Organic fluorophore

Physical Principles Behind Spectroscopic Response of Organic Fluorophores to Intermolecular Interactions. 189... 

Tomin VI (2010) Physical principles behind spectroscopic response of organic fluorophores to intermolecular interactions. In Demchenko AP (ed) Advanced Fluorescence Reporters in Chemistry and Biology I. Springer Ser Fluoresc 8 189-224... 

Keywords Combinatorial approach Design-based approach Organic fluorophores Photophysical property Tunability... 

Fluorescence or Forster resonance energy transfer (FRET) is widely accepted as being one of the most useful methods to observe biochemical events in vitro and in living cells. Generally, there are two forms of FRET sensors those based on a pair of genetically encoded fluorophores, usually employing fluorescent proteins from jellyfish or corals, or those based on small molecules that make use of small organic fluorophores. 

First entry on each line is the tag. Square brackets enclose the probe donor + transfer enzyme (where applicable) or reaction. Probe organic fluorophores, nanoparticles (can be QDs as in methods 2, 3, 8, 9) or a bridging/recognition moiety. If desired, the latter can serve in a second orthogonal reaction ( piggyback strategy). See text. Biotin readout probes linked to avidin, streptavidin, anti-biotin 7[101] ... 

Furthermore, silica-entrapped molecules are physically and chemically protected. For example, organic fluorophores encapsulated via a sol gel in ORMOSIF nanoparticles (20-30 nm in diameter) become 20 times brighter and more photostable than their constituent fluoro-phore due to the cage protecting the fluorophore from bleaching due to oxygen dissolved in the solvent.13... 

The only organic fluorophores approved by the Food and Drug Administration (FDA) for use in humans are fluorescein (e.g., for opthalometry), Nile Blue, and... 

Toxicity of nanoparticles is a much more complicated issue as compared with organic fluorophores Nanoparticles may be nanotoxic, they may contain cytotoxic elements or compounds, or their surface ligands/coating may contain toxic species. Nanotoxicity refers to the ability of a substance to be intrinsically cytotoxic due to its size (and independent of its constituent materials). The most prominent example of nanotoxicity is asbestos. Even though there are no systematic studies on the nanotoxicity of different nanocrystals available the results from several cytotoxicity studies suggest that nanotoxicity is not dominating for nanoparticular reporters [85, 86]. 

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)... 

Fig. 5 Photostability of fluorescent Au nanoclusters (AuNC DHLA) compared with semiconductor quantum dots (polymer-coated QD 520 from Invitrogen) and organic fluorophores (fluorescein, rhodamine 6G) [12]...

Since highly fluorescent water soluble gold clusters have been synthesized by various routes, they can be used in biology-related experiments such as imaging. These clusters may possess additional benefits over organic fluorophores and fluorescent semiconductor quantum dots. Organic fluorophores are prone to photobleaching,... 

Long r s (hundreds of nanoseconds to >100 /tsec), which make r measurements much simpler and less expensive compared to the low-nanosecond lifetimes of most organic fluorophores. 

Some of the theoretical aspects of fluorescence have already been discussed alongside phosphorescence in section 3.2 and shown schematically in Figure 3.1. In organic fluorophores, especially dyes, excitation from the ground level to the hrst excited state Sj is generally a n-n electronic transition. During the extremely short time (1-10 x 10 s) that the excited molecule spends in the various higher... 

Time-resolved RET is capable of very sensitive detection of DNA hybridization. With a lanthanide chelate as the donor and an organic fluorophore like tetramethylrhodamin as the acceptor, time-resolved measurements can indicate the hybridization by strong changes in the intensity decay of the donor [186]. The development of new dyes for time-resolved RET with improved properties still is a major task [187,188]. But, so far, the detection of biomolecular interactions by time-resolved RET has not entered real applications in the DNA or protein array market. 

---