRITC (mixed isomers) include an absorbance maximum at about 544 nm and an emission wavelength of 570 nm. Fluorescent quenching of the molecule is possible. Under concentrated conditions, rhodamine-to-rhodamine interactions result in self-quenching, which reduces its luminescence yield. This phenomenon can occur with TRITC-tagged molecules, as well. If derivatization of a protein is done at too high a level, the resultant quantum yield of the conjugate will be depressed from expected values. Typically, modifications of proteins involve adding no more than 8-10 rhodamine molecules per molecule of protein, with a 4-5 substitution level considered optimal. 

Texas Red sulfonyl chloride is the active halogen derivative erf sulforhodamine 101. This important derivative of the basic rhodamine molecule possesses dual aliphatic rings off the upper-ring nitrogens and sulfonate groups on the No. 3 and 5 carbon... 

The proof that single molecules could be measured by confocal illumination was given in a study where fluorescence bursts of Rhodamine molecules passing through a sharply focused laser beam were analyzed. From the burst... 

Fig. 4.6. Image of individual ss DNA fragments labeled at the 5 end with a tetramethyl Rhodamin molecule and positioned at the surface of a cover glass by biotin-streptavidin [23]...

Other experimental techniques have been used to study the very fast relaxation of dye molecules in solution. Ricard and Ducuing studied rhodamine molecules in various solvents and observed vibrational rates ranging from 1 to 4 ps for the first excited singlet state. Their experiment consisted of two pulses with a variable delay time between them the first excites molecules into the excited state manifold and the second measures the time evolution of stimulated emission for different wavelengths. Ricard found a correlation between fast internal conversion and vibrational relaxation rates. Laubereau et al. found a relaxation time of 1.3 0.3 ps for coumarin 6 in CCI4. They used an infrared pulse to prepare a well-defined vibrational mode in the ground electronic state, and monitored the population evolution with a second pulse that excited the system to the lowest singlet excited state, followed by fluorescence detection. 

Rhodamine B isothiocyanate was adsorbed onto microcrystalline cellulose by two different methods deposition from ethanolic and aqueous solutions followed by solvent evaporation (Type I) and also fnim aqueous solutions in equilibrium with the powdered solid and following a dyeing protocol (Type II). Figure 38 displays the scheme of the dyeing procedure used to bind rhodamine molecules to microcrystalline cellulose [15]. 

Figure 5 Fluorescence signal from cuvettes with constant concentration of gold nanopaiticles but altering concentration of tetramethyl-Rhodamine. Assuming that one Rhodamine molecule occupies an area of-1 nm one can calculate the surface coverage for each concentration. Below 100 % surhice coverage the fluorescence is quenched, while above the fluorescence intensity increases linearly with Rhodamine concentration.

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